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Short Posterior Ciliary Arteries
The short posterior ciliary arteries are a number of branches of the ophthalmic artery. They pass forward with the optic nerve to reach the eyeball, piercing the sclera around the entry of the optic nerve into the eyeball. Anatomy The number of short posterior ciliary arteries varies between individuals; one or more short posterior ciliary arteries initially branch off the ophthalmic artery, subsequently dividing to form up to 20 short posterior ciliary arteries. Origin The short posterior ciliary arteries branch off the ophthalmic artery as it crosses the optic nerve medially. Course and relations About 7 short posterior ciliary arteries accompany the optic nerve, passing anterior-ward to reach the posterior part of the eyeball, where they divide into 15-20 branches and pierce the sclera around the entrance of the optic nerve. Distribution The short posterior ciliary arteries contribute arterial supply to the choroid, ciliary processes, optic disc, the outer retina, and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sclera
The sclera, also known as the white of the eye or, in older literature, as the tunica albuginea oculi, is the opaque, fibrous, protective outer layer of the eye containing mainly collagen and some crucial elastic fiber. In the development of the embryo, the sclera is derived from the neural crest. In children, it is thinner and shows some of the underlying pigment, appearing slightly blue. In the elderly, fatty deposits on the sclera can make it appear slightly yellow. People with dark skin can have naturally darkened sclerae, the result of melanin pigmentation. In humans, and some other vertebrates, the whole sclera is white or pale, contrasting with the coloured iris (anatomy), iris. The cooperative eye hypothesis suggests that the pale sclera evolved as a method of nonverbal communication that makes it easier for one individual to identify where another individual is looking. Other mammals with white or pale sclera include chimpanzees, many orangutans, some gorillas, and bon ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ophthalmic Artery
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. Structure The ophthalmic artery emerges from the internal carotid artery. This is usually just after the internal carotid artery emerges from the cavernous sinus. In some cases, the ophthalmic artery branches just before the internal carotid exits the carotid sinus. The ophthalmic artery emerges along the medial side of the anterior clinoid process. It runs anteriorly, passing through the optic canal inferolaterally to the optic nerve. It can also pass superiorly to the optic nerve in a minority of cases. In the posterior third of the cone of the orbit, the ophthalmic artery turns sharply and med ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vorticose Veins
The vorticose veins, referred to clinically as the vortex veins, are veins that drain the choroid of the eye. There are usually 4-5 vorticose veins in each eye, with at least one vorticose vein per each quadrant of the eye. Vorticose veins drain into the superior ophthalmic vein, and inferior ophthalmic vein. Vorticose veins are an important ophthalmoscopic landmark. Structure Course and relations Vorticose veins exit the eyeball 6 mm posterior to its equator. Fate Upper vortex veins empty into the superior ophthalmic vein 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 a ..., and lower vortex veins empty into the inferior ophthalmic vein. Variation The number of vorticose veins is known to vary from 4 to 8, with about 65% of the normal population having 4 or 5 with ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Choroid
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 (at 0.2 mm), 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 structure of the choroid is generally divided into four layers (classified in order of furthest away from the retina to closest): *Haller's layer – outermost layer of the choroid consisting of larger diameter blood vessels; * Sattler's layer – layer of medium diameter blood vessels; * Choriocapillaris – layer of capillaries; and * Bruch's membrane (synonyms: Lamina basalis, Complexus basalis, Lamina vitra) – innermost layer of the choroid. Blood supply There are two circulations of the eye: ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ciliary Process
In the anatomy of the eye, the ciliary processes are formed by the inward folding of the various layers of the choroid, viz. the choroid proper and the lamina basalis, and are received between corresponding foldings of the suspensory ligament of the lens. Anatomy They are arranged in a circle, and form a sort of frill behind the iris, around the margin of the lens. They vary from sixty to eighty in number, lie side by side, and may be divided into large and small; the former are about 2.5 mm. in length, and the latter, consisting of about one-third of the entire number, are situated in spaces between them, but without regular arrangement. They are attached by their periphery to three or four of the ridges of the orbiculus ciliaris, and are continuous with the layers of the choroid: their opposite extremities are free and rounded, and are directed toward the posterior chamber of the eyeball and circumference of the lens. In front, they are continuous with the periph ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Optic Nerve
In neuroanatomy, the optic nerve, also known as the second cranial nerve, cranial nerve II, or simply CN II, is a paired cranial nerve that transmits visual system, visual information from the retina to the brain. In humans, the optic nerve is derived from optic stalks during the seventh week of development and is composed of retinal ganglion cell axons and glial cells; it extends from the optic disc to the optic chiasma and continues as the optic tract to the lateral geniculate nucleus, Pretectal area, pretectal nuclei, and superior colliculus. Structure The optic nerve has been classified as the second of twelve paired cranial nerves, but it is technically a myelinated tract of the central nervous system, rather than a classical nerve of the peripheral nervous system because it is derived from an out-pouching of the diencephalon (optic stalks) during embryonic development. As a consequence, the fibers of the optic nerve are covered with myelin produced by oligodendrocytes, r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Choroid
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 (at 0.2 mm), 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 structure of the choroid is generally divided into four layers (classified in order of furthest away from the retina to closest): *Haller's layer – outermost layer of the choroid consisting of larger diameter blood vessels; * Sattler's layer – layer of medium diameter blood vessels; * Choriocapillaris – layer of capillaries; and * Bruch's membrane (synonyms: Lamina basalis, Complexus basalis, Lamina vitra) – innermost layer of the choroid. Blood supply There are two circulations of the eye: ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Optic Disc
The optic disc or optic nerve head is the point of exit for ganglion cell axons leaving the eye. Because there are no rods or cones overlying the optic disc, it corresponds to a small blind spot in each eye. The ganglion cell axons form the optic nerve after they leave the eye. The optic disc represents the beginning of the optic nerve and is the point where the axons of retinal ganglion cells come together. The optic disc in a normal human eye carries 1–1.2 million afferent nerve fibers from the eye toward the brain. The optic disc is also the entry point for the major arteries that supply the retina with blood, and the exit point for the veins from the retina. Structure The optic disc is located 3 to 4 mm to the nasal side of the fovea. It is a vertical oval, with average dimensions of 1.76mm horizontally by 1.92mm vertically. There is a central depression, of variable size, called the optic cup. This depression can be a variety of shapes from a shallow indent ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Retina
The retina (; or retinas) is the innermost, photosensitivity, light-sensitive layer of tissue (biology), tissue of the eye of most vertebrates and some Mollusca, molluscs. The optics of the eye create a focus (optics), focused two-dimensional image of the visual world on the retina, which then processes that image within the retina and sends nerve impulses along the optic nerve to the visual cortex to create visual perception. The retina serves a function which is in many ways analogous to that of the photographic film, film or image sensor in a camera. The neural retina consists of several layers of neurons interconnected by Chemical synapse, synapses and is supported by an outer layer of pigmented epithelial cells. The primary light-sensing cells in the retina are the photoreceptor cells, which are of two types: rod cell, rods and cone cell, cones. Rods function mainly in dim light and provide monochromatic vision. Cones function in well-lit conditions and are responsible fo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bruch's Membrane
Bruch's membrane or lamina vitrea is the innermost layer of the choroid of the eye. It is also called the ''vitreous lamina'' or ''Membrane vitriae'', because of its glassy microscopic appearance. It is 2–4 μm thick. Anatomy Structure Bruch's membrane consists of five layers (from inside to outside): #the basement membrane of the retinal pigment epithelium #the inner collagenous zone #a central band of elastic fibers #the outer collagenous zone #the basement membrane of the choriocapillaris Development The membrane grows thicker with age. With age, lipid-containing extracellular deposits may accumulate between the membrane and the basal lamina of the retinal pigmental epithelium, impairing exchange of solutes and contributing to age-related pathology. Embryology Bruch's membrane is present by midterm in fetal development as an elastic sheet. Function The membrane is involved in the regulation of fluid and solute passage from the choroid to the retina. Pathology ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Common Tendinous Ring
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. It can be used to divide the regions of the superior orbital fissure. The arteries surrounding the optic nerve form a vascular structure known as the circle of Zinn-Haller, or sometimes as the ''circle of Zinn''. The following structures pass through the tendinous ring (superior to inferior): * Superior division of the oculomotor nerve (CNIII) * Nasociliary nerve (branch of ophthalmic nerve) * Inferior division of the oculomotor nerve (CNIII) * Abducens nerve The abducens nerve or abducent nerve, also known as the sixth cranial nerve, cranial nerve VI, or simply CN VI, is a cranial nerve in humans and various other animals that controls the movement of the lateral rectus muscle, one of the extraocula ... (CNVI) ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
