Everything about Orbit Anatomy totally explained
In
anatomy, the
orbital bone is the cavity or socket of the
skull in which the
eye and its
appendages are situated.
It can also mean the skin which surrounds the eye of a bird.
In the adult human, the volume of the orbit is 30 ml, of which the eye occupies 6.5 ml.
Definition
The orbits are conical cavities, which open into the midline of the face. Each consists of a base, an apex and four walls.
The base, which opens in the face, has four borders. The following bones take part in their formation:
- 1. Superior margin: frontal bone
- 2. Inferior margin: maxilla and zygomatic
- 3. Medial margin: frontal, lacrimal and maxilla
- 4. Lateral margin: zygomatic and frontal
The apex lies near the medial end of
superior orbital fissure and contain the
optic canal which communicates with
middle cranial fossa.
The roof (superior wall) is formed by the orbital plate
frontal bone and the lesser wing of
sphenoid. The orbital surface presents medially by trochlear fovea and laterally by lacrimal fossa
The floor (inferior wall) is formed by the orbital surface of
maxilla, the orbital surface of
zygomatic bone and the orbital process of
palatine bone. Medially near the orbital margin is located the groove for
nasolacrimal duct. Near the middle of the floor, located infraorbital groove, which leads to the infraorbital foramen. The floor is separated from the lateral wall by
inferior orbital fissure, which connects the orbit to
pterygopalatine and
infratemporal fossa.
The medial wall is formed by the frontal process of maxilla,
lacrimal bone, orbital plate of
ethmoid and a small part of the body of the sphenoid.
The Lateral wall is formed by the orbital process of zygomatic and the orbital plate of greater wing of sphenoid. The bones meet at the zygomaticosphenoid suture. The lateral wall is the thickest wall of the orbit.
Fat cushion
In the orbit, surrounding the eyeball and its muscles, is a layer of fat that helps the eye rotate around a fixed center of rotation. If excess liquid is collected in the fat cushion tissue, the eye may protrude.
Contents
Eyeball
Fascias: Orbital, Bulbar
Extraocular muscles (Levator Palpebrae Superioris, Superior, Inferior, Lateral and Medial Rectus muscles, Superior and Inferior Oblique Muscles)
Nerves: cranial nerves II, III, IV, V, and VI
Blood vessels
Extraocular Fat
Lacrimal gland, Lacrimal sac, Nasolacrimal duct
Eyelids
Medial and Lateral Palpebral ligaments
Medial and Lateral Check ligaments
Suspensory ligament of the eyeball
Conjunctiva
Trochlea
Orbital septum
Ciliary ganglion and short ciliary nerves
Bones
In humans, seven bones make up the bony orbit:
Frontal bone (Pars orbitalis)
Lacrimal bone
Ethmoid bone (Lamina papyracea)
Zygomatic bone (Orbital process of the the zygomatic bone)
Maxillary bone (Orbital surface of the body of the maxilla)
Palatine bone (Orbital process of palatine bone)
Sphenoid bone (Greater and lesser wings)
Foramina and openings
Optic foramen
Superior orbital fissure
Inferior orbital fissure
Anterior ethmoid foramen
Posterior ethmoidal foramen
Infraorbital foramen
Supraorbital foramen
Naso-lacrimal canal opening
Zygomatic orbital foramen
Additional images
Image:Gray190.png|The skull from the front.
Image:Gray192.png|Medial wall of left orbit.
Image:Gray787.png|Dissection showing origins of right ocular muscles, and nerves entering by the superior orbital fissure.
Image:Gray859.png|Coronal section of nasal cavities.
Image:Orbita mensch.jpg
Image:Lateral orbit anatomy 2.jpg|Lateral orbit anatomy
Image:Lateral orbit nerves.jpg|Lateral orbit nerves
Image:Massospondylus Skull Steveoc 86.png|The orbit in relation to the other skull openings in the dinosaur Massospondylus.
Further Information
Get more info on 'Orbit Anatomy'.
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