Digestive System

Chapter 38

The Food Machine1. How many eggs & cheese does a person consume in

a lifetime?2. What starts the process of digestion?3. What is the esophagus?4. What is the name of the contractions that allow for

passage of food through the system?5. How much saliva is produced every day?6. What is the size of the stomach?7. What do the cells in the stomach release?8. What is pepsin?9. What is energy measured in?10. What is the job of villi?

Movie quiz 5-23-071. What starts the process of digestion?

2. What is the esophagus?

3. What is the name of the contractions that allow for passage of food through the system?

4. What is the size of the stomach?

5. What do the cells in the stomach release?

6. What is pepsin?

7. What is energy measured in?

Food & Nutrition

• Food is our “fuel”

• Our digestive system breaks down food into molecules that we can use for energy

Nutrients• Substances in food that supply energy &

raw materials

• Water

• Carbohydrates

• Fats

• Proteins

• Vitamins

• Minerals

Water• Most important nutrient

• Can not live without it

• Makes up most of all body fluids (blood)

• Humans need at least 1 liter a day

• If not – dehydration occurs

• This leads to problems in the circulatory, respiratory, & nervous system

• Drinking water is the #1 way to keep your body healthy

Carbohydrates (CHO)

• Sugars – monosaccharides/disaccharides

- fruit, honey, sweets

• Starches – polysaccharides (complex)

- grains, potatoes, veggies

• Each type is broken down into GLUCOSE.

• Used for immediate source of energy

• If not used – stored in liver & skeletal muscle as GLYCOGEN

Cellulose - Fiber

• Type of CHO that body can not break down

• Main job – to keep food & wastes moving through body

• Sources – whole grain breads

bran

many fruits

veggies

Fats (lipids)• Made of fatty acids & glycerol

• “Essential Fatty Acids”

- produces cell membranes, myelin sheaths, & certain hormones

- help absorb fat soluble vitamins

• We need some fat to protect organs & insulate the body

• When you eat more food than is needed – body stores extra energy as fat

Types of Fats

• Saturated – solid at room temperature

- butter & other animal fat (lard)

• Unsaturated – liquid at room temp.

- oils

• Eating too much of either one can lead to heart disease, high blood pressure, obesity, diabetes & even death

Proteins

• Have many jobs in our body

• Supply materials for growth & repair of skin & muscles

• Regulate activities

- insulin – regulates sugar levels

• Help transport materials

- hemoglobin – helps transport oxygen in blood

Amino Acids

• 20 amino acids make up all proteins in human body

• 12 of the 20 – body makes naturally

• Other 8 are called “essential amino acids”

• These must be obtained from food

• Meat, eggs, & milk generally contain all 8

• Vegetarians must eat a combo of rice & beans to get all 8

Vitamins

• If food is fuel for our body, then vitamins are the ignition

• Organic molecules that help regulate body processes

• Work with enzymes (speed up reactions)• Most obtained by food• Bacteria in intestines make Vitamin K• Skin exposed to sun makes Vitamin D• Lack of vitamins can have serious even

fatal consequences

Types of Vitamins• Fat soluble – A, D, E, K

- stored in fat – can be used in future

• Water soluble - B & C

- cannot be stored in body

- need to eat food to get vitamins

• Taking large doses of supplements does not benefit the body – causes real harm

• Excessive amounts of vitamin A, D, E, & K can be toxic

Minerals

• Inorganic nutrients the body needs• Calcium, iron, magnesium, potassium• Body can not break them down• Loses them through sweat, urine, & other

wastes• Need to eat plants & meat to get the

required amounts• Sometimes need to take supplements if

you do not eat the right foods

include

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are made of include

Nutrient 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

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.

Section 38-1Food Pyramid

Mouth• Contains digestive

enzymes that begin the breakdown of carbohydrates (CHO)

• Where teeth are located• Where saliva produced• Mechanical digestion

- the physical breakdown of large pieces of food into smaller pieces

Teeth• Tear, crush & chew food• Anchored into bones

of the jaw• Covered by enamel• Mechanical digestion• 4 types

1. molars

2. bicuspids

3. cuspids

4. incisors

Saliva• Secreted by Salivary Glands

• Moistens food – makes it easier to chew

• Mechanical digestion

• Releases 2 enzymes:

1. Amylase – breaks down starches & releases sugars

2. Lysozyme – fights infection by digesting cell walls of bacteria that enters the mouth

Esophagus• Food tube• Connects mouth to stomach• Once food is chewed, it is

called a BOLUS• Contractions called

PERISTALSIS squeeze food through the esophagus into the stomach

• CARDIAC SPHINTER – ring of muscle that closes the esophagus after the food passes into stomach – to prevent food from coming back up

Stomach• Large muscular sac – surrounded by 4

layers of muscle• Mechanical digestion:

- alternating contractions mix & churn food which is known as CHYME

• Chemical digestion:- releases HCl (hydrochloric acid) - this activates PEPSIN – breaks down proteins- CHO digestion stops in stomach

because it is too acidic- starts again in the small

intestine- releases mucus – to protect lining of stomach

Small Intestine• PYLORIC VALVE –

separates stomach & small intestine

- open 1 or 2 hours after food arrives in stomach

• DUODENUM – beginning of s. intestine

- most chemical & mechanical digestion occurs here

- digestive enzymes from the pancreas & liver

Pancreas• Large Gland• 3 major functions:

1. produce hormones that regulate blood sugar

2. produce enzymes that breakdown carbohydrates, lipids, proteins & nucleic acids

3. produces SODIUM BICARBONATE - neutralizes stomach acid

Liver• Located just above

& to the right of stomach

• Produces BILE – acts like a detergent

- dissolves fat

- stored in GALLBLADDER

Large Intestine• Primary function –

remove water from undigested material

• Colonies of bacteria are found here – produce Vitamin K

• Once water is removed – waste moves through colon to the rectum and is excreted from the body