Download DEPARTMENT OF HISTOLOGY AND MEDICAL BIOLOGY OF

DEPARTMENT OF HISTOLOGY AND MEDICAL BIOLOGY OF
MEDICAL TREATMENT AND MEDICAL PROPHYLACTIC FACULTIES
The theme of lecture: "SENSORY ORGANS"
for students of a course of medical prophylactic, medical treatment departments
Tashkent 2012
Lecture: Sensory Systems. Sensory organs (Organa sensuum) - 2:00
The purpose of the lecture: on the basis of the formation of the structure of
the senses will be provided with an understanding of the perception of stimuli and
transform coding of external energy (chemical), transfer centers, where the
analysis and the formation of subjective perceptions.
Basic knowledge:
The anatomical structure of the eye, ear, nose and tongue
The concept of the reflex arc, the structure of neurons and neuroglia
The structure of the synapses
The structure of biological membranes and specific receptors
Building knowledge and skills
After reading the text of the lecture the student should know:
- Light-and electron-microscopic structure of neurosensory and sensoepitelial
cells that convert the stimulus into a nerve impulse or membrane potential.
- The differences of the structure and function.
- Topography (spatial organization) of the structural elements of the body.
- The value of the senses in medicine and changes in natural and pathological
conditions.
The Plan of lecture
Organ of vision:
a) The outer shell
b) the average shell
c) The inner envelope
d) ultrastructure of photoreceptors
The organ of hearing and balance
a) the structure of the cochlear duct
b) the structure of the spiral organ
a) the structure of the vestibular apparatus
Organ of smell and taste.
Basic concepts and terms.
Questions for self-training.
References. (Literature)
Organ of vision
Organ of vision consists of:
1. Eyeball, connected with the optic nerve to the brain.
2. Oculomotor striated muscle.
3. The century.
4. Lacrimal gland.
Eyes - peripheral part of the visual analyzer. Receptor function is performed
by the rods and cones retina.
Development: The retina and optic nerve develop from the neural tube by
the formation of bubbles eye and eye stalks. Of the optic vesicle forms the optic
cup double layer, consisting of outer and inner layers. Thin outer layer consists of a
layer of cells differentiating into pigment. From the inner layer in the end there is a
multilayered retina.
Ectoderm, which is before the eye vesicle, thickens and forms a hollow lens
primordium, which is introduced into the emerging optic cup and. Corneal
epithelium is also formed from the ectoderm. From the mesoderm develop the iris,
vitreous, choroid and sclera.
Cornea - the front transparent shell, is 1 / 6 the whole outer shell eyes. There
are distinguished:
Anterior epithelium consisting of 5-6 layers of epithelial cells, permeated by free
nerve endings. Anterior basal plate boundary (Bowman's membrane).
Own substance.
Entocornea (Descemet's membrane)
"Endothelium" or posterior epithelium.
The front surface formed 1.2 layers of the squamous epithelium is moistened tear
secretion glands and conjunctival folds and dying cells. Prismatic epithelium basal
germinative permanently divided mitotically and contributes to the physiological
and reparative regeneration. Go to the basal layer adjacent 2-3 layers of polygonal
cells (thorny cells)
Structureless limiting membrane - 6.9 mm thick, transparent, homogeneous,
consists of randomly arranged collagen fibrils.
Own substance of the cornea - is about 90% of the total corneal thickness, is
composed of collagen fibers that make up the plate. In each plate the fibers are
parallel to the surface at an angle to the fibers of the adjacent plate. Collagen fibers
are immersed in a transparent matrix, which contains sulfated glycosaminoglycans.
In platelets and in between are flat dendritic cells - fibrocytes. On the periphery of
their own stuff going on in the opaque outer membrane of the eye - the sclera.
Own substance corneal blood vessels has not.
Rear - Frontier plate - Descemet's membrane - a homogeneous, glassy,
strongly refracting light membrane thickness of 5-10 microns. Consists of collagen
fibers embedded in an amorphous substance. Characteristic features of Descemet's
membrane: durability, resistance to chemicals, melts action purulent exudate in
lesions of the cornea.
"Endothelium" or posterior epithelium. It consists of a single layer of
polygonal cells low, which protect and nourish their own substance of the cornea.
Metabolism in the cornea by diffusion of nutrients from the liquid and the anterior
chamber of dense plexus of capillaries.
The lens - biconvex body, the outside is covered with a transparent capsule.
On the front surface of the capsule under a single-layered cubic epithelium, which
is towards the equator is cylindrical. As of differentiation, epithelial cells elongate,
lose their nucleus and become hexagonal lenticular fibers.
Vitreous body - a jelly-like substance that fills the cavity between the lens and
retina. Vitreous gel supported by a network of collagen fibers, consists of protein
vitreina and hyaluronic acid.
Vascular (average) of the eye.
It is located between the sclera and the retina and the iris and in front forms the
ciliary (ciliary) body.
The choroid is rich in melanocytes and consists of the following layers:
Above-vessels plate.
Vascular plate.
Vascular capillary plate.
Basal complex (Bruch's membrane).
Above-vessels plate - the outer layer, adjacent to the sclera, is formed by
loose connective tissue.
Vascular plate consists of intertwining arteries and veins, between which is
loose fibrous connective tissue, smooth muscle bundles.
Vascular capillary plate - consists of visceral capillaries or sinusoidal type.
Basal complex - a very thin plate, which separates the choroid from the
retinal pigment layer. It consists of 3 layers:
a) an outer collagen with elastic fibers;
b) collagen (fibrous), wider;
c) the cuticular - basement membrane retinal pigment epithelium.
Ciliary body - derived vascular and retinal membranes, on a section of the
form of a triangle. The basis of the ciliary body ciliary muscle, which plays an
important role in the accommodation of the eye. Its fibers pass in three mutually
perpendicular directions.
Iris - discoid formation with a hole in the center (pupil). Is derived vascular
(mostly) and reticular membranes. Located between the cornea and lens, front and
rear chamber of the eye, has 5 layers:
Anterior epithelium.
The outer boundary (avascular).
Vascular.
The inner boundary.
Pigment epithelium.
The anterior epithelium - a flat polygonal epithelium is a continuation
Niemi posterior corneal epithelium.
Outside the boundary layer - consists of ground substance in which a conConsequently the number of contained fibroblasts, melanocytes, causing eye color.
Vascular layer - consists of numerous blood vessels, loose fibrous
connective tissue and melanocytes.
Internal boundary layer - almost identical to the outer boundary layer (2).
Posterior pigment layer - the continuation of the epithelium of the retina.
Muscles that are part of the iris, expand or narrow the pupil.
Retin-A - (internal of the eye). Has visual department that going to the back
surface of the ciliary body and iris, becomes blind department.
In the visual department at the posterior edge of the optical axis of the eye retina
has a round yellow spot diameter of 2 mm. In the middle of the macula has a
central hole - the best place of vision and perception of visual stimuli (mainly
focused cones).
The retina is formed by three types of neurons and radial glia are located.
The first type is located on the outside - it's rods and cones - that is, photoreceptors.
The second type - bipolar neurons - carry out the interaction of types I and III
neurons.
The third type - ganglionic neurons - gather information from all layers of
the retina, both the vertical and lateral paths and by forming the optic nerve,
delivering a signal to the central nervous system.
In the retina, there are also horizontal and amacryn nerve cells that carry the
horizontal connections.
In the retina, 10 layers are distinguished:
Pigmentary
Rods and cones
The outer limiting membrane
Outer nuclear
The outer mesh
Inner nuclear
The inner mesh
Ganglionic
Nerve fibers
The internal limiting membrane
Pigment layer - the outer, adjacent to the membrane of Bruch's choroid layer
of the retina. It consists of a polygonal prismatic pigment cells. The apical surface
of adherent directly to the outer segments of photoreceptors, and separates them by
short and long microvilli. One pigmentotsit contact with the outer segments of
photoreceptors, 30-45; around a single rod outer segments is 7.3 pigmentocytes
processes containing melanosomes, around the rod outer segments - 30-40 long
shoots pigmentocytes. Melanosomes in sprouts absorb 85-90% of the light entering
the eye. In the darkness, the melanosomes are moved to the cytoplasm
pigmentotsitov.
Functions of the pigment epithelium:
1) optical protection and shielding from the light;
2) The transport of metabolites, salts, oxygen, etc. from the choroid to the
photoreceptors and back;
3) the phagocytic - absorbs waste disks of photoreceptors;
4) participates in the regulation of ion composition in the subretinal space.
Layer of rods and cones contain outer segments of photoreceptor cells that
absorb photons of light and begin to generate visual stimulation. It sticks in a
cylindrical shape and has a stack of flat, same round (like a coin) to 1,000 discs.
Each disc is formed at the base of the outer segment during its invagination
plasmolemma. After separation from plasmolemma each disk is a closed 2
photoreceptor membranes of 7 nm thick and separated by a narrow slit of 1 nm.
The distance between the disks 15 nm.
In rods, disks are formed throughout life (every 30-45 minutes. And
gradually move toward the apical portion of the segment). Used CDs in the apical
part of the segment are either included in cytolemma, or stand outside where
phagocytized melanocytes. In the cones outer segment varies in its length: the wide
in the middle, it tapers towards the base and the apical part. In this connection,
located under cytolemma drives have a structure like the sticks, but of unequal
diameter.
Cytolemma disc contains the visual pigment rhodopsin (in rods) and of cone
opsin (in cones, one of them iodopsin). Morphologically, the cones, which perceive
green, red or purple color can not be identified.
Quantum of light causes photolysis of pigment and hyperpolarization of the
corresponding cell.
The outer segment is connected with an internal short stalk, which has the
structure of cilia (tsiliya). In the inner segment of rods containing elongated
mitochondria, poliribosomy, tanks Golgi complex and the most granular and
smooth reticulum. In the inner segment of cone cells - lipid body surrounded by a
dense accumulation of mitochondria, a large number of tanks, the endoplasmic
reticulum (ellipsoid).
Nucleated forms of photoreceptor cell outer nuclear layer of the retina. From
the bodies of rods (110-125 million) and cones (6-7 million) depart axons that form
synapses with the dendrites of bipolar neurons, the horizontal processes of neurons.
As a result of interaction processes of photoreceptors with bipolar and horizontal
neurons formed the outer reticular layer of the retina.
Inner nuclear layer - here are the body:
a) bipolar neurons, connecting rods and cones to ganglion cells, and b) horizontal
c) amacryne neurons and d) glial cells.
Horizontal cells in 1-2 rows stacked on bipolar. A lot of their dendrites,
axons in contact with the rods and cones, axons are drawn horizontally and at a
distance, in contact with axons and photoreceptor cells, carry the effect of lateral
inhibition.
Bipolar cells interact with different rods and cones: 15-20 axons converge on
the dendrites of rod bipolar one. Bipolar axon diverge on several types of
amacryne cells that converge on the ganglionic cells. Convergence and divergence
cause increased sensitivity to a single quantum of light.
Cones converge on a bipolar ganglion neurons (indirect pathway) or directly
on the ganglion cell (straight path).
Amacryne neurons are located medially from the body and carry out the
integration of bipolar, modulation and integration of signals coming from bipolar
to ganglion cells.
The inner mesh layer - the zone of synaptic communication bipolar axons
and dendrites of ganglion cells.
Ganglionic layer - here are the body's largest retinal neurons - ganglion.
They collect electrical impulses (information) from all layers of the retina as the
vertical (photoreceptors ® bipolar ganglion cell ®) and on the lateral paths
(photoreceptors ® horizontal cells).
Layer of nerve fibers - axons of ganglion cells is formed. More than a
million amyelinate fibers leaving the retina become the optic nerve, which has a
myelin sheath.
The outer and inner limiting membrane formed by three types of glial cells
(Muller, astroglia, microglia). They are long and narrow, arranged radially. The
nuclei lie at the level of bipolar bodies.
External processes glia form microvilli, which are located between the outer
segments of rods and cones, internal processes - line the inner surface of the retina
and separate it from the vitreous.
Regeneration of the retina - the processes of intracellular physiological
regeneration of rod and cone occur throughout life.
Vascularization - the ophthalmic artery forms:
a) The retinal vascular system (the retina and optic nerve of the)
b) the ciliary system (ciliary body, iris and sclera)
Lymphatic capillaries are found only in the scleral conjunctiva.
Olfactory
The olfactory receptor before the main (olfactory organ) and vomeonazal bodies.
Anatomically, the olfactory organ covers a limited area of the mucous membrane
of the upper and middle part sinks nasal cavity and the upper part of the nasal
septum.
Vomeonasal (Jacobson) body - paired epithelial tubes located at the base of
the nasal septum, between the cartilage and the vomer.
Development: the ectoderm placodes are formed, and then maintaining epithelial
and neurosensory olfactory cells. Some of these olfactory cells, plunging into the
underlying mesenchyme to form the olfactory glands.
Structure. The main olfactory organ and vomeonazalny consist of multi-row
layer of the epithelium thickness of 80-90 microns, which distinguish the olfactory
neurosensory cells, supporting and basal epithelial cells.
Neurosensory cells are supporting epithelial cells have a peripheral (dendrite) and
central (axon) processes.
Nucleated part of the neuron occupies the middle part of the olfactory
mucosa. The distal part of the peripheral processes of neurons has a characteristic
thickening - olfactory mace - a typical mobile carrier 10.12 cilia. The basal part of
the neurons forming axon, which passes between the supporting cells. In his own
plate of mucous membrane, they are combined into bundles amyelinate olfactory
nerve. Through the opening of the ethmoid bone, they deliver pulses to the
olfactory bulb. Receptor cells vomeonasale body at the free surface has microvilli,
which unlike cilia are immobile.
Supporting epithelial cells form a pseudostratified epithelial layer. On the
apical surface of their observed numerous microvilli to 4 microns. Supporting cells
have signs amacryne secretion in the cytoplasm above the nucleus are profiles of
granular reticulum, mitochondria, Golgi complex, a brownish-yellow pigment.
Basal cells are located on the basement membrane, have a cytoplasmic outgrowths
that surround the olfactory nerve bundles, cytoplasm rich in ribosomes. Basal cells
are regarded as sources of the olfactory receptor cells.
Under the epithelium of the olfactory mucosa in the underlying loose
connective tissue are simple tubular-alveolar glands. Their end sections are lined
with myoepithelial and glandular cells. The secret of the past and supporting cells
of the olfactory cilia covers that dissolve odoriferous substances and contribute to
the perception of different odors membranes of the cilia of olfactory cells.