The ciliary body structure and functions. Ciliary (ciliary) body: structure, functions

Ciliary body of the eye, also known as ciliary body of the eye, is the middle part of the choroid.
It suspends the lens according to its means and provides the function of accommodating the eye. In addition to all this, the ciliary body of the eye takes part in the production of aqueous humor. The ciliary body is located under the sclera of the eye, connects the vascular and iris.

The ciliary body of the eye performs the filtration function of fluid from the bloodstream. A significant part of the ciliary body is represented by muscle tissue and blood vessels. Most developed muscles ciliary body are located in several layers with different directions, these muscles contract and relax, changing the curvature of the lens.

The structure of the ciliary body

The anatomical shape of the ciliary body is a closed ring, which is located under between and. Due to the fact that the ciliary body is hidden by the iris, its examination at the time of the eye examination is impossible. In the structure of the structure of the ciliary body, two parts are distinguished: flat and ciliary. The width of the flat part is 4 mm and this part reaches the jagged edge. The width of the ciliary part is 2 mm, it contains about 80 ciliary processes, the totality of which is a ciliary crown.

The ciliary process is a small plate that has a pronounced network of blood vessels, due to which the filtration function of the blood is ensured, followed by the formation of intraocular fluid.

The cellular structure of the ciliary body is represented by the mesodermal layer, which includes muscle and connective tissue, and the neuroectodermal layer, which contains a non-functioning layer of the epithelium from the retina of the eye.

The order of the layers of cells in the ciliary body from the inside to the outside:

muscle layer
- vascular layer
- basal plate
- pigment layer of the epithelium
- non-pigmented layer of the epithelium
- inner boundary membrane

In the muscle layer, several groups of muscle bundles are distinguished, which are located in different directions. The Brücke muscles have a longitudinal direction and they are located outside, deeper in the radial direction are located muscle fibers, they are Ivanov's muscles, and the last group of muscles, Muller's muscles, has a circular direction.

The inner surface of the ciliary body is connected to the lens capsule by means of the ciliary girdle, which consists of many thin fibers. The band performs a fixing function, holding the lens in correct position, and during the work of the ciliary muscle takes part in the process. The anterior and posterior zonular fibers are isolated, anterior to the posterior part of the lens and to its equator, the posterior ones are attached to the equator of the lens and its anterior part.

At the very moment when the ciliary muscle is tense, the ligaments relax, the tension from the lens capsule decreases, the lens takes on a rounded shape. At the moment of relaxation, the reverse process occurs, the ligaments become tense, the tension of the lens capsule increases, and it acquires a more elongated shape.

The layer of blood vessels is a direct continuation of the choroid itself, a significant part of which consists of veins of different sizes, because the arteries of the choroid proper are located in the perivascular space and the ciliary body, where their location is in the muscle layer, giving small branches of the vessels back to the vascular proper shell.

The basement membrane is also a continuation of the choroid itself, the inner coating of which is represented by pigmented and non-pigmented epithelium. These two layers of the epithelium are a non-functioning retina, separated from the vitreous body by a boundary membrane.

The blood supply to the ciliary body is provided by two arteries, which are limited in the supravascular space by the pole of the eye and the ciliary body. The ciliary body has a large number of nerve endings, however, in newborns it is poorly developed, only by seven, sometimes even by ten years, the ciliary body begins to fully function.

An important part of the vascular network of the organ is the ciliary or ciliary body of the eye, consisting of vessels and smooth muscle cells. When the muscles tense or relax, the shape of the lens changes, due to which it is possible to see objects that are near or far clearly. Capillaries contribute to the production of fluid, blood supply to the underlying tissues is performed. Thanks to this, all the main functions that the eye performs are supported.

The correct functioning of the organ can be assessed using accommodometry. This test will determine the indicators of absolute accommodation (each eye separately) and relative (both at the same time). It is believed that good performance is 2 diopters. Differences in one direction or another are characteristic of myopia and hypermetropia.

Histological structure and blood supply

The ciliary processes contain capillaries and contribute to the production of fluid, blood supply to the underlying tissues is carried out. It supports the basic functions of the eye. The body closes the sclera. The structure can only be assessed with gonio- and cycloscopy. Ophthalmologists divide it into 2 parts: flat (dark) and ciliary (folded). On each process of the second part there is a plate with blood vessels that cleans the blood flow to distribute fluid. The ciliary body and its structure:

muscles (subcutaneous part);
vessels (parts of the choroid);
basal plate associated with a sheath of vessels;
cubic pigmented and cylindrical non-pigmented epithelium;
the inner membrane is the barrier between the epithelium and the vitreous layer.

A disease of the organs of vision caused by infection causes inflammation, which is called cyclitis.

In diseases caused by infection, acute pain is very pronounced. Inflammation of the function of the ciliary body may develop. The peculiarity of the structure is such that each smooth muscle cell has a separate supply of nerve endings. It is the only muscle human body with the ability to react in such a way to irritations, so a person feels pain.

Muscles and vessels of the ciliary body

An important place is occupied by the following in equipping the clarity of vision - muscles. The cilia belt connects the lens capsule and the surface inside the ciliary body, while properly holding this part of the eye. Its shape will become rounded if the muscles of the ligament tighten. Conversely, it will become elongated when the muscles relax. Groups of muscle bundles are directed from each other in different directions.

The pattern with veins can only be seen with an ophthalmoscopic examination. Near the shell of the eye there are arteries both in the muscle fibers and in the ciliary body. This part with many vessels performs moistening of the retina and the function of accommodation. Forms a frame for the iris. Inside contains up to 4 drops of blood. Violation of this volume above or below the limits causes a rise in pressure inside the eye.

basement membrane

Lamellar layers - non-functional retina. Two arteries provide blood supply to the ciliary body. The main tasks performed by the membrane are an elastic support and a filtration barrier. The pigment contributes to the formation of a dark camera - pinhole, which provides clarity of objects on the retina and prevents the reflection of rays.

Functions of the ciliary body

The ciliary body is one of the elements that provide the process of accommodation of the eye.

The eye is an organ that combines many functions. The ciliary epithelium produces intraocular fluid under perforated blood vessels. Ions leave their channel through them. The epithelium absorbs and transports various substances. Physiologically, the shape of the lens capsule is adjusted. A person can clearly see when the pressure is stable. Changes in the shape of the lens - focusing, depending on the tension of the fibers on the ciliary muscle. Branches of the ciliary nerves are responsible for sensitivity.

Diseases and their symptoms

Types of ailments and pathological conditions:

Glaucoma. It is characterized by a periodic increase in pressure inside the eye.
Iridocyclitis. It is accompanied by an inflammatory process that affects the ciliary body and the iris.
Violation of accommodation, in which there is no clarity of objects.
Hypopion, which is a collection of pus in the anterior chamber of the eyeball.
Neoplasms in the ciliary body. There are benign and malignant.
Hypotension of the eye. The pressure in the eye is greatly reduced, which can lead to visual impairment.

In a dark room, the light guide is applied to the cornea and the size of the neoplasm is estimated. The following research methods will help identify the disease:

conducting symptoms by palpation through a closed eye;
examination under a microscope;
transillumination diagnostics of the organ;
Ultrasound structures;
pressure measurement;
tonography with measurement of secretion.

ciliary body is a closed ring 6-8 mm wide, which covers the eye along its entire circumference. There are two main sections of the ciliary body - anterior and posterior.

The anterior section is a folded part of the ciliary body 2 mm wide. It is adjacent to the iris, has 70-80 oblong ridge-like processes. The processes have a whitish color, stand inside the eye and are located radially around the equatorial zone of the lens, forming a closed ring. The height of the processes is about 0.8 mm. The ciliary processes produce aqueous humor.

The posterior ciliary body is the flat part of the ciliary body that passes into the choroid.

Structure

The ciliary body is not accessible for inspection, as it is hidden by the iris. On the meridional section, the ciliary body looks like a triangle. The place of transition of the choroid to the ciliary body coincides with the place of transition of the visual part of the retina to the blind and is called the jagged edge (ora serrata).

Ciliary processes (processus ciliares) depart from the inner part of the ring towards the lens. The set of processes is a ciliary crown (corona ciliaris). Each of the 70-80 processes consists of stroma, thin-walled wide capillaries, and two layers of epithelial cells: pigmented and non-pigmented. Epithelial cells are separated from stromal substances and the space of the posterior chamber by outer and inner boundary membranes. Radially very thin fibers depart from these processes (zonular fibers, fibrae zonulares), attached to the equator of the lens. The totality of these fibers is called the zonula ligament or ciliated girdle (zonula ziliaris).

Histologically, the ciliary body is formed from highly vascularized loose connective tissue and smooth myocytes. Externally, the ciliary body and its processes are covered with the ciliary part of the retina (pars ciliaris retinae), which together with the iris part of the retina (pars iridica retinae) forms the blind part of the retina (pars caeca retinae). The epithelium is two-layered. The inner layer of epithelial cells is pigmented, the outer one is not. It is these unpigmented epithelial cells that are involved in the production of aqueous humor and hyaluronic acid.

The anterior section - the stroma of the ciliary body, has in its composition a large number of pigment cells - chromatophores, it is covered with an elastic vitreous plate.
The posterior portion of the ciliary body is covered by ciliary epithelium, pigment epithelium, and the internal vitreous membrane. Zonular fibers are attached to the vitreous membrane, on which the lens is fixed. The posterior border of the ciliary body is the dentate line.

muscles

The ciliary (accommodative) muscle consists of smooth muscle fibers and is connected by means of a ciliary search (zinn ligament) with the lens, regulating its curvature. In the muscle, meridional (longitudinal), radial and circular fibers are isolated.

innervation

Autonomic innervation: the meridial and radial parts of the muscle are innervated by the sympathetic cervical nerve, and the circular part is innervated by the parasympathetic fibers of the oculomotor nerve.

The ciliary muscle is innervated by the oculomotor nerve (III pair of cranial nerves). Switching of parasympathetic fibers is carried out in the ciliary node.

Sensory fibers depart from the ciliary body in the form of short and long ciliary nerves, which are branches of the trigeminal nerve (V pair of cranial nerves).

blood supply

The vascular network of the ciliary body is formed by two long posterior ciliary arteries (branches of the ophthalmic artery), which pass through the sclera at the posterior pole of the eye, and then go in the suprachoroidal space along the 3 and 9 o'clock meridian, anastomose with branches of the anterior and posterior short ciliary arteries.

The ciliary body is not available for direct examination, it is observed only with gonio- and cycloscopy. It is a closed ring, covering the eye around the entire circumference. The width of the ring is about 6-7 mm, the nasal and upper part is slightly narrower than the temporal and lower - 5-5.9 and 6-6.7 mm, respectively, the greatest thickness - up to 1 mm, is determined in the anterior part, and the ciliary body is thicker in lower segment than the upper one. The outer part of the ciliary body, attaching to the scleral spur or immediately behind it, forms here the anterior annular ligament of the choroid. Immediately after this ligament, the supraciliary space begins. On the meridional cut, the ciliary body may look like this: (A.P. Nesterov, Yu.E. Batmanov, 1974):

Triangular (8%) - the mass of tissues of the ciliary body, and therefore, its thickness gradually decreases in the direction from front to back. The apex of the triangle looks backward, towards the choroid, and the base looks forward, towards the iris. In eyes with this shape of the ciliary body, it comes very close to the equator of the lens, which predisposes to blockade of the anterior chamber angle and the development of malignant glaucoma.

Rhomboid, or club-shaped (59%) - the thickest part is somewhat posterior to the anterior edge of the ciliary body. Both anteriorly and especially posteriorly, the thickness of this structure decreases

Oval (23%) - characterized by an even greater posterior displacement of the main mass of the ciliary body, while the latter is flatter.

Incorrect (4%) - the anterior part of the ciliary body departs from the sclera and turns almost at a right angle into the anterior chamber. In this case, the anterior part of the ciliary body, together with the iris, forms the posterior wall of the anterior chamber. Edema of the ciliary body in such cases can lead to blockade of the APC, and after fistulizing operations, blockade of the burr hole by the anterior part of the ciliary body may occur.

The thickness of the ciliary body is 0.45-0.9 mm.

The ciliary body is projected onto the sclera immediately behind the limbus. In a typical case, on a meridional section, the anterior part of the ciliary body consists of two processes - anterior and posterior, and resembles an open mouth. This form is formed due to resorption and reorganization of that part of the stroma of the ciliary body, which is adjacent to the anterior chamber during embryonic development. The anterior process goes to the scleral spur, partly attaches to it, and partly continues to the anterior border Schwalbe ring, in the form of a uveal portion of the trabecula. The length of this process can reach 350 µm. In eyes with a well-developed anterior process, the supraciliary fissure extends anteriorly from the main mass of the ciliary body to the region located above the anterior chamber. If during the operation the anterior chamber is opened along its posterior border, then in such eyes the incision will pass posterior to the anterior annular ligament of the choroid and the supraciliary space will communicate with the anterior chamber, although cyclodialysis was not performed. The thickness of the anterior process at the base is 60 µm on average, and can reach 340 µm. The thinner the process, obviously, the easier the intraocular fluid can be filtered from the eye by the uveoscleral route. The posterior process is connected with the iris or goes behind it into the posterior chamber of the eye. Its average length is 60 µm, the maximum length is 400 µm. In 30% of cases, the posterior process is absent.

The anterior surface of the ciliary body, facing the anterior chamber, is represented by a thin layer of stroma with a well-defined anterior boundary layer. Immediately posterior to this layer is the ciliary muscle. In another embodiment, the ciliary muscle is separated from the anterior chamber by a thick layer of loose tissue. This type of structure probably occurs with incomplete resorption of the stroma at the top of the APC. Loose tissue can be considered as a variant of a very developed pectinate ligament. The anterior part of the ciliary body does not have a dense endothelial layer that limits the interstitial spaces from the anterior chamber. Consequently, part of the fluid from the anterior chamber enters the intercellular spaces between the bundles of the ciliary muscle. A drug increase in the tone of the ciliary muscle leads to an increase in the outflow of fluid through the Schlemm canal, but completely blocks the uveoscleral outflow pathway, since an increase in the tone of muscle fibers closes the interstitial spaces inside the muscle (Bill A., 1977).

The posterior border of the ciliary body runs along the so-called dentate line, which approximately corresponds to the places of attachment of the rectus muscles on the sclera (except for the superior rectus muscle, which is attached behind the projection of the dentate line onto the sclera). The dentate line got its name because of its peculiar appearance, here the "protrusions" of the ciliary body "grow" into the peripheral retina. The largest number of this kind of "dentate processes" is in the upper inner quadrant. Their number progressively decreases from the lower internal, through the upper temporal to the lower temporal quadrant.

The CT consists of two sections: the anterior section - the folded part, corona ciliaris, 2 mm wide, and the posterior section, the flat part - pars plana (sharply separated from the adjacent choroid in black), about 3.5-4 mm wide (on the outside ) and 3 mm (on the inside). The inner diameter of the ring of processes of the ciliary body is about 12 mm (Sheplakova V. M., 1961; Duke-Elder S. W., 1961).

Some anatomical parameters of the ciliary body (A. P. Nesterov, Yu. E. Batmanov, 1974):

The thickness of the ciliary crown (without processes) - 450-930 microns

The thickness of the ciliary muscle is 150-800 microns

Thickness of the flat part - 160-620 microns

The distance from the anterior edge of the suprachoroidal fissure to the apex of the angle is from 250 μm anteriorly to 400 μm posteriorly.

The folded part of the ciliary body adjoins directly to the iris and has 70-80 ridge-shaped processes of a whitish hue (they are weakly pigmented), located radially around the lens equator. The degree of development of the ciliary processes and their position are subject to significant variations. In some cases, they go to the back of the iris, while the root of the iris becomes especially rigid and its bombardment is unlikely.

As a rule, the ciliary processes begin at the root of the iris, but in 5% of cases they can be located on the posterior surface of the ciliary belt of the iris or slightly backwards from the root. This arrangement of the processes allows us to distinguish 3 levels of the posterior chamber: low, medium, high. In the angle of the anterior chamber, these anatomical variants of the location of the processes correspond to a strip of the ciliary body of different widths. Knowledge of anatomical features can prevent a number of complications. An attempt to capture the iris to perform an iridectomy can lead to infringement of the processes of the ciliary body in the forceps, and its excision can lead to prolonged, massive bleeding.

Among the processes of the ciliary body, the main and intermediate ones should be distinguished (Bochkareva A. A. et al., 1976). The main processes are massive, they form a cornice and slope, which ends abruptly at the transition to the flat part of the ciliary body. Between the two main processes are 2-3 intermediate ones. The latter have the appearance of warty elevations that stretch in a radial direction. The distance from the lens equator to the tops of the processes is estimated at an average of 0.5 mm. highest height(up to 0.8 mm) the processes are in the anterior part of the ciliary body, the height of the processes decreases posteriorly, and they pass into small folds. Between the processes there are grooves, at the bottom of which the fibers of the zinn ligament are attached, gradually merging with the inner surface of the CT. However, the folded part is only an intermediate zone of fiber fixation. The bulk of the fibers of the ciliary girdle, both from the anterior and posterior surfaces of the lens, is directed posteriorly and is attached throughout the ciliary body up to the dentate line.

On the surface of the flat part, a row of dark stripes is visible, extending from the teeth of the dentate line and continuing to the beginning of the furrows between the processes of the ciliary body. The observed age-related changes in the flat part of the ciliary body are hyalinosis of the connective tissue, thickening of the anterior limiting membrane, proliferation of pigmented and non-pigmented epithelium, obliteration of arterioles.

The presence of ciliary processes and accommodative muscle in the ciliary body are features that provide the secretory and accommodative functions of the ciliary body.

Ciliary (ciliary) body - the structural part of the choroid notes obaglaza.ru, consisting of vessels and muscles. Its muscle fibers are located in different directions, which allows you to take an active part in the process of accommodation.

Functions

Due to its structure, the ciliary body performs a number of important functions:

it plays leading role in changing the shape of the lens;
blood vessels provide blood circulation to the iris;
small vessels are involved in the formation of intraocular fluid and normalize the pressure inside the eye;
supporting, for the choroid plexus of the iris.

Structure

The ciliary body is located behind the sclera and is not visible during visual inspection, says obaglaza.ru. The main localization is behind the iris and around the eyeball. In section it has the shape of a triangle, the edges of which are attached to the lens.

Anatomically, the ciliary body has two parts: a flat (4 mm wide) and a ciliary part (2 mm). The ciliary part has processes (plates) with small capillaries that produce intraocular fluid.

Depending on the functions of the cells that form the layer, there are mesodermal (muscle and connective fibers) and neuroectodermal (epithelial fibers) parts.

Layers

Layers of obaglazadistinguishes depending on the cells that form them:

Muscular (deepest). Forms the position of the lens (accommodation process). The muscular part is divided into processes running in the outer longitudinal (Bruke muscle), radial (Ivanov muscle) and circular (Muller muscle) directions.

The ciliary body is attached to the lens with the help of a ciliary belt (thin muscle fibers). Its front part is attached in the zone of the lens equator, and the back part is in front of it. The tension of the muscle layer of the ciliary body relaxes the ligaments of the lens, and it takes on a spherical shape. When the ligaments tighten and the ciliary body relaxes, the lens stretches.

Vascular. The layer is formed from venous vessels, different size, which are a continuation of the vessels of the choroid. The arteries of the choroid lie mainly in the intervascular space and the muscular layer.
Basal. The layer is formed in the form of a plate and is a continuation of the choroid.
Epithelial. Pigmented and non-pigmented epithelium (non-functional retina) covers the plate of the basal layer from the inside.
border membrane. It acts as a barrier between the epithelium and the vitreous body of the eyeball.

Blood supply and innervation

The ciliary body is provided with a rush of blood due to two arteries that pass from the posterior ophthalmic pole into the intervascular space of the choroid.

The nerve endings of the ciliary body are fully formed by the age of 7-10, therefore, obglaza.ru focuses attention in newborns, diseases can proceed painlessly.

Disease symptoms

Signs of diseases can be disguised as pathologies of various organs of the eyeball (lens, retina, etc.). The most common symptoms are:

disturbance of accommodation (spasm, paralysis);
presbyopia;
violation of the normal production of intraocular moisture;
with inflammation, soreness, redness, clouding of moisture, hypopyon are observed;
neoplasms.

Diagnostics

Diseases of the ciliary body are difficult to diagnose, insists obglazar due to their similarity with other pathologies, therefore, the following methods are used to make the correct diagnosis:

palpation - pressure in the area where the ciliary body is located (in inflammatory processes, the procedure becomes painful);
examination with a contact lens;
transillumination - examination with the help of light (helps to identify neoplasms);
ultrasound examinations (biomicroscopy);
tonometry (measurement of pressure inside the eye);
tonography (study of hydrodynamics).