Question

Which type of circulation is found in rats?
A. Open and double
B. Open and single
C. Closed and single
D. Closed and double

Answer 1

The circulatory system transfers oxygen and nutrients to the tissues of the body for metabolization and extracts carbon dioxide and other metabolic waste from the body for elimination.

Complete answer:
A tube carrying deoxygenated blood in the reverse direction called a "vein".It starts from the capillaries and ends back at the heart. Note that in this respect, the pulmonary artery and the vein are exceptional. The heart is a four-chambered muscular pump situated inside the pericardium in the thoracic cavity. The pulmonary circulation is supplied from the right side and the systemic circulation from the left side. There is an atrium (the anterior chamber which receives blood) and a ventricle on each side of the heart (a thicker-walled chamber whose contractions drive the blood out of the heart). The systemic venous blood (deoxygenated) from the cranial vena cava and the caudal vena cava is formed from the right atrium and the coronary sinus. The right atrium contracts the blood into the right ventricle and drives it.
The right ventricle chamber contraction forces the blood to enter the pulmonary artery and from there to the lungs, where it gets oxygen. In the pulmonary vein, oxygenated blood from the lungs enters the left atrium of the heart.
The blood is forced into the left ventricle by contraction of the left atrium. The left ventricle contraction drives the oxygenated blood to the remainder of the body through the aorta. The presence of valves that prevent the backflow of blood increases the potency of these contractions. A series of 'atrioventricular valves' is located between each atrium and its corresponding ventricle. Between the right atrium and the ventricle, the tricuspid valve is present. Between the left atrium and the ventricle, the bicuspid valve is present. Between the aorta and the left ventricle, semilunar valves are present. At the junction of the pulmonary artery and the right ventricle, a series of valves is located. Such valves block the flow of blood back into the chamber. The valves keep the chordae tendineae from flapping back into the atrium. The arterial flow to the heart is provided by the left and right coronary arteries, originating from the aorta.
Rats show double circulation. The oxygenated blood is isolated from the venous blood found in the right chamber in the left chamber of the auricles of the heart and the blood produced in the heart passes through it twice, once through the pulmonary circulation of the lungs and other times through different body systems.
So, choice D- Closed and double is the correct answer.

Note: The coronary veins follow the arteries' path and open through the coronary sinus into the left atrium. In the epicardium, the lymphatic vessels run and merge into trunks and ultimately drain into the nodes of the tracheo-bronchial lymph.