Blood vessels

• arterioles carry blood from the arteries into the capillarlies
• venules carry blood from capillaries into the veins
• Arteries are adapted to carry blood at high pressure away from the heart.
• Adaptations of arteries:

  1. Collagen - Provides strength to prevent the vessel from bursting and to maintain the shape.
  2. Elastic fibres - Contain elastin that lets them stretch and recoil to minimise changes in pressure.
  3. Thick smooth muscle layer - Contracts and relaxes to constrict and dilate the lumen and control blood
• Differences between structure of arteries and arterioles:

  • arterioles have a larger lumen
  • arterioles have more smooth muscle
  • Arterioles have less elastin
• why do arterioles have less elastin than arteries?

  They don’t need to withstand such high pressures
• What is the function of smooth muscle in arteries and arterioles?

  They are adapted to control blood flow
• what are the two mechanisms in which smooth muscle can control blood flow?

  vasoconstriction and vasodilation
• What happens during vasoconstriction?

  • smooth muscle contracts
  • This constricts the blood vessel
  • Decreasing the blood flow
• What happens during vasodilation?

  • smooth muscle relaxes
  • this dilates blood vessels
  • increasing blood flow
• Outline adaptations of erythrocytes

  • biconcave shape increases surface area
  • no nucleus to give more space for haemoglobin
  • flexible to squeeze through capillaries
  • small for short diffusion pathway
  • transport proteins in membrane to allow chloride shift
• Circulatory systems are transport systems
• What is a single circulatory system?

  • blood passes through the heart only once per circuit
• Explain how the fish has a single circulatory system

  • the heart pumps blood to the gills to pick up oxygen
  • blood flows directly from the gills to the rest of the body to deliver oxygen
• What is a double circulatory system?

  • blood passes through the heart twice per circuit
• closed circulatory systems

  • Their blood is enclosed in vessels
  • Arteries generally distribute oxygenated blood
  • Veins generally return deoxygenated blood to heart
• Open circulatory system

  • their blood flows freely through the body cavity
  • blood returns to the heart through valves
  • blood doesn't just transport oxygen
• What type of circulatory system do mammals have?

  Closed, double circulatory system
• What does "double" mean in the context of a circulatory system?

  Blood passes through the heart twice for each circulation
• Why does pulmonary circulation occur at low pressure?

  To prevent damage to lung tissues
• What is the purpose of systemic circulation?

  Pumps blood at higher pressure around tissues
• How does systemic circulation affect the speed of circulation?

  It increases the speed of circulation
• How does the circulatory system of fish differ from that of mammals?

  Fish have a single circulatory system
• What does "closed" mean in the context of a circulatory system?

  Blood is maintained inside vessels
• What does "single" mean in the context of a fish's circulatory system?

  Blood passes through the heart once for each circulation
• What is the role of tissue fluid in fish?

  Tissue fluid bathes the cells to give nutrients
• How many atria and ventricles do fish have?

  One atrium and one ventricle
• What type of circulatory system do insects have?

  Open circulatory system
• What does "open" mean in the context of an insect's circulatory system?

  Blood not carried within vessels
• How does blood circulate in insects?

  Fluid circulates through the body cavity
• How do insect muscles assist in circulation?

  Muscles help to circulate the blood
• What are the layers of blood vessels and their functions?

  • Tunica externa: made of collagen
  • Tunica media: smooth muscle (controls blood flow) + elastic tissue (maintains high blood pressure)
  • Tunica interna: squamous epithelial cells (reduces friction)
• What is the structure of arteries?

  Thick tunica media, narrow lumen
• What role does smooth muscle play in arteries?

  Contracts to narrow the lumen
• What distinguishes arterioles from arteries?

  Thicker smooth muscle layer
• Why do capillaries have low blood pressure?

  Due to existing as a network
• What is the structure of capillaries?

  One squamous epithelial cell thick
• What are fenestrations in capillaries?

  Spaces between endothelial cells for fluid movement
• How do capillaries facilitate nutrient exchange?

  Narrow diameter slows blood flow for exchange
• What is the structure of veins?

  Large lumen, thin tunica media