The diagram given alongside represents the human heart in one phase of its activity. Study the same and then answer the questions that follow:

(a) Name the phase.

(b) Which part of the heart is contracting in this phase? Give a reason to support your answer.

(c) Name the parts numbered 1 to 6.

(d) What type of blood flows through the parts marked ‘1’ and ‘2’ respectively?

(e) How many valves are closed in this phase?

(a) The phase is ventricular systole & auricular diastole.

Explanation: The phase is ventricular systole as it is shown in the diagram above that both the ventricles are contracting & the tricuspid & bicuspid valves are closing. It shows auricular diastole as atria draws in blood through the openings of venacava & pulmonary vein.

(b) Ventricles are contracting in this phase as systole itself means the contraction phase of the heart. During this blood passes into aorta & pulmonary artery through semiluy valves.

Explanation: Ventricular systole indicates the contraction phase of ventricular muscles & the closure of tricuspid & bicuspid valve. Blood passes into aorta & pulmonary artery through the semilunar valves & atria draws in blood through the openings of venacava & pulmonary vein.

(c) The following parts as mentioned as given in the diagram:

1: Pulmonary artery (blood vessel carrying de oxygenated blood from right ventricle to lungs)

2 : Aorta (blood vessel carrying oxygenated blood from left ventricle to all parts of the body)

3 : Pulmonary vein (blood vessel carrying oxygenated blood from lungs to left auricle)

4 : Left auricle (heart chamber receiving oxygenated blood lungs via pulmonary vein)

5 : Bicuspid valve (valve having two cusps present at the aperture between right auricle and right ventricle)

6 : Right ventricle (chamber of heart receiving de oxygenated blood from all parts of body via venacava)

(e) Through part (1) i.e. pulmonary artery de oxygenated blood flows from right ventricle to the lungs while through part (2) i.e. aorta oxygenated blood flows from .

(e) Two valves are closed in this phase : Tricuspid valve (present at aperture between right auricle and ventricle) & bicuspid valve (present at aperture between left auricle and ventricle).