microcirculation and tissue fluid exchange Flashcards
is the cardiovascular system closed open
closed
is the lymphatic system closed or open
open- starts at tissues only goes in one direction
what is the pulmonary circulation
- 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
what is systemic circulation
- 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
what clinical signs/conditions are a consequence of tissue fluid exchange
- 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
what are examples of vasodilator substances
- adenosine
- histamine
- nitric oxide
- carbon dioxide
-pottasium ions - hydrogen ions
what is a metarteriole and what are their roles and how do they control blood flow to capillaries
- 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
what are true capillaries
where tissue fluid exchange happens
what are preferential channel in capillaries
- 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
what is the tension equation
tension= pressure x radius
- pressure keeps capillary open
what are the three transcapillary exchanges that happen
- diffusion
- filtration/reabsorption
- pinocytosis
what are the three structural classification of capillaries
- closed
-fenestrated - discontinuous
what is the strucutre of a closed capillary
- 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
structure of a fenestrated capillary
- 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
discontinous capillary structure
- 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
how can molecules pass through endothelim
- small molecules between the tight or loose junctions- paracellular
- large molecules have to enter the cell transcellular
- e.g. transednothelial channel, receptor mediated, endcytosis
what are the factros determining filtration in the capillaries
- capillary pressure (hydrostatic)- out
- interstitial fluid colloid osmotic pressure -out- osmotic
-interstitial fluid pressure- in - hydrostatic - plasma colloid osmotic pressure - in- oncotic pressure
what is starlins hypothesis
net filtration= outward forces - inward forces
during normal circumstances what is the net movement of fluid and talk about the hydrostatic and oncotic pressure
- 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
what is the tissue fluid exchange in pulmanory capillaries
- 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
what is the tissue fluid exchange in the kidneys
- hydrostatic pressure always greater than oncotic pressure even at venuole end
- so only filtration takes place
what is the 1st cause of oedema
- increased venous pressure and therefroe less reabosrption takes place at venuole end leading to fluid build up
what is the 2nd cause of oedema
- 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
what is the 3rd cause oedema
- reduced plasma proteins levels
- reduced oncotic pressure
- more filtration happens and less reabsorption
- nephrotic syndrome, malnutrition, ascits
what is the fourth cause of oedema
- 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
