The circulatory system

Summary

The circulatory system in mammals consists of the heart, blood, and blood vessels, facilitating the transport of oxygen and nutrients throughout the body. It includes both systemic and pulmonary circulations, with blood vessels like arteries, veins, and capillaries playing distinct roles. Water is crucial in circulation as it forms the majority of blood and tissue fluid, aiding in transport and temperature regulation.

• Circulatory System — a network of the heart, blood, and blood vessels transporting blood throughout the body.
  Example: Human circulatory system is closed and double, involving systemic and pulmonary circuits.
• Blood Vessels — tubes that carry blood throughout the body, including arteries, veins, and capillaries.
  Example: Arteries carry oxygenated blood at high pressure, while veins carry deoxygenated blood at low pressure.
• Red Blood Cells — cells in the blood that carry oxygen using hemoglobin.
  Example: Erythrocytes have a biconcave shape and lack a nucleus.
• Tissue Fluid — fluid that leaks out of capillaries to surround cells, facilitating exchange of nutrients and waste.
  Example: Tissue fluid forms when plasma seeps into spaces between cells.
• Lymphatic System — a network of vessels that helps in drainage, immunity, and digestion.
  Example: Lymphatics transport lymph to the subclavian vein.

Exam Tips

Key Definitions to Remember

• Circulatory System: Network of heart, blood, and vessels.
• Blood Vessels: Arteries, veins, and capillaries transporting blood.
• Red Blood Cells: Oxygen-carrying cells with hemoglobin.
• Tissue Fluid: Plasma that leaks out of capillaries.
• Lymphatic System: Vessels aiding in drainage and immunity.

Common Confusions

• Difference between open and closed circulatory systems.
• Functions of systemic vs. pulmonary circulation.

Typical Exam Questions

• What is the order of blood flow through the vessels?
  Artery → arterioles → capillaries → venules → veins
• What features of arteries resist blood pressure changes?
  Thick elastic layer and muscle in the artery wall
• What are the structures labeled X and Y in a microscope image?
  Identify based on features like cell shape and wall thickness

What Examiners Usually Test

• Understanding of blood vessel structure and function
• Ability to identify blood cells and vessels in images
• Explanation of the role of water in circulation