Question

In mammals, the bicuspid (mitral valve), guards the opening between
a. Left atrium and left ventricle
b. Pulmonary vein and left auricle
c. Stomach and intestine
d. Right atrium and right ventricle

Answer 1

Cardiovascular system is a system containing heart and blood vessels that circulate blood throughout the body. The function of blood is to transport nutrients and oxygen to tissues. The heart is a muscular organ and contains four chambers in human beings. So, it is called a four-chambered heart.

Complete answer:
The heart of human beings is four-chambered. It contains two Atria and two Ventricles.
Sides of heart-
The right side of the heart- It has two chambers-

Right atrium- It is thin-walled and contains a Sinoatrial node (pacemaker) and an Atrioventricular node that conducts impulses to ventricles.
Right ventricle- It is thick-walled and contains a pulmonary artery.

The left side of the heart- It contains two chambers-

Left atrium- It receives oxygenated blood from the lungs through the pulmonary vein. It contains a Bicuspid valve- Blood from the left atrium enters the left ventricle through this valve. It is also termed as the Mitral valve.
Left ventricle- Thick-walled and high pressure. It contains systemic Aorta.

The heart contains four valves- The function of valves is to prevent the backflow of blood and permit blood to flow only in one direction.
Atrioventricular valves are two in number-
- Bicuspid valve or Mitral valve- Blood from the left atrium enters the left ventricle through the Bicuspid or Mitral valve.

Tricuspid valve- They open towards ventricles and prevent the backflow into atria.
Semilunar valves- It is present at the opening of the systemic Aorta and pulmonary artery and prevents the backflow of blood into ventricles.

Hence, the correct answer is option (A).

Additional information:
The problems in heart valves or failure in the functioning of these valves leads to three types of problems:
- Regurgitation: It occurs when a valve is not closed properly and leakage occurs. Blood flows back.
- Stenosis: The valve becomes narrow and does not open properly. The valve does not open fully and there is a reduced supply of blood.
- Atresia: Pulmonary atresia occurs and there is no backflow of blood.

Note: The function of valves is to prevent the backflow of blood. As the mitral valve is present between the left atrium and left ventricle, it prevents the backflow of pure blood which is coming from the pulmonary vein.