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  1. 1. The structure of mammalian skin Epidermis DermisSubcutaneous layer of fat
  2. 2. Function of the adipose/fat layer:1. provides a store of energy2. forms an insulating layer: prevents heat loss Subcutaneous layer of fat
  3. 3. Question: Sep, 2011Give a biological explanationfor each of the following:Aquatic mammals such aswhales have a thick layer ofblubber. (3)
  4. 4. 3 layers in epidermis: cornified granular malpighian
  5. 5. New skin cells are made all the time at the : cornified granular malpighian
  6. 6. Growth of the epidermis: cornified4 The dead cells become hard and flat and flake off. The cells are cut3 off from the blood granular supply and so die. 2 This cell enters the granular layer. Cells in this layer malpighian1 divide to produce two cells.
  7. 7. Functions of the cornified layer:i) reduces water lossii) keeps out microbes Cornified layer dead cells
  8. 8. Function of the malpighian layer: cells divide by mitosis to form the granular layer Granular layer Malpighian layer: produces melanin
  9. 9. Functions of melanin:1. absorbs ultraviolet rays2. gives colour to the skin
  10. 10. What is present in the dermis? sensory nerve endings sweat glands hair follicles capillaries Let’s f ind outthe f unction of each.
  11. 11. Where are the sensory nerve endings located?
  12. 12. Receptors serve as receivers for the body, keeping it informed of changes in its environment.
  13. 13. What is present in the dermis? sensory nerve endings sweat glands hair follicles capillaries
  14. 14. sweat pore evaporationSectionthrough skin epidermis The sweat gland dermis extracts sweat from the blood and passes it up sweat duct the duct to the skin surface where it evaporates sweat gland blood vessel 0.25 mm
  15. 15. Question: SEP, 2010What is sweat made up of? (3)  Water  Salts  Urea  A little lactic acid
  16. 16. Sweat cools the body as it evaporates The skin
  17. 17. Evaporative cooling Hippos bathing
  18. 18. Explain why a person is advised to take a salt tablet after staying in the sun for a long time. To replace salts lost in sweat.
  19. 19. Question: SEP, 2010On hot days the volume of urine lost is lessthan on cold days. Explain why. (4) Cold days:Hot days: No/less sweatWater lost in sweat
  20. 20. Urine changes colourThe more dilutethe urine is, the lighter is its colour.
  21. 21. What is present in the dermis? sensory nerve endings sweat glands hair follicles capillaries
  22. 22. A hair follicle is a deep pit lined with granular and malpighian cells Hair Hair follicleBlood vessels
  23. 23. It is not painful to cut your hair. Why? Hair is made of dead cells.Human hair:made of the protein keratin
  24. 24. Hair erector muscle Erector Thicker layer of muscleThinner layer of air is trapped. contracted air is trapped. Hot day Cold day
  25. 25. Head louse clings to hair
  26. 26. Thickness of fur varies according to season
  27. 27. Sebaceous / Oil glandproduce sebum - waterproof
  28. 28. What is present in the dermis? sensory nerve endings sweat glands hair follicles capillaries
  29. 29. Capillaries: bring food and oxygen to the skin and remove wastes capillary loops near the skin surface are important in controlling temperature
  30. 30. Cold Hot dayday
  31. 31. VasodilationIf thetemperaturerises, the bloodvessel dilates(gets bigger). This means more heat is lost from the surface of the skin
  32. 32. VasoconstrictionIf thetemperaturefalls, the bloodvessel constricts(gets shut off). This means less heat is lost from the surface of the skin
  33. 33. Give a reason for this observation. A child looks pale in the face on a cold day but red after running a race.Vasoconstriction to Vasodilation to reduce heat loss. increase heat loss.
  34. 34. Spot 3 ways shown in the diagramthat help cool the body on a hot day. Cold 1 Hot 2 3
  35. 35. 5 functions of the skin:1. Protection – barrier to microbes reduces water loss absorbs UV rays
  36. 36. 5 functions of the skin:2. Sensationsensory cells make the bodyaware of the changes around itthrough pain, touch, heat coldand pressure
  37. 37. 5 functions of the skin:3. Formation of vitamin Dby the action of sunlight on the skin
  38. 38. 5 functions of the skin:4. Temperature regulationhelps to keep a constant body temperature5. Excretionremoves urea in sweat
  39. 39. Question: Sep, 2011Give a biological explanation for each of thefollowing: African elephants flap their large ears frequently in hot weather. (4)
  40. 40. Balance in heat gain and heat loss HEAT GAIN HEAT LOSS
  42. 42. Ways to GAIN heat 1) INTERNAL CHANGES i) reactions release heat ii) muscular contractions release heat IRATIONRESP
  43. 43. Ways to GAIN heat2) EXTERNAL CHANGESi)body absorbs heat if temperature is more than 37°Cii) hot foods and drinks add heat
  44. 44. Ways to LOSE heata)conduction, convection, radiationb) evaporation of sweatc) cold air inhaledd) cold drinks and food
  45. 45. Find the SA:Vol of the cubeArea of 1 side = length x width = 1 x 1 = 1 cm2Area of 6 sides = 1 x 6 = 6 cm2Volume = length x width x height= 1 x 1 x 1 = 1 cm3 Surface area to volume ratio = 6:1
  46. 46. Find the SA:Vol of the cubeArea of 1 side = 2 x 2 = 4 cm2Area of 6 sides = 4 x 6 = 24 cm2Volume = 2 x 2 x 2 = 8 cm3 Surface area to volume ratio = 3:1
  47. 47. What happens to the SA:Vol ratio as the cube increases?
  48. 48. 2 cubes were immersed in a dye for the same amount of time. They were removed and cut in half. Explain the result.
  49. 49. Rate of diffusion is the same in all cubes BUT distance to centre is different
  50. 50. A LARGE organism has a small surface area to volume ratio which means:1. little heat is lost2. cannot take in oxygen from the body surface by diffusion
  51. 51. Curling up when cold reduces surface area for heat loss
  52. 52. A large organism needs a:  Circulatory system  Breathing system Why does an amoeba lack a circulatory system?Being small, it has a large surface area tovolume ratio. Materials reach all parts ofthe cell quickly.
  53. 53. A SMALL organism has a large surface area to volume ratio which means:1. a lot of heat is lost2. can take in oxygen from the body surface by diffusion
  54. 54. Which animal has thehigher metabolic rate?
  55. 55. Arctic animals  Are large  Have small ears  Thick fur
  56. 56. Two species of Lepus adapted to live at different temperatures. Explain how.
  57. 57. A baby and an adult, both naked,are placed in a room at a lowtemperature. Which one loses heatfaster and dies first? Why?Small body- Large body-large SA: Vol ratio small SA: Vol ratio
  58. 58. Rule is: LARGE animals in cold climates SMALL animals in hot climatesLarge body- Small body- little heat loss large heat losses
  59. 59.  fish, reptiles, amphibians and invertebrates absorb heat from their surroundings - this is called basking are poikilotherms Marine iguana basking
  60. 60.  birds and mammals produce heat inside their bodies are homeotherms
  61. 61. Endotherms insulate their body by: Feathers FurBlubber
  62. 62. Question: MAY, 2011Give a biological explanation for each of the followingsituations:a)A volunteer student sat in a sauna (a chamber witha temperature reaching 80°C for an hour. Sweatproduction increased rapidly. (3)
  63. 63. Increase in external environmentaltemperature will result in an increase in theinternal body temperature.Body produces sweat to regulate the internaltemperature.Evaporation of sweat cools down the bodytemperature.
  64. 64. Question: MAY, 2011Give a biological explanation for each of the followingsituations:b) A young child falls in a frozen lake in winter. Thechild starts shivering vigorously after being pulled outof the lake. (4)
  65. 65. Muscles contract and relax quickly – thisproduces heat.The heat generated in the muscles warms theblood as it flows through them.The blood distributes this heat all over thebody.
  66. 66. Question: MAY, 2011List THREE ways by which the parents of a childwho fell in a frozen lake in winter can preventfurther heat loss. (3)
  67. 67.  Provision of dry clothes/moving child next to a warm environment such as a heater/removing cold clothes and covering child with a blanket/ Help child to take a warm bath Provide a warm drink or fluid such as soup.
  68. 68. Question: SEP, 2010Give a biological explanation for each of thefollowing statements:In cold weather we tend to shiver and eatmore. (3)Shiver: to produce heatEat more: higher rate of respiration = moreheat
  69. 69. So cool!! THE END