Capillary Dynamics and Interstitial Fluid Flashcards
The following area of the body have fenestrated capillaries (true or false):
The medial meniscus of the knee
False. Cartilage and epithelia have no capillary supply.
The following area of the body have fenestrated capillaries (true or false):
The ileum
True. The absorption sites of the gastrointestinal tract have fenestrated capillaries
The following area of the body have fenestrated capillaries (true or false):
The organum vasculosum of the laminae terminalis (OVLT)
True. The OVLT is one of the circumventricular organs, all of which are outside the blood brain barrier near the brainstem. The others are the posterior pituitary, median eminence of the hypothalmus, the area postrema and the subfornical organ
The following area of the body have fenestrated capillaries (true or false):
The spleen
False. The spleen and liver both have discontinuous capillaries.
The following area of the body have fenestrated capillaries (true or false):
The descending vasa recta of the kidney
False. The afferent capillaries of Bowman’s capsule are fenestrated but the descending vasa recta which accompanies the descending loop of Henle is non fenestrated with a facilitated transporter for urea. The ascending vasa recta is fenestrated so it may function as a reabsorption site for solutes.
In relation to capillary beds (true or false):
Reactive hyperaemia is due to vasodilatation caused by accumulation of metabolites
True. As well as metabolites accumulating, the increase in temperature and increase in CO2 generated all cause reactive hyperaemia.
In relation to capillary beds (true or false):
Parasympathetic vasodilator fibres innervate the vessels of the gastrointestinal tract
True. Parasympathetic fibres also innervate skeletal muscle and the capillaries of the skin and the coronary circulation.
In relation to capillary beds (true or false):
Substance P and bradykinin reduce capillary permeability
False. Both these cause vasodilatation of the pre capillary sphincter.
In relation to capillary beds (true or false):
Transit time of a resting capillary is 0.5 s
False. The minimum transit time is 1 s and a resting capillary typically has a transit time of 2 s.
In relation to capillary beds (true or false):
Reabsorption of interstitial fluid occurs in venules of 35 µm in diameter
False. Only venules up to 30 µ m take part in ultrafiltration.
The pressure in a capillary in the foot of a prone adult is 38 mm Hg at the arteriolar end and 19 mm Hg at the venular end. The interstitial pressure is -1 mm Hg and the colloid osmotic pressure 26 mm Hg in the capillary and 15 mm Hg in the interstitial space. What is the net force of filtration at the arteriolar end of the capillary?
A. 12 mm Hg into the capillary
B. 12 mm Hg out of the capillary
C. 28 mm Hg out of the capillary
D. 27 mm Hg out of the capillary
E. 28 mm Hg into the capillary
F. 8 mm Hg out of the capillary
C. Fluid movement Q = (pc-pi) – (?c-?i)
Hydrostatic pressure at arterial end is 38 + 1 (because the interstitial pressure is -1 so in fact it is almost adding to the hydrostatic pressure out of the capillary. The colloid osmotic pressure difference is 26 - 15 = 11, drawing fluid back into the capillary. Therefore net force of filtration is
39 - 11 = 28 mmHg out
Which of the following is most likely to explain the development of generalized oedema in a patient who is 1 week into their admission to intensive care with an episode of acute on chronic pancreatitis.
A. Vasodilatation secondary to systemic inflammatory response syndrome
B. Increased capillary pressure
C. Increased venous pressure
D. Increased interstitial protein concentration
E. Plasma protein deficiency
E.
In pancreatitis all the listed items will occur, particularly if the patient has been managed in a ward environment with imprecise fluid management. But it is the lowering of plamsa oncotic pressure which has the most profound effect on the balance of Starling forces in the peripheral capillary. Particularly in this case as the patient is likely to have preexisting low albumin due to the chronic pancreatitis.
Regarding capillary beds in the following organ (true or false):
The liver has fenestrated capillaries
False. Although the liver has gaps in the adjacent cells on electron-microscopy (sinusoid capillary) to allow protein molecules to pass, it is a type of continuous capillary. Cytoplasm of the cells have no fenestrations. Only the kidney and gut have fenestrated capillaries which allow solutes but not albumin to freely pass.
Regarding capillary beds in the following organ (true or false):
The blood brain barrier has aquaporin transporters to allow water to be transported across
False. The blood brain barrier does have carrier systems for glucose, thyroid hormones, nucleic acid precursors and amino acids.
Regarding capillary beds in the following organ (true or false):
Glomerular capillaries are 10 times more permeable to water than skeletal muscle capillaries
False. Glomerular capillaries are 50 times more permeable than systemic capillaries.
Regarding capillary beds in the following organ (true or false):
The distal colon has continuous capillaries
False. The colon is an absorption site so has fenestrated capillaries.
Regarding capillary beds in the following organ (true or false):
The lung has continuous capillaries with no gaps between cells
False. The lung has continuous capillaries but the gap junctions are not tight and water can pass through paracellularly.
The following occurs when blood passes through the systemic capillaries (true or false):
Haematocrit increases
True. Some intravascular water (15%) returns to the circulation via the lymphatics so increases the haematocrit.
The following occurs when blood passes through the systemic capillaries (true or false):
Vasomotion varies the flow between 0.2 and 2 cm/s
False. The flow in some capillaries is zero at any one time and the maximum flow is limited to 0.2 cm/s to allow effective exchange by diffusion to occur.
The following occurs when blood passes through the systemic capillaries (true or false):
The blood protein content increases
True. There is a concentration effect caused by less water being reabsorbed.
The following occurs when blood passes through the systemic capillaries (true or false):
Endothelin -1, serotonin and neuropeptide Y all cause relaxation of the precapillary sphincter
False. These polypeptides all cause vasoconstriction and reduce flow in the capillary.
The following occurs when blood passes through the systemic capillaries (true or false):
The red blood cells change shape as they pass through the capillary
True. Red blood cells change shape with the central section ballooning forward to create a thimble or parachute shape. They also increase in size associated with uptake of carbon dioxide in the periphery.
The following occurs when blood passes through the systemic capillaries (true or false):
The precapillary sphincters contract 2-3 times a minute, generating pulsatile flow in the capillary
False. The sphincters do cyclically contract and relax, but at a higher rate of 12 times a mininute, to generate pulsatile flow.
Regarding the velocity of blood flow (true or false):
It is higher in the capillaries than the arterioles
False. Velocity is 20 cm/s in the aorta and 0.1 cm/s in the capillary.
Regarding the velocity of blood flow (true or false):
Falls to zero in the descending aorta during diastole
False. Forward flow in the aorta continues in diastole when the reservoir of blood stored by elastic distention of the aorta is propelled forwards.
Regarding the velocity of blood flow (true or false):
It is higher in the veins than the venules
True. Flow in the veins is 5-15 cm/s whereas flow in the venules is 0.1-5 cm/s.
Regarding the velocity of blood flow (true or false):
Flow in the large veins is pulsatile
True. Transmitted pulsations from large arteries and the cardiac cycle in the right atrium transmit to large veins.
Regarding the velocity of blood flow (true or false):
Aortic flow velocity always exceeds arteriolar flow
True. Aortic flow is 20 cm/s and arteriolar flow 5-10 cm/s.
What percentage of total blood is held in each of these compartments at rest?
Capillary
Heart
Artery
Arteriole
Pulmonary circulation
Aorta
Large veins and vena cava
Capillary 5%
Heart 12%
Arteries 8%
Arterioles 1%
Pulmonary Circulation 18%
Aorta 2%
Large veins and vena cava 54%
