Procedure Astructure And Function Of The

1. Review a textbook section on the structure of the eye.

2. As a review activity, label figures 35.1, 35.2, and 35.3.

3. Complete Part A of Laboratory Report 35.

4. Examine the dissectible model of the eye and locate the following features:

eyelid conjunctiva orbicularis oculi levator palpebrae superioris lacrimal apparatus lacrimal gland canaliculi lacrimal sac nasolacrimal duct extrinsic muscles superior rectus inferior rectus medial rectus lateral rectus superior oblique inferior oblique trochlea (pulley)

cornea sclera optic nerve

Figure 35.1 Label the structures of the lacrimal apparatus.

Figure 35.1 Label the structures of the lacrimal apparatus.

Eye Labeling Lateral View
Figure 35.2 Label the extrinsic muscles of the right eye (lateral view).
Function Fovea Centralis

Figure 35.3 Label the structures indicated in this transverse section of the left eye (superior view).

Medial rectus

Conjunctiva

Figure 35.3 Label the structures indicated in this transverse section of the left eye (superior view).

Medial rectus

Conjunctiva

Function Fovea Centralis

Lateral rectus

(contents)

(cavity)

Lateral rectus

choroid coat ciliary body ciliary processes ciliary muscles lens suspensory ligaments iris anterior cavity anterior chamber posterior chamber aqueous humor pupil retina macula lutea fovea centralis optic disk posterior cavity vitreous humor

5. Obtain a microscope slide of a mammalian eye section, and locate as many of the preceding listed features as possible.

6. Observe the posterior portion of the eye wall using high-power magnification, and locate the sclera, choroid coat, and retina.

7. Examine the retina using high-power magnification, and note its layered structure (fig. 35.4). Locate the following:

nerve fibers leading to the optic nerve (innermost layer of the retina)

layer of ganglion cells layer of bipolar neurons nuclei of rods and cones receptor ends of rods and cones pigmented epithelium (outermost layer of the retina)

Figure 35.4 The cells of the retina are arranged in distinct layers (75x).

Direction of light

Inside of eye

Figure 35.4 The cells of the retina are arranged in distinct layers (75x).

Inside of eye

Ganglion Cells Eye

Vitreous humor Nerve fibers Ganglion cells

Bipolar neurons

Nuclei of rods and cones

Receptor ends of rods and cones Pigmented epithelium

Outside of eye

OPTIONAL ACTIVITY

u se an ophthalmoscope to examine the interior of your laboratory partner's eye. This instrument consists of a set of lenses held in a rotating disk, a light source, and some mirrors that reflect the light into the test subject's eye.

The examination should be conducted in a dimly lighted room. Have your partner seated and staring straight ahead at eye level. Move the rotating disk of the ophthalmoscope so that the O appears in the lens selection window. Hold the instrument in your right hand with the end of your index finger on the rotating disk (fig. 35.5). Direct the light at a slight angle from a distance of about 15 cm into the subject's right eye. The light beam should pass along the inner edge of the pupil. Look through the instrument and you should see a reddish, circular area—the interior of the eye. Rotate the disk of lenses to higher values until sharp focus is achieved.

Move the ophthalmoscope to within about 5 cm of the eye being examined being very careful that the instrument does not touch the eye, and again rotate the lenses to sharpen the focus (fig. 35.6). Locate the optic disk and the blood vessels that pass through it. Also locate the yellowish macula lutea by having your partner stare directly into the light of the instrument (fig. 35.7).

Examine the subject's iris by viewing it from the side and by using a lens with a +15 or +20 value.

Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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