Comprehensive Study Notes on Blood and Hemodynamics for Advanced Physiology

Blood Overview

  • Long regarded historically as the source of life and personality, blood was traditionally termed the "river of life."

  • Severe blood loss often resulted in death, linking blood and life in ancient beliefs.

  • Blood was believed to possess qualities determining emotions and personality traits, such as "bad blood" leading to feuds or anger said to cause blood to boil.

  • Blood was thought to become impure through moral transgressions, linked with diseases like syphilis and AIDS.

  • Strikingly, sharing blood symbolized creating a bond, making one a "blood brother."

Hematology and Circulation

  • The scientific study of blood is called hematology, originating from the Greek root "hemat" meaning "blood."

  • Blood circulates through a closed system of blood vessels, propelled by the heart's pumping action.

Functions of Blood

Blood has three primary functions:

  1. Transport

    • Delivers oxygen (O2) and nutrients to cells.

    • Collects waste materials from cells and transports them to excretory organs.

    • Transports hormones, ions, and other vital substances.

  2. Regulation

    • Helps maintain fluid and electrolyte balance, acid-base balance, and body temperature.

  3. Protection

    • Defends against infection and contains clotting factors to prevent excessive blood loss.

Composition of Blood

Blood comprises two components:

  1. Plasma

    • A pale-yellow liquid (~55% of blood) primarily composed of water, proteins, ions, nutrients, gases, and waste products.

    • Features proteins like albumin, clotting factors, antibodies, and complement proteins aiding fluid balance, immune response, and clot prevention.

    • Serum = plasma minus clotting proteins.

  2. Formed Elements (Cells and Fragments)

    • Includes:

      • Red Blood Cells (RBCs or Erythrocytes)

      • Transport oxygen and carbon dioxide.

      • White Blood Cells (WBCs or Leukocytes)

      • Protect against infections.

      • Platelets (Thrombocytes)

      • Prevent bleeding.

    • Blood cells and fragments are primarily produced in the red bone marrow (myeloid hemopoiesis) and lymphatic tissue (lymphoid hemopoiesis).

Characteristics of Blood

  • Color varies from bright red (oxygenated) to dark blue-red (deoxygenated).

  • Volume varies by individual, averaging 4-6 liters in adults.

Functions of Blood Cells

Red Blood Cells (RBCs)

  • Normal range: 4.5 to 6 million cells/μL in men; 4.2 to 5.4 million cells/μL in women.

  • Key function: Oxygen and carbon dioxide transport.

  • Powered by hemoglobin, allowing for gas exchange.

    • Oxyhemoglobin: oxygenated form of hemoglobin.

    • Carbaminohemoglobin: CO2-bound form of hemoglobin.

White Blood Cells (WBCs)

  • Normal range: 5,000 to 10,000 cells/μL.

  • Protect against pathogens and engage in phagocytosis.

    • Types include neutrophils, basophils, eosinophils, monocytes, and lymphocytes.

Platelets

  • Normal range: 150,000 to 450,000/μL.

  • Essential for hemostasis, preventing blood loss.

Hemopoiesis

  • Blood cell formation occurs in red bone marrow and lymphatic tissue.

    • Stem cells differentiate into various blood cell types under growth factors.

    • Conditions affecting bone marrow can lead to blood cell deficiencies, as seen in myelosuppression or polycythemia vera.

Steps of Hemostasis

  • Hemostasis involves stopping bleeding and comprises:

  1. Vascular spasm: Injury causes blood vessel contraction.

  2. Formation of a platelet plug: Activated platelets adhere and aggregate at the injury site.

  3. Blood coagulation: Clotting factors form a fibrin clot stabilizing the platelet plug.

Coagulation Cascade

  • Initiated by injury, leads to the formation of prothrombin activator, converting prothrombin to thrombin, which activates fibrinogen to fibrin, trapping cells to form a clot.

Clot Retraction and Dissolution

  • Following clot formation, retraction occurs to minimize the size of the vessel opening, and clot dissolution (fibrinolysis) is carried out by plasmin.

Blood Types

ABO System

  • Blood types classified based on antigens:

    • Type A: A antigen; contains anti-B antibodies.

    • Type B: B antigen; contains anti-A antibodies.

    • Type AB: A and B antigens; contains no antibodies — universal recipient.

    • Type O: No antigens; contains both anti-A and anti-B antibodies — universal donor.

  • Importance of blood type testing prior to transfusions to prevent agglutination and hemolysis.

Rh Factor

  • Presence indicates Rh-positive blood; absence indicates Rh-negative blood.

  • Compatibility must be checked especially in pregnancies where Rh incompatibility can lead to fetal hemolytic conditions.

Special Topics in Blood

Jaundice

  • Caused by hyperbilirubinemia, indicating excessive breakdown of RBCs or impaired bilirubin processing in the liver.

Conditions Leading to Jaundice

  • Hemolytic: increased RBC breakdown, resulting in elevated unconjugated bilirubin.

  • Hepatocellular: liver damage impairs conjugation, leading to both unconjugated and conjugated bilirubin elevation.

  • Obstructive: bile duct obstruction retaining conjugated bilirubin.

Clinical Terms for the Heart and Blood Vessels

  • Anemia: Low RBC count or hemoglobin; various types based on etiology.

  • Coronary artery disease: Narrowing of coronary arteries affecting blood supply to the heart muscle.

  • Hypertension: High BP readings (> 140/90 mm Hg); chronic conditions can lead to heart failure, stroke, etc.

  • Shock: Life-threatening condition due to insufficient blood flow to organs.

Exercise and Health

  • Regular exercise increases cardiac output, decreases BP, and prevents conditions like DVT and CAD.

  • Healthy lifestyles significantly benefit cardiovascular health, enhancing blood flow and pressure regulation.