STRTIFIED EPITHELIUM


B .STRTIFIED EPITHELIUM:qq

1.It consists of two or more layers of cells.
2. It protects the underlying tissues.
3. The lower most layer consists of columnar cells called stratum germinatium. It lies n the basement membrane.
4. The middle layer contains round granular cells called stratum granulosa.
5. The upper most layer contains flattened, dead, keratinised cells called stratum corneum.
6. It gives protection. Hence it is called protective epithelium.
According to the shape of cells in its apical layer, the stratified epithelium is clasified in to four types.
They are:

a) Stratified squamous Epithelium- It covers dry surface such as the skin(keratinized)
It covers wet surface such as oesophagus and vegina( Non keratinized)

b) Stratified cubodal Epithelium- Ducts of sweat glands.
c) Stratified columnar Epithelium- conjuctiva of the eye.
d) Transitional Epithelium- urinary bladder, urethra, uterus

a) Stratified squamous Epithelium :

1.Cells of apical layer are squamous.
2. Cells of basal layer are cubodal or columnar
3. It is found primarily in places subject to abrasion.
4. The superficial cells are sloughed off.
It is of tw types:i) stratified squamous keratinized
ii) stratified squamous non keratinized
i) stratified squamous keratinized:
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1. It covers dry surface such as the skin
2. The cells of apical layers contain a layer of keratin.
3. It protects the underlying tissues from microbes, heat and chemicals.

ii) stratified squamous non keratinized:
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It covers wet surfaces such as oesophagus, vagina.

b) Stratified cubodal Epithelium :
It has two or more layers of cells.
Cells in the apical layers are cube- shaped.
It is a rare type of epithelium.
Location: Ducts of sweat glands.

c) Stratified columnar Epithelium:
It has several layers of irregular cells.
Cells in the apical layer are columnar
It is also uncommon.
Location: Conjuctiva of the eye
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d)Transitional Epithelium:

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1. It is specialized to a greater degree f stretch.
2. The transitional epithelium of the urinary bladder has about four or five layers of cells.
3.The superfecial cells are rounded.
4.When the bladder is full of urine, the superfecial cells become squamous and the epithelium appears to be two or three cells thick.
Location: Urinary bladder, uterus and parts of urethra.

d) Pseudo stratified epithelium:
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1. single layer of the cells rest on the basal lamina, which makes it a simple epithelium.
2. It contains of cells some of which are tall and some are short.
3. The short cells do not reach the surface of the epithelium.
4. The nuclei of the cells are at various levels.
5. It gives a false impression as if it is a stratified epithelium.
6. It is of the two types : a) Ciliated
b) Non Ciliated
a) Pseudo stratified ciliated columnar epithelium:
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It occurs in trachea
Cellls that extend to the surface either secrate mucus or beat cilia.
Mucus traps foreign particles and cilia sweep away mucus.
b)Pseudo stratified non ciliated columnar epithelium:

Lacks goblet cells
Cilia are absent
It occurs in epididymis and a part of urethra

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About balarangaiahnarapuram

TEACHER M.Sc in ZOOLOGY M.Sc in PSYCHOLOGY B.Ed
This entry was posted in ANIMAL ORGANIZATION and tagged , , , , , . Bookmark the permalink.

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