Histology specimens
Fig 143. Neurofibrils in multipolar neurons of the anterior horns of the spinal cord. Silver
impregnation. x 400. 1 – Neurofibrils, 2 – Nucleus, 3 – Process of nerve cell.
Structural features :
1.neurofibrils : The delicate interlacing threads, formed by aggregations of neurofilaments and
neurotubules, coursing through the CYTOPLASM of the body of a NEURON and extending
from one DENDRITE into another or into the AXON.
2. nucleus : The Nucleus of a neuron is an oval shaped membrane-bound structure found in the
soma or body of the neuron. It contains the nucleolus and chromosomes, necessary for the coded
production of proteins within the cell
3. process of nerve cell : Nerve processes are "finger-like" projections from the cell body that
are able to conduct and transmit signals. There are two types: Axons typically carry signals away
from the cell body. They are long nerve processes that may branch out to convey signals to
various areas. They are dendrite and axon
Function :
*Neurofibrils include neurofilaments and neurotubules, microtubules that play a role in
the transport of proteins and other substances within the cytoplasm.
A multipolar neuron is a type of neuron that possesses a single axon and many dendrites (and
dendritic branches), allowing for the integration of a great deal of information from other
neurons.
the anterior horn contains cell bodies of alpha motor neurons, which innervate skeletal muscle to
cause movement.
Fig 144. Neurofibrils in multipolar neurons of the anterior horns of the spinal cord. Azocarmine.
x 400. 1 – Processes of nerve cells, 2 – Neurofibrils. 3 – Nucleus, 4 – Nucleolus.
structural feature
1.neurofibrils : The delicate interlacing threads, formed by aggregations of neurofilaments and
neurotubules, coursing through the CYTOPLASM of the body of a NEURON and extending
from one DENDRITE into another or into the AXON.
2. nucleus : The Nucleus of a neuron is an oval shaped membrane-bound structure found in the
soma or body of the neuron. It contains the nucleolus and chromosomes, necessary for the coded
production of proteins within the cell
3. process of nerve cell : Nerve processes are "finger-like" projections from the cell body that
are able to conduct and transmit signals. There are two types: Axons typically carry signals away
from the cell body. They are long nerve processes that may branch out to convey signals to
various areas. They are dendrite and axon
4 – Nucleolus. Nucleolus is an organelle within the nucleus which is involved actively
in ribosome synthesis and in the transfer of RNA to the cytosol.
Structure. Three major components of the nucleolus are recognized: the fibrillar center (FC),
the dense fibrillar component (DFC), and the granular component (GC). Transcription of the
rDNA occurs in the FC. The DFC contains the protein fibrillarin, which is important in rRNA
processing.
Function :
*Neurofibrils include neurofilaments and neurotubules, microtubules that play a role in
the transport of proteins and other substances within the cytoplasm.
A multipolar neuron is a type of neuron that possesses a single axon and many dendrites (and
dendritic branches), allowing for the integration of a great deal of information from other
neurons.
the anterior horn contains cell bodies of alpha motor neurons, which innervate skeletal muscle to
cause movement.
Fig 145. Granules of basophilic substance in the cytoplasm of motor neurons of the cord. x 200.
1 – Granules of basophilic substance, 2 – Nucleus, 3 – Nucleolus.
Answer : structural feature
1 – Granules of basophilic substance-A Nissl body, also known as Nissl substance and Nissl
material, is a large granular body found in neurons. These granules are of rough endoplasmic
reticulum (RER) with rosettes of free ribosomes, and are the site of protein synthesis
2 – Nucleus-The Nucleus of a neuron is an oval shaped membrane-bound structure found in the
soma or body of the neuron. It contains the nucleolus and chromosomes, necessary for the coded
production of proteins within the cell. The nucleolus of the nucleus produces ribosomes. There is
only one nucleus in the motor neuron and it is the site of mRNA transcription.
3 – Nucleolus.- It is the place where the ribosomal proteins are formed. Granular Components:
Before ribosomes are formed, these components have rRNA that binds to ribosomal proteins.
Dense Fibrillar Components: It has new transcribed RNA, which connects to the ribosomal
proteins.
Function : They are responsible for the synthesis of proteins which flow along the dendrites
and the axon and replace the proteins which are broken down during cellular activity.
Fig 146. Neurofibrils in multipolar neurons of the anterior horns of the spinal cord. x 400. 1 –
Nucleus, 2 – Nucleolus, 3 – Granules of basophilic substance.
Same as above
Fig 147. Ependymal glia of the spinal cord. Nissl stain. x 200. 1– Ependymocytes, 2 – Central
canal.
Answer :
structural feature
1– EpendymocytesThese are nervous tissue cells with simple cuboidal shape, much like that of
some mucosal epithelial cells.
2 – Central canal-The central canal, also referred to as the spinal foramen or ependymal canal,
extends from the conus medullaris in the lumbar spine to the caudal angle of the fourth ventricle
and is lined by a single layer of columnar ependymal cells
Function : The central canal, also referred to as the spinal foramen or ependymal canal,
extends from the conus medullaris in the lumbar spine to the caudal angle of the fourth ventricle
and is lined by a single layer of columnar ependymal cells
5-Ependymal glia of the spinal cord
Stain – azocarmine
Research objects – 1-central canal
2- ependymocytes
Structure features –
1) Central canal - The central canal is the longitudinal CSF-filled space which runs the
entire length of the spinal cord and represents the most caudal portion of the ventricular
system. It is lined by ependymal
2) The ependyma is the thin neuroepithelial lining of the ventricular system of the brain and
the central canal of the spinal cord. The ependyma is one of the four types of neuroglia in
the central nervous system (CNS).
Function - It is involved in the production of cerebrospinal fluid (CSF), and is shown to serve
as a reservoir for neuroregeneration.
6- protoplasmic astrocytes and pyramidal cells
Stain – silver impregnation
Protoplasmic astrocytes
Structure feature - protoplasmic astrocytes occur in the gray matter of the central nervous
system. They have fewer fibrils within their cytoplasm, and cytoplasmic organelles are sparse, so
that the somata are shaped by surrounding neurons and fibres
function - Protoplasmic astrocytes posses highly branched bushy processes and are widely
distributed in the gray matter. They extend endfeet to blood vessels and enwrap them to form the
glial limiting membrane, which is the outermost wall of the blood brain barrier
pyramidal cells
structure features - Pyramidal cells have large, pyramid-shaped cell bodies that range from
20–120 µm in diameter. They are excitatory neurons that have numerous apical and basal
dendrites and a single axon that projects out of the cortex. Pyramidal cells are particularly
prominent in motor and premotor areas.
Function - They comprise about two-thirds of all neurons in the mammalian cerebral cortex,
which places them center-stage for many important cognitive processes. What do pyramidal
neurons do? Like many other types of neuron, their main job is to transform synaptic inputs into
a patterned output of action potentials.
7- Fibrillar astrocytes
Stain – silver impregnation
Structure features - fibrillary astrocytes have abundant fiber components in the processes;
however, they have low amount of cytoplasm. The state of fibrillary astrocytes indicates a
tissue reaction that leads to gliosis
Function –
8- microglia
Stain – silver impregnation
Structure function – these cells are small—the smallest of all the neuroglia. Microglia nuclei
are typically oval-shaped, and projecting out from their cell bodies are slender elongated
processes that enable the cells to move via chemotaxis (movement along a chemical gradient)
Function - Microglia are resident cells of the brain that regulate brain development,
maintenance of neuronal networks, and injury repair.
9- myelinated nerve fibre of the sciatic nerve of frog, nodal interception
Stain – osmium impregnation
Research object – 1- neurolemma
2- nodal interception
3- myelin sheath
4- axon
Structure feature
1) neurolemma, sheath of Schwann, or Schwann's sheath) is the outermost nucleated
cytoplasmic layer of Schwann cells (also called neurilemmocytes) that surrounds the
axon of the neuron. It forms the outermost layer of the nerve fiber in the peripheral
nervous system.
2) Node of Ranvier, periodic gap in the insulating sheath (myelin) on the axon of
certain neurons that serves to facilitate the rapid conduction of nerve impulses. Nodes of
Ranvier are approximately 1 μm wide and expose the neuron membrane to the
external environment. These gaps are rich in ion channels, which mediate the exchange
of certain ions, including sodium and chloride, that are required to form an action
potential—the reversal of electrical polarization of the neuron membrane that initiates or
is part of a wave of excitation that travels along the axon. The action
potential propagated by one node of Ranvier jumps to and is regenerated at the next node
along the axon, thereby enabling the action potential to travel rapidly along the fibre
3) The myelin sheath is not compacted at lateral loops and Schmidt–Lanterman clefts,
which contain Schwann cell cytoplasm
4) axon is a long, tail-like structure which joins the cell body at a specialized junction
called the axon hillock. Many axons are insulated with a fatty substance called myelin.
Myelin helps axons to conduct an electrical signal. Neurons generally have one main
axon.
Function - provide the body with a rapid and efficient transfer of information
Structural features:
1) Nodes of Ranvier are microscopic gaps found within myelinated axons, occur along a
myelinated axon where the axolemma is exposed to the extracellular space, these serves
to facilitate the rapid conduction of nerve impulses.
2) Axon: Myelin forms by the concentric wraps of the plasma membrane of neuroglia cells
around the axon. These axon are a long, tail-like structure which joins the cell body at a
specialized junction called the axon hillock. These cells are the Schwann cells (or
neurolemmocytes) in the PNS and oligodendrocytes in the CNS.
3) Myelin sheath is an insulating layer, or sheath that forms around nerves, including those
in the brain and spinal cord. It is made up of protein and fatty substances, that insulate
the axon from electrical activity
4) Basement membrane: The basal lamina is a thin layer of extracellular matrix covering
the connective tissue surface of Schwann cells, muscle fibers and epithelial cells in
general. The main structural component of basal lamina is type IV collagen,
Regenerating axons grow through basal lamina tubes derived from Schwann cells,
skeletal muscle fibers and other tissues.
Function:

The myelinated nerve fibre provide the body with a rapid and efficient transfer of
information from peripheral receptors to the central nervous system (CNS), from the
CNS to peripheral effectors, and between different centres within the CNS.



They also have protection role for many neurons
Myelin sheath acts as an insulator allowing for the protection of the integrity of nerve
impulse as well as protecting the axon from foreign electrical impulse
Myelin also yield formation of node of Ranvier
Structural features:
1) Nodes of Ranvier are microscopic gaps found within myelinated axons, occur along a
myelinated axon where the axolemma is exposed to the extracellular space, these serves
to facilitate the rapid conduction of nerve impulses.
2) Axon: Myelin forms by the concentric wraps of the plasma membrane of neuroglia cells
around the axon. These axon are a long, tail-like structure which joins the cell body at a
specialized junction called the axon hillock. These cells are the Schwann cells (or
neurolemmocytes) in the PNS and oligodendrocytes in the CNS.
3) Myelin sheath is an insulating layer, or sheath that forms around nerves, including those
in the brain and spinal cord. It is made up of protein and fatty substances, that insulate
the axon from electrical activity
4) Nucleus of neurolemmocyte is also called as Schwann cell, A well-developed Schwann
cell is shaped like a rolled-up sheet of paper, with layers of myelin between each coil.
The inner layers of the wrapping, which are predominantly membrane material, form the
myelin sheath, while the outermost layer of nucleated cytoplasm forms the neurilemma.
Function:




The myelinated nerve fibre provide the body with a rapid and efficient transfer of
information from peripheral receptors to the central nervous system (CNS), from the
CNS to peripheral effectors, and between different centres within the CNS.
They also have protection role for many neurons
Myelin sheath acts as an insulator allowing for the protection of the integrity of nerve
impulse as well as protecting the axon from foreign electrical impulse
Myelin also yield formation of node of Ranvier
Structural features:
1) Axon: Myelin forms by the concentric wraps of the plasma membrane of neuroglia cells
around the axon. These axon are a long, tail-like structure which joins the cell body at a
specialized junction called the axon hillock. These cells are the Schwann cells (or
neurolemmocytes) in the PNS and oligodendrocytes in the CNS.
2) Myelin sheath is an insulating layer, or sheath that forms around nerves, including those
in the brain and spinal cord. It is made up of protein and fatty substances, that insulate
the axon from electrical activity.
3) Notches are an incision on the edges or on surfaces of the myelin, they promotes the
growth by longitudinal axons
Function:




The myelinated nerve fibre provide the body with a rapid and efficient transfer of
information from peripheral receptors to the central nervous system (CNS), from the
CNS to peripheral effectors, and between different centres within the CNS.
They also have protection role for many neurons
Myelin sheath acts as an insulator allowing for the protection of the integrity of nerve
impulse as well as protecting the axon from foreign electrical impulse
Myelin also yield formation of node of Ranvier
Structural features:



The Pacinian corpuscle is approximately oval-cylindrical-shaped and 1 mm in length.
The entire corpuscle is wrapped by a layer of connective tissue.
The core of the Vater-Pacini corpuscle contains a single, unbranched, non-myelinated
nerve fibre, which has several club-like terminals. The innervating neuron becomes
myelinated once it leaves the Pacinian corpuscle on its way to the cerebral cortex.
The concentric lamellae are flattened neurolemmocytes (the source of the myelin sheaths)
and are separated by interstitial fluid space and delicate collagen fibers. Pressure is
translated as a mechanical stimulus through the connective tissue layers and fluid,
exciting the core receptor axon.
Function:



Pacinian corpuscles are rapidly adapting (phasic) receptors that detect gross pressure
changes and vibrations in the skin.
The corpuscle transmits mechanical stimuli, through the connective tissue lamellae and
fluid, to excite the nonmyelinated receptor axon in its core.
Pacinian corpuscles have a large receptive field on the skin's surface with an especially
sensitive centre
Structural feature :
1.The corneal epithelium is non-keratinized stratified squamous epithelium approximately 5-6
cells thick that covers the front of cornea.
2. The Bowman’s membrane or anterior lamina or anterior elastic lamina is a smooth ,
acellular , non-regenerating layer located between the superficial epithelium and the stroma in
the cornea of eye.
3.The Substantia propria is a fibrous , tough , unyeilding perfectly transparent and the thickest
layer of the cornea of the eye.Its between the Bowman’s membrane anteriorly and Descemet’s
membrane posteriorly.
4.The Descemet membrane or posterior lamina or posterior elastic lamina covers the
posterior surface of substantia propria and is elastic , transparent homogeneous membrane of
extreme thickness which is not rendered opaque by either water , alcohol or acids.
5.Posterior cuboidal epithelium acts as a barrier to protect the cornea, resisting the free flow of
fluids from the tears , and prevents bacteria from entering the epithelium and corneal stroma.
Function:
1. The cornea acts as the eye’s outermost lens ,which functions like a window that controls and
focuses the entry of light into the eye.
2.It protects the eye against infections. Cornea contributes to two-third of the refractive power of
the eye.
16)
CORNEA
Stain – hematoxilin eosin
Research object –
1) Striated squamous non-keratinized epithelium
2) Anterior limiting lamina
3) Substantia propria
Structure features
1) The corneal epithelium is a stratified (possessing five or six layers) squamous nonkeratinized epithelium (the superficial cells are flattened, nucleated and nonkeratinized). ... New cells are derived from mitotic activity in the limbal basal cell layer
2) The Bowman's membrane (Bowman's layer, anterior limiting
lamina, anterior elastic lamina) is a smooth, acellular, nonregenerating layer, located
between the superficial epithelium and the stroma in the cornea of the eye
3) The stroma of the cornea (or substantia propria) is a fibrous, tough, unyielding,
perfectly transparent and the thickest layer of the cornea of the eye. It is between
Bowman's membrane anteriorly, and Descemet's membrane posteriorly
Function
The cornea acts as the eye's outermost lens. It functions like a window that controls and focuses
the entry of light into the eye. The cornea contributes between 65- 75 percent of the eye's total
focusing power.
17)
ANTERIOIR PART OF EYEBALL
Stain – axocarmine
Research object –
1) Cornea
2) Anterior chamber of eye
3) Iris
Structure features
1) The cornea is comprised of five layers: the epithelium, Bowman's layer, the stroma,
Descemet's membrane, and the endothelium. The first layer, the epithelium, is a layer of
cells covering the cornea. It absorbs nutrients and oxygen from tears and conveys it to
the rest of the cornea. It contains free nerve endings.
2) The anterior segment is the front third of the eye that includes the structures in front of
the vitreous humour: thecornea, iris, ciliary body, and lens. Within the anterior segment
are two fluid-filled spaces: the anterior chamber between the posterior surface of the
cornea (i.e. the corneal endothelium) and the iris.
3) The iris is a flat and ring-shaped membrane behind the cornea of the eye with an
adjustable circular opening in the center called a pupil. This is the structure that provides
an individual with eye color.
Function
The anterior chamber is the front part of the eye between the cornea and the iris.
The iris controls the amount of light that enters the eye by opening and closing the pupil.
The iris uses muscles to change the size of the pupil.
18 )
IRIS
Stain – azocarmine
Research object
1) Simple squamous epithelium
2) External boundary layer
3) Vascular layer
4) Internal boundary layer
5) Posterior pigment epithelium
Structure feature
1) A simple squamous epithelium is a single layer of flat cells in contact with the basal
lamina (one of the two layers of the basement membrane) of the epithelium. This type of
epithelium is often permeable and occurs where small molecules need to pass quickly
through membranes via filtration or diffusion.
2)
3) The vascular layer of the eye lies underneath the fibrous layer. It consists of the choroid,
ciliary body and iris: Choroid - layer of connective tissue and blood vessels. It provides
nourishment to the outer layers of the retina
4)
5) Iris epithelium is a double-layered pigmented cuboidal epithelium. ... Our results
suggest that the outer layer of the optic cup forms two layers of the iris epithelium, and
the posterior IPE is the inward-curling anterior rim of the outer layer of the optic cup
Function –
the iris is responsible for regulating the amount of light that gets into the eye. Too much or
too little light can hamper vision. The muscular iris moves to shrink the pupil if there is too
much light and widen it if there is not enough.
19)
LENS ( anterio – lateral part )
Stain – hematoxylin eosin
Research object
1)
2)
3)
4)
Epithelium of lens
Fibres of lens
Nuclei of fibres of lens
Nucleus of lens
Structure features
1) The lens epithelium, located in the anterior portion of the lens between the lens capsule
and the lens fibers, is a simple cuboidal epithelium. The cells of the lens
epithelium regulate most of the homeostatic functions of the lens. ... The cells of the lens
epithelium also serve as the progenitors for new lens fibers.
2) each layer of fibers approximates a layer of an onion, but then each layer is made up of
adjacent fibers. A section through the equator of the lens shows that the fibers cut in
cross section are mostly hexagonal in shape and arranged in concentric rings
3) Moving outwards from the central, oldest layer, the lens is split into an
embryonic nucleus, the fetal nucleus, the adult nucleus, and the outer cortex. New lens
fibers, generated from the lens epithelium, are added to the outer cortex. Mature lens
fibers have no organelles or nucle
4) The lens nucleus contains proteins that are present from birth. Moreover, the outer
fibrous cells no longer make proteins after the lens has been fully shaped (Zhang et al.,
2008 and references therein)
Function –
the lens help to focus the light rays onto the back of the eye (retina). The cells in the retina
absorb and convert the light to electrochemical impulses which are transferred along the
optic nerve and then to the brain. The eye works much the same as a camera.
20 )
POSTEROR WALL OF THE EYE . RETINA IN THE DARK
Stain – hematoxylin eosin
Research object
1) Choroid
2) Pigment epithelium
3) Layer of rods and cones
4) Outer nuclear layer
5) Outer plexiform layer
6) Inner nuclear layer
7) Inner plexiform layer
8) Ganglion cell layer
9) Nerve fibre layer
10) Inner limiting membrane
Structure features
1) the lens help to focus the light rays onto the back of the eye (retina). The cells in the
retina absorb and convert the light to electrochemical impulses which are transferred
along the optic nerve and then to the brain. The eye works much the same as a camera.
2) The pigmented layer of retina or retinal pigment epithelium (RPE) is
the pigmented cell layer just outside the neurosensory retina that nourishes retinal visual
cells, and is firmly attached to the underlying choroid and overlying retinal visual cells.
3) The elements composing the Layer of Rods and Cones (Jacob's membrane) in the retina
of the eye are of two kinds, rod cells and cone cells, the former being much more
numerous than the latter except in the macula lutea.
4) The outer nuclear layer (ONL) of the retina contains the nuclei of the cone and rod
photoreceptors1. Loss of the cellular machinery found in these nuclei causes irreparable
loss of the photoreceptors and the capacity for visual function.
5) The outer plexiform layer (OPL; also outer synaptic layer) has a wide external band
composed of inner fibers of rods and cones and a narrower inner band consisting of
synapses between photoreceptor cells and cells from the inner nuclear layer.
6) The inner nuclear layer (INL) consists of the cell bodies of horizontal cells, bipolar
cells, amacrine cells, interplexiform neurons, Müller cells, and sometimes displaced
ganglion cells. ... The retinal vasculature of the deep capillary network is located in
the inner nuclear layer.
7) The inner plexiform layer is an area of the retina that is made up of a dense reticulum
of fibrils formed by interlaced dendrites of retinal ganglion cells and cells of
the inner nuclear layer. Within this reticulum a few branched spongioblasts are
sometimes embedded.
8) A retinal ganglion cell (RGC) is a type of neuron located near the inner surface
(the ganglion cell layer) of the retina of the eye. It receives visual information from
photoreceptors via two intermediate neuron types: bipolar cells and amacrine cells. ...
These axons form the optic nerve, optic chiasm, and optic tract.
9) A retinal ganglion cell (RGC) is a type of neuron located near the inner surface
(the ganglion cell layer) of the retina of the eye. It receives visual information from
photoreceptors via two intermediate neuron types: bipolar cells and amacrine cells. ...
These axons form the optic nerve, optic chiasm, and optic tract.
10) The internal limiting membrane (ILM) is the basal lamina of the inner retina that is
formed by the footplates of Müller cells. It is the structural interface between
the retina and the vitreous and is composed of collagen fibers, glycosaminoglycans,
laminin, and fibronectin.
Function
The posterior chamber is between the iris and lens. The lens is behind the iris and is
normally clear. Light passes through the pupil to the lens. The lens is held in place by small
tissue strands or fibers (zonules) extending from the inner wall of the eye.
rhodopsin regenerates and the sensitivity of the retina increases over time (this can take
approximately one hour). During these adaptation process reflexive changes occur in the
pupil size.
21)
Structural feature:
The pigmented layer of retina or retinal pigment epithelium (RPE) is the pigmented cell
layer just outside the neurosensory retina that nourishes retinal visual cells, and is firmly
attached to the underlying choroid and overlying retinal visual cells.
Function:
A layer of cells that protects and nourishes the retina, removes waste products, prevents new
blood vessel growth into the retinal layer and absorbs light not absorbed by the photoreceptor
cells; these actions prevent the scattering of the light and enhance clarity of vision
22)
Structural features;
1. The choroid is a thin, pigmented vascular network consisting of three layers (from inner to
outer): choriocapillaris, stroma, and lamina fusca. The choriocapillaris provides nutrients to the
RPE and the outer third of the retina.
2.The pigmented epithelium, which is adjacent to the choroid, absorbs light to reduce back
reflection of light onto the retina,
3. the photoreceptor layer contains photosensitive outer segments of rods and cones. Rods and
cones: rods are cylindrical, cones are longer and thicker; light is converted by photoreceptor cells
into electric impulses.
It form the outer nuclear layer
Synapse with bipolar cells at the outer plexiform layer
Rods deal predominantly with peripheral and night vision
Cones deal mainly with central vision
4.The outer nuclear layer contains the cell bodies of the photoreceptor cells. These cells extend a
process toward the outer plexiform layer, where they form the characteristic synaptic terminals
of rods (spherules) and cones (pedicles). the outer nuclear layer contains cell bodies of the rods
and cones,
5. the outer plexiform layer contains synapses between axons of photoreceptors and dendrites of
intermediate neurons,
6. The inner nuclear layer (INL) consists of the cell bodies of horizontal cells, bipolar cells,
amacrine cells, interplexiform neurons, Müller cells, and sometimes displaced ganglion cells.
The retinal vasculature of the deep capillary network is located in the inner nuclear layer. the
inner nuclear layer contains cell bodies of intermediate neurons and Muller cells,
7.The inner plexiform layer (IPL; also inner synaptic layer) consists of synaptic connections
between the axons of bipolar cells and dendrites of ganglion cells. The IPL contains the synapse
between the second-order and third-order neuron in the visual pathway, the inner plexiform layer
contains synapses between intermediate neurons and ganglion cells of the optic tract,
8. The ganglion cell layer is generally a single cell thick except near the macula, where it might
be 8 to 10 cells thick, and at the temporal side of the optic disc, where it is 2 cells thick.
Although lying side by side, ganglion cells are separated from each other by glial processes of
Müller cells. the ganglion cell layer contains cell bodies of ganglion cells,
9. The nerve fiber layer consists of the axons of the ganglion neurons coursing on the vitreal
surface of the retina to the optic disk. These axons are unmyelinated until they penetrate the
sclera at the optic disk. Their myelination by oligodendrocytes at this point accounts for the
white color of the optic disk.
Function:
The purpose of the retina is to receive light that the lens has focused, convert the light into
neural signals, and send these signals on to the brain for visual recognition.
23)
Structural feature: The pigmented layer of retina or retinal pigment epithelium (RPE) is
the pigmented cell layer just outside the neurosensory retina that nourishes retinal visual
cells, and is firmly attached to the underlying choroid and overlying retinal visual cells.
Functions:
A layer of cells that protects and nourishes the retina, removes waste products, prevents new
blood vessel growth into the retinal layer and absorbs light not absorbed by the photoreceptor
cells; these actions prevent the scattering of the light and enhance clarity of vision
24)
Structural features;
1. The choroid is a thin, pigmented vascular network consisting of three layers (from inner to
outer): choriocapillaris, stroma, and lamina fusca. The choriocapillaris provides nutrients to the
RPE and the outer third of the retina.
2.The pigmented epithelium, which is adjacent to the choroid, absorbs light to reduce back
reflection of light onto the retina,
3. the photoreceptor layer contains photosensitive outer segments of rods and cones. Rods and
cones: rods are cylindrical, cones are longer and thicker; light is converted by photoreceptor cells
into electric impulses.
It form the outer nuclear layer
Synapse with bipolar cells at the outer plexiform layer
Rods deal predominantly with peripheral and night vision
Cones deal mainly with central vision
4.The outer nuclear layer contains the cell bodies of the photoreceptor cells. These cells extend a
process toward the outer plexiform layer, where they form the characteristic synaptic terminals
of rods (spherules) and cones (pedicles). the outer nuclear layer contains cell bodies of the rods
and cones,
5. the outer plexiform layer contains synapses between axons of photoreceptors and dendrites of
intermediate neurons,
6. The inner nuclear layer (INL) consists of the cell bodies of horizontal cells, bipolar cells,
amacrine cells, interplexiform neurons, Müller cells, and sometimes displaced ganglion cells.
The retinal vasculature of the deep capillary network is located in the inner nuclear layer. the
inner nuclear layer contains cell bodies of intermediate neurons and Muller cells,
7.The inner plexiform layer (IPL; also inner synaptic layer) consists of synaptic connections
between the axons of bipolar cells and dendrites of ganglion cells. The IPL contains the synapse
between the second-order and third-order neuron in the visual pathway, the inner plexiform layer
contains synapses between intermediate neurons and ganglion cells of the optic tract,
8. The ganglion cell layer is generally a single cell thick except near the macula, where it might
be 8 to 10 cells thick, and at the temporal side of the optic disc, where it is 2 cells thick.
Although lying side by side, ganglion cells are separated from each other by glial processes of
Müller cells. the ganglion cell layer contains cell bodies of ganglion cells,
9. The nerve fiber layer consists of the axons of the ganglion neurons coursing on the vitreal
surface of the retina to the optic disk. These axons are unmyelinated until they penetrate the
sclera at the optic disk. Their myelination by oligodendrocytes at this point accounts for the
white color of the optic disk.
10. The internal limiting membrane (ILM) is the basal lamina of the inner retina that is formed
by the footplates of Müller cells. It is the structural interface between the retina and the vitreous
and is composed of collagen fibers, glycosaminoglycans, laminin, and fibronectin.
the optic nerve fiber layer contains axons of ganglion cells. Membrane layers that are not visible
in this image separate the photoreceptors from their cell bodies and retina from the vitreal body.
Function: The purpose of the retina is to receive light that the lens has focused, convert the
light into neural signals, and send these signals on to the brain for visual recognition.
25)
STRUCTURAL FEATURES
The retina consists of a three-cell pathway: photoreceptors (rods and cones), bipolar cells and
ganglion cells. Neural integration between these layers occurs in two synaptic regions, the outer
plexiform layer and the inner plexiform layer. The vitreous chamber is visible in the upper left,
the choroid is visible in the lower right.
FUNCTION
The retina accept light focused by the cornea and lens and convert it into chemical and nervous
signals which are sent to the visual center of our brain through the optic nerve
Horizontal cells connect to the photoreceptors that surround the bipolar connected photoreceptor
cells and help the help integrate and regulate the input from multiple photoreceptor cells,
increasing your visual acuity.
26)
STRUCTURAL FEATURES
Organization of the olfactory region of the nasal cavity is similar to that of the non-olfactory
region, important differences distinguish the two regions. In the olfactory region, the
pseudostratified epithelium is much thicker and possesses bipolar neuronal cell bodies in
addition to epithelial cells. Also, serous glands replace the mixed glands in the lamina propria
FUNCTION
The bowman’s glands deliver a proteinaceous secretion via ducts onto the surface of the mucosa.
The role of the secretions is to trap and dissolve odour substances for the bipolar neurons.
Constant flow from the olfactory glands allows old odours to be constantly washed away.
27)
STRUCTURAL FEATURES
This is a medium power view of the olfactory epithelium that contains a meshwork of
sustentacular microvilli and olfactory cilia on the surface. The epithelium is pseudostratified
columnar and it is hard to differentiate between the olfactory receptor cells, sustentacular cells
and basal epithelial cells. However, the nuclei of the sustentacular cells tend to be in the top
portion of the layer, the nuclei of the olfactory receptor cells tend to be in the middle portion, and
the nuclei of the basal epithelial cells tend to be in the bottom portion. One can also see the
afferent nerve bundle.
FUNCTIONS
Perception of smell
The absorption of odour by olfactory mucous into receptors transmission of neural signal to
olfactory bulb in brain
28)
STRUCTURAL FEATURES
Cochlea is located in the petrous portion of the temporal bone. The inner ear contains two fluidfilled canals that spiral makes 2.75 turns around a central bony axis known as the modiolus. The
scala vestibuli and scala tympani contain perilymph whereas the scala media contains
endolymph. The scala vestibuli and scala media are separated by the vestibular membrane, and
the scala media and scala tympani are separated by the basilar membrane. The organ of Corti is
located on the basilar membrane and contains the hair cells that can be observed more closely in
subsequent slides. The bony portion of the cochlea also contains the spiral ganglion, which
contains cell bodies of cranial nerve VIII.
FUNCTIONS
The cochlea receives sound in the form of vibrations, which cause the stereocilia to move.
The stereocilia then convert these vibrations into nerve impulses which are taken up to the brain
to be interpreted.
29)
STRUCTURAL FEATURES
The organ of Corti itself is located on the basilar membrane. The organ of Corti rests on the
basilar membrane and contains two types of hair cells: inner hair cells and outer hair cells. The
fibrous tectorial membrane rests on top of the stereocilia or the outer hair cells.The vestibular
membrane (also called Reissner’s membrane) is the tissue separating the cochlear duct from the
scala tympani .The stria vascularis is a stratified epithelium along the outer wall of the cochlear
duct that is unique
FUNCTIONS
The organ of Corti is a specialized sensory epithelium that allows for the transduction of sound
vibrations into neural signals
Inner hair cells transduce sound from vibrations to neural signals via the shearing action of their
stereocilia
Outer hair cells serve a function as acoustic pre-amplifiers which improve frequency selectivity
by allowing the organ of Corti to become attuned to specific frequencies, like those of speech or
music.
30)
STRUCTURAL FEATURES
The organ of Corti itself is located on the basilar membrane. The organ of Corti rests on the
basilar membrane and contains two types of hair cells: inner hair cells and outer hair cells. The
fibrous tectorial membrane rests on top of the stereocilia or the outer hair cells.The vestibular
membrane (also called Reissner’s membrane) is the tissue separating the cochlear duct from the
scala tympani .The stria vascularis is a stratified epithelium along the outer wall of the cochlear
duct that is unique
FUNCTIONS
The organ of Corti is a specialized sensory epithelium that allows for the transduction of sound
vibrations into neural signals
Inner hair cells transduce sound from vibrations to neural signals via the shearing action of their
stereocilia
Outer hair cells serve a function as acoustic pre-amplifiers which improve frequency selectivity
by allowing the organ of Corti to become attuned to specific frequencies, like those of speech or
music.
31)
31)
VASCULAR STRIA OF THE TYMPANIC DUCT OF COCHLEA
Stain – azocarmine
Research object –
1)
2)
3)
4)
Outer bony wall of chochlea
Spiral ligament
Vascular stria
Blood vessels
Structure feature
1) The base of the triangular cochlear duct, when viewed in transverse section, is attached to
the outer wall of the bony cochlea and consists of a stria vascularis and a spiral
prominence, This membrane is between the perilymph of the scala vestibuli and the
endolymph of the cochlear duct
2) The spiral ligament extends above the attachment of the Reissner membrane and is in
contact with the perilymph in the scala vestibuli. Extending below the insertion of the
basilar membrane, it is in contact with the perilymph of the scala tympani. It contains
many stout fibres that anchor the basilar membrane and numerous connective-tissue cells.
The structure of the spiral ligament is denser behind the stria than near the upper and
lower margins. The spiral ligament, like the adjacent stria, is well supplied with blood
vessels. It receives the radiating arterioles that pass outward from the modiolus in bony
channels of the roof of the scala vestibule.
3) The upper portion of the spiral ligament (which forms the outer wall of the cochlear duct)
contains numerous capillary loops and small blood vessels, and is termed
the stria vascularis. It produces endolymph for the scala media, one of the three fluidfilled compartments of the cochlea.
4) cochlear duct) contains numerous capillary loops and small blood vessels, and is termed
the stria vascularis. It produces endolymph for the scala media, one of the three fluidfilled compartments of the cochlea.
Function –
It has a vital role in generating the high resting potential. the endocochlear potential. in the
endolymph filling the scala media. It also contributes to the unusual high-potassium, lowsodium content of the endolymph.
32)
AXIAL SECTION OF COCHLEA
Stain – hematoxylin eosin
Research objects –
1)
2)
3)
4)
5)
6)
7)
8)
Scala vestibuli
Tympanic duct
Scala tympani
Basilar membrane
Spiral organ
Vascular stria
Spiral ligament
Spiral ganglion
Structure features
1) scala vestibuli is a perilymph-filled cavity inside the cochlea of the inner ear that
conducts sound vibrations to the cochlear duct. It is separated from the cochlear duct by
Reissner's membrane and extends from the vestibule of the ear to the helicotrema where
it joins the tympanic duct.
2) It is one of the perilymph-filled cavities in the inner ear of the human. It is separated
from the cochlear duct by the basilar membrane, and it extends from the round window
to the helicotrema, where it continues as vestibular duct
3) it is also known as the scala tympan, it is one of the perilymph-filled cavities in the
inner ear of the human. It is separated from the cochlear duct by the basilar membrane,
and it extends from the round window to the helicotrema, where it continues
as vestibular duct
4) the basilar membrane, forms the base of the cochlear duct, is an arrangement of sensory
cells and supporting cells known as the organ of Corti
5) The spiral organ of Corti (organon spirale [Corti]; organ of Corti) is composed of a
series of epithelial structures placed upon the inner part of the basal lamina. The more
central of these structures are two rows of rod-like bodies, the inner and outer rods or
pillars of Corti.
6) The upper portion of the spiral ligament (which forms the outer wall of
the cochlear duct) contains numerous capillary loops and small blood vessels, and is
termed the stria vascularis. It produces endolymph for the scala media, one of the three
fluid-filled compartments of the cochlea
7) A spiral thickening of the fibrous lining of the cochlear wall. Spiral ligament secures
the membranous COCHLEAR DUCT to the bony spiral canal of the COCHLEA.
Its spiral ligament fibrocytes function in conjunction with the STRIA VASCULARIS to
mediate cochlear ion homeostasis.
8) Spiral ganglion neurons. The cochlear spiral ganglion (SG) is formed by two
populations of neurons, Type‐I (AF‐I, bipolar, and myelinated), and Type‐II (AF‐II,
pseudounipolar, and unmyelinated) neurons which fibers innervate the organ of Corti
(OC) inner and outer hair cells (IHCs and OHCs), respectively
Function
The cochlea is a hollow, spiral-shaped bone found in the inner ear that plays a key role in
the sense of hearing and participates in the process of auditory transduction. Sound waves are
transduced into electrical impulses that can be interpreted by the brain as individual
frequencies of sound.
33)
TRANSVERSE SECTION OF THE HELIX OF THE COCHLEA
Stain – hematoxylin – eosin
Research object
1)
2)
3)
4)
5)
6)
7)
8)
9)
10)
Outer bony wall of cochlea
Vascular stria
Spiral ligament
Scala vestibuli
Vestibular membrane
Tympanic duct
Spiral organ
Basilar membrane
Scala tympani
Spiral ganglion
Structure features
1)
The base of the triangular cochlear duct, when viewed in transverse section, is attached
to the outer wall of the bony cochlea and consists of a stria vascularis and a spiral
prominence
2) The upper portion of the spiral ligament (which forms the outer wall of
the cochlear duct) contains numerous capillary loops and small blood vessels, and is
termed the stria vascularis. It produces endolymph for the scala media, one of the three
fluid-filled compartments of the cochlea
3) A spiral thickening of the fibrous lining of the cochlear wall. Spiral ligament secures
the membranous COCHLEAR DUCT to the bony spiral canal of the COCHLEA.
Its spiral ligament fibrocytes function in conjunction with the STRIA VASCULARIS to
mediate cochlear ion homeostasis.
4) scala vestibuli is a perilymph-filled cavity inside the cochlea of the inner ear that
conducts sound vibrations to the cochlear duct. It is separated from the cochlear duct by
Reissner's membrane and extends from the vestibule of the ear to the helicotrema where
it joins the tympanic duct.
5) the membrane is composed of two layers of flattened epithelium, separated by a basal
lamina. Its structure suggests that its function is transport of fluid and electrolytes.
6) It is one of the perilymph-filled cavities in the inner ear of the human. It is separated
from the cochlear duct by the basilar membrane, and it extends from the round window
to the helicotrema, where it continues as vestibular duct
7) The spiral organ of Corti (organon spirale [Corti]; organ of Corti) is composed of a
series of epithelial structures placed upon the inner part of the basal lamina. The more
central of these structures are two rows of rod-like bodies, the inner and outer rods or
pillars of Corti.
8) the basilar membrane, forms the base of the cochlear duct, is an arrangement of sensory
cells and supporting cells known as the organ of Corti
9) it is also known as the scala tympan, it is one of the perilymph-filled cavities in the
inner ear of the human. It is separated from the cochlear duct by the basilar membrane,
and it extends from the round window to the helicotrema, where it continues
as vestibular duct
10) Spiral ganglion neurons. The cochlear spiral ganglion (SG) is formed by two
populations of neurons, Type‐I (AF‐I, bipolar, and myelinated), and Type‐II (AF‐II,
pseudounipolar, and unmyelinated) neurons which fibers innervate the organ of Corti
(OC) inner and outer hair cells (IHCs and OHCs), respectively
Function
The cochlea is a portion of the inner ear that looks like a snail shell (cochlea is Greek for
snail.) The cochlea receives sound in the form of vibrations, which cause the stereocilia to
move. The stereocilia then convert these vibrations into nerve impulses which are taken up to
the brain to be interpreted.
34)
SPIRAL ORGAN ( ORGAN OF CORTI )
Stain – hematoxylin – eosin
Research object
1)
2)
3)
4)
5)
6)
7)
8)
9)
Spiral limbus
Vestibular membrane
Tectorial membrane
Inner tunnel (corti’s tunnel)
Scala tympani
Basilar membrane
Outer hair cells
Tympanic duct
Scala vestibuli
Structure features
1) The spiral limbus is formed by a thickening of the soft tissue overlying the
osseous spiral lamina. It is easy to identify the cochlear chambers if you remember that
2)
3)
4)
5)
6)
7)
8)
9)
the vestibular membrane (the thinnest wall of the cochlear duct) separates the scala
vestibulifrom the scala media
the membrane is composed of two layers of flattened epithelium, separated by a basal
lamina. Its structure suggests that its function is transport of fluid and electrolytes.
The tectorial membrane (TM) of the inner ear is a ribbon-like strip of extracellular
matrix that spirals along the entire length of the cochlea.
Corti is the arch, or tunnel, of Corti, formed by two rows of pillar cells, or rods. The
pillar cells furnish the major support of this structure. They separate a single row of
larger, pear-shaped inner hair cells from three or more rows of smaller, cylindrical outer
hair cells
The scala tympani are filled with perilymph, communicate with each other through an
opening at the apex of the cochlea, called the helicotrema, which can be seen if the
cochlea is sliced longitudinally down the middle.
basilar membrane is the entire blue/grey structure. the basilar membrane is found in
the cochlea; it forms the base of the organ of Corti, which contains sensory receptors for
hearing. Movement of the basilar membrane in response to sound waves causes the
depolarization of hair cells in the organ of Corti.
OHCs have a regular cylindric and elongated shape. At the synaptic pole, two types of
connections are seen: an efferent synapse between a medial efferent terminal (red) and
the OHC, and an afferent synapse between the OHC and spiral afferent (green)
tympanic duct or scala tympani is one of the perilymph-filled cavities in the inner ear of
the human. It is separated from the cochlear duct by the basilar membrane, and it
extends from the round window to the helicotrema, where it continues as vestibular
duct.
The vestibular duct or scala vestibuli is a perilymph-filled cavity inside the cochlea of
the inner ear that conducts sound vibrations to the cochlear duct. It is separated from the
cochlear duct by Reissner's membrane and extends from the vestibule of the ear to the
helicotrema where it joins the tympanic duct.
Function –
The true organ of hearing, a spiral structure within the cochlea containing hair cells that are
stimulated by sound vibrations.
35)
SPIRAL ORGAN (ORGAN OF CORTI )
Stain – hematoxylin eosin
Research object
1)
2)
3)
4)
5)
6)
7)
8)
9)
Spiral limbus
Incisures of limbus
Tectorial membrane
Inner hair cells
Inner tunnel
Outer hair cells
Column cells
Outer phalangeal cells
Basilar membrane
Structure features
1) The spiral limbus is formed by a thickening of the soft tissue overlying the
osseous spiral lamina. It is easy to identify the cochlear chambers if you remember that
the vestibular membrane (the thinnest wall of the cochlear duct) separates the scala
vestibulifrom the scala media
2)
3) The tectorial membrane (TM) of the inner ear is a ribbon-like strip of extracellular
matrix that spirals along the entire length of the cochlea.
4) inner hair cell is surrounded by processes of an inner border cell on the medial side and
an inner phalangeal cell on the lateral (abneural) side. These processes form a
calyx structure around both the inner hair cell body and its afferent nerve fiber,
isolating it from the basilar membrane
5) Corti is the arch, or tunnel, of Corti, formed by two rows of pillar cells, or rods. The
pillar cells furnish the major support of this structure. They separate a single row of
larger, pear-shaped inner hair cells from three or more rows of smaller, cylindrical outer
hair cells.
6) OHCs have a regular cylindric and elongated shape. At the synaptic pole, two types of
connections are seen: an efferent synapse between a medial efferent terminal (red) and
the OHC, and an afferent synapse between the OHC and spiral afferent (green).
7)
8) They are the supporting cells they hold the base of the hair
9) basilar membrane is the entire blue/grey structure. the basilar membrane is found in
the cochlea; it forms the base of the organ of Corti, which contains sensory receptors for
hearing. Movement of the basilar membrane in response to sound waves causes the
depolarization of hair cells in the organ of Corti.
Function - The true organ of hearing, a spiral structure within the cochlea containing hair
cells that are stimulated by sound vibrations.
36)
1)The spiral limbus is formed by a thickening of the soft tissue overlying the osseous spiral
lamina. It is easy to identify the cochlear chambers if you remember that the vestibular
membrane (the thinnest wall of the cochlear duct) separates the scala vestibulifrom the scala
media
2)The tectorial membrane (TM) of the inner ear is a ribbon-like strip of extracellular
matrix that spirals along the entire length of the cochlea.
3) inner hair cell is surrounded by processes of an inner border cell on the medial side
and an inner phalangeal cell on the lateral (abneural) side. These processes form a
calyx structure around both the inner hair cell body and its afferent nerve fiber,
isolating it from the basilar membrane
4)Corti is the arch, or tunnel, of Corti, formed by two rows of pillar cells, or rods. The pillar
cells furnish the major support of this structure. They separate a single row of larger, pearshaped inner hair cells from three or more rows of smaller, cylindrical outer hair cells.
5)OHCs have a regular cylindric and elongated shape. At the synaptic pole, two types of
connections are seen: an efferent synapse between a medial efferent terminal (red) and
the OHC, and an afferent synapse between the OHC and spiral afferent (green).
7) They are the supporting cells they hold the base of the hair
9)basilar membrane is the entire blue/grey structure. the basilar membrane is found in
the cochlea; it forms the base of the organ of Corti, which contains sensory receptors for
hearing. Movement of the basilar membrane in response to sound waves causes the
depolarization of hair cells in the organ of Corti.
Function - The true organ of hearing, a spiral structure within the cochlea containing hair
cells that are stimulated by sound vibrations.
37)
stracture- The spinal cord is a long cylinder of nerves that runs from the base of your brain
through the vertebral canal through the backbone. It is part of the central nervous system (CNS)
along with the brain. It is divided into different segments. Each segment contains a pair roots
made out of nerve fibres.
Function- The brain and spinal cord are your body's central nervous system. The brain is the
command center for your body, and the spinal cord is the pathway for messages sent by the brain
to the body and from the body to the brain.
38)
Structure:
Foliate papillae in humans were first reported by Albinus .They are located bilaterally along the
posterolateral margins of the tongue surface, and consist of parallel rows of ridges (folia) and
valleys, which lie adjacent to the lower molar teeth (Hönigschmied, 1873). They are fine, small,
cone-shaped papillae covering most of the dorsum of the tongue. They are responsible for
giving the tongue its texture and are responsible for the sensation of touch. Unlike the other
kinds of papillae, filiform papillae do not contain taste buds.
Function- The foliate papillae are involved in the sensations of taste and have taste buds
39)
StractureMyelin is an insulating layer, or sheath that forms around nerves, including those in the brain and
spinal cord. It is made up of protein and fatty substances. This myelin sheath allows electrical
impulses to transmit quickly and efficiently along the nerve cells. If myelin is damaged, these
impulses slow down.
Function1) It acts as an electrical insulator for the neurone - it prevents electrical impulses travelling
through the sheath. 2) The sheath prevents the movement of ions into or out of the neurone/ it
prevents depolarisation
40)
StractureThe myelinated nerve fiber is one of the most beautiful examples of how structure and function
go hand-in-hand in biology. The axon, a slender living process from a single neuron, possesses
the molecular apparatus for generating and propagating nerve impulses, one of the important
information units that the nervous system uses to promote our survival.
Myelin sheath wraps the axon in segments. ... Interruptions, which occur in the myelin sheath at
regular intervals along the length of axons and expose the axon, are called nodes of Ranvier.
Each node indicates an interface between the myelin sheaths of two different Schwann cells
located along the axon.
functionThe myelinated nerve fiber is designed by evolution to provide the body with a rapid and
efficient transfer of information from peripheral receptors to the central nervous system (CNS),
from the CNS to peripheral effectors, and between different centers within the CNS.
41.
Structural Features:








Nerve tract is filled with ring shape.
The Axon is surrounded by multimellar structure of Myelin.
They together form the Bundles or Fasciculi.
Each nerve fibre with its Schwann Cell and Basal Lamina Is surrounded by a layer of
Connective Tissue called Endoneurium.
The endoneurium contains fibroblasts, endothelial cells, macrophages. It holds adjoining
nerve fibres together and facilitates aggregation to form fasciculi.
Each fasciculi is surrounded by a thick layer of connective tissue called Perineurium.
Blood vessels are present which are associated with Connective tissue in the fascicles.
It is made up of flattened cells separated by Collagen fibres.
Blood vessels are supported by Endoneurium forming network of elongated meshes.
Functions:

Increases speed at which electrical impulses propogate along the myelinated nerve fibers.
It decreases capacitance and increases Electrical Resistance across the membrane of the
Axon.

They prevent the loss of Impulses.
42.
Structural Features:





Group of Sensory Neurons (Pseudo-unipolar) is located on each Dorsal root of the
Ganglion.
Lipids of Myelin Sheaths ectracts during the staining which appears foamy.
The neurons of Sensory Ganglia are observed large in size arranged in groups at the
periphery.
The cell body is surrounded by a layer of flattened cells called as Capsular or satellite
Cells.
The Satellite cells are covered by the layer of Connective Tissue which is continuous
with Endoneurium.
Large Pseudounipolar neurons are arranged in groups which are separated by bundles
of nerve fibers.
Functions:


They are responsible in the transmission of sensory message from receptors such as
Thermoreceptors or Nocireceptors to the CNS for response.
These act as the connection between the Peripheral and the Central Nervous System.
These nerve clusters help transmit messages towards the brain.
43.
Structural Features:



Spinal Ganglion is a cluster of neiurons in the posterior root of the Spinal Nerve.
The neurons of Sensory Ganglia are observed large in size arranged in groups at the
periphery.
The cell body is surrounded by a layer of flattened cells called as Capsular or satellite
Cells.
The Satellite cells are covered by the layer of Connective Tissue which is continuous
with Endoneurium.


Large Pseudounipolar neurons are arranged in groups which are separated by bundles
of nerve fibers.
Each neuron has a vesicular nucleolous.
Functions:


They are responsible in the transmission of sensory message from receptors such as
Thermoreceptors or Nocireceptors to the CNS for response.
These act as the connection between the Peripheral and the Central Nervous System.
These nerve clusters help transmit messages towards the brain.
44.
Structural Features:-








The ganglion is covered by the capsule of Connective tissue from outside.
The neurons of Sensory Ganglia are observed large in size arranged in groups at the
periphery.
The cell body is surrounded by a layer of flattened cells called as Capsular or satellite
Cells.
The Satellite cells are covered by the layer of Connective Tissue which is continuou s
with Endoneurium.
Large Pseudounipolar neurons are arranged in groups that are separated by bundles of
nerve fibers.
Each neuron has a vesicular nucleus with a prominent nucleolus.
The neuron is surrounded by a ring of satellite cells.
The entire ganglion is pervaded by fine connective tissue.
Functions:


They are responsible in the transmission of sensory message from receptors such as
Thermoreceptors or Nocireceptors to the CNS for response.
These act as the connection between the Peripheral and the Central Nervous System.
These nerve clusters help transmit messages towards the brain.
45)
Structural Features:-





Autonomic Ganglia consists of neurons which are not arranged in groups, but are
scattered amongst nerve fibers.
The neurons here are smaller in size.
Nerve fibers are Non myelinated and thinner.
Satellite cells are not well defined.
Schwann cells nuclei associates with the nerve fibers entering or leaving the ganglion.
Functions:


These are motor in function supplying smooth muscles, Heart muscles and glands.
They transmit sensory signals from periphery to the integration centers in the CNS.
They send their Axons to visceral and vascular targets.
46)
Specimen name:-cererellum
Stain:-silver impregnation
Research objects:1. Molecular layer
2. Ganglionic layer
3. Granular layer
4. Purkije cells
5. White matter
Structural features:- Layer I is the molecular layer, and contains few scattered neurons,
including GABAergic rosehip neurons.[21] Layer I consists largely of extensions of
apical dendritic tufts of pyramidal neurons and horizontally oriented axons, as well
as glial cells.[22] During development, Cajal-Retzius cells[23] and subpial granular layer
cells[24] are present in this layer. Also, some spiny stellate cells can be found here
Functions:- . Inputs to the apical tufts are thought to be crucial for
the feedback interactions in the cerebral cortex involved in associative learning and
attention.[25] While it was once thought that the input to layer I came from the cortex
itself,[26] it is now realized that layer I across the cerebral cortex mantle receives
substantial input from matrix or M-type thalamus cells
Structural features:- Inner granular layer (lamina granularis interna) - contains small,
irregularily shaped nerve cells. V. Ganglionic or inner pyramidal layer (lamina
pyramidalis interna) - includes large pyramidal cells.
Functions:- The cerebral cortex is connected to various subcortical structures such as
the thalamus and the basal ganglia, sending information to them along efferent
connections and receiving information from them via afferent connections. Most sensory
information is routed to the cerebral cortex via the thalamus.
Structural features:- The cerebral cortex consists of neurons, nerve fibers and
neuroglia. ... Molecular layer (lamina molecularis) - consists only a few nerve cells. II.
External granular layer (lamina granularis externa) – relatively thin layer consisting of
numerous small, densely packed neurons.
The internal granular layer, layer IV, receives thalamocortical connections, especially
from the specific thalamic nuclei. This is most prominent in the primary sensory cortices.
The infragranular layers, layers V and VI, primarily connect the cerebral cortex with
subcortical regions.
Structural features:- Purkinje cells, also called Purkinje neurons, are neurons in
vertebrate animals located in the cerebellar cortex of the brain. Purkinje cell bodies are
shaped like a flask and have many threadlike extensions called dendrites, which receive
impulses from other neurons called granule cells
Functions:- Most Purkinje cells release a neurotransmitter called GABA (gammaaminobutyric acid), which exerts inhibitory actions on certain neurons and thereby
reduces the transmission of nerve impulses. These inhibitory functions enable Purkinje
cells to regulate and coordinate motor movements
structural features:- White matter is tissue in the brain composed of nerve fibers.
The fibers (called axons) connect nerve cells and are covered by myelin (a type of
fat). The myelin is what gives white matter its white color.
function:- Long thought to be passive tissue, white matter affects learning and brain
functions, modulating the distribution of action potentials, acting as a relay and
coordinating communication between different brain regions. White matter is named
for its relatively light appearance resulting from the lipid content of myelin.
47).Specimen name:-cererellum
Stain:-silver impregnation
Research objects:-
1.
2.
3.
4.
5.
Molecular layer
Ganglionic layer
Granular layer
Purkije cells
Processes of the basket cells
Structural features:- Layer I is the molecular layer, and contains few scattered neurons,
including GABAergic rosehip neurons.[21] Layer I consists largely of extensions of
apical dendritic tufts of pyramidal neurons and horizontally oriented axons, as well
as glial cells.[22] During development, Cajal-Retzius cells[23] and subpial granular layer
cells[24] are present in this layer. Also, some spiny stellate cells can be found here
Functions:- . Inputs to the apical tufts are thought to be crucial for
the feedback interactions in the cerebral cortex involved in associative learning and
attention.[25] While it was once thought that the input to layer I came from the cortex
itself,[26] it is now realized that layer I across the cerebral cortex mantle receives
substantial input from matrix or M-type thalamus cells
Structural features:- Inner granular layer (lamina granularis interna) - contains small,
irregularily shaped nerve cells. V. Ganglionic or inner pyramidal layer (lamina
pyramidalis interna) - includes large pyramidal cells.
Functions:- The cerebral cortex is connected to various subcortical structures such as
the thalamus and the basal ganglia, sending information to them along efferent
connections and receiving information from them via afferent connections. Most sensory
information is routed to the cerebral cortex via the thalamus.
Structural features:- The cerebral cortex consists of neurons, nerve fibers and
neuroglia. ... Molecular layer (lamina molecularis) - consists only a few nerve cells. II.
External granular layer (lamina granularis externa) – relatively thin layer consisting of
numerous small, densely packed neurons.
The internal granular layer, layer IV, receives thalamocortical connections, especially
from the specific thalamic nuclei. This is most prominent in the primary sensory cortices.
The infragranular layers, layers V and VI, primarily connect the cerebral cortex with
subcortical regions.
Structural features:- Purkinje cells, also called Purkinje neurons, are neurons in
vertebrate animals located in the cerebellar cortex of the brain. Purkinje cell bodies are
shaped like a flask and have many threadlike extensions called dendrites, which receive
impulses from other neurons called granule cells
Functions:- Most Purkinje cells release a neurotransmitter called GABA (gammaaminobutyric acid), which exerts inhibitory actions on certain neurons and thereby
reduces the transmission of nerve impulses. These inhibitory functions enable Purkinje
cells to regulate and coordinate motor movements
Basket cells synapse on the cell bodies of Purkinje cells and make inhibitory synapses
with Purkinje cells. Cerebellar basket cell axons fire inhibitory neurotransmitters such
as GABA to Purkinje cell axons, and inhibits the Purkinje cell.
48)
.Specimen name:-cererellum
Stain:-:- silver impregnation
Research objects:1.
2.
3.
4.
5.
Molecular layer
Ganglionic layer
Granular layer
Dendrites of the ganglionic nerve cell
Processes of the basket cells
Structural features:- Layer I is the molecular layer, and contains few scattered neurons,
including GABAergic rosehip neurons.[21] Layer I consists largely of extensions of
apical dendritic tufts of pyramidal neurons and horizontally oriented axons, as well
as glial cells.[22] During development, Cajal-Retzius cells[23] and subpial granular layer
cells[24] are present in this layer. Also, some spiny stellate cells can be found here
Functions:- . Inputs to the apical tufts are thought to be crucial for
the feedback interactions in the cerebral cortex involved in associative learning and
attention.[25] While it was once thought that the input to layer I came from the cortex
itself,[26] it is now realized that layer I across the cerebral cortex mantle receives
substantial input from matrix or M-type thalamus cells
Structural features:- Inner granular layer (lamina granularis interna) - contains small,
irregularily shaped nerve cells. V. Ganglionic or inner pyramidal layer (lamina
pyramidalis interna) - includes large pyramidal cells.
Functions:- The cerebral cortex is connected to various subcortical structures such as
the thalamus and the basal ganglia, sending information to them along efferent
connections and receiving information from them via afferent connections. Most sensory
information is routed to the cerebral cortex via the thalamus.
Structural features:- The cerebral cortex consists of neurons, nerve fibers and
neuroglia. ... Molecular layer (lamina molecularis) - consists only a few nerve cells. II.
External granular layer (lamina granularis externa) – relatively thin layer consisting of
numerous small, densely packed neurons.
The internal granular layer, layer IV, receives thalamocortical connections, especially
from the specific thalamic nuclei. This is most prominent in the primary sensory cortices.
The infragranular layers, layers V and VI, primarily connect the cerebral cortex with
subcortical regions.
Ganglion cells are the first type of neuron to differentiate, appearing earliest in the
central retina and later in the periphery. Ganglion cell dendrites extend into the inner
plexiform layer (IPL), a neuropil located on the outer side of the ganglion cell layer.
Basket cells synapse on the cell bodies of Purkinje cells and make inhibitory synapses
with Purkinje cells. Cerebellar basket cell axons fire inhibitory neurotransmitters such
as GABA to Purkinje cell axons, and inhibits the Purkinje cell.
49.
Specimen name:-convolution of brain.
Stain:-silver impregnation
Research objects:1. White matter
2. Cortex of the cerebrum
3. Large pyramidal cells[betz cells]
4. Pia mater
structural features:- White matter is tissue in the brain composed of nerve fibers.
The fibers (called axons) connect nerve cells and are covered by myelin (a type of
fat). The myelin is what gives white matter its white color.
function:- Long thought to be passive tissue, white matter affects learning and brain
functions, modulating the distribution of action potentials, acting as a relay and
coordinating communication between different brain regions. White matter is named
for its relatively light appearance resulting from the lipid content of myelin.
Structural features:- The cerebrum consists of two cerebral hemispheres the outer layer
called cortex (gray matter) and the inner layer (white matter). There are four lobes in
the cortex, the frontal lobe, parietal lobe, temporal lobe, occipital lobe
Functions:- The cerebral cortex is the largest site of neural integration in the central
nervous system. It plays a key role in attention, perception, awareness, thought,
memory, language, and consciousness.
Structural features:-Betz cells are the largest neurons of the cerebral cortex (70 to 100
μm) and are found in the primary motor cortex where they dwarf their neighboring
cortical pyramidal cells.The cerebrum consists of two cerebral hemispheres the outer
layer called cortex (gray matter) and the inner layer (white matter). There are four lobes
in the cortex, the frontal lobe, parietal lobe, temporal lobe, occipital lobe. In this
review article, we will focus on the functions of the cerebral cortex.
Functions:-Pyramidal cells are the most frequent type of neuron in the cortex,
suggesting that they are necessary for the processing of external signals
and motor control. The general morphology of pyramidal cells is very stereotypical and
likely to be the basis of their computational properties.The cerebral cortex is required for
voluntary activities, language, speech, and multiple brain functions, such
as thinking and memory. In addition to the neuron bodies, the cortex also contains
endings of neurons that reach it from other parts of the brain as well as a rich network of
blood vessels.
Structural features:- The pia mater is the meningeal envelope that firmly adheres to the
surface of the brain and spinal cord. It is a very thin membrane composed of fibrous
tissue covered on its outer surface by a sheet of flat cells thought to be impermeable to
fluid.
Functions:- Together with the other meningeal layers, the function of the pia mater is to
protect the central nervous system by containing the cerebrospinal fluid, which
cushions the brain and spine. The cranial pia mater covers the surface of the brain.
50.Cerebral [ brain] cortex.
Stain- Silver impregnation
Research objects:1. Piamater
2. Molecular layer
3. External granular layer
4. External pyramidal layer
5. Internal granular layer
6. Internal pyramidal layer
Structural features:- The pia mater is the meningeal envelope that firmly adheres to the
surface of the brain and spinal cord. It is a very thin membrane composed of fibrous
tissue covered on its outer surface by a sheet of flat cells thought to be impermeable to
fluid.
Functions:- Together with the other meningeal layers, the function of the pia mater is to
protect the central nervous system by containing the cerebrospinal fluid, which
cushions the brain and spine. The cranial pia mater covers the surface of the brain.
Structural features:- Layer I is the molecular layer, and contains few scattered neurons,
including GABAergic rosehip neurons.[21] Layer I consists largely of extensions of
apical dendritic tufts of pyramidal neurons and horizontally oriented axons, as well
as glial cells.[22] During development, Cajal-Retzius cells[23] and subpial granular layer
cells[24] are present in this layer. Also, some spiny stellate cells can be found here
Functions:- . Inputs to the apical tufts are thought to be crucial for
the feedback interactions in the cerebral cortex involved in associative learning and
attention.[25] While it was once thought that the input to layer I came from the cortex
itself,[26] it is now realized that layer I across the cerebral cortex mantle receives
substantial input from matrix or M-type thalamus cells
Structural features The external granular layer of the cerebral cortex is commonly
known as layer II. It is different from the internal granular layer of the cerebral
cortex (commonly known as layer IV). Layer II is often grouped together with layer III
and referred to as layer II/III.
Functions:- The outer granular layer maintains its independent character as a
separate layer only in relatively few regions, where it represents a strip of densely
packed, small polymorphic cells deep to the molecular layer, distinguished from the
actual pyramidal layer by the density and small size of these cells. ...
Structural features Layer III, the external pyramidal layer, contains predominantly
small and medium-size pyramidal neurons, as well as non-pyramidal neurons with
vertically oriented intracortical axons; layers I through III are the main target of
interhemispheric corticocortical afferents, and layer III is the principal source of
corticocortical efferents.
Functions:- The apical dendrites of these cells extend superficially and reach the
molecular layer, whereas the basal processes join the subcortical white matter and then
project again to the cortex, so they serve as both association and commissural
corticocortical fibers.
structural features:- The internal granular layer [layer IV] is a layer composed
mainly of densely packed small granular cells. It receives stimuli mainly from
thalamocortical fibers
function:- The internal granular layer, layer IV, receives thalamocortical connections,
especially from the specific thalamic nuclei. This is most prominent in the primary
sensory cortices. ... Layer V gives rise to all of the principal cortical efferent projections
to basal ganglia, brain stem and spinal cord.
structural features:- Layer V, the internal pyramidal layer, contains large pyramidal
neurons. Axons from these leave the cortex and connect with subcortical
structures including the basal ganglia. In the primary motor cortex of the frontal
lobe, layer V contains giant pyramidal cells called Betz cells,
function:- This layer consists predominantly of the medium-sized and
large pyramidal cells. It is the source of the output or corticofugal fibers. For that
reason, it is most prominent within the motor cortex from which it sends fibers that
mediate motor activity.
51.Cerebral [ brain] cortex.
Stain- Silver impregnation
Research objects:1.
2.
3.
4.
Internal granular layer,
internal pyramidal layer,
multiform layer,
white matter,
structural features:- The internal granular layer [layer IV] is a layer composed
mainly of densely packed small granular cells. It receives stimuli mainly from
thalamocortical fibers
function:- The internal granular layer, layer IV, receives thalamocortical connections,
especially from the specific thalamic nuclei. This is most prominent in the primary
sensory cortices. ... Layer V gives rise to all of the principal cortical efferent projections
to basal ganglia, brain stem and spinal cord.
structural features:- Layer V, the internal pyramidal layer, contains large pyramidal
neurons. Axons from these leave the cortex and connect with subcortical
structures including the basal ganglia. In the primary motor cortex of the frontal
lobe, layer V contains giant pyramidal cells called Betz cells,
function:- This layer consists predominantly of the medium-sized and
large pyramidal cells. It is the source of the output or corticofugal fibers. For that
reason, it is most prominent within the motor cortex from which it sends fibers that
mediate motor activity.
structural features:- Layer VI, the polymorphic or multiform layer, contains few
large pyramidal neurons and many small spindle-like pyramidal and multiform
neurons; layer VI sends efferent fibers to the thalamus, establishing a very
precise reciprocal interconnection between the cortex and the thalamus. [29] That
is, layer VI neurons from one cortical column connect with thalamus neurons that
provide input to the same cortical column
function:- This is the deepest layer of the cortex that directly overlies the subcortical
white matter. ... The axons of the fusiform and pyramidal cells of this layer distribute
corticocortical commissural fibers and corticothalamic projection fibers that end in the
thalamus.
structural features:- White matter is tissue in the brain composed of nerve fibers.
The fibers (called axons) connect nerve cells and are covered by myelin (a type of
fat). The myelin is what gives white matter its white color.
function:- Long thought to be passive tissue, white matter affects learning and brain
functions, modulating the distribution of action potentials, acting as a relay and
coordinating communication between different brain regions. White matter is named
for its relatively light appearance resulting from the lipid content of myelin.
52.Cerebral [ brain] cortex.
Stain- Silver impregnation
Research objects:1.Betz [ large pyramidal ]cells
Structural features:-Betz cells are the largest neurons of the cerebral cortex (70 to 100
μm) and are found in the primary motor cortex where they dwarf their neighboring
cortical pyramidal cells.The cerebrum consists of two cerebral hemispheres the outer
layer called cortex (gray matter) and the inner layer (white matter). There are four lobes
in the cortex, the frontal lobe, parietal lobe, temporal lobe, occipital lobe. In this
review article, we will focus on the functions of the cerebral cortex.
Functions:-Pyramidal cells are the most frequent type of neuron in the cortex,
suggesting that they are necessary for the processing of external signals
and motor control. The general morphology of pyramidal cells is very stereotypical and
likely to be the basis of their computational properties.The cerebral cortex is required for
voluntary activities, language, speech, and multiple brain functions, such
as thinking and memory. In addition to the neuron bodies, the cortex also contains
endings of neurons that reach it from other parts of the brain as well as a rich network of
blood vessels.
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56)
57)
58)
59)
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