LAB – NO.-2
The Animal Tissue
Tissue is the collection of specialized cells and cell product that perform a relatively limited number of function . the science which study of tissue is called HISTOLOGY .
There are four basic tissue types :
1-Epithelium Tissue
2-connectve tissue
3- muscle tissue
4- neural tissue
Epithelial tissue :
Epithelial tissue is made of closely – packed cells arranged in flat sheets (like layer of cells ). Epithelial form the surface of the skin and line the various cavities and tubes of the body . where Epithelium lines the inner surface of the heart , blood vessels and lymphatic vessels it is given a special name "ENDOTHELUM " .
Epithelium tissue also often contain glandular cells that function in fluid secretion .the entire sheet of the Epithelial cells is attached to a layer of extracelluler matrix that is called the (Basal Lamina or Basement Membrane) .
The chief function of the Epithelium is protection but the cells are also variously specialized for secretion , extraction , absorption and sensory perception .
Epithelial tissue may be classified according to the :
¤-Number of layer of cell :(simple and stratified ).
¤- shape of the cell on the free surface :(Squamous ,Cuboidal , Columnar ).
SIMBLE EPITELIAL TISSUE :
Simple Epithelium tissue is made up of single layer of Epithelial cells , it is found where there is not much wear and tear or where diffusion or absorption occurs . simple Epithelium are thin , fragile and found only in protective areas inside the body like ventral body cavities , the chamber of the heart and all blood vessels
1-Simple Squamous Epithelium Tissue :
Composed of thin flat cells , irregular in shape with round or oval nuclei ,found inside walls of blood vessels (ENDOTHELUM ), the body cavities and the alveoli of the lung . The simple squamous Epithelium that line ventral body cavities is known (MESOTHELIUM ).
2-Simple Cuboidal Epithelium Tissue :
The cells of cuboidal epithelium resemble little hexagonal boxes .They appear square in typical sectional views , the nuclei are near the center of each cell .Such an epithelium lines protions of kidney tubules , saliva gland and lines the follicles of thyroid gland .
3-Simple Columnar Epithelium Tissue
Columnar Epithelium Tissue are also hexagonal in cross section ,but they are taller and more slender than Cuboidal epithelial cells . The nuclei s are crowded into narrow band close to the basement membrane . Simple columnar Epithelium is found inside the small intestine ,large intestine and stomach .
4- Pseudostratified Columnar Epithelium tissue :
Pseudostratified Columnar cells are actually simple epithelium with all the cell resting on a basement membrane but the cells have appearance of stratified epithelium ; because they are not all the same height and their nuclei located at different levels ,some cells do not reach the surface , this type of possess cilia and lines most of nasal cavity and portion of male reproductive tract and trachea .
STRATIFIED EPITHELIUM TISSUE :
Composed of two or more layers of cells ,it is generally found in areas subject to mechanical or chemical stresses ,such as the surface of skin .
1- Stratified Squamous Epithelium Tissue :
It I generally located where mechanical stresses are sever ,the tissue is composed of series of layer of cells . This Type of tissue found in skin , pharynx ,esophagus and vagina .In skin where mechanical stresses and dehydration problem ,the apical layer of epithelial cells are packed filament of the protein , keratin ,there form called keratinized stratified squmaous .
2- Stratified Cuboidal Epithelium Tissue :
They composed of epithelial cells , it is found along the duct of the sweet gland and mammary gland .
3- Stratified Columnar Epithelium Tissue :
It is multiple layer of epithelial cells stratified columnar providing protection and locating in epiglottis , urethra and anus .
4- Transitional Epithelium Tissue :
It is called stratified because the appearance of the epithelium changes as the stretching occurs .A transitional epithelium confined to the urinary biadde where large changes in volume occurs when relaxed theepithelium appear to be four or five cells thicks ,when stretched . it appears only two or three cell thick with the surface cell flattened.