this ppt cover the anatomy of uveal tract

uvea

1. Uveal tract vassccular coat Azmat jehan

2. Uvea / uveal tract (Latin – Grape) iris   Ciliary body (these two are jointly referred to as anterior uvea ) Choroids (also referred to as posterior uvea ). Uveal tract is markedly vascular. Anatomically the three structures are continuous and disease of the one structure can spread to the other Uvea is firmly attached to the sclera at three sites: anteriorly at the scleral spur at the exit of the vortex veins posteriorly at the optic nerve

3. gross anatomy of the iris IRIS: It is a colored circular diaphragm present b/w lens and cornea, forming anterior part of the uveal tract. It divides the space between cornea and lens into anterior and posterior chambers, communicating with an aperture in the centre called pupil.   GROSS ANATOMY: A) Border Central border is free and ends at the pupillary margin. Periphral border is attached to the anterior surface of ciliry body (Iris root) It may detach from C.B. by blunt trauma ( iridodialysis ) B) Iris Pattern : Anterior surface is uneven and that depression called iris crypts. Collerette is an irregular circle running on anterior surface of iris some distance from the papillary margin. C) Color of Iris:   May be black, brown , blue, green. At birth it is often blue. Permanent color is reached at the age of one year. Color depends upon the amount of pigment in iris stromal cells.  

4. MICROSCOPIC structure of the iris: Stroma : it lies anteriorly and consists of spongy connective tissue, pigment cells,smooth muscles, bloods vessels and nerves. The anterior surface of the iris is devoid of epithelium and has a velvety appearance Pigmented Epithelium : It consist of an anterior layer of flat cells and a posterior layer of pigment cells, cuboidal is shape. It continues posteriorly with the epithelium of ciliary body. Physiological ectropion is normally present at the pupillary margin and it means the coming of posterior pigmented epithelium to the anterior surface of iris forming ruff. Pathological ectropion can occur in conditions like rubeosis iridis .   Normally the blood vessels run radially and almost straight but in rubeosis iridis the vessels are irregular and may form a network.

5. Iris Muscles: Sphincter pupillae muscle: Is present at the pupillary margin and is supplied by parasympathetic fibers (in 3 rd crarial nerve). It causes Miosis . Dilator pupillae muscle: Is arranged radially and runs from pupilliary to cillary boder of the iris. It is supplied by sympathetic fibers and causes Mydriasis . Certain drags may stimulate or inhibit either of the muscle and so may cause mrydriasis or miosis .

6. Blood supply: Is from the major arterial circle that lies in the anterior part of ciliary body.

7. Ciliary body It is the intermediate part of the uveal tract extending from root of the iris to the anterior part of the choroid, i.e. known as ora serrate at a distance of 8mm from limbus . It is a wedge shaped structure and looks triangular on cross section. On the surface; it is divided into pars plicata (ant-2mm) and pars plana (post.4mm).  

8. cillary muscles Consist of 3 parts but the origin of all of them is one i.e. from the scleral spur. It is supplied by para sympathetic fibers from III C.N. Meridional fibers: contraction leads to opening of trabecular meshwork Circlar fibers: contraction leads to relaxation of suspensory ligaments and lens accommodation. Radial fibers: are present between the two group of muscle fibers.

9. Ciliary Processes: about 75 in numbers and arise from pars plicata . ciliary processes are called valleys of Kuhnt . Zonules of lens ( suspensory ligaments of lens) are inserted in these valleys. Each of these ciliary processes are 2 mm in length and 0.5 mm in diameter. The ciliary process lies 0.5 mm from the periphery(equator) of the crystalline lens. The ciliary processes are white whereas the valleys of Kuhnt are dark in colour . – Ciliary Epithelium : It is composed of two layers. inner non pigmented cells. Outer pigmented cells.   Ciliary epithelium help is the formation of aqueous humor from the ciliary processes. Certain drugs like Diamox ’ acts on ciliary epithelium to reduce the production of aq. humor and so to treat glaucoma.

10. Blood vessels in ciliary stroma : Major arterial circle of iris Major arterial circle of iris, formed by the anastomosis of long posterior ciliary arteries and anterior ciliary arteries , is located in ciliary stroma near iris root just in front of circular portion of ciliary muscle. Ciliary stroma also consists of numerous capillaries which are fenestrated and large in size. The capillaries are more in numbers in ciliary processes, making them the most vascular organ of the eye. - Long posterior ciliary artery, a branch of ophthalmic artery, pierce the globe near the optic nerve and run up to ciliary body to form major arterial circle, which is formed with the anastomosis of of anterior ciliary arteries

11. Nerve supply Ciliary muscle is innervated by the autonomic nervous system, parasympathetic postganglionic fibres derived from the oculomotor nerve. The nerve fibres reaches the muscle via short ciliary nerve. The parasympathetic stimulation activates the muscle for contraction, Parasympathetic fibers, coming from the Edinger Westphal nucleus with the oculomotor nerve, are mixed with nerve fibres from the ciliary ganglion and form a plexus in the ciliary muscle. The sensory fibers, coming from the nasociliary branch of the trigeminal nerve, also run in the long ciliary nerve to the ciliary body and terminate in the ciliary muscle. - whereas sympthetic innervation likely has an inhibitory effect to parasympatic fibers,. Sympathetic fibers from the cervical sympathetic trunk, synapse in the superior cervical ganglion, and run to the ciliary muscle via the long ciliary nerve.

12. choroid Thin, soft, brown Extremely vascular Inner surface smooth Outer surface roughened Continuation of pia and arachnoid mater The choroid measures 0.22 to 0.30 mm in thickness in the posterior pole and 0.10 to 0.15 mm anteriorly and peripherally .

13. It is a hight vascular dark colored layers b/w sclera & retina and forms the posterior part of uveal tract (posterior uvea ). It extends from ora serrata to the Optic nerve aperture in the sclera.(optic disc) It consists of 5 layers from sclera side to retina. larmina suprachoridea ( suprachoriodal space). Layer of large blood vessels. Layer of medium sized vessels. . Layer of choriocapillaris Bruch’s membrane. Blood supply: Short and long posterior ciliary anterior supply the choroid and ciliary body. Vortex veins

14. Function of uveal track : Iris: The iris has a shutter mechanism, controlling the amount of light entering the eye, in the interest of clear vision. The iris muscles helps in the dilation and relaxation of pupil as needed. Not only due to amount of light the iris muscles contract and relaxes the pupil but also due to emotional arousals e.g. fear, anxiety etc. The iris also shows the increase in intraocular pressure because when the pressure is increased so it bows out to forward and dilated, which indicates glaucoma. The color of iris shows the amount of pigment present in it. Pigmented iris gives color to the eye, which is a good for cosmetic purposes.

15. The iris has a very important function in the repair of any trauma because it is vascular and therefore can regenerate. Its most important function is sensitiveness because of nerve supply. The texture and pattern of iris is used as a fingerprint because it is different from person to person. Any difference in color of iris of a person shows various pathologies. The iris divides the eye into anterior and posterior chamber. It also helps in the circulation of aqueous humor through pupil into anterior and posterior chamber.

16. Cilliary body: The active secretion of epithelium of cilliary body helps in the formation of aqueous humor. The cilliary body helps in supporting the crystalline lens by means of connective fibers i.e. Zonular fibers Contraction of cilliary muscles releases the tension of Zonular fibers, controlling the size and shape of the lens. This also helps the lens to budge out forward and increase in the power of the lens. Therefore the cilliary muscles directly controls the focusing ability of the eye. Certain drugs can prevent the cilliary body from production of aqueous humor, which is helpful in the treatment of glaucoma.

17. It also maintains the shape of the eye by maintaining the amount of aqueous humor. The cilliary muscles help in focusing the light on retina by changing the focal length of the lens. It provides nourishment to the cornea and lens through aqueous humor. It is also involved in the removal of wastes from the eye through aqueous humor. It regulates the amount of aqueous humor by opening and closing of the trabecular meshwork through it meridional fibers

18. Choroid: It supplies blood and nourishment to the outer layer of retina because it is highly vascularised . It provides oxygen to the eye. Along with the sclera it also provides a tight light environment for the inside the eye, preventing stray light from confusing visual images in the retina .so it Prevents reflection It absorbs light via its pigment layer to minimize glare with in the eye. The bruch’s membrane of Choroid is collagen and elastic fibers providing strength and support to the eye. The melanin of Choroid cells absorbs excess light and helps in keeping the inside of the eye. The Choroid coat of the eye protects the eye from damage . Regulation of IOP through blood flow