Understanding the Cardiovascular System

Aug 2, 2024

Cardiovascular System Overview

Definition

  • The cardiovascular system is part of the circulatory system that circulates blood.
  • Commonly used interchangeably with the term "circulatory system."

Components of the Cardiovascular System

  • Heart: The pump that moves blood through the vessels.
  • Blood: The fluid that carries oxygen, nutrients, and waste.
  • Blood Vessels: Includes arteries, veins, and capillaries.

Heart Structure

  • Two Sides: Each side contains two chambers.
    • Right Side: Pumps oxygen-poor blood to the lungs (pulmonary circuit).
    • Left Side: Pumps oxygen-rich blood to the body (systemic circuit).
  • Valves: Four valves ensure one-way blood flow:
    • Right atrium → Right ventricle → Pulmonary arteries (oxygen-poor)
    • Left atrium → Left ventricle → Aorta (oxygen-rich)
  • Myocardium: Thick middle layer responsible for heart contractions.
  • Pericardium: Double-walled protective sac enclosing the heart, contains pericardial fluid for lubrication.

Blood Circulation Process

  1. Oxygen-poor blood returns to right atrium.
  2. Pumped to lungs via right ventricle.
  3. Blood picks up oxygen and releases carbon dioxide in lungs.
  4. Oxygen-rich blood returns to left atrium.
  5. Pumped to body tissues via left ventricle.
  6. Unloads oxygen and picks up carbon dioxide, returning to right side to complete the cycle.

Electrical Impulses

  • Contraction initiated by action potentials (electrical impulses).
  • Pacemaker Cells: Generate own electrical stimulation, primarily from the SA node.

Functions of Blood

  • Gas Transport: Transports oxygen and carbon dioxide.
  • Nutrient Supply: Receives nutrients from the digestive system; absorbed in small intestine and passed to the liver.
  • Waste Removal: Filters wastes in kidneys, excreted in urine.
  • Hormone Distribution: Carries hormones from endocrine glands to target organs.
  • Immune Defense: Participates in body’s immune responses.

Blood Composition

  • Plasma: Clear extracellular fluid.
  • Formed Elements:
    • Red Blood Cells: Transport gases.
    • White Blood Cells: Defense mechanisms against invading organisms.
    • Platelets: Blood clotting to minimize blood loss.

Blood Circulation Pathway

  • Closed loop: Blood never leaves vessels; substances diffuse through vessel walls.
  • Arteries: Carry blood away from the heart (usually oxygenated).
  • Veins: Bring blood back to the heart (usually deoxygenated).
  • Capillaries: Smallest vessels for substance exchange.

Vessel Structure

  • Arteries and Veins: Consist of 3 layers:
    • Outer Layer: Loose connective tissue for anchoring.
    • Middle Layer: Smooth muscle for constriction/dilation.
    • Inner Layer: Thin squamous endothelium with a basement membrane.
  • Capillaries: Only consist of thin endothelium and basement membrane for easy diffusion.