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Orbit (anatomy)
 
 
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In anatomy
Anatomy

Anatomy is a branch of biology that is the consideration of the body plan. It is a general term that includes human anatomy, animal anatomy and plant anatomy ....
, the orbital bone is the cavity or socket of the skull
Skull

The skull is a bone structure found in the head of many animals. The skull supports the structures of the face and protects the head against injury....
 in which the eye
Eye

Eyes are Organ that detect light, and send signals along the optic nerve to the visual system and other areas of the brain. Complex optical systems with resolving power have come in ten fundamentally different forms, and 96% of animal species possess a complex optical system....
 and its appendages
Adnexa

In anatomy, adnexa refers to the Appendage of an organ. ...
 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.

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.






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In anatomy
Anatomy

Anatomy is a branch of biology that is the consideration of the body plan. It is a general term that includes human anatomy, animal anatomy and plant anatomy ....
, the orbital bone is the cavity or socket of the skull
Skull

The skull is a bone structure found in the head of many animals. The skull supports the structures of the face and protects the head against injury....
 in which the eye
Eye

Eyes are Organ that detect light, and send signals along the optic nerve to the visual system and other areas of the brain. Complex optical systems with resolving power have come in ten fundamentally different forms, and 96% of animal species possess a complex optical system....
 and its appendages
Adnexa

In anatomy, adnexa refers to the Appendage of an organ. ...
 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
Superior orbital fissure

The superior orbital fissure is a foramen in the skull, although strictly it is more of a cleft, lying between the Small wings of the sphenoid and Great wings of the sphenoid of the sphenoid bone....
 and contains the optic canal which communicates with middle cranial fossa
Middle cranial fossa

The middle fossa, deeper than the anterior cranial fossa, is narrow medially and widens laterally to the sides of the skull. It is separated from the posterior cranial fossa by the Clivus and the petrous crest....
.

The roof (superior wall) is formed by the orbital plate frontal bone
Frontal bone

The frontal bone is a bone in the human skull that resembles a Cockle in form, and consists of two portions:* a vertical portion, the squama frontalis, corresponding with the region of the forehead....
 and the lesser wing of sphenoid
Sphenoid

Sphenoid may refer to:* In anatomy, the sphenoid bone* In geometry, a tetrahedron with mirror symmetry...
. 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
Maxilla

The maxilla is a fusion of two bones along the palate fissure that form the upper jaw. This is similar to the mandible, which is also a fusion of two halves at the mental symphysis....
, the orbital surface of zygomatic bone
Zygomatic bone

The zygomatic bone is a paired bone of the human skull. It articulates with the maxilla, the temporal bone, the sphenoid bone and the frontal bone....
 and the orbital process of palatine bone
Palatine bone

The palatine bone is a bone in many species of the animal kingdom, commonly termed the palatum ....
. Medially near the orbital margin is located the groove for nasolacrimal duct
Nasolacrimal duct

The nasolacrimal duct carries tears from the lacrimal sac into the nasal cavity. Excess tears flow through nasolacrimal duct which opens in the nose....
. 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
Inferior orbital fissure

The lateral wall and the floor of the Orbit are separated posteriorly by the inferior orbital fissure which transmits the maxillary nerve and its zygomatic branch, and the ascending branches from the sphenopalatine ganglion....
, which connects the orbit to pterygopalatine
Pterygopalatine fossa

The pterygopalatine fossa is a fossa in the skull. It is the indented area medial to the pterygomaxillary fissure leading into the sphenopalatine foramen....
 and infratemporal fossa
Infratemporal fossa

The infratemporal fossa is an irregularly shaped cavity, situated below and medial to the zygomatic arch....
.

The medial wall is formed by the frontal process of maxilla, lacrimal bone
Lacrimal bone

The lacrimal bone, the smallest and most fragile bone of the face, is situated at the front part of the medial wall of the Orbit . It has two surfaces and four borders....
, 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.

Protrusion

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. Alternately, the eye may make an illusion of protrusion in extreme fear, not from the contraction of smooth muscle of the orbit, but based on the widening of the eyelids and dilation of the pupil (all commanded by the sympathetic nervous system.

Contents

  • Eyeball
  • Fascia
    Fascia

    Fascia , pl. fas?ci?ae , adj. fascial is the soft tissue component of the connective tissue system that permeates the human body....
    s: Orbital
    Orbital

    The term orbital has several meanings:In chemistry and physics:* Atomic orbital* Molecular orbitalIn astronomy and space flight:...
    , Bulbar
  • Extraocular muscles
    Muscles of orbit

    There are six Orbital Muscles; Four of the muscles control the movement of the eye going up and down and side to side. Two of the muscles control the eye to move while the head moves....
     (Levator Palpebrae Superioris, Superior, Inferior, Lateral and Medial Rectus muscles, Superior and Inferior Oblique Muscles)
  • Nerve
    Nerve

    A nerve is an enclosed, cable-like bundle of Peripheral nervous system axons . A nerve provides a common pathway for the electrochemical nerve impulses that are transmitted along each of the axons....
    s: cranial nerves II
    Optic nerve

    The optic nerve, also called cranial nerve II, transmits visual information from the retina to the brain....
    , III
    Oculomotor nerve

    The oculomotor nerve is the third of twelve paired cranial nerves. It controls most of the eye's movements, constriction of the pupil, and maintains an open eyelid....
    , IV
    Trochlear nerve

    The trochlear nerve is a motor nerve that innervates a single muscle: the superior oblique muscle of the eye. An older name is pathetic nerve, which refers to the dejected appearance that is characteristic of patients with fourth nerve palsies....
    , V
    Trigeminal nerve

    The trigeminal nerve is responsible for sensation in the face. Sensory information from the face and body is processed by parallel pathways in the central nervous system....
    , and VI
  • Blood vessel
    Blood vessel

    The blood vessels are the part of the circulatory system that transport blood throughout the body. There are three major types of blood vessels: the artery, which carry the blood away from the heart, the capillary, which enable the actual exchange of water and chemicals between the blood and the tissues; and the veins, which carry blood from...
    s
  • Extraocular Fat
    Fat

    Fats consist of a wide group of compounds that are generally soluble in organic solvents and largely insoluble in water. Chemistry, fats are generally ester of glycerol and fatty acids....
  • Lacrimal gland
    Lacrimal gland

    The lacrimal glands are paired almond-shaped glands, one for each eye, that secrete the aqueous layer of the tears film. They are situated in the upper, outer portion of each Orbit ....
    , Lacrimal sac
    Lacrimal sac

    The lacrimal sac is the upper dilated end of the nasolacrimal duct, and is lodged in a deep groove formed by the lacrimal bone and frontal process of the maxilla....
    , Nasolacrimal duct
    Nasolacrimal duct

    The nasolacrimal duct carries tears from the lacrimal sac into the nasal cavity. Excess tears flow through nasolacrimal duct which opens in the nose....
  • Eyelids
  • Medial and Lateral Palpebral ligaments
  • Medial and Lateral Check ligaments
  • Suspensory ligament
    Suspensory ligament

    Suspensory ligament describes any ligament that supports a body part, especially an organ . Types include:* In humans** Suspensory ligament of the penis...
     of the eyeball
  • Conjunctiva
    Conjunctiva

    The conjunctiva is a clear mucous membrane consisting of cells and underlying basement membrane that covers the sclera and lines the inside of the eyelids....
  • Trochlea
    Trochlea

    Trochlea is a term in anatomy. It refers to a grooved structure reminiscent of a pulley's wheel.Most commonly, trochleae bear the articular surface of saddle joint and other joints:...
  • Orbital septum
    Orbital septum

    The orbital septum is a membranous sheet that acts as the anterior boundary of the Orbit . It extends from the orbital rims to the eyelids.In the upper eyelid it blends with the tendon of the Levator palpebr? superioris, and in the lower eyelid with the Tarsus ....
  • Ciliary ganglion
    Ciliary ganglion

    The ciliary ganglion is a Parasympathetic nervous system ganglion located in the posterior Orbit . It measures 1?2 millimeters in diameter and contains approximately 2,500 neurons....
     and short ciliary nerves


Bones


In humans, seven bones make up the bony orbit:
  • Frontal bone
    Frontal bone

    The frontal bone is a bone in the human skull that resembles a Cockle in form, and consists of two portions:* a vertical portion, the squama frontalis, corresponding with the region of the forehead....
     (Pars orbitalis
    Pars orbitalis

    The orbital or horizontal part of the frontal bone consists of two thin triangular plates, the orbital plates, which form the vaults of the orbits, and are separated from one another by a median gap, the ethmoidal notch....
    )
  • Lacrimal bone
    Lacrimal bone

    The lacrimal bone, the smallest and most fragile bone of the face, is situated at the front part of the medial wall of the Orbit . It has two surfaces and four borders....
  • Ethmoid bone
    Ethmoid bone

    The ethmoid bone is a bone in the skull that separates the nasal cavity from the brain. As such, it is located at the roof of the nose, between the two Orbit s....
     (Lamina papyracea)
  • Zygomatic bone
    Zygomatic bone

    The zygomatic bone is a paired bone of the human skull. It articulates with the maxilla, the temporal bone, the sphenoid bone and the frontal bone....
     (Orbital process of the zygomatic bone
    Orbital process of the zygomatic bone

    The orbital process of the zygomatic bone is a thick, strong plate, projecting backward and medialward from the orbital margin.Its antero-medial surface forms, by its junction with the orbital surface of the maxilla and with the great wing of the sphenoid, part of the floor and lateral wall of the orbit....
    )
  • Maxillary bone (Orbital surface of the body of the maxilla
    Orbital surface of the body of the maxilla

    The orbital surface is smooth and triangular, and forms the greater part of the floor of the Orbit .It is bounded medially by an irregular margin which in front presents a notch, the lacrimal notch; behind this notch the margin articulates with the lacrimal, the lamina papyracea of the ethmoid and the Orbital process of palatine bone of...
    )
  • Palatine bone
    Palatine bone

    The palatine bone is a bone in many species of the animal kingdom, commonly termed the palatum ....
     (Orbital process of palatine bone
    Orbital process of palatine bone

    The orbital process of the palatine bone is placed on a higher level than the sphenoidal, and is directed upward and lateralward from the front of the vertical part, to which it is connected by a constricted neck....
    )
  • Sphenoid bone
    Sphenoid bone

    The sphenoid bone is a bone situated at the base of the skull in front of the temporal bone and basilar part of the occipital bone.The sphenoid bone is one of the seven bones that articulate to form the orbit ....
     (Greater and lesser wings)


Foramina and openings

  1. Optic foramen
    Optic foramen

    The optic foramen is the opening to the optic canal.The superior surface of the sphenoid bone is bounded behind by a ridge, which forms the anterior border of a narrow, transverse groove, the chiasmatic groove , above and behind which lies the optic chiasma; the groove ends on either side in the optic foramen, which transmits the optic...
  2. Superior orbital fissure
    Superior orbital fissure

    The superior orbital fissure is a foramen in the skull, although strictly it is more of a cleft, lying between the Small wings of the sphenoid and Great wings of the sphenoid of the sphenoid bone....
  3. Inferior orbital fissure
    Inferior orbital fissure

    The lateral wall and the floor of the Orbit are separated posteriorly by the inferior orbital fissure which transmits the maxillary nerve and its zygomatic branch, and the ascending branches from the sphenopalatine ganglion....
  4. Anterior ethmoidal foramen
    Anterior ethmoidal foramen

    Lateral to either olfactory groove are the internal openings of the anterior and posterior ethmoidal foramina .The anterior ethmoidal foramen, situated about the middle of the lateral margin of the olfactory groove, transmits the anterior ethmoidal vessels and the anterior ethmoidal nerve; the nerve runs in a groove along the lateral edge o...
  5. Posterior ethmoidal foramen
    Posterior ethmoidal foramen

    Lateral to either olfactory groove are the internal openings of the anterior and posterior ethmoidal foramina .The posterior ethmoidal foramen opens at the back part of this margin under cover of the projecting lamina of the sphenoid, and transmits the posterior ethmoidal vessels and posterior ethmoidal nerve....
  6. Infraorbital foramen
    Infraorbital foramen

    Above the canine fossa is the infraorbital foramen, the end of the infraorbital canal; it transmits the infraorbital artery, vein, and infraorbital nerve....
  7. Supraorbital foramen
    Supraorbital foramen

    The supraorbital foramen is a bony elongated path located above the Orbit and under the forehead. The supraorbital foramen lies directly under the eyebrow....
  8. Naso-lacrimal canal opening
  9. Zygomatic orbital foramen


Additional images


External links

- "Arterial Supply, Orbit"