Heart

Question 1 Name the largest artery in our body?

Question 2 What is the meaning of double circulation?

Question 3 Explain the double circulation of blood in human heart?

Question 4 Describe the structure and function of human heart?

Question 5 What is cardiac cycle?

Question 6 Define the term systole?

Question 7 Define the term diastole?

Question 8 What is blood pressure?

Question 9 Name the instrument used to measure blood pressure?

Question 10 Define systolic pressure?

Question 11 Define diastolic pressure?

Heart:

Heart

1)It is a muscular organ,big as our fist,reddish brown in colour,situated between the 2 lungs in middle of thoracic cavity,surrounded by 2 layered sac.

2)It has different chambers to prevent the oxygen rich blood from mixing with blood containing carbon dioxide.

3)Heart is divided by septa into 2 halves ie the right and left.Each half consist of 2 chambers:upper atrium and lower ventricle.Thus heart has 4 chambers:Right atrium,left atrium,right ventricle,left ventricle.

4)There are valves between left atrium and left ventricle and between right ventricle.These valves provide one-way passage and prevent return of blood.

5)The valves of heart are made up of cardiac muscles.

 Double circulation

The sequence of events which take place during the completion of one heart beat is called cardiac cycle.

It involves repeated rhythmic contraction and relaxation of heart muscles.

Contraction is called systole

Relaxation is called diastole.

1)Oxygen rich blood from the lungs enter the left atrium.The left atrium relaxes when it is collecting the blood.Then it contracts while next chamber ie left ventricle expands so that blood is transferred to it.

2)From left atrium the blood is transferred to left ventricle through bicuspid valve.From the left ventricle the blood is pumped to various parts of body through aorta(largest artery).Oxygenated blood from lungs enters the left atrium through pulmonary veins.

3)The de-oxygenated blood from various parts of the body is poured into right atrium through large veins called vena cava.

4)As the right atrium contracts,the corresponding right ventricle expands and blood through tricuspid valve gets collected.It then pumps it to the lungs for oxygenation by pulmonary arteries.In the lungs this blood become oxygenated and return to the heart by pulmonary veins.

The blood circulation in human heart is Double Circulation.This means that blood passes through heart twice.One circulation involves entry of blood from all body parts to heart.This blood is deoxygenated which goes to lungs for oxygenation.The second circulation involves entry of oxygenated blood from lungs to heart and then to all body parts.

The force that blood exerts against the walls of a vessel is called Blood pressure.

It is measured by Sphymamometer.

The pressure of blood inside artery during ventricular contraction is called Systolic pressure.

The pressure of blood inside artery during ventricular relaxation is called Diastolic pressure.

It is 120mm of Hg /80mm of Hg

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