Cardiovascular System Overview

Major Functions of the Cardiovascular System

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

• Protection: Circulates immune cells and antibodies to defend against pathogens.

• Regulation: Maintains homeostasis of temperature, pH, and fluid balance.

Blood (Martini Chapter 19)

Blood Composition and Functions

• Formed Elements: Includes erythrocytes (RBCs), leukocytes (WBCs), and thrombocytes (platelets).

• Plasma: The liquid matrix of blood, containing water, electrolytes, nutrients, hormones, and waste products.

• Plasma Proteins: Albumins (osmotic pressure), globulins (immunity), and fibrinogen (clotting).

Microscopic Identification and Comparison of Blood Cells

• Erythrocytes (RBCs): Biconcave, anucleate, 4.2–6.2 million/μL.

• Leukocytes (WBCs): Five types:

  • Neutrophils: Multilobed nucleus, phagocytic.

  • Lymphocytes: Large nucleus, adaptive immunity.

  • Monocytes: Kidney-shaped nucleus, become macrophages.

  • Eosinophils: Bilobed nucleus, combat parasites.

  • Basophils: Large granules, release histamine.

• Thrombocytes (Platelets): Small cell fragments, 150,000–400,000/μL, involved in clotting.

Hemopoiesis (Blood Cell Formation)

• Location: Red bone marrow (myeloid tissue), lymphoid tissues.

• Key Cells: Hemocytoblasts (stem cells), reticulocytes (immature RBCs), megakaryocytes (platelet precursors).

• Regulatory Hormones: Erythropoietin (stimulates RBCs), colony stimulating factors (WBCs).

Common Blood Tests

• Hematocrit: Percentage of RBCs in blood.

• Differential Count: Proportion of each WBC type.

• RBC and WBC Count: Number per microliter.

• Hemoglobin Concentration: Amount of hemoglobin in blood.

• Coagulation Time: Time required for blood to clot.

Red Blood Cell Structure and Function

• Biconcave Shape: Increases surface area for gas exchange and flexibility.

• Lack of Nucleus: Maximizes space for hemoglobin.

Hemoglobin Structure and Related Terms

• Structure: Four polypeptide chains, each with a heme group binding one O2.

• Oxyhemoglobin: Hemoglobin bound to oxygen.

• Deoxyhemoglobin: Hemoglobin without oxygen.

• Carbaminohemoglobin: Hemoglobin bound to CO2.

RBC Breakdown and Recycling

• Location: Spleen, liver, bone marrow.

• Products: Heme → bilirubin (excreted in bile); iron recycled; globin → amino acids.

Blood Typing: ABO and Rh Systems

• Surface Antigens: Determine blood type (A, B, AB, O).

• Antibodies: Present in plasma, react with foreign antigens.

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

Blood Transfusion Compatibility

• Compatible Types: Determined by absence of recipient antibodies against donor antigens.

• Transfusion Reaction: Agglutination and hemolysis if incompatible blood is transfused.

Hemostasis and Coagulation

• Three Phases: Vascular spasm, platelet plug formation, coagulation.

• Coagulation Pathways:

  • Intrinsic Pathway: Initiated by damage inside vessel.

  • Extrinsic Pathway: Initiated by external trauma.

  • Common Pathway: Both converge to activate Factor X, leading to thrombin and fibrin formation.

• Fibrinolysis: Plasmin dissolves the clot.

The Heart (Martini Chapter 20)

Heart Anatomy and Position

• Pericardium: Double-layered sac (parietal and visceral layers).

• Chambers: Two atria (receiving), two ventricles (pumping).

• Valves: Tricuspid (right AV), bicuspid/mitral (left AV), pulmonary, aortic.

• Other Structures: Chordae tendineae, papillary muscles, interventricular septum.

• Heart Wall Layers: Epicardium (outer), myocardium (muscle), endocardium (inner).

• Coronary Arteries: Right coronary, marginal, posterior interventricular, left coronary, anterior interventricular, circumflex.

• Cardiac Veins: Great cardiac, middle cardiac, coronary sinus.

Cardiac Cycle Events

• Diastole: Chambers relax and fill with blood.

• Systole: Chambers contract and eject blood.

• Valve Actions: Opening and closing produce heart sounds ("lub-dub").

• Volume and Pressure Changes: Drive blood flow through the heart.

Blood Flow Through the Heart

• Right atrium → tricuspid valve → right ventricle → pulmonary valve → pulmonary trunk → lungs → pulmonary veins → left atrium → bicuspid/mitral valve → left ventricle → aortic valve → aorta → systemic circulation.

Cardiac Conduction System and ECG

• Automaticity: Heart's ability to generate its own impulses.

• Conduction System: SA node, AV node, bundle of His, bundle branches, Purkinje fibers.

• ECG Components: P wave (atrial depolarization), QRS complex (ventricular depolarization), T wave (ventricular repolarization), PR interval, QT interval.

Relationship of ECG to Cardiac Cycle

• Electrical events (seen on ECG) precede mechanical events (contraction/relaxation) in the cardiac cycle.

Cardiac Output and Influencing Factors

• Cardiac Output (CO): Volume of blood pumped per minute.

  • Formula:

• Cardiac Reserve: Difference between resting and maximal CO.

• Influencing Factors: Stroke volume, heart rate, venous return, end systolic volume (ESV), end diastolic volume (EDV), fill time, preload, afterload, contractility.

Chemical Influences on Cardiac Output

• Natriuretic Peptides: Decrease blood volume and pressure.

• Epinephrine/Norepinephrine: Increase heart rate and contractility.

• Acetylcholine: Decreases heart rate.

Blood Vessels and Circulation (Martini Chapter 21)

Blood Vessel Types and Structure

• Arteries: Carry blood away from the heart.

  • Elastic Arteries: Large, stretch to accommodate pressure.

  • Muscular Arteries: Distribute blood to organs.

  • Arterioles: Smallest, regulate flow into capillaries.

• Capillaries: Site of exchange.

  • Continuous: Most common, tight junctions.

  • Fenestrated: Pores for increased permeability.

  • Sinusoid: Large gaps, found in liver, spleen.

• Veins: Return blood to the heart.

  • Venules: Smallest veins.

  • Medium Veins: Contain valves.

  • Large Veins: Superior/inferior vena cava.

Capillary Exchange and Pressures

• Osmotic Pressure: Pulls fluid into capillaries.

• Hydrostatic Pressure: Pushes fluid out of capillaries.

• Net Filtration Pressure: Determines direction of fluid movement.

Control of Blood Flow

• Local Autoregulation: Tissues regulate their own blood flow.

• Neural Mechanisms: Baroreceptor and chemoreceptor reflexes, sympathetic stimulation.

• Hormonal Mechanisms: Hormones adjust vessel diameter and blood volume.

Homeostatic Responses to Circulatory Changes

• Hemorrhaging: Vasoconstriction, increased heart rate, fluid retention.

• Anaphylactic Shock: Widespread vasodilation, drop in blood pressure.

• Exercise: Increased cardiac output, redistribution of blood flow.

Pulmonary and Systemic Circuits

• Pulmonary Circuit: Right ventricle → lungs → left atrium.

• Systemic Circuit: Left ventricle → body → right atrium.

• Major Vessels: Pulmonary trunk, arteries, veins (pulmonary); aorta, vena cavae, and named arteries/veins (systemic).

Major Arteries and Veins of the Systemic Circuit

Fetal vs. Adult Circulation

• Fetal Circulation: Includes foramen ovale, ductus arteriosus, ductus venosus for bypassing nonfunctional lungs/liver.

• Adult Circulation: These shunts close after birth.

Hepatic Portal Circulation

• Definition: Blood from digestive organs passes through the liver before returning to the heart.

• Significance: Allows processing and detoxification of absorbed substances.

Venous Reserve and Anastomoses

• Venous Reserve: Extra blood in veins that can be mobilized during blood loss.

• Anastomoses: Connections between blood vessels providing alternate routes for blood flow.

Hemodynamics: Blood Flow, Pressure, and Resistance

• Blood Flow: Volume of blood moving through a vessel per unit time.

• Blood Pressure: Force exerted by blood on vessel walls.

• Blood Velocity: Speed of blood flow.

• Vasodilation: Widening of blood vessels, decreases resistance.

• Vasoconstriction: Narrowing of blood vessels, increases resistance.

• Peripheral Resistance: Opposition to flow, mainly in arterioles.

• Relationship: (Flow = Pressure difference / Resistance)

Blood Pressure Measurement and Calculations

• Systolic Pressure: Peak pressure during ventricular contraction.

• Diastolic Pressure: Lowest pressure during ventricular relaxation.

• Pulse Pressure:

• Mean Arterial Pressure (MAP):

Example:

If blood pressure is 120/80 mmHg: Pulse Pressure = 120 - 80 = 40 mmHg MAP = 80 + (1/3) × 40 = 93 mmHg

Additional info: This guide expands on the listed outcomes with definitions, examples, and formulas for comprehensive exam preparation.