Capillaries/Lymphatics

Question 1

Metarterioles

Answer 1

Shunts for blood flow that bypass capillaries during low metabolic activity

Question 2

Pericytes

Answer 2

Contractile cells that form sphincters - open during high metabolic activity to allow blood to true capillaries instead of metarterioles

Question 3

4 Mechs of Exchange Across Capillary Wall (& what follows them)

Answer 3

Direct diffusion through endothelial cell membranes - O2/CO2
Diffusion through spaces b/w endothelial cells - Small, membrane impermeant molecules like glucose (except in brain)
Transport across membranes via pinocytosis
Transport via specialized transport prots (like glucose in brain)

Question 4

Glycocalyx

Answer 4

Lines lumenal side of capillary and prevents movement of prots across endothelial cells. Also causes fluid movement in and out of capillaries to have a nonlinear relationship w/ pressure

Question 5

Starling Equation of Transcapillary Movement

Answer 5

Net filtration rate = K*[(Pc - Pi) - (pic - pii)], where K is ultrafiltration coefficient, P is hydrostatic pressure, and pi is oncotic pressure. (c and i are capillary and interstitial fluid)

Question 6

Oncotic Pressure

Answer 6

Osmotic pressure component exerted by prots that do not readily cross capillary wall

Question 7

Forces Promoting and Opposing Fluid Movement out of Capillary

Answer 7

Hydrostatic pressure vs. oncotic pressure

Question 8

Excess Filtration Negative Feedback

Answer 8

It increases ISF volume, which in turn increases ISF hydrostatic pressure inhibiting more filtration. Also, that dilutes prots in ISF so there’s less interstitial oncotic pressure, also inhibiting filtration

Question 9

Opening of Lymphatic Capillaries

Answer 9

Collagenous fibers extend from ext. surface of endothelial cells into surrounding tissue, so when ISF accumulates, they exert traction on those cells to pull them and increase lumenal diameter

Question 10

4 Conditions -> Increased Likelihood of Edema

Answer 10

Increased hydrostatic pressure in capillaries caused by elevated venous pressures
Reduced capillary oncotic pressure
Increased capillary permeance to proteins
Blockage of lymphatic drainage

Question 11

3 Things that Promote Angiogenesis

Answer 11

VEGF
Low pH
NO

Question 12

VEGF Prot and R family

Answer 12

VEGFR-2 Promotes angiogenesis and 3 promotes lymphangiogenesis. VEGFC activates both