Reading: RR&K, Chapters 13 and 14
SLIDE 39a eye, monkey (H&E)
(RR&K p761, Fig.1; p765, Fig. 1,2; p767, Fig. 1,2,3)
This slide is a section through the whole eye of an adult monkey. Identify the following structures:
Using high power observe the cornea. The outer layer is an epithelium which typically is five cells thick. The epithelium developed from the surface ectoderm. Bowman's membrane lies between the epithelium and the underlying connective tissue. The stroma of the cornea is composed of a very regular arrangement of collagen fibers. The regular arrangement can be easily seen in TEM preparations of the cornea (see Figure 23.4). Internal to the stroma of the cornea and adjacent to the anterior chamber is an endothelium that arises embryologically from mesoderm. The corneal endothelium typically is a simple cuboidal epithelium.
The sclera or white of the eye is dense connective tissue that provides attachment sites for muscles. This slide shows the layers of the iris. The anterior layer has two smooth muscles: the sphincter pupillae muscle (in cross section on your slide) and dilatator pupillae muscle cut longitudinally. The posterior layer of the iris is pigmented, as is the posterior (inner) layer of the ciliary body. The ciliary body is located peripheral to the lens. Look for the very fine suspensory ligaments of the lens running from the ciliary body to the lens. You should be able to find the iridocorneal angle of the eye formed between the iris and cornea.
The fluid produced by the finger-like processes of ciliary body, the aqueous humor, circulates from the posterior chamber through the pupil, into the anterior chamber, and in the area of the iridocorneal angle. Next, the aqueous humor passes through the trabecular meshwork of pectinate ligaments and into the venous sinus of sclerae known as the canal of Schlemm. The canal of Schlemm connects with small veins on the surface of the sclera, so the ultimate destination of fluid is to the vascular system.
Observe the ciliary body and identify the ciliary muscle which has two types of fibers. Anteriorly, superficially located are longitudinal (meridional) fibers of ciliary muscle. Deeper you can recognize a cross-section of the circular fibers. Both muscles are essential the accommodation: longitudinal fibers increase and circular fibers decrease the tension via suspensory ligaments on the lens, which changes its shape depending on the focal point. The lens has an anterior layer that is one cell layer thick. As the cells mature they change position and elongate. Note the elongated lens fibers seen behind the anterior layer of cells. The lens is enclosed within a capsule which is located outside of the cellular layers. Interior to the lens is the vitreous body. This is a cavity filled with a transparent gel. The layers of the retina (outer toward inner) are: pigmented epithelium, layer of rods and cones, outer limiting membrane, outer nuclear layer, outer plexiform layer, inner nuclear layer, inner plexiform layer, ganglion cell layer, optic nerve fiber layer, and inner limiting membrane. A description of these layers is provided with the next slide.
The choroid is a region continuous with the ciliary body and adjacent to the retina. It contains the vascular supply of nutrients to the retina. It also contains many pigmented cells which assist in absorbing light thus preventing glare within the eye. On some slides the uvea is present. This region lacks rods and cones and consists mostly of choroid.
Check list for SLIDE 39a:
SLIDE 38c retina, chick (H&E)
(RR&K p763, Fig.1,2,3)
This slide has one or more pieces of retina. The retina may be curled up because it is too delicate to retain its shape during processing. To orient yourself, locate the pigmented epithelium which are epithelial cells containing brown pigment. This epithelium is the outer most layer of the retina. The layers of the retina (outer toward inner) are:
Light passes through layers j-c before the light signal is sensed by the rods and cones in layer b. The sensory impulse begins in the rods and cones and travels in the opposite direction from the rods and cones to the conducting neurons (bipolar neurons and ganglion cells) and finally to the optic nerve and the brain.
Check list for SLIDE 38c:
SLIDE 42f eyelid (H&E)
(RR&K p757, Fig. 23.10)
Examine the anterior surface of the eyelid (palpebra) noting the epidermal layers and character of the dermis. Follow the anterior surface of the eyelid around to the posterior surface. At the margin of the eyelid, the epidermis becomes continuous with the epithelium of palpebral conjunctiva. Note the changes that occur as one proceeds from the keratinized epithelium to the mucus lining surface. What changes are evident to you? Note that the conjunctiva of the lid consists of stratified columnar epithelium and is rather fragile; thus, it is important to examine only those areas that are clearly intact to make your assessment. Close to the palpebral conjunctiva is a tarsal plate. In this plate made of dense irregular connective tissue are embedded, long, complex sebaceous tarsal (Meibomian) glands. These differ from sebaceous glands in the thin skin (scalp) in that the terminal alveoli are connected by short lateral ducts to a long central excretory duct. Observe hair follicle of the eyelashes which are usually arranged in three or four rows along the edge of the eyelid and have very small associated sebaceous glands (of Zeis). Observe apocrine sweat glands between hair follicles. Also identify the section of the palpebral part of orbicularis oculi muscle. Classify its muscle type.
Check list for SLIDE 42f:
SLIDE 43a cochlea, guinea pig (H&E)
(RR&K p793, Fig.1,2; p795, Fig.1,2)
Study this section of the temporal bone (petrous portion) with the reversed ocular and then with the 10X objective lens. Scan the entire slide and identify the cochlea and the modiolus. With the 40X objective lens, examine the details of the modiolus and cochlea. The modiolus is composed of spongy bone. It is the axis of the cochlear wall that transmits blood vessels and the cochlear portion of the VIII cranial nerve. Outside the modiolus, locate the cochlear duct, which spirals 2: turns around the modiolus in humans. The cochlear duct is triangular in appearance and bordered by vestibular (Reissner's) membrane, basilar membrane, and the lateral cochlear wall. Reissner's membrane extends from the bony spiral lamina to the lateral cochlear wall. The lateral cochlear wall is composed of the stria vascularis and the spiral ligament. On the basilar membrane is the Organ of Corti, which is composed both of sensory hair cells, receptor cells for hearing, and supporting cells. At the base of the hair cells are dendrites of the cochlear portion of the VIII cranial nerve. The axons of the cochlear portion of the VIII cranial nerve pass distally through the modiolus to cochlear nuclei within the brain stem. The cell bodies of these neurons form the spiral ganglion. The spiral ganglion cells are located in the modiolus. Where would you find satellite and Schwann cells? The space within the cochlear duct is called the scala media, which contains fluid called endolymph (high K+, low Na+ content). The placement of the cochlear duct within the cochlear canal divides the space into two additional compartments, the scala vestibuli superiorly and the scala tympani inferiorly. These spaces contain fluid, called perilymph (high Na+, low K+ content), and are continuous with one another at the apex of the cochlea.
Check list for SLIDE 43a: 
The eye and ear are extremely intricate organs which allow us to see and hear our environment. The ear also houses the structure necessary to maintain balance: the vestibular apparatus. This unit takes a look at the eye and ear and their structural components