Biology [2 Mark Question Answer]

Blood Vessels entering the heart: The right atrium receives two large vessels :
(i) Anterior vena cava
(ii) Posterior vena cava

Blood Vessels leaving the heart: Arising from the ventricle are two large blood vessels :
(i) The pulmonary artery
(ii) The aorta
The coronary arteries arising from the base of the aorta.

(i) Oxygen,
(ii). Whole body, Lungs,
(iii) Liver, Kidney
(iv) Liver,
(v) Hormones, Endocrine glands,
(vi) Tissues.

Origin: R.B.Cs. or erythrocytes are minute biconcave disc-like structures, flat in the center and thick and round at periphery in the blood formed in the red bone marrow of the long bones and bregot bone.
Function: They help in the transportation of oxygen and carbon dioxide to the different parts of the body.

Cardiac Cycle:
It is the sequential phenomenon of contraction and relaxation of the heart. The action potential causes atria and then ventricles to undergo contraction (systole) followed by their relaxation (diastole). Systole forces blood to move from the atria to the ventricles and to the pulmonary artery and the aorta, then. The heart beats 72 times in a minute. So several cardiac cycles are done per minute. The duration of the cardiac cycle is 0-8 seconds. Two heart sounds are heard by a stethoscope during each cardiac cycle.

The blood entering the kidneys contains excretory substances such as urea, uric acid, etc. These substances are removed from the blood in the kidneys and the blood is free from the waste: products of metabolism when it leaves the kidneys.

Double circulation means that the blood flows twice in the heart before it completes one full round-the short pulmonary (lung) circulation and the long systemic (general body) circulation.
For this reason, blood circulation in the human body is also called double circulation.

(a) Blood vessels entering the liver:
(i) Hepatic artery (from the aorta into the liver).
(ii) Hepatic portal vein (from stomach and intestine into the liver).
(b) Blood vessel entering the kidney: Renal artery (from the aorta into the kidney).
(c) Blood vessel leaving liver: Hepatic vein (from the liver into posterior vena cava)
(d) Blood vessel leaving kidney: Renal vein (from the kidney into posterior vena cava).

Circulatory system is also called transport system because it transports food, water, hormones, enzymes, electrolytes, antibodies and respiratory gases to or away from the body tissues.

In arteries blood flows with pressure but in veins the pressure falls considerably and the back flow of blood is prevented by the semilunar valves.

People have a common belief that the heart is located on the left side of the chest because the narrow end of the roughly triangular heart is pointed to the left side and during its working, the contraction of the heart is more powerful on the left side which can be felt.

Circulatory system is also called transport system because it transports food, water, hormones, enzymes, electrolytes, antibodies and respiratory gases to or away from the body tissues.

Formation of blood corpuscles like WBC and RBC by the bone marrow and lymph nodes is called haemopoiesis. Bone marrow and lymph nodes are called haemopoietic tissues.

The passage of White Blood Corpuscles through an unruptured wall of blood vessels is known as diapedesis. It also helps in engulfing the germs and also protects the body from getting infected.

Systems of veins carrying blood capillaries of the intestine to the liver in mammals is called the hepatic portal system. The blood from the intestine carries digested carbohydrates and proteins, i.e., glucose and amino acids to the liver which converts them into glycogen and urea respectively.

In mammals the heart produces two separate circulations, the pulmonary to the lungs and systemic to the rest of the body. These two separate circulations are jointly called double circulation. From the right ventricle deoxygenated blood goes to the lung for purification and
comes back to left auricle through pulmonary vein after purification which is known as pulmonary circulation,. Distribution of blood from the left ventricle to different parts of the body and back to hearts as deoxygenated blood is known as systemic circulation.

Pulse rate indicates the rate at which the heart beats. Each heartbeat results from the contraction (systole) and relaxation (diastole) of the heart. Both the auricles contract at a time and pour the blood into the main artery (dorsal aorta). The systole and diastole take 0.8 secs., which is 75 beats per minute.

When the blood flows in the artery it exerts pressure on the elastic wall of the artery which is called blood pressure. It is greater during systole (contraction) than during diastole (relaxation) of the heart. In a normal adult, the blood pressure is 120/80 where systolic is 120 and diastolic pressure is 80 mm of Hg (mercury).

(i) Veins.
(ii) Pocket valves.
(iii) These structures maintain the flow of blood in one direction only by preventing its back¬flow.
(iv) Yes. These are present in lymph vessels.
(v) The heart is located towards the top side of the figure.

(A) Red blood cells
(B) RBC in section
(C) Basophil
(D) Neutrophil
(E) Lymphocyte
(F) Monocyte
(G) Eosinophil
(H) Platelets.

(i) Atrial systole.
(ii)
(1) Left pulmonary artery
(2) Superior vena cava
(3) Aorta.
(iii) Simultaneous contraction of both the auricles. Because the cuspid valves are open, allowing blood to flow into ventricles.