-
WBC
Migrate into tissue via postcapillary venules
-
tunica intima
- innermost layer including the endothelial lining
- Like card enothelium, SUBendotheial CT & endothelia cells
- Internal elastic lamin in arteries, large veins
-
tunica media
- middle, muscular layer - pressure resisting
- Prominent in arteries
- elastic laminae (elastic arteries)
- EXTERNAL elastic laminae
- Pericytes- in cap & postcap venules
- circular
-
tunica adventitia
- supporting LCT layer
- longitudinal
- (Sm. m longit. in large vein)
-
Vasa vasorum
- blood vessels in adventitia, near media
- larger arteries and veins
-
Vessel's sm m. on walls
secretory and contractile
-
Elastic arteries (>1cm)
- Intimal subendothelium prominent
- Elastic laminae- recoil (diatole) maintains P and Q
- Aneurysm- loss of elastic tissue, loss diatole, thinner, prone to rupture
-
Muscular arteries
- Thin intima
- Well-defined internal elastic laminae
- Sometimes EXTERNAL elastic laminae- in between media & adventitia
-
Atherosclerosis
- Intima->bigger & bigger
- Atheromatous plaque, partial occlusion, plaque rupture, platelet aggregation, thrombus, infarction
-
Arteriole
- NO internal elastic laminae, some elastin seen
- precapillary sphincters (metarterioles)- blood flow to cap dec
- AV shunt- blood flow to cap incr (imp for thermoreg, bp)
-
Endothelial cells
- lines all blood vessels
- fascia adherens & fascia occludens
- anti-thrombogenic/coagulant
- angiogenesis- formation of new bv activated by VEGF, wound healing, tumors
- anti-angiogenesis-tumor regression (Avastin- anti-VEGF, treat cancers)
-
Pericytes
- supporting cell for cap, postcap venules instead of SMC
- contractile
- PDGF instead of VEGF
- Progentitor for wound fibroblast repair
-
Capillaries
Blood flow rate= 1% rate of elastic arteries
-
Continuous capillaries
- muscles, lung, nerve
- fascia occluden, fascia adherens- 10nm
- metabolite exchange through caveolae & pinocyotic vesicles
- BBB and blood-thymus barrier-> zonuka occludens
-
Fenestrated capillaries
- GI, endocrine glands, kidney
- 80-100nm channels- "slit membranes"
- intact/continuous basal lamina
- 100x exchange
-
Discontinuous or sinusoids
- liver, spleen, some endocrine glands
- Gaps between endothelial cells
- Attenuated basal lamina
- Fastest exchange
-
Veins
- 70% of blood
- small wall:lumen ratio
-
Venules
postcap venules become "leaky" in response to inflammtion->histamin increases vascular permeability
-
Large veins
Adventia has longitudinal smooth muscle- support for "hanging veins"
-
Lymphatic capillaries (central lacteals)
- Discontinuous endothelium
- Attenuated basement membrane
- NO pericytes
- lymph moves passively
-
Lymph return
- through thoracic duct and right lymphatic duct
- 3 layer wall, spiral smooth muscle in media
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