how many types of cell in ur body?
200
definition of tissue
collection of cells and its products that perform similar function
characteristics of epithelial tissues
o Cells are bound closely together (no gaps between cells)
o One surface of the cells are exposed to the
environment
o Base of the cells rest on a basement membrane
o There are no blood vessels
o Cells are continually replaced by stem cells
what is epthelia
cells that cover external & internal surfaces
physical barrier
function + type + eg of glands
[function] for secretion
[types]
- endocrine ( hormones-insulins)
- exocrine (sweat/mammary/sebaceous glands)
3 modes of secretion (exocrine glands)
1) merocrine [ released as vesicles]
2) apocrine [part of cell breaks]
3) holocrine [cell bursts]
eg. of int + ext surfaces epithelia cover
[int]
tubal organs- lining of mouth, vagina, vessels, trachea
body cavities- pleura, peritoneum and pericardium
[ext]
skin
classification of epithelia
[number of layers]
- simple
- stratified
- pseudostratified
[shape of the cell]
- squamous
- cuboidal
- columnar
[presence of special structures]
- ciliated epithelium
= helps in the movement of substances/secretions settling on its surface
- keratinised epithelium (dead cells)
= waterproof and reduce evaporation from underlying
tissues
location + functions of SIMPLE SQUAMOUS EPITHELIUM
[location]
- blood vessels
- lungs, alveoli
- kidneys, filtration membrane
[function]
- efficient diffusion of gases, nutrients & wastes
location + functions of SIMPLE CUBOIDAL EPITHELIUM
[location]
- kidney tubules
- thyroid gland
[function]
- secretion + absorption
location + functions of SIMPLE COLUMNAR EPITHELIUM
[location]
- stomach
- intestinal lining
- gall bladder
- bladder
[function]
- secretion + absorption
location + functions of STRATIFIED SQUAMOUS EPITHELIUM
[location]
- lining of mouth
- vagina
- anus
[function]
- physical protection against friction
location + functions of KERATINIZED STRATIFIED SQUAMOUS EPITHELIUM
[location]
-skin, epithelium
[function]
- waterproof layer
- physical protection against friction
location + functions of PSEUDOSTRATIFIED CILIATED EPITHELIUM
[location]
- trachea
- bronchi
- nasal cavity
[function]
- secretion
- protection
location + functions of TRANSITIONAL EPITHELIUM
[location]
- urinary bladder
- ureters
- renal pelvis
[function]
- withstand stretching
functions of epithelial tissue
- provides physical protection
- produces specialised secretion
- provide sensations
- controls permeablility
