The ocular orbit and spheno-cavernous syndrome

Question 1

Describe the boundaries of the apex and base of the occular orbit

Answer 1

The apex of the pyramid-shaped bony orbit is the optic foramen, whereas the base (the orbital rim) is formed:

▪ superiorly by the frontal bone,
▪ medially by the frontal process of the maxilla,
▪ inferiorly by the zygomatic process of the maxilla and the zygomatic bone, and
▪ laterally by the zygomatic bone, the frontal process of the zygomatic bone, and the zygomatic process of the frontal bone.

Question 2

What is the significance of the shape of the orbital rim

and what shape is orbit if take a saggital section

Answer 2

Ring like structure so usually breaks in two places , commonly medial and inferior wall giving rise to the notion of blow out fractures

it is pyramidal with an apex and base when seen in saggital sections

Question 3

Describe the borders of the roof or orbit and associated features

Answer 3

The roof ( superior wall ) of the bony orbit is made up of the orbital part of the frontal bone with a small contribution from the sphenoid bone ( Fig. 8.76 ). This thin plate of bone separates the contents of the orbit from the brain in the anterior cranial fossa.

Unique features of the superior wall include:

▪ anteromedially, the trochlear fovea, for the attachment of a pulley through which the superior oblique muscle passes, and the possible intrusion of part of the frontal sinus;
▪ anterolaterally, a depression (the lacrimal fossa) for the orbital part of the lacrimal gland.
Posteriorly, the lesser wing of the sphenoid bone completes the roof.

Question 4

Describe the borders of the medial wall or orbit and associated features

Answer 4

he medial walls of the paired bony orbits are parallel to each other and each consists of four bones—the maxilla, lacrimal, ethmoid, and sphenoid bones ( Fig. 8.76 ).

The largest contributor to the medial wall is the orbital plate of the ethmoid bone. This part of the ethmoid bone contains collections of ethmoidal cells, which are clearly visible in a dried skull.

Also visible, at the junction between the roof and the medial wall, usually associated with the frontoethmoidal suture, are the anterior and posterior ethmoidal foramina . The anterior and posterior ethmoidal nerves and vessels leave the orbit through these openings.

Anterior to the ethmoid bone is the small lacrimal bone, and completing the anterior part of the medial wall is the frontal process of the maxilla. These two bones participate in the formation of the lacrimal groove , which contains the lacrimal sac and is bound by the posterior lacrimal crest (part of the lacrimal bone) and the anterior lacrimal crest (part of the maxilla).

Posterior to the ethmoid bone the medial wall is completed by a small part of the sphenoid bone, which forms a part of the medial wall of the optic canal.

Question 5

describe the borders of the floor of orbit and associated features

Answer 5

The floor ( inferior wall ) of the bony orbit, which is also the roof of the maxillary sinus, consists primarily of the orbital surface of the maxilla ( Fig. 8.76 ), with small contributions from the zygomatic and palatine bones.

Beginning posteriorly and continuing along the lateral boundary of the floor of the bony orbit is the inferior orbital fissure. Beyond the anterior end of the fissure the zygomatic bone completes the floor of the bony orbit.

Posteriorly, the orbital process of the palatine bone makes a small contribution to the floor of the bony orbit near the junction of the maxilla, ethmoid, and sphenoid bones.

Question 6

Describe the borders of the lateral wall of orbit and associated features

Answer 6

The lateral wall of the bony orbit consists of contributions from two bones—anteriorly, the zygomatic bone and posteriorly, the greater wing of the sphenoid bone

Question 7

what forms the zygomatic arch (posterior to anterior)

Answer 7

1. zygomatic process of temporal bone
2. temporal process zygomatic bone
   3.