Difference between epithelial tissue and connective tissue. How does epithelial tissue differ from connective tissue: description and differences Comparative table of epithelial and connective tissue

Epithelial tissue- the outer surface of human skin, as well as the lining surface of the mucous membranes of internal organs, the gastrointestinal tract, lungs, and most glands.

The epithelium is devoid of blood vessels, so nutrition occurs due to the adjacent connective tissues, which are nourished by the bloodstream.

Functions of epithelial tissue

Main function skin epithelial tissue is protective, that is, limiting the impact of external factors on internal organs. Epithelial tissue has a multilayer structure, so keratinized (dead) cells are quickly replaced by new ones. It is known that epithelial tissue has increased restorative properties, which is why human skin is quickly renewed.

There is also intestinal epithelial tissue with a single-layer structure, which has absorptive properties, due to which digestion occurs. In addition, the intestinal epithelium tends to secrete chemicals, in particular sulfuric acid.

Human epithelial tissue covers almost all organs from the cornea of ​​the eye to the respiratory and genitourinary systems. Some types of epithelial tissue are involved in protein and gas metabolism.

The structure of epithelial tissue

Single-layer epithelial cells are located on the basement membrane and form one layer with it. Stratified epithelial cells are formed from several layers and only the lowest layer is the basement membrane.

According to the shape of the structure, epithelial tissue can be: cubic, flat, cylindrical, ciliated, transitional, glandular, etc.

Glandular epithelial tissue has secretory functions, that is, the ability to secrete secretions. The glandular epithelium is located in the intestine, making up the sweat and salivary glands, endocrine glands, etc.

The role of epithelial tissue in the human body

The epithelium plays a barrier role, protecting internal tissues, and also promotes the absorption of nutrients. When eating hot food, part of the intestinal epithelium dies and is completely restored overnight.

Connective tissue

Connective tissue– building matter that unites and fills the entire organism.

Connective tissue is presented in nature in several states at once: liquid, gel-like, solid and fibrous.

In accordance with this, they distinguish between blood and lymph, fat and cartilage, bones, ligaments and tendons, as well as various intermediate body fluids. The peculiarity of connective tissue is that there is much more intercellular substance in it than there are cells themselves.

Types of connective tissue

— Cartilaginous, there are three types:
a) Hyaline cartilage;
b) Elastic;
c) Fibrous.

— Bone(consists of forming cells - osteoblast, and destroying cells - osteoclast);

— Fibrous, in turn happens:
a) Loose (creates a frame for organs);
b) Formed dense (forms tendons and ligaments);
c) Unformed dense (the perichondrium and periosteum are built from it).

— Trophic(blood and lymph);

— Specialized:
a) Reticular (from it the tonsils, bone marrow, lymph nodes, kidneys and liver are formed);
b) Fat (subcutaneous energy reservoir, heat regulator);
c) Pigment (iris, nipple halo, anus circumference);
d) Intermediate (synovial, cerebrospinal and other auxiliary fluids).

Functions of connective tissue

These structural features allow connective tissue to perform various functions:

1. Mechanical The (supporting) function is performed by bone and cartilage tissue, as well as fibrous connective tissue of tendons;
2. Protective the function is performed by adipose tissue;
3. Transport The function is performed by liquid connective tissues: blood and lymph.

Blood ensures the transport of oxygen and carbon dioxide, nutrients, and metabolic products. Thus, connective tissue connects parts of the body to each other.

The structure of connective tissue

Most of the connective tissue is an intercellular matrix of collagen and non-collagen proteins.

In addition to it - naturally, cells, as well as a number of fibrous structures. The most important cells Fibroblasts can be called fibroblasts, which produce intercellular fluid substances (elastin, collagen, etc.).

Also important in structure are basophils (immune function), macrophages (exterminators of pathogens) and melanocytes (responsible for pigmentation).

Question 1. What tissue does the skin, walls of the oral cavity, ear and nasal cartilage consist of?

The skin and walls of the oral cavity consist of epithelial tissue, and the ear and nasal cartilages consist of connective tissue.

Questions after the paragraph

Question 1. What is called fabric?

Groups of cells and intercellular substance that have a similar structure and origin and perform common functions are called tissues.

Question 2. What fabrics do you know? Make and fill out the “Variety of Fabrics” diagram.

In the body of animals and humans, there are four main groups of tissues: epithelial, connective, muscle and nervous. In muscles, for example, muscle tissue predominates, but along with it there is also connective and nervous tissue. Tissue can consist of both identical and different cells.

Question 3. How do connective tissues differ from epithelial tissues?

Connective tissue contains cells that can fight microorganisms, and if the main tissue of an organ is damaged, this tissue is able to replace the lost elements. Thus, scars formed after injuries consist of connective tissue. True, it cannot perform the functions of the tissue that connective tissue replaced.

Question 4. What types of epithelial and connective tissue do you know?

Types of epithelial tissue: squamous epithelium, cuboidal epithelium, ciliated epithelium, columnar epithelium.

Connective tissues include supporting tissues - cartilage and bone; liquid tissues - blood and lymph, loose fibrous tissue that fills the space between organs, accompanying blood vessels and nerves; adipose tissue; dense fibrous tissue that makes up tendons and ligaments.

Question 5. What properties do muscle tissue cells have - smooth, skeletal, cardiac?

The general properties of all muscle tissues are excitability and contractility. In response to irritation, muscle tissue contracts. Thanks to contraction, all human movements and the work of his internal organs are carried out.

Question 6. What functions do neuroglial cells perform?

Neuroglial cells perform servicing functions in relation to them: protective and supportive, nutritional and electrically insulating.

Question 7. What is the structure and properties of neurons?

A neuron consists of a body and processes. The body of the neuron contains the nucleus and the main cellular organelles. Neuron processes vary in structure, shape and function.

Question 8. Compare dendrites and axons. What are their similarities and what are their fundamental differences?

Dendrite is a process that transmits excitation to the neuron body. Most often, a neuron has several short branched dendrites. However, there are neurons that have only one long dendrite.

An axon is a long process that transmits information from the neuron body to the next neuron or to the working organ. Each neuron has only one axon. The axon branches only at the end, forming short branches - terminal and.

Question 9. What is a synapse? Tell us about the principles of its operation.

Places of contact between individual neurons or between neurons and the cells they control are called synapses.

At the extended end of the axon, special vesicles - vesicles - contain a biologically active substance from the group of neurotransmitters. When a nerve impulse propagating along an axon reaches its end, the vesicles approach the membrane, integrate into it, and transmitter molecules are released into the synaptic cleft. These chemicals act on the membrane of another cell and in this way transmit information to the next neuron or cell of the controlled organ. The neurotransmitter can activate the next cell, causing it to become excited. However, there are mediators that lead to inhibition of the next neuron. This process is called inhibition.

Excitation and inhibition are the most important processes occurring in the nervous system. It is thanks to the balance of these two opposing processes that at each moment in time nerve impulses can arise only in a strictly defined group of nerve cells. Our attention, the ability to concentrate on a specific activity, is possible thanks to neurons that cut off redundant information. Without them, our nervous system would very quickly become overloaded and would not be able to function normally.

Tasks

1. Look for scars on your skin or those you know. Determine what fabric they are made of. Explain why they do not tan and differ in structure from healthy areas of skin.

Scars are made of connective tissue. These cells lack the pigment melanin, so these areas of the skin do not tan in the sun.

2. Look at samples of epithelial and connective tissue under a microscope. Using Figures 16 and 17, tell us about their structure.

The epithelial cell has a thick membrane (a small amount of intercellular substance). Connective tissue has a high ability to regenerate (the main function is performed by the intercellular substance.

3. In Figure 20, find the neuron body, nucleus, dendrites and axon. Determine in which direction the nerve impulses will go along the processes if the cell is excited.

If the cell is excited, the nerve impulse always moves from the cell body along the axon to the synapses.

4. It is known that the thoracic and abdominal cavities are separated by the diaphragm, which is involved in breathing. Does it consist of smooth or striated muscles? Hold your breath, inhale and exhale voluntarily and answer this question.

The diaphragm is formed by muscle tissue. It consists of smooth muscles.

5. There are many classifications of neurons. Some of them you already know. Using additional sources of information, suggest other classifications than those presented in the textbook.

Classification of neurons by the number of processes:

1. Multipolar neurons - neurons with numerous processes

2. Bipolar neurons - have 2 processes

3. Unipolar

a) Pseudounipolar (have 1 process, although initially they are formed as two-processes, but the bases of the processes are very close and it seems as if there is 1 process)

b) True unipolar - 1 process

Epithelial tissue, or epithelium, covers the outside of the body, lines the cavities of the body and internal organs, and forms most of the glands.

Varieties of epithelium have significant variations in structure, which depends on the origin (epithelial tissue develops from all three germ layers) of the epithelium and its functions.

However, all species have common features that characterize epithelial tissue:

1. The epithelium is a layer of cells, due to which it can protect underlying tissues from external influences and carry out exchanges between the external and internal environments; Violation of the integrity of the formation leads to a weakening of its protective properties, leading to the possibility of infection.
2. It is located on the connective tissue (basal membrane), from which nutrients are supplied to it.
3. Epithelial cells have polarity, i.e. parts of the cell (basal) lying closer to the basement membrane have one structure, and the opposite part of the cell (apical) has another; Each part houses different components of the cell.
4. Has a high ability to regenerate (recovery). Epithelial tissue does not contain intercellular substance or contains very little of it.

Epithelial tissue formation

Epithelial tissue is made up of epithelial cells that are tightly connected to each other and form a continuous layer.

Epithelial cells are always located on the basement membrane. It delimits them from the loose connective tissue that lies below, performing a barrier function, and prevents the germination of the epithelium.

The basement membrane plays an important role in the trophism of epithelial tissue. Since the epithelium is vascularless, it receives nutrition through the basement membrane from the connective tissue vessels.

Classification by origin

Depending on their origin, epithelium is divided into six types, each of which occupies a specific place in the body.

1. Cutaneous - develops from the ectoderm, localized in the oral cavity, esophagus, cornea, and so on.
2. Intestinal - develops from the endoderm, lines the stomach, small and large intestine
3. Coelomic - develops from the ventral mesoderm, forms serous membranes.
4. Ependymoglial - develops from the neural tube, lining the cavities of the brain.
5. Angiodermal - develops from mesenchyme (also called endothelium), lines blood and lymphatic vessels.
6. Renal - develops from the intermediate mesoderm, found in the renal tubules.

Features of the structure of epithelial tissue

According to the shape and function of the cells, the epithelium is divided into flat, cubic, cylindrical (prismatic), ciliated (ciliated), as well as single-layer, consisting of one layer of cells, and multilayer, consisting of several layers.

Single layer

Single layer flat the epithelium is formed by a thin layer of cells with uneven edges, the surface of which is covered with microvilli. There are mononuclear cells, as well as with two or three nuclei.

Single layer cubic consists of cells with the same height and width, characteristic of the excretory duct of the glands. Single-layer columnar epithelium is divided into three types:

1. Bordered - found in the intestines, gall bladder, has adsorbing abilities.
2. Ciliated - characteristic of the oviduct, in the cells of which at the apical pole there are movable cilia (promote the movement of the egg).
3. Glandular - localized in the stomach, produces mucous secretion.

Single layer multi-row The epithelium lines the airways and contains three types of cells: ciliated, intercalated, goblet and endocrine. Together they ensure the normal functioning of the respiratory system and protect against the entry of foreign particles (for example, the movement of cilia and mucous secretions help remove dust from the respiratory tract). Endocrine cells produce hormones for local regulation.

Multilayer

Multilayer flat non-keratinizing the epithelium is located in the cornea, anal rectum, etc. There are three layers:

• The basal layer is formed by cylinder-shaped cells, they divide mitotically, some of the cells belong to the stem;
• spinous layer - cells have processes that penetrate between the apical ends of the cells of the basal layer;
• layer of flat cells - located on the outside, constantly dying and peeling off.

Multilayer flat keratinizing epithelium covers the surface of the skin. There are five different layers:

1. Basal - formed by poorly differentiated stem cells, together with pigment cells - melanocytes.
2. The spinous layer together with the basal layer form the growth zone of the epidermis.
3. The granular layer is built of flat cells, in the cytoplasm of which the keratoglian protein is located.
4. The stratum pellucida received its name because of its characteristic appearance upon microscopic examination of histological preparations. It is a uniform shiny stripe, which stands out due to the presence of elaidin in flat cells.
5. The stratum corneum consists of horny scales filled with keratin. The scales that are closer to the surface are susceptible to the action of lysosomal enzymes and lose contact with the underlying cells, so they are constantly exfoliated.

Transitional epithelium located in the kidney tissue, urinary canal, and bladder. Has three layers:

• Basal - consists of cells with intense coloring;
• intermediate - with cells of various shapes;
• integumentary - has large cells with two or three nuclei.

It is common for transitional epithelium to change shape depending on the state of the organ wall; they can flatten or acquire a pear-shaped shape.

Special types of epithelium

Acetowhite - This is an abnormal epithelium that becomes intensely white when exposed to acetic acid. Its appearance during a colposcopic examination makes it possible to identify the pathological process in the early stages.

Buccal - collected from the inner surface of the cheek, it is used for genetic testing and establishing family relationships.

Functions of epithelial tissue

Located on the surface of the body and organs, the epithelium is a border tissue. This position determines its protective function: protecting the underlying tissues from harmful mechanical, chemical and other influences. In addition, metabolic processes occur through the epithelium - absorption or release of various substances.

The epithelium that is part of the glands has the ability to form special substances - secretions, and also secrete them into the blood and lymph or into the ducts of the glands. This epithelium is called secretory or glandular.

Differences between loose fibrous connective tissue and epithelial tissue

Epithelial and connective tissue perform various functions: protective and secretory in the epithelium, supporting and transport in the connective tissue.

The cells of epithelial tissue are tightly connected to each other, there is practically no intercellular fluid. Connective tissue contains a large amount of intercellular substance; the cells are not tightly connected to each other.

The human body is a certain integral system capable of regulating itself independently and periodically recovering if necessary. This system, in turn, is represented by a large set of cells.

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

Tissue is the union of all cells found in the human body and non-cellular substances that are similar to each other in the functions they perform, appearance, and formation.

Epithelial tissue, better known as epithelium, is the tissue that forms the basis of the surface of the skin, serous membrane, cornea of ​​the eyeball, digestive, genitourinary and respiratory systems, genital organs, and 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.
• Equipped with a stratum corneum.
• Single-layer, equipped with villi (renal, coelomic, intestinal epithelium).

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

1. Gas exchange occurs through the epithelium in the alveoli of the lungs.
2. The process of urine secretion occurs from the renal epithelium.
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 types of damage. In the human body, a huge number of glands are created from a similar base.

Epithelial tissue is formed from:

• Ectoderm (covering the cornea of ​​the eye, oral cavity, esophagus, skin).
• Endoderm (gastrointestinal tract).
• Mesoderm (organs of the genitourinary 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.
2. The epithelium is known for its restorative properties; the integrity of the damaged layer is fully regenerated after a certain period of time.
3. The cellular basis of tissues have their own polarity of structure. It is associated with the apical and basal parts of the cell body.

Within the whole layer between neighboring cells, communication is formed quite often with the help of desmos. Desmos are 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.

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 stationary cells called:

• Fibrocytes.
• Fibroplasts.

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

Connective tissue is divided into:

• Embryonic- is formed in the mother's 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 participates in the formation of antibodies; this is facilitated by its content in the organs of the lymphatic system.
• Interstitial- supporting tissue of organs, it fills the gaps between the internal organs in the human body.
• Elastic– located in tendons and fascia, contains a huge amount of collagen fibers.
• Fatty– aimed at protecting the body from heat loss.

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

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. Connective tissue has a more pronounced intercellular substance.
3. Connective tissue is presented in 4 types: fibrous, gel-like, hard and liquid, epithelial in the 1st layer.
4. Epithelial cells resemble cells in appearance; in connective tissue they have an elongated shape.