Epithelial tissues (epithelium) cover the surfaces of the body, line the membranes of internal organs, and form most of the glands. They are divided into integumentary and glandular. Integumentary epithelium occupy a border position in the body, separate the internal environment from the external one, and participate in the functions of absorption and excretion. The integumentary epithelium performs protective functions, protecting the body from external influences.
Building features:
1. Cells are closely adjacent to each other and lie on the basement membrane;
2. There is practically no intercellular substance between cells, they are firmly connected to each other with the help of special contacts;
3. There are no blood and lymphatic vessels in epithelial cells, nutrients and oxygen penetrate to the epithelial cells from the underlying loose connective tissue;
4. Cell change occurs due to the ability of epithelial cells to multiply rapidly (mitotic division).
Distinguish between single-layer and multilayer epithelium. In single-layer epithelium, all cells lie on the basement membrane, and in multilayer epithelium, only the lower (deep) layer is associated with the basement membrane.
glandular epithelium. Cells of the glandular epithelium perform the functions of formation (synthesis) and secretion of specific substances - secrets on the surface of the skin, mucous membranes or into the blood, lymph. These substances perform important functions in the life of the body: they protect the surface of the body, contain digestive enzymes and other biologically active substances. Glands are built from secretory cells, which are divided into two groups. There are glands of external secretion (exocrine) and glands of internal secretion (endocrine). Exocrine glands secrete their secret on the surface of the body, covered with epithelium. Exocrine glands include sweat and sebaceous glands, whose secret is secreted to the surface of the skin, as well as salivary, gastric, intestinal glands, etc., which secrete their secret to the surface of the mucous membranes of internal organs. material from the site
The endocrine glands do not have excretory ducts; their biologically active substances (hormones) enter directly into the blood of the blood capillaries that surround the glands. Endocrine glands: pituitary gland, thyroid gland, adrenal glands, etc.
There are mixed glands in the human body. For example, the pancreas consists of an exocrine part, whose secret is secreted into the lumen of the small intestine, and an endocrine part, which releases its hormones into the blood.
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On this page, material on the topics:
- human epithelial tissue. Its structure and functions
- summary of epithelial tissue
- structure and function of the epithelial tissue of a single layer
- structure of human epithelial tissue
- localization of epithelial tissue
You know that the human body, like all living organisms, has a cellular structure. The cells in it are not arranged randomly. They are connected by intercellular substance, grouped and form tissues.A tissue is a collection of cells and its intercellular substance, identical in origin, structure and performance ((nations.In the human body, tissues are divided into 4 groups: epithelial, connective, muscle and nervous.
Epithelial tissue (from the Greek.epi -on the. on top), or epithelium, forms the top layer of the skin, mucous membranes of internal organs (stomach, intestines, excretory organs, nasal and oral cavities), as well as some glands. Epithelial tissue cells are closely adjacent to each other. Thus, it performs a protective role and protects the body from harmful substances and microbes. The shape of the cells are varied: flat, tetrahedral, cylindrical, etc. The structure of the epithelium can be single-layer and multilayer. So, the outer layer of the skin is multi-layered. The top cells die off (shed off) and are replaced by inner, next ones.
Depending on the function performed, the epithelium is divided into groups (Fig. 9):
cellsglandular epitheliumsecrete milk, tears, saliva, sulfur;
ciliated epitheliumrespiratory tract retains dust and other foreign bodies with the help of mobile cilia. Hence its other name -ciliated:
integumentary epitheliumcovers our body from the outside and linesoutthree organ cavities. It can be multi-layered (on the surface of the skin and in the esophagus) and single-layered (for example, inside the renal tubules).
Functions of epithelial tissue:
1)protects underlying tissues;
2)participates in the metabolism at the initial and final stages;
3)glands, consisting of epithelium, regulate the constancy of the internal environment of orgashima, metabolism, etc.
Connective tissue (Fig. 10) is very diverse. There are many of its subspecies, at first glance, not similar to each other, but having a common property - a large amount of intercellular substance.
P.hotnovolok / plain fabric -cells are located close to each other, a lot of intercellular substance, a lot of fibers. It is located in the skin, in the walls of blood vessels, ligaments and tendons.
cartilage tissuecells are spherical, arranged in bundles. There is a lot of cartilage tissue in the joints, between the bodies of the vertebrae. epiglottis, pharynx andearThe shell is also made up of cartilage.
bone tissueIt contains calcium salts and proteins. Bone cells -osteocytes -alive, they are surrounded by blood vessels and nerves. The bones of the skeleton are entirely composed of such tissue.
Loose fibrous tissue (adipose).The fibers are intertwined with each other, the cells are located close to each other. Surrounds blood vessels and nerves, fills the space between organs, between skin and muscles. Under the skin forms a loose tissue - subcutaneous fatty tissue.
Bloodandlymph- fluid connective tissue.
Connective tissue functions:
1)gives strength to organs, forming the basis of tendons and skin (dense fibrous tissue);
2)performs a supporting function (cartilage and bone tissue);
3)provides transportation throughout the body of nutrients and oxygen (blood, lymph);
1) contains a supply of nutrients.
1.What is fabric?
2.What types of fabrics do you know?
3.What tissue is blood? What function does it perform? V
1.What are the types of epithelial tissue? Describe the glandular etghelion.
2.Where is ciliated epithelium located? What role does he play?
3.What are the types of connective tissue? Where is dense fibrous tissue located?
1.What organs contain ciliated, integumentary single-layer and stratified epithelium? What role do they play?
2.Describe the functions of connective tissue. What is its feature?
Epithelial tissue covers the entire outer surface of the human body, lines all body cavities. Lines the mucous membrane of hollow organs, serous membranes, is part of the glands of the body. Therefore, they distinguish integumentary and glandular epithelium.
Epithelial tissue is located on the border of the external and internal environment of the body. And participates in the metabolism between the body and the external environment. Performs protective role (skin epithelium). Performs functions suction(intestinal epithelium) allocation(renal tubular epithelium) gas exchange(epithelium of the alveoli of the lungs). This fabric has a high regeneration. glandular epithelium, which forms gland, able to allocate secrets. This ability to produce and release substances necessary for life is called secretion. This epithelium is called secretory.
Distinctive features of epithelial tissue:
-Epithelial tissue is located on the border of the external and internal environment of the body.
- It consists of epithelial cells, these cells form solid layers.
- In these layers there are no blood vessels.
-Nutrition this tissue occurs through diffusion through the basement membrane, which separates the epithelial tissue from the underlying loose connective tissue and serves as a support for the epithelium.
V integumentary epithelium secrete single layer epithelium and stratified.
V single layer epithelium all cells are located on the basement membrane.
V multilayer epithelium only the lower layer of cells lies on the basement membrane. The upper layers lose their connection with it and form several layers.
single layer epithelium happens single and multi-row.
epithelial cells - epitheliocytes. In epithelial cells secrete two parts. 1. Basal part - directed towards the underlying tissue. 2. Apical part - facing the free surface. In the basal part lies the nucleus.
The apical part contains organelles, inclusions, microvilli, and cilia. According to the shape of the cells, the epithelium is flat, cubic, cylindrical (prismatic).
Rice. No. 1. Types of epithelium.
Single layered squamous epithelium– mesothelium - covers the serous membranes - pleura, epicardium, peritoneum.
Single layered squamous epithelium – endothelium - lines mucous membrane circulatory and lymphatic vessels.
Single layer cubic epithelium covers renal tubules, excretory ducts of glands and small bronchi.
Single layer prismatic epithelium lines mucous membrane of the stomach.
Single layer prismatic bordered epithelium lines intestinal mucosa.
Single layer multi-row prismatic ciliated epithelium covers fallopian tubes and respiratory tract.
Stratified squamous epithelium on the basis of keratinization of the upper layers of cells are divided into keratinized and non-keratinized.
Stratified squamous keratinized epithelium – epidermis. It covers the surface of the skin. The epidermis consists of many tens of layers of cells. Cells on the surface of the skin die, turning into horny scales. They destroy the nucleus and cytoplasm and accumulate keratin.
Stratified squamous nonkeratinized epithelium lines the cornea of the eye, oral cavity, esophagus.
There is a transitional form of stratified epithelium - transition. It covers the urinary tract renal pelvis, bladder, i.e. organs that can change their volume.
glandular epithelium makes up the bulk of the body's glands. Glands in the body perform a secretory function. The secret he secretes is necessary for the processes taking place in the body. Some glands are independent organs, such as the pancreas, large salivary glands. Other glands are part of organs, such as glands in the intestinal wall, stomach. Most glands are derivatives of the epithelium.
Distinguish glands external secretion - exocrine. They have excretory ducts and secrete their secret into the body cavity or onto the surface of the body. These are the mammary glands, sweat, salivary.
There is endocrine glands - endocrine. They do not have excretory ducts and secrete their secret into the internal environment of the body - blood or lymph. Their secret is hormones.
There are glands of mixed secretion. They have endocrine and exocrine parts, such as the pancreas.
Fig No. 2. Types of glands.
exocrine glands are very diverse. Allocate unicellular and multicellular glands.
Unicellular glands- goblet cells, located in the intestinal epithelium, they produce mucus in the respiratory tract.
In multicellular glands, there are secretory and excretory duct. The secretory section is made up of cells - glandulocytes, who produce the secret. Depending on whether the excretory duct branches or not, they allocate simple and complex glands.
According to the shape of the secretory department, they are distinguished tubular, alveolar and alveolar-tubular glands.
Depending on how the secret is formed and in what way it is released from the cells, there are merocrine, apocrine and holocrine glands.
Merocrine glands are the most common. They secrete their secret into the duct without destroying the cytoplasm of the secretory cells.
In apocrine glands, there is a partial destruction of the cytoplasm of secretory cells. The apical part of the cell is destroyed and is part of the secret. Then the destroyed cell is restored. These glands include the mammary and sweat glands.
In holocrine gland secretion is accompanied by cell death. These destroyed cells are the secret of the gland. These glands include the sebaceous glands.
By the nature of the secret distinguish between mucous, protein and mixed (protein-mucous) glands.
epithelial tissue- the outer surface of the human skin, as well as the lining surface of the mucous membranes of the internal organs, gastrointestinal tract, lungs, and most glands.
The epithelium is devoid of blood vessels, so nutrition occurs at the expense of adjacent connective tissues, which are powered by blood flow.
Functions of epithelial tissue
main function skin epithelial tissue - protective, that is, limiting the impact of external factors on internal organs. The epithelial tissue has a multilayer structure, so keratinized (dead) cells are quickly replaced by new ones. It is known that epithelial tissue has increased regenerative properties, which is why human skin is quickly renewed.
There is also intestinal epithelial tissue with a single layer structure, which has suction properties, due to which digestion occurs. In addition, the intestinal epithelium has the ability to release 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
The cells of a single-layer epithelium 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 a secret. The glandular epithelium is located in the intestine, it makes up 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 off and is completely restored overnight.
Connective tissue
Connective tissue- building matter that unites and fills the entire body.
Connective tissue is present in nature in several states at once: liquid, gel-like, solid and fibrous.
In accordance with this, blood and lymph, fat and cartilage, bones, ligaments and tendons, as well as various intermediate body fluids are distinguished. The peculiarity of the connective tissue is that there is much more intercellular substance in it than the cells themselves.
Types of connective tissue
— cartilaginous, is of three types:
a) Hyaline cartilage;
b) Elastic;
c) Fibrous.
— Bone(consists of forming cells - osteoblast, and destroying - osteoclast);
— fibrous, in turn happens:
a) Loose (creates a framework 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 (tonsils, bone marrow, lymph nodes, kidneys and liver are formed from it);
b) Fat (subcutaneous energy reservoir, heat regulator);
c) Pigmentary (iris, nipple halo, anus circumference);
d) Intermediate (synovial, cerebrospinal and other auxiliary fluids).
Connective tissue functions
These structural features allow the connective tissue to perform various functions:
- Mechanical(supporting) function is performed by bone and cartilage tissues, as well as fibrous connective tissue of tendons;
- Protective function is performed by adipose tissue;
- transport function is performed by liquid connective tissues: blood and lymph.
Blood provides the transport of oxygen and carbon dioxide, nutrients, and metabolic products. Thus, the connective tissue connects the parts of the body together.
Connective tissue structure
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. by the most important cells we can name fibroblasts, which produce the substances of the intercellular fluid (elastin, collagen, etc.).
Important in the structure are also basophils (immune function), macrophages (fighters of pathogens) and melanocytes (responsible for pigmentation).
The cell is part of the tissue that makes up the body of humans and animals.
Textile - it is a system of cells and extracellular structures united by the unity of origin, structure and functions.
As a result of the interaction of the organism with the external environment, which has developed in the process of evolution, four types of tissues with certain functional features have appeared: epithelial, connective, muscle and nervous.
Each organ is made up of various tissues that are closely related. For example, the stomach, intestines, and other organs consist of epithelial, connective, smooth muscle, and nervous tissues.
The connective tissue of many organs forms the stroma, and the epithelial tissue forms the parenchyma. The function of the digestive system cannot be fully performed if its muscular activity is impaired.
Thus, the various tissues that make up a particular organ ensure the performance of the main function of this organ.
epithelial tissue
Epithelial tissue (epithelium)covers the entire outer surface of the body of humans and animals, lines the mucous membranes of hollow internal organs (stomach, intestines, urinary tract, pleura, pericardium, peritoneum) and is part of the endocrine glands. Allocate integumentary (superficial) and secretory (glandular) epithelium. Epithelial tissue is involved in the metabolism between the body and the environment, performs a protective function (skin epithelium), functions of secretion, absorption (intestinal epithelium), excretion (kidney epithelium), gas exchange (lung epithelium), and has a great regenerative capacity.
Depending on the number of cell layers and the shape of individual cells, epithelium is distinguished multilayer - keratinizing and non-keratinizing, transition and single layer - simple columnar, simple cubic (flat), simple squamous (mesothelium) (Fig. 3).
V squamous epithelium the cells are thin, compacted, contain little cytoplasm, the discoid nucleus is in the center, its edge is uneven. The squamous epithelium lines the alveoli of the lungs, the walls of capillaries, blood vessels, and cavities of the heart, where, due to its thinness, it diffuses various substances and reduces the friction of flowing fluids.
cuboidal epithelium lines the ducts of many glands, and also forms the tubules of the kidneys, performs a secretory function.
Columnar epithelium consists of tall and narrow cells. It lines the stomach, intestines, gallbladder, renal tubules, and is also part of the thyroid gland.
Rice. 3. Different types of epithelium:
A - single layer flat; B - single layer cubic; V - cylindrical; G - single-layer ciliated; D—multiple; E - multilayer keratinizing
Cells ciliated epithelium usually have the shape of a cylinder, with many cilia on the free surfaces; lines the oviducts, the ventricles of the brain, the spinal canal and the respiratory tract, where it provides the transport of various substances.
Stratified epithelium lines the urinary tract, trachea, respiratory tract and is part of the mucous membrane of the olfactory cavities.
Stratified epithelium consists of several layers of cells. It lines the outer surface of the skin, the mucous membrane of the esophagus, the inner surface of the cheeks, and the vagina.
transitional epithelium located in those organs that are subject to strong stretching (bladder, ureter, renal pelvis). The thickness of the transitional epithelium prevents urine from entering the surrounding tissues.
glandular epithelium makes up the bulk of those glands in which epithelial cells are involved in the formation and release of substances necessary for the body.
There are two types of secretory cells - exocrine and endocrine. exocrine cells they secrete a secret on the free surface of the epithelium and through the ducts into the cavity (stomach, intestines, respiratory tract, etc.). Endocrine called glands, the secret (hormone) of which is secreted directly into the blood or lymph (pituitary, thyroid, thymus, adrenal glands).
According to the structure, exocrine glands can be tubular, alveolar, tubular-alveolar.
