1. EXCRETION

2. DEFINITION
Excretion is the release of metabolic waste substances from the body.
Metabolic waste are ingested substances that have been altered by the body before its accumulation and subsequent release e.g. proteins to amino acids.

3. EXCRETORY PRODUCTS OF PLANTS
Oxygen: from photosynthesis (day)
Carbon dioxide: from respiration (night)
Water: from respiration (night)
Nitrogenous compounds: tannins, alkaloids
Calcium oxalate: solid waste products

4. EXCRETORY MECHANISMS IN PLANTS
Stomata and lenticels for the diffusion of waste gases out of the plant
Nitrogenous compounds and calcium oxalate are stored in dead permanent tissue e.g. leaves bark, flowers, fruits, seeds and will fall off the tree to be excreted.

5. EXCRETORY PRODUCTS IN HUMANS
CO2, water, heat: from resp.
N2 compounds from deamination of amino acids
Bile pigments from haemoglobin break-down in the liver
Ions from nutrient metabolism
Heat from metabolism

6. ORGANS OF EXCRETION The human excretory organs are:
Lungs – carbon dioxide
Liver – bile, urea
Skin – sweat, heat
Kidney – urine, salts, excess water, urea

7. LUNGS
After respiration, the lungs excrete the carbon dioxide and water that are the by-products.
This therefore utilizes breathing and gaseous exchange.
Why are nitrogen and inert gases not said to be excreted?

8. LIVER
Deamination of excess amino acids to form carbohydrates (stored) and urea (excreted).
Detoxification of poisons such as drugs, alcohol.
Breakdown of red blood cells; haemoglobin is broken down to form bile pigments bilirubin and biliverdin.

9. LIVER
The liver excretes excess proteins from the body by removing the amino (NH) groups and then storing the carbohydrate portion.
The amino region is converted to urea and is released in the sweat and urine. This is called deamination.
The carbohydrate is stored as glycogen for later use.

10. Homework
List the ten functions of the liver into your notebooks. Pages green text.
Read through the details of each point for your own knowledge base.

11. DEAMINATION

12. SKIN The skin excretes salts, urea and water from the pores as sweat.
Sweat glands are located in the dermis and then emerge at the surface of the epidermis as pores.

14. URINARY SYSTEM

15. THE KIDNEYS AND URINARY SYSTEM

18. The urinary system is composed of
the kidneys which make urine
the ureters which are tubes (one from each kidney) that carries urine to the
bladder which temporarily stores urine until ready to leave the body through the
urethra in the penis or vagina.

19. the kidneys which make urine
the ureters which are tubes (one from each kidney) that carries urine to the
bladder which temporarily stores urine until ready to leave the body through the
urethra in the penis or vagina.

20. The renal artery carries oxygen and nutrient rich blood to the kidneys
The renal vein carry deoxygenated, filtered blood to the heart.

21. Urinary Show Follow this link to the kidney show. LINK
HOW THE KIDNEY WORKS

22. The kidney itself is composed of
the outer cortex
the inner medulla that pinches off into structures called
the pyramids that all point towards
the pelvis which is the upper region of
the ureter which carries urine from the kidney then to the bladder.

24. the outer cortex
the inner medulla that pinches off into structures called
the pyramids that all point towards
the pelvis which is the upper region of
the ureter which carries urine from the kidney then to the bladder.

26. THE NEPHRON
Although they seem solid, the kidneys are made up of thousands of tiny tubules called nephrons.

28. THE NEPHRON Other names for the nephron include:
kidney tubules or uriniferous tubules. 28

29. THE NEPHRON

30. THE NEPHRON
Each nephron begins in the cortex, loops down into the medulla, back into the cortex and then goes down through the medulla to the pelvis where the nephrons join up with the ureter.

31. URINE IS MADE FROM BLOOD
Urine contains the waste our kidneys filter from our blood.
The nephrons filter blood under high pressure (ultrafiltration).
The waste is removed as the filtrate (urine) and useful substances are left behind or reabsorbed.

32. COMPARE BLOOD TO URINE COMPONENTS OF BLOOD COMPONENTS OF URINE Urea
Salts
Water
Red Blood cells
White Blood cells
Proteins
Glucose
Hormones
Amino acids
All Urea
Some salts
Some water
None
None (may be diabetic if present)
Small amounts possible

35. The nephron has five regions:
The Bowman’s capsule
The proximal convoluted tubule
The Loop of Henlé
The distal convoluted tubule
The collecting duct
The five regions of the nephron help cleanse the blood in the following way:

36. BOWMAN’S CAPSULE
the Bowman’s capsule in which ultrafiltration of blood occurs under high pressure.

37. PROXIMAL CONVOLUTED TUBULE
the proximal convoluted tubule where 80% selective reabsorption occurs

39. LOOP OF HENLE
the Loop of Henlé where mainly water is reabsorbed from the collecting ducts in order to concentrate urine.

40. DISTAL CONVOLUTED TUBULE
the distal convoluted tubule where the remaining substances are reabsorbed.

41. COLLECTING DUCT
the collecting duct in which more than one nephron may empty its urine into to be carried to the ureters

42. NEPHRON FUNCTION REGION OF NEPHRON FUNCTION Bowman’s capsule
Ultrafiltration (glomerular filtrate contains water, glucose, amino acids, vitamins, hormones, salts and UREA)
Proximal convoluted tubule
Selective reabsorption (80% of water, glucose, salts and amino acids; most hormones and vitamins.)
Loop of Henle
Selective reabsorption (6% of mainly water)
Distal convoluted tubule
Selective reabsorption (13% of water, glucose, amino acids and salts)
Collecting duct
Collection of urine (1% remaining filtrate)
Capillaries around nephron
Selective reabsorption

43. ULTRAFILTRATION
Thin-walled, porous glomeruli rest inside each Bowman’s capsule.
Blood passing through the narrow glomerulus from the wider afferent arteriole is under such high pressure that the blood is squeezed against the glomerular walls and tiny molecules can squeeze out through their pores forming a glomerular filtrate.
Glomerular filtrate contains water, salts, glucose,amino acids and urea.

45. USEFUL SUBSTANCES ARE REABSORBED
Some of the water, salts and amino acids and all of the glucose are needed by the body so cannot be left as filtrate to make urine.
They must be reabsorbed and do so as they travel along the length of the nephron.
Blood capillaries leading back to the renal vein wrap around each nephron for reabsorption of substances.

46. These capillaries reabsorb the useful substances from the nephron and empty them into the efferent arteriole that joins up with the vein.
This takes the useful substances back to the bloodstream.

48. Urine: The Movie
THE KIDNEYS AND THE NEPHRON

49. Recap

50. Suppose the kidney stop working

51. HOMEOSTASIS

52. Keeping the internal environment of the body constant.
This is done by
Kidney- osmoregulation (water)
Pancreas and liver- glucose concentration
Lungs- carbon dioxide concentration
Skin- body temperature

53. OSMOREGULATION

55. How do we gain water
Drinking
Eating
Osmosis (plants)

56. How do we lose water?
Sweating
Urinating
Breathing out

57. Too much water in the blood (dilute) water enters cells by osmosis which may swell and burst.
Too little water in the blood (concentrated) water leaves cells by osmosis and may shrink leaving the body dehydrated.

58. KIDNEYS Too little water
Hypothalamus detects and signals pituitary gland to secrete more ADH
ADH goes to kidneys and make the capillaries around the nephron more permeable
More water is therefore reabsorbed to bring balance.
Urine produced is in small amount and very concentrated (yellow).

59. TOO MUCH WATER? WHAT HAPPENS?
Hypothalamus detects and signals pituitary gland to secrete less ADH
Less ADH goes to kidneys and so the capillaries around the nephron are less permeable
Less water is therefore reabsorbed to bring balance.
Urine produced is in larger amount and very dilute (clear and colourless).

60. DIALYSIS Kidneys damaged by injury or infection. Can survive with one.
Can be donated to a “matched” person.
If both kidneys fail, dialysis is done for up to 10 hours every few days.
Dialysis fluid is same conc. as healthy blood so anything in excess will diffuse from the blood into the fluid before re-entering the body.

63. HOMEOSTASIS

64. What is Homeostasis?
Homeostasis is the maintaining of a constant environment inside the body regardless of external changes.

65. Feedback mechanisms keep many aspects of the internal environment constant.
BLOOD passing through the HYPOTHALAMUS of the brain containing too much or too little of a particular SUBSTANCE causes the HYPOTHALAMUS to send impulses to appropriate ORGANS causing them to return the level to NORMAL.
This is known as NEGATIVE FEEDBACK.

66. If the corrective mechanism FAILS and the level cannot be returned to normal, the increase or decrease will continue.
This is known as POSITIVE FEEDBACK and is rare in living organisms since it often causes DEATH.

68. WATER CONCENTRATION IN BLOOD
One example of homeostasis is osmoregulation where the pituitary gland secretes more or less Anti-diuretic hormone (ADH) to control the amount of water in the blood/body by causing more or less urine to be made and released.

69. WATER CONCENTRATION IN BLOOD

70. WATER CONCENTRATION IN BLOOD

71. BODY TEMPERATURE
Another example of homeostasis brings body temperature back to normal if our surroundings get too hot or cold.

72. BODY TEMPERATURE

73. BODY TEMPERATURE

74. BODY TEMPERATURE

75. GLUCOSE LEVELS
Another example of homeostasis keeps blood sugar (glucose) levels normal if we eat too much or too little.

76. GLUCOSE LEVELS

77. GLUCOSE LEVELS

78. CO2 LEVELS IN BLOOD
Another example of homeostasis keeps the level of carbon dioxide in our blood normal.

79. CO2 LEVELS IN BLOOD

80. CO2 LEVELS IN BLOOD

81. Too much water in the blood causes cells to absorb it by osmosis, swell and burst.
Too little water in the blood causes cells to lose water and shrivel.

82. Being too cold is HYPOTHERMIA and this causes the heart and breathing rate to slow until death.
Being too hot is HYPERTHERMIA and this causes the body to overheat and can cause stroke.

83. Too much sugar in the blood is a sign of diabetes and can lead to excessive thirst, nerve damage and blindness.
Too little sugar in the blood can stare the brain and lead to blackouts, coma and death.

84. Too little CO2 in the blood will not trigger the breathing system to take breaths.
Too much CO2 in the blood can lead to a build up of carbonic acid that can become toxic.

85. NEGATIVE FEEDBACK
The way in which these organs respond to changes in the environment by brining the body back to the norm is called a negative feedback mechanism.

86. SKIN When a person gets too hot they start to Sweat
Vasodilation occurs
The hairs lie flat

87. When a person gets too cold:
They shiver
Vasoconstriction occurs
The hairs stand upright

88. USE THIS DIAGRAM TO PRACTICE DIFFERENT FEEDBACKS

89. OSMOREGULATION

90. TEMPERATURE REGULATION

91. TEMPERATURE REGULATION

92. GLUCOSE CONCENTRATION

93. CO2 CONCENTRATION