vasculature Flashcards
3 main layers of muscular artery (lumen outwards)
tunica intima
tunica media
tunica adventita
describe the structure of a capillary (layers)
endothelial cells
basal lamina - fibrous proteins supporting endothelium
pericytes
what happens to venules near a site of infection
become more permeable to leukocytes - allow to enter tissues for immune response
what facts affect vascular tone and act on only smooth muscle
noradrenaline - constrict
angiotensin II - constrict
adrenaline - B2 receptor = dilate
-pressure - increase=constrict (myogenic response)
what factors affect vascular tone and act on only endothelium
flow - vasodilate
what factors affect vascular tone and act on both smooth muscle and endothelium
- tissue metabolites: dilators. Cause endothelium to release NO and activate endothelium-dependent hypopolarisation (EDH)
- local hormones: constrict. autocoids
describe how an active complex is formed to cause muscles to contract
myosin light chain kinase + calmodulin bind to Ca2+.
phosphorylate myosin –> actin -> crossbridge cycle
describe how a phosphorylated myosin may be dephosphorylated
enzyme myosin phosphatase.
-activated by NO via. cGMP - promote relaxation
Ca desensitisation
what may inhibit the enzyme myosin phosphatase
agonists via. rho kinase = Ca sensitisation
contract
what is NO released by and when
in response to increasing Ca bradykinin ATP histamine H+ CO2 ACh
what does endothelium release to vasodilate/constrict
- prostacyclin (PGI2) - vasodilate and inhibit platelet aggregation
- endothelin - vasoconstrict
describe NO-mediated vasodilation
- NO enters smooth muscle
- activates guanylate cyclase which breaks down GTP –> cGMP
- cGMP activates Ca pump - Ca out of cells via. SERCA and PMCA (plasma membrane Ca ATPase)
- myosin dephosphatase - Ca desensitisation
- open K channels = hyperpolarise = VGCC close
- phosphodiesterase - stop breakdown of GMP
what is angiogenesis and what structure is involved
growth of new blood vessels
endothelium
layers of an arterial vessel
endothelial cells internal elastic lamina smooth muscle cells external elastic lamina tunica adventitia: blood vessel, collagen, symp nerves, fibroblasts
role of pericyte
regulate capillary diameter in CNS
what’s the relationship between pressure and venous volume
small changes in pressure/tone changes volume greatly
diameter of veins and composition
5mm
tunica media with sparce smooth muscle
what kinase does cGMP activate
protein kinase G
what is oxidative stress and what does it do
overproduction of reactive oxygen species
associated with CV disease
-cause contraction, raise BP
examples of reactive species
super oxide - O2-
hydrogen peroxide - H2O2
what do superoxides do
react with NO = peroxynitrate which prevents NO-mediated vasodilation
what is an alternative mechanism of vasodilation which uses cAMP
- activate B2, PGI2 and adenosine receptors on vascular SMC
- stimulates adenylate cyclase which synthesises cAMP –> PKA activate
- PKG and PKA= vasodilate
what are some acids released by endothelium to cause vasodilation
epoxyeicosatrieonic acids (EETS)
what do EETS do
activate K channels on SMC = hyperpolarisation = relax
released by endothelium
what is autoregulation
constant blood flow over wide range of pressures e.g. in renal, coronary, cerebral
what is autoregulation caused by
myogenic response
effects of flow on local conc of metabolites
how does the myogenic response keep change in flow to a minimum
slow constriction
how are the concentrations of metabolites prevented from building up
increase in metabolites = vasodilation influence.
- increases blood flow which washes out metabolites.
- redices dilation = increase tone and local resistance
what is metabolic hyperaemia
increased metabolism produces vasodilation factors.
important in cardiac and skeletal muscle
what is reactive hyperaemia and when does it occur
If local blood flow is cut off, metabolites build up which causes vasodilation until flow is resumed. Flow is enhanced after this to ensure all metabolites are washed out
static (isometric) exercise
what are the 3 types of endothelium and where is each found
- continuous - blood brain barrier (tight junctions)
- fenestrated - kidney, joints, intestinal mucosa
- sinusoidal - liver, bone marrow, spleen
5 routes across a capillary wall
-transcellular
-paracellular & fenestral
for larger lipophilic molecules:
-vesicular transport
-trans-endothelial channel
-wide intracellular gap
what creates a barrier to diffusion in a membrane
glycocalyx and narrow clefts between endothelial cells
-dependent on size of species
what route does water mainly flow though
intracellular clefts (paracellular)
what are the 3 most permeable substances
o2
h20
nacl
what are the 3 of the least permeable substances
glucose
INULIN
albumin
formula for the oncotic osmotic pressure
[blood plasma] - [interstitium] = 2.7-10 mmHg
what is the reflection coefficient
if it can get through the intracellular cleft
harder = higher coefficient
proteins have a high value 0.9
what is the starling eqn
net movement of fluid (Jr) is proportionate hydrostatic - (oncotic x reflection coefficient)
what happens to reabsorption when arterioles are contracted
reduce capillary hydrostatic pressure so reabsorption is more important.
reduce pressure
what happens to P(cap) - capillary pressure - during standing
lower extremities - increases
reflexes: cause arteriolar constriction so Pcap is reduced = compensate for rise in filtration
4 functions of lymphatic system
- preserve fluid balance
- transfer fat absorbed in small int to circulation
- transport foreign material to lymph nodes
- transport lymphocytes in blood
what pathway is in lymph capillaries and what is it driven by
intercellular clefts. one way entry
tissue compression
what’s a lymphangion and why are they important
a unit of lymph vessel between 2 valves
-each has a pacemaker to pump fluid forwards. afferent lymph trunks contain smooth muscle - contract
how much to lymphangions need to compress to avoid pumping
40-50mmHg
describe the Tavel of lymphocytes
blood –> lymph glands –> blood
what occurs at lymph nodes, and glands
- reabsorption of some lymph fluid (node)
- activation of lymphocytes (glands)
