20 Flashcards
which vessels act as the main site for exchange of substances between the blood and extracellular fluid
capillaries
what layers form the aorta and what is each layer made up of
tunica Adventitia (collagen and supported by external elastic lamina)
tunica media (smooth muscle, elastic tissue and collagen)
tunica intima (endothelial cells)
diameter of aorta
25mm
diameter of artery
4mm
diameter of vena cava
30mm
arteriole
30 micrometer
what are macro vessels
aorta artery vein vena cava arteriole
what are micro vessels
terminal arteriole (10 micrometer
capillary 8microm
venule 20 microm
how many layer make up the capillaries
3 single layer of endothelial cells
function of precapillary sphincter
open close vessels and can act as a shunt
what are arteriovenous anastomoses
a connection between an arteriole and a venule
arteriovenous malformation pathophys
tangles of abnormal blood vessels (nidus) in which the feeding arteries are connected directly to venous drainage system (with no capillary bed)
So
+that area is DEPRIVED of exchange (not enough O2 and nutrients will be exchanged)
high pressure goes to low pressure vessels… so can lead to aneurysm or haemorrhage
capillaries funciton
control BP
exchange of nutrients and O2
what are the three types of capillaries
continuous capillaries
fenestrated capillaries
discontinuous capillaries
is there smooth muscle in capillary walls
no
where are continuous capillaries found
skin
muscle
lung
CNS
where are fenestrated capillaries found
exocrine glands
renal glomeruli
intestinal mucosa
which is most common type of capillary
continuous capillaries
what links endothelial cells in continuous capillaries
tight junctions
what are caveolae
transport vesicles
what organs would need a continuous capillary with lots of cavelolae
skeletal muscle lung skin
what organs would need a continuous capillary with few cavelolae
CNS
which types allow free passage of proteins
discontinuous capillaries
what do continuous and fensetraed capillaries allow free passage of
water and ions (salt)
how do things go into capillaries
diffusion (liais soluble substances)
movement through intercellular clefts (water soluble stuff)
movement through fenestrations (water soluble substances)
transport via vesicles (pinocytic vesicles) or caveolae (large substances=
what does the amount of solutes able to be diffused depend on
area x concentration gradient x diffusion coefficient
what does the amount of solutes able to be diffused depend on
surface area x concentration gradient x diffusion coefficient
the rate of diffusion of a substance through any membrane is proportional to
the concentration difference between the two sides of the membrane.
why does blood move from blood to tissue
bc oxygen concentration is lower in tissue
what’s paracellular transport
transfer of substances across an epithelium by passing though the intercellular space between the cells (in kidneys)
what drive water movement across capillary endothelium
hydrostatic pressure
oncotic pressure
hydrostatic pressure is driving filtration at what end and why
arteriole end bc hydrostatic pressure is greatest
hydrostatic pressure is driving reabsorption at what end and why
venus end bc hydrostatic pressure is lowest
what’s the normal hydrostatic pressure of interstitial fluid
0
what substances set the capillary colloid osmotic pressure and how much is it
plasma proteins
26mmHg
what’s the interstitial fluid colloid osmotic pressure
very small, 1mmHg
net filtration pressure (NFP) equation
(HPc - HPif) - (OPc - OPif)
HPv - HPif) - (OPv - OPif
HP in arterial end
OP in arterial end
35 mmHg
26 mmHg
HP in venous end
OP in venous end
17 mmHg
26 mmHg
HP interstitial fluid
OP interstitial fluid
0 mmHg
1 mmHg
what’s the NFP in venous end
-8 mmHg
what’s the NFP in arterial end
10 mmHg
why does fluid leave capillaries at arterial end
because of hydrostatic pressure
why does oncotic pressure stay the same across capillaru
bc proteins don’t normally leave capillaries
where does surplus fluid go
lymphatic system
how many litres of plasma pass though capillaries per day
4000L
how much plasma is filtered
0.1 0.2%
how much fluid moves from capillaries to interstitial fluid every day
4-8 L
key characteristics of lymphatic capillaries
valves so lymph travels away from tissue
made up of endothelium with large intercellular gaps surrounded by permeable BM
what do lymph capillaries do with excess fluid
send it to circulation via lymph nodes
send it to circulation via subclavian artery
whats an oedema
increased volume in the interstitial compartment that leads to tissue swelling
symptoms of oedema
swollen puffy ankles feet legs
shiny stretched or red skin
where do systemic oedema fist occur
in lower region of body like ankles
how to physical exam oedema
put pressure in area for 5 10 secods
you get pitting oedema like it doesn’t bounce back
what can be a Benin cause of what could look like an edema
venous pressure build-up in the legs afters tanning for too long
what causes oedema
increased secretion or filtration of fluid into the interstitial space or impaired removal of this fluid
what determines the amount of interstitial fluid
fluid homeostasis
factors precipitating oedema
- increased capillary hydrostatic pressure
- decreased plasma oncotic pressure
- increased capillary permeabiliity
- lymphatic obstruction
give an example for increased hydrostatic pressure
in Heart failure
venous pressure increases so driving force into ISS decreases so reabsotrion decreases and fluid buildsup
give an example for the cause of decrease plasma oncotic pressure
Kwashiorkor
main factor that regulates fluid balance
plasma oncotic pressure
whats Kwashiorkor
sever malnutrition deficiency in dietary protein lack of proteins in blood and tissues reduced OPs pitting edema water retention in gut
give an example for increased capillary permeability
vascular damage burn trauma
water flows more freely
may allow more molecules to pass through so
OP decreases
what causes primary lymphedema
genetic cause or malformation of lymphatic system
what causes secondary lymphedema
damage to lymphatic system due to surgery or radiation tissue injury
whats more common primary or secondary lymphedema
secondary
treatments for oedema
drugs that promote loss of sodium and water
diuretics
either osmotic diuretics (increase water excretion= or loop diuretics (increase sodium excretion, natriuresis=
