TOPIC : THE SKIN.
Let's proceed to today's Biology lecture on the skin.if you all look at your body now, you can see it all covered with some kind of meat and some part covered by this meat grows hair. This meat is called the skin. WHAT'S THE SKIN? The skin [the mammalian skin] is the largest organ of the body and it consists of two main epidermis and dermis.
The Epidermis being the outer layer consists of
1. The horny or cornified layer : Outermost layer made up of dead cells which are flexible and water proof. These cells are impregnated in Keratin.
2. Granular Layer : These are progressively more alive living cells which are produced by malpighian layer.
3. Malpighian or Germinalive layer :This layer is made up of actively dividing the cells which contain Melanin and Keratin with many infoldings that form hair follick and sabeceous glands.
The dermis is a layer of connective tissues which consists of sweat glands, hair follicles, sebaceous glands, sensory nerves, blood capillaries and fat cells.
➡️Sweat glands : These are coiled tubes which opens at the surface as sweat pores. They secrete water which contains wastes, such as mineral salt and urea called sweat.
➡️Hair Follicles : Deep pit from the infolding of the malpighian layer. It possesses nerve which responds to stimuli when the hair is touched.
➡️Sebaceous glands : It secrete Sebum which keeps the hair and epidermis waterproof, subtle and keeps out dust and micro-organisms.
➡️Blood Capillaries : Provide food and oxygen to the dermal and epidermal cells and remove this wastes.
➡️Sensory Nerve : This contains sensory cells or inspector which receives stimuli from the external environment and send them to appropriate part of the body for interpretation and action.
➡️Subcutaneous Fat : This contains fats cell which act as a long term foodstuff as well as insulating layer to prevent heart loss.
FUNCTIONS OF THE SKIN.
The skin is able to perform the following functions.
1. Protection
2. Sensibility
3. Excretion.
4. Regulation of body temperature
5. Production of milk
6. Storage of food.
🔰 Regulations of body temperature by the skin, On hot days, there is a rise in body temperature which brings about the following processes to get rid of excess body heat.
A. Vasolidation : Dilation of capillaries near the skin surface and constriction of these in the deeper layer leaving to large flow of blood near the surface so that heat is lost through convention and radiation.
B. Sweating : In human, the sweat gland become active and become a large amount of sweat which flows out of the surface of the skin, as this evaporate. It is use up, thus pulling the body.
C. Decrease Metabolic Waste : The body slopes down its activities of metabolic rate.
D. Lowering of hairs : During hot days, the air on the skin lie down flat on the skin.
E. Behavioural Changes.
🔰 There is a fall in body temperature on cold days, leaving to the following processes to produce and conserve heat.
A. Vasoconstriction : Capillaries near the skin constrict while does in the deeper layer dialect causing a smaller volume of blood to flow near the skin so that heat is reduce in order to conserve body heat.
B. Sweating : The sweat gland becomes less active and produce small amount of sweat.
C. Increasing Metabolic rate.
D. Raising of hairs.
E. Behavioural changes such as staying indoors, hurdling into ball, wearing of sweater and winter jacket, using of robs.
🔰 CARE OF THE SKIN.
The skin can be maintained by the following activities :
1. Regular cleaning such as bathing twice a day.
2. Exposure of the skin to fresh air.
3. Eating balanced diet.
4. Proper treatment of skin diseases such as Eczema, small pox, chicken pox etc.
5. Wearing of clean clothes.
6. Regular Exercise.
7. Dressing of wound and cut.
8. Avoiding of the use of injurious chemicals.
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