Circulatory notes - Summary of Advanced Histotechnology lecture, taught by Donna Smeeton PDF

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Circulatory  System  Summary  NotesThe  circulatory  systems  mediate  the  continuous  movement  of  all  body  fluids.  The  circulatory  systemincludes  both  the  blood  vascular  system &nbs...

Description

1" " Circulatory+System+Summary+Notes+ +

+ The"circulatory"systems"mediate"the"continuous"movement"of"all"body"fluids."The"circulatory"system" includes"both"the"blood"vascular"system"and"the"lymph"vascular"system"" Principal+function:"the"transport"of"oxygen"and"nutrients"to"the"tissues,"and"transport"of"carbon"dioxide" and"other"metabolic"waste"products"from"the"tissues" • Also"involved"in"temperature"regulation"and"the"distribution"of"molecules,"such"as"hormones," and"cells,"such"as"those"of"the"immune"system" • Two"functional"components:"blood"vascular"system"and"the"lymph"vascular"system" " Blood+vascular+system:"consists"of"the"heart,"major"arteries,"arterioles,"capillaries,"venules"and"veins."" "–"is"a"circuit"of"vessels"thru"which"blood"flow"is"initiated"by"continuous"action"of"a"central"muscular" pump,"the"heart." • The"arterial"system"provides"a"distribution"network"to"the"tiny"peripheral"microcirculation,"the" capillaries"and"postAcapillary"venues,"which"are"the"main"sites"of"interchange"of"gas"and"metabolite" molecules"between"the"tissues"and"the"blood."The"venous"system"carries"blood"from"the"capillary" system"back"to"the"heat."" • Main"function"–"deliver"oxygenated"blood"to"cells"and"tissues"and"to"return"venous"blood"to"the" lungs"for"gaseous"exchange" " The+Heart:+ " Made"up"of"three+basic+layers"similar"to"that"of"the"blood"vessels:" • Endocardium"(tunica"intima"equivalent),"" • Myocardium"(tunica"media"equivalent)"and"" • Pericardium"or"called"epicardium"(tunica"adventia" equivalent)."" " Endocardium"Ainner"(Tunica'Intima)"–"lines"the"heart" • Has"a"surface"layer"of"flattened"endothelia"cells"supported"by"a" fibrous"layer,"containing"variable"amounts"of"elastic"tissue," which"merges"with"the"collagen"fibres"surrounding"the"adjacent"cardiac"muscles"and"larger"Purkinje" fibres." + MyocardiumAmiddle"(Tunica'media)"made"up"of"cardiac+muscle"(striated,"involuntary)""

2" " Is"the"thickest"of"the"tunics"of"the"heart"and"consists"of"cardiac"muscle"cells"arranged"in"layers" that"surround"the"heart"chambers"in"a"complex"spiral."" • High"capillary"network"–"a"reflection"of"the"high"and"constant"oxygen"demand"of"the" myocardium,"particularly"the"left"ventricle" Epicardium"(visceral"pericardium)"–"outer"covering"(Tunica'Adventitia)A"consisting"of"simple"squamous" epithelium"A"mesothelium" 0 Pericardium"–"sac"that"contains"the"heart"(Dense"sheet"of"fibrocollagenous"tissue,"which"also" contains"elastic"fibres)" 0 " " •

""""""""""""" + Heart+Valve:"consists"of"leaflets"of"fibroelastic"tissue,"the"surfaces"covered"by"a"thin"layer"of" endothelium" " Muscle+review:"Cardiac"muscle"–"found"only"in"the"heart,"muscle"fibres"are"striated"and"they""are" involuntary" • Cylindrical,"primarily"located"in"the"walls"and"septa"of"the"heart"and"the"walls"of"the"large"vessels" attached"to"the"heart"(aorta"and"pulmonary"truck)" • Exhibit"crossAstriations"as"a"result"of"the"regular"arrangements"of"acting"and"myosin"filaments" • In"contrast"to"skeletal"muscles,"cardiac"muscle"fibres"exhibit"only"one"or"two"central+nuclei,"are" shorter,"and"are+branched+ • The"nuclei"are"clearly"seen"as"central"when"cardiac"muscle"is"cut"transversely"(XAsection)+ • Autonomic"nervous"system"innervates"hears"and"influences"heart"rate"and"blood"pressure+ • The"terminal"ends"of"adjacent"cardiac"muscle"fibres"show"characteristic"and"denseAstaining"endA toAend"junctional"complexes"called"intercalated+disks."" o The"discs"are"special"attachment"sites"that"cross"the"cardiac"cells"at"irregular"intervals"in" step"like"fashion."Located"in"the"intercalated"disks"are"the"gap"junctions"the"enable"ionic" communication"and"continuity"between"adjacent"cardiac"muscle"fibres" + Histology+of+blood+vessels+ • •

The"tunica"intima"is"the"inner"lining,"consisting"of"endothelium,"supported"by"a"basement"membrane" and"a"relatively"thin"layer"of"supporting"connective"tissue." The"tunica"media"is"the"middle"muscular"and/or"elastic"layer,"containing"smooth"muscle"and"elastic" tissue"in"varying"proportions."

3" " The"muscular"content"exhibits"the"greatest"variation"from"one"part"of"the"system"to" another."For"example"it"is"totally"absent"in"capillaries"but"comprises"almost"the"whole"mass" of"the"heard."Blood"flow"is"predominantly"influenced"by"variation"in"activity"of"the"muscular" tissue." The"tunica"adventitia"is"the"outer,"fibrous"connective"tissue"layer." """ Nervous"tissue"is"generally"inconspicuous"in"blood"vessels"but"serves"to"regulate"smooth"muscle" function"and"to"mediate"pain"sensation." The"tissues"of"the"thick"walls"of"large"vessels"(e.g."aorta)"cannot"be"sustained"by"diffusion"of"oxygen" and"nutrients"from"their"Lumina,"and"are"supplied"by"small"arteries"(vasa+vasorum)"which"run"in"the" tunica"adventitia"and"sends"arterioles"and"capillaries"into"the"tunica"media" o

• • •

" "

Layers of the blood vessels – Tunica intima, tunica media and tunica adventitia

" " " Arteries+ • Carry"blood"with"nutrients"and"oxygen,"to"the"tissues" • Divided"into"three+types:"(elastic,"muscular"and"arterioles)" • Large"or"elastic"arteries,"medium"to"small"muscular"arteries,"small"arterioles" §฀ Arteries"that"leave"the"heart"to"distribute"the"oxygenated"blood"exhibit"progressive" branching."Which"each"branching,,"the"luminal"diameters"of"the"arteries"gradually" decrease,"until"the"smallest"vessel,"the"capillary"is"formed" " Structural+plan+of+arteries:+contains"three"concentric"layers"or"tunics"(same"as"heart"muscle)"–"" • Innermost+layer+–+tunica+intima"–"composed"of"a"simple"squamous"epithelium"called"endothelium"" • Middle+layer+–+tunica+media"–"composed"primarily"of"smooth"muscle"fibres."Interspersed"among"the" smooth"muscle"cells"are"variable"amounts"of"elastic"and"reticular"fibres."In"these"arteries,"smooth" muscles"produce"the"extracellular"matrix"

4" " •

Outermost+layer+–+tunica+adventitia"–"composed"mainly"of"collagen"and"elastic"connective"tissue" fibres"(mainly"type"1"collagen)"

" •

•

The"largest"arteries,"such"as"the"aorta"and"its"larger"branches,"have"a"tunica"media"dominated"by" elastic"tissue.""The"elasticity"conferred"by"elastin"allows"these"elastic+arteries"to"smooth"out"the" sharp"changes"in"blood"pressure"resulting"from"the"pumping"heart." Most"arteries"are"muscular+arteries,"with"a"media"dominated"by"smooth"muscle.""But"elastin"is"also" a"substantial"component."

" Elastic+arteries"are"the"largest"blood"vessels"in"the"body"and"include"the"pulmonary"truck"and"aorta.."The" walls"of"these"vessels"are"primarily"composed"of"elastic"connective"tissue"fibres."These"fibres"provide" great"resilience"and"flexibility"during"blood"flow.""" • Tunica+intima+–"Relatively"thick,"it"consist"of"a"lining"endothelium"with"its"basal"lamina,"a" subendothelial"layer"of"connective"tissue"and"a"layer"of"elastic"material,"the"internal"elastic" membrane"(lamina)."" • Tunica+media+–"is"the"thickest"of"the"three"layers."It"consists"of"sheets,"or"lamellae,"of"elastic" material"with"intervening"layers"comprised"of"smooth"muscle"cells,"collagenous"fibers,"and"ground" substances."" • Tunica+adventitia+–"is"a"connective"tissue"layer,"relatively"thin,"usually"half"than"the"thickness"of"the" tunica"media.""

"""""""""""""""""""""""""""""""""""""""""" " " The"large"elastic"arteries"branch"and"become"mediumIsized+muscular+arteries,"the"most"numerous" vessels"in"the"body."" " Medium+(Muscular)+arteries+–"may"control"the"affluence"of"blood"to"the"organs"by"contracting"or" relaxing"the"smooth"muscle"cells"of"the"tunica"media."" • Tunica+intima+–"contains"a"lining"of"endothelial"cells"sitting"on"an"elastic"lamina" • Tunica+media+–"contains"smooth+muscle+cells,"collagenous"fibers"and"relatively"little"elastic"material."" • Thickest"layer"" • Tunica+adventitia+–"is"a"connective"tissue"layer,"relatively"thin,"usually"half"than"the"thickness"of"the" tunica"media.""

5" " §฀

In"contrast"to"the"walls"of"elastic"arteries,"those"of"muscular"arteries"contain"greater+amounts+ of+smooth+muscle+fibres.+ +++++++++++++++++

"""""""""""""""""""""""""""""""""""""""""""""""""" "" " Small+arteries+and+arterioles+–"are"arbitrarily"distinguished"from"one"another"by"the"number"of"smooth" muscle"cells"in"the"tunica"media,"although"there"are"other"differences"as"well."" • Small+arteries"A"may"have"up"to"8"layers"of"smooth"muscle."" • Arterioles"–"has"one"or"two"layers"of"smooth"muscle"cells"in"the"tunica"media"" §฀ Arterioles"deliver"blood"to"the"smallest"blood"vessels,"the"capillaries."These"connect" arterioles"with"the"smallest"veins"of"venules."" "

+ + + Structural+plan+of+veins:"capillaries"unite"to"form"larger"blood"vessels"called"venules"and"then"increase"in" size"to"veins"(small"to"medium"to"large)" • Walls"of"veins"also"have"three+layers","however"the"muscular"layer"is"much"less"prominent" • Compared+with+arteries+veins+typically+are+more+numerous+and+have+thinner+walls,+larger+ diameters,+and+greater+structural+variation+ • Small"to"medium"sized"veins"have"valves"which"assist"venous"blood"flow"by"preventing" backflow" +

6" " Large+veins+–"have"a"well"develop"tunica"intima,"but"the"tunica"media"is"thinner,"with"few"smooth" muscle"cells"and"connective"tissue."" • Tunica+intima+–"consist"of"endothelium,"its"basal"lamina"and"a"small"amount"of"subAendothelial" connective"tissue"with"smooth"muscle"cells."" • Tunica+media+–"is"relatively"thin,"it"contains"smooth"muscle"cells,"collagenous"fibers,"and"some" fibroblasts."" • Tunica+adventitia+–"relatively"thick"containing"bundles"of"longitudinally"disposed"smooth"muscle" cells,"some"fibroblasts,"collagenous"fibers"and"some"elastic"fibers."" o In"large"veins"the"tunica"adventitia"is"the"thickest"and"bestAdeveloped"layer." T."Intima"–very"thin"layer"of"endothelium,"basal" lamina"and"CT"

T."Media"

T."Adventitia"

Large"vein" " Medium+veins+–"all"three"layers"of"the"venous"wall"are"most"evident."" (thinner"–"walled"than"artery;"lumen"larger"and"usually"oblong)" • Tunica+intima+–"consist"of"endothelium,"its"basal"lamina"and"a"small"amount"of"subAendothelial" connective"tissue"with"smooth"muscle"cells,"and"a"thin"internal"elastic"membrane."" • Tunica+media+–"is"much"thinner"than"the"medium"arteries,"it"contains"circularly"arranged" smooth"muscle"cells"and"collagenous"fibers."" • Tunica+adventitia+–"relatively"thicker"than"the"tunica"media."It"is"made"up"of"connective"tissue" with"many"longitudinally"disposed"bundles"of"smooth"muscle"cells,"collagenous"fibers"and" network"of"elastic"fibers."

Medium"Vein" " Venules+ • Post"capillary"venules"(which"receive"blood"from"capillaries)"have"only"an"endothelial"lining" (intima)"and"lack"a"smooth"muscle"media."

7" " • •

Collecting"venules"have"a"thin"adventitia"in"addition"to"the"pericytes"surrounding"the"intima."The" adventitia"consists"of"longitudinally"arranged"collagen"fibres"with"a"few"elastin"fibres."" Muscular"venules"have"1A3"layers"of"smooth"muscle"surrounding"the"intima,"and"an"adventitia"as" described"above.""

+ + Capillaries+–are"the"smallest"diameter"vessels"and"the"site"of"exchange"of"metabolites"between" blood"and"tissues."Capillaries"are"just"wide"enough"to"allow"the"passage"of"red"blood"cells,"only" one"cell"at"a"time." • Thin"walled;"lumen"very"tiny,"one"cell"diameter" • Walls"consist"of"endothelium"+"basal"lamina"+"thin"sheath"of"delicate"collagen"and"reticular" fibres"in"larger"capillaries" Capillary"

" Types+of+capillaries+–+continuous,+fenestrated+and+sinusoidal+ • Continuous+capillaries"–"most"common,"in"these"the"endothelial"cells"are"joined"and"form"an" uninterrupted,"solid"endothelial"lining"(found"almost"everywhere"in"muscle,"connective"tissue," nervous"tissue,"skin,"respiratory"organs"and"exocrine"glands)" • Fenestrated+capillaries"–"characterized"by"large"openings"or"fenestrations"in"the"cytoplasm" of"endothelial"cells"designed"for"a"rapid"exchange"of"molecules"between"blood"and"tissues." (found"in"endocrine"tissues"or"glands,"small"intestine,"and"kidney"glomeruli)" • Sinusoidal+(discontinuous)+capillaries"A"blood"vessels"that"exhibit"irregular,"tortuous"paths." Their"much"wider"diameters"slow"down"the"flow"of"blood."Endothelial"cells"junctions"are" rare"in"sinusoidal"capillaries"and"wide"gaps"exist"between"individual"endothelial"cells."" Because"a"basement"membrane"underlying"the"endothelium"is"either"incomplete"or"absent," a"direct"exchange"of"molecules"occurs"between"blood"contents"and"cells"(found"in"liver," spleen"and"bone"marrow)" + Lymphatic+system:"network"of"drainage"vessels"for"returning"excess"extra"vascular"fluid,"the"lymph,"to" the"blood"circulatory"system"and"for"transporting"lymph"to"the"lymph"nodes"for"immunological" screening." • System"starts"as"blindAending"tubules"or"lymphatic"capillaries"in"the"connective"tissue"of"different" organs" • To"allow"greater"permeability,"the"endothelium"in"lymph"capillaries"and"vessels"is"extremely"thin" • The"structure"of"larger"lymph"vessels"is"similar"to"that"of"veins"except"that"their"walls"are"much" thinner.""

8" " • •

Lymph"vessels"–"look"like"small"to"medium"sized"veins"without"RBCs;"Tunics"somewhat"less"distinct" Lymph"capillaries"–"resemble"continuous"capillaries"BUT"basal"lamina"is"incomplete"or"lacking"

Comparison"between"lymphatic"vessel" (L)"and"venule"(V)"

" " Summary"–Differences+between+Arteries+and+Veins+ "

" " ARTERY-VEIN COMPARISON Artery Vein Lumen = 1/2 wall thickness, oval Lumen larger relative to wall, oblong Maintains rigidity Collapses without blood Inner Elastic Lamina is heavy Internal elastic lamina is slight or not distinct More muscle Tunica media is relatively thin Tunica media is the thickest tunic Tunica adventitia is the thickest tunic Tunica adventitia is thin An artery and vein frequently run together, and this facilitates their comparison. A useful generalization is that the artery has a relatively thick wall and a small lumen, whereas a vein has a relatively thin wall and a broad lumen....