62.
Examples of the adnexa are the:
a.
Extrinsic ocular muscles.
b.
Eyelids.
c.
Lacrimal apparatus.
d.
Eyebrow.
e.
63.
Of the six extrinsic ocular muscles, four are called recti muscles. Two are oblique
muscles. The lateral rectus M. is on the outer side of the eyeball. The superior
rectus M. is above the eyeball. The medial rectus M. is on the inner side of the
eyeball. The inferior rectus M. is below the eyeball. The superior oblique and
inferior oblique muscles approach the eyeball from the medial side. (para 11-29a)
64.
Attached to the margins of the orbit are the upper and lower eyelids. These have
special hairs called eyelashes. The inner lining of the eyelids is continuous with
the conjunctiva, a membrane over the anterior surface of the eyeball.
65.
In the upper outer corner of the orbit is a lacrimal gland, which secretes a lacrimal
fluid, which is ultimately collected and delivered into the nasal chamber by the
66.
Neurons carry information from the photoreceptors located in the nervous retina.
They leave the eyeball at the blind spot. Passing to the rear of the orbit, the
neurons now belong to the optic nerve (cranial nerve II). The optic nerve enters
the cranial cavity by passing through the optic canal. Beneath the brain, the optic
nerves from both sides join to form the optic chiasma, in which half of the neurons
from each optic nerve cross to the opposite side. From the optic chiasma, the
right and left optic tracts proceed to the brain proper. (para 11-29e)
67.
The human ear has two major special sensory functions: hearing (auditory) and
equilibrium (balance). The three parts of the human ear are the external (outer)
ear, the middle ear, and the internal (inner) ear. (para 11-30)
68.
The external flap of the ear is called the auricle (pinna). It directs airborne sound
waves into the canal called the external auditory meatus, which extends into the
69.
The tympanic membrane is between the external auditory meatus and the middle
ear cavity. On the medial side of the tympanic membrane, there is a space within
the temporal bone called the middle ear cavity. The auditory ossicles are three
very small bones linking the tympanic membrane to the medial wall of the middle
ear cavity. The auditory ossicles respond to a sound stimulus by vibrating
(mechanically oscillating). From the lateral to the medial ends, the names of the
MD0006
11-59