P4 Science - Human Body Systems
Created by Miss Clarissa Ng | www.clartutors.com
What is a System?
- A system is made of different parts that work together to perform a specific function.
- All living things are systems as they are made up of different parts that work together for the organism to survive and grow.
Respiratory System
- The respiratory system allows the exchange of gases between the body and the surroundings.
- It takes in oxygen from the surroundings and removes carbon dioxide from the body.
| Component | Function |
|---|---|
| Nose | Entry point for air; filters, warms, and moistens incoming air |
| Windpipe (Trachea) | Tube that carries air to the lungs |
| Lungs | Site of gas exchange — takes in oxygen, releases carbon dioxide |
Circulatory System
- The circulatory system carries (or transports) substances to different parts of the body.
- Blood is pumped around the body by the heart and travels through tiny tubes called blood vessels.
| Component | Function |
|---|---|
| Heart | Pumps blood around the body |
| Blood | Carries useful substances (digested food, oxygen, water) to different parts of the body. Also carries carbon dioxide and waste products away from the body. |
| Blood Vessels | Tubes through which blood travels to all parts of the body |
Skeletal System
- Consists of bones that support the body and give it shape.
- Protects important parts such as the brain, spinal cord, heart, and lungs.
| Function | Details |
|---|---|
| Support & Shape | Bones form the framework of the body, giving it structure and shape. |
| Protection | Skull protects the brain. Ribcage protects the heart and lungs. Spinal column protects the spinal cord. |
Muscular System
- Works with the skeletal system to help different parts of the body move.
- All movement in the body is controlled by muscles.
- Muscles contract or relax for movement to occur.
Digestive System
- Digestion breaks down food into simpler substances so it can be absorbed into the bloodstream and used for energy, growth, and repair.
- Digestion occurs in the mouth, stomach, and small intestine.
| Organ | Function |
|---|---|
| Mouth | Teeth chew and grind food into smaller pieces, increasing the exposed surface area of food to digestive juices, allowing the food to be digested faster. Saliva softens food and contains digestive juice that digests food. |
| Gullet | Pushes food from mouth to stomach. |
| Stomach | Muscular bag that churns food with digestive juices for further digestion. |
| Small Intestine | Digestion ends here. Most digestion takes place in the small intestine. Digested food is absorbed into the bloodstream. |
| Large Intestine | Does not digest any food. Water is absorbed from undigested food. |
Fun fact! The small intestine is called "small" because of its narrow width, but it is actually about 7 meters long — longer than a grown-up and the length of your body multiple times!
Fun fact! The large intestine is about 1.5 meters long — it's shorter but wider than the small intestine.
Working Together
- The human body has different systems. Each system has a different function, but all work together for the body to function.
Example of how systems work together:
| System | Role |
|---|---|
| Digestive System | Breaks down food into simpler substances. |
| Circulatory System | Carries digested food to all parts of the body. |
| Respiratory System | Provides oxygen needed for energy release. |
| Muscular & Skeletal Systems | Use energy from food and oxygen for movement. |