Cardiovascular System Overview

• Definition: The cardiovascular system is responsible for moving blood, nutrients, and oxygen throughout the body.
• Components:
  • Circulatory Fluid: Blood is a major component.
  • Blood Vessels: Includes arteries, veins, and capillaries.
  • Muscular Pump: Heart

Types of Circulatory Systems

• Open Circulatory System:

  • Definition: No blood vessels; circulatory fluid (hemolymph) bathes organs directly.
  • Example Organisms: Many invertebrates rely on diffusion to distribute nutrients and oxygen.
  • Energy Efficiency: Requires less energy to operate since fluid is not pumped through vessels.

• Closed Circulatory System:

  • Definition: Blood is contained within vessels.
  • Example: Humans have a closed circulatory system with arteries and veins.
  • Energy Requirement: More energy-intensive due to the need for a muscular heart to pump blood.

Differences between Arteries and Veins

• Arteries:

  • Carry oxygenated blood away from the heart (except pulmonary arteries, which carry deoxygenated blood to the lungs).
  • Thick, elastic walls to handle high pressure.
  • Example: Aorta, Pulmonary artery.

• Veins:

  • Usually carry deoxygenated blood back to the heart (except pulmonary veins, which carry oxygenated blood from the lungs).
  • Thinner walls and lower pressure compared to arteries.
  • Contain valves to prevent backflow.

Human Heart Structure

• Chambers: Human heart has four chambers.

  • Atria: Upper chambers (right and left atrium). Receive blood.
  • Ventricles: Lower chambers (right and left ventricle). Pump blood out.

• Blood Flow:

  1. Deoxygenated blood returns to the right atrium via the inferior and superior vena cava.
  2. Blood moves to the right ventricle and is pumped to the lungs via the pulmonary artery.
  3. Oxygenated blood returns to the left atrium from the lungs through pulmonary veins.
  4. Blood moves to the left ventricle and is pumped out to the body via the aorta.

• Valves:

  • Atrioventricular (AV) Valves: Separate atria and ventricles (tricuspid and bicuspid).
  • Semilunar Valves: Between ventricles and arteries (pulmonary and aortic).

Double Circulation in Humans

• Definition: Two separate circuits for blood flow: one for oxygen-poor blood to the lungs and one for oxygen-rich blood to the rest of the body.
• Major Points:
  • Oxygen-poor blood enters the right atrium ➔ right ventricle ➔ lungs (oxygenated).
  • Oxygen-rich blood returns to the left atrium ➔ left ventricle ➔ body.

Cardiac Cycle and Blood Pressure

• Systole: Contraction of the heart (blood is pumped out).

  • Systolic Pressure: Higher number in blood pressure readings (e.g., 120).

• Diastole: Relaxation of the heart (heart fills with blood).

  • Diastolic Pressure: Lower number in blood pressure readings (e.g., 80).

Cardiac Output and Heart Rate

• Cardiac Output: Volume of blood pumped by the heart.
  • Factors influencing cardiac output:
  • Heart Rate: Number of beats per minute.
  • Stroke Volume: Volume of blood pumped per contraction.

Heart Sounds and Murmurs

• Heart Sounds:
  • “Lub-Dub”: Sounds produced by closure of heart valves during the cardiac cycle.
  • Lub: Closure of AV valves; Dub: Closure of semilunar valves.
• Heart Murmurs: Abnormal sounds caused by turbulent blood flow due to leaky valves.

Differences in Blood Vessels

• Arteries: Thick walls due to high pressure; designed to handle pulsatile flow.
• Veins: Thinner walls; designed for lower pressure; contain valves to prevent backflow.
• Varicose Veins: Caused by weakened valves in veins, leading to blood pooling.