Isaac Han (8)Koh Huai Ze (10)Liu Shuyang (14)

Ng Wei Kai (16)

The Digestive System

The breakdown of food into smaller pieces to allow easy absorption into the blood stream Lipids are broken down into fatty acids Proteins are broken down into individual amino acids Carbohydrates are broken down into simple sugars

Digestion – A brief introduction

Foods that we eat must be broken down into smaller pieces before they can be absorbed into the blood and carried to cells throughout the body.

Our body requires these foods to build and nourish cells and to provide energy through respiration.

Digestion – Why it is Important?

The digestive system consists of: The digestive tract

A series of hollow organs joined in a long, twisting tube from the mouth to the anus

Other organs that help the body break down and absorb food

Liver Pancreas

The Digestive System

The Digestive TractConsists of: Mouth Esophagus Stomach Small Intestine Large Intestine (Colon) Rectum Anus

Holloworgans

These hollow organs contain a lining called the mucosa

In the mouth, stomach and small intestine, the mucosa contains tiny glands that produce digestive juices to help digest food

The digestive tract also contains a layer of smooth muscle that helps break down food and move it along the tract

The Digestive Tract

Liver, pancreas and gallbladder

“solid” digestive organs

The liver and pancreas produce digestive juices that reach the intestine through small tubes called ducts

The gallbladder stores the liver’s digestive juices until they are needed in the intestine

Other organs

Digestion involves making food with digestive juices, moving it through the digestive tract, and breaking it down into smaller molecules

It begins in the mouth, and is completed in the small intestine

How is food digested?

Beginning of the digestive system

Chews up food into smaller pieces to aid digestion

Lined with a mucous membrane

Produces saliva which breaks down some starch and fats in the food

Mouth

Esophagus Swallowed food is pushed into

the esophagus Connects the mouth with the

stomach below

Lower esophageal sphincter Ring-like muscle Located at the junction of the

esophagus and stomach In charge of closing the

passage between the two organs

As food approaches it, it relaxes and allows the food to pass through to the stomach

Esophagus

Functions:1. Stores the swallowed

food and liquid – muscle of the upper part of the stomach relaxes to accept large volumes of swallowed material

2. Through a churning action, mixes the food and liquid with digestive juices produced by the stomach to digest them

3. Empty its contents slowly into the small intestine

Carbohydrates spend the least amount of time in the stomach, while proteins stay in the stomach longer, and fats the longest.

Stomach

Much of the digestion and absorption of food takes place here

Primary function: to absorb nutrients and minerals found in food

The mucosa of the small intestine contains many folds called villi

The villi are covered with microscopic projections called microvilli

The structures create a vast surface area for nutrients to be absorbed

Small Intestine

Absorbs water from the remaining indigestible food matter

Connects the small intestine to the rectum

Pass useless waste material from the body

About 1.5m long

Large Intestine

Receives waste matter from the large intestine

When gas or stool comes into the rectum, sensors will send a message to the brain

Act as a temporary storage site for waste matter before it is excreted from the body through the anus

Made up of muscular walls that are able to expand to hold waste material

Rectum

Disposes waste products out of the body

Anus

Produces a digestive juice that contains a wide array of enzymes* to break down the carbohydrate, protein and fat in food

Stores bile from the liver

*enzymes: substances that speed up chemical reactions in the body

Pancreas

Produces a digestive juice called bile

Bile is stored between meals in the gallbladder

At mealtime, it is squeezed out of the gallbladder into the intestine to mix with the fat in food to dissolve the fats and digest the dissolved fats.

Liver