Epithelial tissue:
It may be defined as collection of closely aggregated polyhedral cells with very little intercellular substance covering internal and external surfaces of the body.
Functions:
1)Protection of the underlying structure
2)Secretion
3)Absorption
There are two major categories of epithelia:
Membranous and Glandular.
1.Membranous epithelia are located throughout the body and form such structures as the outer layer of the skin; the inner lining of body cavities, tubes, and ducts; and the covering of visceral organs.
2.Glandular epithelia are specialized tissues that form the secretory portion of glands.
Membranous epithelia are histologically classified by the number of layers of cells and the shape of the cells along the exposed surface.
3.Epithelial tissues that are composed of a single layer of cells are called simple; those that are layered are said to be stratified.
4.Squamous cells are flattened; cuboidal cells are cubeshaped; and columnar cells are taller than they are wide.
Simple Epithelia:
Simple epithelial tissue is a single cell layer thick and is located where diffusion, absorption, filtration, and secretion are principal functions.
Simple Columnar Epithelium:
Simple columnar epithelium is composed of tall, columnar cells. The height of the cells varies, depending on the site and function of the tissue.
Each cell contains a single nucleus which is usually located near the basement membrane . Simple columnar epithelium is found lining the inside walls of the stomach and intestine.
Simple Squamous Epithelium:
Simple squamous epithelium is composed of flattened, irregularly shaped cells that are tightly bound together.
Each cell contains an oval or spherical central nucleus. This epithelium is adapted for diffusion and filtration.
It occurs in the pulmonary alveoli within the lungs (where gaseous exchange occurs), in portions of the kidney (where blood is filtered),
n the inside walls of blood vessels, in the lining of body cavities, and in the covering of the viscera.
Simple Cuboidal Epithelium:
Simple cuboidal epithelium is composed of a single layer of tightly fitted cube-shaped cells. This type of epithelium is found lining small ducts and tubules that have excretory, secretory,or absorptive functions.
It occurs on the surface of the ovaries, forms a portion of the tubules within the kidney, and lines the ducts of the salivary glands and pancreas.
Simple Ciliated Columnar Epithelium:
Simple ciliated columnar epithelium is characterized by the presence of cilia along its free surface. By contrast, the simple columnar type is unciliated.
Cilia produce wavelike movements that transport materials through tubes or passageways. This type of epithelium occurs in the female uterine tubes to move the ovum (egg cell) toward the uterus.
Pseudo-stratified Ciliated Columnar Epithelium:
As the name implies, this type of epithelium has a layered appearance (strata = layers). Actually, it is not multilayered (pseudo = false), because each cell is in contact with the basement membrane.
The tissue appears to be stratified because the nuclei of the cells are located at different levels.
It is found lining the inside walls of the trachea and the bronchial tubes; hence, it is frequently called respiratory epithelium. Its function is to remove foreign dust and bacteria entrapped in mucus from the lower respiratory system.
Stratified Epithelia :
Stratified epithelia have two or more layers of cells. Stratified epithelia have a primarily protective function that is enhanced by rapid cell divisions.
Stratified Squamous Epithelium:
Stratified squamous epithelium is composed of a variable number of cell layers that are flattest at the surface.There are two types of stratified squamous epithelial tissues: keratinized and nonkeratinized.
1. Keratinized stratified squamous epithelium:
It contains keratin, a protein that strengthens the tissue. Keratin makes the epidermis (outer layer) of the skin somewhat waterproof and protects it from bacterial invasion
The outer layers of the skin are dead, but glandular secretions keep them soft.
2. Nonkeratinized stratified squamous epithelium:
It lines the oral cavity and pharynx, nasal cavity, vagina, and anal canal. This type of epithelium, called mucosa (myoo-ko′sa˘),is well adapted to withstand moderate abrasion but not fluid loss.
Stratified Cuboidal Epithelium:
Stratified cuboidal epithelium usually consists of only two or three layers of cuboidal cells. This type of epithelium is confined to the linings of the large ducts of sweat glands, salivary glands, and the pancreas, where its stratification probably provides a more robust lining than would simple epithelium.
Transitional Epithelium:
Transitional epithelium is similar to nonkeratinized stratified squamous epithelium except that the surface cells of the former are large and round rather than flat, and some may have two nuclei.
Transitional epithelium is found only in the urinary system, particularly lining the cavity of the urinary bladder and lining the lumina of the ureters.
This tissue is specialized to permit distension (stretching) of the urinary bladder as it fills with urine
The inner, exposed cells actually transform from being rounded when the urinary bladder is empty to being somewhat flattened as it distends with urine.
Connective tissue is the most abundant tissue in the body. It supports other tissues or binds them together and provides for the metabolic needs of all body organs. Certain types of connective tissue store nutritional substances; other types manufacture protective and regulatory materials.
A. Embryonic connective tissue
B. Connective tissue proper
1. Loose (areolar) connective tissue
2. Dense regular connective tissue
3. Dense irregular connective tissue
4. Elastic connective tissue
5. Reticular connective tissue
6. Adipose tissue
C. Cartilage
1. Hyaline cartilage
2. Fibrocartilage
3. Elastic cartilage
D. Bone tissue
E. Blood (vascular tissue)
It may be defined as collection of closely aggregated polyhedral cells with very little intercellular substance covering internal and external surfaces of the body.
Functions:
1)Protection of the underlying structure
2)Secretion
3)Absorption
There are two major categories of epithelia:
Membranous and Glandular.
1.Membranous epithelia are located throughout the body and form such structures as the outer layer of the skin; the inner lining of body cavities, tubes, and ducts; and the covering of visceral organs.
2.Glandular epithelia are specialized tissues that form the secretory portion of glands.
Membranous epithelia are histologically classified by the number of layers of cells and the shape of the cells along the exposed surface.
3.Epithelial tissues that are composed of a single layer of cells are called simple; those that are layered are said to be stratified.
4.Squamous cells are flattened; cuboidal cells are cubeshaped; and columnar cells are taller than they are wide.
Simple Epithelia:
Simple epithelial tissue is a single cell layer thick and is located where diffusion, absorption, filtration, and secretion are principal functions.
Simple Columnar Epithelium:
Simple columnar epithelium is composed of tall, columnar cells. The height of the cells varies, depending on the site and function of the tissue.
Each cell contains a single nucleus which is usually located near the basement membrane . Simple columnar epithelium is found lining the inside walls of the stomach and intestine.
Simple Squamous Epithelium:
Simple squamous epithelium is composed of flattened, irregularly shaped cells that are tightly bound together.
Each cell contains an oval or spherical central nucleus. This epithelium is adapted for diffusion and filtration.
It occurs in the pulmonary alveoli within the lungs (where gaseous exchange occurs), in portions of the kidney (where blood is filtered),
n the inside walls of blood vessels, in the lining of body cavities, and in the covering of the viscera.
Simple Cuboidal Epithelium:
Simple cuboidal epithelium is composed of a single layer of tightly fitted cube-shaped cells. This type of epithelium is found lining small ducts and tubules that have excretory, secretory,or absorptive functions.
It occurs on the surface of the ovaries, forms a portion of the tubules within the kidney, and lines the ducts of the salivary glands and pancreas.
Simple Ciliated Columnar Epithelium:
Simple ciliated columnar epithelium is characterized by the presence of cilia along its free surface. By contrast, the simple columnar type is unciliated.
Cilia produce wavelike movements that transport materials through tubes or passageways. This type of epithelium occurs in the female uterine tubes to move the ovum (egg cell) toward the uterus.
Pseudo-stratified Ciliated Columnar Epithelium:
As the name implies, this type of epithelium has a layered appearance (strata = layers). Actually, it is not multilayered (pseudo = false), because each cell is in contact with the basement membrane.
The tissue appears to be stratified because the nuclei of the cells are located at different levels.
It is found lining the inside walls of the trachea and the bronchial tubes; hence, it is frequently called respiratory epithelium. Its function is to remove foreign dust and bacteria entrapped in mucus from the lower respiratory system.
Stratified Epithelia :
Stratified epithelia have two or more layers of cells. Stratified epithelia have a primarily protective function that is enhanced by rapid cell divisions.
Stratified Squamous Epithelium:
Stratified squamous epithelium is composed of a variable number of cell layers that are flattest at the surface.There are two types of stratified squamous epithelial tissues: keratinized and nonkeratinized.
1. Keratinized stratified squamous epithelium:
It contains keratin, a protein that strengthens the tissue. Keratin makes the epidermis (outer layer) of the skin somewhat waterproof and protects it from bacterial invasion
The outer layers of the skin are dead, but glandular secretions keep them soft.
2. Nonkeratinized stratified squamous epithelium:
It lines the oral cavity and pharynx, nasal cavity, vagina, and anal canal. This type of epithelium, called mucosa (myoo-ko′sa˘),is well adapted to withstand moderate abrasion but not fluid loss.
Stratified Cuboidal Epithelium:
Stratified cuboidal epithelium usually consists of only two or three layers of cuboidal cells. This type of epithelium is confined to the linings of the large ducts of sweat glands, salivary glands, and the pancreas, where its stratification probably provides a more robust lining than would simple epithelium.
Transitional Epithelium:
Transitional epithelium is similar to nonkeratinized stratified squamous epithelium except that the surface cells of the former are large and round rather than flat, and some may have two nuclei.
Transitional epithelium is found only in the urinary system, particularly lining the cavity of the urinary bladder and lining the lumina of the ureters.
This tissue is specialized to permit distension (stretching) of the urinary bladder as it fills with urine
The inner, exposed cells actually transform from being rounded when the urinary bladder is empty to being somewhat flattened as it distends with urine.
Connective tissue is the most abundant tissue in the body. It supports other tissues or binds them together and provides for the metabolic needs of all body organs. Certain types of connective tissue store nutritional substances; other types manufacture protective and regulatory materials.
A. Embryonic connective tissue
B. Connective tissue proper
1. Loose (areolar) connective tissue
2. Dense regular connective tissue
3. Dense irregular connective tissue
4. Elastic connective tissue
5. Reticular connective tissue
6. Adipose tissue
C. Cartilage
1. Hyaline cartilage
2. Fibrocartilage
3. Elastic cartilage
D. Bone tissue
E. Blood (vascular tissue)
