Own choroid. Choroid (choroid) - structure and function

01.04.2020

choroid itself - (choroidea, PNA; chorioidea, BNA; chorioides, JNA) posterior part of the choroid eyeballrich in blood vessels and pigment; S. s. about. prevents light from passing through the sclera ... Big Medical Dictionary

VASCULAR SHEET - eyes (chorioidea), represents the posterior section of the vascular tract and is located posterior to the dentate edge of the retina (oga serrata) to the opening optic nerve (fig. 1). This section of the vascular tract is the largest and embraces ... ... Great medical encyclopedia

VASCULAR SHEET - choroid (chorioidea), connective tissue pigmented membrane of the eye in vertebrates, located between the retinal pigment epithelium and the sclera. It is abundantly permeated with blood vessels supplying the retina with oxygen and nutrition. substances ... Biological encyclopedic dictionary

Membrane of the eye Vascular (Choroid) - the middle shell of the eyeball, located between the retina and the sclera. It contains a large number of blood vessels and large pigment cells that absorb excess light entering the eye, which prevents ... ... Medical terms

VASCULAR EYE - (choroid) the middle shell of the eyeball, located between the retina and the sclera. It contains a large number of blood vessels and large pigment cells that absorb an excessive amount of light entering the eye, which ... ... Explanatory dictionary in medicine

Choroid - The ophthalmic membrane associated with the sclera, which consists mainly of blood vessels and is the main source of nutrition for the eye. The highly pigmented and dark choroid absorbs excess light entering the eye, reducing ... ... The Psychology of Sensations: A Glossary

Choroid - the choroid, the connective tissue membrane of the Eye, located between the retina (see Retina) and the sclera (See Sclera); through it, metabolites and oxygen enter the pigment epithelium and retinal photoreceptors from the blood. S. o. subdivided ... ... Great Soviet Encyclopedia

Choroid - the name attached to the various authorities. This is the name, for example, of the choroid membrane of the eye (Chorioidea) replete with blood vessels, the deeper layer of the brain and spinal cord pia mater, replete with vessels, as well as some ... ... encyclopedic Dictionary F. Brockhaus and I.A. Efron

EYE CONTRUSION - honey. Eye contusion injury when exposed to a blunt blow; account for 33% of the total number of eye injuries leading to blindness and disability. Classification I degree contusion that does not cause visual impairment during recovery II ... ... Handbook of diseases

Iris - human eyes Iris, iris, iris (Latin iris), thin movable diaphragm of the eye in vertebrates with a hole (pupil ... Wikipedia

- (choroidea, PNA; chorioidea, BNA; chorioides, JNA) the posterior part of the choroid of the eyeball, rich in blood vessels and pigment; S. s. about. prevents light from passing through the sclera ... Big Medical Dictionary

VASCULAR SHEET - eyes (chorioidea), represents the posterior part of the vascular tract and is located posterior to the dentate edge of the retina (oga serrata) to the opening of the optic nerve (Fig. 1). This section of the vascular tract is the largest and embraces ... ... Great medical encyclopedia

Choroid (chorioidea), the connective tissue pigmented membrane of the eye in vertebrates, located between the retinal pigment epithelium and the sclera. It is abundantly permeated with blood vessels supplying the retina with oxygen and nutrition. substances ... Biological encyclopedic dictionary

The middle shell of the eyeball, located between the retina and the sclera. It contains a large number of blood vessels and large pigment cells that absorb excess light entering the eye, which prevents ... ... Medical terms

Choroid, the connective tissue of the Eye, located between the retina (see Retina) and the sclera (See Sclera); through it, metabolites and oxygen enter the pigment epithelium and retinal photoreceptors from the blood. S. o. subdivided ... ... Great Soviet Encyclopedia

Title appended to various bodies. This is the name, for example, of the choroid membrane of the eye (Chorioidea) replete with blood vessels, the deeper layer of the brain and spinal cord pia mater, replete with vessels, as well as some ... ... Encyclopedic Dictionary of F.A. Brockhaus and I.A. Efron

Human eyes Iris, iris, iris (Latin iris), thin movable diaphragm of the eye in vertebrates with a hole (pupil ... Wikipedia

The main task of the choroid is to provide uninterrupted nutrition to the four outer layers of the retina, including the layer of photoreceptors, and to remove metabolic products into the bloodstream. The layer of capillaries from the retina is delimited by a thin Bruch's membrane, whose function is to regulate the exchange processes between the retina and the choroid. The periosteal space, due to its loose structure, serves as a conductor for the posterior long ciliary arteries, which are involved in the blood supply to the anterior part of the organ of vision.

Choroid structure

The choroid belongs to the most extensive part in the vascular tract of the eyeball, which also includes the ciliary body and the iris. It runs from the ciliary body, bounded by the dentate line, to the limits of the optic nerve head.

Choroidal blood flow is provided through the posterior short ciliary arteries. And the blood flows through the vorticose veins. A limited number of veins (one for each quadrant, the eyeball and massive blood flow contribute to a slow blood flow, which increases the likelihood of the development of infectious inflammation processes due to the sedimentation of pathogens. There are no sensitive nerve endings in the choroid, so its diseases are painless.

In special cells of the choroid, chromatophores, there is a rich supply of dark pigment. This pigment is very important for vision, because light rays passing through the open areas of the iris or sclera can interfere with good eyesight due to diffuse illumination of the retina or lateral glare. In addition, the amount of pigment contained in the choroid determines the degree of coloration of the fundus.

For the most part, the choroid, in accordance with its name, consists of blood vessels, including several more layers: the perivascular space, as well as the supravascular and vascular layers, the vascular-capillary layer and the basal layer.

The perichoroidal perivascular space is a narrow gap that delimits the inner surface of the sclera from the vascular plate, which is permeated with delicate endothelial plates connecting the walls. However, the connection between the choroid and the sclera in this space is rather weak and the choroid easily exfoliates from the sclera, for example, with surges in intraocular pressure during surgical treatment glaucoma. To the anterior segment of the eye from the posterior, in the perichoroidal space there are two blood vessels accompanied by nerve trunks, these are the long posterior ciliary arteries.
The supravascular plate includes endothelial plates, elastic fibers and chromatophores - cells containing dark pigment. Their number in the choroidal layers in the inward direction decreases markedly, and disappears in the choriocapillary layer. The presence of chromatophores often leads to the development of choroidal nevi, and melanomas, the most aggressive of malignant neoplasms, often occur.
The vascular plate is a brown membrane, the thickness of which reaches 0.4 mm, and the size of its layer is associated with the conditions of blood filling. The vascular plate includes two layers: large vessels with arteries lying outside and vessels of medium caliber, with prevailing veins.
The choriocapillary layer, called the vascular capillary plate, is considered the most significant layer of the choroid. It provides the functions of the underlying retina and is formed from small highways of arteries and veins, which then disintegrate into many capillaries, which allows more oxygen to enter the retina. A particularly pronounced network of capillaries is present in the macular region. The very close connection between the choroid and the retina is the reason that inflammation processes, as a rule, affect almost simultaneously both the retina and the choroid.
Bruch's membrane is a thin, two-layer lamina, very tightly connected to the choriocapillary layer. She is involved in regulating the supply of oxygen to the retina and the removal of metabolic products into the blood. Bruch's membrane is also connected with the outer layer of the retina - the pigment epithelium. In the case of predisposition, with age, sometimes there are dysfunctions of a complex of structures, including the choriocapillary layer, Bruchia's membrane, and pigment epithelium. This leads to the development of age-related macular degeneration.

Video about the structure of the choroid

Diagnosis of choroid diseases

Methods for diagnosing pathologies of the choroid are:

Ophthalmoscopic examination.
Ultrasound diagnostics (ultrasound).
Fluorescent angiography, with an assessment of the state of blood vessels, detection of damage to Bruch's membrane and newly formed vessels.

Symptoms of choroid diseases

Decreased visual acuity.
Distorted vision.
Twilight vision impairment (hemeralopia).
Flies before the eyes.
Blurred vision.
Lightning before the eyes.

Diseases of the choroid

Coloboma of the choroid or complete absence of a certain part of the choroid.
Choroid dystrophy.
Choroiditis, chorioretinitis.
Detachment of the choroid that occurs during intraocular pressure surges during ophthalmic operations.
Ruptures in the choroid and hemorrhages - more often due to eye injuries.
Choroidal nevus.
Neoplasms (tumors) of the choroid.

Choroid - This is the most significant element of the vascular tract of the organ of vision, which also includes and. The structural component from the ciliary body to the optic nerve head is widespread. The basis of the shell is a collection of blood vessels.

The anatomical structure under consideration does not include sensory nerve endings. For this reason, all pathologies associated with its defeat can quite often pass without pronounced symptoms.

What is the choroid?

Choroid (choroid) - the central zone of the eyeball, located in the interval between the retina and the sclera. The network of blood vessels, as the basis of the structural element, is distinguished by its development and orderliness: large vessels are located on the outside, capillaries border the retina.

Structure

The shell structure includes 5 layers. Below is a description of each of them:

Periarticular space

Part of the space between the shell itself and the surface layer inside. Endothelial plates loosely connect the membranes to each other.

Supravascular plate

It contains endothelial plates, elastic fiber, chromatophores - cells-carriers of dark pigment.

Vascular layer

Represented by a brown membrane. The layer size indicator is less than 0.4 mm (varies on the quality of blood supply). The plate contains a layer of large vessels and an interlayer with a prevalence of veins of average size.

Vascular capillary plate

Most significant element. Includes small veins and arteries, passing into many capillaries - a regular enrichment of the retina with oxygen is ensured.

Bruch Membrane

A narrow plate, combined from a pair of layers. The outer layer of the retina is in close contact with the membrane.

Functions

The choroid performs key function - trophic. It consists in a regulatory effect on material metabolism and nutrition. In addition to these, the structural element takes on a number of secondary functions:

regulation of the flow of sunlight and heat energy transported by them;
participation in local thermoregulation within the organ of vision due to the production of thermal energy;
optimization of intraocular pressure;
withdrawal of metabolites from the eyeball area;
delivery of chemical agents for the synthesis and production of pigmentation of the organ of vision;
the content of the ciliary arteries feeding the proximal organ of vision;
transportation of nutrients to the retina.

Symptoms

For a rather long period of time, the pathological processes, with the development of which the choroid suffers, can proceed without obvious manifestations.

Choroid of the eyeball (tunica vasculosa bulbi). Embryogenetically, it corresponds to a soft meninges and contains a dense plexus of blood vessels. It is divided into three sections: the iris ( iris), ciliary or ciliary body (corpus ciliare) and the choroid itself ( chorioidea). Each of these three sections of the vascular tract has specific functions.

Iris is the anterior well-visible section of the vascular tract.

The physiological significance of the iris is that it is a kind of diaphragm that regulates the flow of light into the eye, depending on the conditions. Optimal conditions for high visual acuity are provided with a pupil width of 3 mm. In addition, the iris takes part in ultrafiltration and outflow of intraocular fluid, and also ensures the constancy of the moisture temperature of the anterior chamber and the tissue itself by changing the width of the vessels. The iris is a pigmented, circular plate located between the cornea and the lens. In its center there is a round hole, the pupil ( pupilla), the edges of which are covered with a pigmented fringe. The iris has an exceptionally peculiar pattern, due to the radially located rather densely intertwined vessels and connective tissue beams (lacunae and trabeculae). Due to the friability of the iris tissue, many lymphatic spaces are formed in it, which open on the anterior surface with holes of various sizes or lacunae, crypts.

In the anterior part of the iris, there are many process pigment cells - chromatophores containing golden xanthophores and silvery guanophores. The posterior region of the iris is black due to the large number of fuscin-filled pigment cells.

In the anterior mesodermal layer of the iris of the newborn, the pigment is almost absent, and the posterior pigment plate shines through the stroma, causing the bluish color of the iris. The iris acquires a permanent color by the age of 10-12 years of a child's life. In places where pigment accumulates, "freckles" of the iris are formed.

In old age, depigmentation of the iris is observed in connection with sclerotic and dystrophic processes in the aging body, and it again acquires a lighter color.

There are two muscles in the iris. The circular muscle, constricting the pupil (m. Sphincter pupillae), consists of circular smooth fibers located concentrically to the pupillary edge at a width of 1.5 mm - the pupillary girdle; innervated by parasympathetic nerve fibers. The muscle that dilates the pupil (m. Dilatator pupillae) consists of pigmented smooth fibers that lie radially in the posterior layers of the iris and have sympathetic innervation. In young children, the iris muscles are poorly expressed, the dilator is almost non-functional; the sphincter predominates and the pupil is always narrower than in older children.

The peripheral part of the iris is made up of the ciliary (ciliary) belt up to 4 mm wide. At the border of the pupillary and ciliary zones, by 3-5 years a collar (mesentery) is formed, in which the small arterial circle of the iris is located, formed by the anastomosing branches large circle and providing blood supply to the pupillary girdle.

The large arterial circle of the iris is formed on the border with the ciliary body due to the branches of the posterior long and anterior ciliary arteries, which anastomose to each other and give return branches to the choroid itself.

The iris is innervated by sensitive (ciliary), motor (oculomotor) and sympathetic nerve branches. The constriction and dilation of the pupil is carried out mainly through the parasympathetic (oculomotor) and sympathetic nerves. In the case of damage to the parasympathetic pathways, while maintaining the sympathetic, there is absolutely no reaction of the pupil to light, convergence and accommodation. The elasticity of the iris, which depends on the person's age, also affects the size of the pupil. In children under 1 year old, the pupil is narrow (up to 2 mm) and reacts poorly to light, weakly expands, in adolescence and young age it is wider than average (up to 4 mm), reacts vividly to light and other influences by old age, when the elasticity of the iris decreases sharply, the pupils, on the contrary, narrow and their reactions are weakened. None of the parts of the eyeball contains so many indicators for understanding the physiological and especially the pathological state of the central nervous system human as a pupil. This unusually sensitive apparatus easily reacts to various psycho-emotional shifts (fear, joy), diseases of the nervous system (tumors, congenital syphilis), diseases internal organs, intoxication (botulism), childhood infections (diphtheria), etc.

Ciliary body is, figuratively speaking, iron internal secretion eyes. The main functions of the ciliary body are the production (ultrafiltration) of intraocular fluid and accommodation, that is, the creation of conditions for clear vision near and far. In addition, the ciliary body takes part in the blood supply to the underlying tissues, as well as in maintaining normal ophthalmotonus due to both the production and outflow of intraocular fluid.

The ciliary body is like a continuation of the iris. Its structure can be found only with tonnage and cycloscopy. The ciliary body is a closed ring about 0.5 mm thick and almost 6 mm wide, located under the sclera and separated from it by the supraciliary space. On a meridional section, the ciliary body has a triangular shape with a base towards the iris, one apex towards the choroid, the other towards the lens and contains the ciliary (accommodative muscle - m. ciliaris), consisting of smooth muscle fibers. On the tuberous front inner surface of the ciliary muscle, there are more than 70 ciliary processes ( processus ciliares). Each ciliary process consists of a stroma with a rich network of vessels and nerves (sensory, motor, trophic), covered with two sheets (pigment and non-pigment) epithelium. The anterior segment of the ciliary body, which has pronounced processes, is called the ciliary crown ( corona ciliaris), and the posterior processless part is the ciliary circle ( orbiculus ciliaris) or flat section ( pars plana). The stroma of the ciliary body, like the iris, contains a large number of pigment cells - chromatophores. However, the ciliary processes do not contain these cells.

The stroma is covered with an elastic vitreous plate. Further inwardly, the surface of the ciliary body is covered with ciliary epithelium, pigment epithelium and, finally, the inner vitreous membrane, which are a continuation of similar formations of the retina. Zonal fibers are attached to the vitreous membrane of the ciliary body ( fibrae zonulares), on which the lens is fixed. The posterior border of the ciliary body is the dentate line (ora serrata), where the vascular itself begins and the optically active part of the retina ends ( pars optica retinae).

The blood supply to the ciliary body is carried out through the posterior long ciliary arteries and anastomoses with the vasculature of the iris and choroid. Thanks to the rich network of nerve endings, the ciliary body is very sensitive to any irritation.

In newborns, the ciliary body is underdeveloped. The ciliary muscle is very thin. However, by the second year of life, it significantly increases and due to the appearance of combined contractions of all eye muscles, it acquires the ability to accommodate. With the growth of the ciliary body, its innervation is formed and differentiated. In the first years of life, the sensitive innervation is less perfect than the motor and trophic, and this is manifested in the painlessness of the ciliary body in children during inflammatory and traumatic processes. In seven-year-old children, all relationships and sizes of the morphological structures of the ciliary body are the same as in adults.

Choroid itself (chorioidea) is the posterior part of the vascular tract, visible only with biomicro- and ophthalmoscopy. It is located under the sclera. The choroid accounts for 2/3 of the entire vascular tract. The choroid takes part in feeding the avascular structures of the eye, photoenergetic layers of the retina, in ultrafiltration and outflow of intraocular fluid, in maintaining normal ophthalmotonus. The choroid is formed by the posterior short ciliary arteries. In the anterior section, the vessels of the choroid anastomose with the vessels of the large arterial circle iris. In the posterior section around the optic nerve head there are anastomoses of the vessels of the choriocapillary layer with the capillary network of the optic nerve from the central retinal artery. The choroid thickness is up to 0.2 mm at the posterior pole and up to 0.1 mm in the front. Between the choroid and the sclera there is a perichoroidal space (spatium perichorioidale), filled with outflowing intraocular fluid. In the early childhood there is almost no perichoroidal space at all, it develops only by the second half of the child's life, opening in the first months first in the area of \u200b\u200bthe ciliary body.

Choroid is a multi-layered formation. The outer layer is formed by large vessels (vascular plate, lamina vasculosa). Between the vessels of this layer there is a loose connective tissue with cells - chromatophores, the color of the choroid depends on their number and color. As a rule, the number of chromatophores in the choroid corresponds to the general pigmentation of the human body and is relatively small in children. Thanks to the pigment, the choroid forms a kind of dark camera obscura, preventing the reflection of the rays coming through the pupil into the eye and providing a clear image on the retina. If there is little or no pigment in the choroid (more often in fair-haired persons), then there is an albino picture of the fundus. In such cases, the function of the eye is significantly reduced. In this shell, in the layer of large vessels, there are also 4-6 vorticose, or vortex, veins ( v. vorticosae) through which venous outflow mainly from the posterior part of the eyeball.

Next comes the layer of middle vessels. Connective tissue and there are fewer chromatophores and veins predominate over arteries. Behind the middle vascular layer is a layer of small vessels, from which branches branch off into the innermost - choriocapillary layer ( lamina choriocapillaris). The choriocapillary layer has an unusual structure and passes through its lumen (lacunae) not one uniform element of blood, as usual, but several in one row. In terms of diameter and number of capillaries per unit area, this layer is the most powerful in comparison with others. Top wall capillaries, that is, the inner shell of the choroid, is the vitreous plate, which serves as a border with the retinal pigment epithelium, which, however, is intimately associated with the choroid. It should be noted that the vasculature is most dense in the posterior choroid. It is very intense in the central (macular) area and poor in the area of \u200b\u200bthe optic nerve exit and near the dentate line.

The choroid contains, as a rule, the same amount of blood (up to 4 drops). An increase in the choroidal volume by one drop can cause an increase in the pressure inside the eye by more than 30 mm Hg. Art. The relatively large amount of blood continuously passing through the choroid provides constant nutrition pigment epithelium the retina associated with the choroid, where active photochemical processes take place. The innervation of the choroid is mainly trophic. Due to the lack of sensitive nerve fibers its inflammation, injuries and swellings are painless.