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HISTOLOGY OF CIRCULATORY SYSTEM II
T- TUBULES & SARCOPLASMIC RETICULUMLess regular arrangementT- Tubules are more numerousAt level of Z- lineDIAD
CONDUCTING SYSTEMMitochondria more numerousLipofuscin pigment granules
CARDIAC FIBROUS SKELETONSeptum membranaceumTrigona fibrosaAnnuli fibrosa
Composed of dense connective tissue
CONDUCTING SYSTEM
CIRCULATORY SYSTEMBLOOD VASCULAR SYSTEMLYMPH VASCULAR SYSTEM
COMPONENTSHEARTARTERIESCAPILLARIES
LYMPHATIC CAPILLARIESLYMPH VESSELSLYMPHOID ORGANS
DIVISIONS
MACROVASCULATURE: > 0.1µm, large arterioles, muscular & elastic arteries, muscular veins
MICROVASCULATURE: < 0.1µm, arterioles, capillaries, post capillary venules
Exchange vessels
TISSUE COMPONENTSEndotheliumMuscular tissueConnective tissue (Elastic elements)
STRUCTURAL PLAN OF BLOOD VESSELS
TUNICA INTIMAEndotheliumBasal laminaSub endothelial connective tissueInternal elastic lamina
TUNICA MEDIASmooth musclesElastic lamellae, reticular fibersGround substance elementsExternal elastic lamina
TUNICA ADVENTITIACollagen & elastic fibers
VASA VASORUMVessels of vesselsArterioles, capillaries, venules in
adventitia
INNERVATIONSympathetic fibers (norepinephrine)VasoconstrictionArteries in Skeletal Muscles- cholinergic
vasodilator fibers
ENDOTHELIUM: Semi permeable barrier
Monitor bidirectional exchangeNonthrombogenic surface;
heparin, tissue plaminogen activator & Von Willibrand factor
Regulate Vascular tone & Blood flow; Contraction: endothelin 1 & ACE Relaxation: NO & Prostacyclin
Inflammation & Local Immune response; Adhesion of WBCs, expression of P-Selectin, Weibel Palade
BodiesGrowth Factors;
VEGF in Vasculogenesis, Angiogenesis, role of Angiopoeitins
LipolysisProduce Vasoactive substances
Thrombosis, emboli (Role of TPA)
VASCULAR SMOOTH MUSCLESPresent in all vessels EXCEPT capillaries
and post capillary venulesEnclosed in basal lamina & connective
tissueArranged helicallyConnected by gap junctions
VASCULAR CONNECTIVE TISSUE
Variable proportionCollagen, IV, III, IElastic fibersGround substance; heterogenous gel
Medical ApplicationArteriosclerosis Thickening of walls of small arteriesMonkeberg’s calcific sclerosisAtherosclerosis
LARGE ELASTIC ARTERIEST. INTIMAIntima is thicker; smooth muscles in sub
endothelial connective tissueInternal elastic lamina, though present not
prominent
T. MEDIAConcentric lamellae of elastic fibers (40-70)Reticular fibers, smooth muscles
T. ADVENTITIALess developed
Arterial Sensory ReceptorsCarotid & Aortic Sinus:
BaroreceptorsTunica Media is thin--- allows distensionAfferent impulses via 9th cranial nerveVasomotor center in brainEfferent adjust lumen to control BP
Carotid & Aortic Bodies:Chemoreceptors Para ganglia with rich capillary networkGlomus type I cells; dense core granules containing
Dopamine, AchSupported by Satellite Type II cellsIon channels in Glomus cells respond to Low Oxygen,
High CO2 or AcidosisAfferents to brain efferents to cvs or respiratory
system
MEDIUM SIZED, MUSCULAR ARTERIEST. INTIMASubendothelial layer thinProminent internal elastic lamina
T. MEDIASmooth muscles- 40 layersElastic fibers
T. ADVENTITIAConnective tissue, vasa vasorum,
lymphatics
SMALL ARTERIES & ARTERIOLES<0.5mm lumenThin subendothelial connective tissueInt. elastic lamina absent in small arteriolesT. Media: smooth muscle layerAdventitia is thin
Hypertension
CAPILLARIESDiameter : 5-7 µmSingle layer of endothelium; permit metabolic
exchangeFunction in groups- Capillary BedsRichness conforms to metabolic activity of
tissueStructure and pulsatile flow of blood through
capillaries and thoroughfare channel.
TYPES
ContinuousFenestratedSinusoidal
CONTINUOUS CAPILLARIESNo fenestrations, complete basal laminaPinocytic vesiclesLocation:Muscles, nervous tissue, exocrine glands
FENESTRATED CAPILLARIESTranscellular openings (80nm)Limited by cell membraneCovered by diaphragm ( thinner than cell
membrane, proteoglycans)In endocrine glandsKidneys etc
SINUSOIDAL CAPILLARIESDiameter 30-40µmEndothelial cells discontinuous layerFenestrations without diaphragmIncomplete basal laminaMacrophagesFound in liver, hematopoietic organs
PERICYTESCells at periphery of continuous capillariesenclosed in own basal laminaMesenchymal originActin, myosin– contractile propertiesRole in repair process
Diabetic Microangiopathy