The Circulatory System

The Circulatory System

Heart Structures and Functions

  • The heart is a double pump that drives the blood flow around two separate circuits in the body.
  • The right side of the heart pumps deoxygenated blood to the lungs where it picks up oxygen and releases carbon dioxide. This is known as the pulmonary circulation.
  • The left side of the heart pumps oxygenated blood to all other parts of the body, supplying the body cells with the oxygen they need for respiration. This is called systemic circulation.
  • The heart is mainly composed of cardiac muscle and it contracts and relaxes rhythmically to pump blood.
  • Blood exits the heart through large arteries: the pulmonary artery and the aorta.
  • Blood enters the heart through the pulmonary veins and the vena cava.

Blood Vessels

  • The arteries carry blood away from the heart. They have thick, elastic walls to withstand high pressure of blood.
  • Veins carry blood back to the heart. They have thinner walls due to lower pressure and wider lumens to hold more blood.
  • Capillaries are microscopic vessels that deliver oxygen and nutrients to body cells and remove waste. They have one-cell thick walls to allow rapid exchange of substances.

Blood and Its Components

  • The human blood is a form of connective tissue. It is composed of blood plasma and blood cells.
  • Red blood cells (RBCs) are responsible for carrying oxygen. They contain a red pigment called haemoglobin that binds to oxygen.
  • White blood cells (WBCs) are involved in immune response. They help protect against infection by producing antibodies or by engulfing and digesting pathogens.
  • Platelets are fragments of cells that play a vital role in blood clotting, preventing loss of blood from wounds.
  • Blood plasma is a yellowish liquid carrying dissolved glucose, amino acids, mineral ions, hormones, and waste substances.

The Role of Blood in Transport

  • The blood plays a vital role in the transport of materials around the body. This includes transport of oxygen from lungs to body cells, carbon dioxide from cells to lungs, nutrients from digestive system to cells, urea from liver to kidneys, and hormones.

Remember to keep in mind how these elements of the circulatory system interact to contribute to its overall function. Understanding the individual roles and function of the heart, blood vessels and blood components will provide a robust knowledge of the circulatory system.