Circulatory System

• Circulatory System:

  • Transport system
  • Link between cells in body and external environment
  • Blood transports substances between cells of all body systems
  • Important in maintaining constant internal environment
• Function of Blood

  • Transport oxygen and nutrients to cells
  • Transport carbon dioxide and other waste products away from cells
  • Transport hormones to cells
  • Maintain pH of body fluids
  • Distribute heat and maintain body temp
  • Maintain water content and ion concentration of body fluids
  • Protect against disease-causing micro-organisms
  • Clotting when vessels are damaged, preventing blood loss
• Components of Blood: Plasma

  • Mixture of water with dissolved substances such as sugar and salt
  • FUNCTION: transport components of blood – cells, nutrients, wastes, hormones, proteins and antibodies throughout body
• Components of Blood: Red Blood Cells (Erythrocytes)

  • Biconcave disks (flattened in the middle on both sides)
  • No nucleus (increases flexibility and SA)
  • Contains haemoglobin which carries oxygen
  • Produced in bone marrow, destroyed in liver and spleen
  • FUNCTION: transport oxygen and carbon dioxide
• Components of Blood: White Blood Cells (Leucocytes)

  • Neutrophils: engulf and digest pathogen
  • Monocytes: engulf pathogens and aged/damaged cells by phagocytosis
  • Basophils: responsible for allergic reactions, defend against parasites and bacteria
  • Eosinophils: inflammatory response, respond to large parasites and worms
• Components of Blood: Platelets (Thrombocytes)

  • Very small, no nucleus
  • Formed in bone marrow, very short life span
  • FUNCTION: adhere to blood vessel lining when injured to form scaffold for coagulation of blood to form clot
• The Heart: Left and Right

  • Left and right separated by septum – allows for separation of oxygenated and deoxygenated blood (allows for maintenance of concentration gradient)
• • Right of heart – collects blood from body and pumps to lungs
• • Left of heart – received blood from lungs and pumps to rest of body
• The Heart: Chambers:

  • 4 chambers – 2 atria, 2 ventricles
  • Atria thinner walls than ventricles
  • Left ventricle thicker walls than right ventricle 
• The Heart Valves:

  • FUNCTION: ensure blood flows in 1 direction
• • Atrioventricular valves: separate atrium and ventricle, preventing backflow.
  • Flaps of thin tissue that attach to heart
  • Prevented from turning inside out by fibrous cords
• • Semilunar valves: separate ventricles and arteries
  • Right = pulmonary artery
  • Left = aorta
  • Cusps press flat against artery when blood flows through
  • When blood tries to flow back cusps fill and seal off artery
• Arteries:

  • Carry blood away from heart
  • Can contract/ relax to control amount of blood flow to an organ
  • Thick muscular, elastic walls
  • No valves
  • Blood pressure increases as ventricles contract and decrease when they relax
  • Pulmonary artery and aorta
• Veins:

  • Carry blood to heart
  • Cannot contract and relax
  • Thin, relatively inelastic walls with little muscle
  • Often have valves to prevent backflow
  • Constant low blood pressure
  • Inferior and superior vena cava, pulmonary vein
• Capillaries:

  • Link between arteries and veins, carries blood close to almost every cell in the body
  • Enables exchange of materials (nutrients and wastes) between cells
  • One cell thick - allows substances to pass easily between blood and surrounding cells