Department of General HistologyDepartment of General Histology

Practical lessonPractical lesson

TopicTopic: : Sensory organs

Sensory organssense organ. What it's mean? The sense organs are the peripheral parts of the analyzers. They are in communication with the central nervous system of external and internal environment.

Sensory Analyzer Analyzer. Analyzer. What it's mean? Every analyzer consist three parts: the peripheral part of

the analyzer, where the perception (reception) is present. (example - organ of taste, organ of vision) an intermediate part formed by the conductive paths and subcortical structures, and a central part - plot of the cerebral cortex, where the analysis and synthesis of the final of perceived sensations.

What types of sensory organs do you know?What types of sensory organs do you know? Due to the peculiarities of the development, structure and

functions we know the three types of sensory organs 1. the first type includes the organ of vision and the organ of

smell, are pawned in embryogenesis as part of the neural plate. 2. The second type is the organ of taste, balance and hearing.

These organs are laid in the embryogenesis of the thickened ectoderm - placode.

3. The third type is a group of sensory receptor endings (eg, tactile, lamellar bodies), which are the peripheral parts of the corresponding analyzers (touch, pressure, etc.).

Sensory receptorsSensory receptors

Eye structure (membranes)Eye structure (membranes) The eyeball has three membranes: the outer - fibrous, middle - vascular,

internal - retina. The fibrous membrane is opaque (not transparent ) and is called the sclera. In front of the eyeball, it goes into a convex transparent cornea.

Eye structure (membranes)Eye structure (membranes) Medium membrane has blood vessels and pigment cells. In front of the

eye, it thickens to form the ciliary body, inside of which is the ciliary muscle. It shrinking and changes the curvature of the lens.

Eye structure (membranes)Eye structure (membranes) The innermost membrane of the eye - the retina containing the rods and The innermost membrane of the eye - the retina containing the rods and

cones - the light-sensitive receptors, representing the peripheral part of the cones - the light-sensitive receptors, representing the peripheral part of the visual analyzer. In the eye of a person, there are about 130 million rods and visual analyzer. In the eye of a person, there are about 130 million rods and 7 million cones.7 million cones.

Eye structure (membranes)Eye structure (membranes) In the center of the retina is focused more cones, but rods are

located on the periphery around cones. From the light-sensitive elements of the eye (rods and cones) depart nerve fibers, which, connecting through intermediate neurons and form the optic nerve.

In place of its exit eyes are no receptors, this site is not sensitive to light and is called the blind spot. Outside of the blind spot on the retina focused only cones. This area is called the yellow spot, it the largest number of cones. The rear section of the retina is the bottom of the of the eyeball

Eye structureEye structure Ciliary body becomes the iris, consisting of

several layers. Pigment cells are in the deeper layer. Eye color depends on the amount of pigment. In the center of the iris present the hole – pupil. Circular muscle are located around the pupil. Muscles contract - the pupil narrows.

CorneaCornea 1-1- 2-2- 3-3- 4-4- 5-5-

RetinaRetina 1-1-Pigment layer - consists of pigmented cells 2-2-Layer of rods and cones – consists of the external and internal segments of the rods and cones 3-3-Outside the boundary layer - Plexus T-shaped branching glial cells. 4-4-The outer nuclear layer - consists of a nucleus of photoreceptor cells. 5-5-Outer plexiform layer - the photoreceptor axons, dendrites and synapses between bipolar them 6-6-The inner nuclear layer - the core of bipolar, horizontal, amokrinnyh and glial cells. 7-7-The inner plexiform layer - axons and dendrites of bipolar ganglion cells, the synapses between them 8-8-Ganglionic layer - the core of ganglion cells. 9-9-Layer of nerve fibers - axons of ganglion cells 10-10-The internal limiting membrane - Plexus T-shaped branching glial cells.

olfactory organ

Olfactory organ is formed from the olfactory fossae are separated from the neural plate. Supporting, basal epithelial cells and neurosensory cells are formed from cells of the olfactory pits (fossae). Receptor, neurosensory cells have a short peripheral dendritic spines and long-Central - axons that make up the olfactory nerve that goes to the olfactory bulbs.

 

The inner ear: The auditory and vestibular systems are intimately connected. The receptors

for both are located in the temporal bone, in a convoluted chamber called the bony labyrinth. A delicate continuous membrane is suspended within the bony labyrinth, creating a second chamber within the first. This chamber is called the membranous labyrinth. The entire fluid-filled structure is called the inner ear.

  The inner ear has two membrane-covered outlets into the air-filled middle ear -

the oval window and the round window. The oval window is filled by the plate of the stapes, the third middle ear bone. The stapes vibrates in response to vibrations of the eardrum, setting the fluid of the inner ear sloshing back and forth. The round window serves as a pressure valve, bulging outward as pressure rises in the inner ear.

The inner ear: The oval window opens into a large central area within the inner ear

called the vestibule. All of the inner ear organs branch off from this central chamber. On one side is the cochlea, on the other the semicircular canals. The utricle and saccule, additional vestibular organs, are adjacent to the vestibule.

The membranous labyrinth is filled with a special fluid called endolymph. Endolymph is very similar to intracellular fluid: it is high in potassium and low in sodium. The ionic composition is necessary for vestibular and auditory hair cells to function optimally. The space between the membranous and bony labyrinths is filled with perilymph, which is very much like normal cerebral spinal fluid.

The transduction of sound into a neural signal occurs in the cochlea. If we were to unroll the snail-shaped cochlea, it would look like this:

The inner ear:

As the stapes vibrates the oval window, the perilymph sloshes back and forth, vibrating the round window in a complementary rhythm. The membranous labyrinth is caught between the two, and bounces up and down with all this sloshing. Now let's take a closer look at the membranous labyrinth. If we cut the cochlea in cross section, it looks like this:

The inner ear: The membranous labyrinth of the cochlea encloses The membranous labyrinth of the cochlea encloses the endolymph-filled scala media. The two the endolymph-filled scala media. The two compartments of the bony labyrinth, which housecompartments of the bony labyrinth, which house the perilymph, are called the scalae vestibuli and the perilymph, are called the scalae vestibuli and tympani. Within the scala media is the receptor organ,tympani. Within the scala media is the receptor organ, the organ of Corti. It rests on part of the membranous the organ of Corti. It rests on part of the membranous labyrinth, the basilar membrane.labyrinth, the basilar membrane.

A single turn of the cochlea has been outlined in blue.A single turn of the cochlea has been outlined in blue.

You can see the auditory nerve exiting at the base of the cochlea; it will travel through the You can see the auditory nerve exiting at the base of the cochlea; it will travel through the temporal bone to the brainstem.temporal bone to the brainstem.

The inner ear: You can see the auditory nerve exiting at the base of the cochlea; it will travel

through the temporal bone to the brainstem. The auditory hair cells sit within the organ of Corti. There are inner hair cells,

which are the auditory receptors, and outer hair cells, which help to "tune" the cochlea, as well as supporting cells. The sensitive stereocilia of the inner hair cells are embedded in a membrane called the tectorial membrane. As the basilar membrane bounces up and down, the fine stereocilia are sheared back and forth under the tectorial membrane. When the stereocilia are pulled in the right direction, the hair cell depolarizes. This signal is transmitted to a nerve process lying under the organ of Corti.

The inner ear: This neuron transmits the signal back along the auditory nerve to the brainstem.

As with almost all sensory neurons (the exception is in the retina), its cell body lies outside the CNS in a ganglion. In this case, the ganglion is stretched out along the spiralling center axis of the cochlea, and is named the spiral ganglion.

  You can see most of the structures in this higher magnification of the organ of

Corti; unfortunately, the inner hair cells have been artifactually pulled away from the tectorial membrane.

2

11

Taste buds in the papillae of the tongue histologyTaste buds in the papillae of the tongue histology