Composition of Blood

Composition of Blood

• Blood is a complex connective tissue composed of formed elements (cells and cell fragments) suspended in a liquid matrix called plasma.
• Plasma is about 55% of whole blood volume.
• Plasma primarily consists of water (90%), proteins (7%), and other solutes (3%).
• Plasma proteins include albumin, globulins, and fibrinogen, with various roles in blood function.
• Albumin maintains osmotic pressure, globulins transport lipids and some hormones, and fibrinogen plays a critical role in blood clotting.
• Formed elements include red blood cells (erythrocytes), white blood cells (leukocytes), and platelets (thrombocytes).
• Red blood cells are responsible for oxygen transport.
• White blood cells are crucial for immune defense, with various types performing different functions.
• Platelets are essential for blood clotting.

Red Blood Cells (Erythrocytes)

• Erythrocytes are biconcave discs that lack a nucleus in mature form.
• They contain hemoglobin, a protein that binds oxygen.
• Hemoglobin gives blood its red color.
• Red blood cells are specialized for oxygen transport.
• The biconcave shape increases surface area for efficient gas exchange.
• Erythropoiesis, the production of red blood cells, occurs in the bone marrow.
• Red blood cell lifespan is approximately 120 days.
• Aged or damaged red blood cells are removed from circulation by the spleen and liver.

White Blood Cells (Leukocytes)

• Leukocytes are crucial for immune defense.
• They are larger than red blood cells and have a nucleus.
• Different types of white blood cells include neutrophils, lymphocytes, monocytes, eosinophils, and basophils, each with specific roles in immune response.
• Neutrophils are phagocytes that engulf and destroy pathogens.
• Lymphocytes are involved in antibody production and cellular immunity.
• Monocytes differentiate into macrophages, phagocytosing pathogens and debris.
• Eosinophils are involved in allergic reactions and parasitic infections.
• Basophils release histamine, contributing to inflammation.

Platelets (Thrombocytes)

• Platelets are cell fragments vital for blood clotting.
• They are produced from megakaryocytes in the bone marrow.
• Platelets circulate in the blood until needed to initiate clot formation.
• When a blood vessel is damaged, platelets adhere to the site, aggregate, and release clotting factors.
• These factors initiate a cascade of reactions that lead to fibrin formation, creating a mesh to stop bleeding.
• Blood clotting is a complex process to prevent excessive blood loss from damaged vessels.

Blood Types

• Blood is categorized into different types based on the presence or absence of specific antigens on red blood cell surfaces.
• The most common blood typing system is ABO, which categorizes blood into types A, B, AB, and O, based on the presence of A and/or B antigens.
• Another critical blood typing system is the Rh system, with positive and negative designations depending on the presence (positive) or absence (negative) of the Rh antigen.
• Blood transfusions must be carefully matched for compatibility to prevent adverse reactions.

Blood Disorders

• Several disorders can affect blood components.
• Anemia is characterized by a deficiency in red blood cells or hemoglobin.
• Leukemia involves uncontrolled proliferation of white blood cells.
• Hemophilia is a hereditary disorder affecting blood clotting factors.
• Sickle cell disease is a genetic disorder affecting hemoglobin structure, leading to deformed red blood cells.
• These disorders can be caused by genetic mutations, environmental factors, or other underlying conditions.

Blood Functions

• Blood plays essential functions in the body, including:
• Transportation of oxygen, nutrients, hormones, and waste products.
• Regulation of body temperature, pH, and fluid balance.
• Protection against infections and blood loss through immune cells and clotting mechanisms.
• Blood is a vital fluid circulating throughout the body, carrying out critical functions for life.