AQA GCSE FOUNDATION Biology: Digestive System Overview

AQA GCSE Foundation Biology: Digestive System Overview

Introduction

The digestive system is a complex and vital part of our body responsible for breaking down food into smaller molecules that can be absorbed and used for energy, growth, and repair. This process is called digestion.

Organs of the Digestive System

The digestive system comprises several organs working together to achieve digestion. Here is an overview of their structures and functions:

1. Mouth:

• Structure: The mouth contains teeth, tongue, and salivary glands.
• Function:
  • Teeth: Used for chewing and grinding food into smaller pieces.
  • Tongue: Helps mix food with saliva and push it towards the back of the mouth.
  • Salivary Glands: Produce saliva, which contains enzymes like amylase, that begin the breakdown of starch into simpler sugars.

2. Oesophagus:

• Structure: A muscular tube connecting the mouth to the stomach.
• Function: Peristalsis, muscular contractions, move food down the oesophagus to the stomach.

3. Stomach:

• Structure: A muscular bag with a thick lining that secretes digestive juices.
• Function:
  • Churns and mixes food with gastric juices.
  • Gastric juices contain hydrochloric acid to kill bacteria and pepsin, an enzyme that breaks down proteins.
  • The stomach also secretes mucus to protect its lining from the acidic juices.

4. Small Intestine:

• Structure: A long, coiled tube made up of three sections: the duodenum, the jejunum, and the ileum.
• Function:
  • The majority of digestion and absorption takes place here.
  • The duodenum receives digestive juices from the pancreas and liver.
  • The pancreas secretes pancreatic juice containing enzymes like amylase, lipase, and protease, which break down carbohydrates, fats, and proteins, respectively.
  • The liver produces bile, stored in the gallbladder, which emulsifies fats, making them easier to digest.
  • Villi and microvilli on the lining of the small intestine increase the surface area for absorption of nutrients.

5. Large Intestine:

• Structure: A wider, shorter tube consisting of the colon and rectum.
• Function:
  • Absorbs water and some minerals from undigested food.
  • Forms faeces, which is stored in the rectum before being eliminated from the body.

6. Pancreas:

• Structure: A gland located near the small intestine.
• Function:
  • Secretes pancreatic juice into the duodenum, containing digestive enzymes.
  • Produces insulin and glucagon, hormones that regulate blood sugar levels.

7. Liver:

• Structure: The largest gland in the body.
• Function:
  • Produces bile, which aids in fat digestion.
  • Detoxifies the blood, removing harmful substances.
  • Stores glucose as glycogen, regulating blood sugar levels.
  • Produces proteins essential for blood clotting and other functions.

8. Gallbladder:

• Structure: A small sac attached to the liver.
• Function: Stores and concentrates bile produced by the liver.

Summary

The digestive system is a complex and essential system that allows us to break down food, absorb nutrients, and eliminate waste. Each organ plays a crucial role in this process, and understanding their functions is vital for maintaining a healthy digestive system.