Cardiovascular+System

Cardiovascular System Overview

  • Components of the Cardiovascular System

    • Heart

    • Arteries

    • Capillaries

    • Veins

Learning Objectives

  • Understand components of the cardiovascular system.

  • Differentiate between arteries and veins.

  • Know the layers of blood vessels and heart.

  • Identify major parts of three layers of arteries and veins.

  • Recognize differences between large, medium, small arteries, and veins.

  • Recall types of capillaries and their locations.

  • Understand metarterioles and arteriovenous anastomoses.

  • Distinguish between Purkinje fibers and normal cardiac myocytes.

Circulatory Routes

  • Pulmonary Circulation

    • Involves arteries delivering deoxygenated blood to the lungs and veins returning oxygenated blood to the heart.

  • Systemic Circulation

    • Involves blood flow from the heart to body tissues and back.

Blood Flow Through the Heart

  • Pathway:

    • Blood enters right atrium from the superior and inferior vena cava.

    • Flows through the tricuspid valve into the right ventricle.

    • Blood is pumped through pulmonary semilunar valve into pulmonary arteries to lungs.

    • After oxygenation, blood returns via pulmonary veins into left atrium.

    • Flows through bicuspid valve into left ventricle.

    • Blood is pumped through aortic semilunar valve into aorta for systemic circulation.

Layers of the Heart

  • Heart Structure:

    • Composed of 4 chambers with major layers:

      • Endocardium:

        • Endothelium and subendocardial connective tissue with Purkinje fibers.

      • Myocardium:

        • Cardiac muscle responsible for heart contractions.

      • Epicardium:

        • Visceral pericardium consisting of connective tissue and simple squamous mesothelium.

        • Contains a subepicardial layer with coronary blood vessels.

Cardiac Valves

  • Function as one-way pathways to control blood flow:

    • Atrioventricular Valves:

      • Tricuspid (right side)

      • Bicuspid (Mitral, left side)

    • Semilunar Valves:

      • Aortic

      • Pulmonary

Conduction System of the Heart

  • Components:

    • SA node (pacemaker)

    • AV node

    • Bundle of His

    • Bundle branches

    • Purkinje fibers, which rapidly conduct impulses to myocardium.

Purkinje Fibers

  • Specialized cardiac muscle cells, larger in size and paler in color compared to typical cardiac myocytes.

  • Conduct impulses faster (4-5 times) due to a richer glycogen content and fewer myofibrils.

Blood Vessel Structure

  • 3 Layers (Tunicas):

    • Tunica Intima:

      • Simple squamous epithelium and underlying loose connective tissue.

    • Tunica Media:

      • Smooth muscle and elastic fibers, responsible for vessel dilation and constriction.

    • Tunica Adventitia:

      • Outermost layer, composed of connective tissue.

Types of Blood Vessels

  • Arteries:

    • Carry blood away from the heart, thicker walls due to a prominent tunica media.

    • Types:

      • Elastic Arteries:

        • Thick walls with high elasticity (e.g., aorta).

      • Muscular Arteries:

        • More smooth muscle (e.g., brachial artery).

      • Arterioles:

        • Smallest arteries, leading to capillary beds.

Types of Capillaries

  • Continuous Capillaries:

    • Found in muscle and nervous tissue, no fenestrations.

  • Fenestrated Capillaries:

    • Found in kidney glomeruli, contain fenestrations.

  • Sinusoidal Capillaries:

    • Wider, more tortuous, allowing larger molecules to pass, found in liver and spleen.

Specialized Structures

  • Metarterioles:

    • Connect arterioles and capillary beds, containing smooth muscle for regulation.

  • Arteriovenous Anastomoses:

    • Direct connections between arterioles and venules, bypassing capillaries.

Veins

  • Structure:

    • Thinner walls than arteries, larger lumina, and have valves to prevent backflow.

  • Features:

    • Tunica intima, tunica media (thinner), and tunica adventitia (thickest layer).

Venules and Their Structure

  • Collect blood from capillaries, initially lack a muscular media.

  • Medium-sized veins have vasa vasorum and valves.

Practice Questions

  • Possible Exam Questions:

    • The tunica adventitia is thickest in which vessels?

    • Function of Purkinje fibers: conduction of electric impulses.

    • What features are prominent in the tunica media of medium/large arteries?

    • Valves of veins are made of:

      • Folds of endothelial cells.