(a) State one function of each of the following structures:
(i) Arteries
(ii) Capillaries
(iii) Veins
(iv) Xylem
(v) Phloem
(b) Describe the changes that take place in the composition of human blood as it passes through the:
(i) Lungs
(ii) Liver
(iii) Kidneys
(iv) Small intestine
(c) List the cellular components of blood.
Explanation
(a)(i) Arteries:
- carry blood away from the heart.
- transport oxygenated blood with the exception of pulmonary artery.
(ii) Capillaries: –
- permit exchange of materials between blood and tissues. .
- links the arteries and veins.
(iii) Veins: –
- carry blood to the heart.
- transport deoxygenated blood except pulmonary vein.
(iv) Xylem: –
- transports water/dissolved mineral salts
- serves as a supporting tissue/strengthening tissue.
(v) Phloem: –
- transports manufactured food/auxins/plants hormones
- performs strengthening supporting function.
(b) Changes in blood composition:(i) Lungs: –
- oxygen is added to the blood.
- carbon dioxide is removed from the blood.
- water is removed from the blood.
(ii) Liver: –
- urea is added to the blood.
- hormonal level is reduced.
- glucose level reduced.
- worn out erythrocytes are removed from the blood.
(iii) Kidneys: Water, urea, some glucose; mineral salts are reduced in the blood.
(iv) Small Intestine: – simple sugars/glucose, amino acids; water; salts and vitamins are added to the blood.
(c) Cellular Components of blood: Red blood cells/erythrocytes; white blood cells/leacocytes; and platelets/ thrombocytes.