Blood Vessels

• in which direction does blood flow in arteries and veins?

  • arteries - away from heart towards tissue
  • vein - into the heart from tissues
• what's the difference between an artery and an arteriole?

  • arteries are larger to withstand high pressure
  • arterioles are smaller to help pressure transition/size transition to capillaries (have less muscle)
• what is the difference between a vein and a venule?

  • venules don't have valves
• what is the order of artery/arteriole structures from inside to outside?

  • lumen
  • endothelium
  • elastic fibres
  • smooth muscle
  • collagen fibres
• what is the function of arteries and arterioles?

  • carries blood away from heart to the tissue of the body
  • carries oxygenated blood (except pulmonary artery)
  • blood is under higher pressure than blood in veins - thick muscle to withstand pressure
• what is the function of elastic fibres, smooth muscle and collagen fibres?

  • enables arteries/arterioles to withstand force of pumping blood
  • smooth muscle allows for easy blood flow
• what is vasoconstriction?

  when smooth muscle contracts, constricting blood flow into capillary bed
• what is vasodilation?

  smooth muscle relaxes, blood flows into capillary bed
• what features help arteries/arterioles to maintain high pressure?

  • small lumen - small volume of blood can pass through
  • thick (smooth) muscle allows constriction of lumen to maintain high pressure
  • elastic fibres recoil to control lumen, but can also expand
• what features help arteries/arterioles to withstand high pressure?

  • elastic fibres - can stretch
  • strong collagen - collagen fibres stop elastic fibres from stretching too much
  • folded endothelium than can unfold when blood passes through without tearing
  • smooth muscle - allows easy blood flow
• why are valves not necessary in arteries or arterioles?

  • under high pressure so backflow of blood in unlikely to occur
  • high pressure ensure blood is flowing in onw direction only
• what is the function of veins and venules?

  • carry blood away from body towards heart
  • is under lower pressure due to large lumen
• what is the order of vein/venule structures from inside to outside?

  • lumen (larger than arteries/arterioles)
  • endothelium
  • elastic fibres
  • smooth muscle
  • collagen fibres
• what does skeletal muscle allow for in veins/venules?

  • allows for blood to flow in correct direction when contracting - pushes blood through veins back towards the heart
• how do valves work?

  • blood flowing towards the heart passes easily through valves
  • valves close - preventing blood from flowing in the wrong direction (prevents backflow)
• what are capillaries?

  • form an extensive network through all tissues of the body
  • substances are exchanges through capillary walls between tissue cells and blood
  • provide a large surface area for diffusion
  • walls are a single endothelial cell thick, giving a very thin/short diffusion pathway
• what is the order of capillary structures from inside to outside?

  • lumen (small so red blood cells can pass through)
  • endothelium
  • fenestrations (pores between cells - allows exchange of materials)
• what is meant by the term endothelium?

  • a single layer of squamous epithelial cells that line the interior surface of blood vessels, and lymphatic vessels
• what is the importance of smooth muscles in the arteriole walls?

  • vasoconstriction and vasodilation
• why does the pressure from the aorta to the vena cava decrease drastically?

  • only heart gives force to pump blood around body for further from the heart the lower the pressure
• why does the blood pressure change as the distance from the heart increases?

  • some vessels are unable to withstand high pressure due to their thin walls and lack for muscle-capillaries
  • change in lumen size
  • heart beat adds pressure, the further from the heart the less influence the heart beat has on the pressure
  • veins need smooth muscle to contract for blood to move towards heart
• why does the blood pressure fluctuate in the aorta and arteries?

  • systole/contraction of the heart increases pressure
  • contraction of ventricle muscle/wall
  • diastole/relaxation/blood flowing onwards, decreases pressure
• what is a sphygmomanometer?

  • monitors blood pressure
  • top number shows systolic pressure
  • middle number shows diastolic pressure
  • bottom number shows heart rate/pulse rate