In anatomy, the orbit is the cavity or socket of the skull in which the eye and its appendages are situated. "Orbit" can refer to the bony socket, or it can also be used to imply the contents. In the adult human, the volume of the orbit is 30 millilitres, of which the eye occupies 6.5 ml. The orbital contents comprise the eye, the orbital and retrobulbar fascia, extraocular muscles, cranial nerves II, III, IV, V, and VI, blood vessels, fat, the lacrimal gland with its sac and duct, the eyelids, medial and lateral palpebral ligaments, check ligaments, the suspensory ligament, septum, ciliary ganglion and short ciliary nerves.
The middle meningeal artery is typically the third branch of the first portion of the maxillary artery, one of the two terminal branches of the external carotid artery. After branching off the maxillary artery in the infratemporal fossa, it runs through the foramen spinosum to supply the dura mater the outer meningeal layer, and the calvaria. The middle meningeal artery is the largest of the three (paired) arteries that supply the meninges, the others being the anterior meningeal artery and the posterior meningeal artery.
In mammalian anatomy, the cribriform plate, horizontal lamina or lamina cribrosa of the ethmoid bone is received into the ethmoidal notch of the frontal bone and roofs in the nasal cavities.
The maxillary nerve (V2) is one of the three branches or divisions of the trigeminal nerve, the fifth (CN V) cranial nerve. It comprises the principal functions of sensation from the maxilla, nasal cavity, sinuses, the palate and subsequently that of the mid-face, and is intermediate, both in position and size, between the ophthalmic nerve and the mandibular nerve.
The supraorbital foramen, is a bony elongated opening located above the orbit and under the forehead. The supraorbital foramen lies directly under the eyebrow. Sometimes this foramen is incomplete and is then known as the supraorbital notch.
The greater wing of the sphenoid bone, or alisphenoid, is a bony process of the sphenoid bone; there is one on each side, extending from the side of the body of the sphenoid and curving upward, laterally, and backward.
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, end in sharp points [Fig. 1].
The lateral wall and the floor of the orbit are separated posteriorly by the inferior orbital fissure which transmits the zygomatic branch of the maxillary nerve and the ascending branches from the pterygopalatine ganglion. The infraorbital vessels are found in the inferior orbital fissure, and travel down the infraorbital groove into the infraorbital canal and exit through the infraorbital foramen. Inferior division of ophthalmic vein passes through the inferior orbital fissure.
The anterior ethmoidal foramen is a small opening in the ethmoid bone in the skull.
The optic foramen is the opening to the optic canal. The canal is located in the sphenoid bone; it is bounded medially by the body of the sphenoid and laterally by the lesser wing of the sphenoid.
In human anatomy, the infraorbital foramen is an opening in the maxillary bone of the skull located below the infraorbital margin of the orbit. It transmits the infraorbital artery and vein, and the infraorbital nerve, a branch of the maxillary nerve. It is typically 6.10 to 10.9 mm from the infraorbital margin.
The middle cranial 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 fossa by the clivus and the petrous crest.
The anterior cranial fossa is a depression in the floor of the cranial base which houses the projecting frontal lobes of the brain. It is formed by the orbital plates of the frontal, the cribriform plate of the ethmoid, and the small wings and front part of the body of the sphenoid; it is limited behind by the posterior borders of the small wings of the sphenoid and by the anterior margin of the chiasmatic groove. The lesser wings of the sphenoid separate the anterior and middle fossae.
The infratemporal fossa is an irregularly shaped cavity, situated below and medial to the zygomatic arch. It is not fully enclosed by bone in all directions, and it contains superficial muscles that are visible during dissection after removing skin and fascia: namely, the lower part of the temporalis muscle, the lateral pterygoid, and the medial pterygoid.
In the sphenoid bone, the posterior border, smooth and rounded, is received into the lateral fissure of the brain; the medial end of this border forms the anterior clinoid process, which gives attachment to the tentorium cerebelli; it is sometimes joined to the middle clinoid process by a spicule of bone, and when this occurs the termination of the groove for the internal carotid artery is converted into a foramen (carotico-clinoid).
Not to be confused with the inferior orbital fissure, which is just lateral to the infraorbital groove.
The infraorbital nerve is a branch of the maxillary nerve, itself a branch of the trigeminal nerve. It travels through the orbit and enters the infraorbital canal to exit onto the face through the infraorbital foramen. It provides sensory innervation to the skin and mucous membranes around the middle of the face.
The base of skull, also known as the cranial base or the cranial floor, is the most inferior area of the skull. It is composed of the endocranium and the lower parts of the skull roof.
The following outline is provided as an overview of and topical guide to human anatomy:
The infraorbital vein arises on the face by the union of several tributaries. Accompanied by the infraorbital artery and the infraorbital nerve, it passes posteriorly through the infraorbital foramen, infraorbital canal, and infraorbital groove. It drains through the inferior orbital fissure into the pterygoid venous plexus. It receives tributaries from structures that lie close to the floor of the orbit and communicates with the inferior ophthalmic vein.
