Blood Cells: Definition, Composition, and Functions

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What are Blood Cells?

o Fluid that helps in transportation of oxygen to all tissues and lungs with the nutrient is the blood.

o Blood consists of components i.e., plasma, white blood cells, red blood cells and platelets.

o Blood helps in the regulation of body temperature along with the filtration of blood from kidney and liver.

o Blood transports to different parts through the arteries, capillaries and veins in the form of whole blood in which plasma is present 55% of it and remaining 45% are the blood cell.

o Blood holds 7% to 8% of the total body weight of a person. Average male has blood range of about 4500 mL to 5700 mL.

Blood Cells

o Blood cells are formed by the process of hematopoiesis by the hematopoietic stem cells but develop in the bone marrow (mostly found in pelvic bones, spine and breast bones of an adult).

o The hematopoietic stem cells able to form red blood cells, platelets and white blood cells.

o The lymph nodes, liver and the spleen help in regulation of the blood cells production, differentiation and destruction of these cells.

o The immature blood cells from the stem cells are called the blast, that may remain in the marrow to mature. Other cells mature and function as blood cells.

Components of Blood

1. Red Blood Cells (RBCs)

Red Blood Cells are also known as the erythrocytes that are biconcave and anucleate cells containing hemoglobin.

o The RBCs help in transportation of carbon dioxide and oxygen between tissue and lungs.

o Red blood cells are formed in the red bone marrow (that forms into the blood cells) by the process known as erythropoiesis.

o These erythrocytes survive for 100 days to 120 days that are then recycled by the help of macrophages of liver, lymph nodes, bone marrow and spleen.

o Erythrocytes helps in the determining the blood types along with the gas exchange transportation of oxygen and carbon dioxide between the tissue.

2. White Blood Cells (WBCs)

o White Blood Cells (WBCs) also known as the leukocytes and are a part of immune system helping fight infection and protects against the foreign material.

o WBCs are of different types that help in the recognition and killing the harmful bacteria.

o WBCs help in the production of antibodies for defense of body from future exposure by the foreign material or bacteria and fungi.

i. Neutrophils

o Majority of the WBC are neutrophils and are the first responders to act in the immune response and alert other cells for the immune response.

o The survival time for the neutrophils are eight hours after release from the bone marrow and about 100 billion are produced every day.

ii. Eosinophils

o 5% of the WBCs make the eosinophil but concentration of the eosinophils are highest in the digestive tract.

o Eosinophil helps in the fighting against the foreign organism especially the parasites.

o Eosinophils are known for the production of allergy symptom against allergen that considered as the invader.

iii. Basophils

o 1% of the WBC cells are basophils that help in immune response specially non – specific immune response to the pathogens. When triggered, basophil release histamine resulting in the inflammation and bronchoconstriction in the airways. This non – specific immune response observed in the asthma attack.

iv. Monocytes

o About 5% to 12% of the WBCs makes the monocytes. The monocytes functions to migrate the dead cells from the tissues. Acts as the garbage carrier of immune system.

v. Lymphocytes

o There are two types of lymphocytes namely T and B lymphocytes.

The T – lymphocytes are the WBCs that kills the foreign invader directly whereas, B – lymphocytes are like other WBCs help in activation of humoral immunity.

o These lymphocytes help in the production of the memory cells that remembers the invaders and protects the body against such invaders in the future.

o The hematopoietic stems cells proceed to the lymphoid cell line via lymphoid stem cell giving rise to B-lymphocyte or T-lymphocytes.

3. Platelets

o The platelets are also known thrombocytes. They are membrane bound cell fragments derived from the fragmentation of precursor cells called megakaryocytes by the process of thrombopoiesis.

o Platelets are responsible for the blood clothing process that helps in the wound healing process.

o Platelets do not have nucleus and irregularly shaped and not defined cells but the fragments.

o Platelets clot blood by the coagulation. Platelets release certain factors that accumulate on the injury leading to the clotting.

Complete Blood Count

o Complete blood count gives the total number of RBCs, WBCs and platelets in the blood with their percentages.

o The complete blood count test help diagnose the conditions like anemia, infection or other disorders.

o The platelet count from the CBC helps understand to evaluate the bleeding and the disorders in the clotting.

Blood Test

o These tests include the complete blood count that includes the following;

o White Blood Cell count

o Red Blood Cell count

o Differential blood count

o Platelet count

o Hematocrit red blood cell volume

o These tests help diagnose the anemia and other certain cancers of blood with blood disorders.

o Test like the platelet count help diagnose the clotting and bleeding disorders.

o Prothrombin time and Partial thromboplastin time tests help to evaluate bleeding and clotting disorders to observe the anticoagulation therapies of the blood.

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Digestive System Disorder: Types, Definition, and Treatment

Human Respiratory System: Definition, Mechanism, and Facts

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