Blood vessels (Histology) Oct31 M3 Flashcards
efferent vessels def
arteries (supply blood)
afferent vessels def
veins (drain blood)
lymph composition
plasma enriched with Igs and lymphocytes produced by lymphatic organs
arterial vessels 4 types
large (elastic) arteries
muscular arteries
arterioles
metarterioles
venous vessels 4 types
postcapillary venules
venules
medial or small size veins
large veins
where large veins and medium small sized veins located
parallel to muscular arteries and large arteries
3 layers of muscular arteries and middle sized veins + gross composition
intima (endoth and CT), media (SM cells) and adventitia (dense CT)
3 layers of intima in musculary artery
- endothelial (squamous simple epith)
- Subendothelial layer (thin layer of CT, mainly ECM, reticular and elastic fibers too)
- IELM (internal elastic limiting membrane or internal elastic)
IELM function and appearance
elastic membrane covers artery like a sleeve. not a fiber. appears wavy bc of retraction at fixation
Intima layers in veins
endothelium and bit of subendothelial layer (CT) (NO IELM)
Media composition
layers of SM
media diff between arteries and arterioles
arteries: 4-26 SM layers
arterioles: 1-2 SM layers
media in veins and diff with arteries
1-2 layers of SM and cells separated by CT
adventitia charact
dense irregular CT , collagen fibers, etc.
vasa vasorum def
small blood vessels within wall of vessels
where vasa vasorum found
in adventitia of large arteries and large veins
how nutrients supply is done in large arteries and veins
top half supplied by lumen
bottom half supplied by vasa vasorum
diagnostic tool to separate arteries and veins (2)
Presence of IELM
Thickness of media
appearance of IELM on longitudinal section and real characteristic
appears to have openings and fenestrations but isn’t broken in fact. is continuous
cells found in adventitia
fibrocytes
special structure found in veins of very low extremities and normal functioning
valves part of the intima projecting in the lumen. Normally, closed
varicose veins def and risk factors
valves in lower extremities stay open. Associated with what: high BP, obesity, lack of movement, smoking, pregnancy, genetic predisposition
valves in lower extremities come from what
are part of intima. endothelial cells with bit of subendothelial layers project in lumen
subendothelial layer of intima something particular
can be present, absent or can be very thin
something special found in media of elastic arteries
elastic membranes (along with the SM)
how adventitia changes more distally in CV system
becomes thinner (and no vasa vasorum)
elastic artery morphology and histology
endoth layer, subendoth layer, IELM, other elastic membranes not called IELM. SM between these. adventitia. SM and elastic membranes form concentric circles
large veins like VC. composition
endoth layer, subendoth, no IELM. no elastic membranes, thinner media
middle size veins how media differs from large veins
discontinuous layer of SM
how elastic membranes of large arteries appear on longitudinal section
- can connect between one another
2. appear interrupted but are not. are continuous, not broken.
how SM cells of large arteries differ from SM cells of muscular arteries
in large arteries, run in diff directions (disorganized)
in musc. arteries, organized
stain to see elastic membranes of large arteries well
Verhoeff Hematoxylin
SM cells behavior in large veins + appearance
run in diff directions. look more purple. separated by bit of CT
arterial vessel with 3 SM layer considered what?
transition between muscular artery and arteriole
Diff in elastic fibers between arteries and arterioles
No IELM in arterioles, only elastic fibers running in parallel with length of the arteriole
SM configuration in arterioles
runs perpendicular to arteriole direction, on their circumference
how SM appears on longit cut and cross section of arteriole
SM cut in cross section on longit cut of arteriole.
SM cut longit. on cross section of arteriole
how flow and volme of blood compares between aorta and capillaries
800 times greater volume in capillaries
1000x slower flow in capillaries (0.3 vs 320 mm per sec)
functions of capillaries (5)
Exchange, nutrition, thermoregulation, BP regul, inflammation
capillaries classification
permeable (fenestrated or sinusoid) and impermeable (continuous)
sinusoid capillaries charact
no BM, only supported by reticular fibers
fenestrated or continuous capillary charact.
can’t differentiate without EM.
postcap venule charact. and how ressembles capillaries
endoth layer (1 cell), like cap., diameter 10-15 microns vs 8 for cap. may have cells called pericytes
pericytes what they do in postcap venule
contractile element that isn’t SM
epithelial junction found in both fenestrated and continuous capillaries
zonula occludens (gap junction, synonym)
modes of transport through continous (permeable) capillaries (3)
- endocytosis in lumen, exocytosis in ECF
- pores closed and that open when two vesicles fuse. small molecules can pass
- clathrin mediated vesicles that behave like endo and exocytosis
modes of transport through fenestrated capillaries (4)
3 modes of continuous caps + openings and windoes sealed by small diaphragms where albumin may pass
sinusoid capillaries found where
spleen and liver
continuous capillaries found where
nervous tissue, skeletal, cardiac, SM, skin, lung, lymphatic organs
fenestrated capillaries location
intestinal mucosa, pancreas, salivary glands, endocrine glands, renal glomerulus
particular function metarterioles may accomplish
may act as sphincters that close in case of hemorrhage. blood then goes to venous circul. via anastomosis
4 fcts of endothelium of all CV system
- permeability
- metabolic
- prod of vasoactive substances
- anti-thrombogenic function
what endothelium lets through (permeability)
lipids
endothelium: 2 metabolic functions
- enzymes on surface convert angiotensin 1 to angiotensin 3
- inactivation of bradykinin (which can make SM contract), serotonin, PGs, NE, etc.
endothelium: 2 vasoactive substances produced
- endothelin: contraction of SM
- NO: relaxation of SM
why endothelium has anti-thrombogenic function
stops platelets from touching ECM and forming clot
anti-thrombogenic effect of endothelium: importance in atherosclerosis
atherosclerosis (macrophages accum, etc.) pushes on artery wall. advanced stage, endothelium broken and clot can form
where lymphatic vessels pass
in CT containing lymph
what makes up lymphatic vessels AT LUMEN
very thin endothelial cells without occluding and gap junctions
BM or no BM in lymphatics
no BM around endothelium
lymphatics: what endothelial cells attach to
anchored to CT fibers (type 1 and type 3 collagen + elastic fibers)
special structure sometimes found in small or large lymphatics
valves (folds of the wall projecting in lumen)
large lymphatics like thoracic duct: other tissue composing their wall
SM cells
blood cell type not found in lymph
RBCs
