रक्त: परिभाषा और अवयव

• Blood is a vital bodily fluid in humans and other animals
• It delivers necessary substances such as oxygen and nutrients to the cells
• It transports metabolic waste products away from those same cells

Blood Components

• Blood is composed of plasma, red blood cells, white blood cells, and platelets

Plasma

• Plasma is the liquid component of blood, making up about 55% of its volume
• It is mostly water (about 92% by volume) and contains dissolved proteins, glucose, mineral ions, hormones, carbon dioxide, and blood cells

Red Blood Cells (Erythrocytes)

• Red blood cells (RBCs) are the most abundant type of blood cell
• They are responsible for carrying oxygen from the lungs to the body's tissues and carbon dioxide as a waste product back to the lungs
• RBCs contain hemoglobin, an iron-rich protein that binds to oxygen, enabling efficient oxygen transport
• Mature red blood cells are flexible and assume the shape of a biconcave disc
• This shape optimizes their surface area for oxygen exchange and allows them to squeeze through narrow capillaries
• Red blood cells do not have a nucleus, which allows them to contain more hemoglobin and thus carry more oxygen

White Blood Cells (Leukocytes)

• White blood cells (WBCs) are involved in the immune system, protecting the body against infectious diseases and foreign invaders
• There are several types of WBCs, each with specific functions
• Neutrophils, lymphocytes, monocytes, eosinophils, and basophils are all types of white blood cells

Platelets (Thrombocytes)

• Platelets are small, irregularly shaped cell fragments
• They are involved in blood clotting (coagulation)
• Platelets adhere to damaged blood vessel walls and form a plug to stop bleeding

Blood Types

• Blood types are classified based on the presence or absence of certain antigens on the surface of red blood cells

ABO Blood Group System

• The ABO system is the most important blood group system
• It is based on the presence or absence of A and B antigens
• Type A blood has A antigens, type B has B antigens, type AB has both A and B antigens, and type O has neither
• Antibodies against the antigens not present on a person's red blood cells are found in their plasma
• For example, a person with type A blood has anti-B antibodies

Rh Factor

• The Rh factor, also known as the D antigen, is another important antigen
• People who have the Rh factor are Rh-positive (Rh+), while those who do not are Rh-negative (Rh-)
• Rh incompatibility between a pregnant woman and her fetus can lead to complications
• If an Rh-negative mother is carrying an Rh-positive fetus, she can develop antibodies against the Rh factor, which can attack the fetus's red blood cells in subsequent pregnancies

Blood Type Compatibility

• Blood transfusions must be compatible to avoid adverse reactions
• Type O-negative blood is the universal donor because it lacks A, B, and Rh antigens
• Type AB-positive blood is the universal recipient because it has no antibodies against A, B, or Rh antigens

Blood Clotting (Coagulation)

• Blood clotting is a complex process that prevents excessive bleeding when a blood vessel is injured
• It involves a cascade of enzymatic reactions that result in the formation of a blood clot

Steps of Blood Clotting

• Vasoconstriction: The blood vessel constricts to reduce blood flow to the injured area
• Platelet Plug Formation: Platelets adhere to the damaged vessel wall and form a temporary plug
• Coagulation Cascade: A series of clotting factors are activated, leading to the formation of fibrin
• Fibrin Clot Formation: Fibrin strands form a mesh that strengthens the platelet plug and creates a stable blood clot

Clotting Factors

• Clotting factors are proteins in the blood that are essential for blood clot formation
• They are produced in the liver and circulate in the blood in an inactive form
• Vitamin K is required for the synthesis of several clotting factors

Blood Diseases

• Blood diseases can affect any of the blood components and can have a wide range of symptoms and severity

Anemia

• Anemia is a condition characterized by a deficiency of red blood cells or hemoglobin
• This leads to reduced oxygen-carrying capacity of the blood
• Iron-deficiency anemia, vitamin deficiency anemia, and aplastic anemia are types of anemia

Leukemia

• Leukemia is a cancer of the blood-forming tissues, including the bone marrow
• It results in the production of abnormal white blood cells that do not function properly
• Acute leukemia and chronic leukemia are types of leukemia

Hemophilia

• Hemophilia is a genetic bleeding disorder caused by a deficiency of certain clotting factors
• People with hemophilia experience prolonged bleeding after injuries or surgery

Thrombocytopenia

• Thrombocytopenia is a condition characterized by a low platelet count
• This can lead to excessive bleeding and bruising

Blood Transfusions

• Blood transfusions are the process of transferring blood or blood components from one person to another
• They are used to treat various medical conditions, such as anemia, blood loss, and bleeding disorders

Types of Blood Transfusions

• Whole blood transfusions: Involve the transfusion of all blood components
• Packed red blood cell transfusions: Involve the transfusion of only red blood cells
• Platelet transfusions: Involve the transfusion of only platelets
• Plasma transfusions: Involve the transfusion of only plasma

Blood Transfusion Risks

• Transfusion reactions: Occur when the recipient's immune system attacks the transfused blood cells
• Infections: Blood transfusions can transmit infectious diseases, such as hepatitis and HIV
• Iron overload: Frequent blood transfusions can lead to iron overload, which can damage organs