CHECK-LIST for HISTOLOGY in the SSB Unit



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)

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)

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, melanocyte, merkel cell)

Epidermal appendages (sweat gland, sebaceous gland, hair follicle, hair shaft)

Dermal layers (papillary layer / dermal papillae, reticular layer)

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)

Skeleton

Cartilage (matrix, chondrocytes, lacunae)

Bone (Haversian system / osteon, Haversian canals, lamellae, lacunae)

Bone cells (osteocytes, osteoblasts, osteoclasts)

Bone remodelling

Periosteum, endosteum

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)

Cerebrospinal fluid (CSF)

Choroid plexus (in relation to CSF formation)

Ependyma

Meninges: dura, arachnoid, pia (especially in relation to CSF flow, blood-brain barrier)

Cerebral cortex

Cerebellar cortex

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.

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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.

(EASY) Find a dendrite. Question: Where is the end of the dendrite? (Is it likely to be on the slide?)

(VERY HARD) Find an axon. Question: How long is the axon? (Is it likely to fit on the slide?)

(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?

(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?

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.

Slide 2, scalp

Slide 3, skin

(EASY) Find epidermis. Question: What kind of tissue is epidermis?

(HARDER) Find the stratum corneum of the epidermis. Question: What does the presence of keratohyalin granules reveal about the tissue?

(EASY) Find the dermis. Question: What kind of tissue is dermis?

(HARDER) Distinguish between papillary and reticular layers of the dermis.

(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.

(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 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.

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?

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.

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.

* * *

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.

(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

(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.

(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.

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.]

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 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.

[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 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.

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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 microscope-aided 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.

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