Modul IB
Nerve tissue
histology and
embryology
Martin Špaček
(m.spacek@centrum.cz)
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Pictures from:
Junqueira et al.: Basic histology
Rarey, Romrell: Clinical human embryology
Young, Heath: Wheather’s functional histology
http://www.med.unc.edu/embryo_images
http://www.meddean.luc.edu/lumen/meded/Histo/frames/
histo_frames.html
http://www.lf3.cuni.cz/histologie
Development
• Formation of the notochord
(notochordal or head process)
• inductive influence on the
overlying ectoderm
Development
• Nerve tissue develops from
the ectoderm
• At the beginning of the 3rd
week the ectoderm
overlying the notochord
forms the neural plate
Development
• Neural plate
• neural groove
• neural folds – approach each other in
the midline, where they fuse ⇒
• Neural tube is formed
• This process is known as
neurulation
Development
• Neural crest
• during neurulation a specialized
portion of the neural plate
separates from the neural tube
• give rise to heterogeneous array
of tissues
Development
• Neural crest
• during neurulation a specialized
portion of the neural plate
separates from the neural tube
• give rise to heterogeneous array
of tissues
••spinal
spinal and
and autonomic
autonomic ganglia
ganglia
•• Schwann
Schwann cells
cells
•• odontoblasts
odontoblasts
•• chromaffin
chromaffin cells
cells of
of the
the adrenal
adrenal medulla
medulla
•• pigment
pigment cells
cells (melanocytes)
(melanocytes)
•• meninges
meninges
•• Merkel
Merkel cells
cells
Development
• Histogenesis of the neural
tube
• the wall of the tube consists of
the pseudostratified columnar
epithelium – neuroepithelium
– formed by 3 zones:
• 1) ventricular zone
• progenitor cells
• 2) intermediate zone
• neurons migrate toward →
• 3) cortical plate
• the future gray matter
lumen
Development
• Histological differentiation
1. nerve cells (neurons)
2. glia cells
„connective tissue of the CNS“
3. neural crest cells
Types of neurons
• According to the number of
processes:
• Multipolar
• the most abundant
• pyramidal cells, Purkinje cells
• Bipolar
• visual, auditory system
• Pseudounipolar
• sensory ganglia
Types of neurons
Types of neurons
• Based on the length of the
axon:
• Golgi type I
• the axon extends beyond the
dendritic tree
• pyramidal cells, Purkynje cells
• Golgi type II
• axon terminates in the
immediate area of the cell body
• stellate cells
Components of a neuron
Perikaryon (soma)
• nucleus
• large, spherical, euchromatic
• prominent nucleolus
• ↑ synthetic activity
• endoplasmic ret.
• Nissl bodies in light microscope
• highly developed
• Golgi complex
• only in the perikaryon
• transfer and secretory vesicles
• mitochondria
• abundant in the axon terminals
• cytoskeleton
• neurofilaments, microtubules
• inclusions
• lipofuscin, melanin
Dendrites
• Are the „receiving“ surface
of the neuron
• Neurons have numerous
dendrites
• Composition of the
cytoplasm is similar to that
of the perikaryon
Axons
• Most neurons have only one
axon
• Originate from axon hillock
• Dependent on the
perikaryon for its
maintenance – axonal
transport
Axonal Transport
• Microtubules form tracks
within the axon to carry
organelles and vesicles
Motor Proteins
Transport Cargo
• Proteins related to axon flow
include
• dynein & kinesin
• they both have two ATPbiding heads & a tail
Synapses
• Enlarged endings of
terminal branches
• Axodendritic
• Axosomatic
• Axoaxonic
Synapses
• Presynaptic ending
• contains synaptic vesicles with
neurotransmitters (chemicals
that cross the synapse between
two neurons)
• Synaptic cleft
• a region of extracellular space
(20-30 nm)
• Postsynaptic ending
• contains receptor sites for
neurotransmitters
Synaptic transmission
N1 – cerebrum (HE)
N2 – cerebrum (Nissl)
Cerebellum
• Cerebellar layers:
• Molecular layer
• mostly neuronal fibers
• Purkynje layer
• large multipolar neurons
• Granule cell layer
• small integrator neurons
N4 – cerebellum (HE)
N4 – cerebellum (HE)
Neuroglia
• 10 glial cells for each neuron
• About half of the volume of
nerve tissue
• Function: provide neurons
with structural support and
maintain local conditions for
neuronal function
• Staining: silver or gold
impregnation, histochemical
technique
• 4 morphologic types
I. astrocytes
• The largest
• Vascular feet – surround and
ensheathe all vessels
• Structural support for nerve
tissue
• Form glial scar
I. astrocytes
• A. protoplasmic
• granular cytoplasm
• envelop the surface of nerve
cells and blood vessels
• B. fibrous
• long processes
• predominantly in white matter
I. astrocytes
N8 – cerebrum
(astrocytes), Antibody
Anti-S-100 protein, ABC
II. oligodendrocytes
• Smaller, ↓processes
• Processes envelop axons
and form myelin sheath
• Are found in both gray and
white matter
• The formation of the myelin
sheath is similar to that of
Schwann cells in peripheral
nerves
II. oligodendrocytes
III. microglia
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Phagocytic cells
Derived from mesoderm
Small cell bodies
Their nuclei have elongated
shape
• other neuroglia have spherical
• Short processes with small
expansions – thorny
appearance
III. microglia
IV. ependymal cells
• Epithelial arrangement
• Line the cavities of the
brain and spinal cord
• Motile cilia (movement of the
cerebrospinal fluid)
N5 – spinal cord (HE)
• Central canal of spinal cord lined with
ependymal cells
Nerve fibres
• Consist of axons enveloped
by special sheaths of
ectodermal origin
• Groups of nerve fibres
constitute:
• the tracts of the brain
(oligodendrocytes)
• peripheral nerves (Schwann
cells)
• Fibres:
• unmyelinated
• myelinated
Unmyelinated fibres
• CNS – axons run free
among the other neuronal
and glial processes
• PNS – axons are enveloped
within simple clefts of
Schwann cells
Unmyelinated fibres
Myelinated fibres
• myelin formation:
• in the PNS a single axon is
embedded in a Schwann cell
• the plasma membrane of a
Schwann cell wraps in a
spiral around the axon
Myelinated fibres
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S – Schwann cell nucleolus
A – axonal cytoplasm
M – myelin sheath
13 – Myelinated axon
Myelinated fibres
Myelinated fibres
• nodes of Ranvier – gaps
between Schwann cells
N3 – cerebrum (Myelin)
Peripheral nervous
system
• nerves
• nerve fibres grouped in bundles
• connective tissue coverings:
• endoneurium
• perineurium
• epineurium
Nerves
Nerves
Nerves
N7 – peripheral nerve (HE)
N7 – peripheral nerve (HE)
Peripheral nervous
system
• Ganglia
• aggregations of nerve cell
bodies outside the CNS
• a connective tissue capsule
• each neuronal cell body is
surrounded by Schwann celllike satellite cell
• Two main classes
• craniospinal (sensory)
• autonomic (motor)
N6 – autonomic ganglia
(HE)
Meninges
Meninges
• Dura mater
• external meninx
• dense connective tissue
• subdural space
• Arachnoid
• connective tissue devoid of
blood vessels
• a layer in contact with dura
mater
• system of trabeculae –
cavities form subarachnoid
space (filled with CSF)
• Pia mater
• loose connective tissue
containing many blood
vessels
Meninges