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The Digestive System

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Do Now

Good Food Sense

Nutrients are molecules that provide the body with energy and materials for growth. Three kinds of nutrients you eat are called fats, proteins, and carbohydrates—terms you may have already heard. Think about what they may mean.

Section 38-1

1. Write a brief description of what you think fats, proteins, and carbohydrates are.

2. Which of these three nutrients do you think should make up the largest part of your diet? Which should make up the smallest part? Arrange the three nutrients in order starting from the one that you should eat the most to the one that you should eat the least.

3. Why might it be unwise to eat too much of the nutrient you listed last?

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Section Outline

38–1 Food and NutritionA. Food and Energy

B. Nutrients

1. Water

2. Carbohydrates

3. Fats

4. Proteins

5. Vitamins

6. Minerals

C. Nutrition and a Balanced Diet

Section 38-1

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Food and Energy

•Cells convert the chemical energy stored in food into ATP

– When food is burned it releases heat energy, which is measured in calories

• A calorie is the amount of heat needed to raise the temperature of 1 gram of water 1 degree Celsius

• Dietary Calories refer to the energy stored in food.

– One Calorie = 1000 calories

•Food also supplies the raw materials used to build and repair body tissues

– These raw materials are used to manufacture new biomolecules

• Food also contains at least 45 substances that your body cannot manufacture

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include

include

such as such as

are made of include

Concept Map

includeare made using

Section 38-1

Nutrients

Carbohydrates Fats MineralsProteins Vitamins

Simple ComplexAmino acids

Calcium Iron

Fatty Acids Glycerol

Sugars Starches Fat-solubleWater-soluble

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Carbohydrates

•Main source of energy for the body– Can be simple

• Mono and disaccharides – found in honey, fruits, sugar cane– Can be complex

• Polysaccharides – starches found in grains, potatoes, veggies•Broken down by the digestive system to be absorbed into the blood and carried throughout the body

– If not used immediately, sugars are converted to glycogen, a complex carb and stored in the liver and muscles.

•Not all carbs can be broken down– Fiber (cellulose) is used to keep your digestive system functioning

properly by helping wastes to move through

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Fats

•Fats (lipids) formed from fatty acids and glycerol– Needed to form cell membranes, myelin sheaths and some

hormones•Extra food is stored as fat to protect body organs and insulate the body•Classified as saturated or unsaturated

– Saturated fats• Solid at room temperature• Main cause of high blood pressure, heart disease, obesity and

diabetes– Unsaturated fats

• Liquid at room temperature• A healthier choice of fat

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Proteins

•Supply raw materials for growth and repair of skin and muscles

•Have regulatory and transport functions

– Ex. insulin, hemoglobin

•Polymers of amino acids

– The body can only synthesize 12 of the 20 amino acids

– The other 8 must be ingested

• Found in meat, fish, milk, eggs

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Figure 38–6 Types of Vitamins

Vitamin

A (retinol)

D (calciferol)

E (tocopherol)

K

B1 (thiamine)

B2 (riboflavin)

Vitamin

A (retinol)

D (calciferol)

E (tocopherol)

K

B1 (thiamine)

B2 (riboflavin)

Sources

Yellow, orange, and dark green vegetables; dairy products

Fish oils, eggs; made by skin when exposed to sunlight; added to dairy products

Green leafy vegetables, seeds, vegetable oils

Green leafy vegetables; made by bacteria that live in human intestine

Whole grains, pork, legumes, milk

Dairy products, meats, vegetables, whole-grain cereal

Sources

Yellow, orange, and dark green vegetables; dairy products

Fish oils, eggs; made by skin when exposed to sunlight; added to dairy products

Green leafy vegetables, seeds, vegetable oils

Green leafy vegetables; made by bacteria that live in human intestine

Whole grains, pork, legumes, milk

Dairy products, meats, vegetables, whole-grain cereal

Function

Important for growth of skin cells; important for night vision

Promotes bone growth; increases calcium and phosphorus absorption

Antioxidant; prevents cellular damage

Needed for normal blood clotting

Normal metabolism of carbohydrates

Normal growth; part of electron transport chain; energy metabolism

Function

Important for growth of skin cells; important for night vision

Promotes bone growth; increases calcium and phosphorus absorption

Antioxidant; prevents cellular damage

Needed for normal blood clotting

Normal metabolism of carbohydrates

Normal growth; part of electron transport chain; energy metabolism

Section 38-1

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Figure 38–6 Types of Vitamins

Vitamin

Niacin

B6 (pyridoxine)

Pantothenic acid

Folic acid

B12 (cyanocobalamin)

Vitamin

Niacin

B6 (pyridoxine)

Pantothenic acid

Folic acid

B12 (cyanocobalamin)

Sources

Liver, milk, whole grains, nuts, meats, legumes

Whole grains, meats, vegetables

Meats, dairy, whole grains

Legumes, nuts, green leafy vegetables, oranges, broccoli, peas, fortified bread and cereal

Meats, eggs, dairy products, enriched cereals

Sources

Liver, milk, whole grains, nuts, meats, legumes

Whole grains, meats, vegetables

Meats, dairy, whole grains

Legumes, nuts, green leafy vegetables, oranges, broccoli, peas, fortified bread and cereal

Meats, eggs, dairy products, enriched cereals

Function

Important in energy metabolism

Important for amino acid metabolism

Needed for energy metabolism

Coenzyme involved in nucleic acid metabolism; prevents neural-tube defects in developing fetuses

Coenzyme in nucleic acid metabolism; maturation of red blood cells

Function

Important in energy metabolism

Important for amino acid metabolism

Needed for energy metabolism

Coenzyme involved in nucleic acid metabolism; prevents neural-tube defects in developing fetuses

Coenzyme in nucleic acid metabolism; maturation of red blood cells

Section 38-1

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Figure 38–6 Types of Vitamins

Vitamin

C (ascorbic acid)

Biotin

Choline

Vitamin

C (ascorbic acid)

Biotin

Choline

Sources

Citrus fruits, tomatoes, red or green peppers, broccoli, cabbage, strawberries

Legumes, vegetables, meat

Egg yolk, liver, grains, legumes

Sources

Citrus fruits, tomatoes, red or green peppers, broccoli, cabbage, strawberries

Legumes, vegetables, meat

Egg yolk, liver, grains, legumes

Function

Maintenance of cartilage and bone; antioxidant; improves iron absorption; important for healthy gums, tissue repair, and wound healing

Coenzyme in synthesis of fat; glycogen formation; amino acid metabolism

Required for phospholipids and neurotransmitters

Function

Maintenance of cartilage and bone; antioxidant; improves iron absorption; important for healthy gums, tissue repair, and wound healing

Coenzyme in synthesis of fat; glycogen formation; amino acid metabolism

Required for phospholipids and neurotransmitters

Section 38-1

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Figure 38–7 Types of Minerals

Section 38-1

Mineral

Calcium

Phosphorus

Potassium

Chlorine

Sodium

Magnesium

Iron

Fluorine

Iodine

Zinc

Sources

Diary products; salmon; sardines;

kale; tofu; collard greens; legumes

Dairy products; meats; poultry; grains

Meats; dairy products; manyfruits and vegetables; grains

Table salt; processed foods

Table salt; processed foods

Whole grains; green leafy vegetables

Meats; eggs; legumes; whole grains; green leafy vegetables; dried fruit

Fluoridated drinking water; tea; seafood

Seafood; dairy products; iodized salt

Meats; seafood; grains

Function

Bone and tooth formation; blood clotting; nerve and muscle function

Bone and tooth formation; acid-base balance

Acid-base balance; body water balance; nerve function

Acid-base balance; formation of gastric juice

Acid-base balance; body water balance; nerve function

Activation of enzymes in protein synthesis

Component of hemoglobin and of electron carriers used in energy metabolism

Maintenance of tooth structure; maintenance of bone structure

Component of thyroid hormones

Component of certain digestive enzymes

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FatsSugars

Fats, Oils, and Sweets (use sparingly)Soft drinks, candy, ice cream, mayonnaise, and other foods in this group have relatively few valuable nutrients.

Milk, Yogurt, and Cheese Group(2-3 Servings)Milk and other dairy products are rich in proteins, carbohydrates, vitamins, and minerals.

Meat, Poultry, Fish, Dry Beans, Eggs, and Nut Group(2-3 servings)These foods are high in protein. They also supply vitamins and minerals.

Vegetable Group(3-5 servings)Vegetables are a low-fat source of carbohydrates,fiber, vitamins, and minerals.

Fruit Group(2-4 servings)Fruits are good sources of carbohydrates, fiber, vitaminsand water.

Bread, Cereal, Riceand Pasta Group(6-11 servings)The foods at the base of the pyramid are rich in complex carbohydrates and also provide proteins, fiber, vitamins, and some minerals.

Figure 38–8 Food Guide Pyramid

Section 38-1

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Section Outline

38–2 The Process of DigestionA. The Mouth

1. Teeth

2. Saliva

B. The Esophagus

C. The Stomach

1. Chemical Digestion

2. Mechanical Digestion

D. The Small Intestine

Accessory Structures of Digestion

E. Absorption in the Small Intestine

F. The Large Intestine

G. Digestive System Disorders

Section 38-2

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Mouth

Salivary glands

Stomach

Pancreas (behind stomach)Large intestine

Small intestine

Rectum

Gallbladder (behind liver)

Liver

Esophagus

Pharynx

Figure 38–10 The Digestive System

Section 38-2

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The Mouth

•Performs mechanical and chemical digestion

– Mechanical – food is changed in size

• Performed by the teeth

– Chemical – food is changed in composition

• Performed by saliva

– Contains amylase (an enzyme that breaks down starch)

– Also helps to moisten food so it can move easier

– Contains lysozyme (an enzyme used to kill bacteria)

•The chewed up clump of food is now considered a bolus

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The Esophagus

•Lined with smooth (involuntary) muscle

•As the bolus passes through, contractions, known as peristalsis, squeeze the food through to the stomach

•The cardiac sphincter (a thick ring of muscle) closes the esophagus after food has entered the stomach to prevent the contents of the stomach from moving back up.

– Is associated with heartburn

• A backflow of stomach acid into your esophagus

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Stomach

•A large muscular sac

– Continues mechanical and chemical digestion

• Mechanical – churning of bolus and stomach acids to form chyme

• Chemical – stomach glands release a variety of secretions

– Hydrochloric acid – activates pepsin

– Pepsin – breaks down proteins

– Any other chemical digestion is stopped until the food reaches the small intestine

– Chyme then leaves the stomach through the pyloric valve and enters the small intestine

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Small Intestine (SI)

•Duodenum (1st part of the SI) where almost all of the digestive enzymes enter from accessory organs

– Shortest part of the SI

•Jejunum and Ileum

– Where absorption of nutrients occurs

– Villi – increase surface area to allow for greater absorption

• Contain capillaries and lymph vessels

– Products of carbs and proteins are absorbed into the capillaries

– Undigested fats and fatty acids are absorbed by the lymph vessels

•Water, cellulose and other undigestible substances leave the SI and enter the large intestine

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Small Intestine Villus

Circular folds

Villi

Epithelial cells

Capillaries

Lacteal

Vein

Artery

Figure 38–14 The Small Intestine

Section 38-2

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Accessory Organs

•Pancreas

– Produces enzymes, that break down carbs, proteins, lipids and nucleic acids

– Also produces sodium bicarbonate to neutralize stomach acids so the enzymes will work

•Liver

– Produces bile, which dissolves and disperses droplets of fats, so that the enzymes can work on the smaller fat molecules

•Gall Bladder

– Stores the bile that is produced by the liver

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Liver

Gallbladder

Duodenum

Bile duct

Pancreas

Pancreatic duct

To rest of small intestine

Figure 38–13 The Liver and the Pancreas

Section 38-2

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The Digestive Enzymes

Site

Mouth

Stomach

Small intestine(from pancreas)

Small intestine

Site

Mouth

Stomach

Small intestine(from pancreas)

Small intestine

EnzymeEnzyme Role in DigestionRole in Digestion

Section 38-2

Salivary amylase

Pepsin

Amylase

Trypsin

Lipase

Maltase, sucrase, lactase

Peptidase

Breaks down starches into disaccharides

Breaks down proteins into large peptides

Continues the breakdown of starch

Continues the breakdown of protein

Breaks down fat

Breaks down remaining disaccharides into monosaccharides

Breaks down dipeptides into amino acids.

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Mouth

Salivary glands

Stomach

Pancreas (behind stomach)Large intestine

Small intestine

Rectum

Gallbladder (behind liver)

Liver

Esophagus

Pharynx

Figure 38–10 The Digestive System

Section 38-2

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Diseases of the Digestive System

Diarrhea-frequent loose or liquid bowel movements-The large intestine is responsible for re-absorption of water. If this does not occur, too much water may be eliminated from the body along with fecal matter. -Upsets the body’s electrolyte balance unless fluids are replaced.

Constipation- stools are usually hard, dry, small in size, and difficult to eliminate - if the large intestine absorbs too much water, the fecal matter becomes very hard and is unable to pass through the colon to the rectum.- treatment can include change in diet, more physical exercise and laxatives

Gastritis - inflammation of the lining of the stomach. -The symptoms include pain or burning sensation in the stomach, especially between meals or at night, upset stomach and blood in stool- The causes are H. pylori infection, non-steroidal anti-inflammatory drugs (NSAIDs), and drinking alcoholic beverages- Treated with antibiotics and medications to reduce stomach acid

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The Excretory System

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Interest Grabber

Your Body’s Filter

Have you ever seen a water-purification system attached to a faucet?This system removes impurities from the water such as arsenic or other chemicals that can be harmful to people. As water passes through the filters contained in the system, the impurities are trapped on the surface of the filters. Eventually, the water that comes out of this purifier is free of the impurities.

Section 38-3

1. Your body has its own system for filtering blood. Why might the blood in your body need to be filtered?

2. What organ(s) do you think filters your blood?

3. How do you think the filtered materials leave your body?

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Section Outline

38–3 The Excretory SystemA. Functions of the Excretory System

B. The Kidneys

1. Kidney Structure

2. Filtration

3. Reabsorption

4. Kidney Stones

C. Control of Kidney Function

D. Homeostasis by Machine

Section 38-3

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Functions of the Excretory System

•Every cell in the body produces metabolic wastes as a result of maintaining homeostasis

– Wastes such as urea, excess salts and carbon dioxide must be removed from the body

•The skin, lungs and liver are three organs that assist in excretion

– The skin excretes excess salts, water and a small amount of urea

– The lungs excrete carbon dioxide

– The liver takes excess amino acids from the blood stream and converts them to useful compounds

• In the process of conversion, poisonous nitrogen compounds are created, which are turned into urea

• Urea is then removed from the bloodstream by the body’s principal organs of excretion – the kidneys

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Kidneys

•The kidneys have many roles

– Remove waste products from the blood

– Maintain blood pH

– Regulate the water content of the blood and therefore blood volume

•As waste-laden blood enters the kidney from the renal artery, it removes urea, excess water and other wastes and passes them to the ureter

•The clean, filtered blood leaves the kidney through the renal vein and returns to circulation

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Kidney Structure

•Two distinct regions

– Renal cortex – outer part

• Contains nephrons – the functional units of the kidney

– Each one is a small, independent unit

– One part of a nephron, the loop of Henle, descend into the inner part of the kidney

– Renal medulla – inner part

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Nephron

•Each nephron has its own blood supply– An arteriole, a venule and a network of capillaries

•Each nephron releases fluid into a collecting duct, which leads to the ureters•Blood purification involves two distinct processes: filtration & reabsorption

– Filtration – takes place in the glomerulus, a small network of capillaries encased in Bowman’s capsule

– Reabsorption – most of the material (water, amino acids, glucose) removed from Bowman’s capsule is taken back into the blood

– The material that remains is urine (urea, salts, water) and is concentrated in the loop of Henle, where water is conserved and the volume of urine is minimized.

– Urine is then stored in the bladder until it is released from the body through the urethra

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Kidney (Cross Section)

Cortex

Medulla

Vein Artery

Kidney

Ureter

Urinary bladder

Urethra

The Urinary System

Section 38-3

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Kidney Nephron

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

Figure 38–17 Structure of the Kidneys

Section 38-3

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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.

Reabsorption

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.

The Nephron

Section 38-3

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Control of Kidney Function

•The activity of the kidneys is controlled by the blood itself.

•Water is absorbed into the blood from the digestive system.

– The concentration of water in the blood increases.

• Without your kidneys, the increase in water conc. would force water into cells and tissues, causing your body to swell

– 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 the excess water is sent to the bladder.

•With an increase in salt, your kidneys return less salt to the blood, and send the excess salt to the bladder.

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Disease

•Kidney Stones

– Substances such as calcium, magnesium or salts in the urine crystallize and form stones

– These stones may block the ureter, causing great pain

– Often treated using ultrasound waves

• The stones gets pulverized into smaller fragments, which are then excreted in the urine.

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Homeostasis by Machine

•Dialysis

– Blood is removed from the body through a tube and pumped through special tubing that acts like nephrons

– Wastes diffuse out of the blood and into a fluid-filled chamber

– The purified blood is then returned to the body

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Vein

Artery

Shunt

Air detector Dialysis machine

Blood pump

Blood in tubing flows through dialysis fluid

Used dialysis fluid

Compressed air

Fresh dialysis

fluid

Figure 38–19 Kidney Dialysis

Section 38-3