Homeostasis and excretion are related processes where homeostasis refers to maintaining a constant internal environment and excretion refers to removing metabolic waste products. The skin, lungs, liver, and kidneys are organs that help maintain homeostasis by regulating processes like temperature, water balance, and removal of toxins. The skin specifically regulates temperature through blood flow, sweat glands, and erector muscles in the dermis and helps remove some waste through sweat.

1. Homeostasis & Excretion LPK TB Chapter 12 & 11 1

2. Homeostasis is … Excretion is … How are homeostasis and excretion related? 2

3. In the case of these fishes… Homeostasis is somewhat like how Salty Sail maintains the water potential of his cells. Drinking a lot of water and Excreting salt is the way he achieves it. 3

4. Definition Homeostasis is the maintenance of a constant internal environment. e.g. Body temperature, blood glucose concentration & blood water potential Excretion is the process by which metabolic waste products and toxic materials are removed from the body of an organism. 4

5. Principle of Homeostasis Normal/Ideal condition when it becomes Not normal/ideal Sends a Which allows condition to go back to Stimulus to Receptor Activates Corrective Mechanism e.g. Excretion Which causes Response/Changes e.g. negative feedback 5

7. What are the organs involved in maintaining homeostasis in our body? Lungs Liver Kidney Skin Excretory organs 7

8. 8

9. THE SKIN 9

11. Describe the functions of parts of the skin

12. Describe the maintenance of a constant body temperature in humans10

13. Structure of the Mammalian Skin 7 6 8 6) Sense receptors 7) Blood vessels 8) Hair 5 5) Sweat pore 9 4) Hair follicle 9) Sebaceous gland 4 1 1) Epidermis 10 2 10) Erector muscle 2) Dermis 11) Sweat gland 3 3) Subcutaneous fat 11 11

15. Removes excess salts, water and urea in the form of sweat

16. Temperature regulation

17. to maintain a constant body temperature

18. Sense organ

19. Detect pain, pressure changes and temperature

20. Protective covering Prevents entry of bacteria, protects from mechanical damage and excessive loss of water by evaporation 12

23. contains living cells which is gradually pushed up to replace the worn-out cells in the cornified layer 14

25. contains actively dividing cells to produce new epidermis

26. contains melanin pigments that gives skin its colour and absorbs ultraviolet radiation 15

28. More obvious in fair-skinned people.

29. Freckles become more prominent when exposed to sunlight because the skin produces extra melanin in sunny conditions.16

31. Detect pain, changes in temperature and pressure on skin

32. Hair follicle and hair

36. Regulate temperature by vascular constriction or dilation19

38. sebum builds up in clogged pores

39. Sebaceous glands continue to produce sebum but it has no where to go 

41. Why are tattoos permanent? 22 What you see when you look at a tattoo is the ink that's left in the skin after the tattooing. The ink is not in the epidermis, which is the layer of skin that we see and the skin that gets replaced constantly, but instead intermingles with cells in the dermis and shows through the epidermis. The cells of the dermis are remarkably stable, so the tattoo's ink will last, with minor fading and dispersion, for your entire life!

43. dissolved sodium chloride

44. urea23

45. Sweat is secreted by the sweat gland. It travels through the sweat duct and out onto the skin via the sweat pore. 24

46. Test Yourself Which part of the skin regulates the following functions? Epidermis Protection from harmful agents of external environment: biological germs, UV light & chemicals Subcutaneous fat Shock absorber Blood vessels & sweat glands Temperature regulation Subcutaneous fat Insulation Nerve endings Sensation Sebaceous glands Lubrication Subcutaneous fat Calorie reserve Epidermis Vitamin D synthesis Sweat glands Body odour 25

47. Which part of the skin contributes to thermal homeostasis? Epidermis Protection from harmful agents of external environment: biological germs, UV light & chemicals Subcutaneous fat Shock absorber Blood vessels & sweat glands Temperature regulation Subcutaneous fat Insulation Nerve endings Sensation Sebaceous glands Lubrication Subcutaneous fat Calorie reserve Epidermis Vitamin D synthesis Body odour Sweat glands 26

48. 27 Q. What do we call animals which keep their body temperature at a roughly constant level, regardless of the environment’s temperature? Warm-bloodedness generally refers to three separate aspects of thermoregulation. Endothermy (control via internal means strictly - metabolism) Homeothermy (thermoregulation within regardless of external influence; opposite = poikilothermy) Tachymetabolism (high resting metabolism rate)

49. Reptile Mammals Birds Fish Amphibian Invertebrates Animals “Warm blooded”/ Homoiothermic “Cold blooded”/ Poikilothermic 28

50. 29

51. Mechanisms in warm-blooded creatures 30

52. Metabolic rate slows down 4 3 Erector muscle 1 2 Arterioles In hot conditions  Less heat is produced Arterioles in skin dilate Sweat gland active  More blood and more heat send to skin Erector muscles relax  As sweat evaporates, latent heat lost  Hair lie flat, close to skin 31

53. Metabolic rate speeds up 5 4 Erector muscles 1 2 Shivering occurs 3 In cold conditions Arterioles  More heat is produced Erector muscles contract  Hairs trap a layer of air close to skin. Arterioles in skin constrict Sweat gland inactive  Less blood and less heat send to skin 32

54. Principle of Homeostasis Normal temperature when it becomes Too Hot Too Cold Heat receptors on skin sends Stimulus Which allows condition to go back to Which allows condition to go back to to Hypothalamus causes Arterioles constrict Arterioles dilate Which leads to Increased heat loss Reduced heat loss 33

56. Recap - What is excretion? Excretion is the process by which metabolic waste products and toxic materials are removed from the body of an organism. 35

57. Q1. What is metabolism? Excretion is the process by which metabolic waste products and toxic materials are removed from the body of an organism. Chemical activities of the cells which keep the organism alive Anabolic C a t a b ol I c 36

58. 37 Metabolic + Anabolic Catabolic =

59. Metabolic Waste Products substances left over from excretory processes cannot be used (surplus/lethal effect) must be excreted. E.g.Nitrogen compounds, water, CO2, phosphates, sulfates, medicals, food additives 38

60. Q2. Why must living organisms excrete metabolic waste products? Accumulation of these substances Can interfere with proper functioning of cells Change the concentration of tissue fluid around cells 39

61. Q2.1 What is the difference between excretion and egestion? Excretion ≠ Egestion (metabolic waste) (undigested waste) 40