Ear and Eye Anatomy

External ear

Consists of the auricle (pinna) and the external acoustic meatus (ear canal)

External acoustic meatus (ear canal)

Mostly cartilaginous

Has a short osseous part in the lateral aspect of the tympanic bulla

Cartilaginous part of ear canal

Makes a right-angle turn and extends towards tympanic membrane

Auricular cartilage

In external ear

Rolled into a tube ventromedially

Funnel-shaped

Helix

Slightly folded medial and lateral margin

Anthelix

Transverse ridge on the internal concave wall at beginning of external acoustic meatus

Tragus

Opposite anthelix, the rostral boundary of the initial ear canal, a quadrangular plate of auricular cartilage

Antitragus

Projects caudally from the tragus and completes the lateral boundary of the ear canal

Thin elongated piece of cartilage

Intertragic incisure

Separates the tragus and antitragus

Marginal cutaneous sac

Pouch formed by an incisure on the lateral portion of the helix

Spine of helix

Angle at proximal end of the border of the medial helix

Medial and lateral crura of the helix

Between the spine of the helix and the tragus

The medial border is formed by two curved portions of cartilage

Pretragic incisure

Separates tragus from the crura of the helix

Orbit

The conical cavity containing the eyeball

Periorbita

The cone-shaped sheath of connective tissue and smooth muscle

Encloses the eyeball and its muscles, vessels, and nerves

Orbital fat may be observed on both sides

Lacrimal gland

Small; lies on the medial side of the orbital ligament within the periorbita

Empties secretions into the conjunctival sac

Levator palpebrae superioris m.

Thin, narrow, and superficial

Begins at the apex of the orbit, extends over the dorsal rectus m., and widens to insert as a flat tendon in the superior eyelid

Innervated by CN3 (oculomotor n.)

Sclera of eye, near equator of eyeball

Where do the seven extrinsic muscles of the eye all insert?

Two obliquus mm., four rectus mm., retractor bulbi m.

What do the seven extrinsic muscles of the eye include?

Dorsal rectus, medial rectus, ventral rectus, and lateral rectus mm.

Course rostrally from a small area of origin around the optic canal and orbital fissure

Diverge and attach to the sclera on an imaginary line encircling the eyeball at the equator

CN3, CN6

Dorsal, medial, and ventral rectus mm. are innervated by ___.

Lateral rectus m. is innervated by ___.

Retractor bulbi m.

In the space between the rectus mm.

Consists of four fascicles, a dorsal and ventral pair, that surround CN2 (optic n.)

CN6

What innervates retractor bulbi m.?

Dorsal oblique m.

On the dorsomedial side of the extraocular mm., dorsal to the medial rectus m.

A narrow muscle that forms a long tendon rostrally

Passes through a groove in the trochlea

CN4

What innervates the dorsal oblique m.?

Trochlea

Cartilaginous plaque attached at the level of the medial angle of the eye to the wall of the orbit

Ventral oblique m.

Arises from the rostral border of the palatine bone at the level of the maxillary foramen

Inserts on the sclera at the insertion of the lateral rectus

Does not arise from the apex of the orbit

CN3

What innervates ventral oblique m.?

Superficial gland of third eyelid

On bulbar conjunctival surface of third eyelid

Bulbus oculi

Fancy word for eyeball

External fibrous coat, vascular coat, internal coat that includes retina

Three layers of bulbus oculi (eyeball)