The Special Senses

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Dilute saline solution containing mucus, antibodies, and lysozyme

Blinking spreads the tears toward the medial commissure

Tears enter paired lacrimal canaliculi via the lacrimal puncta

Drain into the nasolacrimal duct

Slide 10

Figure 15.2

Lacrimal gland

Excretory ducts

of lacrimal glands

Lacrimal punctum

Lacrimal canaliculus

Nasolacrimal duct

Inferior meatus

of nasal cavity

Nostril

Lacrimal sac

Slide 11

Extrinsic Eye Muscles

Six straplike extrinsic eye muscles

Originate from the bony orbit

Enable the eye to follow moving objects

Maintain the shape of the eyeball

Four rectus muscles originate from the common tendinous ring; names indicate the movements they promote

Two oblique muscles move the eye in the vertical plane and rotate the eyeball

Slide 12

Figure 15.3a

Inferior rectus

muscle

Inferior oblique

muscle

Superior oblique

muscle

Superior oblique

tendon

Superior rectus

muscle

Lateral rectus

muscle

(a) Lateral view of the right eye

Slide 13

Figure 15.3b

Superior oblique

muscle

Common

tendinous ring

Trochlea

Superior oblique

tendon

Superior rectus

muscle

(b) Superior view of the right eye

Axis at center

of eye

Medial

rectus muscle

Inferior

rectus muscle

Lateral

rectus muscle

Slide 14

Figure 15.3c

(c) Summary of muscle actions and innervating cranial nerves

Lateral rectus

Medial rectus

Superior rectus

Inferior rectus

Inferior oblique

Superior oblique

Moves eye laterally

Moves eye medially

Elevates eye and turns it medially

Depresses eye and turns it medially

Elevates eye and turns it laterally

Depresses eye and turns it laterally

VI (abducens)

III (oculomotor)

III (oculomotor)

III (oculomotor)

III (oculomotor)

IV (trochlear)

Muscle

Action

Controlling

cranial nerve

Slide 15

Structure of the Eyeball

Wall of eyeball contains three layers

Fibrous

Vascular

Sensory

Internal cavity is filled with fluids called humors

The lens separates the internal cavity into anterior and posterior segments (cavities)

Slide 16

Figure 15.4a

Central artery

and vein of