CHECK-LIST for HISTOLOGY in the SSB Unit
You should be familiar with the basic vocabulary used to describe nervous tissue, skin, muscle, skeletal tissue, and special sense
organs at the level of tissues and cells. Terms in the following check-list should be recognizable and meaningful when encountered in
your reading (i.e., you shouldn't need a dictionary or a histology atlas to define or identify these terms). To the extent that these
features are visible on ordinary, H&E stained histological preparations, you should be familiar with their appearance.
"The rare moment is not the moment when there is something worth looking at but the moment when we are capable of seeing."
Joseph Wood Krutch
Nerve cells
Neuron, axon, dendrite, cell body
Synapse, synaptic vesicles, synaptic cleft
Peripheral nerve
Epineurium
Sensory and motor axons (including location of cell
bodies and terminals)
Skeleton
Cartilage (matrix, chondrocytes, lacunae)
Bone (Haversian system / osteon, Haversian canals,
lamellae, lacunae)
Bone cells (osteocytes, osteoblasts, osteoclasts)
Bone remodelling
Periosteum, endosteum
Unmyelinated and myelinated axons (including
typical functions)
Schwann cells
Myelin
Nodes of Ranvier (in relation to voltage-dependent
sodium channels and saltatory conduction)
Autonomic ganglia (sympathetic and parasympathetic;
location of cell bodies and efferent axon terminals)
Somatosensory receptor endings (location and
function for Golgi tendon organs, muscle spindles,
Meissner's corpuscles, Pacinian corpuscles, free nerve
endings)
Central nervous tissue
White matter, gray matter
Cortex, nuclei, tracts, commissures
Neurons (e.g., pyramical cells, Purkinje cells, spinal
motor neurons, local interneurons, retinal ganglion
cells)
Afferent and efferent axons
Synapses (pre- and postsynaptic membranes, synaptic
vesicles)
Glial cells (oligodendroglia, astroglia, microglia)
Brain vasculature (especially capillary endothelium in
relation to blood-brain barrier)
Skin
Thin skin, thick (glabrous; palmar and plantar) skin
Epidermal layers (stratum basale, stratum spinosum,
stratum granulosum, stratum corneum)
Epidermal cell types (keratinocyte, Langerhans cell,
Cerebrospinal fluid (CSF)
Choroid plexus (in relation to CSF formation)
Ependyma
Meninges: dura, arachnoid, pia (especially in relation
melanocyte, merkel cell)
Epidermal appendages (sweat gland, sebaceous gland,
hair follicle, hair shaft)
Dermal layers (papillary layer / dermal papillae,
reticular layer)
Cerebral cortex
Cerebellar cortex
Hypodermis
Dermal and hypodermal cell types (fibroblast, mast
cell, macrophage, lymphocyte, adipocyte)
Other dermal and hypodermal structures (arrector
pili muscle, Meissner's corpuscle, Pacinian corpuscle,
veins, arteries, capillaries)
Muscle
Muscle fibers
Muscle ultrastructures (myofibril, myofilaments,
sarcomere, transverse tubules, sarcoplasmic reticulum,
banding pattern: A-band, I-band, Z-line)
Neuromuscular junction
Epimysium, endomysium
Muscle spindle (capsule, intrafusal muscle fibers)
to CSF flow, blood-brain barrier)
Eye
Layers (cornea, sclera, choroid, retina)
Internal structures (iris, lens, ciliary body, ciliary
processes esp. in relation to aqueous humor flow,
canal of Schlemm)
Retina (basic layers: pigmented epithelium,
photoreceptors / rods and cones; bipolar cells,
ganglion cells, axons)
Optic nerve
Inner ear
Bony labyrinth, membranous labyrinth
Endolymph, perilymph
Hair cells (location in maculae, cristae, organ of Corti)
Saccule, utricle, semicircular canals
Cochlea (scala vestibuli, scala tympani, scala media,
organ of Corti, spiral ganglion, stria vascularis)
SSB Histology Lab I
Nerve Cells and Skin
SSB Week 1
The following suggestions are intended to guide your "seeing" in lab, and also to prime your attention for further reading.
Please don't let these exercises limit your experience. On any slide, there is always more to see than seems apparent at first.
___________________________________________________________________________________________________
Slide 24, spinal cord smear.
(Note: This specimen was prepared by smearing, or
squashing, a bit of gray matter onto the slide. It is not a
tissue slice like most other specimens in your slide set.)
(EASY) Find the nucleus of a nerve cell body.
Slide 2, scalp
Slide 3, skin
(EASY) Find epidermis. Question: What kind of tissue
is epidermis?
(EASY) Find a dendrite. Question: Where is the end of
the dendrite? (Is it likely to be on the slide?)
(HARDER) Find the stratum corneum of the epidermis.
Question: What does the presence of keratohyalin
granules reveal about the tissue?
(VERY HARD) Find an axon. Question: How long is
the axon? (Is it likely to fit on the slide?)
(EASY) Find the dermis. Question: What kind of tissue
is dermis?
(EASY) Find the nucleus of a glial cell. Question: How
can you tell the difference between nuclei of nerve cells
and nuclei of glial cells?
(HARDER) Distinguish between papillary and reticular
layers of the dermis.
(THOUGHTFUL) Find the biggest nerve cell body on
this slide. Question: Is this cell most probably a sensory
neuron, a motor neuron, or an interneuron? Why?
(EASY) Find a hair follicle. Question: What kind of
tissue is the hair follicle? Question: Why do hair follicles
present so many different appearances?
(EASY) Find a sebaceous gland.
(HARD) Find an arrector pili muscle.
Slide 23, spinal cord
Repeat the exercises above.
(Look at this slide again in a couple weeks, when you
know more about pathways in the spinal cord.)
Slide 16, peripheral nerve section
Slide 55, artery, vein, nerve
(EASY) Find the epineurium. Question: What kind of
tissue is epineurium? (Can you see fibroblasts?)
(EASY) Find a Schwann cell nucleus.
(IMPOSSIBLE) Find a nerve cell body. Question: Why
is this impossible?
(HARDER) Distinguish axons from myelin. Distinguish
axons of different sizes.
(IMPOSSIBLE) Distinguish sensory from motor axons.
Question: Why is this impossible?
(EASY) Distinguish cross section from longitudinal
section.
(HARDER) On a longitudinal section, find a node of
Ranvier.
(THOUGHTFUL) Count the nodes of Ranvier visible in
one high-magnification field of view of a longitudinal
section of nerve. Question: How could you use this
number to estimate the length of a typical internode?
Why should a clinician care about the length of an
internode?
(HARD) Find a nerve on some other slide. And another.
(EASY) Find an artery and a vein. Hint: Look deep.
(HARDER) Find some capillaries. Hint: There should
be lots, especially in the papillary layer (but they may be
extremely inconspicuous).
(EASY) Find a sweat gland. What kind of tissue is the
gland?
(HARDER) Distinguish the secretory portion of a sweat
gland from its duct.
(EASY) Find a keratinocyte Question: In what layer
should you look?
(HARDER) Find an epidermal cell that is not a
keratinocyte. Question: What other cell type might it be
(list at least three possibilities)?
(EASY) Find collagen. Question: In what layer should
you look?
(EASY) Find adipocytes. Question: Where should you
look?
(EASY) Find any other connective tissue cell. List the
types of connective tissue cells which may occur in skin.
Question: Which ones are typically more common?
(EASY) Find a dying cell with a pyknotic (shrunken)
nucleus. Hint: Look in sebaceous glands.
(HARDER) Find a nerve. Hint: Look deep. Question:
Do the axons in this nerve belong to sensory or motor
nerve cells? Explain why.
(THOUGHTFUL) Compare / contrast skin with
specimens of cornea (slide 25), esophagus (slide 34) and
vagina (slide 77), tongue (slide 29).
SSB Histology Lab II
Muscle and Peripheral Nervous System
SSB Week 2
►►► NOTE: Slide numbers may differ from box to box. If you don't have the slide listed, ask your colleagues.
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INTRODUCTORY COMMENT on MUSCLE.
The structure of striated, skeletal muscle is best studied by
electron microscopy (i.e., through text-book pictures).
In Histology Lab, you should learn to recognize skeletal
muscle -- which means distinguishing it from other
fibrous, eosinophilic structures such as collagen and
smooth muscle.
Slide 34, Esophagus.
(EASY) Find smooth muscle.
(HARD?) This specimen may or may not include a few
striated muscle fibers. (The upper esophagus has striated
muscle, the lower esophagus does not.) If not, try the
same slide number from your colleagues' slide boxes.
Slide 14, Striated Muscle.
(Note: This specimen displays isolated muscle samples,
stained to accentuate the striations. Be sure to appreciate
how plane-of-section affects the appearance of muscle
fibers.)
(EASY) In the longitudinal section, observe striations. In
the cross section, observe fiber diameter and myofibrillar
structure. Note position of nuclei.
Slide 10, Fibrocartilage.
(Note: This specimen includes tissues of the pubic
symphysis, with bone and cartilage as well as muscle.
(EASY) Find the skeletal muscle.
*
*
*
PERIPHERAL NERVOUS TISSUE.
We really don't have any elegant preparations that show
special features of the peripheral nervous system. But
there are a few structures which may be interesting to
find.
Slide 55, artery, vein, nerve
(EASY) Find the nerve(s).
(EASY) Determine whether striated muscle is present.
Slide 15, Muscle, 3 types.
(EASY) Compare and contrast smooth muscle, cardiac
muscle, skeletal muscle. Questions: Can you see
individual cells? Can you really tell where the nuclei are
located?
(HARD?) IF striated muscle is present, look for a muscle
spindle (spindles are present on some but not all
specimens). Question: What makes muscle spindles
recognizable?
Slide 2, 3, 4, Skin
Slide 17, Motor Nerve Endings.
(Note: This is a "just-for-fun" preparation. The specimen
is a teased wholemount, not a section. A small bit of
muscle, at a site of innervation, was dissected free and
placed on the slide.)
(HARD?) Find some neuromuscular junctions. Hint:
Don't just look randomly -- sweep across the specimen at
low power and try to find black-stained nerve fibers.
Then follow these to their destination.
Slides 29, 30, Tongue
(EASY) Find the skeletal muscle (most of the bulk of the
specimen). Note fibers with different orientations (i.e.,
different planes of section).
(HARDER) Make sure you can distinguish muscle from
connective tissue.
(EASY?) Deep in the tongue, this specimen may also
include prominent nerves.
Slide 46, Anal Canal.
(HARD?) This specimen may include both smooth and
striated muscle. Determine what is present.
(EASY?) Find a nerve. Hint: Look deep. Question: Do
the axons in this nerve belong to sensory or motor nerve
cells? Explain why.
(HARD) Find a Meissner's corpuscle. Hint: Don't bother
looking unless the specimen on your slide shows thick
skin. Questions: How do you recognize thick (glabrous)
skin? Where should you look for Meissner's corpuscles?
(EASY or IMPOSSIBLE) Find a Pacinian corpuscle. If
one of these structures is present, it will be obvious (up to
a millimeter in diameter, looking like an onion cut in
half). But most of our slides do not include any.
Slide 18, Sensory Nerve Endings.
(Note: This is another "just-for-fun" preparation. The
specimen is a teased wholemount, not a section. A small
bit of muscle and tendon, at a site of innervation, was
dissected free and placed on the slide.)
(HARD?) Find some sensory endings on the tendon.
Hint: Don't just look randomly -- sweep across the
specimen at low power and try to find black-stained nerve
fibers. Then follow these to their destination. Question:
How can you tell these are not motor endings?
SSB Histology Lab III
Skeletal Tissues
SSB Week 3
►►► NOTE: Slide sets may differ; so, as always, examine slides from more than one box.. Slides 4 and 9 may be
checked out from your instructor or from the MRC, if the slide in your box does not match the description below.
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Slide 4, Fingernail or toenail. (See note above.)
This slide includes the entire tip of a finger or toe,
including cartilage of the developing bone. The specimen
from which it comes was still undergoing development;
so most of the tissues though recognizable, are immature.
(EASY) Find cartilage and/or bone.
Slide 5, Decalcified bone.
"Decalcified" means that this section of bone has had all
of the mineral dissolved away. Some specimens display
active remodelling, others are inactive.
(EASY) First, distinguish "solid" bone tissue from bone
marrow. In the bone tissue, find osteocytes, Haversian
canals. Is any muscle present?
(HARDER) Determine whether your specimen is being
actively remodelled (i.e., look for osteoblasts and
osteoclasts; see slides 6 and 10 for additional examples).
Try to visualize lamellae (easier on "ground bone"
specimens, described below).
Slide 6, Cartilage bone, developing.
This is a decalcified specimen from the epiphyseal end of
an embryonic long bone, displaying the process of
cartilage growth, replacement of cartilage by bone, and
bone remodelling. There should be lots to see.
(EASY) Distinguish bone, bone marrow, cartilage,
ordinary connective tissue. Is any muscle present?
(HARDER) Distinguish various stages of cartilage
maturation. Determine the direction of advancing bone
growth, from the relative age of cartilage tissue in
different positions.
(HARDER) Find osteoblasts and osteoclasts. Which
areas of bone are newly formed and which have already
undergone remodelling? Question: How can childrens'
rigid bones maintain appropriate shape while growing?
Slides 7 and 8, Ground bone.
"Ground bone" means a specimen from which the organic
matter has been removed and the remaining mineral
reduced to a thin sliver by grinding. On this specimen,
Haversian canals, lamellae, lacunae and canaliculi should
be plainly visible. The grainy texture within Haversian
canals is bone dust from the grinding process.
(EASY) What living structures are found in Haversian
canals? Why are lacunae interconnected by canaliculi?
(THOUGHTFUL) Deduce the prior history of osteon
formation and remodelling, by finding older lamellae
("interstitial lamellae") that have been partially removed
and replaced by newer lamellae.
Slides 9, Early Dental Cup. (See note above.)
The title of this slide acknowledges the presence of
developing teeth. But the specimen includes a section
across the entire snout of the fetus of some small animal,
including facial bones, nasal cavities, oral cavity, tongue,
and other anterior head features. All features are
developmentally immature.
(EASY) Find hyaline cartilage, in sites where bone will
form by endochondral ossification.
(EASY) Find spicules of bone in sites, such as mandible
and cranium, where bone is forming by intramembranous
ossification.
(Miscellaneous) Notice the pattern of developing muscle
fibers in the tongue; the peculiar features of developing
teeth. See whether you can recognize other features, by
their anatomical position as well as tissue appearance.
Slide 10, Fibrocartilage
This specimen is a section through the pubic symphysis,
with a more-or-less symmetrical arrangement of bone and
muscle on either side of the midline. The bones are
bound together by a fibrocartilagenous synarthrosis in the
medial region of the preparation.
(EASY) Find muscle, bone, bone marrow, cartilage.
Question: What evidence of bone remodelling can you
find?
(HARDER) Notice the characteristic quality of
fibrocartilage (i.e., although collagen is present in all
cartilage, microscopically visible strands of cartilage are
only apparent in fibrocartilage, where they contribute
extra toughness). Find sites of active bone remodelling.
Slide 11, Elastic cartilage
Observe the cartilage; notice the characteristic "nests" of
cells embedded in matrix. The conspicuous elastic fibers
in the matrix are visible only because of special staining
(hence the peculiar brownish-purple color).
Slide 12, Hyaline cartilage
Observe the cartilage; notice the characteristic "nests" of
cells embedded in a relatively smooth matrix.
Slides 27, Inner ear
(EASY) Find bone. Details of this slide will be
examined later.
Slides 60, 61, Trachea
(EASY) Find the cartilage. Review tracheal layers.
(REVIEW) Find smooth muscle.
SSB Histology Lab IV
Nerve Cells and Glia
SSB Week 4
►►► NOTE: Slide numbers may differ from box to box. If you don't have the slide listed, ask your colleagues.
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Slide 23, Spinal cord.
(EASY) Distinguish white matter from gray matter.
Locate the principal gray-matter regions (dorsal horn,
ventral horn).
(EASY) Associate functional ascending and descending
pathways with particular white matter regions. Dorsal
columns are easy (set off by the dorsal horns), but note
the absence of any markers for particular lateral and
anterior tracts.
(THOUGHTFUL) Determine the approximate level of
the cord section(s) on your slide. Recall that dorsal
columns must be larger in size at higher levels, as more
axons join the tracts at each level. The ventral horn area
is larger in regions serving the upper or lower limbs.
Slide 21. Cerebellar cortex.
The layers of the cerebellar cortex are conspicuous, so
begin by noting the outer "molecular layer" (where nerve
cell bodies are rare), the large cell bodies of the "Purkinje
cell layer", the densely-packed nuclei of the "granule cell
layer", and the underlying white matter.
(EASY) Find blood vessels in both white and gray
matter.
(EASY) Distinguish nerve cell bodies from glia. Nerve
cell bodies have noticable cytoplasm and nuclei that are
large, round, and relatively euchromatic. Glia generally
have inconspicuous (i.e., invisible) cytoplasm and small,
oval, heterochromatic nuclei.
(HARDER) Try to distinguish astrocyte nuclei from
oligodendrocyte nuclei. (You will not be tested on this
distinction.) Note that the nuclei of oligos are smaller and
more heterochromatic than those of astrocytes. Oligos
may be more numerous in white matter.
[For a later lab (week 7): Imagine the complete shape,
including dendrites and axons, of the neurons comprising
the visible layers of the cerebellar cortex. Think about
afferent and efferent axons, as well as the functional
connections locally within the cerebellum.]
Slide 20, Cerebral cortex, pre- and postcentral gyri.
This specimen spans the central sulcus, containing
portions of both precentral gyrus and postcentral gyrus.
The connective tissue in between (i.e., within the sulcus)
is called arachnoid and includes some fairly large blood
vessels.
(EASY) Find blood vessels within the cortex.
(EASY) Distinguish nerve cell bodies from glia.
Note that both vessels and nerve cell bodies may be
surrounded by clear space, an artifact that is relatively
common in nervous tissue due to tissue shrinkage.
(HARDER) Distinguish astrocyte nuclei from
oligodendrocyte nuclei. (Use the same criteria to
distinguish these cell types as in spinal cord, above.)
[For a later lab (week 7): Determine which gyrus is
which. Try to visualize the six layers of the cortex, and
what sorts of connections are typical of each layer. Think
about the synapses occurring in the cortex, with their
associated afferent and efferent axons.]
(EASY) Find blood vessels within the cerebellum.
(EASY) Distinguish nerve cell bodies from glia. Nearly
all of the nuclei in the molecular layer belong either to
glial cells or to capillary endothelium. But note that
within the densely-packed small nuclei of the granular
cell layer, granule cells (small neurons) and glia cannot be
readily distinguished.
Slide 22, Golgi stain, cerebral or cerebellar cortex.
A Golgi stain can, potentially, reveal great detail about
the shapes of cells in central nervous tissue, not only
neuronal dendrites and axons but also glial cell processes.
But the stain is quirky and our samples are not fine
examples of the art. The really large, irregular dark
patches are just masses of crystalized stain. Blood vessels
may also look like big, dark blobs. Nevertheless, with
some patience and care (i.e., thoughtful and diligent
searching), you may be able to find a nice example of a
nerve cell on which you can see dentritic spines, or an
astrocyte with end feet contacting a capillary.
SSB Histology Lab V
Inner Ear
SSB Week 5
On reverse side: Histo Lab VI
Eye, Meninges
SSB Week 6
►►► NOTE: Slide numbers may differ from box to box. If you don't have the slide listed, ask your colleagues.
___________________________________________________________________________________________________
Slide 27, Internal ear.
Unlike the slides of nervous tissue examined
last week, this slide is loaded with interesting
details that are readily visible to the microscopeaided eye. But the inner ear is a complex
structure in three dimensions, and any single
section calls for some thoughtful interpretation.
Inner ear "histology" is more like sectional
gross anatomy, but on very small scale. We are
less concerned with tissues and cells than with
the functional interrelationships of parts.
Our sections are all taken along the axis of the
cochlea, so cochlear structures are reliably
present. Some but not all sections also include
sensory regions of the vestibular system; others
include middle ear bones. Because individual
sections do differ significantly, you are advised
to look at the "same" slide from your colleagues'
slide boxes.
Locate as many as you can of the following
structures, with guidance from your favorite
textbook or atlas.
Asterisks mark those structures that are reliably
present on all slides, but you should be familiar
with the shape and function of all of these
structures.
[Note that this specimen comes from some laboratory rodent. The
proportions of the human cochlea are shorter and broader.]
*bony labyrinth
* perilymph
* vestibule
semicircular canals
* cochlea
*membranous labyrinth
* endolymph
vestibular system
saccule and utricle
maculae
otolith membrane
hair cells
semicircular canals
ampullae
cristae
cupola
hair cells
vestibular ganglion
*cochlea
* vestibular duct (scala vestibuli)
* tympanic duct (scala tympani)
helicotrema
* cochlear duct (scala media)
* organ of Corti
* vestibular (Reissner's) membrane
* basilar membrane
* tectorial membrane
* stria vascularis
* hair cells
* spiral ganglion
On reverse side: Week 6 Lab, Eye, Meninges.
SSB Histology Lab VI
Eye, Meninges
SSB Week 6
On reverse side: Histo Lab V
Inner Ear
SSB Week 5
►►► NOTE: Slide numbers may differ from box to box. If you don't have the slide listed, ask your colleagues.
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Slide 25, Eyeball.
Like the slide of ear examined last week, this
slide is loaded with interesting details that are
readily visible through the microscope.
Locate as many as you can of the following
structures, with guidance from your favorite
textbook or atlas.
sclera
limbus
cornea
epithelium
Bowman's membrane
stroma
Descemet's membrane
"endothelium"
uvea
choroid
blood vessels
iris
ciliary body
ciliary muscle
ciliary zonules
ciliary epithelium = ciliary processes
retina
pigmented epithelium
photoreceptors
rods
cones
outer nuclear layer
outer plexiform layer
bipolar cells
inner plexiform layer
ganglion cells
blood vessels
nerve fiber layer
optic nerve
lens
anterior cuboidal epithelium
lens fibers
vitreous body
aqueous humor
posterior chamber
anterior chamber
canal of Schlemm
Slide 20, Cerebral cortex, pre- and postcentral gyri.
Arachnoid tissue (loose connective tissue), including
some fairly large blood vessels, may be found in the
central sulcus of this specimen. Nervous tissue on either
side of this sulcus represents portions of precentral and
postcentral gyri.
Slide 19, Choroid plexus.
This slide is not especially illuminating, but if you
remember where choroid plexus occurs (in each of the
ventricles of the brain) and what it does (secretes CSF),
you should be able to appreciate that you are looking at an
extremely wrinkled simple cuboidal epithelium. This
epithelium has ventricular space on the apical side and
connective tissue with blood vessels on the basal side.
For thought: Labs V and VI have shown three
locations where a special fluid is secreted.
These are stria vascularis in the scala media of
the inner ear, ciliary processes in the posterior
chamber of the eye, and choroid plexus in the
ventricles -- secreting, respectively, endolymph,
aqueous humor, and CSF. In each case,
secretion and drainage must be balanced or
trouble (Menier's disease, glaucoma, and
hydrocephalus respectively) will develop.
On reverse side: Week 5 Lab, Inner ear.
SSB Histology Lab VII
Cerebral and Cerebellar Cortex
SSB Week 7
►►► NOTE: Slide numbers may differ from box to box. If you don't have the slide listed, ask your colleagues.
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Slide 20, Cerebral cortex, pre- and postcentral gyri.
This specimen spans the central sulcus, containing
portions of both precentral gyrus and postcentral gyrus.
In between are blood vessels and arachnoid connective
tissue.
Review Lab IV -- find blood vessels within the cortex,
and distinguish nerve cell bodies from glia.
Determine which gyrus is which. What function is
served by the pre-central gyrus? . . . post-central gyrus?
First clue: Cortex in primary motor cortex
(Brodmann's area 4) is noticably thicker than that of
primary somatosensory cortex (areas 1,2,3).
Second clue: In layer V of area 4 are
exceptionally large pyramidal cells ("Betz cells"). These
"giant" neuron cell bodies are large because their axons
are much longer than those of most cortical pyramidal
cells, projecting down the pyramidal tract instead of to
another region of the cerebrum. These are the "upper
motor neurons you have learned about elsewhere.
Note that each of Brodmann's areas can be distinguished
by variations in the "cytoarchitecture" of the several
cortical layers. Try to visualize the supposed six layers
of the cortex. This is not obvious. Basically, Layer I is
the outermost "molecular" layer, with relatively few nerve
cell bodies. Layer V is a deeper layer with larger
"pyramidal" cell bodies. With material such as ours, the
in-between layers are mostly just approximate guesses.
Imagine the synaptic connections that are typical for each
layer. Quick summary: The principal output (efferents)
from cortex consists of pyramidal cell axons, which
project to other areas of cortex and to deeper structures.
Dendrites of pyramidal cells ramify in all cortical layers,
with a prominent apical dendrite which extends "upward"
toward into Layer I. Specific afferents (e.g., thalamic
input) is concentrated in Layer IV. Association fibers
(i.e., axons from pyramidal cells in other areas of cortex)
as well as all the various local neurons (granule cells,
stellate cells, horizontal cells, etc.) synapse in Layers I, II,
and III as well as deeper layers.
Slide 21. Cerebellar cortex.
This specimen represents a parasagittal section across
several folia. Because nerve cells of cerebellar cortex are
oriented with respect to the orientation of the folia, the
appearance of the cells as well as gross tissue shape is
affected by plane of section.
Review Lab IV -- note the conspicuous layers of the
cerebellar cortex -- granule-cell layer (lots of small
nuclei), Purkinje-cell layer (single row of individual, large
cell bodies), and molecular layer (few neuronal cell
bodies).
Imagine the complete shape of a Purkinje cell, including
the orientation of its dendrites in relation to its position in
the cortex. Imagine the complete shape of a granule cell, ,
including the orientation of its axon in relation to its
position in the cortex. Imagine the spatial and numerical
relationships between Purkinje cells and granules.
Imagine other afferent axons (mossy and climbing fibers)
and cortical interneurons (basket, stellate, and golgi cells).
Slide 22, Golgi stain, cerebral or cerebellar cortex.
A Golgi stain can, potentially, reveal great detail about
the shapes of cells in central nervous tissue, not only
neuronal dendrites and axons but also glial cell processes.
But the stain is quirky and our samples are not fine
examples of the art. The really large, irregular dark
patches are just masses of crystalized stain. Blood vessels
may also look like big, dark blobs. Nevertheless, with
some patience and care (i.e., thoughtful and diligent
searching), you may be able to find a nice example of a
nerve cell on which you can see dentritic spines, or an
astrocyte with end feet contacting a capillary.
Most of the cerebral cortex Golgi slides include at least a
few pyramidal cells, recognizable by their prominent
apical dendrite.
Most of the cerebellar cortex Golgi slides include several
Purkinje cell dendrites, recognizable by their extremely
numerous dendritic spines.