Circulatory System in Humans

The upper chambers of the heart have thin walls and are called auricle .

Aorta carries blood from the heart to various parts of the body.

Vena Cavae carry blood from different body parts towards the heart.

Circulation of blood between the heart and lungs is called Pulmonary circulation.

The normal blood pressure in an adult is 120/80 mm Hg.

auricles

Reason — Auricles have thinner walls than ventricles as they are the receiving chamber. They receive blood from different parts of the body. Ventricles pump out blood at greater pressure hence they have thicker walls.

ventricles

Reason — Ventricles are lower chambers of the heart whereas auricles are the upper chambers.

inferior vena cava

Reason — Inferior Vena Cava brings deoxygenated blood from the posterior part of the body and Superior Vena Cava brings deoxygenated blood from the anterior parts of the body.

aorta

Reason — Aorta is the main artery and it arises from the left ventricle of the heart.

AB

Reason — Blood group AB is called the universal recipient since it can receive blood from a person with any blood group.

antigen A and antibody B

Reason — Blood group A has antigen A and antibody B.

lymph

Reason — Lymph is a fluid that contains infection-fighting white blood cells.

The Pericardial fluid protects the heart from the shocks and jerks during contraction.

The bicuspid valve is present between the left auricle and left ventricle.

Oxygenated blood is found in the left side of the heart.

The Vena Cavae are large veins which carry deoxygenated blood from the body to the heart.

The largest artery in the body is aorta.

The stretching and relaxing of arteries with each heartbeat felt as throbbing is called pulse.

Cardiac cycle — The sequence of events involving repeated contraction and relaxation of heart muscles, which take place during one complete heart beat is known as cardiac cycle.

Blood pressure — The force of blood exerted against the arterial walls by the heart is called blood pressure.

Palpitation — Palpitation can be defined as a condition which is caused by anxiety, side effect of some medicine or some coronary heart disease and makes a person feel as if his heart is beating too fast, skipping a beat, or fluttering.

Hypertension — Hypertension or high blood pressure is a medical condition which creates difficulty in the flow of blood due to constriction of arterioles.

Cardiac arrest — The sudden stoppage of contraction of heart due to deposition of cholesterol and calcium on the inner walls of coronary arteries is called cardiac arrest.

Blood transfusion — The process by which blood is transferred from one person to another is called blood transfusion.

False

Correct Statement — The heart is enclosed by double-layered membrane called pericardium.

True

True

False

Correct Statement — The bicuspid valve is present between the left auricle and the left ventricle.

True

False

Correct Statement — Blood group AB is called the universal recipient.

Left side of the heart contains oxygenated blood.

The valves present in the heart prevent the blood from flowing in the wrong direction in the heart.

Inter-auricular septum is the wall separating the two auricles.

Superior Vena Cava and Inferior Vena Cava are two major veins.

For completing one round of circulation in the body, the blood passes twice through the heart. This is called double circulation. Double circulation involves two processes — Pulmonary circulation and Systemic circulation.

Pericardium.

The four blood groups in human beings are A, B, AB and O. They are named on the presence or absence of specific antigens.

The inter-auricular septum and inter-ventricular septum present between the auricles and ventricles and the valves present in the heart prevent mixing of blood between auricles and ventricles.
Septum separates the heart into the left and right sides. The valves work like a door that open only in one direction and regulate the blood flow from auricles to ventricles and various parts of the body. Bicuspid valves are present between the left auricle and left ventricle. Similarly, tricuspid valves are present between right auricle and right ventricle.

For completing one round of circulation in the body, the blood passes twice through the heart. This is called double circulation. Double circulation involves two processes: pulmonary circulation and systemic circulation.

Pulmonary circulation — The circulation of blood between the heart and lungs is called pulmonary circulation. From the right auricle, the blood flows into the right ventricle and then to the lungs through the pulmonary arteries. The oxygenated or pure blood from the lungs is brought to the left auricle by the pulmonary veins.

Systemic circulation — The circulation of blood between the heart and other body organs is called systemic circulation. From the left auricle, the oxygenated blood flows into the left ventricle and from there it is pumped into the aorta, the largest artery in the body. The aorta divides further to supply blood to all body tissues.

Below schematic diagram shows circulation of blood in the body:

A person with blood group O is called a universal donor since his blood can be given to a person with any blood group. As blood group O has neither antigen A nor B so it doesn't cause self-clumping with any antibodies making it compatible with all blood groups.
A person with blood group AB is called a universal recipient since he can receive blood from a person with any blood group. As blood group AB has no antibodies, so there is no attack on the antigens of any blood group making it compatible to receive blood from all blood groups.

Lymph is a fluid that contains infection-fighting white blood cells. When blood reaches the capillaries, some of the water and dissolved solutes are filtered out from the plasma into tissue spaces to form a tissue fluid called lymph. Some of this lymph enters tiny channels called lymph vessels.

Difference between Blood and Lymph — Basically, lymph has all the elements of blood except RBCs and blood platelets. It is slightly yellowish in colour and contains special type of white blood cells called lymphocytes.

Following are the functions of lymph:

1. Transportation — The lymph helps in transporting nutrients and hormones to the body cells. It also removes waste materials from the body cells to the tissues and finally pours them into veins. Lymph carries lymphocytes and antibodies from the lymph nodes to the blood. The lymph also absorbs and transports fats (fatty acids and glycerol) from the small intestine to the blood.
2. Defence — Lymph carries lymphocytes and antibodies, which destroy the harmful microorganisms and foreign particles in the lymph nodes. Lymph takes the bacteria entering the body to the lymph nodes for destroying them. This prevents the infection from spreading to other tissues.
3. Drainage — The lymph drains excess tissue fluid from the intercellular spaces back into the blood.

The below diagram shows the labelled parts of human heart:

Navin's blood test indicates that he has antibodies A and B but no antigen at all. This means that his blood group is O.

Ankita qualifies as his blood donor because her blood group is O- and she is an universal donor.

The Auricles have to receive blood and transfer it to the ventricles for which they do not require much force. So, they have thin walls. But the ventricles have thick walls because they need more force as they have to pump the blood out of the heart at greater pressure to the lungs (Right ventricle) and whole body (Left ventricle).