Mammalian Circulation

8/17/2019 Mammalian Circulation

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Mammalian Circulation

CAPE II Bio

R.Wint


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Objectives

1. Describe the structure of a typicalaalian heart

!. E"plain #ouble circulation

$. Relate the structures of arteries%veins an# capillaries to theirfunctions.

&. I#entify the #estination of the ajorbloo# vessels to an# fro the heart


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Overvie'

• (he heart pups bloo# aroun# thebo#y

• (he aalian heart has &

chabers an# sho's #oublecirculation.

• Double Circulation: eans that the

bloo# passes throu)h the heart t'icefor the bo#y to be supplie# once.

• (he ! circulations are systemic

circulation an# pulmonary circulation


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Bloo# *essels

•

Blood vessels are hollo' tubularor)ans that con#uct bloo# aroun#the bo#y.

•

(he bloo# vessels consist ofarteries% arterioles% capillaries%venules% an# veins.


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Bloo# *essels


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Typical Blood Vessel


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Arteries +unction•

Arteries transports bloo# a'ay frothe heart at high pressure.

• Arteries are a#apte# to be stron)%

,e"ible an# elastic.


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-tructure of Arteries

• Arterial 'alls are able to e"pan# an#contract.

• Arteries have three layers of thic

'alls an# hollo' re)ion no'n aslumen.

• TunicaExterna: connectivetissue / elastic

0bres• Tunica Media:

sooth uscle/ elastic 0bres

colla)en2• Tunica Intima:


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tructure o! Veins

• *eins return bloo# to the heart at lo'pressure.

• (hus *eins have uch thinner 'alls

than #o arteries% lar)ely because thepressure in veins is so uch lo'er.

• *eins can 'i#en #ilate2 as the

aount of ,ui# in the increases


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tructure o! Veins


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Capillaries

• Capillaries are icroscopic an# onecell thic an# are the sites for thee"chan)e of nutrients% 'aste% an#

o"y)en 'ith tissues at the tissue3cellular level


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Capillaries

• Capillaries are icroscopic vessels 'ith verythin% porous 'alls.

•

4et'ors of these vessels% calle# capillarybeds% in0ltrate every tissue% passin) 'ithin afe' cell #iaeters of every cell in the bo#y.

•

Across the thin 'alls of capillaries% cheicals%inclu#in) #issolve# )ases% are e"chan)e# bydi"usion bet'een the bloo# an# theinterstitial #uid aroun# the tissue cells.


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$%$T&M' $%D ()'I&*&+'&, T)E )E$-T


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Objectives1. Describe the structure of heart5internal an# 6.-. vie'%

inclu#in) valves an# ajor vessels

!. Describe the coposition of three layers of the heart

$. -tate the role of coronary artery

&. Describe the role of the pericar#iu

7. Describe the Paceaer8. Outline the car#iac cycle an# its initiation

9. Discuss the internal factors that control heart action

:. Distin)uish bet'een heart beat, pulse and blood

pressure;. Distin)uish bet'een systolic an# #iastolic pressure

1


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>eart E"ternal +rontal *ie'


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E"ternal +rontal *ie'


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Coronary Circulation

• (he heart receives its o'n supply of bloo#fro coronary arteries.

•

Coronary arteries: vessels that supplybloo# to the yocar#iu heart uscle2

• Cardiac veins: reove #eo"y)enate#bloo# fro the heart uscle.

• (hese relatively narro' vessels arecoonly a=ecte# by atherosclerosis an#can becoe bloce#% causin) an)ina ora myocardial in!arction heart attac.


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Interior Anterior *ie' 6.-.2


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Interior3Anterior *ie'


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Route of Bloo#


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(he >eart• 6ocate# bet'een your lun)s in the i##le of your

chest% behin# an# sli)htly to the left of yourbreastbone sternu2 .

• A #ouble5layere# ebrane calle# the

pericardium surroun#s the heart lie a sac.• (ericardium is very iportant to car#iac function@

– -tabilises the heart in its position an# prevents

overin,ation – pericar#ial ,ui# lubricate the heart an# re#uces the

friction on heart #urin) beatin)

– Protects it fro infections coin) fro nearby or)anssuch as lun)s2


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6ayers of (he heart• >eart 'all has $ layers@

epicardium myocardium

and endocardium

/. Epicardium 0visceralpericardium1: thin layerof connective tissue an# fat%serves as a##itional layer ofprotection.

2. Myocardium: thickestlayer copose# of car#iacuscle that contracts forbeatin) an# con#uctselectricity

3. Endocardium: copose#of endothelial cells 'hich


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Chabers of (he >eart•

(he atrial 4alls are thin they #ont nee#to 4ithstand uch pressure.

• (he ventricles 4alls on the other han#are uch thic5er.

• When the ventricles contract% the bloodpressure insi#e becoes very high% an#they nee# to be able to 4ithstand this.

•

(he 4alls of the le!tventricle are thic5er than those ofthe right ventricle.


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$tria6 Ventricles Cont7d

• -ysteic circulation is un#er hi)her pressure thanpulonary

• Blood in the systemic circuit nee#s to be ata high pressure in or#er to ae its 'ay aroun#

the 4hole body an# bac5 a)ain.• In contrast% the lungs are very close to the heart%

an# contain very delicate capillaries 'hich'oul# brea5 if subjecte# to too )reat a pressure.

• >ence the systemic circuit reuires a greaterblood pressure than the pulmonary circuit% an#thus the 4alls of the le!t ventricle ustbe thic5er than those of the right ventricle.


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Valves

• (he valves prevent the bac'ar#,o' of bloo#.

• (apillary muscle@ A sall uscleon the ,oor of the ventricles thatanchors the heart valves.

• Papillary uscle prevents valvesfro prolapsin)


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Cardiac Cycle• (he cardiac cycle is the seuenceof events that occurs 'henthe heart beats. (here are three

ain phases of the car#iac cycle@Diastole% $trialystole an# Ventricular ystole


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Cardiac Cycle

• (he heart contracts an# rela"es in a

rhythic cycle.

•

When it contracts% it pumps blood 'henit relaxes% its chambers fll with blood.

• One coplete seuence of pupin)

an# 0llin) is referre# to as the cardiaccycle.


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Car#iac Cycle

• In the #iastole phase% theheart ventricles are rela"e# an# the heart0lls 'ith bloo#

• In the systole phase% the ventricles contractan# pup bloo# to the arteries.

• One car#iac cycle is coplete# 'hen theheart 0lls 'ith bloo# an# the bloo# ispupe# out of the heart.

C di C l


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Cardiac Cycle


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Car#iac Cycle


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Cardiac Cycle TermsCardiac output: the volue of bloo#

the ventricles pups per inute. Eualsheart rate x stroke volume

)eart rate: easures the rate of

contraction or nuber of beats perinute. 4orally 8


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Coordination o! CardiacCycle

•What controls the tie# rhythic beatin) ofthe heart Where #oes it ori)inate

• Car#iac cells contract 'hen stiulate# by anelectrical impulse 0action potential1

• -oe car#ioyocytes car#iac uscle cells2are autorhytmic eanin) that they arenot controlle# by the nervous syste

• (he heart has an intrinsic contractionsystem that re)ulates heartbeat.


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inoatrial 0$1 %ode:(acema5er

• (he initiation of the car#iaccycle is controlle# by acluster of autorhytic cellscalle# sinoatrial node orpaceaer.

• inoatrial node: arespecialise# autorhyiccar#ioyocytes locate# at

the upper wall o the rightatrium

• $ node: sets the rate an#tiin) at 'hich all car#iacuscle cells contract.


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Initiation o! Contraction

/.$ node spontaneously )enerates an electricalipulse no'n as an action potential.

!. (hese ipulses sprea# rapi#ly throu)hout the atria%causin) the to contract in unison.

$. (he ipulse fro the -A no#e are con#ucte# frothe atria to the atrioventricular 0$V1 node%locate# bet'een the ri)ht an# left atria.

&. At the A* no#e% the ipulse #elays for


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Intrinsic Conductionystem

i i C d i


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Intrinsic Conductionystem

EC3EF


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EC3EF

•

Ipulses fro the-A no#e arecon#ucte# to sinvia bo#y ,ui#s.

• In theelectrocardiogram these ipulsesare recor#e# byelectro#es place#on the sin

l i i


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rdiac Cycle ave• Depolarisation G contr

• -epolarisation G rela


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,actors $"ecting )eart -ate

• Althou)h heart beat is auto)enerate#% its uality is still

a=ecte# other bo#y processes./. $ node activity:

2. ignals !rom the brain

1. -i)nals fro the (arasympathetic 0Vagus1 %erve: slo'sheart rate

!. -i)nals fro ympathetic nerves increases heart rate

$. En#ocrine secretion@ a#renaline secretion increases heartrate ,i)ht or 0)ht o#e2% thyro"in

&. -ensory input H stress emotion etc5 fro hi)her braincentres e#ulla cerebru% etc2

3. &2 concentration: a #rop in O! conc. e.). #urin)

e"ercise2 stiulates the release of 4O that stiulatesvaso#ilation of aterioles increasin) heart rate

&. Chan)es in core bo#y teperature


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B*&&D (-E;-E


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Blood (ressure

•Bloo# pressure is the force per area thatbloo# e"erts on the 'alls of bloo# vessels#urin) the car#iac cycle

• It is e"presse# as a systolic number over a

diastolic number• Bloo# pressure is easure# in illietres of

ercury% mm)g

•

A youn)% 0t person shoul# have a bloo#pressure of about 1!< over 9


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Blood (ressure

• +lui# 'ill ove fro areas of hi)h tolo' hy#rostatic pressures. In the arteries% thehy#rostatic pressure near the heart is very hi)h.

• ystolic pressure is the pea pressure in the

arteries #urin) the car#iac cycle

• (he diastolic pressure is the lo'est pressure atthe restin) phase of the car#iac cycle.

• (ulse pressure is the #i=erence bet'een thesystolic bloo# pressure an# the #iastolic bloo#pressure.

• (ulse: the temporary increase in pressure

l d


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Blood (ressure

•

Bloo# pressure #rops as bloo# ovesfarther a'ay fro the heart.

• (his is #ue to increase# in #istanceas 'ell #i=erence in contraction inarteries vs veins.


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Arterial Bloo# Pressure

• (he 'alls of arteries are thic an#stron)% accoo#atin) bloo#pupe# at hi)h pressure by the

heart.• Arterial 'alls also have an elastic

recoil that helps aintain bloo#

pressure an# ,o' to capillaries


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Venous Blood (ressure•

Althou)h pressurein veins is lo'%several echanissai# in returnin)bloo# to heart@

1. Rhythiccontractions of

sooth uscles inthe 'alls of venulesan# veins

!. the contraction of

seletal uscles


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Internal ,actors That $"ectBlood (ressure

Blood vessel diameterWi#er luen G lo'er pressure% since the area

per force increases.

$utonomic %ervous ystem: nervesi)nals innervatin) arterial sooth usclecan cause vasodilation orvasoconstriction

)ormones and other molecular signals%itric &xide< ainly for vaso#ilation

Endothelin H ainly for vasocontriction


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Dan)ers of Abnoral Bloo# Pressure

• )ypertension – i#ney #aa)e

– burst bloo# vessels

– #aa)e to the brain% inclu#in) stroes.

• 6o' bloo# pressure >ypotension2

can cause #iiness% faintin) an#poor bloo# circulation.


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Capillary ,unction

• Capillaries are microscopic andpenetrates every tissue.

• Capillaries allo' for )as e"chan)e%

an# nutrient an# 'aste e"chan)ebet'een cells. – (hin en#othelial 'alls for rapi# #i=uses

of )ases an# sall olecules – Wall contain icroscopic pores as route

for transport of sall solutes


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Capillary Exchange


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Mammalian Circulation

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