Circulatory System Lecture Notes

Overview

• The lecture is divided into two parts: structure and processes of the circulatory system.
• Importance of understanding structure to comprehend function.
• Two types of circulatory systems: open and closed.

Types of Circulatory Systems

• Open Circulatory System

  • Blood vessels are open-ended allowing blood to leak out among tissues.
  • Example: Insects like grasshoppers.
  • Suitable for small organisms.

• Closed Circulatory System

  • Blood remains within the vessels and heart.
  • Example: Humans, earthworms.
  • Allows for specialization and supports larger organisms.

Human Circulatory System

• Double Circulatory System
  • Blood is pumped twice: once to the lungs (pulmonary) and once to the body (systemic).

Circulatory Circuits

• Systemic Circulation

  • Blood is oxygenated in the lungs, enters the heart, and is delivered to the body.
  • Returns deoxygenated to the heart.

• Pulmonary Circulation

  • Blood moves from the heart to the lungs to be re-oxygenated.
  • Low oxygen and high carbon dioxide levels.

Structure of the Heart

• External Structures

  • Superior Vena Cava: Largest vein, brings blood to the heart.
  • Right Atrium: Upper chamber where blood enters from the body.
  • Coronary Arteries: Supply heart with oxygen and nutrients.
  • Aorta: Largest artery, carries oxygenated blood.
  • Pericardium: Protective membrane reducing friction.

• Internal Structures

  • Right Ventricle: Muscular chamber pumping blood to lungs.
  • Left Ventricle: Thicker, pumps blood against gravity to the body.
  • Septum: Divides left/right heart, prevents mixing of blood.

Layers of the Heart

• Pericardium: Outer protective layer.
• Epicardium: Just inside pericardium.
• Myocardium: Muscular layer.
• Endocardium: Innermost layer.

Blood Vessels

• Arteries

  • Thick, muscular walls, high pressure, narrow lumen.
  • Move blood away from the heart.

• Veins

  • Thinner walls, larger lumen, lower pressure.
  • Move blood back to the heart, contain valves to prevent backflow.

• Capillaries

  • Microscopic, one cell layer thick.
  • Connect arteries to veins, facilitate nutrient and waste exchange.

Terminology Recap

• Closed System: Blood remains within vessels.
• Double Circulation: Blood returns to the heart twice (lungs and body).
• Pulmonary Circulation: Blood to lungs.
• Systemic Circulation: Blood to body.
• Ventricles and Atria: Heart chambers.
• Pericardium: Protective sack.
• Epicardium/Endocardium: Heart layers.
• Tricuspid/Mitral Valves: Separate heart chambers.
• Arteries/Veins/Capillaries: Types of blood vessels.