Blood_TB- Human Bio

Cardiovascular System

Blood

Functions of Blood

  • Transportation:

    • Transports oxygen, nutrients, wastes, carbon dioxide, and hormones.

  • Defense:

    • Protects against pathogens;

      • White blood cells (WBCs) phagocytize microbes.

      • Some produce antibodies that disable pathogens.

  • Regulatory Functions:

    • Maintains body temperature, water-salt balance, and pH levels.

  • Protects Against Fluid Loss:

    • Involves clotting mechanisms.

Composition of Blood

  • Fluid Connective Tissue:

    • Average adult contains 5-6 liters of blood.

  • Formed Elements: Produced in red bone marrow:

    • Red Blood Cells (RBCs): Erythrocytes.

    • White Blood Cells (WBCs): Leukocytes.

    • Platelets: Cell fragments.

  • Plasma:

    • 91% water and 9% salts and organic molecules.

    • Plasma proteins are the most abundant molecules.

Plasma Composition

  • Percent by Volume:

    • Water: 91%

    • Proteins (albumins, globulins, fibrinogen): 7%

    • Other Solutes (ions, nutrients, waste products, gases, hormones, vitamins): 2%

  • Cells and Platelets:

    • Comprise 45% of blood.

Characteristics of Plasma

  • Composed of 10% plasma proteins and 90% water.

  • Major Types of Plasma Proteins:

    • Albumin: Most abundant, maintains osmotic balance, regulates pH, transports molecules (e.g., bilirubin).

    • Globulins: Carrier proteins that bind hormones, fatty acids, ions.

    • Fibrinogen: Inactive precursor to proteins that form clots.

Blood Plasma Solutes

  • Plasma Proteins: Albumin, globulins, fibrinogen.

  • Inorganic Ions: Na, Ca², K, Mg², Cl, HCO3, HPO4², SO4².

  • Gases: O2, CO2.

  • Organic Nutrients: Glucose, fats, phospholipids, amino acids.

  • Nitrogenous Waste Products: Urea, ammonia, uric acid.

  • Regulatory Substances: Hormones, enzymes.

Red Blood Cells (RBCs)

  • Produced in red bone marrow.

  • Average lifespan of ~120 days.

  • Male RBC Count: 4.6 – 6.2 million/μL

  • Female RBC Count: 4.2 – 5.4 million/μL.

Hematocrit

  • Defined as the volume of blood occupied by red blood cells.

  • Varies based on individuals' oxygen requirements; athletes may have higher hematocrit due to training at high altitudes.

Structure of Red Blood Cells

  • Lack a nucleus and few organelles.

  • Biconcave shape increases surface area for gas exchange.

  • Contain approximately 280 million hemoglobin molecules, which are iron-containing proteins that transport oxygen and give red color to the cells.

Carbon Dioxide Transport in the Blood

  • Transport Mechanism:

    • 7% dissolved in plasma.

    • 23% binds to the globin portion of hemoglobin (carbaminohemoglobin).

    • 70% is transported in plasma as bicarbonate ion (HCO3-).

  • Reaction Example:

    • CO2 + H2O ⇌ H2CO3 ⇌ H+ + HCO3-.

Production of Red Blood Cells

  • Produced in red bone marrow, regulated by erythropoietin (EPO) from kidneys when oxygen levels are low.

  • Old RBCs are destroyed in the liver and spleen.

Blood Doping

  • Definition: Methods used to increase the number of RBCs to enhance athletic performance.

  • Risks: Increased blood viscosity can lead to heart attacks; involves EPO injections before athletic events.

Disorders Involving RBCs

  • Anemia: Reduced RBC count or hemoglobin leading to fatigue and shortness of breath.

    • Causes include excessive bleeding, tumors in marrow, and deficiencies in iron, copper, or B12.

    • Sickle-Cell Anemia: Genetic disorder causing sickle-shaped RBCs that rupture easily.

    • Hemolytic Disease of the Newborn: Incompatibility between blood types leading to cell rupture.

White Blood Cells (WBCs)

  • Derived from red bone marrow; they have nuclei and vary in lifespan from days to years.

  • Important for fighting infections and are regulated by colony-stimulating factors (CSF).

Categories of White Blood Cells

  • Granular WBCs: Eosinophils, basophils, neutrophils.

  • Agranular WBCs: Lymphocytes and monocytes.

Neutrophils

  • 50-70% of WBCs, multi-lobed nuclei.

  • Perform phagocytosis of pathogens upon infection.

Eosinophils

  • Small percentage of WBCs; contains a bilobed nucleus and large granules.

  • Functions mainly in parasitic infections and allergic reactions.

Basophils

  • Small percentage; contains U-shaped nucleus.

  • Releases histamine during allergic responses.

Monocytes

  • Largest type of WBC with horseshoe-shaped nuclei.

  • Differentiate into macrophages in tissues to engulf pathogens and worn-out RBCs.

Lymphocytes

  • Comprise 25-35% of WBCs; have large nuclei.

  • Develop into T cells (cell-mediated immunity) and B cells (humoral immunity) important for the immune response.

Types of Lymphocytes

  • T-lymphocytes: Involved in cell-mediated immunity.

  • B-lymphocytes: Involved in antibody production.

    • Plasma cells derived from B-lymphocytes produce antibodies.

  • Leukocytosis: Increased WBC count in response to infection.

Disorders Involving WBCs

  • Leukemia: Cancer affecting WBCs, leading to uncontrolled proliferation.

    • Types: Acute leukemia (common in children).

    • Cancerous WBCs crowd out RBCs and platelets, impairing function.

    • Treatment may involve irradiation and marrow transplants.

Platelets

  • Fragments of megakaryocytes produced in the red bone marrow, crucial for blood clotting.

  • Roughly 200 billion platelets produced daily.

Blood Clotting Process

  • Steps:

    1. Blood vessel punctured.

    2. Platelets congregate, forming a plug.

    3. Platelet and tissue release prothrombin activator, initiating a cascade of reactions.

    4. Fibrin threads form to trap RBCs.

  • Key Proteins involved: Thrombin and fibrinogen, formed in the liver.

Steps in Clotting

  • Initial Steps:

    • Damage to blood vessels leads to platelet clumping.

    • Damaged cells release thromboplastin to convert prothrombin into thrombin.

    • Thrombin activates fibrinogen, allowing formation of fibrin threads that bind platelets and RBCs.

Disorders Involving Platelets

  • Thrombocytopenia: Low platelet count due to insufficient production or increased breakdown.

  • Thromboembolism: Detached clots can block blood vessels, causing heart attacks or strokes.

  • Hemophilia: Genetic condition leading to deficient clotting factors, resulting in impaired blood clotting.

Blood Types

  • RBCs can have antigens A, B, AB, or none (O).

  • Antigens trigger immune response through antibodies.

Terminology for ABO Blood Typing

  • Antigen: Foreign substance inducing an immune response.

  • Antibody: Proteins created in response to antigens, bind to them.

  • Blood Transfusion: Process of transferring blood from one individual to another.

Determinants of Blood Type

  • Based on presence or absence of antigens (A and B).

    • Antibodies present against lacking antigens on RBCs.

    • Example: Type A has A antigens and B antibodies.

Blood Compatibility

  • Recipient's antibodies can agglutinate donor's RBCs if antigens are recognized, causing rejection.

  • Crossmatching is performed to ensure compatibility.

Blood Type Compatibility

  • Universal Donor: O-

  • Universal Recipient: AB+

  • Blood transfusion table outlines donor-recipient compatibilities for all types.

Rh Blood Groups

  • Rh antigen on RBCs determines Rh+ or Rh-.

  • Rh antibodies develop only after exposure to Rh factors from another’s blood.

Importance of Rh Factor

  • Crucial during pregnancy, especially with Rh- mothers and Rh+ fathers.

  • Risk of hemolytic disease of the newborn if the mother produces anti-Rh antibodies that attack fetal RBCs.

Prevention of Hemolytic Disease

  • Rh- women receive injections of anti-Rh antibodies to prevent antibody formation that harms fetal RBCs during pregnancy.

Donating Blood

  • Safe and sterile process; ~a pint of blood is donated.

  • Plasma replaced in hours, cells in weeks, with possible mild side effects like dizziness.

  • Blood is tested for infectious diseases before donation is allowed; critical for saving lives.

  • Contraindications for donation include: history of hepatitis, malaria, or recent treatment for STIs.