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Orbit (anatomy)
The seven bones which articulate to form the orbit.
yellow = Frontal bone
green = Lacrimal bone
brown = Ethmoid bone
blue = Zygomatic bone
purple = Maxillary bone
aqua = Palatine bone
red = Sphenoid bone
Latin orbitae
Gray's subject #46 188
MeSH Orbit
Dorlands/Elsevier o_05/12594914

In anatomy, the orbital bone is the cavity or socket of the skull in which the eye and its appendages are situated. The frontal bone is a Bone in the Human Skull that resembles a cockleshell in form and consists of two portions a vertical 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. The ethmoid bone (from Greek ethmos, "sieve" is a Bone in the Skull that separates the Nasal cavity from the Brain. The zygomatic bone came from the Latin term zyosislymore meaning malar bone (commonly called "cheek bone" ( malar bone) is a paired bone of the human Skull This article is about the Mammal maxilla For Arthropod maxillae see Mouthparts; for Insect maxillae in particular see Insect mouthparts The palatine bone is a Bone in the Palate (Latin palatum; unrelated to palatium 'palace' from which other senses of Palatine derive The sphenoid bone (from Greek sphenoeides, "wedgelike" is a Bone situated at the base of the Skull in front of the Temporals and basilar Latin ( lingua Latīna, laˈtiːna is an Italic language, historically spoken in Latium and Ancient Rome. Introduction ( classes Long bones body or Diaphysis Medullary canal Medical Subject Headings ( MeSH) is a huge Controlled vocabulary (or metadata system for the purpose of indexing journal articles and books Elsevier, the world's largest Publisher of Medical and Scientific literature, forms part of the Reed Elsevier group Anatomy (from the Greek anatomia, from ana separate apart from and temnein, to cut up cut open is a branch of Biology that is the consideration Eyes are organs that detect Light, and send signals along the Optic nerve to the visual areas of the brain In Anatomy, adnexa refers to the Appendages of an organ Examples of adnexa Adnexa of Eye Extraocular muscles

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. [1]

Contents

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:

The apex lies near the medial end of superior orbital fissure and contain the optic canal which communicates with middle cranial fossa. The superior orbital fissure is a Foramen in the skull although strictly it is more of a cleft lying between the lesser and greater wings of the 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 The middle fossa, deeper than the Anterior cranial fossa, is narrow medially and widens laterally to the sides of the Skull.

The roof (superior wall) is formed by the orbital plate frontal bone and the lesser wing of sphenoid. The frontal bone is a Bone in the Human Skull that resembles a cockleshell in form and consists of two portions a vertical The sphenoid bone (from Greek sphenoeides, "wedgelike" is a Bone situated at the base of the Skull in front of the Temporals and basilar 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. This article is about the Mammal maxilla For Arthropod maxillae see Mouthparts; for Insect maxillae in particular see Insect mouthparts The zygomatic bone came from the Latin term zyosislymore meaning malar bone (commonly called "cheek bone" ( malar bone) is a paired bone of the human Skull The palatine bone is a Bone in the Palate (Latin palatum; unrelated to palatium 'palace' from which other senses of Palatine derive Medially near the orbital margin is located the groove for nasolacrimal duct. The nasolacrimal duct (sometimes called tear ducts) carries Tears from the Lacrimal sac into the Nasal cavity. 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 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 The pterygopalatine fossa is a Fossa in the Skull. It is the indented area medial to the Pterygomaxillary fissure leading into the Sphenopalatine foramen 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, orbital plate of ethmoid and a small part of the body of the sphenoid. 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. The ethmoid bone (from Greek ethmos, "sieve" is a Bone in the Skull that separates the Nasal cavity from the Brain.

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. [2]

Contents

Bones

In humans, seven bones make up the bony orbit:

Foramina and openings

  1. Optic foramen
  2. Superior orbital fissure
  3. Inferior orbital fissure
  4. Anterior ethmoid foramen
  5. Posterior ethmoidal foramen
  6. Infraorbital foramen
  7. Supraorbital foramen
  8. Naso-lacrimal canal opening
  9. Zygomatic orbital foramen

Additional images

The skull from the front. Fascia (făsh'ē-ə pl fas·ci·ae (făsh'ē-ē adj fascial (făsh'ē-əl (from Latin: a band is the Soft tissue component of The corticobulbar (or corticonuclear) tract is a White matter pathway connecting the Cerebral cortex to the Brainstem (the term "bulbar" There are six Orbital Muscles; Four of the muscles control the movement of the eye going up and down and side to side The levator palpebrae superioris (or levator muscle of upper eyelid) is the Muscle in the orbit that elevates the superior (upper Eyelid. The rectus abdominis muscle (commonly known as "abs" is a paired Muscle running vertically on each side of the anterior wall of the human abdomen (and in some other A nerve is an enclosed cable-like bundle of peripheral Axons (the long slender projections of Neurons. Cranial nerves are Nerves that emerge directly from the Brain stem in contrast to Spinal nerves which emerge from segments of the Spinal cord. The optic nerve, also called cranial nerve II, is the Nerve that transmits visual information from the Retina to the Brain. The oculomotor nerve is the third of twelve paired Cranial nerves. The trochlear nerve (the fourth cranial nerve, also called the fourth nerve or simply IV) is a motor nerve (a “somatic efferent” nerve that innervates The trigeminal nerve (the fifth Cranial nerve, also called the fifth nerve or simply V) is responsible for sensation in the face The abducens nerve (the sixth cranial nerve, also called the sixth nerve or simply VI) is a “somatic efferent” nerve that controls the movement of a The blood vessels are part of the Circulatory system and function to transport Blood throughout the body Fats consist of a wide group of compounds that are generally soluble in organic solvents and largely insoluble in water The lacrimal glands are paired almond-shaped Glands, one for each eye that secrete the aqueous layer of the tear film 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 The nasolacrimal duct (sometimes called tear ducts) carries Tears from the Lacrimal sac into the Nasal cavity. An eyelid is a thin fold of skin that covers and protects an Eye. The conjunctiva is a clear membrane that covers the Sclera (white part of the Eye) and lines the inside of the Eyelids It is made of lymphoid tissue The orbital septum ( palpebral ligament) is a membranous sheet that acts as the anterior boundary of the orbit. The ciliary ganglion is a parasympathetic Ganglion located in the posterior orbit. Human beings, humans or man (Origin 1590–1600 L homō man OL hemō the earthly one (see Humus The frontal bone is a Bone in the Human Skull that resembles a cockleshell in form and consists of two portions a vertical The orbital or horizontal part of the Frontal bone ( pars orbitalis) consists of two thin triangular plates the Orbital plates, which form the 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. The ethmoid bone (from Greek ethmos, "sieve" is a Bone in the Skull that separates the Nasal cavity from the Brain. The lateral surface of the labyrinth of the Ethmoid bone is formed of a thin smooth oblong plate the lamina papyracea (or orbital lamina) which covers in the middle The zygomatic bone came from the Latin term zyosislymore meaning malar bone (commonly called "cheek bone" ( malar bone) is a paired bone of the human Skull The orbital process of the Zygomatic bone is a thick strong plate projecting backward and medialward from the orbital margin This article is about the Mammal maxilla For Arthropod maxillae see Mouthparts; for Insect maxillae in particular see Insect mouthparts The orbital surface is smooth and triangular and forms the greater part of the floor of the orbit. The palatine bone is a Bone in the Palate (Latin palatum; unrelated to palatium 'palace' from which other senses of Palatine derive 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 The sphenoid bone (from Greek sphenoeides, "wedgelike" is a Bone situated at the base of the Skull in front of the Temporals and basilar The greater wing of the sphenoid bone, or ali-sphenoid The lesser wings of the Sphenoid or orbito-sphenoids are two thin triangular plates which arise from the upper and anterior parts of the body and projecting lateralward 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 The superior orbital fissure is a Foramen in the skull although strictly it is more of a cleft lying between the lesser and greater wings of the 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 Lateral to either Olfactory groove are the internal openings of the anterior and posterior ethmoidal foramina (or canals Above the Canine fossa is the infraorbital foramen, the end of the Infraorbital canal; it transmits the Infraorbital artery, vein and Infraorbital The supraorbital foramen is a bony elongated path located above the orbit (eye socket and under the forehead The nasolacrimal duct (sometimes called tear ducts) carries Tears from the Lacrimal sac into the Nasal cavity. On the orbital process of the Zygomatic bone are seen the orifices of two canals the zygomatico-orbital foramina.

Medial wall of left orbit.

Dissection showing origins of right ocular muscles, and nerves entering by the superior orbital fissure.

Coronal section of nasal cavities.

Lateral orbit anatomy

Lateral orbit nerves

The orbit in relation to the other skull openings in the dinosaur Massospondylus. Massospondylus (ˌmæsoʊˈspɒndɨləs from Greek, (massōn "longer" and (spondylos "vertebra" is a Genus of prosauropod

References

  1. ^ Duane's Ophthalmology, Chapter 32 Embryology and Anatomy of the Orbit and Lacrimal System . (eds Tasman W, Jaeger EA) Lippincott/Williams & Wilkins, 2007
  2. ^ "eye, human. "Encyclopædia Britannica. 2008. Encyclopædia Britannica 2006 Ultimate Reference Suite DVD 5 Apr. 2008


External links

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