Epidermis, Biology

Assignment Help:

EPIDERMIS -

  1. Ectodermal in origin. Outer part of skin. Made up of stratified epithelium.
  2. Branches of sensory nerves present. More branches on lips, tips of fingers.
  3. Blood vessels are absent. Get necessary miaterials from dermis.
  4. Porous in nature. Thickest in sole. Thinnest in cornea (conjuctiva).
  5. On palm grooves are known as sulcicutis & ridges are known as cristae cutis. Their study is dactyloscopy.
  6. Their arrangement on fingers & thumb are finger mark, i.e. dermatoglyphics.
  7. After the birth of babies, permanent linings on abdomen of women are linear gravidarum.
  8. In epidermis outer to inner following layers are clear -

1. Stratum corneum

2. Stratum lucidum

3. Stratum granulosum

4. Stratum spinosum

5. Stratum malpighi

 

 

1.      STRATUM CORNEUM -

  1. Outermost part of epidermis. 8-10 layers of cells present.
  2. Cells are flat, intercellular spaces absent, nucleus absent, cytoplasm negligible, more or less dead.
  3. Keratine protein present which is scleroprotein. It gives impermeability to skin.
  4. As on inner side new layer are formed by S. malpighi, outer layer of corneum is shed off. It is known as ecdysis.
  5. Free cholesterol and fat present in this layer.
  6. Claws, nails, horns hoofs in animals are formed by this layer.
  7. This layer is endocrine in nature. Hormon secreted by this layer reduces power of cell division in S. malpighi.
  8. If we remove this layer sensivity is increased.

 

2.      STRATUM LUCIDUM -

  1. Present inside S. corneum. 2-3 layers present. Cells are flat, intercellular spaces absent.
  2. Nucleus present, cytoplasm present, living cells eleidin present, that gives transparnacy to this layer.
  3. It is also known as clear zone, barrier layer.
  4. This layer checks water & other minerals to move out.

 

3.      STRATUM GRANULOSUM -

  1. In cytoplasm keratohyaline present which is made up of polysaccharide, Ca & RNA, basophillic in nature.
  2. Cornification or keratinization is common i.e. keratohyaline is converted first in to eleidin then in keratine.
  3. In this process malpighi cells first become cuboidal then squamous.

 

4.      STRATUM SPINOSUM -

  1. Situated inside S. granulosum. Cells are polygonal. Also known as prickle cells.
  2. Keratohyaline granules present little.

 

5.      STRATUM MALPIGHI -

  1. Also known as S. Germinativum.
  2. Inner most part of epidermis. 1-2 layers present. Capable of cell division.
  3. Cells are round in shape but columner type, so this layer is also known as S. Cylindricum.
  4. Complete epidermis is formed by it.
  5. S. Malpighi rests on basement membrane of dermis.
  6. S. Malpighi forms out growth as Rete pegs enter in dermis.
  7. Melanin pigment present, formed in melanasome part of melanocyte, dopa oxidase enzyme is needed for it.
  8. Colour of skin depends on quantity and shades of melanin.
  9. Melanin absent in palm & sole. Melanin maximum in areola mammary.
  10. Worm blooded animals of hot & humid area have abundent melanin pig. It is explained by Gloger's law.
  11. Melanin is under control of MSH & UV rays.
  12. Darking of skin after exposure to UV rays is common.
  13. In man complete absence of melanin is albinism due to recessive gene & absence of tyrosinase as melanin is derivative of tyrosine.
  14. Chromatophores absent. In frog present in dermis.
  15. In leucodermea melanin becomes absent at patches. Such skin is peibled skin.

158_mammalian skin.png


Related Discussions:- Epidermis

How depolarization of the neuronal plasma membrane generated, How is the de...

How is the depolarization of the neuronal plasma membrane generated? How does the cell return to its original rest? When the neuron receives a stimulus by the binding of neurot

Photosynthesis, Photosynthesis Two main energy pathways are recognised...

Photosynthesis Two main energy pathways are recognised in living systems. These are photosynthesis and cellular respiration. Both have their respective but different electron

What are plant cell vacuoles, What are plant cell vacuoles? What are their ...

What are plant cell vacuoles? What are their functions? How is the covering membrane of the vacuoles called? Ans) Plant cell vacuoles are cell structures delimited by membranes

All or None Response, All or None Response A very weak stimulus does n...

All or None Response A very weak stimulus does not result in an action potential. The stimulus must have a certain strength to evoke an excitation. This is the threshold value

How is retaining structure used, How is retaining structure used? A ret...

How is retaining structure used? A retaining wall helps in maintaining the surface of the ground at different elevations on either side of the structure. If the retaining wall

How is claimant need to make balance of probability, How is claimant need t...

How is claimant need to make balance of probability? When there is no loss suffered through a person after that there cannot be a civil proceeding not like under criminal law t

Explain the riboflavin content of rbc - riboflavin, Explain the Riboflavin ...

Explain the Riboflavin content of RBC - Riboflavin? The erythrocyte glutathione reductase assay, with an activity coe cient (AC) expressing the ratio of activities in the prese

Mollusca, commercially important bivalve species

commercially important bivalve species

Mycotic diseases-sheep, Goat and sheep M. mycoides subsp. capri is the...

Goat and sheep M. mycoides subsp. capri is the cause of caprine pleuropneumonia, a serious malady of goats. The disease is prevalent in certain parts of this country. The mort

Financing of healthcare - constraints, Financing of Healthcare - Constraint...

Financing of Healthcare - Constraints One of the major constraints to improve the healthcare delivery system in developing countries is weak public sector management. These ec

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd