Flashcards in Chapter 21 - Special Senses Deck (11):
Which of the following specialized receptors exhibits a large ovoid capsule consisting of many concentric lamellae, each separated by a space containing tissue fluid?
(A) Cold receptors
(B) Pacinian corpuscles
(C) Ruffini endings
(D) Meissner corpuscles
(E) Krause end bulb
B. Pacinian corpuscles are usually macroscopic. Their capsules are composed of several lamellae containing fibroblasts and collagen fibers. The lamellae are separated by sparse amounts of tissue fluid. Pacinian corpuscles respond to vibrations and pressure that distort the lamellae. Meissner corpuscles, responsible for touch, are tapered terminals at the tips of dermal papil lae. Ruffini endings, which are sensitive to mechanical stresses, possess a thin connective tis sue capsule that surrounds a fluid-filled space. Cold receptors are naked nerve endings that respond to temperatures below 25°C to 30°C (see Chapter 21 II B).
Aqueous humor drains from the eye by passing
(A) into the ciliary processes.
(B) from the anterior chamber into the
(C) through the canal of Schlemm.
(D) into the vitreous body.
(E) through the pupil.
C. Aqueous humor exits the eye by passing into the canal of Schlemm. The vitreous body is a refractile gel that fills the chamber of the globe posterior to the lens and is not related to the aqueous humor (see Chapter 21 III D 1).
Which of the following statements is characteristic of the choroid?
(A) It is avascular.
(B) It is the posterior portion of the tunica
(C) It is tightly attached to the sclera.
(D) It contains many melanocytes.
(E) It is not pigmented.
D. The choroid is the vascular tunic of the eye that loosely adheres to the sclera of the tunica fibrosa. It contains many melanocytes, which impart a dark pigment to the eye (see Chapter 21 III C 1).
Communication of the scala vestibuli and scala tympani occurs at the
(A) round window.
(B) oval window.
(D) endolymphatic sac.
(E) inner tunnel.
C. The scala vestibuli and the scala tympani are actually one perilymphatic space separated by the cochlear duct (scala media). The scala vestibuli and tympani communicate with each other at the helicotrema (see Chapter 21 IV C 2 e).
The bony ossicles of the middle ear cavity are arranged in a series bridging the tympanic cavity beginning at the tympanic membrane and ending at the
(A) endolymphatic duct. (B) round window.
(D) oval window.
(E) cochlear duct.
D. The bony ossicles of the middle ear cavity articulate in a series from the tympanic membrane to the oval window (see Chapter 21 IV B).
Which of the following cells in the inner ear are involved in detecting movements ofthe head?
(A) Hair cells in the maculae
(B) Outer pillar cells
(C) Inner pillar cells
(D) Cells of Hensen
(E) Hair cells in the organ of Corti
A. Neuroepithelial hair cells in the maculae of the saccule and the utricle detect linear movement of the head. These cells are connected to the vestibular portion of the acoustic nerve (see Chapter 21 IV C 2).
Rods and cones form synapses with which of
the following cells?
(E) Pigmented epithelium
B. Rods and cones synapse with bipolar cells and horizontal cells (see Chapter 21 III E 3).
Which of the following statements is
characteristic of the cornea?
(A) It represents the anterior portion of the tunica vasculosa.
(B) It is composed of three layers.
(C) It forms the anterior boundary of the
posterior chamber of the eye.
(D) It is devoid of nerve endings.
(E) It is the anterior transparent portion of the tunica fibrosa.
E. The cornea is the transparent anterior portion of the tunica fibrosa, the outer covering of the eye; thus it forms the anterior wall of the anterior chamber of the eye. It is also rich in sensory nerve endings. The sclera is the posterior portion of the tunica fibrosa. The tunica vasculosa (middle coat) is composed of the choroid and ciliary body and the iris (see Chapter 21 III B).
A patient exhibiting a high intraocular pressure in both eyes is symptomatic for
(B) detached retina.
C. High intraocular pressure is a symptom of glaucoma. This condition prohibits the aqueous humor from escaping from the anterior chamber of the eye via the canal of Schlemm. If it is left untreated, a gradual loss of peripheral sight occurs; overtime, blindness results. People with cataract have opacity of the lens that blurs the vision. Conjunctivitis is an inflammation of the conjunctiva of the eye with severe reddening of the sclera and the conjunctival surface of the lids, perhaps with a discharge. This condition may be contagious, and if left untreated, blind ness may occur (see Chapter 21 III D Clinical Consideration).
Aqueous humor is produced by
(A) the corneal epithelium.
(B) the canal of Schlemm.
(C) ciliary epithelium.
(E) ora serrata.
C. The ciliary epithelium that lines the ciliary processes secretes the aqueous humor into the posterior chamber of the eye between the iris and the lens. The aqueous humor then flows through the pupil and into the anterior chamber of the eye and finally leaves the anterior chamber by entering the venous system via the canal of Schlemm (see Chapter 21 III D 1).