Chapter 38 lecture on the digestive & excretory systems

2. 38–1 Food and Nutrition

3. Food and Energy
You eat food to obtain energy and raw materials.
The energy in food is measured in Calories
(capital C). One Calorie is equal to 1000 calories.
One calorie is the amount of heat
needed to raise the temperature of one
gram of water by one degree Celsius.

4. Food and Energy
Caloric needs vary for each person.
An average-sized female teenager needs
about 2200 Calories a day.
An average-sized male teenager needs
about 2800 Calories a day.
If you exercise regularly, your energy needs
may be higher.

5. Nutrients
Nutrients
Nutrients are substances in food
that supply the energy and raw
materials your body uses for
growth, repair, and maintenance.

6. Nutrients
The nutrients that the body needs are:
•water
•carbohydrates
•fats
•proteins
•vitamins
•minerals

7. Nutrients
Every cell in the human body needs
water because many of the body's
processes take place in water.

8. Nutrients
Water makes up blood, lymph, and
other bodily fluids.
Water is lost during sweating, when it
evaporates to cool the body.
Water vapor is also lost when you exhale
and in urine.
Humans need to drink at least one liter of water
each day.

9. Nutrients
Carbohydrates
Carbohydrates are the main source of
energy for the body.
There are two types of carbohydrates:
•simple
•complex

10. Nutrients
Simple carbohydrates are found in fruits,
honey, and sugar cane.
Simple carbohydrates do not need to be
digested or broken down.

11. Nutrients
Complex carbohydrates, or starches, are
found in grains, potatoes, and vegetables.
Complex carbohydrates need to be broken
down before they can be used by the body.
Many foods contain the complex
carbohydrate cellulose, or fiber.

12. Nutrients
Fiber is needed in your diet.
Bulk supplied by fiber helps muscles keep
food and wastes moving through your
digestive and excretory systems.
Whole-grain breads and many fruits and
vegetables have fiber.

13. Nutrients
Fats
Fats, or lipids, are an important part of a
healthy diet.
Fats are formed from fatty acids and
glycerol.

14. Nutrients
Fats are needed:
• to produce cell membranes, myelin
sheaths around neurons, and certain
hormones.
• to help the body absorb fat-soluble
vitamins.
• to protect body organs and insulate the
body.

15. Nutrients
Fats are classified as saturated or
unsaturated.
When there are only single bonds between
carbon atoms in the fatty acids, the fat is
saturated.
Most saturated fats are solids at room
temperature—including butter and other
animal fats.

16. Nutrients
Unsaturated fats have at least one double
bond in a fatty acid chain.
Unsaturated fats are usually liquids at room
temperature.
Because many vegetable oils contain more
than one double bond, they are called
polyunsaturated.

17. Nutrients
Proteins
Proteins supply raw materials for growth
and repair of structures such as skin and
muscle.
They have regulatory and transport
functions.

18. Nutrients
Proteins are polymers of amino acids.
The body can synthesize only 12 of the 20
amino acids used to make proteins.
The other 8 amino acids are called essential
amino acids; they must come from food.

19. Nutrients
Animal products, including meat, fish, eggs,
and milk, contain all 8 essential amino
acids.
Foods derived from plants, such as grains
and beans, do not.
Therefore, people who don’t eat animal
products must eat a combination of plant
foods to obtain all of the essential amino
acids.

20. Nutrients
Vitamins
Vitamins are organic molecules that help
regulate body processes, often working
with enzymes.
Most vitamins must be obtained from food.
A diet lacking certain vitamins can have
serious, even fatal, consequences.

21. Nutrients
There are two types of vitamins:
• fat-soluble
• water-soluble
The fat-soluble vitamins A, D, E, and K can
be stored in the fatty tissues of the body.
The body can build up stores of these
vitamins for future use.

22. Nutrients
Fat-Soluble Vitamins

23. Nutrients
The water-soluble vitamins dissolve in
water and cannot be stored in the body.
Eating a diet containing a
variety of foods will supply
the daily vitamin needs of
nearly everyone.

24. Nutrients
Water-Soluble Vitamins

25. Nutrients
Water-Soluble Vitamins

26. Nutrients
Minerals
Inorganic nutrients that the body needs,
usually in small amounts, are called
minerals.
By eating a variety of foods, you can meet
your daily requirement of minerals.

27. Nutrients

28. Nutrients

29. Nutrition and a Balanced Diet
The new food pyramid classifies foods
into six categories:
•grains
•vegetables
•fruits
•milk
•meat and beans
•fats, sugars, and salts

30. Nutrition and a Balanced Diet

31. The figure climbing up the side of the
pyramid represents exercise.
You should get at least 30 minutes of
exercise each day.
Nutrition and a Balanced Diet

32. A food label provides information about
nutrition.
Daily values are based on a 2000-Calorie
diet, and nutrient needs are affected by age,
gender, and lifestyle.
Nutrition and a Balanced Diet

33. When choosing foods, you should compare
similar foods on the basis of their
proportion of nutrients to Calories.
When you choose a food, it should be high
in nutrition and low in Calories.
Nutrition and a Balanced Diet

34. 38–2 The Process of Digestion

35. Digestion
The digestive system includes the mouth,
pharynx, esophagus, stomach, small
intestine, and large intestine.
Other structures add secretions to the
digestive system, and aid in digestion.
These include the salivary glands, pancreas
and liver.

36. Mouth
Salivary glands
Stomach
Pancreas
Large intestine
Small intestine
Pharynx
Esophagus
Liver
Gallbladder
Rectum
• The Digestive System

38. The function of the digestive system is to
help convert foods into simpler molecules
that can be absorbed and used by the cells
of the body.

39. The Mouth
The Mouth
•Chewing begins mechanical
digestion, which is the physical
breakdown of large pieces of
food into smaller pieces.

40. The Mouth
• The teeth cut, tear, and crush food into
small fragments.
• As the teeth cut and grind the food,
salivary glands secrete saliva, which
moistens food and makes it easier to
chew.
• Saliva helps ease the passage of food
through the digestive system.

41. The Mouth
Saliva contains amylase, an enzyme
that breaks the chemical bonds in
starches and releases sugars. This
begins chemical digestion.
Saliva also contains lysozyme, an enzyme that
fights infection.

42. The Esophagus
From the pharynx , the chewed food
passes through the esophagus, or
food tube, into the stomach.
Contractions of smooth muscle,
known as peristalsis, squeeze
the food through the esophagus
into the stomach.

43. Peristalsis
in the
esophagus
Esophagus
Bolus
Stomach
Muscles
contracted

44. The Esophagus
The cardiac sphincter closes the
esophagus after food has passed into the
stomach.

45. The Stomach
The Stomach
• Food from the esophagus empties into
the stomach.
• The stomach continues mechanical and
chemical digestion.
• Alternating contractions of three
smooth muscle layers churn food.

46. The Stomach
Chemical Digestion
•Stomach lining has millions of gastric glands that
release substances into the stomach.
Some glands produce mucus, which lubricates
and protects the stomach wall.
Other glands produce hydrochloric acid,
which makes the stomach very acidic.
Other glands produce pepsin, an enzyme that
digests protein.

47. The Stomach
Pepsin and hydrochloric acid begin protein
digestion.
Pepsin breaks proteins into smaller
polypeptide fragments.
Other enzymes are denatured by stomach
acid.

49. The Stomach
Mechanical Digestion
•The stomach contracts to churn
fluids and food, gradually
producing a mixture known as
chyme.
• After 1–2 hours, the pyloric valve between
the stomach and small intestine opens
and chyme flows into the small intestine.

50. The Small Intestine
The Small Intestine
• As chyme is pushed through the pyloric
valve, it enters the duodenum.
• The duodenum is the first of three parts
of the small intestine, and is where most
digestive enzymes enter the intestine.

51. The Small Intestine
Most chemical digestion and
absorption of food occurs in the
small intestine.

52. The Small Intestine
Accessory Structures of Digestion
Liver
Gallbladder
Duodenum
Bile duct
Pancreas
Pancreatic
duct
To rest of small
intestine

53. The Small Intestine
Accessory Structures of Digestion
• Just behind the stomach is the
pancreas.

54. During digestion, the pancreas:
•produces enzymes that break
down carbohydrates, proteins,
lipids, and nucleic acids.
•produces sodium bicarbonate, a
base that neutralizes stomach
acid so that these enzymes can be
effective.

55. The pancreas also secretes
insulin, a hormone that regulates
the amount of sugar in the blood.

56. The Small Intestine
Assisting the pancreas is the liver,
which produces bile.
Bile dissolves and disperses
droplets of fat in fatty foods. This
enables enzymes to break down smaller fat
molecules.
Bile is stored in the gallbladder.

57. Absorption in the Small Intestine
• The small intestine is adapted for
the absorption of nutrients.
•The folded surfaces of the
small intestine are covered
with fingerlike projections
called villi.

58. Small intestine
Circular folds
Villi
Villus
Epithelial
cells
Capillaries
Lymph vessel
Vein
Artery
Absorption in the Small Intestine

59. Cell surfaces of villi have more projections
called microvilli.
These provide an enormous surface area
for the absorption of nutrient molecules.
Slow, wavelike contractions of smooth
muscles move the chyme along this
surface.
Absorption in the Small Intestine

60. Nutrient molecules are absorbed into the
cells lining the small intestine.
Most products of carbohydrate and protein
digestion are absorbed into the capillaries
in the villi.
Molecules of undigested fat are absorbed
by lymph vessels.
Absorption in the Small Intestine

61. The Large Intestine
• When the chyme leaves the small intestine, it enters the
large intestine, or colon.
•The large intestine removes water from the
chyme.
• Water is absorbed quickly, leaving undigested materials
behind.
•Concentrated waste material passes through
the rectum and is eliminated from the body.

62. Digestive System Disorders
•Stomach acids sometimes damage
the organ’s own lining, producing
a hole in the stomach wall known
as a peptic ulcer. Most peptic ulcers
are caused by the bacterium H. pylori.
• Other digestive disorders include diarrhea
and constipation.

63. 38–3 The Excretory System

64. Functions of the Excretory System
•maintain homeostasis
•remove metabolic wastes
through excretion.

65. The skin excretes excess water
and salts in the form of sweat.
The lungs excrete carbon dioxide.
The kidneys also play a major role in
excretion.

66. The kidneys (main excretory
organs):
•remove waste products from the
blood.
•maintain blood pH.
•regulate the water content of the
blood and, therefore, blood
volume.

67. The Kidneys
• The kidneys are located on either side of
the spinal column near the lower back.
• A tube, called the ureter, leaves each
kidney, carrying urine to the urinary
bladder.
• The urinary bladder is a saclike organ
where urine is stored before being
excreted.

68. Structure of the Kidneys
Kidney Nephron

70. The Kidneys
Blood enters the kidney through the renal artery.
The kidney removes urea, excess water, and
other waste products and passes them to the
ureter.
The clean, filtered blood
leaves the kidney through
the renal vein and returns
to circulation.

71. The Kidneys
Kidney Structure
• A kidney has two distinct regions:
The inner part is called the renal
medulla.
The outer part is called the renal
cortex.

72. Cortex
Medulla
The Kidneys
Renal
artery
Renal vein
Ureter
To the bladder

73. The Kidneys
The functional units of the kidney
are called nephrons.
Nephrons are located in the renal cortex,
except for their loops of Henle, which
descend into the renal medulla.

74. Artery
Vein
Loop of Henle
Bowman’s capsule
Glomerulus
The Kidneys
Collecting
duct
Capillaries
To the ureter

75. The Kidneys
Vein
Artery
Capillaries
To the ureter
Collecting
duct
Each nephron has
its own blood
supply:
• an arteriole
• a venule
• a network of
capillaries
connecting them

76. The Kidneys
Vein
Artery
Capillaries
To the ureter
Collecting
duct
Each nephron
releases fluids to a
collecting duct,
which leads to the
ureter.

77. The Kidneys
As blood enters a nephron through the
arteriole, impurities are filtered out and
emptied into the collecting duct.
The purified blood exits the nephron
through the venule.

78. The Kidneys
The mechanism of blood purification
involves two distinct processes: filtration
and reabsorption.

79. The Kidneys
Filtration
• Passing a liquid or gas through a filter to
remove wastes is called filtration.
•Filtration of blood takes place in
the glomerulus, a small network of
capillaries encased in the top of the
nephron by a hollow, cup-shaped
structure called Bowman's capsule.

80. The Kidneys
Fluid from the blood flows into Bowman’s
capsule.
The materials filtered from the blood
include water, urea, glucose, salts,
amino acids, and some vitamins.
Plasma proteins, cells, and platelets remain
in the blood because they are too large to
pass through the capillary walls.

81. The Kidneys
Reabsorption
• Most of the material removed from the
blood at Bowman's capsule makes its
way back into the blood.
• The process in which liquid is taken
back into a vessel is called
reabsorption.

82. The Kidneys
Almost 99% of the water that enters
Bowman’s capsule is reabsorbed into the
blood.
Most water and nutrients are
reabsorbed into the blood.

83. The Kidneys
Remaining material, called urine, is emptied
into a collecting duct.
Urine is primarily concentrated in the loop
of Henle.
The loop of Henle is a section of the
nephron tubule in which water is conserved
and the volume of urine minimized.

84. The Kidneys
As the kidney works, purified blood is
returned to circulation while urine is
collected in the urinary bladder.
Urine is stored here until it is released
from the body through a tube
called the urethra.

85. Control of Kidney Function
• The activity of the kidneys is mostly
controlled by the composition of the
blood.
• In addition, regulatory hormones are
released in response to the composition
of blood.

86. Control of Kidney Function
When you drink a liquid, it is absorbed into the
blood through the digestive system.
As a result, the concentration of water in the
blood increases.
As the amount of water in the blood increases,
the rate of water reabsorption in the kidneys
decreases.
Less water is returned to the blood, and excess
water is sent to the urinary bladder to be excreted
as urine.

87. When the kidneys detect an increase in salt,
they respond by returning less salt to the
blood by reabsorption.
The excess salt the kidneys retain is
excreted in urine, thus maintaining the
composition of the blood.
Control of Kidney Function

88. Kidney Disorders
Kidney Disorders
•Humans have two kidneys, but can
survive with only one.
•If both kidneys are damaged by disease
or injury, there are two options:
a kidney transplant
kidney dialysis

89. Kidney dialysis works as follows:
• Blood is removed by a tube and pumped
through special tubing that acts like
nephrons.
•Tiny pores in dialysis tubing allow
salts and small molecules like urea
to pass through.
• Wastes diffuse out of the blood into the fluid-
filled chamber, allowing purified blood to be
returned to the body.

90. Kidney Disorders
Kidney Dialysis
Air detector Dialysis
machine
Fresh
dialysis
fluid
Compressed
air
Vein
Artery
Shunt
Blood pump
Blood in tubing flows
through dialysis fluid
Used dialysis fluid

91. Esophagus
Stomach
Liver
Pancreas
Small intestine
Large intestine

92. 38–1
Which nutrient is found in fruits, sugars, and
whole-grain breads?
a. protein
b. fat
c. carbohydrates
d. vitamins

93. 38–1
Organic molecules that help regulate body
processes and often work with enzymes are
a. fats.
b. minerals.
c. vitamins.
d. amino acids.

94. 38–1
Which two vitamins can be made by the body?
a. vitamins a and B
b. vitamins C and D
c. vitamins A and K
d. vitamins D and K

95. 38–1
The most important nutrient is
a. fat
b. water
c. vitamins
d. protein.

96. 38–1
The foods that should make up the largest part of
your diet are
a. fats and sweets.
b. meat, poultry, and fish
c. milk, yogurt, and cheese.
d. breads, cereals, rice, and pasta.
FRESH VEGETABLES & FRUITS !!!!!

97. 38–2
Food is moved through the esophagus into the
stomach by
a. air pressure.
b. muscle contractions.
c. gravity.
d. swallowing.

98. 38–2
A gland that has both endocrine and exocrine
functions is the
a. liver.
b. spleen.
c. pancreas.
d. gallbladder.

99. 38–2
The enzyme in saliva that begins the digestion of
starch is
a. amylase.
b. pepsin.
c. lysozyme.
d. peptidase.

100. 38–2
Stomach muscles contract to churn and mix
stomach fluids and food, producing a mixture
known as
a. chyme.
b. amylase.
c. bile.
d. acid.

101. 38–2
Absorption of vitamins, minerals, and digested
food molecules takes place in the
a. stomach.
b. small intestine.
c. large intestine.
d. duodenum.

102. 38–3
A dialysis machine performs the function of which
structure in the excretory system?
a. nephron
b. ureter
c. urethra
d. glomerulus

103. 38–3
In the human body, the kidneys play an important
role in
a. producing digestive enzymes.
b. circulating the blood.
c. destroying old red blood cells.
d. maintaining homeostasis.

104. 38–3
In the nephron, most filtration occurs in the
a. renal tubule.
b. capillaries.
c. glomerulus.
d. loop of Henle.

105. 38–3
Urine leaves the body through the
a. loop of Henle.
b. glomerulus.
c. urethra.
d. bladder.

106. 38–3
Materials filtered out of the blood include all of
the following EXCEPT:
a. water.
b. urea.
c. amino acids.
d. plasma proteins.