epithelial tissue Flashcards
who coined the term epithelium ?
Ruysch
what is epithelium?
epithelium is made up of one layer or more than one layer of cells, they cover or lines organs and other external and infernal parts of the body.
explain the the structure of epithelial tissues?
they are made up of variously shaped cells closely arranges with very little intercellular material.it has one or more than one layer.it consists of a basal surface which lies on the basement membrane and free surface which faces the body fluid or outside environment and thus proving a protecting covering
what is basement membrane and explain its function?
basement membrane is a non- cellular layer which is responsible for providing elastic support to the epithelial cell and also anchors it to the underlying connective tissue for obtaining nutrients
what are the main two groups of epithelial tissue?`
simple epithelium and compound epithelium
whaat are the 6 types of simple epithelial tissue?
1) squamous
2) cuboidal
3) columnar
4) glandular
5) pseudo stratified
6) ciliated
explain the structure of squamous epithelium?
they are closely fitted thin flat cell with irregular boundaries .but from the surface they look polygonal they are also called pavement cells. They have a flat thin centrally located nuclei
where are squamous epithelial cells located?
inner blood vessels(endothelium).Bowman’s capsule, Loop of Henle, lymph vessels, coelomic cavity, alveoli
what are the functions of epithelial tissue?
since they are thin its easier for particles to pass-through
1) they help is filtration in Bowman’s capsule
2) exchange of material between blood capillaries and tissue fluid
3) exchange of gases in alveoli
explain the structure of cuboidal epithelium?
it consists of cube shaped cells that has a centrally located round nuclei.the free surface are either smooth or has microvilli wich increases the area of absorption.cuboidal epithelium with micro villi are called brush bodered epithelium
where are cuboidal epithelium located?
they are located in :
1) ducts of glands, thyroid follicles
2) ovaries and testis (germinal epithelium
3) PCT of nephron(brush bordered epithelium)
functions of cuboidal epithelium?
1) selective reabsorption in PCT
2) SECRETION AND excretion by glands
what is germinal epithelium?
they are cuboidal epithelium present in ovaries and seminiferous tubules of testes, they produce gametes , ova and sperms
explain structure of columnar epithelium?
they are tall and slender cellls. the nuclei is elongated along the long axis and is present near the base of the cell. their free surface can be smooth or can have microvilli. some columnar cells produce mucus(goblet cell)
what are mucosa?
they are mucus producing epithelium with underlying connective tissue
what are brush bordered columnar epithelium?
they are intestinal mucosa with micro villi .
where is columnar epithelium located?
lining of stomach and intestine., gall bladder , bile duct pancreatic lobules
what are the functions of columnar epithelium?
secretion and absorption.
what are ciliated epithelium and explain its structure?
they are cuboidal or columnar cell that bear cilia(hair-like outgrowth).the cilia stays in a rhythmic motion to create a current that moves materials in contact to a specific direction.
where are ciliated epithelium located?
cuboidal: - smaller bronchioles, nephrons
columnar: -fallopian tube, most of the respiratory tract., ventricles of the brain, lymphatic tube cavity of the middle ear, the central canal of the spinal cord, eustachian tube
what are the functions of ciliated epithelium?
1) in fallopian tube they help in the passage of ovum through the fallopian tube.
2) they help in the expelling of mucus and other particles present in the respiratory tract, towards pharynx.
what are mucus producing columnar epithelium called?
goblet cells
what are pseudostratified epithelium?
they are single layered epithelium whose nuclei is positioned in a manner that makes it look like stratified epithelia.
explain the structure of pseudostratified epithelium?
they are columnar cell but in unequal sizes, the t long cell extend upto the free surface and has oval nuclei. the short cells do not reach the outer free surface and has round nuclei .the nuclei lie at different levels making it look stratified ,and thus giving it the name pseudostratified epithelium. goblet cells also occur in this epithelium
where are pseudostratified epithelium located?
non ciliated: urethra of males
ciliated: large bronchi and trachea
what are glandular epithelium?
they are epithelium that get specialized for secretion, cells of glandular epithelium are columnar or cuboidal in outline.the glands are formed from glandular epithelium n. glands may be made up of a cell,tissue or organ.
what are glands classified into on the bases of mode of secretion?
glands are classified into :
1)endocrine gland: they are ductless glands that secret products(hormones) directly into the fluid the bathing the gland i.e blood and lymph. blood and lymph caries the hormones to the target organ.eg: thyroid, adrenal, hypothalamus , pituitary .
2) exocrine: they drain out their secretion to the body surface through a duct or pours directly over the substrate. exocrine glands secret mucus saliva ,earwax, oil , milk , digestive enzymes and other cell products. eg: salivary gland, gastric gland , mammary gland etc.
what are compound epithelium?
they are epithelium that consists more than on layer. they are responsible for protection of underlying tissues from mechanical, chemical and thermal or osmotic stress.
what are the two parts of a compound epithelium?
stratum cornea and stratum germinativum
what are the 2 types of compound epithelium?
stratified epithelium and transitional epithelium
what are the different types of stratified epithelium?
1) stratified cuboidal-e.g.: large salivary ducts
2) non keratinized squamous(squamous + cuboidal):
e. g.- buccal cavity , tongue , pharynx , oesophagus.
3) keratinized stratified squamous : epidermis of land vertebrates
what are transitional epithelium?
1) its thinner and more stretchable that stratified epithelium
2) it has single layer of cuboidal cells at the base
3) 2-3 middle layers made up of polygonal or pear shaped cells
4) superficial; layer of large broad oval or rectangular cells.
5) lack basement membrane
6) eg; inner surface of urinary bladder and ureter.(urothethelieum) considerable expansions of these organs allows to accommodate urine, because stretching considerably flattens and broadens the cells of superficial and middle layer
what are glands classified into based on secretory and ducts part?
1) tubular
2) alveolar /saccular gland
what are tubular g;ands?
1) simple tubular: eg crpts of leiberkuhn
2) simple coiled tubular : sweat glands
3) simple branched tubular glands: gastric gland
4) compound tubular: mammary gland of oviparous mammal
what are alveolar glands / saccular glands?
1) simple alveolar: skin gland of frogs, poison gland of toads.
2) simple branched alveolar: sebaceous gland
3) compound alveolar: sublingual and submandibular salivary glands
4) compound tubular alveolar gland : parotid gland, mammary gland of humans
what are the 3 types of glands based on secretion?
1) merocrine gland cells: pancreas, gastric, sweat salivary
2) apocrine cells: mammary gland humans.
3) holocrine cells: sebaceous gland
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