Anatomy Lecture 8: The Orbital Region

Study Notes

Orbits are bony cavities that house the eyeballs, associated muscles, nerves, vessels, fat, and lacrimal apparatus.
Eyelids, consisting of two thin, movable folds, guard the orbital opening.

Orbital margin includes:
- Frontal bone (superior margin)
- Zygomatic bone and maxilla (inferior margin)
- Frontal and maxilla (medial margin)
Roof formed by the orbital plate of the frontal bone.
Lateral wall includes zygomatic bone and greater wing of the sphenoid.
Floor formed by maxilla, separating the orbital cavity from the maxillary sinus.
Medial wall comprises frontal process of maxilla, lacrimal bone, and ethmoid.

Supraorbital notch (foramen): Located on superior margin; transmits the supraorbital nerve and vessels.
Infraorbital groove and canal: Situated on the floor; transmits the infraorbital nerve and vessels.
Nasolacrimal canal: Located anteriorly on the medial wall; transmits the nasolacrimal duct.
Inferior orbital fissure: Posteriorly between maxilla and greater wing of sphenoid; transmits maxillary nerve, Zygomatic branch, and inferior ophthalmic vein.
Superior orbital fissure: Posteriorly between greater and lesser wings of the sphenoid; transmits several cranial nerves and superior ophthalmic vein.
Optic canal: Communicates with the middle cranial fossa; transmits optic nerve and ophthalmic artery.
Anterior and Posterior ethmoidal foramen: Located between frontal and ethmoidal bone; transmit anterior and posterior ethmoidal nerves and vessels.
Zygomatic foramen: Found in the zygomatic bone; transmits zygomatic branches.

Extends from nostrils to posterior nasal apertures (choanae), connecting to the nasopharynx.
Nasal vestibule is located just inside the nostrils.
Divided into right and left halves by the nasal septum.

Floor: Composed of the palatine process of maxilla and horizontal plate of palatine bone.
Roof: Formed by nasal and frontal bones anteriorly, cribriform plate of the ethmoid, and body of the sphenoid posteriorly.
Lateral wall: Consists of maxilla, palatine bone, medial pterygoid plate, labyrinth of ethmoid, inferior concha, and lacrimal bone.
Paranasal sinuses connect to nasal cavity via ostia.
Lateral wall features three nasal conchae (superior, middle, inferior) and corresponding meatus below each concha.

Sphenoethmoidal recess: Above the superior concha; opens to sphenoid air sinus.
Superior meatus: Below superior concha; opens to posterior ethmoid sinuses.
Inferior meatus: Receives the nasolacrimal duct's lower end.
Middle meatus: Lies below the middle concha.

Formed by the nasal septum, with upper part made up of ethmoid's vertical plate and vomer.
Septal cartilage forms anterior part; the septum often deviates from midline.

Comprise three paired bones: malleus, incus, and stapes.
Malleus is the largest; features head, neck, handle, anterior, and lateral processes.
Incus has a large body and two processes, articulating with both the malleus and stapes.
Stapes has a head, neck, limbs, and base, connecting to the oval window.