1. Ch 38-2 The Process of Digestion
By the end of this section you should be able to:
Identify the organs of the digestive system
Describe the function of the digestive system

2. Ch 38-2 The Process of Digestion
alimentary canal – one-way tube that passes through the body

3. Ch 38-2 The Process of Digestion
digestive system – helps convert foods into simpler molecules that can be absorbed and used by the cells of the body

4. Ch 38-2 The Process of Digestion
– includes:
mouth pharynx esophagus small intestine
 large intestine stomach 

5. Ch 38-2 The Process of Digestion
accessory structures: add secretions to the digestive system
 pancreas liver  salivary glands

6. Ch 38-2 The Process of Digestion

7. Ch 38-2 The Mouth
mechanical digestion – physical breakdown of large pieces of food into smaller pieces

8. Ch 38-2 The Mouth
chemical digestion – breakdown of large food molecules into smaller food molecules with digestive enzymes

9. Ch 38-2 The Mouth
mouth – the organ in which digestion begins
teeth – tear and crush food into a fine paste until it is ready to be swallowed
– anchored to the bones of the jaw; protected by a coating of enamel
– do much of the mechanical digestion

10. Ch 38-2 The Mouth
saliva – secreted by salivary glands as the teeth cut and grind food
– secretion is controlled by the nervous system; can be triggered by scent

11. Ch 38-2 The Mouth
three functions:
1) helps to ease the passage of food through the digestive system by moistening food
2) contains lysozyme – an enzyme that fights infection by digesting the cell walls of bacteria that enter the mouth
3) contains amylase – begins to break the bonds in starches to produce simpler sugars

12. Ch 38-2 The Esophagus
bolus – chewed clump of food that is pushed down the throat by the tongue and throat muscles
epiglottis – flap of tissue that covers the trachea when swallowing to prevent food from entering lungs

13. Ch 38-2 The Esophagus
esophagus – tube that connects the throat (pharynx) to the stomach
– walls are made of ringed muscle that squeeze food through the tube
– peristalsis – the rhythmic muscular contractions of the smooth muscle in the digestive system that pushes food along

14. Ch 38-2 The Esophagus
cardiac sphincter – also called esophageal sphincter
– a thick ring of muscle that closes the esophagus after food has passed into the stomach
– prevents the contents of the stomach from moving back into the esophagus

15. Ch 38-2 The Esophagus
heartburn – backflow of stomach acid across the cardiac sphincter
– can be caused by overeating, overdrinking, or excess caffeine

16. Ch 38-2 The Stomach
stomach – large, muscular sac just below the diaphragm in the abdomen
– three layers of smooth muscle
– churns and mixes the food that is swallowed

17. Ch 38-2 The Stomach
chemical digestion – stomach is lined with millions of microscopic gastric glands that release a number of substances into the stomach

18. Ch 38-2 The Stomach
gastric secretions include:
1) mucus – lubricates food and protects the stomach lining
2) HCl – hydrochloric acid makes the stomach contents acidic which allows pepsin to work

19. Ch 38-2 The Stomach
gastric secretions include:
3) pepsin – enzyme that begins the digestion of protein
– works best in acidic environments
– breaks proteins into smaller polypeptide fragments

20. Ch 38-2 The Stomach
the acidic environment denatures (“changes the shape of”) the amylase enzyme, so carbohydrate digestion stops in the stomach (it restarts in the small intestine)

21. Ch 38-2 The Stomach
mechanical digestion – muscular walls of the stomach contract to churn and mix stomach fluids and food to produce chyme
▫ chyme – a pasty mixture of food that results after 2 to 3 hours of churning in the stomach

22. Ch 38-2 The Stomach
pyloric valve – a ring of muscle between the stomach and small intestine
– opens to allow chyme to flow into the small intestine

23. Ch 38-2 The Stomach

24. Ch 38-2 The Small Intestine
three sections:
duodenum
jejunum
3) ileum

25. Ch 38-2 The Small Intestine
duodenum – first of the three parts of the small intestine
– where almost all of the digestive enzymes enter the intestines
– chyme mixes with enzymes and digestive fluids from the pancreas, liver, and the lining of the duodenum

26. Ch 38-2 The Small Intestine
intestinal secretions
1) peptidase – breaks down dipeptides into amino acids
2) maltase, sucrase, and lactase – breaks down remaining disaccharide into monosaccharides

27. Ch 38-2 The Small Intestine
accessory structures:
 pancreas – long gland located behind the stomach
– gland that serves three functions:
1) produces hormones that regulate blood sugar levels
 2) produces enzymes that break down carbohydrates, proteins, lipids, and nucleic acids

28. Ch 38-2 The Small Intestine
3) produces sodium bicarbonate to neutralize HCl from stomach acid – because pancreatic enzymes only work in a neutral environment

29. Ch 38-2 The Small Intestine
liver – large, brownish organ located just above and to the right of the stomach
– secretes bile – yellow-brown liquid loaded with lipids and salts
– acts like a detergent - breaks fat into smaller and smaller droplets which make it possible for enzymes to reach more surface area

30. Ch 38-2 The Small Intestine
gallbladder – pouch-like organ behind the liver that stores bile

31. Ch 38-2 The Small Intestine

32. Ch 38-2 Absorption in the Small Intestine
jejunum and ileum – last two sections of the small intestine
– approximately 6 meters long
– at this point chemical digestion is complete

33. Ch 38-2 Absorption in the Small Intestine
– nutrient molecules are absorbed from these two sections into the bloodstream
– peristalsis move the chyme along the jejunum and ileum

34. Ch 38-2 Absorption in the Small Intestine
villi – finger-like projections that increase the surface area of the walls of the small intestine

35. Ch 38-2 Absorption in the Small Intestine
microvilli – thousands of even tinier finger-like projections found on the surface of the cells of the villi!
– inside each villus is a network of capillaries and lymph vessels

36. Ch 38-2 Absorption in the Small Intestine
absorption – nutrients are absorbed into the cells of the villi lining the small intestine
– carbohydrates and proteins are absorbed into capillaries
– undigested fat and some fatty acids are absorbed into lymph vessels

37. Ch 38-2 Absorption in the Small Intestine

38. Ch 38-2 Absorption in the Small Intestine
when food leaves the small intestine, it is nutrient-free
only water, cellulose, and other undigestible substances remain

39. Ch 38-2 Absorption in the Small Intestine
appendix – small sac-like organ in small intestine that does little to promote digestion
– can be clogged and inflamed - appendicitis

40. Ch 38-2 The Large Intestine
large intestine, or colon – removes water from undigested material that is left
– bacterial colonies produce compounds like vitamin K
concentrated waste material passes through the rectum and is eliminated

41. Ch 38-2 Digestive System Disorders
GERD – gastroesophageal reflux disease
– chronic heartburn in 25-35% of people
– symptoms – heartburn, regurgitation, difficulty swallowing

42. Ch 38-2 Digestive System Disorders
causes – defects in esophageal sphincter;
– slower than normal emptying of the stomach;
– decreased secretion of bicarbonate by the esophagus
– treatments – lifestyle changes; medication to control stomach acid; surgery

43. Ch 38-2 Digestive System Disorders
peptic ulcer – hole in stomach lining produced by the powerful acids released into the stomach
– most are caused by Heliobacter pylori; can be cured with antibiotics

44. Ch 38-2 Digestive System Disorders
diarrhea – irritation or infection that interferes with the removal of water from the large intestines

45. Ch 38-2 Digestive System Disorders
constipation – condition resulting from the removal of too much water from the undigested material in the large intestine

46. Ch 38-2 The Process of Digestion
By the end of this section you should be able to:
Identify the organs of the digestive system
Describe the function of the digestive system

47. Ch 38-2 The Process of Digestion
Identify the organs of the digestive system
Mouth, pharynx, esophagus, stomach, small intestine, and large intestine
Describe the function of the digestive system

48. Ch 38-2 The Process of Digestion
Describe the function of the digestive system
To convert food into simple molecules that can be absorbed and used by the cells of the body

49. Ch 38-3 The Excretory System
By the end of this section you should be able to:
Describe the functions of the kidneys
Explain how blood is filtered

50. Ch 38-3 Functions of the Excretory System
excretion – process by which metabolic wastes are eliminated
– maintains homeostasis in the internal cellular environment
– rids the body of excess salt, CO2 and urea
– urea – toxic compound that is produced when amino acids are used for energy

51. Ch 38-3 The Excretory System
organs of excretion
1) skin – excretes excess water and salt, and a small amount of urea in sweat
2) lungs – excrete carbon dioxide that is produced when ATP is made

52. Ch 38-3 The Excretory System
3) liver – takes up amino acids from proteins that have been broken down
– converts the amino acids into other useful compounds
– produces nitrogen waste in the process, which is potentially poisonous
– the liver converts this nitrogen waste quickly to urea
– urea is removed from the bloodstream by the kidneys

53. Ch 38-3 The Excretory System
4) kidneys – play an important role in maintaining homeostasis by...
1) removing waste products from the blood
2) maintaining blood pH
3) regulating the water content of the blood (i.e., blood volume)

54. Ch 38-3 The Kidneys
anatomy of excretion
 kidneys – located on either side of the spinal column near the lower back

55. Ch 38-3 The Kidneys
ureter – tube that leaves each kidney carrying urine to the urinary bladder
– maintains homeostasis in the internal cellular environment

56. Ch 38-3 The Kidneys
urinary bladder – sac-like organ in which urine is stored before being excreted

57. Ch 38-3 The Kidneys

58. Ch 38-3 The Kidneys
function of kidney
1) blood enters the kidney through the renal artery
2) kidneys remove urea, excess water and other waste products from the blood

59. Ch 38-3 The Kidneys
3) waste products are passed on to the ureter
4) clean, filtered blood leaves the kidney through the renal vein to return to circulation

60. Ch 38-3 The Kidneys
kidney structure – 10 cm long, 6 cm in diameter
 two distinct regions:
1) renal medulla – inner part of the kidney
2) renal cortex – outer part of the kidney

61. Ch 38-3 The Kidneys Kidney Nephron Bowman’s capsule Capillaries Cortex
Medulla
Renal artery
Renal vein
Ureter
To the bladder
Bowman’s capsule
Glomerulus
Capillaries
Collecting duct
To the ureter
Loop of Henle
Artery
Vein

62. Ch 38-3 The Kidneys
nephrons – functional units of the kidney; small independent processing units
– 3 cm long, 0.03 mm wide; 1 million per kidney!
– located in the renal cortex except for the loop of Henle which extends into the renal medulla

63. Ch 38-3 The Kidneys
– each nephron has one arteriole and one venule with a network of capillaries connecting them
– releases fluid to the collecting duct that leads to the ureter

64. Ch 38-3 The Kidneys
▫ flow of blood through nephron – to purify blood
1) blood enters the nephron through the arteriole
2) impurities are filtered out and emptied into the collecting duct
3) purified blood exits the nephron through venule

65. Ch 38-3 The Kidneys
blood purification – requires two processes:
filtration
2) reabsorption

66. Ch 38-3 The Kidneys Reabsorption Filtration
As the filtrate flows through the renal tubule, most of the water and nutrients are reabsorbed into the blood. The concentrated fluid that remains is called urine.
Filtration
Most filtration occurs in the glomerulus. Blood pressure forces water, salt, glucose, amino acids, and urea into Bowman’s capsule. Proteins and blood cells are too large to cross the membrane; they remain in the blood. The fluid that enters the renal tubules is called the filtrate.

67. Ch 38-3 The Kidneys
filtration – the process of passing a liquid or a gas through a filter to remove waste
– takes place in the glomerulus

68. Ch 38-3 The Kidneys
glomerulus – a small network of capillaries encased in the upper end of the nephron by a hollow structure called Bowman's capsule

69. Ch 38-3 The Kidneys
reabsorption – the process in which liquid is taken back into a vessel
– most of the material removed from the blood at Bowman's capsule is returned to the blood

70. Ch 38-3 The Kidneys
Steps to blood purification in the nephron:
1) the blood is under pressure and the walls of the capillaries and Bowman's capsule are permeable
2) fluid flows from the blood into Bowman's capsule; this fluid is called filtrate

71. Ch 38-3 The Kidneys
3) filtrate contains:
water glucose amino acids
some vitamins salts urea
filtrate does not contain: cells plasma proteins platelets (because they are too large to filter out)

72. Ch 38-3 The Kidneys
4) amino acids, fats and glucose are actively pumped out of filtrate and reabsorbed by the capillaries – water follows by osmosis
 5) filtrate (with little water or nutrients left) drains into collecting ducts

73. Ch 38-3 The Kidneys
6) urine – the remaining filtrate; contains urea, excess salt and water
– empties into a collecting duct
– becomes concentrated (excess water is reabsorbed) in the loop of Henle
– loop of Henle - the section of nephron tubule in which water is conserved and volume of urine is minimized

74. Ch 38-3 The Kidneys
7) urine is stored in the urinary bladder until it can be released from the body through a tube called the urethra

75. Ch 38-3 The Kidneys
drugs in urine
– drugs are not usually reabsorbed, they remain in the filtrate and are eliminated in the urine
– this is why the effects of many drugs wear off over time (e.g., antibiotics)

76. Ch 38-3 The Kidneys
– this also means that drugs become more concentrated in the urine, so a urine test is a quick, easy way to test for illegal drugs

77. Ch 38-3 The Kidneys
kidney stones – calcium, magnesium, and uric acid salts can crystallize and form a block in the ureter

78. Ch 38-3 The Kidneys
– cause severe pain
– treated with ultrasound waves to pulverize the stone into small fragments that can be eliminated through the urethra

79. Ch 38-3 The Kidneys
Control of Kidney Function
activities of the kidney are controlled by:
1) the composition of the blood itself
2) regulatory hormones released in response to composition of blood

80. Ch 38-3 The Kidneys example – when you drink a glass of water...
1) the amount of water in your blood increases
2) the rate of water reabsorption decreases
3) less water is returned to the blood
4) excess water is sent to the urinary bladder to be excreted

81. Ch 38-3 The Kidneys
example – when you eat salty food...
1) the amount of salt in your blood increases
2) the kidney allows less salt to be reabsorbed into the blood
3) excess salt is excreted in the urine

82. Ch 38-3 The Kidneys
Homeostasis by Machine
- humans have two kidneys, but can live with one
- if both kidneys are damaged, there are two alternatives:

83. 1) kidney transplant – from a compatible donor
Ch 38-3 The Kidneys
1) kidney transplant – from a compatible donor

84. Ch 38-3 The Kidneys
2) kidney dialysis – if no donor is available
a) blood is removed from the body through a tube, and is sent through a series of tubing that acts like a nephron
b) holes in the tubing allow salt and small molecules to pass through

85. Ch 38-3 The Kidneys
c) waste, urea, and excess salt diffuse out of the blood into a fluid filled chamber
d) purified blood is returned to the body
▫ dialysis is expensive and time- consuming (several hours, 3 times/week)

86. Blood in tubing flows through dialysis fluid
Ch 38-3 The Kidneys
Blood in tubing flows through dialysis fluid
Blood pump
Used dialysis fluid
Air detector
Dialysis machine
Fresh dialysis fluid
Compressed air

87. Ch 38-3 The Excretory System
By the end of this section you should be able to:
Describe the functions of the kidneys
Explain how blood is filtered

88. Ch 38-3 The Excretory System
Describe the functions of the kidneys
Remove waste products from the blood; maintain blood pH; and regulate the water content of the blood (blood volume)
Explain how blood is filtered

89. Ch 38-3 The Excretory System
Explain how blood is filtered