Skin homeostasis


Published on

  • Be the first to comment

No Downloads
Total views
On SlideShare
From Embeds
Number of Embeds
Embeds 0
No embeds

No notes for slide

Skin homeostasis

  1. 1. Guess the topic of the next presentation… * Its total surface is 1.80 m2 * It is the first line of defense from external factors. * It’s water resistant * *It keeps our extra kilos in secret, although it weighs 3 - 4 kilos * We “gotta feeling” thanks to it
  2. 2. Some English idioms with it be --------- and bone/bones : to be extremely thin Beauty is only ----------- deep : a person's character is more important than his/her appearance by the ----------------- of one's teeth Fig. just barely. give someone some -------------------- Sl. [for two people] to touch two hands together in a special greeting, like a handshake. (One hand may be slapped down on top of the other, or they may be slapped together palm to palm with the arms held vertically. There's more than one way to --------------- a cat. Prov. You can always find more than one way to do something. (nearly) jump out of one's ---------------- Fig. to react strongly to shock or surprise.
  3. 3. I’ve got you under my SKIN
  4. 4. Skin structure • Epidermis Basal layer Cornified layer • Dermis • Hypodermis •The deepest layer, one cell thick. • made up of basal keratinocyte cells (stem cells of the epidermis) that produce keratin and melanocytes that produce MELANIN • Cells % by mitosis, move towards surface, die and fill up with KERATINE *Top layer *Hard and waterproof *Made of dead cells *Always worn away (every 28days) and replaced Melanin UV rays Fold Hair follicle CONNECTIVE TISSUE + elastic fibres COLLAGEN/ ELASTIN +sweat glands +sebaceous glands produce sebum keeps the skin and hair from drying out and inhibits the growth of certain harmful bacteria +blood vessels +nerve endings +hair follicles Layer of adipose tissue Food reserve/ insulation
  5. 5. Differences in skin color result from differences in the amount of melanin produced and how melanosomes, packets of melanin, are arranged in the keratinocytes. Particularly in people with light skin, melanin sometimes accumulates in patches, forming freckles, age spots, or liver spots.
  6. 6. A total lack of melanin, a genetic condition called albinism, makes people extremely sensitive to the sun. People with albinism have very light skin, hair, and eyes.
  7. 7. The color of hair is due to melanin. Dark hair contains true melanin like that found in the skin. Blond and red hair result from types of melanin that contain sulfur and iron. Hair goes grey when melanocytes age and lose the enzyme necessary to produce melanin.
  8. 8. NAILS Nails on the fingers and toes are made of hard, keratin-filled epidermal cells. They protect the ends of the digits from injury, help us grasp small objects, and enable us to scratch.
  9. 9. Functions of the skin 1.Protection: a)an anatomical barrier from pathogens and damage between the internal and external environment b)it reduces WATER LOSS c)Melanin protects from UV rays 2.Sensation: contains a variety of nerve endings that jump to heat and cold, touch, pressure, vibration, and tissue injury SENSITIVITY 3.Heat regulation: increase perfusion and heatloss, while constricted vessels greatly reduce cutaneous blood flow and conserve heat. 4.Control of evaporation: the skin provides a relatively dry and semi- impermeable barrier to fluid loss. 5.Storage :acts as a storage center for lipids and water 6.Water resistance: barrier so essential nutrients aren't washed out of the body. The nutrients and oils that help hydrate our skin are covered by our most outer skin layer, the epidermis. This is helped in part by the sebaceous glands that release sebum, an oily liquid.
  10. 10. We are safe!!!
  11. 11. How long could the people have remained alive in the water? On the night of the Titanic sinking, the temperature of the salt water was likely around 28° F(-2 °C). The human body loses heat to the water about 30 times faster than it does to the air. When the core body temperature falls to approximately (31°C), a decrease in consciousness occurs. If the core temperature cools to below 86° F(30°C) then heart failure becomes a major concern, as it is the most common cause of hypothermia-related deaths. The people in the -2 °C water above the sinking Titanic would have had anywhere from several minutes to an hour to live, depending on their physical condition and how much they flailed. Some people in the water might have believed that swimming would help their body to generate heat. In reality, people who swam or moved around a lot would have lost heat 35-50% faster and been susceptible to exhaustion. There were even several people who died from hypothermia in the Titanic lifeboats, because they were open and gave no protection against the cold. Regulations have since been put in place that require lifeboats to be fully or partially enclosed.
  12. 12. Temperature Control * Normal human body temperature varies between -------------- and --------- * CORE TEMPERATURE * Heat is lost by * Heat is gained by IN BALANCE IF NOT OVERHEATINGOVERCOOLING 1) 2) 1) 2) 3) 4)
  13. 13. The term ‘homeostasis’ is derived from two Greek words; Homeo which means ‘unchanging’ and Stasis which means ‘standing’ In its simplest form it means ‘staying the same’ It is an organism’s internal environment which ‘stays the same’ The ‘internal environment’ refers to the conditions inside an organism. These conditions remain more or less constant despite changes such as pH or temperature in the outside environment So, a better definition of ‘homeostasis’ is t ---- m----------------------- o- t---- i ----------------------------- e---------------------- w-------------------- n------------------- l--------------------. 2 Homeostasis and negative feedback What for?????????
  14. 14. How do they regulate their temperature? * They are ------------------- * They regulate their temperature by---- If their body temperature falls------------- *We are ------------------- *The “price” we pay is ---------- *The ----------------------------- is the thermoregulatory centre. It has TWO functions: a) b) Why is the process of controlling the temperature is an example of NEGATIVE FEEDBACK????
  15. 15. The skin, kidneys, liver, endocrine system, nervous system and sensory system all play a part in maintaining the internal environment within narrow limits
  16. 16. 2)To carry out its living processes, every cell in the body needs a supply of oxygen and food. Waste products such as carbon dioxide have to be removed before they reach harmful levels and damage the cell These conditions are maintained by tissue fluid bathing the cells. Tissue fluid is derived from the blood 1) The skin is a homeostatic organ which helps maintain the body temperature within the limits given in the previous slide 3) In the cells, the chemical breakdown of proteins produces the nitrogenous compound, urea. If this were allowed to accumulate in the cells it would damage or kill them. The concentration of the blood and tissue fluids tends to vary. If water is lost through evaporation and sweating, the fluids become more concentrated. The intake of water dilutes the fluids These homeostatic functions are carried out by the kidneys 4)The LUNGS keep the concentration of Oxygen and Carbon dioxide in the blood for the cell’s reactions (respiration)
  17. 17. 5) The glucose concentration in the blood is controlled by the pancreas The pancreas contains cells which produce digestive enzymes but it also contains cells (alpha and beta cells) which produce the hormones insulin and glucagon If the glucose concentration rises, the beta cells release insulin If the glucose concentration falls, the alpha cells release glucagon 12 In this way, the concentration of glucose in the blood is kept within narrow limits Insulin stimulates and to remove excess glucose from the blood and store it as glycogen Glucagon stimulates to convert its stored glycogen into glucose which is then released into the bloodstream
  18. 18. The blood system maintains the composition of the tissue fluid cells carbon dioxideglucose oxygen carbon dioxidetissue fluid fluid filtered out of capillary tissue fluid enters capillary blood flowBlood and tissue fluid 9