epithelial and connective tissues. What is the difference between connective tissue and epithelial tissue

The human body is a certain integral system that can regulate itself independently and periodically recover if necessary. This system, in turn, is represented by a large set of cells.

At the cellular level, very important processes are carried out in the human body, which include metabolism, reproduction, and so on. In turn, all cells of the human body and other non-cellular structures are grouped into organs, organ systems, tissues, and then into a full-fledged organism.

A tissue is a union of all cells in the human body and non-cellular substances that are similar to each other in terms of their functions, appearance, and formation.

Epithelial tissue, better known as epithelium, is a tissue that is the basis of the surface of the skin, the serous membrane, the cornea of ​​​​the eyeball, the digestive, genitourinary and respiratory systems, the genital organs, and it also participates in the formation of glands.

This tissue is characterized by a regenerative feature. Numerous types of epithelium differ in their appearance. The fabric can be:

• Multilayer.
• Provided with a stratum corneum.
• Single layer, equipped with villi (renal, coelomic, intestinal epithelium).

Such a tissue is a border substance, which implies its direct participation in a number of vital processes:

1. Through the epithelium, gas exchange occurs in the alveoli of the lungs.
2. From the renal epithelium, the process of excretion of urine occurs.
3. Nutrients are absorbed into the lymph and blood from the intestinal lumen.

The epithelium in the human body performs the most important function - protection, it, in turn, is aimed at protecting the underlying tissues and organs from various kinds of damage. In the human body, a huge number of glands are created from a similar basis.

Epithelial tissue is formed from:

• Ectoderm (covering the cornea of ​​​​the eye, oral cavity, esophagus, skin).
• Endoderm (gastrointestinal tract).
• Mesoderm (organs of the urogenital system, mesothelium).

The formation of epithelial tissue occurs at the initial stage of embryo formation. The epithelium, which is part of the placenta, is directly involved in the exchange of necessary substances between the fetus and the pregnant woman.

Depending on the origin, epithelial tissue is divided into:

• Skin.
• Intestinal.
• Renal.
• Ependymoglial epithelium.
• coelomic epithelium.

These types of epithelial tissue are characterized by the following features:

1. Epithelial cells are presented in the form of a continuous layer located on the basement membrane. Through this membrane, epithelial tissue is saturated, which does not contain blood vessels in its composition.
2. The epithelium is known for its restorative properties, the integrity of the damaged layer after a certain time period is fully regenerated.
3. The cellular basis of tissue has its own polarity of structure. It is associated with the apical and basal parts of the cell body.

Within the whole layer between neighboring cells, the connection is formed quite often with the help of desmos. Desmos is a numerous structures of very small sizes, they consist of two halves, each of them in the form of a thickening is superimposed on the adjacent surface of neighboring cells.

The epithelial tissue has a coating in the form of a plasma membrane containing organelles in the cytoplasm.

Connective tissue is presented in the form of fixed cells, called:

• Fibrocytes.
• Fibroplasts.

Also in this type of tissue contains a large number of free cells (wandering, fat, fat, and so on). Connective tissue aims to give shape to the human body, as well as stability and strength. This type of tissue also connects the organs.

Connective tissue is divided into:

• Embryonic- formed in the womb. Blood cells, muscle structure, and so on are formed from this tissue.
• Reticular-consists of reticulocyte cells that accumulate water in the body. The tissue is involved in the formation of antibodies, this is facilitated by its content in the organs of the lymphatic system.
• Interstitial- the supporting tissue of organs, it fills the gaps between the internal organs in the human body.
• elastic- is located in the tendons and fascia, contains a huge amount of collagen fibers.
• Adipose- is aimed at protecting the body from heat loss.

Connective tissue is present in the human body in the form of cartilage and bone tissues that make up the human body.

The difference between epithelial tissue and connective tissue:

1. Epithelial tissue covers organs and protects them from external influences, while connective tissue connects organs, transports nutrients between them, and so on.
2. In the connective tissue, the intercellular substance is more pronounced.
3. Connective tissue is presented in 4 types: fibrous, gel-like, rigid and liquid, epithelial in the 1st layer.
4. Epithelial cells resemble cells in appearance; in the connective tissue they have an elongated shape.

The human body has a complex structure. It consists of various structures characterized by different levels of biological organization of living matter: cells with intercellular substance, tissues and organs. All structures of the body are interconnected, while cells with intercellular substance form tissues, organs are built from tissues, organs are combined into organ systems.

In the body, tissues are closely related morphologically and functionally. The morphological connection is due to the fact that different tissues are part of the same organs. The functional connection is manifested in the fact that the activity of different tissues that make up the organs is coordinated. This consistency is due to the regulatory influence of the nervous and endocrine systems on all organs and tissues.

Distinguish fabrics of general value and specialized. General tissues include:

epithelial or border tissues, their functions - protective and external exchange;

connective tissues or tissues of the internal environment, their functions are internal exchange, protective and supporting.

Different tissues join together to form organs. It usually consists of several types of tissues, and one of them performs the main function of the organ (for example, muscle tissue in the skeletal muscle), while others perform auxiliary functions (for example, connective tissue in the muscle). The main tissue of an organ that provides its function is called its parenchyma, and the connective tissue covering it from the outside and penetrating it in different directions is called stroma. In the stroma of the organ, vessels and nerves pass, carrying out blood supply and innervation of the organ.

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State budget educational institution
secondary vocational education in Moscow
"Medical School No. 8
Department of Health of the City of Moscow"
(GBOU SPO "MU No. 8 DZM")

Methodological development of a practical lesson

(for students)

Academic discipline: OP.02 "Human Anatomy and Physiology" Topic: "Epithelial and Connective Tissue"

Speciality: 34.02.01 Nursing Course: 2

Lecturer: Lebedeva T.N.

2015

Practical lesson

Topic: “Epithelial and

connective tissue “

Lesson objectives:

1. Learners should know:

Fundamentals of the structure and function of various types of epithelial and connective tissue.

1. Learners should be able to:

Distinguish on micropreparations, posters: varieties of single-layer, multilayer epithelium, glands, fibrous connective tissue, connective tissue with special properties, skeletal connective tissue.

Lesson timeline.

Busy plan:

Organizational part - 2 min.

1. Control of the initial level of knowledge (survey), demonstration of cells, varieties of epithelial and connective tissues, review of their functions. Assignment for independent work and

self-control - 15 min.

1. Independent work and self-control - 55 min.

3. Final control - 15 min.

1. Summing up the lesson and homework - 3 min.

Conduct method.

Practical exercise with fragments independently - search work.

Lesson equipment.

Posters, micropreparations with various types of epithelial tissue, glands, connective tissue, microscopes, “Atlas of normal human anatomy” by V.Ya. Lipchenko and others, textbooks by E.A. etc. "Anatomy".

Technological map of the theoretical lesson

Lesson progress:

MOTIVATION OF THE LESSON

The human body has a complex structure. It consists of various structures characterized by different levels of biological organization of living matter: cells with intercellular substance, tissues and organs. All structures of the body are interconnected, while cells with intercellular substance form tissues, organs are built from tissues, organs are combined into organ systems.

In the body, tissues are closely related morphologically and functionally. The morphological connection is due to the fact that different tissues are part of the same organs. The functional connection is manifested in the fact that the activity of different tissues that make up the organs is coordinated. This consistency is due to the regulatory influence of the nervous and endocrine systems on all organs and tissues.

Distinguish fabrics of general value and specialized. General tissues include:

epithelial or border tissues, their functions - protective and external exchange;

connective tissues or tissues of the internal environment, their functions are internal exchange, protective and supporting.

Various tissues, connecting with each other, form organs. It usually consists of several types of tissues, and one of them performs the main function of the organ (for example, muscle tissue in the skeletal muscle), while others perform auxiliary functions (for example, connective tissue in the muscle). The main tissue of an organ that provides its function is called its parenchyma, and the connective tissue covering it from the outside and penetrating it in different directions is called stroma. In the stroma of the organ, vessels and nerves pass, carrying out blood supply and innervation of the organ.

Baseline Control Questions

1. Cell and its main properties.
2. The main parts of the cell.
3. Cell organelles and their functions.
4. Fabric, basic types of fabrics.
5. Position and function of epithelial tissue.
6. Distinctive features of epithelial tissue.
7. Types of epithelial tissue.
8. What is mesothelium?
9. Varieties of single-layer epithelium.
10. Exo- and endocrine glands.
11. Structural features of connective tissue.
12. Connective tissue functions.
13. Types of connective tissue.
14. Types of fibrous connective tissue.
15. The main types of cells of loose connective tissue.
16. Types of connective tissue with special properties.
17. Types of skeletal connective tissue.
18. The structure and types of cartilage tissue.
19. Bone tissue and its varieties.

Task number 2

1. Using the literature recommended in paragraph 1 of task No. 1, study the structure of connective tissue and its difference from epithelial tissue. At the same time, pay attention to the following morphological features of the connective tissue:

1. it has a great variety in structure;
2. it is less rich in cells than epithelial tissue;
3. its cells are always separated by significant layers of intercellular substance, including the main amorphous substance and special fibers (collagen, elastic, reticular);
4. it, in contrast to epithelial tissue, is a tissue of the internal environment and almost never comes into contact with the external environment, internal cavities, and participates in the construction of many internal organs, combining various types of tissues with each other;
5. the physicochemical features of the intercellular substance and its structure largely determine the functional significance of the types of connective tissue.

On fig. Familiarize yourself with the connective tissue classification scheme.

1. Consider micropreparations with loose, dense unformed and formed fibrous connective tissue, reticular, adipose, cartilage and bone tissues. On a micropreparation with loose fibrous connective tissue, find (against the background of the main amorphous substance, collagen and elastic fibers) the main cells of this type of tissue and familiarize yourself with their functions:

1. fibroblasts are involved in the production of the main amorphous substance and collagen fibers; fibroblasts that have completed the development cycle are called fibrocytes;
2. poorly differentiated cells are able to transform into other cells (adventitial cells, reticular cells, etc.);
3. macrophages are capable of phagocytosis;
4. tissue basophils (mast cells) produce heparin, which prevents blood clotting;
5. plasma cells provide humoral immunity (synthesize antibodies - gamma globulins);
6. lipocytes (adipocytes) - fat cells accumulate reserve

fat;

1. pigmentocytes (melanocytes) - pigment cells contain the pigment melanin.

Loose fibrous connective tissue is present in all organs, as it accompanies the blood and lymphatic vessels and forms the stroma of many organs.

Considering micropreparations with varieties of dense fibrous connective tissue, pay attention to the fact that in an unformed dense tissue, against the background of a small number of cells, collage and elastic fibers are dense, intertwined and go in different directions, and in a formed one they go only in one direction. The first type of dense fibrous connective tissue forms a mesh layer of the skin, and the second - muscle tendons, ligaments, fascia, membranes, etc.

When studying reticular, adipose, gelatinous, pigmented tissues, note that they are all characterized by the predominance of homogeneous cells, with which the very name of connective tissue varieties with special properties is usually associated.

Next, consider the varieties of skeletal connective tissue: cartilage and bone. Cartilage tissue consists of cartilage cells (chondrocytes), located in groups of 2-3 cells, ground substance and fibers. Depending on the structural features of the intercellular substance, select 3 types of cartilage: hyaline, elastic and fibrous. Geolin cartilage forms almost all articular cartilages, cartilages of the ribs, airways, epiphyseal cartilages. Elastic cartilage forms the cartilages of the auricle, part of the auditory tube, external auditory canal, epiglottis, etc. Fibrous cartilage is part of the intervertebral discs, pubic symphysis, intraarticular discs and menisci, sternoclavicular and temporomandibular joints. Bone tissue consists of bone cells (osteocytes) immured in a calcified intercellular substance containing ossein (collagen) fibers and inorganic salts. It forms all the bones of the skeleton, being at the same time a depot of minerals, mainly calcium and phosphorus. Depending on the location of the bundles of ossein fibers, two types of bone tissue are distinguished: coarse-fibered and lamellar. In the first tissue, bundles of ossein fibers are located in different directions. This tissue is inherent in embryos and young organisms. The second tissue consists of bone plates, in which ossein fibers are arranged in parallel bundles within the plates or between them. It can be compact and spongy. Compact bone tissue mainly consists of the middle part of long tubular bones, and spongy bone tissue forms their ends, as well as short bones. In flat bones, there is both one and the other bone tissue. On the sing of the body and the end

Task number 3

1. Fill in the LDS of “epithelial tissue”
2. Fill in the LDS of “connective tissue”
3. Solve problems:

Task 1

How can one explain the high strength of stratified squamous epithelium, which remains intact (intact) even after fairly strong mechanical impacts?

Task 2

two classmates Kolya and Misha, aged 11, while sledding down a steep hill in winter, overturned and were injured: Kolya - an extensive superficial abrasion in the area of ​​​​the right knee joint and lower leg, and Misha - a deep bruised-lacerated wound measuring 2 x 0.5 cm in the region of the eminence of the thumb of the left hand. How, in your opinion, will regeneration and healing of soft tissues occur in both schoolchildren?

Task 3

Name the main cells of loose fibrous connective tissue that are actively involved in the defense of the body, and the specific functions of these cells.

Task 4

what is the macrophage system of the body and what cells belong to it?

long tubular bone, visually familiarize yourself with the structure of these two types of bone tissue.

1. Draw in the albums from fig. 4-8 on pages 22-24, 26 of Anatomy

L.F. Gavrilova and others. Some types of connective tissue: loose, dense, unformed and formed, reticular, fatty, cartilaginous and bone. You can finish the work of sketching fabrics in albums at home.

Are common

functions

General
character -
ristika

Classy -
fiction

Genetic and
morpho-function
physical types
epithelium

Varied
ty epithelium

Morpho funk -
rational
characteristic
cells

Character
located -
nuclei

Private

functions

Related quiz:

“Epithelial tissue

1. indicate which of the following functions are common functions of epithelial tissues:

a) external exchange,

b) internal exchange,

c) protective function,

d) trophic function.

1. Specify which of the following mechanisms constitute the external exchange function:

a) the accumulation of substances in the body,

b) the intake of substances into the body,

c) the synthesis of a substance,

d) excretion of substances from the body.

1. Specify which of the following characteristics are inherent in epithelial tissues:

a) the presence of intercellular substance,

b) cell layer,

c) borderline poloe / canopy,

d) the presence of blood vessels,

e) lack of blood vessels,

e) the presence of a basement membrane,

g) the absence of a basement membrane,

h) polar differentiation,

i) cell apolarity,

j) low regenerative capacity,

k) high regenerative capacity.

1. Specify which of the following epithelium belong to the group of single-layer epithelium:

a) flat

b) cubic,

c) cylindrical,

d) transitional

e) keratinizing.

1. Specify which of the following functions are inherent in stratified epithelium:

a) motor

b) secretory,

c) protective.

1. Specify which of the following secretion secretion methods characterize exocrine (1), endocrine (2), and mixed (3) glands:

a) secretion into the internal environment of the body,

b) release of the secret into the external environment.

1. Name the general functions of epithelial tissues.
2. Name the types of single-layer epithelium according to their shape.
3. Name the types of stratified epithelium.
4. What tissue always underlies the epithelial tissue?
5. List the special organelles found in epithelial tissue.

Related quiz:

" Connective tissue "

Reticular tissue

1. Specify which of the following organs includes reticular tissue:

a) muscles

b) tendons

c) skin

d) hematopoietic organs.

1. Specify which of the following components are part of the intercellular substance of the reticular tissue:

a) base material

b) basement membrane,

c) lymph

d) collagen fibers

e) reticular fibers.

1. Specify which of the following functions are performed by the intercellular substance of the reticular tissue:

a) base

b) protective,

c) contractile.

1. Specify which of the following functions is performed by the reticular tissue:

a) base

b) contractile,

c) trophic,

d) secretory,

e) protective.

Loose fibrous irregular connective tissue.

1. Specify which of the following components are part of loose fibrous irregular connective tissue:

a) basement membrane

b) cellular elements,

c) meucellular substance.

1. Specify which of the following functions are performed by loose fibrous unformed connective tissue:

a) trophic

b) participation in external exchange,

c) support

d) excretory,

e) protective.

1. Specify which of the following types of fibers are part of loose fibrous irregular connective tissue:

a) chondrins

b) reticular,

c) ossein,

d) elastic,

e) collagen.

1. Specify which of the following patterns of fiber arrangement are characteristic of loose fibrous unformed connective tissue:

a) ordered

b) disordered.

1. Specify which of the following cellular elements are part of loose fibrous irregular connective tissue:

a) fibroblasts,

b) fibrocytes,

c) leukocytes,

d) chondroblasts,

e) neurocytes,

e) macrophage histiocytes,

g) epitheliocytes,

h) plasma,

i) obese

j) reticular,

l) e!

m) pigment,

m) undifferentiated.

1. Specify which of the following functions are performed by fibroblast:

a) phagocytosis

b) production of antibodies,

c) the formation of the main substance,

d) the formation of fibers.

1. Specify which of the following functions is performed by a histiocyte-macrophage:

a) base

b) the formation of the main substance of loose fibrous unformed connective tissue,

c) protective.

1. Which of the following functions is performed by a plasma cell:

a) the formation of the main substance of loose fibrous irregular connective tissue,

b) support,

c) the production of antibodies,

d) production of proteolytic enzymes.

Dense connective tissues.

1. Specify which of the following tissues are included in the group of dense connective tissues:

a) coarse fiber

b) lamellar,

c) unformed

d) decorated.

1. Specify the localization of dense unformed (1) and dense formed (2) connective tissues in the body:

a) tendons

b) mesh layer coe / si,

c) links.

1. Specify which of the following components are part of the intercellular substance of dense connective tissues:

a) bundles of reticular fibers,

b) lymph, c) bundles of collagen fibers,

d) base material.

1. Specify which of the following functions are performed by dense connective tissues:

a) trophic

b) support,

c) protective.

cartilage tissue

1. Specify which of the following components are part of the cartilage tissue:

a) periosteum

b) perichondrium,

c) cellular elements,

d) terminal glandular sections,

e) the main substance,

e) chondrin fibers,

g) ossein fibers.

1. Specify which of the following functions is performed by cartilage tissue:

a) regenerative,

b) support,

c) trophic,

d) participation in carbohydrate metabolism,

e) protective.

1. Specify which of the following cells are part of the cartilage tissue:

a) fibroblast

b) chondroblast,

c) fibrocyte,

d) chondrocyte.

1. Specify. In which of the following structures is elastic cartilage localized?

a) ribs

b) airways

c) auricle

d) epiglottis,

e) the skeleton of the embryo,

e) cartilage of the larynx.

1. Specify which of the following characteristics are inherent in the intercellular substance of the elatic cartilage:

a) a lot of elastic fibers,

b) rich in water

c) few collagen fibers,

d) the presence of calcification sites,

e) the absence of calcification sites.

1. Indicate in which of the following structures collagen fibrous cartilage is localized:

a) meeupozv he face-to-face disks,

b) auricle,

c) symphysis of the pubic bones,

d) ribs

d) airways

e) sternoclavicular joint,

g) non-mandibular fussiness,

h) cartilage of the larynx,

i) places of transition of fibrous tissue into hyaline cartilage.

Bone

1. Specify which of the following functions are characteristic of bone tissue:

a) participation in carbohydrate metabolism,

b) support,

c) secretory,

d) participation in mineral metabolism.

1. Specify which of the following cells are part of the bone tissue:

a) fibroblast

b) osteoblast,

c) mast cell

d) osteocyte,

e) osteoclast,

e) chondrocyte,

e/s) plasma cell.

1. Specify which of the following components are part of the intercellular substance of cartilage (1) and bone (2) tissues:

a) ossein fibers

b) chondrin fibers,

c) osseomucoid,

d) inorganic salts,

e) chondromucoid,

e) glycogen.

1. Specify what types of bone plates are contained in lamellar bone tissue:

a) osteon plates,

b) closing,

c) delimiter

d) insert,

e) internal general,

e) basal,

e / s) external general.

1. Specify the nature of the location of ossein fibers in coarse fibrous (1) and lamellar (2) bone tissue:

a) orderly

b) disorderly.

1. Specify which of the following structures is used for bone growth in length (1) and width (2):

a) epiphyseal growth plate

b) periosteum.

Sample answers to the test:
"Epithelial tissue"

1. a, in
2. b, d
3. b, c, e, f, h, l
4. a B C
5. 1-6, 2-a, 3 - a, b
6. a-external exchange, b-protective (barrier)
7. a-flat, b-cubic, c-cylindrical
8. a-keratinizing, b-non-keratinizing, c-transitional
9. a connective tissue
10. a-tonofibrils, b-cilia, c-microvilli

Sample answers to the test:
“ Connective tissue ”

Reticular tissue

1. macrophages - capable of phagocytosis.
2. Plasma cells (plasma cells) synthesize antibodies - gamma globulins and provide humoral immunity.
3. tissue basophils - produce heparin, which prevents blood clotting.

Man is a biological being, the internal structure of which has features that would be useful and informative to understand. For example, inside and outside we are covered with different fabrics. And these tissues differ in structure and function, for example, epithelial tissue from connective tissue.

Epithelial tissue (or epithelium) lines the internal organs of our body, cavities and the outer layer (epidermis). Connective tissue is not so important in itself, but rather in combination with other building elements, it is present almost everywhere. The epithelium forms surfaces and walls, and connective tissues perform supporting and protective functions. It is interesting that connective tissue exists in four forms at once: solid (skeleton), liquid (blood), gel-like (cartilaginous formations) and fibrous (ligaments). The connective tissue has a highly saturated intercellular substance, while the epithelial tissue contains almost no intercellular substance.

Epithelial cells are mostly cellular, not elongated, dense. Connective tissue cells are elastic, elongated. As a result of embryonic development, the connective tissue is formed from the mesoderm (middle layer, germ layer), and the epithelium from the ectoderm or endoderm (outer or inner layer).

Findings site

1. Epithelial tissue and connective tissue perform different functions: the first is lining, the second is supporting.
2. Connective tissue in the body has a greater variety of forms.
3. Connective tissue and epithelium differ in the content of intercellular substance.
4. Basically, epithelial cells are cellular, and connective cells are elongated.
5. The epithelium and connective tissue are formed at different stages of embryogenesis (embryonic development).

Cells and their derivatives combine to form tissues. Tissue is a historically established system of cells and intercellular substance, united by origin, structure and functions. The structure and functions of tissues are studied by histology.

There are 4 types of tissues in the human body: epithelial, connective, muscle, and nervous.

Organs are formed from tissues, and one of the tissues is dominant.

The epithelium can be superficial and glandular. Accordingly, the glandular gland produces various substances and is part of various glands (recall the endocrine system from question 30). There are many types of epithelium, it is necessary to distinguish a multilayer non-keratinizing and keratinizing (see question 29 skin) epithelium. The first covers the mucous membrane of the oral cavity, esophagus, and the cornea of ​​the eye. Separate discussion deserves the transitional epithelium of the bladder and urinary tract, which changes its thickness when stretched. The epithelium of the intestinal tract plays a huge role in our body. This is the squamous columnar epithelium of the intestine. Thanks to him, parietal digestion is carried out under the action of enzymes fixed on the cell membrane.

Connective tissue is a very large group of tissues. These are bone, cartilage, connective tissue proper, blood, lymph, brown fat, pigment tissue.

Muscle tissue forms striated muscles, cardiac muscle and smooth muscle fibers. They contain myofibrils, consisting of actin and myosin, due to the sliding of myofilamins from these proteins, muscle contraction occurs.

Nervous tissue is represented by glia and neurons. Glial cells perform supporting, trophic, protective, insulating and secretory functions. There is glia (ependymyocytes) or simply ependyma that lines the ventricles of the brain and the spinal canal. The surface is covered with microvilli. It participates in the formation of cerebrospinal fluid, performs supporting and delimiting functions.

Astrocytes are the main supporting elements of the CNS. Carry out the transport of substances from the capillary bed to the neuron. Microglia are NS macrophages, possess phagocytic activity.

Oligodendrocytes - located near neurons and their processes. They are also called Schwann cells. They form the sheath of the nerve fiber (axon). Ranvier interception through 0.3-1.5 mm. The myelin sheath provides and improves the isolated conduction of nerve impulses along the axons and is involved in the metabolism of the axon. In the interceptions of Ranvier, during the passage of a nerve impulse, an increase in biopotentials occurs. Part of the amyelinated nerve fibers is surrounded by Schwann cells that do not contain myelin.

The structural and functional unit of the organs of the nervous system is a neuron with processes extending from it. The processes of the nerve cell are divided into an axon (axial process) and tree-branching dendrites. Usually several dendrites extend from the body of a neuron. Dendrites perceive excitation and conduct them to the cell body. The axon, which departs from the cell in the singular, is characterized by a uniform thickness and a regular contour. It can give off branches (collaterals) that transmit impulses from its cell body to other cells. The axon carries the nerve impulse away from the cell body. A synapse is a specialized connection between two neurons. It provides the transfer of excitation. The most common synapse is chemical, transmission is carried out with the help of a mediator - a chemical. Synapses can be axo-dendritic (between an axon and a dendrite of neurons), axo-axonal (between two axons of neurons), axosomatic (between an axon and a soma or body of neurons). There may also be axovascular synapses between the axons of the neurosecretory cells of the hypothalamus and the capillary wall, which ensure the flow of the neurohormone into the blood. There are neuromuscular synapses between the axon of a motor neuron and a skeletal muscle fiber. There may be neuro-secretory synapses between a nerve and an exocrine or endocrine gland.