Science Test 12/6/26

Purpose of Digestion

To convert large food molecules into small, simpler molecules that can be absorbed and transported in the blood

The Digestive System

The group of organs that break down food into nutrienrts

Digestive Tract

The connected organs the food passes through as it’s broken down.

Process of Nurient Absorption

Chyme from the stomach enters the small intestine. Villi and microvilli allow chyme to have a larger surface area for nutrient absorption. Nutrients from the chyme are absorbed through the intestinal lining and enter the bloodstream through capillaries in the villi.

How Digestive System and Circulatory System Work Together

After nutrients are absorbed by the small intestine in the digestive system, these nutrients are transported through the bloodstream to the body by the heart pumping it and the arteries carrying it around the body. These two systems work hand-in-hand to ensure our body gets nutrients.

Mechanical Digestion

Breaks food into smaller pieces of the same substance (e.g. teeth chewing a piece of bread)

Chemical Digestion

Breaks down large complex molecules into smaller, simpler ones (e.g. enzymes in saliva breaking down starch and carbohydrate molecules into glucose)

Digestive Organs

Teeth, Salivary Glands, Oesophagus, Stomach, Small Intestine and Large Intestine

Accessory Organs

Pancreas, Liver and Gallbladder

Teeth

Mechanical Digestion

• Cuts, tears and crushes food

• Purpose is to increase surface area of food and make it easier to swallow

Salivary Glands

Chemical Digestion

• Helps to moisten food and make it easier to chew

• Begins carbohydrate digestion (enzyme amylase breaks down bonds in starches and releases sugar)

Oesophagus (Esophagus)

Mechanical Digestion

• Long tube of smooth muscle that connects the pharynx with the stomach

• Peristalsis (contractions of smooth muscles) squeezes food through oesophagus into stomach

Stomach

Mechanical + Chemical Digestion

• A sac of smooth muscle which contracts when empty and expands when full

• Churns and squashes food into a liquid called ‘chyme’

• Secrets gastric juice which contains pepsin (an enzyme) and hydrochloric acid

• Acid kills harmful bacteria and starts breaking down proteins

• Creates and secretes mucus which lubricates and protects stomach wall

Small Intestine

Chemical Digestion

• Most of chemical digestion and 90% of nutrient absorption happens in the small intestine

Large Intestine (Colon)

• Removes water from unndigested food by quickly absorbing it across its wall

• Some celluose (fiber) is digested by bacteria

• Concentrated waste material (faeces/poop) that remains passes through the rectum and expels through the anus

Pancreas

Chemical Digestion

• Makes pancreatic food to digest food

Liver

• Creates bile which helps digest fats

Gallbladder

• Stores and concentrates bile

Digestive Tract Order

1. Mouth

2. Oesophagus

3. Stomach

4. Small Intestine

5. Large Intestine

6. Rectum

7. Anus