The document provides an eye and ear study guide that summarizes key structures and features. For the eye, it describes the three tunics (layers) that make up the eye wall, as well as internal structures like the aqueous and vitreous compartments, lens, zonular fibers, and retina. It also summarizes key features of the eyelid. For the ear, it outlines the external structures of the auricle and external auditory meatus, as well as the middle ear ossicles and auditory tube, and mentions the two main components of the inner ear.

1. Eye Study Guide
Samantha Blum

2. Tunics
• The wall of the eye is composed of three basic
tunics. The basic tunics are regionally modified to
accomodate specific functions.
– Tunica fibrosa. This outermost tunic comprises the
cornea and sclera. It is the only tunic that is
continuous around the entire eye.
– Tunica vasculosa (uvea). This middle tunic comprises
the choroid, and part of the ciliary body and iris.
– Tunica interna. This innermost tunic comprises the
retina, and part of the ciliary body and iris.

3. Compartments and Internal Structure
• 1. Aqueous compartment. This space is filled
with a CSF-like fluid, the aqueous humor, that is
continually replenished and recycled. Identify
anterior and posterior chambers (2X, 2X). What
are the boundaries of each chamber?
• 2. Vitreous compartment (2X, 2X). The vitreous
body, a transparent, collagenous gel, fills this
compartment. Do not confuse the vitreal
chamber with the posterior chamber.
• 3. Lens (2X, 2X).
• 4. Zonular fibers.

4. Anterior chamber
Lens
Vitreous
compartment Posterior chamber

5. Tunica Fibrosa
• This layer is comprised of the sclera
(posteriorly) and the cornea (anteriorly). Both
structures are formed predominantly by
extracellular C.T. components.

6. Tunica Fibrosa:
Sclera
• This region begins at the corneoscleral limbus (2X, the junction
between the cornea and sclera) and extends posteriorly. Note that
it is opaque.
• Identify the bulbar conjunctiva (2X, 10X) epithelium that covers the
anterior portion (analogous to the "white of the eye").
• Identify the limbus at the corneoscleral junction (2X).
• Identify the region containing the lamina cribrosa (2X, 10X) of the
sclera at the optic disc (the sclera will be obscured here by the optic
nerve).
• Identify the Canal of Schlemm (4X, 10X, 20X).
• Identify the trabecular meshwork (4X, 10X, 20X), located at the
iridocorneal angle (4X).
• What is the function of the trabecular meshwork?
• Note the fibrous nature of the scleral stroma (10X).

8. Tunica Fibrosa:
Cornea
• This clear anterior continuation of the tunica fibrosa is responsible
for the majority of the refraction (bending of light) necessary for
image focusing. Why? The cornea has five histological layers.
Anterior epithelium. (20X, 50X)
• Bowman's membrane (anterior limiting membrane). This structure
is the basement membrane of the anterior epithelium (50X).
• Substantia propria (stroma). Note that this avascular layer accounts
for 90% of the corneal thickness (20X, 50X).
• Descemet's membrane (posterior limiting membrane). This is the
basement membrane of the posterior epithelium (100X).
• Posterior epithelium. Note the low cuboidal "endothelial" cells
(100X).

9. Tunica Vasculosa (Uvea):
Choroid
• The choroid (40X) has four histological layers.
• Suprachoroid. This is an avascular layer of loose
C.T., melanocytes and nerves.
• Vascular layer. (100X) This layer is characterized
by prominent veins and small arteries (20X).
• Choriocapillaris (Choriocapillary layer). (100X)
The capillaries in this layer directly nourish the
outer half of the retina.
• Basal layer, or Brüch's membrane. (100X) This
structure is the basement membrane of the
retinal pigment epithelium.

10. Choroid
Vascular layer
Retina
Choriocapillaris

11. Tunica Vasculosa (Uvea):
Ciliary Body
• The ciliary ring and ciliary crown are gross structures that are
best seen in an axial view (remember that they are circular
structures).
• Locate the ciliary muscle (4X, 40X). What type of muscle is it?
– Smooth muscle

12. Tunica Vasculosa (Uvea):
Iris
• This structure (2X) changes shape to regulate the size of the pupil. The iris is
predominantly uveal; the only non-uveal portion is the epithelium that lines its
posterior surface.
• Identify the uveal portion (4X, 20X, 40X) of the iris, and note that it has two layers,
the anterior border layer and the stroma.
• Note that the anterior border layer (20X, 40X) is thin and avascular.
• Identify the stromal layer, and note that it is thick and vascular, and contains a
variable amount of pigment cells. This pigment is responsible for "eye color".
• Note that the iris has no epithelial covering (40X) on its anterior surface.
• Identify the pupil (2X).
• Identify the sphincter pupillae (4X, 20X, 40X, 50X) muscle in the stroma. These
smooth muscle fibers are arranged circumferentially around the edge of the iris,
and are under parasympathetic cholinergic control. By shortening, they reduce the
diameter of the pupil (schematic).
• Indentify the dilator pupillae (50X). These myoepithelial fibers are arranged
radially around the iris, and are under sympathetically innervated. By shortening,
they increase the diameter of the pupil (schematic).

14. Tunica Interna:
Layers of Retina
• Retinal neurons and glia are organized into readily-identifiable histological layers. Identify the
following: Pigmented cell layer (retinal pigment epithelium, RPE). This is the epithelium on which
the retina rests; it functions to regenerate bleached photopigment, and to phagocytose
degenerated discs from the photoreceptors.
• Note that the epithelium is simple cuboidal (50X, 100X).
• Identify pigment granules (100X).
• Rod and cone layer.
• Identify outer segments of rods and cones (schematic; 100X). Membranes within the outer
segments contain the photosensitive pigment rhodopsin.
• Outer nuclear layer (20X, 100X). This layer contains the cell bodies and nuclei of the photoreceptor
cells .
• Outer plexiform layer (20X, 100X, 100X). The synaptic terminals of photoreceptors make contact
here with bipolar and horizontal cells.
• Inner nuclear layer (20X, 100X, 100X). This layer contains the cell bodies of bipolar cells, horizontal
cells, and amacrine cells.
• Internal plexiform layer (50X). Several types of retinal neuron interact synaptically in this layer.
Information about light is transmitted to the ganglion cells, whose dendrites are found here.
• Ganglion cell layer (20X, 50X, 100X). This layer contains the cell bodies of ganglion cells.
• Nerve fiber layer (20X, 50X, 100X). The axons of the ganglion cells run on the inner surface of the
retina, heading toward the optic disk (see below).
• **THE LAYERS OF THE RETINA DIFFER IN 2 AREAS OF SPECIALIZATION: FOVEA AND OPTIC DISK

15. Tunica Interna:
Fovea
• Within the fovea (4X, 20X), the number of retinal layers is
reduced, because only the photoreceptors are present. The
photoreceptor axons make their normal synaptic
connections (to bipolar cells), but those bipolar cells lie
outside the foveal region, so the photoreceptor axons must
run laterally to get to them.
• Look for a thinning of the retina (4X, 20X) at the posterior
pole, and note the absence of the inner retinal layers at this
point.
• What effect does this retinal thinning have on visual acuity?
• To what region of the visual field does the fovea
correspond?

17. Tunica Interna:
Optic Disk
• At this point, the axons of ganglion cells leave the globe
through a perforated region of the sclera (the lamina
cribrosa, 10X).
• Look for an indentation in the inner (vitreal) surface of
the retina, and note the complete absence of any of
the normal retinal layers here (10X, 20X).
• Note that the optic nerve passes completely through
the sclera, to exit the globe.
• Note that the sclera is continuous with the sheath of
the optic nerve (10X, which is, in turn, continuous with
the dura of the brain).

18. Tunica Interna:
Retinal Blood Supply
• Identify capillaries in the retina (50X). These form
two plexuses, one in the ganglion cell layer and
one in the outer plexiform layer. These capillaries
are fed by branches of the central retinal artery,
which lie on the inner (vitreal) surface of the
retina. These capillaries nourish the inner half of
the thickness of the retina.
• Note that the outer half (50X) of the retina is
avascular. How is it nourished?

19. Retinal Blood Supply
Capillaries in GCL

20. Tunica Interna:
Pars ciliaris retinae
• The name means "the ciliary part of the retina". The photosensitive retina
continues anteriorly, losing its photosensitive properties, and thins down
to become the double epithelium that covers the ciliary body and the
posterior surface of the iris. This epithelium also produces aqueous
humor.
• Identify the outer, pigmented epithelium (10X, 40X).
• Identify the inner, non-pigmented epithelium (10X, 40X).
• Note that these two layers are in intimate contact with one another (as
are the RPE and the photosensitive retina, more posteriorly).
• Identify ciliary processes (10X, 40X), which are extensions of the ciliary
epithelium that protrude into the posterior chamber.
• Identify zonule fibers (10X) extending from the ciliary processes to the
lens epithelium.
• What important substance is produced by the ciliary epithelium?
– Aqueous humor

21. Tunica Interna:
Pars iridica retinae
• The name means "the iridical part of the retina". The double epithelium of the
pars ciliaris continues all the way to the tip of the iris at the pupillary opening.
• Identify the two epithelial layers (50X, 50X) covering the posterior surface; note
that both layers contain pigment here.
• Identify the anterior myo-epithelial layer (50X, 100X), which forms the dilator
muscle (dilator pupillae) of the iris.

22. Lens
• The lens (2X) is an avascular, highly specialized epithelial
structure with three components: lens capsule, lens
epithelium, and lens fibers.
• The lens capsule (20X, 40X, 40X) surrounds the entire lens;
this capsule is actually the basement membrane of the lens
epithelium.
• The lens epithelium (subcapsular epithelium; 40X) is a
simple cuboidal layer that covers only the anterior portion
of the lens.
• The body of the lens consists of large numbers of individual
lens fibers; these are highly specialized cells that develop
from the anterior subcapsular epithelium, and that extend
all the way to the posterior surface of the lens (40X; 40X).

23. Lens
Capsule
Epithelium
Fibers

24. Zona Ciliaris
(Zonule Fibers)
• Identify this suspensory ligament of lens (10X), which takes the form of a
group of colorless, refractile fibers between ciliary processes and lens.
• What effect does contraction of the ciliary muscle have on the shape of
the lens?
– Relaxes (thickens) the lens and improves near vision

25. Aqueous Humor
• Aqueous humor is an ultrafiltrate of plasma that circulates through the anterior
portion of the eye at high pressure. For the maintenance of the correct pressure,
the rate of synthesis and reuptake must be balanced. A rise in intraocular pressure
(IOP) can lead to retinal damage and consequent blindness (glaucoma).
• Identify the following structures or spaces involved in the production, circulation,
and removal of aqueous humor (2X):
• Synthesis by the ciliary epithelium (especially the ciliary processes).
• Release into the posterior chamber.
• Flow into the anterior chamber via the pupil (and, to some extent, by percolating
through the body of the iris).
• Filtration and uptake by the trabecular meshwork. Note that a reduction in the
iridocorneal angle (e.g. by partial collapse of the iris onto the meshwork) might
lead to occlusion (blockage) of the trabecular meshwork, and cause an increase in
intraocular pressure.
• Drainage into the Canal of Schlemm.
• Return to the general circulation, via drainage into scleral veins.

26. Eyelid
• The eyelid is a thin sheet of tissue with a
muscular core. It covers the front surface of the
eye, moving vertically over the cornea to keep its
surface clean and moist. The inner surface lies
against the cornea, trapping a thin layer of tear
fluid; this fluid is a mixture of the secretory
products of the lacrimal (tear) gland, tarsal
(Meibomian) glands, and glands of Moll. The
latter two sets of glands are located within the
eyelid.

27. Eyelid
• The external surface of the eyelid has a covering of skin with hair follicles and associated sebaceous
glands, and sweat glands (1x, 5x).
• On the inner (conjunctival) surface, note that the lining epithelium varies from simple cuboidal to
stratified cuboidal, and may contain goblet cells (20x). Bacterial infections of this membrane, called
conjunctivitis, cause it to be inflamed and red ("pink eye").
• Identify the cluster of large, sebaceous-like glands that comprise the tarsal plate (5x). These tarsal
(Meibomian) glands all drain via ducts located at the tip of the eyelid (10x). They secrete an oily substance
that floats on the surface of the serous tear fluid produced by the lacrimal gland. Inflammation of tarsal
glands causes swelling of the eyelid ("chalazion").
• Identify the skeletal muscle fascicles of the orbicularis muscle (5x).

28. Ear Study Guide
Samantha Blum

29. Auricle
• Examine the cartilage framework of the
auricle, and note that it is comprised of elastic
cartilage (2X, 20X).
• Note that the auricle is covered by thin skin
(2X, 10X).

30. External Auditory Meatus
• Identify elastic cartilage (2X).
• Examine the epidermis of the meatus
(2X), and note that it is a keratinized stratified
squamous epithelium (40X).
• Identify sebaceous glands (4X, 20X) and
ceruminous glands (4X, 40X).
• Identify hair follicles (4X, 10X).

31. Keratinized, stratified squamous

32. The Middle Ear
• A. Tympanic cavity.
• B. Ossicles.
– Malleus.
– Incus.
– Stapes.
• C. Auditory Tube.
– Note that this structure has both bony and
cartilaginous regions.

33. Inner Ear
• The two main components of inner ear are the bony labyrinth
and the membranous labyrinth. The membranous labyrinth is
a continuous, membrane-enclosed compartment within bony
labyrinth; it closely follows the shape of the bony labyrinth.
• Membranous labyrinth has 2 divisions:
– Vestibular division
– Cochlear (auditory) division

34. Vestibular Division of the Membranous Labyrinth:
Utricle & Saccule (Otolith Organs)
• These regions contain receptors responsible for detection of static head
position and linear acceleration (not all slides contain these regions).
Identify the sensory epithelium and its specializations: maculae
(schematic; 4X, 20X, 50X), otolithic membrane (50X) and otoconia (20X,
50X).

35. Semicircular Ducts
• Each semicircular canal (4X, 20X, 4X, 10X) has an
enlargement at its base, in which is located the sensory
apparatus (the crista ampullaris) that detects
movement of fluid through the canal. Identify the
following:
• Crista ampullaris (schematic; 4X, 20X, 40X).
• Sensory hair bundles (40X) extending into the
gelatinous cupula (20X, 40X).
• What type of motion does the semicircular canal
detect?
• What cranial nerve (and division) contains the axons of
sensory neurons in the crista ampullaris?

36. Cochlear Duct
(Scala Media)
• This is the portion of membranous labyrinth that extends
into the bony labyrinth of the cochlea, like a tunnel within a
tunnel. It is attached at two sides along its length to the
cochlea (osseous labyrinth), creating three compartments.
Identify:
• a. Spiral ligament (10X) and spiral limbus (10X).
• b. Scala vestibuli (10X, 10X) and vestibular membrane
(10X).
• c. Scala tympani (10X, 10X) and basilar membrane (10X).
• d. Scala media (4X, cochlear duct).
• e. Modiolus (4X)
• f. Bony (osseous) lamina (10X).

37. Cochlear Duct

38. Organ of Corti
• This is the site where sensory epithelial cells transduce sound vibrations
into electrical signals for sound perception. A number of cell types and
structures are of interest and readily studied on your slides.
• Identify the basilar membrane (50X) that supports the Organ of Corti.
• How do sounds affect the basilar membrane?
• Identify inner and outer hair cells (50X).
• Look for stereocilia (50X).
• Identify the tectorial membrane (50X). What happens to this membrane,
and to the hair cells, when sound vibrations pass into the cochlea?
• Identify cells of the spiral ganglion (10X). Which cranial nerve (and
division) is formed by the axons of these cells?
• Which region of the cochlea detects the highest sound frequencies? The
lowest? How does this arrangement affect the pattern of hearing loss
caused by exposure to loud noises?

39. Organ of Corti

40. Central Nervous System
Samantha Blum

41. Central Nervous System
• The major components of the central nervous system (CNS)
are neurons and neuroglia. Connective tissue is essentially
absent.

42. White Matter of Spinal Cord
• Identify myelinated axons in cross-section
(10X; 40X).

43. Gray Matter of Spinal Cord
• On the silver-stained slide, identify myelinated axonal fibers (10X) and
unmyelinated axonal fibers (20X). Why are axons present in gray matter?
– Axons traverse the gray matter to make connections between white matter
• Note the various nerve fiber sizes.

44. Neuroglia
• The staining method used here does not
demonstrate the cytoplasm of neuroglial cells,
only their nuclei. One can, however, identify
the first three cell types on the basis of
nuclear appearance.

45. Astrocytes
• These cells have large, pale nuclei, and are the
most numerous of the neuroglia in gray
matter. Find them in the cerebral cortex of this
slide (40X; special stain). They occupy most of
the space between neurons.

46. Astrocytes (astrocyte stain)

47. Astrocytes (H&E)

48. Microglia
• The fine, highly branched processes of these cells are not
visible in H&E preparations; only their nuclei are visible (atlas
example). As a result, you will not be able to reliably identify
neuroglia in your slides.

49. Oligodendrocytes
• These cells are responsible for forming the myelin
ensheathment present around some CNS axons.
• Look in areas of white matter first. Note that
oligodendrocytes are the predominant neuroglial cell
type of white matter. Why would you expect to find
them in gray matter?
– Axons are concentrated in white matter; there are some
axons present in gray matter, so there will be some (but
significantly less) oligodendrocytes in gray matter
• Look for their nuclei, which are small, round, and
darkly-stained (100X). Oligodendrocyte processes do
not stain with H&E.

50. Oligodendrocytes

51. Ependymal Cells
• The cerebral ventricles and aqueduct are lined
with a simple cuboidal epithelium, the
ependyma, made up of two types of cells: 1.
Ependymal cells have cilia, and are attached
to one-another with belt desmosomes; the
latter structures prevent leakage of fluids
between ependymal cells. 2) Tanycytes; these
specialized ependymal cells send processes
into the neuropil to make contact with blood
vessels.

52. Ependymal Cells:
Cerebral Ventricle
• Examine the lining of the ventricle in this section of midbrain
(1X).
• Note that the simple cuboidal epithelial lining is formed by a
single layer of ependymal cells (5X).
• Look for cilia at the luminal surface (40X).

53. Ependymal Cells:
Central Canal of Spinal Cord
• Examine the lining of the central canal (which
may have collapsed), identifying ependymal
cells (1X; 20X; 50X).

54. Ependymal Cells:
Central Canal of Spinal Cord

55. Ependymal Cells:
Choroid Plexus
• Identify regions where blood vessels have
penetrated into the ventricular space, forming
tufts of capillaries covered by a layer of cuboidal
ependymal cells. (1x, 1x, 4x, 10x, 40x).
• Cerebrospinal fluid, which is an ultrafiltrate of
plasma, is extruded through the permeable walls
of these blood vessels, then transported into the
ventricular lumen by the ependymal cells.
• Note that many ependymal cells are ciliated
(40x). Why?

56. Choroid Plexus

57. Meninges
• The brain lies within a three-layered
connective tissue capsule. The innermost two
layers, the pia mater and the arachnoid
mater, are not readily seen in this slide.

58. Dura Mater
• This thick outermost layer is composed of
dense fibroelastic connective tissue (50X).