Thursday, Oct. - The Human Body - The Circulatory and Respiratory System

The Circulatory System

The circulatory system moves blood throughout the body – delivering water and nutrients from the digestive system and oxygen from the respiratory system to all the cells in the body. Blood also removes the cells waste.

The center of the circulatory system is the heart, which pumps blood. The heart is divided into two upper chambers called atria and two lower chambers called ventricles.

Oxygen poor blood from the body enters the right side of the heart. The right atrium and ventricle pump the oxygen poor blood to the lungs. The blood gets oxygen and nutrients and release carbon dioxide and waste in the lungs. Then the blood goes to the left atrium and ventricle, which pumps blood to the rest of the body.

There are three kinds of blood vessels inside the body:

• Arteries carry oxygen-rich blood away from the heart. As blood moves away from the heart, arteries get smaller.
• Capillaries are microscopic vessels that connect arteries and veins
• Veins carry blood back to the heart

The Respiratory System

The digestive system is closely connected to the respiratory system. Oxygen is required for cells to release the energy they get from food.

When you breathe, you pull air into your lungs. The lung is divided into many small air sacs called alveoli, which are surrounded by tiny blood vessels. Oxygen enters the body by diffusing across the alveoli and into the blood vessels. Carbon dioxide leaves the blood stream to be exhaled.