Introductio Of tissue

Tissues Introductio Of
Groups of cells similar in structure and function -
The four types of tissues -
Epithelial -
Connective -
Muscle -
Nerve -
Epithelial Tissue
Cellularity – composed almost entirely of cells -
-Special contacts – form continuous sheets held together by tight junctions and desmosomes
Polarity – apical and basal surfaces -
-Supported by connective tissue – reticular and basal laminae
-Avascular but innervated – contains no blood vessels but supplied by nerve fibers
Regenerative – rapidly replaces lost cells by cell division -
Classification of Epithelia
Simple or stratified -
Squamous, cuboidal, or columnar -
Epithelia: Simple Squamous
-Single layer of flattened cells with disc-shaped nuclei and sparse cytoplasm
Functions
Diffusion and filtration
=Provide a slick, friction-reducing lining in lymphatic and cardiovascular systems
-Present in the kidney glomeruli, lining of heart, blood vessels, lymphatic vessels, and serosae
Epithelia: Simple Cuboidal
-Single layer of cubelike cells with large, spherical central nuclei
Function in secretion and absorption-
-Present in kidney tubules, ducts and secretory portions of small glands, and ovary surface
Epithelia: Simple Columnar
Single layer of tall cells with oval nuclei; many contain cili -
Goblet cells are often found in this layer -
Function in absorption and secretion
Nonciliated type line digestive tract and gallbladder -
-Ciliated type line small bronchi, uterine tubes, and some regions of the uterus
Epithelia: Pseudostratified Columnar
-Single layer of cells with different heights; some do not reach the free surface
Nuclei are seen at different layers-
Function in secretion and propulsion of mucus