Blood

Functions of Blood

• Transport: Delivers oxygen, nutrients, hormones, and removes waste products.

• Regulation: Maintains body temperature, pH, and fluid balance.

• Protection: Involves immune responses and clotting to prevent blood loss.

Components of Blood

• Plasma: Liquid matrix containing water, proteins (albumin, globulins, fibrinogen), nutrients, hormones, and waste.

• Formed Elements: Red blood cells (RBCs), white blood cells (WBCs), and platelets.

• Major Proteins: Albumin (osmotic pressure, transport), Globulins (immune function), Fibrinogen (clotting). Most are produced in the liver.

Red Blood Cells (RBCs) vs. White Blood Cells (WBCs)

• RBCs: No nucleus or organelles; specialized for oxygen transport via hemoglobin.

• WBCs: Have nuclei and organelles; function in immune defense.

Hematocrit and Differential

• Hematocrit: Percentage of blood volume occupied by RBCs.

• Differential: Measures the proportion of different types of WBCs.

Hematopoiesis

• Definition: Formation of all blood cells from hematopoietic stem cells in red bone marrow.

• Erythropoiesis: Production of RBCs; triggered by hypoxia (low oxygen).

• Leukopoiesis: Production of WBCs.

Reticulocytes

• Definition: Immature RBCs found in blood; high numbers indicate increased RBC production.

Hemoglobin Structure

• Composed of four globin chains, each with a heme group containing an iron (Fe2+) atom that binds oxygen.

RBC Recycling

• RBCs are broken down in the spleen and liver.

• Transferrin: Transports iron to bone marrow for reuse.

• Heme is converted to bilirubin and excreted by the liver.

Erythropoietin (EPO)

• Hormone produced by kidneys; stimulates erythropoiesis in response to hypoxia.

Leukopenia & Leukemia

• Leukopenia: Low WBC count.

• Leukemia: Cancer of WBC-forming tissues; abnormal proliferation of WBCs.

Platelets and Megakaryocytes

• Megakaryocytes: Large bone marrow cells that fragment to form platelets.

• Platelets: Cell fragments involved in clotting; originate from megakaryocytes.

Granulocytes and Agranulocytes

• Granulocytes: Neutrophils (most prevalent; phagocytosis), Eosinophils (combat parasites, allergies), Basophils (release histamine).

• Agranulocytes: Lymphocytes (B and T cells; adaptive immunity), Monocytes (become macrophages; phagocytosis).

Hemostasis and Clotting

• Hemostasis: Stoppage of bleeding; involves vascular spasm, platelet plug formation, and coagulation.

• Clotting: Cascade of reactions requiring calcium ions (Ca2+).

• Thrombus: Clot in an unbroken vessel; Embolus: Clot that travels in the bloodstream.

Blood Groups

• ABO System: Based on antigens (A, B) on RBCs.

• Rh Factor: Presence (+) or absence (−) of D antigen.

Heart

Heart Structure

• Papillary Muscles & Chordae Tendineae: Prevent valve prolapse during contraction.

• Valves: Atrioventricular (AV) valves (tricuspid, bicuspid/mitral) and semilunar valves (pulmonary, aortic); ensure unidirectional blood flow.

Circulation Pathways

• Systemic Circulation: Left heart pumps oxygenated blood to body.

• Pulmonary Circulation: Right heart pumps deoxygenated blood to lungs.

Cardiomyocyte Structure

• Heart muscle cells with intercalated discs for synchronized contraction.

Cardiac Conduction System

• Pathway: SA node → AV node → Bundle of His → Bundle branches → Purkinje fibers.

• SA Node: Pacemaker; generates autorhythmic action potentials.

Action Potentials in the Heart

• Phases: Depolarization (Na+ influx), Plateau (Ca2+ influx), Repolarization (K+ efflux).

• Plateau Phase: Prolongs contraction to ensure efficient pumping.

Electrocardiogram (EKG/ECG)

• P wave: Atrial depolarization.

• QRS complex: Ventricular depolarization.

• T wave: Ventricular repolarization.

Cardiac Cycle and Heart Sounds

• Systole: Contraction phase; Diastole: Relaxation phase.

• EDV (End-Diastolic Volume): Volume in ventricle at end of filling.

• ESV (End-Systolic Volume): Volume after contraction.

• S1: Closure of AV valves; S2: Closure of semilunar valves.

• Isovolumetric Contraction: All valves closed; pressure rises but volume unchanged.

Cardiac Output (CO) and Stroke Volume (SV)

• CO: Volume of blood pumped per minute;

• Normal CO ≈ 5 L/min.

• SV: Volume ejected per beat; regulated by preload (stretch), afterload (resistance), and contractility.

• Frank-Starling Law: Greater ventricular stretch (preload) increases SV.

Cardiac Pathology Terms

• Myocardial Infarction (MI): Heart attack; tissue death from blocked blood supply.

• Ischemia: Reduced blood flow.

• Hypoxia: Low oxygen in tissues.

• Infarct: Area of dead tissue.

• Angina: Chest pain from temporary ischemia.

Cardiovascular: Vessels

Capillary Filtration and Resorption

• Blood Hydrostatic Pressure (BHP): Pushes fluid out of capillaries; highest at arterial end.

• Blood Colloid Osmotic Pressure (BCOP): Pulls fluid into capillaries; due to plasma proteins.

• Interstitial Fluid Hydrostatic Pressure (IFHP): Normally zero; increases if lymphatics are blocked, causing edema.

Starling's Law of Capillaries

• Fluid movement is determined by the balance of hydrostatic and osmotic pressures.

• Net Filtration Pressure (NFP):

• At arterial end: NFP is positive (filtration); at venous end: NFP is negative (reabsorption).

• About 15% of filtered fluid enters lymphatics; blockage leads to edema.

Edema

• Excess fluid in tissues; caused by increased filtration, decreased reabsorption, or lymphatic obstruction.

Vascular Resistance (SVR)

• Opposition to blood flow; depends on blood viscosity, vessel length, and vessel diameter.

Hormonal Regulation

• ADH (Antidiuretic Hormone): Increases water reabsorption; loss leads to decreased blood volume and CO.

• Aldosterone: Increases sodium and water retention.

Capillary Structure and Types

• Continuous: Most common; tight junctions.

• Fenestrated: Pores for increased permeability (kidneys, intestines).

• Sinusoidal: Large gaps (liver, spleen).

Arterioles and Blood Pressure Regulation

• Arterioles regulate resistance and blood pressure via vasoconstriction/dilation.

• Precapillary sphincters control blood flow into capillary beds.

Relationship: BP, SVR, and CO

• Blood Pressure (BP) is determined by cardiac output (CO) and systemic vascular resistance (SVR):

Immunity

Immune Organs

• Spleen: Filters blood, recycles RBCs, immune surveillance.

• Lymph Nodes: Filter lymph, house lymphocytes.

Non-Specific (Innate) Resistance

• Physical Barriers: Skin, mucous membranes.

• Chemical Barriers: Lysozyme (tears, saliva), acidic pH, interferons, complement proteins.

• Physiological Responses: Inflammation, fever, phagocytosis, urination, defecation.

Phagocytosis and Complement System

• Phagocytosis: Engulfment and destruction of pathogens by neutrophils and macrophages.

• Complement System: Plasma proteins that enhance phagocytosis (opsonization), lyse pathogens, and promote inflammation.

Inflammation

• Redness, heat, swelling, pain; increases blood flow and recruits immune cells.

• Chemotaxis: Movement of immune cells toward chemical signals at infection sites.

Lymph and Lymphatic System

• Lymph: Fluid collected from tissues; returned to blood via lymphatic vessels.

• Lymph Node Structure: Cortex (lymphocytes), medulla (macrophages).

• Thoracic Duct: Drains lymph into left subclavian vein.

Specific (Adaptive) Immunity

• Characteristics: Specificity (targets specific antigens), memory (faster response upon re-exposure).

• Cell-Mediated Immunity: T cells (Tc: cytotoxic, Th: helper) attack infected cells.

• Humoral Immunity: B cells differentiate into plasma cells, produce antibodies.

• Antigen-Presenting Cells (APCs): Present antigens to T cells (e.g., dendritic cells, macrophages).

• NK Cells: Destroy abnormal cells non-specifically.

Antigens and Antibodies

• Antigen: Substance that triggers immune response.

• Antibody: Protein produced by B cells; binds antigens, neutralizes pathogens, promotes phagocytosis.

• Antibody Classes: IgG (blood), IgA (mucosa), IgM (first response), IgE (allergy), IgD (B cell receptor).

Case Study: Left Ventricular Failure (LVF)

Pathophysiology and Symptoms

• Reduced Cardiac Output: LVF decreases blood pumped to body, causing pale, cold skin (vasoconstriction, poor perfusion).

• Pulmonary Congestion: Blood backs up into lungs, causing fluid accumulation (rales/moist sounds).

• Mechanism: Increased pulmonary capillary pressure leads to fluid leakage into alveoli (pulmonary edema).

Summary Table: Blood Cell Types and Functions

Summary Table: Capillary Exchange Pressures

Additional info: Academic context and explanations have been expanded for clarity and completeness. Equations are provided in LaTeX format as required.