Anatomy & physiology

• What are the 5 main types of blood vessels?

  Arteries, arterioles, capillaries, venules, and veins
• What is the primary function of capillaries?


  They are the site of exchange between blood and interstitial fluid
• What is the tunica interna also known as?


  Tunica intima
• What is the role of the endothelium in blood vessels?


  It is the inner lining in direct contact with blood and plays an active role in vessel-related activities
• What is the tunica media composed of?


  Muscular and connective tissue
• How does the tunica media vary among different vessel types?


  It shows the greatest variation among vessel types
• What regulates the diameter of the lumen in blood vessels?

  Smooth muscle in the tunica media
• What is the function of the tunica externa?


  It helps anchor the vessel to surrounding tissue
• What is the characteristic of arteries regarding their walls?

  They have thick muscular-to-elastic tunica media
• What does high compliance in arteries mean?


  Walls stretch and expand in response to pressure without tearing
• What is vasoconstriction?


  A decrease in lumen diameter
• What is vasodilation?


  An increase in lumen diameter
• What are capillaries known as?


  Exchange vessels
• Why do capillaries lack tunica media and tunica externa?


  To facilitate the exchange of substances
• What is the primary function of veins?


  To carry blood to the heart
• How do the walls of veins compare to those of arteries?


  Veins have very thin walls in relation to total diameter
• What is the role of valves in veins?


  They aid in venous return by preventing backflow
• What is the largest portion of blood at rest found?

  In systemic veins and venules
• What is venoconstriction?


  A process that reduces the volume of blood in reservoirs
• What are the three basic methods of capillary exchange?


  Diffusion, transcytosis, and bulk flow
• What is the most important method for solute exchange in capillaries?

  Diffusion
• How do substances move during diffusion?


  Down their concentration gradient
• What substances move from blood to interstitial fluid?

  Oxygen and nutrients
• What substances move from body cells to blood?

  Carbon dioxide and wastes
• What can cross the capillary wall?


  Substances can cross through intracellular clefts, fenestrations, or endothelial cells
• What is unique about sinusoids regarding diffusion?


  Most plasma proteins can cross, and even blood cells can leave
• What limits diffusion in the blood-brain barrier?

  Tight junctions between endothelial cells
• What is transcytosis?


  A process where substances in blood plasma become enclosed within pinocytotic vesicles
• What is bulk flow?


  A passive process where large numbers of particles move together in the same direction
• What is filtration in the context of capillary exchange?


  Movement from capillaries to interstitial fluid
• What is reabsorption in capillary exchange?


  Movement from interstitial fluid to capillaries
• What is the formula for net filtration pressure (NFP)?


  NFP = (BHP + IFOP) – (BCOP + IFHP)
• What promotes filtration in capillaries?

  Blood hydrostatic pressure (BHP) and interstitial fluid osmotic pressure (IFOP)
• What is the average BHP in capillaries?


  It falls from 35 to 16 mmHg over the capillary bed
• What promotes reabsorption in capillaries?


  Blood colloid osmotic pressure (BCOP) and interstitial fluid hydrostatic pressure (IFHP)
• What is the average BCOP?


  It averages 36 mmHg
• What is the interstitial fluid hydrostatic pressure (IFHP)?


  It is close to zero mmHg
• What is blood flow defined as?


  The volume of blood that flows through any tissue in a given period of time
• What is cardiac output (CO)?


  The volume of blood that circulates through systemic or pulmonary blood vessels each minute
• How is cardiac output calculated?


  CO = heart rate (HR) x stroke volume (SV)