Microcirculation & Oedema Flashcards
how do u describe tunica intima?
single layer of endothelial cells: simple squamous epithelial cells.
describe structure of capillary
site for what?
capillaries are know as what?
- single layer of endothelial cells
- no smooth muscle
- held together by tight junctions
- surroundered by basement membrane (what the endothlial cells rest on)
- site for: exchange of nutrients and waste products between circulation and intersitiual fluid that surrounds cells
- capillaries are known as exchange vessles
what is anatomy of capillary bed?
what are precapillary sphincters made from?
what is role of ^?
precapillary sphincters:
- bands of smooth muscle
- can adjust bloodflow through capillary bed - e.g. when they close, they can make arteriovenouse anastamoses
what are arteriovenous malformations?
- when feeding arteries are connected dircetly to venous system (i.e. abscence of capillary bed)
- can cause bleeding / haemorrhage due to high pressure
what distinguishes capillaries from arterioles?
arterioles have smooth muscle, capillaries do not
what are the three types of capillaries?
- continous capillary
- fenestrated capillary
- discontinous / sinusoidal capillary
describe structure of continous capillaries (2)
what can diffuse through em?
what are the two subdivisions and where found?
- sealed endothelium
- tight junctions
- pinocytic vesicles
- allow movement of water and ions
subdivisions:
- those with numerous transport vesicles (caveolae): skeletal muscles, lungs, gonads and skin
- those with few vesicles: CNS / bbb
describe structure of fenestrated capillary? (3)
what do they allow transport of?
where found?
- continous / closed basal lamina
- small pores in endothelial cells
- tight junctions
- pinocytic vesicles
- transport: free passage of salts and water. plasma –> tissues
- location: tissues specialised for bulk fluid exchange - exocrine glands, intestines, pancrease & glom. of kidneys
sinusoidal / discontinous capillaries: i) structure, ii) locations & iii) allow transport of what?
structure:
- special fenestrated endothelial cells
- **discontinous basal lamina
- **lack pinocytic vesicles
allow transport of:
- **red & white blood cells
- serum proteins**
locations:
- **spleen
- liver
- bone marrow**
where do u find each of the different types of capillaries?
- *discontinous**:
- spleen
- liver
- bone marrow
- *fenestrated:**
- exocrine glands
- intestines
- pancreas
- glom. of kidneys
- *continous:**
1. those with numerous transport vesicles (caveolae): skeletal muscles, lungs, gonads and skin
2. those with few vesicles: CNS / bbb
what are the 4 methods of movement through capillary endothelial cells?
what does diffusion through capillaries depend on? (3)
what is the diffusion coeffcient like for:
a) small, lipid soluble molecules
b) lipid insoluble & larger molecules
-
diffusion:
- depends on density of capillaries (high: large SA for exchange & short distance between each cap)
- concentration gradient
- diffusion coefficient
small, lipid soluble molecules
molecules that can diffuse across capillaries:
1.o2
2 co2
3. anaesthetics
lipid insoluble & larger molecules:
depends on the characteridtic of the capillary wall:
i) continous capillaires = limited passage
ii) fenestrated / discontinous = faciliate movement of large molecules
(diffusion is detemined by which law?)
(flicks law: amount moved = area x conc gradient x diffusion coefficient)
what is paracellular diffusion?
e.g. of where occurs?
Paracellular transport refers to the transfer of substances across an epithelium by passing through the intercellular space between the cells.
e.g. kidneys
what are caveolae?
caveolae: specialised pits that undergo endocytosis
which two factors determine the movement of water across capillary endothelium (4)
what can u calculate using these^?
- *1. hydrostatic pressure**
i) HPc: hydrostatic pressure in capillary (changes depending where - arteriol end (33 mmHG) > venous end (17mmHg))
ii) HPif: Hydrostatic pressure in intersitial fluid (usually 0) -
2. oncotic pressure: (**Oncotic pressure, or colloid osmotic-pressure, is a form of osmotic pressure induced by the proteins, notably albumin, in a blood vessel’s plasma (blood/liquid) that causes a pull on fluid back into the capillary)*
i) OPc: capillary colloid osmotic pressure - normally: 26 mm Hg (higher conc of protein (esp albumin in blood - fluid is reabsorbed back into blood, which causes pressure )
ii) OPif: intersititial colloid osmotic pressure - 1mmHg
can calculate: Net filtration pressure
youtube.com/watch?v=rPWf43lYcBU
how do u calculate net filtration pressure?
NFP = (HPc - HPif) - (OPc - OPif)
Net filtration pressure at arterial end / venous end? what does it mean occurs here?
within capillary bed: what is happening at a) arterial end b) venou end?
a) arterial end: filtration
b) venous end: absorbtion
= starling hypothesis
structure of lymphathic capillaries? (5)
- endothelial lining
- large intercellular gaps
- permeabmle basement membrane
- end as blind sacs within tissues
- one way valves
why do have lymph fluid?
bc not all fluid is reabsorbed in capillary beds - so need drainage back
Functionally, the lymphatic vascular system runs in parallel to the blood venous system, in that both return fluids centrally (see Figure 2). Lymphatic vessels carry lymph, which is largely water gathered from interstitial tissue spaces. Fluid appears in the interstitial spaces because blood capillary walls are somewhat leaky, admitting part of the aqueous component of blood, along with some proteins.
where are lymphatic capillaries in relation to blood capillaires?
in close association / proximity
describe water movement in body in lymph system
water movement is in continual flux
how much lymph is returned to circulation a day? what happens if this is maintained correctly?
2/4L lymph returned to circulation a day: if wrong = oedema
what is oedema?
what are symptoms?
oedema: increased volume in the interstitial compartment leading to tissue swelling (aka fluid retention)
- *symptoms**:
- swollen / puffy ankles , feet or legs
- shiny, stretched or red skin
how can u distinguish oedema vs other forms of swelling?
if pitting oedema produced: = oedema -> apply firm pressure and it doesnt bounce back
explain the 4 main factos that cause oedema
-
increased capillary hyrdostatic pressure
- venous pressures become elevated (e.g. through gravitational forces / heart failure)
- this reduces the hydrostatic pressure gradient
- reduces reabsorbtion from interstitial fluid back into capillary
- *2. decrease in plasma oncotic pressure**
- decreases the pressure driving fluid back into capillary
- reduces reabsorbtion
- *3. increased capillary permeability**
- allows more water to leave cap
- also reduces the oncotic pressure different by allowing protein to leave the vessel more easily
4. lymphatic obstruction
what are the two types of lymph obstruction / lymphoedema?
primary: genetic cause
secondary: damage to lymphatic system (e.g. surgery, elephantiasis - worm infection, tissue injury)
what can cause:
- increased capillary hydrostatic pressure?
- decrease in plasma oncotic pressure:?
- increased capillary permeability: ?
4. secondary lymphoedema:
- increased capillary hydrostatic pressure: heart failure
- decrease in plasma oncotic pressure: hypoproteinemia (less proteins in blood). e.g. malnutririon (Kwashiorkor) or liver disease
- increased capillary permeability: vascular damage (burns / trauma / inflammation)
4. secondary lymphoedema: surgery, elephantiasis - worm infection, tissue injury
how can u treat oedema?
- treat underlying disease that causes oedema
- treat oedema itself: diuretics (loop or osmotic)
