cardiovascular system

Cardiovascular System Overview

• The cardiovascular system consists of arteries, arterioles, capillaries, venules, and veins that enable blood circulation throughout the body.

• Blood pressure is critically regulated as blood flows from high-pressure arteries to lower-pressure veins.

Arteries vs Veins

• Arteries:

  • Thick, muscular walls capable of withstanding high pressure.

  • Smaller lumen compared to veins, allowing for efficient control of blood flow.

  • Generally transport oxygenated blood, except for pulmonary arteries (which carry deoxygenated blood).

• Veins:

  • Thinner walls with larger lumen and lower pressure compared to arteries.

  • Return deoxygenated blood to the heart, except for pulmonary veins (which carry oxygenated blood).

  • Blood pressure in veins approaches zero as blood returns to the heart.

Blood Components

• Red Blood Cells (Erythrocytes):

  • Transport oxygen to tissues and carbon dioxide back to lungs.

• White Blood Cells (Leukocytes):

  • Involved in the immune response.

• Platelets:

  • Play a crucial role in blood clotting to repair damaged blood vessels.

• Plasma:

  • Makes up about 55% of blood and is primarily composed of water, proteins, nutrients, hormones, and waste products.

Blood Flow Dynamics

• Blood flow through the body follows a closed loop: artery ➔ arterioles ➔ capillaries ➔ venules ➔ veins & back to heart.

• Importantly, oxygen is exchanged for carbon dioxide during circulation in tissue capillaries, while the reverse occurs in pulmonary capillaries.

Gas Exchange and Cellular Respiration

• Aerobic Respiration:

  • Uses oxygen to generate ATP (energy), producing approximately 36 ATP from glucose.

• Anaerobic Respiration:

  • Occurs without oxygen, yielding only 2 ATP and producing byproducts like lactic acid that can adversely affect pH levels (making it more acidic).

Heart Anatomy and Function

• The heart is enclosed in a pericardial sac that facilitates movement and protects it from friction.

• Chambers of the Heart:

  • Right atrium, right ventricle, left atrium, left ventricle.

• The heart functions via four valves:

  • Atrioventricular (AV) Valves: Control blood flow between atria and ventricles.

    • Tricuspid Valve (right AV valve)

    • Bicuspid/Mitral Valve (left AV valve)

  • Semilunar Valves: Prevent backflow into ventricles from the aorta and pulmonary trunk.

Cardiac Electrical Activity

• The heart has its own electrical conduction system:

  • Sinoatrial Node (SA Node): The primary pacemaker initiates the heartbeat by generating electrical impulses (60–100 beats per minute).

  • Atrioventricular Node (AV Node): Controls the timing of the conduction to the ventricles.

  • Other pacemaker cells can take over if the SA node fails but operate at a lower frequency (40-60 bp).

Importance of Blood Supply

• Ensuring oxygen reaches tissues is vital for metabolic activities; if tissues do not receive sufficient oxygen, cells may die.

• Blockages in coronary arteries lead to inadequate blood flow, resulting in ischemia or heart attacks, often identified via an EKG.

Coronary Circulation

• The heart is supplied with blood from the left and right coronary arteries, branches from the aorta.

• A blockage, particularly in the Left Anterior Descending artery, can cause significant issues as it supplies crucial heart muscle.

• Procedures like stenting are common interventions to maintain blood flow in clogged coronary arteries.

Regulation of Blood Flow

• Blood flow adjusts based on metabolic needs (e.g., increased during exercise, decreased at rest).

• The cardiovascular system maintains adequate perfusion and oxygenation to all tissues, adapting to various physiological demands.

• Valve function ensures unidirectional blood flow which is crucial for effective circulation.