Medium shell. The eyeball and its anatomy. What is the feature? Part of the choroid of the eye is called

Shells of the eye

The eyeball has three shells - outer fibrous, middle vascular and inner, which is called the retina. All three membranes surround the nucleus of the eye. (see appendix 1)

The fibrous membrane consists of two parts - the sclera and the cornea.

The sclera is also called the white of the eye or the tunica albuginea, it is dense white in color, consists of connective tissue. This shell makes up most of the eyeball. The sclera serves as the frame of the eye and performs a protective function. In the posterior sections of the sclera, there is a thinning - a cribriform plate through which the optic nerve exits the eyeball. In the anterior parts of the visual apple, the sclera passes into the cornea. The place of this transition is called the limbus. In newborns, the sclera is thinner than in adults, so the eyes of young animals have a bluish tint.

The cornea is a transparent tissue located in front of the eye. The cornea rises slightly above the level of the sphere of the eyeball, since the radius of its curvature is less than the radius of the sclera. Normally, the cornea has the shape of a sclera. There are a lot of sensitive nerve endings in the cornea, therefore, in acute diseases of the cornea, severe lacrimation and photophobia occur. The cornea does not have blood vessels, and the metabolism in it occurs due to the moisture of the anterior chamber and tear fluid. Violation of the transparency of the cornea leads to a decrease in visual acuity.

The choroid is the second shell of the eye, it is also called the vascular tract. This sheath consists of a network of blood vessels. Conventionally, for a better understanding of internal processes, it is divided into three parts.

The first part is the choroid itself. It has the largest area and lines the two posterior thirds of the sclera from the inside. It serves for the metabolism of the third shell - the retina.

Further, in front is the second, thicker part of the choroid - the ciliary (ciliary) body. The ciliary body has the form of a ring, located around the limbus. The ciliary body consists of muscle fibers and many ciliary processes. From the ciliary processes, the fibers of the zinn ligament begin. The second end of the zinn ligaments is woven into the lens capsule. In the ciliary processes, intraocular fluid is formed. The intraocular fluid participates in the metabolism of those structures of the eye that do not have their own vessels.

The muscles of the ciliary body go in different directions and attach to the sclera. With the contraction of these muscles, the ciliary body is somewhat pulled forward, which weakens the tension of the zinn ligaments. This loosens the tension of the lens capsule and allows the lens to become more convex. A change in the curvature of the lens is necessary for a clear distinction between the details of objects at different distances from the eye, that is, for the process of accommodation.

The third part of the choroid is the iris or iris. The color of the eyes depends on the amount of pigments in the iris. Blue-eyed people have little pigment, brown-eyed people have a lot. Therefore, the more pigment, the darker the eye. Animals with a reduced pigment content, both in the eyes and in the coat, are called albinos. The iris is a round membrane with a hole in the center, consisting of a network of blood vessels and muscles. The muscles of the iris are arranged radially and concentrically. When the concentric muscles contract, the pupil constricts. If the radial muscles contract, the pupil dilates. Pupil size depends on the amount of light falling on the eye, age and other factors.

The third, innermost layer of the eyeball is the retina. She, in the form of a thick film, lines the entire back of the eyeball. The nutrition of the retina occurs through the vessels that enter the area of ​​the optic nerve, and then branch out and cover the entire surface of the retina. It is on this shell that the light reflected by the objects of our world falls. In the retina, the rays are converted into a nerve signal. The retina consists of 3 types of neurons, each of which forms an independent layer. The first is represented by the receptor neuroepithelium (rods and cones and their nuclei), the second by bipolar neurons, and the third by ganglion cells. There are synapses between the first and second, second and third layers of neurons.

In accordance with the location, structure and function in the retina, two parts are distinguished: the visual, lining the inside of the back, most of the wall of the eyeball, and the anterior pigment, covering the inside of the ciliary body and the iris.

The visual part contains photoreceptor, primarily sensory nerve cells. There are two types of photoreceptors - rods and cones. Where the optic nerve forms on the retina, there are no sensory cells. This area is called the blind spot. Each photoreceptor cell consists of an outer and an inner segment; in the rod, the outer segment is thin, long, cylindrical; in the cone, it is short, conical.

The photosensitive layer of the retina contains several types of nerve cells and one type of glial cells. The nucleated areas of all cells form three layers, and the zones of synoptic contacts of cells form two mesh layers. Thus, in the visual part of the retina, the following layers are distinguished, counting from the surface in contact with the choroid: a layer of pigment epithelial cells, a layer of rods and cones, an outer limiting membrane, an outer nuclear layer, an outer reticular layer, an inner nuclear layer, an inner reticular layer, ganglionic layer, nerve fiber layer and inner limiting membrane. (Kvinikhidze G.S. 1985). (see appendix 2)

The pigment epithelium is anatomically closely related to the choroid. The pigment layer of the retina contains a black pigment, melanin, which is actively involved in providing clear vision. The pigment, absorbing light, prevents it from being reflected from the walls and reaching other receptor cells. In addition, the pigment layer contains a large amount of vitamin A, which is involved in the synthesis of visual pigments in the outer segments of the rods and cones, where it can be easily transferred. The pigment epithelium is involved in the act of vision, since it forms and contains visual substances.

The rod and cone layer consists of outer segments of photoreceptor cells surrounded by outgrowths of pigment cells. Rods and cones are in a matrix containing glycosaminoglycans and glycoproteins. There are two types of photoreceptor cells that differ in the shape of the outer segment, but also in quantity, distribution in the retina, ultrastructural organization, and also in the form of synaptic connection with the processes of deeper retinal elements - bipolar and horizontal neurons.

The retinas of diurnal animals and birds (diurnal rodents, chickens, pigeons) contain almost exclusively cones; in the retinas of nocturnal birds (owls, etc.), visual cells are predominantly represented by rods.

The main cellular organelles are concentrated in the inner segment: an accumulation of mitochondria, polysomes, elements of the endoplasmic reticulum, and the Golgi complex.

The rods are dispersed mainly along the periphery of the retina. They are characterized by increased photosensitivity in low light, they provide night and peripheral vision.

Cones are located in the central part of the retina. They can distinguish the smallest details and color, but for this they need a large amount of light. Therefore, in the dark, the flowers seem the same. Cones fill a special area of ​​the retina - the yellow spot. In the center of the macula is the central fovea, which is responsible for the greatest visual acuity.

However, the shape of the outer segment is not always possible to distinguish between cones and rods. So, the cones of the fovea - the places of the best perception of visual stimuli - have a thin outer segment elongated in length, and resembles a stick.

The inner segments of rods and cones also differ in shape and size; at the cone it is much thicker. The main cellular organelles are concentrated in the inner segment: an accumulation of mitochondria, polysomes, elements of the endoplasmic reticulum, and the Golgi complex. Cones in the inner segment have a section consisting of an accumulation of mitochondria tightly adjacent to each other with a lipid droplet located in the center of this accumulation - an ellipsoid. Both segments are connected by the so-called leg.

Among the photoreceptors there is a kind of "specialization". Some photoreceptors signal only the presence of a black vertical line on a light background, others - a black horizontal line, and others - the presence of a line inclined at a certain angle. There are groups of cells that report contours, but only those that are oriented in a certain way. There are also types of cells responsible for the perception of movement in a particular direction, cells that perceive color, shape, etc. The retina is extremely complex, so a huge amount of information is processed in milliseconds.

The human visual organ has a rather complex anatomy. One of the most interesting elements that make up the eye is the eyeball. In the article we will consider in detail its structure.

One of the most important components of the eyeball is its membranes. Their function is to limit the internal space on the front and rear cameras.

There are three shells in the eyeball: outer, middle, inner .

Each of them is also divided into several elements that are responsible for certain functions. What are these elements, and what functions are inherent in them - more on that later.

Outer shell and its components

In the photo: the eyeball and its constituent elements

The outer shell of the eyeball is called "fibrous". It is a dense connective tissue and consists of the following elements:
Cornea.
Sclera.

The first is located in front of the organ of vision, the second fills the rest of the eye. Due to the elasticity that is characteristic of these two components of the shell, the eye has its inherent shape.

The cornea and sclera also have several elements, each responsible for its own function.

Cornea

Among all the components of the eye, the cornea is unique in its structure and color (or rather, in the absence of such). It is an absolutely transparent body.

This phenomenon is due to the absence of blood vessels in it, as well as the location of the cells in the exact optical order.

There are many nerve endings in the cornea. That is why she is hypersensitive. Its functions include transmission, as well as refraction of light rays.

This shell is characterized by the possession of a huge refractive power.

The cornea smoothly passes into the sclera - the second part of which the outer shell consists.

Sclera

The shell is white, having a thickness of only 1 mm. But such dimensions do not deprive it of strength and density, because the sclera consists of strong fibers. It is thanks to this that she "withstands" the muscles that are attached to her.

Vascular or middle membrane

The middle part of the shell of the eyeball is called the vascular. It received such a name because it mainly consists of vessels of various sizes. It also includes:
1.Iris (located in the foreground).
2. Ciliary body (middle).
3. Choroid (background of the sheath).

Let's consider these elements in more detail.

iris

In the photo: the main parts and structure of the iris

This is the circle inside which the pupil is located. The diameter of the latter always fluctuates in response to the level of light: the minimum illumination causes the pupil to expand, the maximum - to narrow.

Two muscles located in the iris are responsible for the "narrowing-expansion" function.

The iris itself is responsible for regulating the width of the light beam as it enters the visual organ.

The most interesting thing is that it is the iris that determines the color of the eyes. This is due to the presence in it of cells with pigment and their number: the fewer of them, the brighter the eyes will be and vice versa.

ciliary body

The inner shell of the eyeball, or rather, its middle layer includes such an element as the ciliary body. This element is also called the “ciliary body”. This is a thickened organ of the middle shell, which visually resembles a circular roller.

It consists of two muscles:
1. Vascular.
2. Ciliary.

The first contains about seventy thin processes that produce intraocular fluid. On the processes there are so-called zinn ligaments, on which another important element is “suspended” - the lens.

The functions of the second muscle are to contract and relax. It consists of the following parts:
1. Outer meridional.
2. Medium radial.
3. Internal circular.
All three are involved in .

Choroid

The back of the shell, which is made up of veins, arteries, capillaries. The choroid nourishes the retina and delivers blood to the iris and ciliary body. This element contains a lot of blood. This is directly reflected in the shade of the fundus - due to the blood it is red.

Inner shell

The inner lining of the eye is called the retina. It converts the received light rays into nerve impulses. The latter are sent to the brain.

So, thanks to the retina, a person can perceive images. This element has a pigment layer vital for vision, which absorbs rays and thus protects the organ from excess light.

The retina of the eyeball has a layer of cell processes. They, in turn, contain visual pigments. They are called rods and cones or, scientifically, rhodopsin and iodopsin.

The active area of ​​the retina is ocular fundus. It is there that the most functional elements are concentrated - the vessels, the optic nerve and the so-called blind spot.

The latter contains the largest number of cones, thereby providing images in color.

All three shells are one of the most important elements of the organ of vision, which ensure the perception of a picture by a person. Now let's go directly to the center of the eyeball - the nucleus and consider what it consists of.

The nucleus of the eyeball

The inner core of the vowel apple consists of a light-conducting and light-refracting medium. This includes: intraocular fluid that fills both chambers, the lens and the vitreous body.

Let's analyze each of them in more detail.

Aqueous fluid and chambers

The moisture inside the eye has a similarity (in composition) with blood plasma. It nourishes the cornea and lens, and this is its main task.
The place of its dislocation is the anterior region of the eye, which is called the chamber - the space between the elements of the eyeball.

As we have already found out, the eye has two chambers - anterior and posterior.

The first is between the cornea and the iris, the second is between the iris and the lens. The link here is the pupil. Between these spaces intraocular fluid continuously circulates.

lens

This element of the eyeball is called the "crystalline lens" because it has a transparent color and a solid structure. In addition, there are absolutely no vessels in it, and visually it looks like a doubly convex lens.

Outside, it is surrounded by a transparent capsule. The location of the lens is a recess behind the iris on the anterior part of the vitreous body. As we have already said, it is “held” by zinn ligaments.

The transparent body is nourished by washing with moisture from all sides. The main task of the lens is to refract light and focus rays on the retina.

vitreous body

The vitreous body is a colorless gelatinous mass (like a gel), the basis of which is water (98%). It also contains hyaluronic acid.

In this element, there is a continuous flow of moisture.

The vitreous body refracts light rays, maintains the shape and tone of the visual organ, and also nourishes the retina.

So, the eyeball has shells, which, in turn, consist of several more elements.

But what protects all these organs from the external environment and damage?

Additional elements

The eye is a very sensitive organ. Therefore, it has protective elements that “save” it from damage. Protective functions are performed by:
1. eye socket. A bone receptacle for the organ of vision, where, in addition to the eyeball, the optic nerve, the muscular and vascular system, and the fat body are located.
2. Eyelids. The main protector of the eye. Closing and opening, they remove small particles of dust from the surface of the organ of vision.
3. Conjunctiva. Inner lining of the eyelids. Performs a protective function.

If you want to learn a lot of useful and interesting information about eyes and vision, read on.

The eyeball also has a lacrimal apparatus, which protects and nourishes it, and a muscular apparatus, thanks to which the eye can move. All this in a complex provides a person with the ability to see and enjoy the surrounding beauty.

Anatomy and physiology of the eyeball

The eyeball with its accessory apparatus is the perceiving part of the visual analyzer. The eyeball has a spherical shape, consists of 3 membranes and intraocular transparent media. These shells surround the internal cavities (chambers) of the eye filled with transparent aqueous humor (intraocular fluid) and the transparent internal refractive media of the eye (crystalline lens and vitreous body).

Outer layer of the eye

This fibrous capsule provides the turgor of the eye, protects it from external influences and serves as an attachment site for the oculomotor muscles. Vessels and nerves pass through it. This shell consists of two sections: the anterior is the transparent cornea, the posterior is the opaque sclera. The place of transition of the cornea to the sclera is called the edge of the cornea or limbus.

The cornea is the transparent part of the fibrous capsule, which is the refractive medium when light rays enter the eye. The power of its refraction is 40 diopters (dopters). There are many nerve endings in it, any mote, if it enters the eye, causes pain. The cornea itself has good permeability, is covered with epithelium and normally does not have blood vessels.

The sclera is the opaque part of the fibrous capsule. Consists of collagen and elastic fibers. Normally it is white or blue-white. Sensitive innervation of the fibrous capsule is carried out by the trigeminal nerve.

It is a choroid, its pattern is visible only with biomicro - and ophthalmoscopy. This shell consists of 3 sections:

1st (anterior) section - iris. It is located behind the cornea, between them there is a space - the anterior chamber of the eye, filled with a watery liquid. The iris is clearly visible from the outside. It is a pigmented round plate with a central hole (pupil). The color of the eyes depends on its color. The diameter of the pupil depends on the level of illumination and the work of two antagonist muscles (constricting and expanding the pupil).

2nd (middle) department - eyelash body. It I is the middle part of the choroid, a continuation of the iris. Zinn ligaments extend from its processes, which support the lens. Depending on the state of the ciliary muscle, these ligaments can stretch or contract, changing the curvature of the lens and its refractive power. The ability of the eye to see near and far equally well depends on the refractive power of the lens. The adaptation of the eye to see clearly at any distance is called accommodation. The ciliary body produces and filters aqueous humor, thereby regulating intraocular pressure, and provides accommodation due to the work of the ciliary muscle.

3rd (posterior) section - the choroid proper . It is located between the sclera and the retina, consists of vessels of different diameters and supplies the retina with blood. Due to the lack of sensitive nerve endings in the choroid, its inflammation, injuries and tumors are painless!

Inner lining of the eye (retina)

It is a specialized brain tissue, brought to the periphery. The retina provides vision. In its architectonics, the retina is similar to the brain. This thin transparent membrane lines the fundus and connects with other membranes of the eye in only two places: at the dentate edge of the ciliary body and around the optic nerve head. Throughout the rest of the length, the retina is tightly attached to the choroid, which is mainly facilitated by the pressure of the vitreous body and intraocular pressure, therefore, with a decrease in intraocular pressure, the retina can exfoliate. The distribution density of light-sensitive elements (photoreceptors) in different parts of the retina is not the same. The most important area of ​​the retina is the retinal spot - this is the area of ​​​​the best perception of visual sensations (a large accumulation of cones). In the central part of the fundus there is an optic disc. It is visible in the fundus through the transparent structures of the eye. The area of ​​the optic disc does not contain photoreceptors (rods and cones) and is the "blind" area of ​​the fundus (blind spot). The optic nerve passes inside the orbit through the optic nerve canal, in the cranial cavity in the region of the optic chiasm, a partial intersection of its fibers is carried out. The cortical representation of the visual analyzer is located in the occipital lobe of the brain.

Transparent intraocular media necessary for the transmission of light rays to the retina and their refraction. These include the chambers of the eye, the lens, the vitreous body, and aqueous humor.

Anterior chamber of the eye. It is located between the cornea and the iris. In the angle of the anterior chamber (iriocorneal angle) is the drainage system of the eye (helmet canal), through which aqueous humor flows into the venous network of the eye. Violation of the outflow leads to an increase in intraocular pressure and the development of glaucoma.

Posterior chamber of the eye. It is bounded anteriorly by the posterior surface of the iris and the ciliary body, and the lens capsule is located posteriorly.

lens . This is an intraocular lens that can change its curvature due to the work of the ciliary muscle. It does not have vessels and nerves, inflammatory processes do not develop here. Its refractive power is 20 diopters. It contains a lot of protein, during the pathological process, the lens loses its transparency. A clouding of the lens is called a cataract. With age, the ability to accommodate may deteriorate (presbyopia).

vitreous body . This is the light-conducting medium of the eye, located between the lens and the fundus of the eye. This is a viscous gel that provides turgor (tone) to the eye.

Aqueous moisture. The intraocular fluid fills the anterior and posterior chambers of the eye. It is 99% water and contains 1% protein fractions.

Blood supply to the eye and orbit carried out at the expense of the ophthalmic artery from the pool of the internal carotid artery. Venous outflow is carried out by the superior and inferior ophthalmic veins. The superior ophthalmic vein carries blood to the cavernous sinus of the brain and anastomoses with the veins of the face through the angular vein. The veins of the orbit do not have valves. Consequently, the inflammatory process of the skin of the face can spread into the cranial cavity. Sensitive innervation of the eye and tissues of the orbit is carried out by 1 branch of the 5th pair of cranial nerves.

The eye is the light-perceiving part of the visual tract. The nerve endings of the retina (rods and cones) that receive light are called photoreceptors. Cones provide visual acuity, and rods provide light perception, i.e. twilight vision. Most of the cones are concentrated in the center of the retina, and most of the rods are on its periphery. Therefore, a distinction is made between central and peripheral vision. Central vision is provided by cones and is characterized by two visual functions: visual acuity and color perception - color perception. Peripheral vision is the vision provided by rods (twilight vision) and is characterized by the field of view and light perception.

The main function of the choroid is to provide nutrition to the four outer layers of the retina, including the layer of rods and cones, as well as to remove metabolic products from the retina back into the bloodstream. The layer of capillaries is delimited from the retina by a thin Bruch's membrane, the function of which is to regulate the metabolic processes between the retina and the choroid. In addition, the perivascular space, due to its loose structure, serves as a conductor for the posterior long ciliary arteries involved in the blood supply to the anterior segment of the eye.

The structure of the choroid

The perivascular or perichoroidal space is a narrow gap between the inner surface of the sclera and the vascular plate, which is pierced by delicate endothelial plates. These plates connect the walls together. However, due to the weak connections between the sclera and the choroid in this space, the choroid is quite easily exfoliated from the sclera, for example, during intraocular pressure drops during operations for glaucoma. In the perichoroidal space, two blood vessels pass from the posterior to the anterior segment of the eye - long posterior ciliary arteries, accompanied by nerve trunks.
The supravascular plate consists of endothelial plates, elastic fibers and chromatophores - cells containing dark pigment. The number of chromatophores in the layers of the choroid in the direction from the outside to the inside rapidly decreases, and they are completely absent in the choriocapillary layer. The presence of chromatophores can lead to the appearance of choroidal nevi and even the most aggressive malignant tumors - melanomas.
The vascular plate has the form of a brown membrane, up to 0.4 mm thick, and the thickness of the layer depends on the degree of blood filling. The choroid plate consists of two layers: large vessels lying outside with a large number of arteries and vessels of medium caliber, in which veins predominate.
The vascular-capillary plate, or choriocapillary layer, is the most important layer of the choroid, ensuring the functioning of the underlying retina. It is formed from small arteries and veins, which then break up into many capillaries that pass several red blood cells in one row, which makes it possible for more oxygen to enter the retina. The network of capillaries for the functioning of the macular region is especially pronounced. The close connection of the choroid with the retina leads to the fact that inflammatory diseases, as a rule, affect both the retina and the choroid together.
Bruch's membrane is a thin plate consisting of two layers. It is very tightly connected to the choriocapillary layer of the choroid, and is involved in regulating the flow of oxygen into the retina and metabolic products back into the bloodstream. Bruch's membrane is also associated with the outer layer of the retina - the pigment epithelium. With age and in the presence of a predisposition, there may be a dysfunction of a complex of structures: the choriocapillary layer, Bruch's membrane and pigment epithelium, with the development of age-related macular degeneration.

Methods for diagnosing diseases of the vascular membrane

• Ophthalmoscopy.
• Ultrasound diagnostics.
• Fluorescent angiography - assessment of the state of the vessels, damage to the Bruch's membrane, the appearance of newly formed vessels.

Symptoms in diseases of the choroid

• Choroid coloboma - the complete absence of the choroid in a certain area.

• Vascular dystrophy.
• Inflammation of the choroid - choroiditis, but more often combined with damage to the retina - chorioretinitis.
• Detachment of the choroid, with intraocular pressure drops during abdominal operations on the eyeball.
• Ruptures of the choroid, hemorrhages - most often due to eye injuries.
• Nevus of the choroid.
• Tumors of the choroid.

Performing a transport function, the choroid of the eye supplies the retina with blood-borne nutrients. It consists of a dense network of arteries and veins that are closely intertwined with each other, as well as loose fibrous connective tissue rich in large pigment cells. Due to the fact that there are no sensitive nerve fibers in the choroid, the diseases associated with this organ proceed painlessly.

What is it and what is its structure?

The human eye has three membranes that are closely related, namely the sclera, choroid or choroid, and retina. The middle layer of the eyeball is an essential part of the organ's blood supply. It contains the iris and the ciliary body, from which the entire choroid passes and ends near the optic nerve head. Blood supply occurs with the help of ciliary vessels located posteriorly, and outflow through the vorticose veins of the eyes.

Due to the special structure of the blood flow and the small number of vessels, the risk of developing an infectious disease of the choroid increases.

An integral part of the middle layer of the eye is the iris, which contains a pigment located in the chromatophores and is responsible for the color of the lens. It prevents direct rays of light from entering, and the formation of glare in the inside of the organ. In the absence of pigment, the clarity and clarity of vision would be significantly reduced.

The vascular membrane consists of the following components:

The shell is represented by several layers that perform certain functions.

• Perivascular space. It has the appearance of a narrow slit located near the surface of the sclera and the vascular plate.
• supravascular plate. Formed from elastic fibers and chromatophore. More intense pigment is located in the center and decreases on the sides.
• Vascular plate. It has the appearance of a brown membrane and a thickness of 0.5 mm. The size depends on the filling of the vessels with blood, since it is formed upward by the layering of large arteries, and downward by medium-sized veins.
• Choriocapillary layer. It is a network of small vessels that turn into capillaries. Performs functions to ensure the operation of the nearby retina.
• Bruch membrane. The function of this layer is to allow oxygen to enter the retina.

Functions of the choroid

The most important task is the delivery of nutrients with blood to the layer of the retina, which is located outward and contains cones and rods. The structural features of the shell allow you to remove metabolic products into the bloodstream. Bruch's membrane limits the access of the capillary network to the retina, as metabolic reactions take place in it.

Anomalies and symptoms of diseases

Choroidal coloboma is one of the anomalies of this layer of the visual organ.

The nature of the disease can be acquired and congenital. The latter include anomalies of the choroid proper in the form of its absence, the pathology is called choroidal coloboma. Acquired diseases are characterized by dystrophic changes and inflammation of the middle layer of the eyeball. Often, in the inflammatory process of the disease, the anterior part of the eye is captured, which leads to partial loss of vision, as well as minor retinal hemorrhages. When performing surgical operations for the treatment of glaucoma, there is a detachment of the choroid due to pressure drops. The choroid can undergo ruptures and hemorrhages when injured, as well as the appearance of neoplasms.

Anomalies include:

• Polycoria. The iris contains several pupils. The patient's visual acuity decreases, he feels discomfort when blinking. Treated with surgery.
• Corectopia. Pronounced displacement of the pupil to the side. Strabismus, amblyopia develops, and vision is sharply reduced.