Receptor apparatus of eye. Retina. Photoreceptor cells. Auxiliary apparatus of eye

There are three basic functional apparatus in eyeball:

7. Dioptric apparatus or photo - refracting. It includes cornea, fluid of anterior and posterior chambers of eye, lens and vitreous body.

8. Accommodation apparatus (or adaptation), which includes of iris, ciliary body with ciliary stria.

9. Receptor apparatus is retina.

Receptor apparatus is retina.

Retina is inner layer of eye. It contains photoreceptor cells. There are the following layers in retina:

1. photosensor layer of rods and cones

2. external nuclear layer

3. external reticular layer

4. internal nuclear layer

5. internal reticular layer

6. ganglious layer

7. 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.

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. General morphofunctional characteristic. Cellular composition of olfactory epithelium. Organ of taste. General morphofunctional characteristic. Taste buds, their cellular composition.

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.

Organ of taste - peripheral part of the gustatory receptor analyzer presented epithelial cells in taste buds. They perceive taste stimuli, generates and transmits receptor potential afferent nerve endings in which there are nerve impulses. The information comes in the subcortical and cortical centers. With the participation of the sensor system also provided some vegetative reactions, behavioral responses to foraging, etc. taste buds are located in the stratified squamous epithelium of the side walls circumvallate, mushroom and leaf buds of human language. The number of taste buds a person reaches 2000. The source of the cells of taste buds is embryonic stratified epithelium papillae.