(a) Anaemia is the decrease in the number of RBC than the normal amount and also due to less quantity of haemoglobin than the normal value in blood This is the most common disorder of the blood.

(b) Angina Pectoris Ocurs when there is blockage in coronary artery, thus in sufficient supply of blood reaches to heart muscles. This results in chest pain, fear, anxiety, pale skin, profuse sweating and vomitting. The anginal pain usually starts in the centre of the chest spreads down to the left arm which last for only few second.

(c) Atherosclerosis is the deposition of cholesterol in the inner lining of arteries called atherosclerotic plaque. Sometimes arteries are completely blocked, this result in stroke or heart attack.

(d) Hypertension Ps sometimes also called as arterial hypertension. The blood pressure in the arteries getselevated. It could be primary hypertension which has no obvious medical reason but secondary hypertension are caused by various conditions which affect kidneys, arteries heart or endocrine system.

(e) Heart Failure is the state of heart when it does not pump blood effectively enough to meet the needs of the body.

(f) Erythroblastosis foetalis is a haemolytic disease of new borns which is an allo-immune condition that develops in foetus when IgG molecules produced by mother pass through placenta and attack RBC causing reticulocytosis and anaemia. It develops due to Rh incompatibility between the couples. In a man with $\mathrm{RH}^{+}$blood and women with $\mathrm{Rh}^{-}$, blood the second pregnancy foetus may have this problem due to IgG accumulation in women during first child development and delivery.

The birds and mammals have evolutionary advancement as far as structure of heart is concerned. They need more oxygen to live in terrestrial habitat.

In these animals, the blood received by left and right auricles is oxygenated and deoxygenated respectively. It passes towards the left and right ventricles and thus no oxygenated and deoxygenated blood is mixed. The ventricles pump oxygenated deoxygenated blood without mixing.

Thus, two separate circulatory pathways are found thus this type of blood circulation is called as double circulation, which include systemic and pulmonary circulation.

Hepatic Portal System

There is special vascular connection that exists between the digestive tract and liver in all chordates and is called as hepatic portal system. This system carries blood from intestine to the liver before it is delivered to the systemic circulation.

Significance of hepatic portal system in circulatory system

(i) Blood that comes from alimentary canal contain glucose, amino acids and other nutrients. The liver absorbs excess of fats and glucose to be used at the time of starvation when blood passess through given.

(ii) Harmful nitrogenous wastes like ammonia is converted into urea which is later removed by kidney.

(iii) Liver produces proteins which are transported through blood circulation (e.g., fibrinogen for blood clotting).

Human Lymphatic System comprises of lymph, lymphatic capillaries, lymphatic vessels, lymphatic ducts and lymphatic nodes.

Functional significance of lymphatic system

(i) It removes $\mathrm{CO}_2$ and other metabolic waste from the tissue where blood vessels can not reach.

(ii) Lymphatic blood capillaries of intestine are called lacteals, which help in absorption of fats.

(iii) Lymph filters through out lymph nodes where phagocytotic WBC and macrophages are present in a good number which eats harmful microorganisms and remove foreign particles from the body fluid.

(a) Difference between plasma and serum are as follows

(b) Difference between open and closed circulatory system are as follows

(c) Difference between sino atriol node and artrio-ventricular node are as follow