UNIT 4 NATURAL SCIENCE: NUTRITION II

CIRCULATION

Circulation is one of the four processes involved in nutrition, along with digestion, reparation and excretion. Circulation involves transporting nutrients, oxygen and waste products throughout the body.

THE CIRCULATORY SYSTEM

The circulatory system is made up of blood, blood vessels and the heart.

• BLOOD: is a liquid substance in our body that reaches all the body cells. It is made u of:
• PLASMA: thesis a clear fluid which transports nutrients and waste around the body.
• RED BLOOD CELLS: these carry oxygen from lungs to all body cells.
• WHITE BLOOD CELLS: these protect the body from germs and disease.
• PLATELETS: these are fragments of old cells. They help to stop bleeding from wounds.

• BLOOD VESSELS: are tubes which transport blood throughout the body. There are three types:
• ARTERIES: these carry blood away from the heart towards all body tissues.
• VEINS: these carry blood back to the heart from all body tissues.
• CAPILLARIES: these have very thin walls. This allows for nutrients and oxygen to pass into the body cells, and for carbon dioxide and other waste products to leave the cells.

• THE HEART: is a special type of muscle. It acts as a pump to send blood around the body through the blood vessels. The heart has four chambers:
• The right and left atria, where blood enters the heart.
• The right and left ventricles, where blood leaves the heart.

CIRCULATION: PULMONARY CIRCULATION AND SYSTEMIC CIRCUIT

Circulation is the movement of blood through the circulatory system. Blood carries nutrients and oxygen to all parts of the body. It also collects carbon dioxide and other waste products which need to be eliminated.

Blood moves constantly in the circulatory system through two separate circuits: the pulmonary circuit and the systemic circuit.

• PULMONARY CIRCULATION: allows for the exchange of gases in the lungs. This circuit carries blood to the lungs to expel carbon dioxide. It also obtains oxygen in the lungs and brings it back to he heart. Pulmonary circulation works like this:

• SYSTEMIC CIRCULATION: allows for the exchange of nutrients, gases and waste products in the body cells. This circuit carries blood with nutrients and oxygen to all body cells. It also returns blood with carbon dioxide and other waste products back to the heart. Systemic circulation works like this:

THE EXRETION AND THE EXCRETORY SYSTEM

Excretion is the elimination of waste products from the blood. Excretion takes place in the excretory system, the respiratory system and the sweet glands.

• The excretory system is also called the urinary system, because it is the system that produces and expels urine. It consists of the kidneys, the ureters, the bladder and the urethra.
  
  
  In the excretory system, excretion happens when blood reaches the kidneys. The kidneys filter the blood, retain waste products and use them to produce urine. Then, the ureters carry urine from the kidneys to the bladder. Urine is stores in the bladder until it leaves the body through the urethra.
• The respiratory system is involved in both nutrition and excretion. It obtains the oxygen we need to live when we breathe in. When we breathe out, it eliminates carbon dioxide, a waste substance produced in our body.
• Sweat glands are long, coiled tubes that are located inside the skin. Each sweat gland connects to a pore on the surface of the skin. Sweat leaves the skin through the pores. Sweat is formed in the sweat glands. It consists mainly of water, but it also contains mineral salts and waste products.