Question

The blood vascular system of mammals is known as double vascular system because
A. A group of arteries carries oxygenated and other groups of veins conducts deoxygenated blood
B. Oxygenated blood runs from heart to different organs by one set of arteries while deoxygenated blood runs from heart to lung by pulmonary artery
C. The two different systems never meet
D. All of the above

Answer 1

Hint:- The heart in mammals and birds is divided into four chambers: two atria and two ventricles. The efficiency of the double circulation is due to the separation of oxygenated blood from the deoxygenated blood. The human heart is called myogenic as it is autoregulated by specialized muscles or nodal tissue.

Complete step-by-step solution:-The process of double circulation in human beings is discussed below:
The deoxygenated blood pumped into the pulmonary artery by the right ventricle is passed on to the lungs from where the oxygenated blood is carried by the pulmonary veins into the left atrium. This pathway constitutes the pulmonary circulation.
The oxygenated blood entering the aorta is carried to the tissues from where the deoxygenated blood is collected and finally emptied into the right atrium. This is the systemic circulation.
The systemic circulation provides nutrients, oxygen, and other essential substances to the tissues and takes carbon dioxide and other harmful substances away for elimination.
The circulation from the right ventricle to the lungs and back to the left atrium for oxygenation of the blood and the circulation from the left ventricle to the entire systemic circulation and back to the right atrium in oxygenated blood completes the process of double circulation.
Hence, the correct answer is option D, i.e. all of the above.

Note:- A special neural centre in the medulla oblongata can moderate the cardiac function through autonomic nervous system (ANS). The ANS is divided into two parts (i) sympathetic nervous system which increases the rate of heart beat and the strength of ventricular contraction and thereby the cardiac output and (ii) parasympathetic nervous system which decreases the rate of heart beat, speed of conduction of action potential and thereby the cardiac output. The cardiac output also gets increased by the action of hormones secreted by adrenal medullary.