EXCRETION

EXCRETION:

It is the process by which harmful materials are removed from the body.

The removal of harmful substances from the body.

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THE HUMAN SKIN

  1. It is the largest organ of the body.It covers most part of the body.
  2. It is a sense for feeling
  3. The skin removes sweat from the body.
  4. Through sweating, the body cools down.
skin

The skinconsists of two main layers.

❖Epidermis. ❖Dermis layer.Epidermis.

-It is the outer layer.The layers that make up the epidermis.

a) Cornified layer.

b) Granular layer

c) Malpighian layer.

Cornified layer

It is the tough outer most layer with dead cells.

  • ❖It prevents bacteria/germ invasion to the skin.
  • ❖It provides resistance to damage.
  • ❖It reduces excessive loss of water by evaporation.

Granular layer

It contains living cellsand produces new cells which die continuously to form the cornified layer.

Malpighian layer.

It is made up of young cells.

It contains melanin that determines skin colour and hair colour.Melanin also protects theskin against strong radiation from the sun.❖NB: When you lack melanin, you become an albino❖On the finger nails are cells called keratin that helps to produce toes and finger nails.Dermis.It is the inner layer of the skin.Parts of the dermis.Capillaries, Sweat glands, Hair follicle, Sebaceous glands, Sweat duct, Pore, ❖Erector muscles, Nerves, Subcutaneous fat .Uses of some partsof the skin.❖Hair: For keeping the body warm.❖Sweat glands: They produceand storesweatAbsorbs sweat from blood.❖Pore: It lets sweat out of the body.❖Capillaries: Transport food and oxygen to all parts of the skin.❖Sebaceous glands: Produce an oily substance called sebum.Sebum protects, lubricates and water proofs the skin, helps repel water, damaging chemicals and microorganisms.❖Erector muscle: It keeps the hair standing.❖Nerves:Conduct sensations of pain and touch.❖Subcutaneous fat:It contains fat cells where fat is stored.