Circulatory System

There are four parts circulatory system: - Heart, blood, arteries, and veins.

1. Blood:

Blood is the fluid which flows in blood vessels. It transports substances like digested food from the small intestine to the other parts of the body. It carries oxygen from the lungs to the cells of the body. It also transports waste for removal from the body. Blood is a liquid, which has cells of various kinds. The fluid part of the blood is called plasma.

Blood contains two types of cell 1) RBC (red blood cells) 2) WBC (white blood cells).

RBC:-

It is also called erythrocytes. Its red color is due to a red pigment called hemoglobin. RBCs are formed in the bone marrow in the adults. The average lifespan of 120 days after which they are destroyed in the spleen (graveyard of RBCs) and liver. Hemoglobin contains iron, iron is responsible for transporting the oxygen from lung to the whole body. They don’t have nucleus except- camel and lama. Anemia disease is caused due to the deficiency of hemoglobin. RBC reduce 5% while sleeping and increased 30% while on the height of 4200 meters.

WBC:-

It is also called Leucocytes. fight against germs that may enter our body. Lifespan is 1-2 days. The nucleus is present.ratio of RBC to WBC is 600:1. There Are two different type of white blood cell:

●Granulocytes have visible granules or grains inside the cells that have different cell functions. Types of granulocytes include basophils, neutrophils, and eosinophils.

●Agranulocytes are free of visible grains under the microscope and include lymphocytes and monocytes.

  1. monocytes= the largest of the types of white blood cells. Monocytes turn into macrophages when they exit the bloodstream.do the job of phagocytosis (cell-eating) of any type of dead cell in the body, whether it is a somatic cell or a dead neutrophil. When there is tissue damage or infection macrophages provide the first line of defense in protecting the host from infection.

  2. Lymphocytes= smallest type of WBC. have a large nucleus within a small amount of cytoplasm.B lymphocytes(called because they develop in bone marrow) make antibodies, T lymphocytes cell((so-called because they develop in a small organ called the thymus gland)response by recognizing the presence of a foreign antigen and then stimulating antibody production and natural killer cell(NK cell) kill the cell which is virus infected it has Cytotoxic .

  3. Neutrophils=most abundant WBC. they defense against bacteria and fungus.they are first to defense against infections.they are also known as Polymorphonuclear (PMN).

  4. Eosinophils= They are second least among all WBC nearly 2-4% of total WBC. They defend from allergies and worm infestations by realizing toxic.

  5. Basophil= they are the least cell among all WBC cell, contain histamine for inflammatory responses. Histamine is responsible for widening blood vessels and increasing the flow of blood to the injured tissue.

Platelets:-

These cell clot the blood when we injured. There is no nucleus. Forms in bone marrow. lifespan is 3-5 days. They die in the spleen.

ABO Blood group:-

The difference blood of a human is due to glycol protein (antigen) found in RBC. The antigen is of two types- Antigen A and Antigen B.

An opposite type of protein found in plasma called antibody. They are of two types of antibody ‘a’ and antibody ‘b’.

The same antibody and antigen cannot live together. If same antigen and antibody mix together, they spoil blood, it is called agglutination of blood.

Blood Group	Antigens on RBCs	Antibodies in Plasma	Donor’s Group
A	A	Anti-B	A, O
B	B	Anti-A	B, O
AB	A, B	Nill	AB, A, B, O
O	Nill	Anti-A, B	O

Blood ‘O’ is called universal donor because it does not have any antigen. Blood ‘AB’ is called universal receiver because it does not have any antibody.

Rh factor— Another antigen Rh antigen. Found on the surface of RBC, who has Rh antigen called Rh positive and Rh negative respectively. It was discovered in the Rhesus monkeys.

2. Blood vessels: -

There are two types of blood vessels.1) Arteries 2) Veins.

Arteries: -  Arteries carry oxygen-rich blood from the heart to all parts of the body. Arteries have thick elastic walls.

Veins: -  Veins are the vessels which carry carbon dioxide-rich blood from all parts of the body back to the heart. The veins have thin walls. There are valves present in veins which allow blood to flow only towards the heart.

Capillaries:

Arteries and veins divide into smaller vessels. On reaching the tissues, they divide further into extremely thin tubes called capillaries. The capillaries join up to form veins which empty into the heart.

There is an exception in vein and arteries.

Pulmonary artery: carry carbon dioxide-rich blood from heart to lung.

Pulmonary vein: carry oxygen-rich blood from lung to heart.

3. Heart:-

The heart is an organ which beats continuously to act as a pump for the transport of blood, which carries other substances with it. Situated in the Thoracic cavity or chest cavity in between the two lungs, slightly tilted to the left. It is protected by a double-walled membranous bag called pericardium. the heart has four chambers. The two small upper chambers are called the atria (singular: atrium) and the two larger lower chambers ventricles. There is a valve in each chamber, they direct the blood in the heart. A thin, muscular wall called the interatrial septum separates the right and the left atria and thick-walled, the inter-ventricular septum, separates the left and the right ventricles. A doctor uses the stethoscope to listen to the heartbeats.