The Orbital Cavity
Introduction:
The orbital cavities are a pair of large bony sockets that contain the eyeball,
their associated muscles, nerves, vessels, fat, and most of the lacrimal apparatus. Each
cavity is pear-shaped and its apex is directed posteriorly, medially, and slightly upwards; the
stalk of the pear lying within the optic canal. The medial wall runs anteroposteriorly parallel
to the sagittal plane; the lateral wall diverges at an angle of about 45 degrees. The seven
individual bones form the orbit namely
● Maxilla
● Palatine
● Zygomatic
● Shenoid
● Frontal
● Ethmoid
● Lacrimal bone
●
Orbital Margins:
The strong orbital margins ( or rim ) is quadrilateral in shape with rounded
corners. In adults the orbital margin is wider than it is high. The supraorbital margins are
formed by the frontal bone, having the sharp lateral two-third and a rounded medial third. At
the junction of the two areas is the supraorbital notch or foramen for the passage of the
supraorbital vessels and nerves. The sharped infraorbital margins are formed laterally by the
zygomatic bone and medically by the maxilla. The lateral margins, the strongest part of the
orbital margin, is formed by the frontal process of the zygomatic bone below and the
zygomatic process of the frontal bone above. The suture between the two bones can be
easily felt in the living subject. The medial margin is formed above by the maxillary process
of the frontal bone and below by the lacrimal crest of the frontal process of the maxilla. The
upper part of the medial margin is indistinct and its lower half is sharp and easily felt.
Walls of the Orbital Cavity:
The walls of the orbital cavity are lined with the periosteum and consist of
a roof, a floor, and a medial and a lateral wall.
The apex of the orbital cavity is at the medial end of the superior orbital
fissure.
Roof
The concave roof of the superior wall is formed by the orbital plate of the
frontal bone to a small extent by the lesser wing of the sphenoid posteriorly. Anteromedially
the roof is invaded by the frontal air sinus. Anterolaterally there is a slight depression, the
lacrimal fossa, for the orbital part of the lacrimal gland. Medial to the supraorbital notch and 4
mm behind the orbital margin is a small depression or spine for the pulley of the superior
oblique muscle.
The roof of the orbit is thin and fragile and in old age portions of the roof
may be absorbed. The roof separates the orbital cavity from the anterior cranial fossa and
the frontal lobe of the cerebral hemisphere.
Floor
The thin floor or inferior wall is formed largely by the orbital plate of the
maxilla, and also by the orbital surface of the zygomatic and the small orbital process of the
Introduction:
The orbital cavities are a pair of large bony sockets that contain the eyeball,
their associated muscles, nerves, vessels, fat, and most of the lacrimal apparatus. Each
cavity is pear-shaped and its apex is directed posteriorly, medially, and slightly upwards; the
stalk of the pear lying within the optic canal. The medial wall runs anteroposteriorly parallel
to the sagittal plane; the lateral wall diverges at an angle of about 45 degrees. The seven
individual bones form the orbit namely
● Maxilla
● Palatine
● Zygomatic
● Shenoid
● Frontal
● Ethmoid
● Lacrimal bone
●
Orbital Margins:
The strong orbital margins ( or rim ) is quadrilateral in shape with rounded
corners. In adults the orbital margin is wider than it is high. The supraorbital margins are
formed by the frontal bone, having the sharp lateral two-third and a rounded medial third. At
the junction of the two areas is the supraorbital notch or foramen for the passage of the
supraorbital vessels and nerves. The sharped infraorbital margins are formed laterally by the
zygomatic bone and medically by the maxilla. The lateral margins, the strongest part of the
orbital margin, is formed by the frontal process of the zygomatic bone below and the
zygomatic process of the frontal bone above. The suture between the two bones can be
easily felt in the living subject. The medial margin is formed above by the maxillary process
of the frontal bone and below by the lacrimal crest of the frontal process of the maxilla. The
upper part of the medial margin is indistinct and its lower half is sharp and easily felt.
Walls of the Orbital Cavity:
The walls of the orbital cavity are lined with the periosteum and consist of
a roof, a floor, and a medial and a lateral wall.
The apex of the orbital cavity is at the medial end of the superior orbital
fissure.
Roof
The concave roof of the superior wall is formed by the orbital plate of the
frontal bone to a small extent by the lesser wing of the sphenoid posteriorly. Anteromedially
the roof is invaded by the frontal air sinus. Anterolaterally there is a slight depression, the
lacrimal fossa, for the orbital part of the lacrimal gland. Medial to the supraorbital notch and 4
mm behind the orbital margin is a small depression or spine for the pulley of the superior
oblique muscle.
The roof of the orbit is thin and fragile and in old age portions of the roof
may be absorbed. The roof separates the orbital cavity from the anterior cranial fossa and
the frontal lobe of the cerebral hemisphere.
Floor
The thin floor or inferior wall is formed largely by the orbital plate of the
maxilla, and also by the orbital surface of the zygomatic and the small orbital process of the
