CIRCULATORY SYSTEM

• Circulatory systems

  • Fluid (blood or hemolymph) that transports materials
  • System of blood vessels
  • A heart to pump the fluid through the vessels
• If your diet is poor in iron, you will make fewer RBCs because there is less iron to make hemoglobin
• Closed system


  • Vertebrates, annelid worms, and a few mollusks
• Hemoglobin


  • Complex protein made up of four protein strands, plus iron-rich heme groups
  • Each hemoglobin molecule can carry four oxygen atoms
  • Presence of oxygen turns hemoglobin bright red
• Thrombin converts the protein fibrinogen into sticky fibrin, which binds the clot
• Red blood cells

  • RBCs lose their nucleus at maturity
  • Make up about 99% of the blood’s cellular component
  • Red color is due to hemoglobin
• Circulatory system


  • Transporting gases, nutrients, wastes, and hormones
• The hormone erythropoietin, made by the kidneys, stimulates the production of RBCs in red bone marrow
• Open system

  • Arthropods and most mollusks
• Platelets


  • Cell fragments used in blood clotting
  • Derived from megakaryocytes
  • Aggregate at the site of a wound
  • Release chemicals to stimulate thrombin production
• Blood Vessels


  • Classes of blood vessels fall into three major categories
• White cells


  • Defend against disease by recognizing proteins that do not belong to the body
  • Able to ooze through the walls of capillaries to patrol the tissues and reach the lymph system
• Blood components

  • Plasma: the liquid portion
  • Red blood cells
  • White cells
  • Platelets
• Types of circulatory systems

  • Open system: fluid is circulated through an open body chamber
  • Closed system: fluid is circulated through blood vessels
• RBCs live about 4 months. Iron from hemoglobin is recycled in the liver and spleen
• Which blood cells transport oxygen? Red cells
• Thrombin converts fibrinogen into fibrin, which binds the clot in blood clotting
• Venules

  • Thin-walled collectors of blood, allow drainage from capillary beds
• Arteries


  • Thick-walled, lined with smooth muscle
• Arteries and arterioles carry blood away from the heart
• Immune system forms a hard cap over the plaque, partially blocking the artery, which can lead to clot formation
• Capillary walls are thin to allow exchange of gases and nutrients
• Regular exercise contributes significantly to LDL cholesterol reduction
• Blood LDL cholesterol can be reduced by a low-fat diet emphasizing high-fiber foods, antioxidants, and "good" fats, and reducing trans-fats
• Artery walls are thick and strong to withstand very high blood pressure when the heart contracts
• Classes of blood vessels

  • Arteries
  • Veins
  • Capillaries
• LDL cholesterol forms plaques in arteries, triggering inflammation
• Thrombin production

  Thrombin converts the protein fibrinogen into sticky fibrin, which binds the clot
• Capillaries


  • Thin walls, allow exchange of gases, nutrients, and wastes
• Capillaries allow exchange of nutrients, wastes, and gases
• Veins

  • Thinner walls than arteries, have valves and fewer smooth muscle cells
• Red cells transport oxygen
• Genetic and environmental factors contribute to atherosclerosis
• Arterioles


  • Branch off of arteries, can constrict to direct and control blood flow
• Veins and venules carry blood to the heart
• Arteries always carry blood away from the heart
• Capillary walls are thin to allow exchange of gases and nutrients and to force RBCs to move through in single file
• Three-chambered heart

  Separate atria allow some separation of oxygenated and deoxygenated blood, advantageous for land organisms like reptiles and amphibians
• Arteries must move blood out to all parts of the body
• Two-chambered heart

  A single atrium receives blood from the body cells and a ventricle sends blood to the gills to collect oxygen