Lecture 5: Blood Vessels & Hemodynamics

Question 1

what is capillary exchange

Answer 1

many molecules pass by diffusion between blood and interstitial fluid while moving down thier concentration gradients

Question 2

what are the 4 routes of crossing a capillary

Answer 2

1. diffusion thorugh plasma membrane (lipid-soluble substances ex. fats) (high[]->low[] until=)
2. movement thorugh intercellular clefts (water-soluble substances)
3. movement through fenestrations (water-soluble substances)
4. transport via vesicles (large substances ex. proteins) (bulk transport)

Question 3

what is bulk flow of fluid movements

Answer 3

-fluid is forced out of clefts of capillaries at arterial end, and most returns to blood at venous end (extremely important in determining relative fluid volumes in blood and interstitial space
-bulk fluid flow across capillary walls causes continuous mixing of fluid between plasma and interstitial fluid (maintains interstitial environment)

Question 4

what does direction and amiunt of fluid flow depend on (bulk flow)

Answer 4

it depends on two opposing forces
-blood hydrostatic pressures (BHP)
-blood colloid osmotic pressures (BCOP)

Question 5

what is hydrostatic pressure

Answer 5

the force applied by fluid pressing against wall
there are two types; capillary blood hydrostatic pressure & interstitial fluid hydrostatic pressure

Question 6

what are the two types of hydrostatic pressure and explain them

Answer 6

1. Capillary blood hydrostatic pressure (BHP): capillary blood pressure that tends to force fluids through capillary walls into interstitial fluid (ISF) -> filtration. it is greater at the arterial end (35mmHg) of bed that at venule end (16-17mmHg)
2. Interstitial fluid hydrostatic pressure (IFHP): pressure pushing fluid back into vessel. usually assumed to be zero because lymphatic vessels drain ISF

Question 7

what is blood colloid osmotic pressure

Answer 7

-also called “oncotic pressure, OPc”
-“sucking” pressure created by non-diffusible plasma proteins (from high [ ] to low [ ] of H2O) pulling water back into capillary
-BCOP ~26mmHg

Question 8

what is interstitial osmotic pressure (IFOP)

Answer 8

from lymphatic vessels
-pressure is inconsequential because ISF has very low protein content
-IFOP only ~1mmHg

Question 9

what is hydrostatic-osmotic pressure interactions

Answer 9

-net fluid flow out at arterial end-> filtration
-net fluid flow in at venous end -> reabsorption
-more fluid leaves at arterial end than is returned at venous end-> excess interstitial fluid is returned to blood via lymphatic system

Question 10

what is net filtration pressure and how is it calculated

Answer 10

it comproses all forces acting on capillary beds
-NFP= (BHP + IFOP) - (IFHP + BCOP)
-(BHP + IFOP) promotes filtration
-(IFHP + BCOP) promotes reabsorption
-net fluid flow out at arterial end-> filtration
-net fluid flow in at venous end-> reabsorption
-more fluid leaves at arterial end than is returned at venous end which causes excess interstitial fluid is returned to blood via lymphatic system

Question 11

net filtration occurs at the arteriolar end of a capillary

Answer 11

1. hydrostatic pressure in capillary (HPc) “pushes” fluid out of capillary
2. osmotic pressure in capillary (OPc) “pulls” fluid into capillary
   NFP= (HPc + OPif) - (HPif + OPc)
   positive NFP in capillary causes fluids to move from the capillary into the interstitial space

Question 12

net reabsorption occurs at the venous end of a capillary

Answer 12

1. hydrostatic pressure in capillary (HPc) “pushes” fluid out of capillary. the pressure has dropped because of resistance encountered along the capillaries
2. osmotic pressure in capillary (OPc) “pulls” fluid into capillary
   NFP= (HPc + OPif) - (HPif + OPc)
   notice that the NFP at the venous end is a (-), this means that reabsorption not filtration is occuring and fluid moves from the interstitial space into the capillary

Question 13

what are some important differences between systemic arteries and veins

Answer 13

-arteries run deep only but veins are both deep & superficial, deep veins share name with corresponding artery, superficial veins do not correspond to names of arteries
-venous pathways are more interconnected (anastamoses), veins can have more than one name making venous pathways harder to follow
-the grain and digestive systems have unique venous drainage systems, brain contains dural venous sinuses, venous system of the digestive system drains into hepatic portal system which perfuses through liver before returning to heart

Question 14

what are the general functional patterns of vessels

Answer 14

1. similar distribution on right and left, except near the heart
2. change in vessel names with different anatomical positions
3. multiple arteries and veins in tissues and organs, anastomoses (multiple interconnections) occurs

Question 15

what are the different circulatory routes

Answer 15

-systemic circulation
-pulmonary circulation
-hepatic portal circulation
-fetal circulation
* systemic & pulmonary makes up vascular system

Question 16

what is the pathway of blood through the heart

Answer 16

-heart consists of two side-by-side pumps
-right side: pump for pulmonary ciculation (short, low pressure circulation)
-left side: pump for systemic circulation (long, high pressure circulation)
-equal volumes of blood are pumped to pulmonary and systemic circuits

Question 17

what is systemic circulation

Answer 17

-arteries and arterioles that carry deoxygenated blood from left ventricle to capillaries, nutrients to body tissues, all arise from aorta
-veins and venules that return deoxygenated blood to right atrium, removes CO2, wastes, all drain into IVC/ SVC & coronary sinus

Question 18

what are the systemic vessels

Answer 18

-84% of blood volume
-aorta, common carotid artey, brachiocephalic artery , subclavian artery, coronary artery, azygos vein, SVC, IVC

Question 19

slide 16

Question 20

slide 17

Question 21

what is the azygos system

Answer 21

-netowrk of veins within thoracic regoin that run on either side of vertebral column
-drains most thoracic region and part of abdominal walls
-three veins: azygos vein, accessory hemiazygos veins & hemiazygos vein all empty into the SVC

Question 22

what is the clinical significance of the azygos system

Answer 22

-serves as bypass for IVC and hepatic portal system
-obstruction to IVC or hepatic portal system, blood shuttles from lower body portion to SVC via azygos system

Question 23

what is the hepatic portal system and the clinical significance

Answer 23

-connection of two capillary beds- one in gastrointestinal (GI) tract, the other in the liver
-clinical significance: nutrient-rich blood (may contain toxins and microbes) from GI organs (spleen, pancreas, gallbladder) delivered to liver sinusoids for processing, after processing in liver blood collects in hepatic veins and empties into IVC

Question 24

what is the pulmonary circulation

Answer 24

-short loop runs from heart to lungs and back to heart
-deoxygentaed blood from RV to alveoli (air sacs) in lungs
-returns oxygenated blood from lungs to LA

Question 25

slide 22

Question 26

what is fetal circulation

Answer 26

-structures that permit exchange of materials between fetus and mother
-non-functioning lungs, kidneys and GI organs
-exchange of O2, nutrients and CO2, wastes by diffusion from maternal blood at placenta

Question 27

what is the placenta blood supply

Answer 27

-blood flows to placenta through umbilical
-a pair of umbilical arteries
-blood returns from placenta
-a single umbilical vein that drains into ductus venosus
-empties into IVC

Question 28

what is fetal pulmonary circulation bypasses

Answer 28

-foramen ovale (interarterial opening), covered by valves-like flap, directs blood from right to left atrium
-ductus arteriosus- short vessel, connects pulmonary trunk to aorta

Question 29

slide 25