Topic 10

Cardiovascular System Overview

  • Closed system of heart and blood vessels.

  • Heart provides the force to pump blood.

  • Blood vessels circulate blood throughout the body.

Functions

  • Deliver oxygen and nutrients to cells and tissues.

  • Remove carbon dioxide and waste products from cells and tissues.

Location of the Heart

  • Located in the thorax, between the lungs in the mediastinum.

  • Orientation: pointed apex directed towards the left hip, base pointing towards the right shoulder.

  • About the size of a human fist.

Anatomy of the Heart

Coverings and Walls of the Heart

  • Pericardium: A double-walled sac enclosing the heart.

    • Fibrous pericardium: Loose and superficial.

    • Serous pericardium: Deep to fibrous pericardium, made up of parietal and visceral layers.

  • Three layers of the heart wall:

    • Epicardium: Visceral pericardium, outer connective tissue layer.

    • Myocardium: Middle layer, composed mostly of cardiac muscle.

    • Endocardium: Inner endothelial lining.

Chambers of the Heart

  • Right Atrium: Receives blood from the body.

  • Right Ventricle: Pumps blood to the lungs.

  • Left Atrium: Receives oxygenated blood from the lungs.

  • Left Ventricle: Pumps oxygenated blood to the body.

  • Interventricular septum: Divides the two ventricles.

  • Interatrial septum: Divides the two atria.

Heart Valves

  • Atrioventricular (AV) valves: Prevent backflow into the atria.

    • Bicuspid (mitral) valve (left side).

    • Tricuspid valve (right side).

  • Semilunar valves: Prevent backflow into the ventricles.

    • Pulmonary semilunar valve.

    • Aortic semilunar valve.

  • Valves open and close due to pressure changes within the heart.

Blood Flow Through the Heart

  1. Blood from the body enters the right atrium via the superior and inferior venae cavae.

  2. Blood flows through the tricuspid valve into the right ventricle.

  3. Blood exits the heart through the pulmonary semilunar valve into the pulmonary trunk, which splits into right and left pulmonary arteries leading to the lungs.

  4. Oxygen-rich blood returns to the left atrium through four pulmonary veins.

  5. Blood flows through the bicuspid valve into the left ventricle.

  6. Blood exits the heart via the aortic semilunar valve into the aorta for distribution to the body.

Circulatory Pathways

  • Pulmonary Circulation: Blood flow from the right heart to the lungs and back to the left heart.

  • Systemic Circulation: Blood flow from the left heart to the body tissues and back to the right heart.

Intrinsic Conduction System of the Heart

  • Controls the basic rhythm of heart contractions.

  • Sinoatrial (SA) Node: The heart's pacemaker.

  • Atrioventricular (AV) Node: Junction of atria and ventricles.

  • AV Bundle (Bundle of His) and Purkinje Fibers: Spread impulses through ventricles, causing contraction.

Cardiac Cycle

  • Consists of one complete heartbeat.

  • Systole: Contraction phase; ventricles eject blood.

  • Diastole: Relaxation phase; heart chambers fill with blood.

Electrocardiogram (ECG)

  • Measures electrical currents generated by heart's impulses.

  • P wave: Atrial depolarization.

  • QRS Complex: Ventricular depolarization.

  • T wave: Ventricular repolarization.

Heart Sounds

  • First sound (lub): Closure of AV valves.

  • Second sound (dup): Closure of semilunar valves.

Regulation of Heart Rate

  • Influenced by various factors:

    • Sympathetic Nervous System: Increases heart rate.

    • Parasympathetic Nervous System: Decreases heart rate.

    • Hormonal influences: Epinephrine increases heart rate.

    • Physical factors: Exercise increases heart rate.

Blood Vessels

  • Arteries: Carry blood away from the heart.

  • Veins: Carry blood back to the heart.

  • Capillaries: Site of exchange between blood and tissues.

Blood Pressure Measurement

  • Measure using a sphygmomanometer.

  • Systolic Pressure: Pressure during ventricular contraction.

  • Diastolic Pressure: Pressure during ventricular relaxation.

Homeostatic Imbalances

  • Hypertension: Elevated blood pressure.

  • Hypotension: Low blood pressure.

  • Atherosclerosis: Buildup of plaque in arteries, leading to increased blood pressure.

Developmental Aspects

  • Early development includes a simple tube heart by week 4.

  • Becomes a four-chambered organ by week 7.

  • Aging impacts cardiovascular health, leading to conditions like varicose veins and arteriosclerosis.