Gross Anatomy & Human Anatomy

Flashcards covering orbit contents, extraocular muscles, cranial nerves, facial muscles, and vascular structures.

Orbit Roof

Separates orbital contents from frontal lobes of brain. Formed by orbital plate of frontal bone.

Orbit Floor

Orbital surfaces of maxilla and zygomatic bone and to small extend orbital process of palatine. Very thin, can be damaged in blow-out fracture causing eye to sink into maxillary sinus.

Medial Wall Orbit

Very thin—delicate. Formed by frontal process of maxilla, Lacrimal bone, ethmoid and small part of body of sphenoid

Lateral Wall Orbit

Orbital process of zygomatic bone and orbital surface of greater wing of sphenoid.

Posterior Wall Orbit

Primarily sphenoid bone

Inferior Oblique Origin

Maxilla, anterior part of floor of orbit

Inferior Oblique Insertion

Posterior lateral aspect of sclera

Inferior Oblique Action

Elevates and abducts eyeball to look superolatrally, extorsion, up and out

Inferior Oblique Innervation

CN III

Superior Oblique Origin

Body of Sphenoid

Superior Oblique Insertion

Posterior and lateral sclera

Superior Oblique Action

Depresses and abducts eyeball to look inferolaterally, intorsion

Superior Oblique Innervation

Trochlear (IV)

Superior Rectus Origin

Common annular tendon

Superior Rectus Insertion

Superior part of sclera

Superior Rectus Action

Elevates and adducts eyeball to look superomedially, intorsion (medial rotation to align both eyes)

Superior Rectus Innervation

CN III, Oculomotor

Medial Rectus Origin

Common annular tendon

Medial Rectus Insertion

Medial sclera

Medial Rectus Action

Adducts eyeball

Medial Rectus Innervation

CN III

Inferior Rectus Origin

Common annular tendon

Inferior Rectus Insertion

Inferior part of sclera

Inferior Rectus Action

Depresses and adducts eyeball to look inferomedially, extorsion (lateral rotation to align both eyes)

Inferior Rectus Innervation

CN III

Lateral Rectus Origin

Common annular tendon

Lateral Rectus Insertion

Lateral surface of sclera

Lateral Rectus Action

Abducts eyeball

Lateral Rectus Innervation

Abducens (VI)

Levator Palpebrae Superioris Origin

The levator palpebrae superioris originates from the lesser wing of the sphenoid bone, just above the optic canal.

Levator Palpebrae Superioris Insertion

It inserts into the skin and fibrous tissue of the upper eyelid.

Levator Palpebrae Superioris Action

Its primary action is to elevate the upper eyelid, allowing the eye to open.

Levator Palpebrae Superioris Innervation

The levator palpebrae superioris is innervated by the oculomotor nerve (cranial nerve III).

Optic Nerve Function

Sensory nerve of vision; travels through optic canal; surrounded by meninges and central artery to retina

Optic Nerve Pathway

Retina -> optic canal in sphenoid bone -> optic chiasm -> optic tracts

Oculomotor Nerve Function

Motor to: superior rectus, medial rectus, inferior rectus, inferior oblique, levator palpebrae. Parasympathetic to ciliary ganglion → sphincter pupillae (pupil constriction) and ciliary muscle (accommodation).

Oculomotor Nerve Origin

The oculomotor nerve originates from the midbrain, specifically from the oculomotor nucleus.

Oculomotor Nerve Pathway

Exits brainstem at the interpeduncular fossa, travels through the cavernous sinus, and enters the orbit through the superior orbital fissure.

Trochlear Nerve Function

Motor to superior oblique

Trochlear Nerve Origin

Arises from the dorsal aspect of the midbrain, just below the inferior colliculus

Trochlear Nerve Pathway

Wraps around the midbrain, passes through the lateral wall of the cavernous sinus, and enters the orbit via the superior orbital fissure.

Abducent Nerve Function

Motor to lateral rectus

Abducent Nerve Origin

Arises from the abducens nucleus in the pons, near the floor of the fourth ventricle.

Abducent Nerve Pathway

Emerges from the pontomedullary junction, pierces the dura mater to enter dorello’s canal, passes through the cavernous sinus, and enters the orbit via the superior orbital fissure.

Frontal Nerve Function

Ophthalmic division of the trigeminal , V1; purely sensory to forehead/scalp

Frontal Nerve Origin

The frontal nerve is the largest branch of the ophthalmic division (V₁) of the trigeminal nerve.

Frontal Nerve Pathway

Enters the orbit via the superior orbital fissure and travels forward between the levator palpebrae superioris and the roof of the orbit. Divides into supraorbital and supratrochlear nerves.

Supraorbital Nerve Function

A terminal branch of the frontal nerve, from CN V₁ – ophthalmic division of the trigeminal nerve; sensory only.

Supraorbital Nerve Origin

Arises from the frontal nerve within the orbit.

Supraorbital Nerve Pathway

Travels anteriorly within the orbit, exits the orbit through the supraorbital foramen or notch in the frontal bone, and ascends onto the forehead and scalp.

Ophthalmic Artery Function

From internal carotid passes through optic canal; Supraorbital and supratrochlear branches: upper eyelid, forehead, scalp

Ophthalmic Artery Origin

Arises from the internal carotid artery just after it emerges from the cavernous sinus, near the optic canal.

Ophthalmic Artery Pathway

Passes through the optic canal, inferolateral to the optic nerve and travels medially along the orbital wall.

Supraorbital Artery Function

Travels with the supraorbital nerve, exits the supraorbital foramen, and supplies the forehead and scalp.

Supraorbital Artery Origin

Arises from the ophthalmic artery within the orbit.

Supraorbital Artery Pathway

Travels anteriorly alongside the supraorbital nerve, passes through the supraorbital foramen or notch in the frontal bone to exit the orbit and ascends onto the forehead beneath the frontalis muscle.

Parotid Gland

Largest paired salivary gland; Location: Side of face, in front of ear

Parotid Duct

Emerges anteriorly, crosses masseter, pierces buccal fat pad and buccinator, opens into oral vestibule opposite 2nd upper molar

Parotid Capsule

Formed by splitting of deep cervical fascia. Infection/inflammation increases pressure, can compress facial nerve branches causing facial muscle paralysis

SCALP Layers

S—skin, C—connective tissue, A—Aponeurosis and muscle, L-- Loose connective tissue, P—Periosteum/pericranium

Buccinator Origin

Pterygomandibular raphe, alveolar margins (lateral to molar teeth) of maxilla and mandible in regions of molars.

Buccinator Insertion

Fibers blend with orbicularis oris

Buccinator Action

Aids in chewing by maintaining food between molars; involved in sucking and blowing air

Buccinator Innervation

Facial nerve (CN VII) — specifically the buccal branch.

Orbicularis Oculi Action

Closes the eyelids: Palpebral (gentle closure), Orbital (forceful closure), Lacrimal (aid tear drainage)

Orbicularis Oculi Innervation

Facial nerve (CN VII) – temporal and zygomatic branches

Levator Labii Superioris Action

Elevates the upper lip, contributing to expressions like disgust or sadness

Levator Labii Superioris Innervation

Facial nerve (CN VII) – buccal branch

Zygomaticus Major Action

Elevates and draws the corner of the mouth laterally, as in smiling or laughing

Zygomaticus Major Innervation

Facial nerve (CN VII) – zygomatic and buccal branches

Orbicularis Oris Action

Closes and protrudes the lips (e.g., puckering, kissing, speech)

Orbicularis Oris Innervation

Facial nerve (CN VII) – buccal and mandibular branches

Depressor Anguli Oris Action

Pulls the angle of the mouth downward, as in frowning or sadness

Depressor Anguli Oris Innervation

Facial nerve (CN VII) – mandibular branch

Occipitofrontalis Action

Frontalis (Raises eyebrows and wrinkles forehead), Occipitalis (Retracts the scalp)

Occipitofrontalis Innervation

Facial nerve (CN VII) – temporal branch (frontalis), posterior auricular branch (occipitalis)

Facial Nerve Branches

Temporal, Zygomatic, Buccal, Mandibular, Cervical. Mnemonic: To Zanzibar By Motor Car

Trigeminal Nerve Divisions

Ophthalmic (V1), Maxillary (V2), Mandibular (V3)

Facial Artery Branches

Inferior labial artery, Superior labial artery, Lateral nasal artery, Angular artery

Superficial Temporal Artery Branches

Transverse facial artery, Frontal branch, Parietal branch, Auricular branches