Overview
This lecture focused on key pathophysiology concepts related to blood flow, blood vessel structure, pharmacological interventions, and blood disorders, essential for nursing practice and board exams.
Anatomy of Blood Vessels
- Blood vessels have three layers: tunica adventitia (outer), tunica media (middle, smooth muscle), and tunica intima (inner, contains endothelium).
- Arteries have thicker walls and smaller lumens; veins have thinner walls, larger lumens, and valves to prevent backflow.
- Valves in veins ensure one-way flow toward the heart and prevent backflow; malfunction leads to conditions like varicose veins.
Blood Flow, Pressure, and Resistance
- Blood flows from high pressure to low pressure; highest pressure is in the aorta.
- Contraction of smooth muscle (vasoconstriction) decreases lumen size, increasing resistance and blood pressure.
- Relaxation (vasodilation) increases lumen size, decreasing resistance and lowering blood pressure.
- Formula: Blood flow (Q) = Pressure gradient (ΔP) / Resistance (R).
- Resistance is increased by greater blood viscosity and vessel length; it decreases with increased vessel radius (Poiseuille’s Law).
Clinical Applications & Medications
- Atherosclerosis: Fat deposits (plaque) in arteries decrease blood flow, leading to ischemia and chest pain (angina).
- Nitroglycerin is given for angina to cause vasodilation, increasing blood flow but may lower blood pressure.
- Routes for nitroglycerin: sublingual (quickest), oral, skin patch; enters systemic circulation and targets coronary arteries.
Blood Clots and Vascular Disorders
- Clots (thrombi) in arteries can cause strokes if they travel (emboli); in veins, can cause pulmonary embolism.
- Deep vein thrombosis (DVT) forms in deep leg veins, often due to immobilization; prevention includes mobilization and exercises.
- Thrombophlebitis affects superficial veins; DVT and thrombophlebitis can both lead to emboli if clots dislodge.
Oxygen Transport and Red Blood Cells
- Red blood cells (erythrocytes) transport oxygen using hemoglobin; need iron and vitamin B12 for production.
- Red blood cells are made in red bone marrow, destroyed in the spleen, and iron is recycled.
- Anemia can result from iron deficiency (most common), B12 deficiency (pernicious anemia), or bone marrow failure (aplastic anemia).
Blood Typing and Hypersensitivity
- Type 1 hypersensitivity (immediate): IgE-mediated, involves mast cells, releases histamine causing vasodilation and allergy symptoms.
- Type 2 hypersensitivity (cytotoxic): Antibody-mediated, responsible for conditions like hemolytic disease of the newborn and transfusion reactions.
- Hemolytic disease of the newborn occurs when an Rh-negative mother develops antibodies against an Rh-positive fetus, affecting subsequent pregnancies.
Key Terms & Definitions
- Tunica intima — innermost vessel layer containing endothelium.
- Vasoconstriction — narrowing of vessel lumen due to smooth muscle contraction.
- Vasodilation — widening of vessel lumen due to smooth muscle relaxation.
- Atherosclerosis — fat (plaque) buildup in arterial walls.
- Ischemia — inadequate blood supply to tissue.
- Nitroglycerin — medication for angina, causes vasodilation.
- Thrombus — stationary blood clot.
- Embolus — travelling blood clot.
- DVT (Deep Vein Thrombosis) — clot in a deep vein.
- Erythrocyte — red blood cell.
- Pernicious anemia — anemia from vitamin B12 deficiency.
- Aplastic anemia — deficiency of all blood cells due to bone marrow failure.
- Poiseuille’s Law — resistance = (8ηL)/(πr⁴) where η = viscosity, L = length, r = radius.
- Hemolytic disease of the newborn — destruction of fetal RBCs by maternal antibodies.
Action Items / Next Steps
- Review textbook chapters 10, 11, 13, 14, and 15.
- Memorize and understand blood flow formulas and Poiseuille’s Law.
- Study clinical implications of vascular disorders and related pharmacology.
- Prepare for upcoming quiz; focus on key terms and blood vessel anatomy.
- Watch relevant recorded teach-back videos for clarification.