Cardiovascular System - Blood and Hemodynamics PDF

Hypertension Summary Definition: Hypertension (high blood pressure) affects about 50 million Americans, leading to heart failure, kidney disease, and stroke. Blood Pressure Categories: ○ Normal: 100 mmHg Types: ○ Primary Hypertension: 90-95% of cases with no...

Hypertension Summary Definition: Hypertension (high blood pressure) affects about 50 million Americans, leading to heart failure, kidney disease, and stroke. Blood Pressure Categories: ○ Normal: 100 mmHg Types: ○ Primary Hypertension: 90-95% of cases with no identifiable cause. ○ Secondary Hypertension: 5-10% with identifiable causes (e.g., kidney disorders, adrenal tumors). Damaging Effects: ○ Blood Vessels: Thickening, atherosclerosis, increased resistance. ○ Heart: Increased workload, myocardial hypertrophy, potential heart failure. ○ Brain: Risk of stroke due to vessel rupture. ○ Kidneys: Damage to arterioles, worsening hypertension. Lifestyle Changes: ○ Weight Loss: Effective in reducing blood pressure. ○ Limit Alcohol: Moderate drinking may lower coronary heart disease risk. ○ Exercise: Regular moderate activity can lower systolic pressure by about 10 mmHg. ○ Reduce Sodium Intake: High-salt diets can worsen hypertension. ○ Maintain Potassium, Calcium, Magnesium: Associated with lower hypertension risk. ○ Quit Smoking: Reduces heart damage. ○ Manage Stress: Techniques like meditation can help lower blood pressure. Drug Treatments: ○ Diuretics: Reduce blood volume by increasing urine output. ○ ACE Inhibitors: Block angiotensin II formation, promote vasodilation. ○ Beta Blockers: Decrease heart rate and renin secretion. ○ Vasodilators: Relax arterial smooth muscle, lowering resistance. ○ Calcium Channel Blockers: Slow calcium entry, reducing heart workload. Medical Terminology (15 Terms) Aneurysm: Bulging blood vessel; risk of rupture. Aortography: X-ray of aorta after dye injection. Carotid Endarterectomy: Removal of plaque from carotid artery. Claudication: Limb pain due to poor circulation. Deep Vein Thrombosis (DVT): Blood clot in deep veins. Doppler Ultrasound: Imaging to measure blood flow.  Femoral Angiography: Imaging of lower limb arteries after contrast injection. Hypotension: Low blood pressure. Normotensive: Normal blood pressure. Occlusion: Blockage of a blood vessel. Orthostatic Hypotension: Blood pressure drop upon standing. Phlebitis: Inflammation of a vein. Thrombectomy: Surgical removal of a blood clot. Thrombophlebitis: Vein inflammation with clot formation. Venipuncture: Puncturing a vein for blood withdrawal. Comprehensive Guide to Blood Vessels 1. Introduction to Blood Vessels Blood vessels form a complex network responsible for transporting blood throughout the body, crucial for maintaining homeostasis. They consist of arteries, arterioles, capillaries, venules, and veins. Each type of blood vessel plays a unique role in circulation, nutrient delivery, and waste removal. 2. Structure of Blood Vessels A. Arteries Function: Carry oxygenated blood away from the heart (except for pulmonary arteries). Structure: 1. Tunica Interna (Intima): Endothelial lining providing a smooth surface to reduce friction. 2. Tunica Media: Thick layer of smooth muscle and elastic fibers for blood pressure regulation. 3. Tunica Externa (Adventitia): Connective tissue for structural support. Types: 1. Elastic Arteries: (e.g., aorta) High elastin content accommodates pressure surges. 2. Muscular Arteries: (e.g., femoral artery) More smooth muscle, allowing for precise control of blood flow. B. Arterioles Function: Small vessels leading to capillaries; regulate blood flow and pressure. Structure: Thinner walls, high smooth muscle content for diameter changes. C. Capillaries Function: Exchange site for oxygen, carbon dioxide, nutrients, and waste.  Structure: Single layer of endothelial cells for diffusion. Types: 1. Continuous Capillaries: Tight junctions; found in muscle and brain. 2. Fenestrated Capillaries: Pores allow larger molecule passage; found in kidneys and intestines. 3. Sinusoidal Capillaries: Large gaps; found in liver and spleen, allowing passage of blood cells and proteins. D. Venules Function: Collect deoxygenated blood from capillaries to transport to veins. Structure: Larger than capillaries, thinner walls, less smooth muscle. E. Veins Function: Carry deoxygenated blood back to the heart. Structure: ○ Thinner walls than arteries, larger lumen for accommodating blood volume. ○ Valves prevent backflow, especially in limbs. 3. Functions of Blood Vessels Transportation: Blood vessels transport oxygen, nutrients, hormones, and waste products. Regulation: Control blood pressure and flow via vasodilation and vasoconstriction. Exchange: Capillaries facilitate gas, nutrient, and waste exchange. Homeostasis: Help maintain body temperature and fluid balance. 4. Blood Flow Regulation A. Autoregulation Tissues regulate their own blood flow based on metabolic needs (e.g., vasodilation during exercise). B. Nervous System Control Sympathetic Nervous System: Activates vasoconstriction, increasing blood pressure. Parasympathetic Nervous System: Promotes vasodilation, decreasing blood pressure. C. Hormonal Control Hormones influencing blood vessel function include: ○ Epinephrine and Norepinephrine: Increase heart rate and cause vasoconstriction. ○ Angiotensin II: A potent vasoconstrictor.  ○ Atrial Natriuretic Peptide (ANP): Promotes vasodilation. 5. Capillary Exchange Mechanisms Diffusion: Movement based on concentration gradients. Transcytosis: Transport of larger molecules via vesicles. Bulk Flow: Net movement of fluids based on hydrostatic and osmotic pressures. A. Starling’s Law of Capillaries Balances fluid movement: ○ Hydrostatic Pressure: Pushes fluid out of capillaries. ○ Osmotic Pressure: Pulls fluid back into capillaries. 6. Hemodynamics A. Blood Pressure The force exerted by circulating blood on vessel walls. Measured using a sphygmomanometer. B. Cardiac Output The volume of blood pumped by the heart per minute: CO=HeartRate×StrokeVolumeCO = Heart Rate \times Stroke VolumeCO=HeartRate×StrokeVolume Hemodynamics: Factors Affecting Blood Flow The velocity of blood flow is inversely related to the cross-sectional area of blood vessels; blood flows slowest where cross-sectional area is greatest. The velocity of blood flow decreases from the aorta to arteries to capillaries and increases in venules and veins. Blood pressure and resistance determine blood flow. Blood flows from regions of higher to lower pressure. The higher the resistance, however, the lower the blood flow. Cardiac output equals the mean arterial pressure divided by total resistance (CO MAP R). Blood pressure is the pressure exerted on the walls of a blood vessel. Factors that affect blood pressure are cardiac output, blood volume, viscosity, resistance, and the elasticity of arteries. As blood leaves the aorta and flows through the systemic circulation, its pressure progressively falls to 0 mmHg by the time it reaches the right ventricle. Resistance depends on blood vessel diameter, blood viscosity, and total blood vessel length.  Venous return depends on pressure differences between the venules and the right ventricle. Blood return to the heart is maintained by several factors, including skeletal muscle contractions, valves in veins (especially in the limbs), and pressure changes associated with breathing. 7. Circulatory Routes A. Systemic Circulation Pathway of oxygenated blood from the left side of the heart to the body and back as deoxygenated blood. B. Pulmonary Circulation Pathway of deoxygenated blood from the right side of the heart to the lungs and back as oxygenated blood. C. Fetal Circulation Definition: Unique circulatory routes in a developing fetus that bypass non-functioning organs (like the lungs) since the fetus receives oxygen through the placenta. Key Structures: 1. Umbilical Vein: Carries oxygenated blood from the placenta to the fetus. 2. Ductus Venosus: Shunts a portion of the umbilical vein blood directly to the inferior vena cava, bypassing the liver. 3. Foramen Ovale: An opening between the right and left atria allowing blood to bypass the non-functioning fetal lungs. 4. Ductus Arteriosus: Connects the pulmonary artery to the aorta, allowing blood to flow directly to the systemic circulation. Development of Fetal Circulation: 1. Gestational Changes: Blood vessels develop from mesodermal tissue through a process known as vasculogenesis. 2. Formation of Major Vessels: Major vessels, including the aorta and pulmonary arteries, are established early in embryonic development. 3. Placental Connection: The placenta provides oxygen and nutrients through the umbilical cord, establishing a vital connection for fetal development. Postnatal Changes: At birth, the circulatory system undergoes significant changes: 1. Umbilical cord clamping stops blood flow from the placenta. 2. Foramen Ovale closure redirects blood flow through the lungs. 3. Ductus Arteriosus constriction becomes a ligament. Control of Blood Pressure and Blood Flow The cardiovascular (CV) center is a group of neurons in the medulla oblongata that regulates heart rate, contractility, and blood vessel diameter. The cardiovascular center receives input from higher brain regions and sensory receptors (baroreceptors and chemoreceptors). Output from the cardiovascular center flows along sympathetic and parasympathetic axons. Sympathetic impulses propagated along cardioaccelerator nerves increase heart rate and contractility; parasympathetic impulses propagated along vagus nerves decrease heart rate. Baroreceptors monitor blood pressure, and chemoreceptors monitor blood levels of O2, CO2, and hydrogen ions. The carotid sinus reflex helps regulate blood pressure in the brain. The aortic reflex regulates general systemic blood pressure. Hormones that help regulate blood pressure are epinephrine, norepinephrine, ADH (antidiuretic hormone), angiotensin II, and ANP (atrial natriuretic peptide). Autoregulation refers to local, automatic adjustments of blood flow in a given region to meet a particular tissue’s need. O2 level is the principal stimulus for autoregulation. Checking Circulation Pulse is the alternate expansion and elastic recoil of an artery wall with each heartbeat. It may be felt in any artery that lies near the surface or over a hard tissue. A normal resting pulse (heart) rate is 70–80 beats/min. Blood pressure is the pressure exerted by blood on the wall of an artery when the left ventricle undergoes systole and then diastole. It is measured by the use of a sphygmomanometer. Systolic blood pressure (SBP) is the arterial blood pressure during ventricular contraction. Diastolic blood pressure (DBP) is the arterial blood pressure during ventricular relaxation. Normal blood pressure is less than 120/80. Pulse pressure is the difference between systolic and diastolic blood pressure. It normally is about 40 mmHg 8. Aging of the Cardiovascular System Effects: Aging leads to structural changes in blood vessels, including: ○ Decreased elasticity and increased stiffness of arteries, leading to higher blood pressure. ○ Increased prevalence of atherosclerosis, narrowing arteries and reducing blood flow. Preventive Measures: A healthy lifestyle, including regular exercise and a balanced diet, can mitigate age-related changes. 9. Clinical Relevance A. Vascular Diseases Atherosclerosis: Fatty plaque buildup in arterial walls, reducing blood flow and increasing heart attack/stroke risk. Hypertension: High blood pressure can lead to heart disease, stroke, and kidney damage. Varicose Veins: Enlarged, twisted veins due to valve failure. B. Diagnostic Procedures Angiography: Imaging to visualize blood vessels for blockages. Doppler Ultrasound: Non-invasive method to evaluate blood flow and detect abnormalities. 10. Conclusion Understanding blood vessels and their functions is essential for comprehending how the circulatory system operates. They play vital roles in transporting blood, regulating flow, facilitating exchange, and maintaining homeostasis. Knowledge of blood vessel structure, function, and development is crucial for recognizing the impact of cardiovascular diseases and the importance of a healthy lifestyle in mitigating age-related changes. 21.1 Structure and Function of Blood Vessels 1. Overview of Blood Vessels Arteries: Carry blood away from the heart. They consist of three layers: ○ Tunica Interna: The inner lining made of endothelial cells. ○ Tunica Media: The middle layer made of smooth muscle and elastic tissue, allowing for elasticity and contractility. ○ Tunica Externa: The outer layer made of connective tissue, providing structural support. Types of Arteries: ○ Elastic Arteries (Conducting): Large arteries (e.g., aorta) that can stretch and recoil. ○ Muscular Arteries (Distributing): Medium-sized arteries that regulate blood flow to various parts of the body. 2. Anastomoses Definition: The joining of the distal ends of two or more vessels. Collateral Circulation: Alternative routes provided by anastomoses, ensuring adequate blood flow even if one route is blocked. End Arteries: Arteries that do not anastomose; blockage can lead to tissue death. 3. Arterioles Function: Small arteries leading to capillaries; regulate blood flow and blood pressure via constriction and dilation. 4. Capillaries Structure: Microscopic vessels facilitating material exchange between blood and tissues. Types: ○ Continuous Capillaries: Have uninterrupted endothelial linings, found in muscles and the brain. ○ Fenestrated Capillaries: Have small pores for enhanced permeability, found in kidneys and endocrine glands. Network: Capillaries form extensive networks to increase surface area for rapid material exchange. 5. Precapillary Sphincters Role: Control blood flow into capillaries based on tissue needs. 6. Sinusoids Definition: Specialized capillaries in the liver with large openings for the passage of larger molecules and cells. 7. Venules and Veins Venules: Small vessels that collect blood from capillaries and merge to form veins. Veins: Have the same three tunics as arteries but are thinner and have a larger lumen. They contain valves to prevent backflow of blood. Varicose Veins: Occur due to weak valves leading to blood pooling. 8. Vascular Sinuses Definition: Thin-walled veins that allow for significant blood volume storage. 9. Blood Reservoirs  Systemic Veins: Serve as reservoirs, particularly in the liver, spleen, and skin, which can shift blood volume into circulation if necessary. 21.2 Capillary Exchange 1. Mechanisms of Exchange Diffusion: Movement of substances from areas of high concentration to low concentration. Transcytosis: Vesicular transport across endothelial cells. Bulk Flow: Movement of water and solutes driven by pressure differences. 2. Hydrostatic and Osmotic Pressures Hydrostatic Pressure: Force exerted by fluid within the capillaries. Osmotic Pressure: Force exerted by proteins in blood plasma that attracts water. 3. Starling’s Law of the Capillaries States that the balance between filtration (fluid leaving the capillary) and reabsorption (fluid entering the capillary) determines fluid movement in and out of capillaries. 4. Edema Definition: Excess accumulation of interstitial fluid due to imbalances in hydrostatic and osmotic pressures. 21.3 Hemodynamics: Factors Affecting Blood Flow 1. Velocity of Blood Flow Relationship with Cross-Sectional Area: Blood flow velocity decreases as the total cross-sectional area increases, meaning it is slowest in capillaries and increases in venules and veins. 2. Determinants of Blood Flow Blood Pressure: The force exerted on blood vessel walls; blood flows from high to low pressure areas. Resistance: The opposition to blood flow, affected by vessel diameter, blood viscosity, and length. 3. Cardiac Output  Formula: CO = MAP / R (where CO is cardiac output, MAP is mean arterial pressure, and R is total resistance). 4. Factors Influencing Blood Pressure Include cardiac output, blood volume, viscosity, resistance, and artery elasticity. 5. Pressure Changes Blood pressure decreases progressively from the aorta to the right ventricle. 6. Venous Return Influencing Factors: Pressure differences, skeletal muscle contractions, venous valves, and respiratory pressure changes. 21.4 Control of Blood Pressure and Blood Flow 1. Cardiovascular Center Located in the medulla oblongata, regulating heart rate, contractility, and vessel diameter. 2. Input and Output Regulation Receives signals from baroreceptors (blood pressure) and chemoreceptors (blood composition) and sends impulses through sympathetic and parasympathetic pathways. 3. Hormonal Regulation Hormones like epinephrine, norepinephrine, ADH, angiotensin II, and ANP help regulate blood pressure. 4. Autoregulation Local adjustments in blood flow based on tissue needs, primarily influenced by oxygen levels. 21.5 Checking Circulation 1. Pulse Measurement  Definition: The rhythmic expansion and recoil of arterial walls; normal resting heart rate is 70-80 beats/min. 2. Blood Pressure Measurement Systolic vs. Diastolic: Measured using a sphygmomanometer; normal is less than 120/80 mmHg. 3. Pulse Pressure Definition: The difference between systolic and diastolic pressures, typically around 40 mmHg. 21.6 Shock and Homeostasis 1. Definition of Shock Inadequate delivery of oxygen and nutrients to meet cellular metabolic needs. 2. Types of Shock Hypovolemic: Due to blood loss. Cardiogenic: Due to heart failure. Vascular: Due to blood vessel issues. Obstructive: Due to obstruction in blood flow. 3. Signs and Symptoms of Shock Low systolic blood pressure (< 90 mmHg), rapid heart rate, cool and clammy skin, altered mental state, and decreased urine output. 21.7 Circulatory Routes 1. Main Circulatory Routes Systemic Circulation: Carries oxygenated blood from the left ventricle to body tissues and returns deoxygenated blood to the right atrium. Pulmonary Circulation: Moves deoxygenated blood from the right ventricle to the lungs and returns oxygenated blood to the left atrium. 2. Subdivisions of Systemic Circulation Coronary Circulation: Supplies blood to the heart muscle.  Hepatic Portal Circulation: Directs blood from digestive organs to the liver for nutrient processing. 3. Fetal Circulation Involves unique pathways for nutrient and gas exchange between the mother and fetus via the placenta. 21.8 Development of Blood Vessels and Blood 1. Origin of Blood Vessels Develop from mesenchymal cells known as hemangioblasts and angioblasts. 2. Blood Cell Formation Blood cells arise from pluripotent stem cells in the yolk sac, liver, and later in bone marrow and thymus. 21.9 Aging and the Cardiovascular System 1. Age-Related Changes Reduced vessel elasticity, smaller cardiac muscle size, lower cardiac output, and increased systolic blood pressure. 2. Increased Risk of Cardiovascular Diseases Higher incidence of conditions such as coronary artery disease, congestive heart failure, and atherosclerosis with aging. Multiple-Choice Questions on Hypertension and Blood Vessels 1. What is the normal blood pressure range? ○ A)