microcirculation and tissue fluid exchange

Question 1

is the cardiovascular system closed open

Answer 1

closed

Question 2

is the lymphatic system closed or open

Answer 2

open- starts at tissues only goes in one direction

Question 3

what is the pulmonary circulation

Answer 3

• flow of blood from the heart to the lungs and back to the heart
• pressure much less than systemic circulation
• goes from right side of the heart and enters back from left

Question 4

what is systemic circulation

Answer 4

• circulation where blood flows from the heart to the peripheral tissues and than back to the heart
• pressure much higher
• leaves heart from left side and enters back from right side

Question 5

what clinical signs/conditions are a consequence of tissue fluid exchange

Answer 5

• insect bite causing inflammation
• pitting oedema- chronic
• diffuse edema due to infections (sepsis)
• local oedema due to inflammation
  -nephrotic syndrome
• ascites= water belly
  -malnutrition
• filariasis- chronic oedema due to lymph node desturction

Question 6

what are examples of vasodilator substances

Answer 6

• adenosine
• histamine
• nitric oxide
• carbon dioxide
  -pottasium ions
• hydrogen ions

Question 7

what is a metarteriole and what are their roles and how do they control blood flow to capillaries

Answer 7

• small blood vessel that connects arterioles to capillaries
• control blood flow to capillary by structures known as sphincter
• when o2 levels are low sphincter opens, when o2 levels are high sp is closed

Question 8

what are true capillaries

Answer 8

where tissue fluid exchange happens

Question 9

what are preferential channel in capillaries

Answer 9

• a vessel in the microcirculation that carries a greater proportion of red blood cells through capillaries
  -When the precapillary sphincters constrict, most blood flow travels through the preferential channel instead of the capillary bed

Question 10

what is the tension equation

Answer 10

tension= pressure x radius
- pressure keeps capillary open

Question 11

what are the three transcapillary exchanges that happen

Answer 11

• diffusion
• filtration/reabsorption
• pinocytosis

Question 12

what are the three structural classification of capillaries

Answer 12

• closed
  -fenestrated
• discontinuous

Question 13

what is the strucutre of a closed capillary

Answer 13

• has endothelial cells which have tight (brain) or loose (skin or muscle) junctions between them
• endothelial membrane- diffusion happens across
• basement membrane- links the endothelium to connective tissue or muscle
• glycocalix

Question 14

structure of a fenestrated capillary

Answer 14

• in kidney or glands
• has endothelial cells, endothelium membrane, glycocalix, basal membrane
• fenestrae with or without diaphragm (without in kidney)
• fenestrae are holes that allow passage of certain substances
• diaphragm acts as a filter covers the fenestrae

Question 15

discontinous capillary structure

Answer 15

• liver, bone marrow, spleen
• again has endothelial cells, endothelium, glycocalix, basal mebrane
• gaps (100nm-3um)
• gaps allow movement of macrophages e.g. kuppfer cells in liver

Question 16

how can molecules pass through endothelim

Answer 16

• small molecules between the tight or loose junctions- paracellular
• large molecules have to enter the cell transcellular
• e.g. transednothelial channel, receptor mediated, endcytosis

Question 17

what are the factros determining filtration in the capillaries

Answer 17

• capillary pressure (hydrostatic)- out
• interstitial fluid colloid osmotic pressure -out- osmotic
  -interstitial fluid pressure- in - hydrostatic
• plasma colloid osmotic pressure - in- oncotic pressure

Question 18

what is starlins hypothesis

Answer 18

net filtration= outward forces - inward forces

Question 19

during normal circumstances what is the net movement of fluid and talk about the hydrostatic and oncotic pressure

Answer 19

• hydrostatic pressure high at arteriole end and low at venuole end
• oncotic pressure stays the same as its determined by the plasma proteins which do not leave the capillary
• at arteriole end net movement is filtration as hydrostatic>oncotic
• at venuole end net movement is absorbtion as oncotic>hydrostatic
• tend to filter out and reabsorb the same amount of fluid

Question 20

what is the tissue fluid exchange in pulmanory capillaries

Answer 20

• in pulmanory capillaries hydrostatic pressure is always lower (as pulmanory circulation has lower pressure) than oncotic pressure even at arteriole end
• and therefore only reabsorption takes place
• prevent fluid build up in lung

Question 21

what is the tissue fluid exchange in the kidneys

Answer 21

• hydrostatic pressure always greater than oncotic pressure even at venuole end
• so only filtration takes place

Question 22

what is the 1st cause of oedema

Answer 22

• increased venous pressure and therefroe less reabosrption takes place at venuole end leading to fluid build up

Question 23

what is the 2nd cause of oedema

Answer 23

• inflammation
• release of mediators which cause vasodilation and increased permability of capillary
• leads to increased hydrostatic pressure at arteriole end- essentialy local vasodilation causes increase in local blood pressure due to increased blood flow and therefroe more filtration happens

Question 24

what is the 3rd cause oedema

Answer 24

• reduced plasma proteins levels
• reduced oncotic pressure
• more filtration happens and less reabsorption
• nephrotic syndrome, malnutrition, ascits

Question 25

what is the fourth cause of oedema

Answer 25

• reduced lymph drainage
• filariasis- causes lymph node destruction and that leads to reduced lymph drainage
• 3l of fluid goes into lymphatic system if that 3l doesnt go in this causes build up