Ch17_Blood_slides (1)

Chapter 17 - Blood

Cardiovascular System Overview

• Blood: Transports various materials throughout the body, such as:

  • Oxygen (O2)

  • Carbon dioxide (CO2)

  • Nutrients

  • Ions

  • Hormones

  • Immune cells

• Heart: Pumps blood to and from the lungs and throughout the body.

• Blood Vessels:

  • Arteries: Carry oxygenated blood away from the heart.

  • Capillaries: Tiny vessels where diffusion of materials occurs between blood and tissues.

  • Veins: Carry deoxygenated blood toward the heart.

• Function: Overall, the cardiovascular system transports essential materials to and from cells.

Functions of Blood

• Transportation: Carries dissolved gases, nutrients, hormones, and metabolic wastes.

• Regulation: Maintains pH and ion composition of interstitial fluids.

• Fluid Loss Prevention: Restricts fluid loss at injury sites.

• Defense Mechanism: Provides defense against toxins and pathogens.

• Temperature Regulation: Stabilizes body temperature.

Blood Composition

• Volume: Approximately 5 liters (5.3 quarts) in the body.

  • 5-6 liters in males, 4-5 liters in females (varies with body size).

• Components:

  • Plasma: Liquid matrix.

  • Formed Elements: Cells and cell fragments.

• Properties:

  • Temperature: ~38°C (100.4°F).

  • Viscosity: 5× more viscous than water due to solid components.

  • pH: Slightly alkaline (average pH 7.4).

Plasma

• Composition resembles interstitial fluid:

  • 92% water

  • 7% plasma proteins

  • 1% other solutes

• Primary Differences between plasma and interstitial fluid:

  • Levels of respiratory gases (O2, CO2).

  • Concentrations of dissolved proteins (stay in blood).

Plasma Proteins

• Present in solution rather than fibers.

• Each 100 mL has approximately 7.6 g of protein (5× that of interstitial fluid).

• Synthesized primarily by the liver (>90%).

• Types of Plasma Proteins:

  • Albumins: 60% of proteins, regulate osmotic pressure.

  • Globulins: 35%; includes immunoglobulins (antibodies for immune response) and transport globulins (bind hormones, minerals, etc.).

  • Fibrinogen: 4%, functions in blood clotting; converts to fibrin strands.

Formed Elements of Blood

• Platelets: Small fragments involved in clotting.

• White Blood Cells (WBCs): Also known as leukocytes, participate in the body's defense mechanisms.

  • Five classes exist, each with specific functions.

• Red Blood Cells (RBCs): Also known as erythrocytes, essential for oxygen transport.

Red Blood Cells (RBCs)

• Characteristics:

  • Lose most organelles including nucleus during development.

  • Cannot repair self, lifespan ~120 days.

  • Contain many hemoglobin molecules (approx. 280 million).

• Function: Primarily carry oxygen,

  • ~98.5% of blood oxygen is bound to hemoglobin; the rest is dissolved in plasma.

Hemoglobin Structure

• Complex quaternary structure with four protein chains (2 alpha, 2 beta).

• Each chain has a single heme pigment that can bind one oxygen molecule.

• Forms of Hemoglobin:

  • Oxyhemoglobin (bright red, bound to O2).

  • Deoxyhemoglobin (dark red, not bound to O2).

Red Blood Cell Production (Erythropoiesis)

• Occurs in red bone marrow (myeloid tissue).

• Developing RBCs absorb amino acids and iron to synthesize hemoglobin.

• Fatty yellow bone marrow can convert to red bone marrow in cases of severe, sustained blood loss.

• Stages of RBC Development:

  • Proerythroblasts

  • Erythroblasts (actively producing Hb)

  • Normoblast (after four days)

  • Reticulocyte : MATURE RBC (80% of mature cell Hb), enters bloodstream after two days, matures in 24 hours.

Erythropoietin (EPO)

• is primarily synthesized by the kidneys in response to low oxygen levels in peripheral tissues (hypoxia).

• It stimulates the stem cells in red bone marrow to produce more red blood cells (RBCs).

Anemia

• A blood disorder characterized by low oxygen-carrying capacity:

  • Iron-deficiency Anemia: Microcytic, hypochromic. Insufficient iron leads to small, less effective RBCs; more common in women.

  • Pernicious Anemia: Macrocytic, normochromic/euchromic. Vitamin B-12 deficiency impacts RBC production.

  • Aplastic Anemia: Injury to bone marrow affects RBC production. Most commonly due to chemo treatments.

  • Sickle Cell Anemia: Genetic mutation in hemoglobin causes sickling of RBCs.

Sickle Cell Disease

• Inherited RBC disorder due to genetic mutation in hemoglobin.

• Sickle-shaped RBCs are fragile and can block blood flow.

• Trait vs. Disorder: One copy of the gene results in the trait; two copies result in the disorder, which also offers increased malaria resistance.

Blood Types

• Determined by presence/absence of surface markers (antigens) on RBCs, predominantly A, B, and Rh systems.

• Blood Type Characteristics:

  • Type A: RBCs have A antigens, plasma contains anti-B antibodies.

  • Type B: RBCs have B antigens, plasma contains anti-A antibodies.

  • Type AB: RBCs have both, plasma has neither antibodies.

  • Type O: RBCs lack both, plasma contains both antibodies.

Hemolytic Disease of the Newborn (HDN)

• Can occur if an Rh– mother carries an Rh+ infant; risks arise due to maternal antibodies attacking fetal RBCs after sensitization.

• Prevention: Administration of anti-Rh antibodies (RhoGAM) during and after delivery.

• RhoGAM works by providing anti-Rh antibodies that help prevent the mother's immune system from attacking the Rh-positive fetal red blood cells, which could lead to complications.

White Blood Cells (Leukocytes)

• Spend little time in circulation, mostly found in tissues near infections.

• Migration Process: Adhere to vessel walls, squeeze through endothelial cells to reach sites of infection (diapedesis).

• Are attracted to chemicals from pathogens, damaged tissues, or other WBCs = Positive chemotaxis

• Types of WBCs:

  There are different types of WBCs categorized into two main groups:

  1. Granular Leukocytes:

     • Neutrophils: Most abundant type, characterized by a multi-lobed nucleus, involved in the phagocytosis of pathogens.

     • Eosinophils: Have a bi-lobed nucleus and are involved in combating multicellular parasites and certain infections.

     • Basophils: Least common, with a bi-lobed nucleus and granules that contain histamine, which plays a role in allergic reactions.

  2. Agranular Leukocytes:

     • Monocytes: Large cells with a kidney-shaped nucleus that differentiate into macrophages and dendritic cells, crucial for phagocytosis and presenting antigens.

     • Lymphocytes: Have a large nucleus and are classified into B-cells (produce antibodies) and T-cells (involved in cell-mediated immunity).

Hemostasis (Blood Clotting)

Hemostasis is the physiological process that prevents and stops bleeding, and it is essential for tissue repair. The process occurs in three main phases:

1. Vascular Phase:

• Smooth Muscle Contraction: Blood vessels constrict (vasoconstriction) to reduce blood flow and limit blood loss following an injury.

• Endothelial Changes: The damaged endothelium (inner lining of blood vessels) becomes more sticky and promotes further aggregation of platelets.

2. Platelet Phase:

• Platelet Activation: Platelets adhere to the exposed collagen fibers of the damaged vessel wall.

• Aggregation: Activated platelets release chemical signals that attract more platelets, forming a temporary 'platelet plug'.

3. Coagulation Phase:

• Conversion of Fibrinogen to Fibrin: This phase involves a series of biochemical reactions that lead to the transformation of fibrinogen (a soluble plasma protein) into fibrin (an insoluble protein), which forms a mesh that stabilizes the platelet plug and creates a solid blood clot.

• Activated Clotting Factors: This phase requires various clotting factors, including thrombin, which is essential for the conversion process.

Understanding Hemostasis Process Steps

The hemostasis process leads to:

• Vascular Spasms: Initial constriction of blood vessels to reduce blood flow.

• Platelet Plug Formation: Formation of a temporary seal at the site of injury.

• Clot Formation: Activation of the clotting cascade results in stable blood clot formation that prevents further blood loss and allows tissue repair to co

Bleeding Disorders

• Bleeding disorders are conditions that affect the blood's ability to clot properly, which can lead to excessive bleeding following injuries or spontaneously. Understanding these disorders is crucial for effective diagnosis and management. Here are some common types of bleeding disorders:

  1. Hemophilia

  • Definition: A genetic disorder where the blood does not clot properly due to the absence or deficiency of clotting factors.

  • Types:

    • Hemophilia A: Caused by a deficiency of factor VIII.

    • Hemophilia B: Caused by a deficiency of factor IX.

  • Symptoms: Patients may experience unexplained or excessive bleeding, frequent bruising, and bleeding around joints and muscles.

  2. Thrombocytopenia

  • Definition: A condition characterized by a low platelet count.

  • Causes: Can be caused by bone marrow disorders, increased platelet destruction (such as in autoimmune diseases), or certain medications.

  • Symptoms: Easy bruising, prolonged bleeding from cuts, petechiae (small red or purple spots on the skin), and bleeding gums.

  3. Von Willebrand Disease

  • Definition: The most common inherited bleeding disorder that affects the blood's ability to clot.

  • Cause: Due to a deficiency in von Willebrand factor, which is essential for platelet adhesion during clot formation.

  • Symptoms: Similar to hemophilia; may include excessive bleeding from cuts, frequent nosebleeds, heavy menstrual periods, and increased bruising.

  4. Vitamin K Deficiency

  • Definition: Vitamin K is vital for synthesizing certain clotting factors. A deficiency can impair the clotting process.

  • Causes: Often occurs due to malabsorption disorders, inadequate dietary intake, or certain medications (like anticoagulants).

  • Symptoms: Increased bleeding tendency, easy bruising, and prolonged bleeding from wounds.

  5. Acquired Bleeding Disorders

  • Definition: These disorders can develop due to other medical conditions or treatments.

  • Examples: Liver disease, which affects the production of clotting factors, and the use of anticoagulants like warfarin or direct oral anticoagulants (DOACs).

  • Symptoms: Vary depending on the underlying cause but may include similar signs such as easy bruising or prolonged bleeding.