It provides change of shape and refracting force of lens, focus of image in retina and also adaptation of eye to intensity of light.
Iris is discoid formation with aperture (pupil) at the center. The iris is composed of a stroma of connective tissue containing numerous pigment cells, blood vessels and smooth muscles. Iris muscles are sphincter pupil and dilator pupil. Number of pigment cells provides color of eye.
There are 5 layers in iris:
anterior epithelium
external limiting layer
vascular layer
internal limiting layer
posterior pigment layer
Ciliary body is thicken anterior parcel of vascular layer. It is divided into two parts: inner ciliary corona and outer ciliary ring. From the surface of the ciliary corona to lens ciliary processes pass. Basic part of ciliary body is made by ciliary muscle. It consists of smooth muscular cells. The ciliary muscle is responsible for producing alterations in the convexity of the lens (through the suspensor ligament) enabling the eye to see objects at varying distances from it. In other words the ciliary is responsible for accommodation.
Epithelial cells covering ciliary body and processes take part in formation of watery moisture, which fills chambers of eye.
Receptor apparatus is retina.
Retina is inner layer of eye. It contains photoreceptor cells. There are the following layers in retina:
photosensor layer of rods and cones
external nuclear layer
external reticular layer
internal nuclear layer
internal reticular layer
ganglious layer
layer of optic nerve fibres
Photoreceptor cells depending on shape of their peripheral processes are rods and cones. There are 6-7 million cones in human retina. The cones respond best to bright light (photopic vision). Cones contain optic pigment iodopsin. They are responsible for sharp vision and for discrimination of color. The rods are far more numerous. Their number is more than 100 million. Rods contain optic pigment rhodopsin, consisting of protein opsin and of aldehyde of vitamin A - retinal. Rods can respond to poor light (twilight vision) and especially to movement across the field of vision.
In the internal nuclear layer of retina associative neurons of three types are located: horizontal, bipolar and amacrine nerve cells.
Neuroglia of retina represents gliocytes located in the internal folium of retina, processes of gliocytes separate retina from vitreous body.
The most external layer of retina is pigmented layer. Number of pigment cells in human being is varied from 4 to 6 million. Microvilli of pigmentocytes branch photoreceptor cells. Melanosomes present in processes of pigmentocytes promote absorption of 85-90% of light passing into eye, this increases allowing ability of eye.
On the internal surface retina of eye round or oval yellow macula is present, its diameter is 2 millimeters. Deep center of this formation is called central fossa. Central fossa is place of the best perception of visual irritations.
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Inside of yellow macula on the retina eminence is present, formed by optic nerve. It is blind spot (macula), all the layers of retina are absent, except layer of nerve fibres.
Morph-functional changes of eye depending on intensity of light.
Light-sensory part of retina reacts for change of light. During this melanosomes pass into apical processes of pigmentocytes, which surround neurosecretory cells. During darkness melanosomes pass from microvilli to cytoplasm of pigmentocytes. Passing of melanosomes is realized with the help of microfilaments.
Auxiliary apparatus of eye
These are ocular muscles, eyelids, and lacrimal apparatus.
Eyelids have anterior skin surface and posterior conjunctiva, in the thickness of eyelids annular muscle is present. External surface of eyelids has structure of skin, it is covered by hairs and contains sebaceous glands.
Lacrimal apparatus consists of lacrimal glands, lacrimal sac, and lacrimal nasal duct.
Lacrimal glands consist of compound alveolar-tubular glands of serous character. Lacrimal fluid contains lysocim, which is bactericide.
Lacrimal sac and lacrimal nasal duct are lined by two-lined epithelium, into lacrimal sac tubular branched glands are opened.
OLFACTORY ORGAN
It represents limiting part of mucosa of nose, by olfactory region. Its development is similar to that of eye ball. It is founded in common embryonal nerve lamina. In a moment of separating from nerve lamina rudiments of olfactory organ are seen as paired olfactory fossa. From the walls of olfactory fossa supporting epitheliocytes and neurosensory olfactory cells are formed.
Structure
Olfactory layer consists of 3 types of cells:
olfactory neurosensory cells,
supporting,
basal epitheliocytes.
Olfactory cells are located between supporting cells, number of these cells in human being reaches 6 million. Dendrites of olfactory cells are finished as olfactory mace, which contain olfactory cilia. These cilia can contract under the action of smell substances. Central processes make up optic nerve and are directed to olfactory bulbs of brain.
Supporting epitheliocytes form layer of cells in which olfactory cells are located. They have high level of metabolism and contain yellow pigment that is why olfactory region is yellow.
Basal epitheliocytes lie onto basal membrane. Their cytoplasmic processes surround central processes of olfactory cells. Basal epitheliocytes are source of regeneration of receptor cells. At the expense of glands, which are present in loose fibrous connective tissue of olfactory region and of secretion of supporting epitheliocytes, the surface of olfactory region is wet. It is necessary for functioning of olfactory cells.
Senses.
Plan of the lecture:
1. The concept of analyzers. Classification of the senses.
2. The body of sources of development, histological structure.
3. The body smell. Sources of development, structure, function.
4. The organ of hearing and balance. Sources of development, structure and cytophysiology organ of hearing and balance.
The human body, like any living open system, constantly on-menivaetsya substances to the environment. The body receives req-sary for vital nutrients, oxygen, and the body cleans metabolism in tissues. But for the normal functioning of a living system, it is not enough. Must also constant-receipts of the system information about the state of the environment, as well as the states-Research Institute of the internal environment. Living organism receives this information through the senses.
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For further processing, analysis and use of infor- mation-senses are part of the system analyzers. Analyzers - a complex structural-functional systems that communicate with the central nervous system of external and internal environment. Each analyzer distinguished:
1. The peripheral part - where the reception, perception. Peripheral-lic the analyzer shows just senses.
2. The intermediate part - pathways, subcortical part of the CNS.
3. The central part - presented korkovymy centers analyzers. Obes-vides an analysis of the information received, the synthesis of perceived sensations, the production of adequate environmental conditions and internal environment of the responses.
Genetic and morphological and functional characteristics senses can be grouped as follows:
Group I - senses of developing neural plate and having in its composition primary sensory receptor cells neurosensory. Pervichnochuvstvitelnye - stimulus affects A direct-tively to the receptor cells, which responds by generating nerve-pulse. This group includes the organ of vision and olfactory organ.
Group II - senses, emerging from the thickening of the ectoderm (placode) and having in its composition as a receptor elements sensoepitelial-nye cells that respond to the impact of the stimulus in the transition state of arousal (change in electric potential difference between the internal-it and the outer surface tsitolemmy). Excitation sensoepitelialnyh cells trapped in contact with her and these dendrites neurocyte neurocytes generate nerve impulses. These neurocytes vtorichnochuvstvi-tional - stimulus acts on them through an intermediary - sensoepiteliotsi-ta. Group II includes organ of taste, hearing and balance.
Group III - grupa encapsulated and unencapsulated receptor-rings and those entities. Group III feature is the lack of clearly-expressed zhennoy organ isolation. They are part of the various organs - the skin, muscles, tendons, internal organs, etc. By Grupe III are orga-us touch and muscle-kinetic sensitivity.
The organ of vision.
Sources of development: the neural tube, the mesenchyme (with the addition evicted from the ganglion cells of neuroectodermal origin of the plate), ecto-dermis.
Bookmark begins at the beginning of the third week of embryonic development in the form of eye holes in the wall even in an open neural tube in the future of this LP-HN 2 holes protrude from the wall of the eye vesicle diencephalon. Eye bubbles are connected to the brain by means of an intermediate eye stalks. The front wall of bubbles and bubbles invaginates pre-rotate in the double-walled eye glasses.
At the same time the ectoderm opposite eye vpyachivayas bubbles form the lens vesicle. Epithelial rear hemisphere Dotterel-kovogo bubble is extended and converted into long-ry transparent structure - lens fibers. In the lens fibers synthesized pro-transparent fiber - crystallin. Later in the lens fibers cells organelles disappear core shrivel and disappear. In this way a lens - a kind of elastic lens. From the front of the lens ectoderm forms the front corneal epithelium.
The inner layer 2 wall of the optic cup differentiates into set-Kamchatka, takes part in the formation of the vitreous body, and the outer layer forms the pigment layer of the retina. Material edge of the optic cup with mesenchyme involved in the formation of
iris.
From the surrounding mesenchyme formed choroid and sclera, Qili-ary muscle own stuff and rear corneal epithelium. Mesenchyme also participates in the formation of vitreous iris.
Structure of the organ of vision.
The eyeball has three shells: fibrous (outermost), vascular (average), the retina (inner).
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I. The outer shell - fibrous, represented by the cornea and sclera. Rogo-Vitsa - front transparent part of the fibrous sheath. Consists of layers:
1. Front epithelium - stratified squamous epithelium neorogovevayuschy on the basal membrane, has a lot of sensitive nerve endings.
2. The front plate boundary (Bowman's membrane) - Number of the finest lagenovyh fibrils in the base material.
3. The proper substance of the cornea - formed lying one above the other plates of collagen fibers between the plates are fibroblasts ists and amorphous transparent base material.
4. Rear limiting membrane (membrane Distsementova - collagen fib-Rill in the basic substance.
5. Rear epithelium - endothelium to the basement membrane.
The cornea has no blood vessels of their own, the power - due to vascular limb and VLA-gi of the anterior chamber of the eye.
II. Sclera - unformed dense fibrous SDT. Consists of collagen fibers in a smaller amount of elastic fibers, fibroblasts are prime. Provides strength and acts as a capsule body.
III. Choroid - a loose SDT with a large-tion containing blood vessels, melanocytes. In front of about vascular-hull goes into the ciliary body and iris. Net provides power-ki.
IV. Retina - the inner membrane of the eye; consists of a thin layer of pigment-cells that is adjacent to the middle choroid and svetovosprinimayuschego thicker layer.
Svetovosprinimayuschy layer Net-ki from the physiological point of view, is a 3-link chain neurocyte:
The first link - the photoreceptor cells (palochkonesuschie and kolbochkonesuschie neurosensory cells). Photoreceptor cells perceive light time-irritation, generate nerve impulses and transmit the 2nd link.
The second link is an associative true bipolar neurocyte-mi. Third link consists of ganglion cells (neurocytes multipolar), whose axons going to the beam form the optic nerve and leave the eye-tion of an apple.
In addition to these neurocyte forming z-x link chain, a light-vosprinimayushem layer of the retina are braking neurocytes:
1. Horizontal neurocytes - inhibit the transmission of nerve impulses at the level of not-synapses between photoreceptors and bipolar.
2. Amokrinnye neurocytes - inhibit impulse transmission at the synapses between bipolar and ganglion cells.
The quantitative ratio of cells in the x-z chain links: most cells of the 1st level, the cells of the 2nd level less even smaller cells 3rd zvna, ie as we move along the chain of nerve impulse is concentrated.
Neurocyte between the retina are gliocytes long voloknopodob-governmental processes of penetrating the entire thickness of the retina. Long processes glial cells at the end of the T-shaped branch. T-shaped branching-swam openly with each other form a continuous membrane (outer and inner limiting membrane in).
Photoreceptor ultrastructure neurocyte. Under electron microscopy-pom in palokovyh and neurosensory cells of cone-ing to distinguish the following parts:
1. The outer segment - rod-shaped cells of the outer neurosensory seg-ment is covered by a continuous membrane on the outside, inside of each other are stacked flattened disks; in disks contain visual pigment Rhodope-hsing (opsin protein coupled aldehyde of vitamin A - retinal); a number of cask neurosensory cells outer segment consists of half-disks, inside which contains the visual pigment Photopsin.
2. Liaison Unit - loaned section contains several cilia.
3. The inner segment - contains mitochondria, EPS, enzyme systems. In addition kolbochnovyh cells in the inner segment contains a lipid-ing body.
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4. perikaryons - nucleated portion of rod-shaped and cone cells.
5. Axon photoreceptor cells.
Functions: Rod neurosensory cells provide black-and-white (sous-merechnoe) vision of cone - color vision.
In histological slides retinal layers are distinguished 10:
1. The pigment layer - consists of pigment cells.
2. A layer of rods and cones - consists of external and internal segments of the hulls of the pas and cones.
3. The outer boundary layer - Plexus T-shaped branching gliotsi-ing.
4. The outer nuclear layer - consists of a photoreceptor cell nuclei.
5. The outer plexiform layer - the axons of the photoreceptors, bipolar dendrites and synapses between them.
6. The inner nuclear layer - the core bipolar, horizontal, amokrinnyh and glial cells.
7. The inner plexiform layer - bipolar axons and dendrites of ganglion cells, synapses between them.
8. Ganglion cell layer - the core of ganglion cells.
9. Nerve fiber layer - the axons of ganglion cells.
10. Inner limiting membrane - Plexus T-shaped branching glial cells.
Retin-A has no own vessels, power is supplied through the diffuse layer of pigment cells of the blood vessels of the choroid. When "detachment set-Kamchatka" breaks down food, which leads to the death of retinal neurocytes, ie to blindness.
Olfactory organ - is classified as Group I of the senses, ie, develops from the neural plate and has pervichnochuvstvuyuschie neuro-sensory cells. From the neural plate at the cranial end of the separated cell material in the form of a 2-olfactory pits, these cells move in the nasal turbinates and differentiate into olfactory neurosensory, expressed support for the cells of the olfactory epithelium and secretory cells Obon-enforcement glands.
Olfactory organ olfactory epithelium is presented on the surface of the top-it and the middle turbinate. The olfactory epithelium in the structure of relative-directed to a simple pseudostratified epithelium and consists of the following cell types:
1. The olfactory neurosensory cell - I olfactory neuron paths. At the end of locally-api has a short arm toward the surface epite-lence - corresponds to the dendrite. On the surface of the olfactory epithelium Dandy-rit ends rounded bulge - olfactory mace. At the top of the mace-there are about 10 olfactory cilia (under an electron microscope - a typical cilium). In the cytoplasm of olfactory cells IME-is granular and agranular EPS mitochondria. On the basal end of the cell leaves the axon connecting to the axons of other cells form the olfactory-tional threads that penetrate through the ethmoid bone in the skull to-timid and olfactory bulb switched on body-II neurons about nyatelnogo way.
2. Supporting epithelial cells - are surrounded on all sides by olfactory neurosensory cells at the apical end have many microvilli.
3. Basal epithelial cells - cells are relatively low, are little to differentiate between cambial cells are used for regeneration of the olfactory epithelium.
Olfactory epithelium located at the basement membrane. In loose SDT olfactory epithelium located beneath the alveolar-tubular-tional olfactory glands. The secret of these glands moisten the surface of the olfactory epi-Telia, dissolves contained in the inhaled air fragrant substances to-torye irritate the cilia of olfactory neurosensory cells and neural networks-weed cells generate nerve impulses.
Organ of hearing consists of the outer, middle and inner ear. We discuss in detail below, in the structure of the inner ear only. In human embryonic organ of hearing and balance are laid together, from the ectoderm. Thickening of the ectoderm forms - auditory placode, which soon turns into a slu-hovuyu hole, and then in the auditory vesicle and detached from the ectoderm and shipped-in is subject to the mesenchyme. Auditory vesicle inside is lined with epithelium mnogoryad nym and soon constriction is divided into two parts - one part of the fore-mated cochlear membranous labyrinth (ie, hearing aid), and from Dru-goy parts - bag, dearest and three semicircular canals (ie.e. equilibri- body-sion). In pseudostratified epithelium cell differentiation membranous labyrinth-ruyutsya sensoepitelialnye in receptor cells and supporting cells. The epithelium of the Eustachian tube connects the middle ear to the throat and middle ear epithelium develop from epithelial 1st gill pocket.
The structure of the organ of hearing (the inner ear). Receptor of the organ of hearing is within the membranous labyrinth, which is located in turn in the bony labyrinth-shaped cochlea - spiral twisted 2.5 turnover bone tube. Along the entire length of the cochlea bone is membranous labyrinth la. A cross section of the cochlea bone labyrinth has a rounded shape and the cross labyrinth has a triangular shape. The walls of the membranous labyrinth la formed in cross-section:
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a) The base of the triangle - the basilar membrane (lamina) consists of individual on-stretched string (fibrillar fibers). The length of the string increases in the direction from the base to the apex of the cochlea. Each string is capable of reso-ordinated on a well-defined frequency oscillations - the strings closer to the base of the cochlea, the NIJ (shorter strings) resonate at a higher frequency of co-oscillations (at a high-pitched sounds), the strings closer to the apex of the cochlea - to lower the oscillation frequency (for lower sounds).
b) the outer wall - formed vascular strip lying on the spiral ligament. Vascular strip - is pseudostratified epithelium, having unlike all epithelia of the body's own blood vessels; the epithelium secretes endolymph that fills the membranous labyrinth.
c) verhnemedialnaya wall - formed vestibular membrane covered with endothelium outside, from the inside - a single layer of squamous epithelium.
The space of the bone above vestibular cochlear membrane called the vestibular stairs below the basilar membrane - a drum-flattering Tsey. Vestibular and scala tympani perilymph filled and faith-Huschke bone snail communicate with each other. At the base of the cochlea vestibular bone ladder ends oval opening closed-Streit Mechka and tympani - a round hole, closed elastic membrane.
Receptor of the organ of hearing is called the spiral body or core-Tieva body and is located on the basilar membrane. Spiral (Korean-Tieva) body consists of the following elements:
1. Sensory hair epithelial cells - cells with slightly elongated zakrug-lennym base at the apical end have microvilli - stereotsi-Lee. To the base of the sensory hair cells fit and form synaptic-sy dendrites 1-x neuronal auditory pathway whose bodies lie in the interior of cost-foot rod - bone spindle snail in the spiral ganglia. Sensory hair epithelial cells are divided into internal and external pear-shaped prisms. Outer hair cells form a 3-5 series, and INT-nal - only 1 row. Between the inner and outer hair klet kami formed tunnel of Corti. Microvilli on hair-sensor cells hangs integumentary (tectorial) membrane.
2. Supporting epithelial cells - are located on the basilar membrane and are the backbone of hair cells, supporting them.
Histophysiology spiral organ. Sound as vibrations in the air shakes ba-servant membrane, then swing through the hammer, anvil stirrup transferred; stapes through the oval window transmits vibrations in the perilymph vestibular ladder by vestibular ladder swings at the top of the cochlea bone becomes perelimfu scala tympani and down the spiral down and rests on the elastic membrane of the round holes. Vibrational-of perelimfy scala tympani causes vibration of the strings basilar membrane; basilar membrane vibrations when hair cells oscillate in the vertical direction and the hairs hurt Tector-cial membrane. Bending microvilli hair cells leads to the excitation of these cells, ie, changes the potential difference between the ext-term and the inner surface tsitolemmy that trapped nerve-chaniyami windows on the basal surface of the hair cells. In nerve endings nerve impulses are generated and transmitted to the auditory path in cortical centers.
As determined by frequency sounds are differentiated (high and low sounds)? The length of the string in the basilar membrane, changing the course of the membranous labyrinth, closer to the apex of the cochlea, the longer string. Each string is tuned to resonate at a specific frequency oscillations.
