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The Digestive System

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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•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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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

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

• starches found in grains, potatoes, veggies•Broken down to be absorbed into the blood •If not used immediately, sugars can be stored in the liver and muscles.•Not all carbs can be broken down

– Fiber (roughage) keeps your digestive system functioning properly by helping wastes to move through

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Fats (lipids)

•Needed to form cell membranes•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•Made from 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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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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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

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The Esophagus

•Lined with smooth (involuntary) muscle•Contractions, known as peristalsis, squeeze the food through to the stomach•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 • Chemical – stomach glands release a variety of

secretions– Any other chemical digestion is stopped until the

food reaches the small intestine

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Small Intestine (SI)

•Where digestion and then absorption occur– Nutrients are absorbed into the bloodstream

•Water, cellulose and other undigestible substances (like some fats) leave the SI and enter the large intestine

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Accessory Organs

•Pancreas– Produces enzymes that break down carbs,

proteins, lipids and nucleic acids•Liver

– Produces bile which makes fat droplets small so they can be broken down

•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 Large Intestine (LI)

•Also known as the colon•Primary function is to absorb water from undigested materials•The concentrated waste material that remains after the water has been removed passes through the rectum, where it is stored until it is eliminated from the body through the anus.

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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-If the large intestine does not reabsorb enough water, too much 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

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The Excretory System

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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 metabolic wastes as a result of maintaining homeostasis

– Wastes must be removed from the body

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

– The skin excretes excess salts and water

– The lungs excrete carbon dioxide

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

• However, urea is created which must be removed by 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•The kidney removes urea, excess water and other wastes and passes them to the ureter•The clean, filtered blood leaves the kidney and returns to circulation

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Nephron

•The functional unit of the kidney•Each nephron has its own blood supply•Each nephron releases fluid into a collecting duct, which leads to the ureters•The ureters then lead to the bladder, where urine is stored until it is excreted from the body by 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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Disease

•Kidney Stones– 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