Microcirculation & Edema Flashcards
Functions of microcirculation
- Connection between arterial & venous side for transport of blood (close the circuit)
- Exchange of nutrients & metabolites, to maintain homeostasis
- Distribution of fluid between extravascular & intravascular compartments
Compare not-true capillaries & true capillaries
- Not-true capillaries are not desgined for exchange conduct blood rapidly from arterial to venous side, they are large capacitance vessels, larger than terminal arterioles. They are metarterioles, AV shunts & thoroughfare vessels, they are rich in SM & nerves have temp regukatory function.
- True capillaries are only desgined for exchange, arise from thoroughfare vessels & terminal arterioles, for every capillary arising from connecting vessel there is a precapillary sphincter, under local tissue control while muscle fibers before it are under neural control.
At rest, …..% of capillaries are inactive & closed
> 75
Fenestrated capillaries are found in ….., their fenestratioms are equal to …..
Endocrine glands, intestinal villi, glomerular membrane of kidney
20-100 nm in diameter
Mention site & functions of sinusoidal capillaries
Liver (allow oassage of plasma protein) Bone marrow (allow passage if RBCs)
Compare types of continuous capillaries (site/function)
- Skeletal, cardiac, smooth muscle veins, fenestrations are 10 nm in diameter, allow bulk flow of water & wtaer soluble ions.
- In brain, the capillaries are non-fenestrated with continuous endothelium there are tight junctions allow passage of small molecules.
GR: Blood velocity in capilkaries is extremely slow
Mention the speed
Due to large TCSA of capillary network, this slow flow is most appropriate for the essential function of capillaries which is exchange between capillary & tissue.
0.1-0.5 mm/sec
Mention how RBCs pass through capillaries
Squeeze as a single file with the center ahead of the edges (parachute shape).
GR: Capillaries withstand pressure
Due to their small radius accirding to Laplace law
…. Capillaries rupture easily
Dilated
… test measures capillary permeability
Hess
Define vasomotion, & its rate
It is defined as alternating closure and opening of capillaries according to metabolic activity, thus blood flows in certain capillaries and they close & blood shifts to other capillaries.
6-12 cycles/min
Mention mechanisms of vasomotion
Metabolic, myogenic, chemical & hormonal, nervous & temperature factors
Describe metabolic & myogenic factors
O2 lack and CO2 excess increases the number & duration of open phase of vasomotion, injection of high O2 blood decreases the vasomotion cyvles per minute & vice versa.
Pacemaker may be present in in smooth muscles of arterioles
…….cause VC, while ……cause VD of precapillar
Adrenimed
Substance P, bradykinin, histamine