Arteries are blood vessels arising out of the heart and supplying blood to all the parts of the body. Veins are blood vessels that bring blood from different parts of the body back to the heart.
How does the blood flow in the veins? Answer
The blood flows in the veins by the action of the muscles of the veins and those of the skeletal muscles surrounding them.
Which are the two chambers of the heart? Which of the two is more muscular? Answer
The two chambers are the upper atria ( auricles) and the lower ventricles. The ventricles are more muscular.
What are the functions of the following in the heart:
ii) Inferior vena cava
iii) Auriculoventricular valve
iv) Semilunar valve Answer
i) Aorta: It is a major blood vessel into which the ventricle pumps the oxygenated blood.
ii) Inferior vena cava: The vein that collect the blood coming from the different parts of the body and pours it into the right auricle.
iii) auriculoventricular valve: The valve between the auricles and the respective ventricle allowing the movement of blood in only one direction, that is, from the auricle into the ventricle and not vice- versa.
iv) Semilunar valve: The valve having three semi- lunar shaped flaps. These valves only allow the flow of blood from the auricle into the aorta.
The contraction of the heart is called the systole and the relaxation of the heart is called the diastole.
What are the stages in the pumping action of the heart? Answer
There are three stages in the pumping action of the heart. They are:
Joint diastole (auricular and ventricular)
What are the ‘lub’ and ‘dub’ sounds produced by the heart? Answer
These are sounds of the heartbeat and they are produced when the valves close during the contraction or relaxation of the heart. At the start of the ventricular contraction or systole, the auriculoventricular valve closes with a ‘lub’ sound. The ‘dub’ sound is produced when the semilunar valve at the entrance of the aorta closes at the beginning of the joint diastole that is the relaxation of both ventricles and auricles.
What initiates and controls the pumping action of the heart? Answer
The pumping action of the heart is initiated by a set of muscles called the sinoatrial node ( SAN). The rate of the heart beat is also controlled by the nerves and the hormones.
ECG stands for electrocardiogram. It is the recording of the electro potential changes over the heart muscles. It is used for detecting any abnormality in the functioning of the heart that reflects as a change in the regular ECG pattern.
What is the normal value for blood pressure? Which instrument is used to measure the blood pressure? Answer
The normal value for blood pressure is 120/80 mm of Hg. Sphygmomanometer is used to measure the blood pressure.
If a finger is kept at a spot where an artery runs close to the body surface, the rhythmic is movement generated by the contraction and relaxation of the heart can be felt. It is found to be the same as the heart rate. The number of pulses per minute is called the pulse rate.
The right ventricle pumps blood into the pulmonary artery that carries it to the lungs. After purification in the lungs, the blood is carried back by the pulmonary vein to the left auricle of the heart. This circulation of blood between the heart and the lungs is called pulmonary circulation.
What are the components of the lymphatic system? Answer
The components of the lymphatic system are:
The fluid lymph
The channels through which the fluid flows- smaller lymph vessels and larger lymph ducts
The enlarged cavities called the lymph glands or nodes
What is tissue fluid? How it is formed? Answer
The fluid that escapes from the blood vessels into the interstitial spaces is called the tissue fluid. The blood flows under high pressure in the arteries. These arteries branch out as arterioles and then as capillaries. The walls of these vessels are very thin. The blood under pressure comes out into the tissue spaces. The cellular components and the larger proteins are not able to come out. Thus, the blood without the cells and the proteins is called the tissue fluid.
What are lymph nodes? Name one. Answer
The lymph vessels and ducts are enlarged at certain areas. These enlarged portions are called the lymph nodes or lymph glands. They contain lymphocytes that are involved in the production of antibodies during infection. The nodes are also lined by phagocytic cells that engulf the foreign bodies like the bacteria. The tonsil in the throat is an example of a bacterial infection.
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