circulation

• Open circulatory system


  A circulatory system that does not have the use for arteries and the fluids flow freely and openly through the organs instead
• Components of open circulatory system


  • Fluid
  • Vessels
  • Heart
• Hemolymph


  Interstitial fluid = extracellular fluid
• Open circulatory system blood flow


  1. Heart contractions - hemolymph → vessels → interconnected sinuses

  2. Heart relaxations - draw hemolymph back into the heart
• Open circulatory system


  • Low pressure, low efficiency, low E
• Organisms with open circulatory system


  • Arthropods
  • Most molluscs
• Closed circulatory system


  Blood is a circulatory fluid confined to vessels
• Closed circulatory system


  • Blood is necessary for oxygen transport and waste removal
  • Heart pumps blood through branched vessels
  • Higher pressure - more efficient, requires more energy
• Organisms with closed circulatory system


  • Annelids
  • Cephalopods
  • Vertebrates
• Vertebrate circulation


  Cardiovascular system
• Components of vertebrate cardiovascular system


  • Heart: pumps blood
  • Vessels: carry blood
  • Exchange at capillaries
• Fish circulatory system


  • Single circulation
  • Heart: 2 chambers (1 atrium, 1 ventricle)
  • Not very efficient
  • Blood is not as oxygenated as it could be
  • Lower blood pressure due to single circulation
• Amphibian circulatory system


  • Double circulation
  • Heart: 3 chambers (2 atria, 1 ventricle)
  • Pulmocutaneous circuit (blood to skin and lungs)
  • Systemic circuit (oxygenated blood to body)
  • Circuits mix together sometimes
• Mammal and bird circulatory system


  • Heart: 4 chambers (2 atria, 2 ventricles)
  • Pulmonary circuit (gas exchange in lungs)
  • Systemic circuit (oxygen/nutrient delivery, homeostasis)
  • Circuits do not mix at all, completely separate
• Human heart


  • Organ that must pump blood
  • More than 2 chambers made of muscle
  • Atria receive blood from veins
  • Ventricles pump blood to arteries
  • Pericardium is connective tissue sac enclosing the heart
• Heart valves


  • 4 valves: 2 atrioventricular (right, left AV), 2 semilunar (pulmonary, aortic)
  • Prevent backflow of blood
• Heart contractions


  1. Autorhythmic - internal initiation, not via AP from CNS

  2. Sinoatrial (SA) node generates action potentials

  3. Impulse from SA node spreads through atria

  4. Delayed at atrioventricular (AV) node

  5. Signals transmitted via bundle branches to ventricles
• Regulation of heart rate

  • Nervous system - baroreceptors detect blood pressure changes, autonomic nerves control rate
  • Endocrine system - stress, temperature affect rate
• Blood vessel structure


  • 3 layers: endothelium, smooth muscle, connective tissue
  • Thick walls prevent diffusion
• Arteries


  • Carry blood from heart to organs
  • Arteries → arterioles → capillaries
• Capillaries


  • Microscopic blood vessels in tissues
  • Capillary bed network
  • Site of exchange between blood and tissues
• Capillary structure


  • 2 layers: endothelium and basal lamina
  • At least 1 capillary near every cell in body
  • Only location of exchange between blood and interstitial fluid
• Veins


  • Carry blood from organs to heart
  • Capillaries → venules → veins
  • Have one-way valves to prevent backflow
• The difference between veins and arteries is in regards to the direction of the blood flow and NOT oxygen concentration
• Mechanism of exchange


  1. Thin capillary lining allows diffusion

  2. Plasma under pressure forces some fluid into interstitial fluid

  3. Antagonistic forces - blood pressure, osmotic pressure

  4. Arterial end - fluid out, venous end - fluid in

  5. Not all fluid returns, 15% remains in interstitial fluid
• Lymphatic system


  • Accessory circulatory system
  • Functions: interstitial fluid to blood, absorb lipids, defend against disease
  • Anatomy: lymph fluid, lymph vessels, lymph nodes, lymph ducts