The circulatory system in humans

Question 1

The circulatory system consists of the following

Answer 1

• Blood which serves as the medium to transport substances around the body.
• Blood vessels which are tubes through which the blood flows to and from all parts of the body.
• The heart which pumps the blood through the blood vessels.

Question 2

Blood is composed of three types of cells:

Answer 2

• red blood cells
• white blood cells
• platelets.

Question 3

Plasma

Answer 3

Plasma is a yellowish fluid composed of about 90% water and 10% dissolved substances. cells are suspended in a fluid called plasma. plasma makes up about 55%.

Question 4

the 10% dissolved substances of plasma consist of

Answer 4

1. Products of digestion, e.g. glucose, amino acids, vitamins and minerals.
2. Waste products, e.g. carbon dioxide and urea.
3. Hormones, e.g. insulin
4. Plasma proteins, e.g. fibrinogen, and antibodies.

Question 5

Functions of plasma

Answer 5

To transport:

1. Products of digestion from the ileum to the liver and the body cells.
2. Carbon dioxide as the HCO3−
   ion from body cells to the lungs.
3. Urea from the liver to the kidneys.
4. Hormones from the glands that produce them (endocrine glands) to target organs
5. Heat from the liver and muscles to all parts of the body

Question 6

There are three main types of blood vessels:

Answer 6

• arteries
• capillaries
• veins.

Question 7

Journey of the arteries, capillaries and veins.

Answer 7

Arteries carry blood away from the heart. On entering an organ, an artery branches into smaller arteries called arterioles which then branch into a network of capillaries that run throughout the organ. Capillaries then join into small veins called venules which join to form a single vein that leads back from the organ towards the heart.

Question 8

pathway of blood

Answer 8

Blood comes into the right atrium from the body, moves into the right ventricle and is pushed into the pulmonary arteries in the lungs. After picking up oxygen, the blood travels back to the heart through the pulmonary veins into the left atrium, to the left ventricle and out to the body’s tissues through the aorta.