Endothelium
The squamous epithelial tissue present in the inner wall of blood vessels and lymphatic vessels is called endothelium.
Endocardium: The squamous epithelial tissue present in the inner wall of the heart is called the endocardium.
Endocardium Functions
- Protection: It protects internal organs from mechanical injury and infection.
- Diffusion: It helps in the diffusion of gases and nutrients, for example, lung alveoli and capillary endothelium.
- Filtration: It helps in ultrafiltration in the Bowman’s capsule of nephron, epithelium, and endothelium.
Read and Learn More: WBCHSE Notes for Class 11 Biology
Cuboidal Epithelial Tissue
Cuboidal Epithelial Tissue Definition: The epithelial tissue that consists of cube-shaped cells that rest on the basement membrane is called cuboidal epithelial tissue.
Cuboidal Epithelial Tissue Position: It is found in the thyroid gland, salivary gland, bronchioles in the lungs, proximal and distal convoluted tubules of the nephron, covering of the ovary (germinal epithelium), etc.
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Endothelium meaning
Cuboidal Epithelial Tissue Structure:
- Cells of this tissue are cuboidal in shape and similar in size i.e., they have almost equal length, breadth, and height.
- The nucleus is spherical and centrally located.
- The cytoplasm is granular.
- The free surfaces of the cells are sometimes lined by microvilli.
- Such a surface containing microvilli is called a brush border.
Cuboidal Epithelial Tissue Function
Protection: It protects the organs to which it is associated.
Secretion: It secretes various secretory products when present in secretory glands such as the thyroid, pancreas, mucous gland, salivary gland, and sweat gland.
Endothelium definition and function notes PDF
Reabsorption: Under special conditions (within convoluted tubules in nephrons), cuboidal epithelium reabsorbs molecules and ions from the urine. Thus, this tissue takes part in urine formation.
Cuboidal epithelial tissue Function Types: Different types of cuboidal epithelium, their definition, positions, and functions are given in the following table
Columnar epithelial tissue
Columnar epithelial tissue Definition: The epithelial tissue in which cells are column-shaped (i.e., height is more than their breadth), is called columnar epithelial tissue.
Columnar epithelial tissue Position: It is found in the lining of the digestive tract, gall bladder, bile duct, ducts of gastric gland, intestinal gland, sweat, and sebaceous gland, and pancreatic lobules.
Columnar epithelial tissue Structure: Cells of this tissue are tall and elongated.
The nucleus is oval-shaped and is situated near the base of the cell, in case the cell is secretory in nature. Otherwise, the nucleus lies at the center of the cell.
Endothelium function in blood vessels and cardiovascular system
“endothelial meaning “
A brush border is seen in the free surface of the epithelium lining the inner cavity of convoluted tubules of the small intestine.
Columnar epithelial tissue Functions
Absorption: It helps in the absorption of digested food into blood by the intestinal epithelium.
Secretion: Columnar epithelium of the gastric and intestinal glands transform into pitcher-shaped cells, known as goblet cells. They secrete mucus.
Protection: The mucus, secreted by the goblet cells, protects the lining of the stomach from the effect of the HCI acid secreted in it. In this way, they protect the organs to which the epithelium is associated.
Types: Types of columnar epithelium, their definition, position, and functions are given in the table below.
Ciliated epithelial tissue Definition: The epithelial tissue that is made up of generally columnar, sometimes cuboidal cells, with fine JiaÿBce processes or cilia on the free surface is known as ciliated epithelial tissue.
Position: It is found in the fallopian tube, most of the uterus, the efferent tubule of testes, the lining of the ventricles of the brain, and the central canal of the spinal cord.
Structure:
- Cells of this tissue are either columnar or cuboidal.
- The free surface of the cells has 20-30 cilia.
- The root of the cilia has a row of particles or corpuscles at its base, called basal granules. These are considered to be the residue of centriole.
- Thread-like structures extend inward, from each basal granule, into the protoplasm of the cell.
Types of cilia on the free surface of epithelial tissue
Kinocilia: These are motile in nature. These cilia originate from basal granules of the cytoplasm. These are present on the inner walls of the trachea.
Stereocilia: These are non-motile in nature. These cilia are formed by the foldings of the plasma membrane. These are seen in epididymis and vas deferens.
Types of cilia on the free surface of epithelial tissue Function
Protection: Wave-like unidirectional movement of cilia of the columnar epithelial cells helps to sweep out mucus and dust particles in organs such as the trachea, nasal passages, etc.
Transport of ovum: The fallopian tube, helps in the transport of the ovum towards the uterus.
“blood vessel lining “
Transport of cerebrospinal fluid (CSF): It helps in the circulation of CSF into cerebrospinal cavities of the central nervous system.
Glandular epithelial tissue Definition: The epithelial tissue that is made up of cells specialized mainly in secretory functions is known as glandular epithelial tissue.
The secretory organs formed by the glandular epithelia are called glands. The secreted substances can be enzymes, hormones, or chemicals. The secretions are transported to their target organs or cells either by duct (in case of enzymes, chemicals, etc.) or without duct (in case of hormones).
Class 11 biology endothelium notes with diagrams
Position: It is found in mammary glands, sweat glands, sebaceous glands, salivary glands, part of Intestinal glands, and thyroid gland.
“endothelial cells “
Glandular epithelial tissue Structure:
- Cells of this tissue are generally cuboidal, columnar, or polygonal in shape.
- The cells are usually arranged in one layer but in the salivary gland, a second layer may be found.
- Sometimes, the secretory cells may be present as bundles. These cells are specialized for the synthesis and secretion of enzymes, hormones, or certain chemicals required by the body.
- The cytoplasm is granular in nature. It contains membrane-bound secretory vesicles.
- Each cell bears a large nucleus.