transport animal

• Main parts of the chapter


  • Circulatory system
  • Transport of oxygen and carbon dioxide
  • The heart
• Circulatory system


  A system that involves blood vessels, blood, lymph, and the heart. Also called the cardiovascular system.
• Circulatory system


  • Needed for transport of nutrients and oxygen around the body
  • Needed for disposal of waste materials like carbon dioxide and urea
  • Transports hormones
  • Circulates white and red blood cells
• Close double circulation system


  • Blood is contained in blood vessels
  • Blood passes through the heart twice in one complete circuit
• Types of circulation systems


  • Close double circulation system
  • Open circulatory system
  • Single closed circulatory system
• Main blood vessels


  • Arteries
  • Capillaries
  • Veins
• Arteries


  • Carry blood away from the heart
  • Most carry oxygenated blood except pulmonary artery
  • Smaller versions are called arterioles
• Capillaries


  • Smaller, thinner vessels that bring blood close to tissues for exchange of oxygen and carbon dioxide
• Veins


  • Carry blood towards the heart
  • Usually carry oxygenated blood except pulmonary vein
• Tunica intima


  The innermost layer of an artery, made of squamous epithelial cells
• Tunica media


  • The thickest layer of an artery, containing collagen fibers, elastic fibers, and smooth muscle
• Tunica externa


  • The outermost layer of an artery, containing collagen fibers and elastic fibers
• Collagen fibers


  Can withstand high pressure and prevent rupture of vessels
• Elastic fibers


  Allow the artery to stretch and recoil, smoothing out the pulsatile blood flow
• Smooth muscle in the tunica media allows the artery to contract and relax, regulating blood pressure and flow
• Heart contraction


  Results in high systolic blood pressure
• Heart relaxation


  Results in low diastolic blood pressure
• Blood pressure is usually measured on the left arm at the same level as the heart to ensure an accurate reading
• Elastic fibers


  They can stretch and recoil, allowing the vessels to stretch when there is high pressure from the heart contracting, and recoil when the heart relaxes and blood pressure drops, providing a small push to maintain blood pressure
• Elastic fiber function


  1. Stretch when blood pressure is high

  2. Recoil when blood pressure drops

  3. Smooth out pulsatile blood flow
• Elastic fibers in arteries

  Allow blood pressure to not fluctuate too much, smoothing out the pulsatile flow near the heart
• Smooth muscle


  Contracts and relaxes, changing the diameter of arteries to control blood flow, in contrast to elastic fibers which stretch and recoil
• Smooth muscle relaxation


  Causes vessel dilation, increasing blood flow
• Smooth muscle contraction


  Causes vessel constriction, reducing blood flow
• Arteries near the heart


  • Have more elastic fibers to withstand high pulsatile pressure
  • Arteries further from the heart have more smooth muscle to control blood flow
• Capillaries


  Around 7 micrometers in diameter, made of endothelial or squamous epithelial cells, with pores/gaps between cells to allow diffusion
• Capillary traits


  • One cell thick for short diffusion distance
  • Small lumen diameter to slow blood flow and bring red blood cells close to tissues
  • High surface area from capillary network
  • Low blood pressure due to distance from heart
• Veins


  Have lower blood pressure and blood flow velocity compared to arteries, have a wider lumen and thinner tunica media
• Vein features


  • Presence of valves to prevent backflow
  • Surrounded by skeletal muscles that contract to push blood back to the heart
• Arteries appear more circular with a wavy endothelial lining, while veins appear more flattened and oval-shaped
• Graphs showing differences between blood vessels

  • Lumen diameter (arteries narrow, veins wide, capillaries tiny)
  • Surface area (capillaries highest)
  • Blood velocity (arteries highest, veins lowest)
  • Blood pressure (arteries pulsatile, veins very low)