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md0006 - BASIC HUMAN ANATOMY.pdf - Raems.com

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62. Examples of the adnexa are the:<br />

a. Extrinsic ocular muscles.<br />

b. Eyelids.<br />

c. Lacrimal apparatus.<br />

d. Eyebrow.<br />

e. Optic nerve. (para 11-29)<br />

63. Of the six extrinsic ocular muscles, four are called recti muscles. Two are oblique<br />

muscles. The lateral rectus M. is on the outer side of the eyeball. The superior<br />

rectus M. is above the eyeball. The medial rectus M. is on the inner side of the<br />

eyeball. The inferior rectus M. is below the eyeball. The superior oblique and<br />

inferior oblique muscles approach the eyeball from the medial side. (para 11-29a)<br />

64. Attached to the margins of the orbit are the upper and lower eyelids. These have<br />

special hairs called eyelashes. The inner lining of the eyelids is continuous with<br />

the conjunctiva, a membrane over the anterior surface of the eyeball.<br />

(para 11-29b)<br />

65. In the upper outer corner of the orbit is a lacrimal gland, which secretes a lacrimal<br />

fluid, which is ultimately collected and delivered into the nasal chamber by the<br />

nasolacrimal duct. (para 11-29c)<br />

66. Neurons carry information from the photoreceptors located in the nervous retina.<br />

They leave the eyeball at the blind spot. Passing to the rear of the orbit, the<br />

neurons now belong to the optic nerve (cranial nerve II). The optic nerve enters<br />

the cranial cavity by passing through the optic canal. Beneath the brain, the optic<br />

nerves from both sides join to form the optic chiasma, in which half of the neurons<br />

from each optic nerve cross to the opposite side. From the optic chiasma, the<br />

right and left optic tracts proceed to the brain proper. (para 11-29e)<br />

67. The human ear has two major special sensory functions: hearing (auditory) and<br />

equilibrium (balance). The three parts of the human ear are the external (outer)<br />

ear, the middle ear, and the internal (inner) ear. (para 11-30)<br />

68. The external flap of the ear is called the auricle (pinna). It directs airborne sound<br />

waves into the canal called the external auditory meatus, which extends into the<br />

temporal portion of the skull. (para 11-31)<br />

69. The tympanic membrane is between the external auditory meatus and the middle<br />

ear cavity. On the medial side of the tympanic membrane, there is a space within<br />

the temporal bone called the middle ear cavity. The auditory ossicles are three<br />

very small bones linking the tympanic membrane to the medial wall of the middle<br />

ear cavity. The auditory ossicles respond to a sound stimulus by vibrating<br />

(mechanically oscillating). From the lateral to the medial ends, the names of the<br />

MD0006 11-59

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