The oculomotor nerve, also known as the third cranial nerve, cranial nerve III, or simply CN III, is a cranial nerve that enters the orbit through the superior orbital fissure and innervates extraocular muscles that enable most movements of the eye and that raise the eyelid. The nerve also contains fibers that innervate the intrinsic eye muscles that enable pupillary constriction and accommodation. The oculomotor nerve is derived from the basal plate of the embryonic midbrain. Cranial nerves IV and VI also participate in control of eye movement.
The internal carotid artery is an artery in the neck which supplies the anterior circulation of the brain.
The choroid, also known as the choroidea or choroid coat, is a part of the uvea, the vascular layer of the eye. It contains connective tissues, and lies between the retina and the sclera. The human choroid is thickest at the far extreme rear of the eye, while in the outlying areas it narrows to 0.1 mm. The choroid provides oxygen and nourishment to the outer layers of the retina. Along with the ciliary body and iris, the choroid forms the uveal tract.
The ophthalmic artery (OA) is an artery of the head. It is the first branch of the internal carotid artery distal to the cavernous sinus. Branches of the ophthalmic artery supply all the structures in the orbit around the eye, as well as some structures in the nose, face, and meninges. Occlusion of the ophthalmic artery or its branches can produce sight-threatening conditions.
The central retinal artery branches off the ophthalmic artery, running inferior to the optic nerve within its dural sheath to the eyeball.
The common tendinous ring, also known as the annulus of Zinn, or annular tendon, is a ring of fibrous tissue surrounding the optic nerve at its entrance at the apex of the orbit. It is the common origin of the four recti muscles of the group of extraocular muscles.
The nasociliary nerve is a branch of the ophthalmic nerve (CN V1) (which is in turn a branch of the trigeminal nerve (CN V)). It is intermediate in size between the other two branches of the ophthalmic nerve, the frontal nerve and lacrimal nerve.
The superior ophthalmic vein is a vein of the orbit that drains venous blood from structures of the upper orbit. It is formed by the union of the angular vein, and supraorbital vein. It passes backwards within the orbit alongside the ophthalmic artery, then exits the orbit through the superior orbital fissure to drain into the cavernous sinus.
The long ciliary nerves are 2-3 nerves that arise from the nasociliary nerve (itself a branch of the ophthalmic branch (CN V1) of the trigeminal nerve (CN V)). They enter the eyeball to provide sensory innervation to parts of the eye, and sympathetic visceral motor innervation to the dilator pupillae muscle.
The lacrimal artery is an artery of the orbit. It is a branch of the ophthalmic artery. It accompanies the lacrimal nerve along the upper border of the lateral rectus muscle, travelling forward to reach the lacrimal gland. It supplies the lacrimal gland, two rectus muscles of the eye, the eyelids, and the conjunctiva.
The posterior ethmoidal artery is an artery of the head which arises from the ophthalmic artery to supply the posterior ethmoidal air cells, and the meninges. It is smaller than the anterior ethmoidal artery.
The short ciliary nerves are nerves of the orbit around the eye. They are branches of the ciliary ganglion. They supply parasympathetic and sympathetic nerve fibers to the ciliary muscle, iris, and cornea. Damage to the short ciliary nerve may result in loss of the pupillary light reflex, or mydriasis.
The ciliary arteries are divisible into three groups, the long posterior, short posterior, and the anterior.
The supraorbital artery is a branch of the ophthalmic artery. It passes anteriorly within the orbit to exit the orbit through the supraorbital foramen or notch alongside the supraorbital nerve, splitting into two terminal branches which go on to form anastomoses with arteries of the head.
The long posterior ciliary arteries are arteries of the orbit. There are long posterior ciliary arteries two on each side of the body. They are branches of the ophthalmic artery. They pass forward within the eye to reach the ciliary body where they ramify and anastomose with the anterior ciliary arteries, thus forming the major arterial circle of the iris.The long posterior ciliary arteries contribute arterial supply to the choroid, ciliary body, and iris.
The anterior ciliary arteries are seven arteries in each eye-socket that arise from muscular branches of the ophthalmic artery and supply the conjunctiva, sclera, rectus muscles, and the ciliary body. The arteries end by anastomosing with branches of the long posterior ciliary arteries to form the circulus arteriosus major.
The Orbital Fascia forms the periosteum of the orbit.
The central retinal vein is a vein that drains the retina of the eye. It travels backwards through the centre of the optic nerve accompanied by the central retinal artery before exiting the optic nerve together with the central retinal artery to drain into either the superior ophthalmic vein or the cavernous sinus.
The following outline is provided as an overview of and topical guide to human anatomy:
Major arterial circle of the iris" is a circular artery of the eye formed by anastomoses of the anterior ciliary arteries and long posterior ciliary arteries at the ciliary body. It supplies arterial blood to the iris, ciliary processes of the ciliary body, and anterior choroid.
