Body Systems and Physiology

A body of working systems

The human body is made of organ systems, each a team of organs doing one big job. The digestive system breaks food down so the body can use it. The circulatory system, driven by the heart, carries materials around the body. The breathing system takes in oxygen and removes carbon dioxide. The nervous system coordinates responses, the kidneys clean the blood, and homeostasis keeps conditions steady inside. No system works alone: the blood links them all. This module covers how these systems work and how they cooperate.

Body-systems words

Learn these terms before the systems are described. Each names a job the body carries out.

Match each organ to its job

Arteries against veins

Blood travels away from the heart and back to it in two different kinds of vessel. Telling them apart is a common exam question.

Which vessels carry blood away?

Which blood vessels carry blood away from the heart?

• Arteries
• Veins
• Capillaries
• Alveoli

Systems work together

The best answers show how systems connect. Oxygen breathed into the lungs is picked up by the blood, which the heart pumps to every cell. Food digested in the gut is absorbed into that same blood and carried away. Waste made by the cells is carried back and removed by the kidneys. So when you explain one system, say what it takes in, what it does, and how the blood links it to the rest. That joined-up thinking is what earns the higher marks.

Pick the true heart facts

Select every true statement about the circulatory system.

• The heart pumps blood around the body
• Arteries carry blood away from the heart
• Veins carry blood back to the heart
• The lungs pump blood around the body
• Blood carries no oxygen at all

Order the path of food

Put the parts of the digestive system in the order food passes through them.

• Mouth, where food is chewed
• Oesophagus, the tube to the stomach
• Stomach, where digestion continues
• Small intestine, where food is absorbed
• Large intestine, where water is absorbed

Complete the body-systems facts

Arteries carry blood _____ from the heart. The place where oxygen enters the blood is the _____. The organs that filter the blood and remove waste are the _____. Keeping the conditions inside the body stable is called _____.

How oxygen reaches the blood

Follow a breath of air. It travels down the windpipe and into smaller and smaller tubes until it reaches millions of tiny air sacs deep in the lungs. These sacs have very thin walls and a rich blood supply pressed right against them. Because there is far more oxygen in the fresh air than in the tired blood arriving, oxygen moves across the thin wall into the blood, while the waste gas made by the cells moves the other way and is breathed out. The blood, now refreshed, returns to the heart to be pumped onward. Thin walls, a big surface and a good blood supply are what make the swap fast.

Spot the digestive organs

Tap the TWO organs that are part of the digestive system.

• the stomach
• the small intestine
• the heart
• the lungs

The body-systems run

Answer each one correctly to keep your lives. Choose the organ or system that fits.

Name the system at work

Read each situation and choose the system or organ responsible.

• A meal is broken down into small pieces the body can absorb. Which system is at work?
• A person touches something hot and pulls their hand away at once. Which system coordinated this?
• On a hot day the body sweats and blood vessels in the skin widen to lose heat. What is this an example of?

Build a point about circulation

Choose the word for each gap to complete one clear point about the circulatory system.

Explain how the body works as systems

A friend thinks each organ works on its own. Using what you have learned, explain how the human body works as connected systems.

• Name some of the main organ systems and their jobs
• Explain how the digestive and circulatory systems are linked
• Explain how oxygen gets from the air to the cells
• Explain what homeostasis means and give an example