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53 Cards in this Set
- Front
- Back
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What does microcirculation refer to?
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The capillary bed
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What percentage of circulating blood volume is in the microcirculation?
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5%
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What's the name for the cells of the capillary wall? What are they supported by?
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Endothelial cells, a basement membrane
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What factors determine the permeability of the capillary? (More obvious than might think)
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Differences in the strength and size of the connections between the endothelial cells and the thickness and permeability of the basement membrane
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What are the two main methods of exchange across a capillary?
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Diffusion and bulk flow (The movement of extracellular fluid between plasma and the interstitial space)
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The movement of extracellular fluid between plasma and the interstitial space
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Bulk flow
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During bulk flow at a capillary, production of interstitial fluid at the arteriolar end is in excess of reabsorption. What is the name for this excess interstitial fluid?
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Lymph
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What is another name for interstitial fluid?
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Tissue fluid
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What is the interstitial space wrt biology?
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The space that surrounds the cells and where interstitial fluid (tissue fluid) sits!
1305250111 |
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Interstitial fluid production =
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Rate fluid production - rate fluid reabsorption
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Interstitial fluid production = Rate fluid production - rate fluid reabsorption
If filtration is increase, or reabsorption decreased the production of interstitial fluid production is increased. What can this lead to? |
Oedema
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What is the name for the first arteriole off an artery? What is the name for the last arteriole before a capillary bed?
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Primary arteriole (large amounts of smooth muscle and innervation)
The terminal arterioles (small amounts of smooth muscle and innervation, calibre determined by tissue metabolites) |
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What is the name for the group of capillaries given off by a terminal arteriole?
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A 'cluster' or 'module' of capillaries
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The walls of postcapillary venules contain cells known as pericytes. As such, postcapillary venules can be known as what other name?
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Pericytic venules
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What is a pericyte?
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A cell that supports postcapillary venules. It serves to support these vessels, but it can differentiate into a fibroblast, smooth muscle cell, or macrophage as well if required
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What are pericytic venules?
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Postcapillary venules, they contain cells known as 'pericytes'
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Postcapillary venules permit the passage of fluid between plasma and interstitial space T/F
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T
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Some capillaries have pericytes T/F
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T
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What are the three types of capillary?
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Continuous
Fenestrated Discontinuous |
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Which is the most common type of capillary?
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The continuous capullary
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Fenestrated capillaries are perforated by small circular pores. What is the name for these pores?
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Fenestrae
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Where are fenestrated capillaries found? Why?
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Exocrine glands and renal glomerulus
Fenestrated capillaries permit a relatively free passage of salts and water from the plasma to the tissues, thus, this type of capillary is found in tissues that are specialised for bulk fluid exchange |
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This type of capillary permits a relatively free passage of salts and water from the plasma to the tissues. This type of capillary is found in tissues that are specialised for bulk fluid exchange (such as exocrine glands and the capillaries of the renal glomerulus)
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Fenestrated capillaries
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This type of capillary is found in the liver, spleen and bone marrow
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Discontinuous capillary
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This is the only capillary which is sufficiently large to permit the passage of plasma proteins
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Discontinuous capilliary
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What is 'vasomotion'?
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A term used to describe the variation in capillary bed flow
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A term used to describe the variation in capillary bed flow
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Vasomotion
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From inside to out, list the layers of the capillary
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Lumen
Glycocalyx Endothelium Basal lamina (Pericyte) |
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The diffusion coeficient becomes smaller as the molecular size decreases T/F
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F. The diffusion coefficient becomes smaller as the molecular size increases, so that large moleccules diffuse more slowly than small ones (see equation in P&R p 294)
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In Fick's law: Amount moved =
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Area x concentration gradient x diffusion coefficient
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Area x concentration gradient x diffusion coefficient =
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Amount moved (Fick's law)
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What is the difference between transcellular exchange, and paracellular exchange through a capillary?
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Transcellular: When very lipophilic substances pass through the endothelial cells relatively freely
Paracellular exchange: When water-soluble substances pass through small spaces between cells and through fenestrations |
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A form of osmotic pressure exerted by proteins in blood plasma that usually tends to pull water into the circulatory system
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Oncotic/colloid osmotic pressure
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What are the requirements for a Donnan equilibrium to exist?
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It exists when two compartments are separated by a membrane that is permeable to ions and to water, but not to large molecules such as proteins
(This exists across most capillaries) |
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It exists when two compartments are separated by a membrane that is permeable to ions and to water, but not to large molecules such as proteins
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A Donnan equilibrium (This exists across most capillaries)
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What is the capillary pressure? (Obvious)
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The pressure within the capillary
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What is the interstitial pressure?
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The pressure within the tissue surrounding the capillary
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What is the oncotic pressure?
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The osmotic pressure exerted by the plasma proteins
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'The pressure within the tissue surrounding the capillary' is called the...
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Interstitial pressure
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'The osmotic pressure exerted by the plasma proteins' is called the...
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Oncotic pressure
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The greater this value, the greater is the tendency for fluid to pass from the capillary to the interstitium (it's a pressure)
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The value of hydraulic pressure (difference between the capillary pressure and that of the interstitial fluid)
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What is the pressure caused by the difference between the capillary pressure and that of the interstitial fluid?
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The hydraulic pressure
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Net filtration pressure =
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Net pressure forcing fluid from capillary - net pressure in tissues
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Net pressure forcing fluid from capillary - net pressure in tissues =
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Net filtration pressure
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What happens to excess filtrate that is not absorbed back into the venule-end of the capillaries or pericytic venules
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It is removed by the lymphatics.
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What is the difference between afferent and efferent lymphatics in terms of their content?
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Afferent: Same composition as interstitial (tissue) fluid
Efferent: Many lymphocytes in fluid, that have migrated through the tissues to the lymph nodes |
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Plasma proteins can flow through the lymphatic vessels T/F
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T
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Afferent lymph trunks do not run along side major veins T/F
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F
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Lymphatic vessels have valves T/F
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T
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The thoracic duct is a lymph vessel T/F
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T
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What vein does the thoracic duct empty into?
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The subclavian vein
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What's special about the subclavian vein wrt lymphatics?
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The thoracic duct empties into the subclavian vein
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Does protein content (and hence oncotic pressure) increase from efferent lymphatics to afferent lymphatics, or decrease
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Increase substantially (probably as a result of absorption of water and electrolytes by the vascular capillaries of the lymph nodes)
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