Fundamentals of Anatomy and Physiology

264 Chapter 11

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Papillae
Taste
buds
Sensory
nerve
fiber^
Connective
tissue
(B)
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(E)
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Taste cell

Taste pore

Supporting

cell

Taste cell cilium

Epithelium

of tongue

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Figure 11- 9 (A) Taste buds on the surface of the tongue are associated with elevations called papillae. (B) A taste bud contains
taste cells with an opening called the taste pore at its free surface. Colored sections indicate common patterns of taste rec eptors:
(C) sweet, (D) sour, (E) salt, and (F) bitter.
inner surface of the eye, and maintains ocular pressure. It is
produced by the ciliary body. The posterior com-partment
of the eye is filled with vitreous (VIT-ree-us) humor. It
too helps to maintain ocular pressure, refracts or bends
light, and holds the retina and lens in place.
The retina is the innermost layer of the eye and con-
tains the photosensitive cells (Figure 11-11). The retina has
a pigmented epithelial layer that helps keep light from
being reflected back into the eye. The sensory layer is made
up of the rods and cones. There are more rods than cones in
this layer. Rods are quite sensitive to light and function in
dim light but do not produce color vi-sion. These are the
cones that produce color and they
require lots of light. Three different types of cones are
sensitive to red, green, or blue. Combinations of these
cones produce all the other colors we see.
The rod and cone cells synapse with the bipolar cells
of the retina. The bipolar cells synapse with ganglia cells
whose axons form the optic nerve. Eventually, the fibers of
the optic nerve reach the thalamus of the brain and synapse
at its posterior portion and enter as optic radia-tions to the
visual cortex of the occipital lobe of the cere-brum for
interpretation.
The yellowish spot in the center of the retina is called
the macula lutea. In its center is a depression called the
fovea centralis. This region produces the sharpest vision,