lecture 10

Question 1

describe blood vessels

Answer 1

• Contribute to homeostasis
  
  • Helps with
    ○ Structure for blood flow
    ○ Transport of nutrients + wasye
    ○ Adjust velocity + flow of blood
    Goes from arteries, to arterioles, to capillaries, to venules, to veins

Question 2

describe the structures of arteries vs veins vs capillaries

Answer 2

• Arteries + veins
  ○ Both used for transport
  ○ Veins have valves
  • Capillaries
    
    • much thinner + basic in structure so waste + nutrients able to diffuse, capillary exchange

Question 3

describe the structure of arteries

Answer 3

• The recoil of elastic arteries propels blood onwards when heart ventricles are relaxing (diastole)
  Medium sized arteries are mostly smooth muscle

Question 4

describe arterioles

Answer 4

○ Wall thickness half of total vessel diameter
○ Regulate blood flow to capillaries
Can regulate own resistance

Question 5

describe resistance in capillaries

Answer 5

○ Mainly due to friction between blood + walls
○ The narrower the vessels, greater the resistance
○ Vasoconstriction icnreases resistance
○ Vasodilation reduces resistance
Arteriole vasoconstriction or relacation controls flow to capillaries

Question 6

describe sphincters in relation to capillaries

Answer 6

Found at junctions of metarterioles + capillaries, regulate capillary perfusion

Question 7

describe capillaries

Answer 7

○ Pass single file
○ No tunica media or externa
○ Single layer of endothelial cells + basmenet membrane
○ Permits the exchange of nutrients + waste between blood + tissue cells
○ Liver has alot of important capillaries
○ Has a arteriole end and a venule end
While it does go in a circle, has a small net leak of 3L/day into the tissue, this is drained into lymphatic system and put back in, the rest is reabsorbed at venous end

Question 8

describe venules

Answer 8

○ Thin walls
○ Drain capillary blood
○ Ebgin returning blood flow back to the heart
Muscular venules found further away from capillaries

Question 9

describe veins

Answer 9

• Responsible for carrying blood back to the heart
  
  • Mostly carry deoxygenated blood
  • Pulmonary vein carries oxygenated blood
  • At rest, the largest portion of the blood in systemic veins + venules (blood reservoirs)
    Veins are capacitance, vessels are blood storage (not technically storage tho, blood still has to be moving, otherwise will clot)

Question 10

describe vein structure

Answer 10

• Tunica externa is thickest layer
  
  • Has thinner walls but larger lumens then arteries
  • Adapt to variations in pressure + volume
  • Veins are 24 times mroe compliant than arteries
    Valves keep blood flowing in 1 direction

Question 11

what is th efunction of the cardiovascular system

Answer 11

• Cardiovascular system keeps blood flowing through capillaries to allow exchange of amterials between blood + interstitial fluid

Question 12

what are the 3 mechanisms for capillary exchange

Answer 12

diffusion, transcytosis, bulk flow

Question 13

describe diffusion

Answer 13

§ Need a conc. Gradient
§ 3 types
□ Simple diffusion across membrane
□ Diffusion through pores- glucose, hormones, amin acids
Diffusion through large intercellular clefts- gaps between endothelial cells

Question 14

describe transcytosis

Answer 14

§ Uses membrane vesicles for transport of large lipid insoluble materials e.g. Insulin
§ Endocytosis- from lumen into endothelial cells
§ Exocytosis- from endothelial cells into itnerstitial fluid
Transcytosis- movement from 1 side of cell to other

Question 15

describe bulk flow

Answer 15

§ Transfer of fluid (water) between blood and interstitial fluid
§ Driven by hydrostatic pressure + osmotic pressure
□ Hydrostatic
® physical rpessur ethat water in the plasma exerts on vessel walls
® Due to blood pressure
□ Osmotic
® In capillary blood only plasma proteins contribute to the effective osmotic pressure- called oncotic pressure
® Due to plasma proteins

			□ Note: electrolytes do NOT contribute to fluid exchange
			
		§ Fluid is forced out of capillaries at the arterial end of the capillary bed
		§ Fluid is reabsorbed by the capillaries at the venous end of th ecapillary bed
		§ Fluid filtraiton + reabsorption determiens the relative volumes of the plasma + the interstital fluid + depends on the relative pressures wihtin the capillaries + itnerstititial space

		§ Is important for regulation fo relativ eovlumes of blood + itnerstitial fluid
		§ Flows from high to low pressure
		§ Capillary to interstitial fluid- filtration promoted by blood hydrostatic pressure + interstitial fluid osmotic pressure
		§ Interstitital to capillary- repeabsorption promoted by blood (oncotic) colloid osmotic pressure + itnerstitial fluid hydrostatic pressure
		§ Sum of all pressures is called net filtration pressure

Question 16

what are the 4 forces thare regulate bulk flow

Answer 16

starling forces

			□ Capillary hydrostatic pressire= blood pressure
				® Favours filtration (flow out of capillary)
			□ Plasma colloud osmotic/oncotic rpessure= Blood osmolarity
				® Favourd absorption (flow into capillary)
			□ Interstitial fludi pressure = fluid pressur eoutside capillary
				® Favours absorption (flow into capillary)
			□ Interstitital fluid colloid osmotic/oncotic pressure = fluid osmolarity outside capillary Favours filitration (flow out of capillary)

Question 17

describe net filtration

Answer 17

• The summation of the hydrostatic + osmotic forces acting on a capillary promotion filitration (or reabsorption)
  
  • NFP = (BHP + IFOP) - (BCOP + IFHP)
  1. Pressure pushing fluid out of capillary (filtration) (BHP + IFOP)
     ○ Capillary hydrostatic pressure + interstitital colloid osmotic pressure
  2. Pressure pushing fluid into capillary (Reabsorption) (BCOP-IFHP)
     ○ Plasma colloid osmotic pressure + itnerstitial hydrostatic pressure