Introduction

• The digestive system is used for breaking down food into nutrients which then pass into the circulatory system and are taken to where they are needed in the body.

Components

• Esophagus• Stomach• Small Intestine• Large Intestine• Gall bladder• Liver• Pancreas

• There are four stages to food processing:

1.Ingestion: taking in food

2.Digestion: breaking down food into nutrients

3.Absorption: taking in nutrients by cells

4.Egestion: removing any leftover wastes

       

1. Digestion:

The process by which

your body breaks down

food into small nutrient

molecules.

(mechanical and chemical)

I. The Digestive Process Begins

The process by which nutrient molecules

pass through the wall of your digestive

system into your blood.

2. Absorption:

3. Elimination:

Materials that are not absorbed are eliminated from the body as waste (ie. Fiber)

Diagram of Digestive System

Mouth• Chemical and

mechanical digestion.

• Food is chewed (masticated) mechanically.

• A bolus (lump) is formed with saliva and the tongue.

B. Mouth

1. Saliva: Fluid released when your mouth waters and plays an important part in both mechanical and chemical digestion.

Types of Digestion

2. Mechanical Digestion- Teeth begin digestion by cutting, tearing, and grinding food

mouthbreak up fooddigest starchkill germsmoisten food

C. Esophagus- Total Time 10 seconds.

1.           1. Epiglottis:

Flap of tissue that seals off your windpipe preventing food from entering.

2. Esophagus:

Food enters a muscular tube that connects the mouth to the stomach.

3. Mucus:

Thick, slippery substance that lines the esophagus in order to make food easier to swallow and move along

• You have a trap door called the epiglottis to cover your windpipe when you swallow.

• series of involuntary wave-like muscle contractions which move food along the digestive tract

Peristalsis

Stomach• Food is temporarily

stored here.• Gastric juices are

secreted.• Has layers of

muscle that line the inside.

• Mechanically and chemically breaks down food.

1. Mechanical Digestion: Three strong layers of smooth muscle contract to produce a churning motion. (similar to a washing machine)

2. Chemical Digestion: Churning food makes contact with digestive juices.

a. Enzyme Pepsin- Works best in an acid environment.

    b. Hydrochloric Acid (HCl).-Kills many bacteria that you swallow with food, mucus protects stomach lining from this acid.

c. Food remains in the stomach until the entire solid has been broken down.

• Your stomach mashes your food the way a baker kneads dough for bread.

• Your stomach stretches when you eat like a balloon being filled with air

stomachkills germs break up fooddigest proteinsstore food

sphincter

sphincter

mouthbreak up fooddigest starchkill germsmoisten food

Small Intestine• Most chemical

digestion takes place here.

• Simple sugars and proteins are absorbed into the inner lining.

• Fatty acids and glycerol go to lymphatic system.

• Lined with villi, which increase surface area for absorption, one cell thick.

 3. Absorption in the Small Intestine

a. Villi:

Fingerlike structures increase the surface area of the small intestines and allow nutrient molecules to pass into the blood

Small Intestine

• Tube that is 20 feet long.

• Continues to digest food

• Food stays in your small intestine for 4 to 8 hours

Large Intestine• Solid materials pass

through the large intestine.

• These are undigestible solids (fibers).

• Water is absorbed.• Vitamins K and B are

reabsorbed with the water.

• Rectum- solid wastes exit the body.

Large intestines (colon)

• Function– re-absorb water

• use ~9 liters of water every day in digestive juices

• > 90% of water reabsorbed– not enough water absorbed

» diarrhea

– too much water absorbed

» constipation

B. The Large Intestine -The last section of the digestive system that contain bacteria that feed on material and make vitamins (1.5 meters long)

-The role is absorb water into the bloodstream and get remaining material ready for elimination.

Large Intestine• Tube that is 5 feet long

• Gets waste from small intestine

• Waste stays for 10 to 12 hours

Rectum

• Last section of colon (large intestines)– eliminate feces

• undigested materials– extracellular waste

» mainly cellulose from plants

» roughage or fiber – masses of bacteria

Accessory Organs• Pancreas

• Gall Bladder

• Spleen

Pancreas

• An organ which secretes both digestive enzymes (exocrine) and hormones (endocrine)

• ** Pancreatic juice digests all major nutrient types.

• Nearly all digestion occurs in the small intestine & all digestion is completed in the SI.

Gall bladder

• Pouch structure located near the liver which concentrates and stores bile

• Bile duct – a long tube that carries BILE. The top half of the common bile duct is associated with the liver, while the bottom half of the common bile duct is associated with the pancreas, through which it passes on its way to the intestine.

BILE

• Bile emulsifies lipids (physically breaks apart FATS)

• Bile is a bitter, greenish-yellow alkaline fluid, stored in the gallbladder between meals and upon eating is discharged into the duodenum where it aids the process of digestion.

pancreasproduces enzymes to digest proteins & starch

stomachkills germs break up fooddigest proteinsstore food

mouthbreak up fooddigest starchkill germsmoisten food

liverproduces bile

- stored in gall bladderbreak up fats

Healthy Habits• Eat foods that

are high in fiber like fruits and vegetables

• Drink plenty of water

• Chew your food completely before you swallow

Avoid foods high in fat

Interesting Facts• Food is in your digestive system

for about 24 hours