P215 Cardiovascular System Blood Vessels Chapter 14 Introduction

Transcription

1 P215 Cardiovascular Systm Blood Vssls Chaptr 14 Introduction vins tubs for blood flow lumn - for blood flow wall - Blood Flow Through Blood Vssls largst vins hart largst artris blood always containd by vssls (and hart chambrs) artris a circulatory systm vnuls capillaris blood vssl cross-sction conntiv tissu and muscl lining - layr of clls wall and lumn blood vssl functions hlp dtrmin: 1) blood 2a) blood flows in body 2b) blood flows to parts of body artriols most important goal: continuous blood flow through capillaris: sits of btwn blood and surrounding fluid som gnral charactristics largst artris two artris artriols capillaris vnuls vins many billions largst vins two 4.0 mm mm 5.0 mm total ara of 3000 x spd of 30 cm/sc 24 cm/sc barly abov 0 cm/sc from figur 14.16

2 blood vssl anatomy s figur 14.6 wall artris connctiv tissu smooth muscl lumn ndothlium (lining layr) a basic charactristic thick, strong walls artriols capillaris vnuls vins lots of smooth muscl for thir siz thin wall - singl ndothlial cll layr thinnr walls lss smooth muscl than comparabl artriols and artris blood vssls: blood prssur and blood flow two big factors affct blood flow factor #1: (actually, diffrnc in ) blood prssur (BP) - BP a forc that pushs against of blood vssls and pushd blood of blood vssls blood prssur as blood flows through systmic and pulmonary circuits largst artris artris artriols capillaris vnuls vins largst vins blood prssur

3 from artris to vins, thr s a diffrnc in blood prssur (BP) that s important... diffrnc in BP ( ) btwn two points blood flow blood ALWAYS flows from to prssur look at systmic and pulmonary circuits (blood prssur oftn masurd in millimtrs of mrcury - mm Hg) mm Hg right atrium mm Hg lft vntricl systmic circuit in systmic circuit BP = mm Hg prssur circuit mm Hg pulmonary circuit right vntricl lft atrium mm Hg in pulmonary circuit BP = mm Hg prssur circuit pulmonary circulation systmic circulation pulmonary circulation systmic circulation artris capillaris vins right sid of hart artris capillaris vins lft sid of hart why dos th systmic circuit rquir mor muscl in th wall of th lft vntricl?

4 in addition to BP, factor #2 also affcts blood flow: du to as blood flows along blood vssl walls blood flow = BP / as BP riss, blood flow as R riss, blood flow sourcs of Rsistanc (R) to blood flow in our cadiovascular systm 1) blood affctd by numbr of RBCs in plasma polycythmia hmolytic anmia RBC # viscosity RBC # viscosity blood doping aplastic anmia 2) blood vssls adding nw blood vssls adding wight R of systmic circuit R of pulmonary circuit 3) blood vssl lumn blood vssl cross-sction smooth muscl rsistanc smooth muscl rsistanc rducing diamtr of blood vssls by half... raiss rsistanc total priphral rsistanc ( ) total priphral rsistanc = rsistanc to blood flow through of body s blood vssls along which blood is currntly flowing

5 artris blood vssls xposd to highst blood prssur thick walls but rlativly complianc of artry walls: prim jobs: 1) withstand 2) hlp produc blood flow xampl vn whn vntricls ar opn smilunar valv during vntricular lft vntricl blood aorta flow aorta blood flow artry closd smilunar valv from figur 14.7 during vntricular lft vntricl aorta blood flow artry artrial prssur: masurmnt and calculations systolic prssur artris artriols capillaris vnuls vins diastolic prssur puls prssur man artrial prssur avrag BP (mm Hg) diastolic BP systolic BP systmic circulation systolic prssur 0 artris artriols capillaris vnuls vins diastolic prssur from figur 14.8 from figur 14.9 MAP is wightd toward prssur bcaus hart spnds mor tim in

6 artriols small artris >>> artriols >>> capillaris walls - lastic tissu, bands of smooth muscl thr s always som smooth muscl contraction mor contraction: rsistanc lss contraction: rsistanc of all blood vssls, artriols offr th to blood flow changing artriol diamtr affcts rsistanc - ky artriol function prim job: 1) distribution of artrial sid * artriols a rt ri s * * * hart tissu tissu tissu capillaris v i n s vnous sid hart hart 1.5 L/min 1.5 L/min 1.0 L/min 0.5 L/min 0.5 L/min 0.5 L/min capillaris capillaris from figur prim job: 2) blood prssur in artrial BP a rt ri s hart v i n s artrial BP a rt ri s hart v i n s many artriols constrictd TPR MAP MAP = CO x many artriols dilatd TPR MAP why b concrnd about artrial BP?

7 artriols function fundmntally dpnds on construction and dilation why do artriols constrict and dilat? answr: 1) capabilitis of thir 2) rspons to influncs rspons of artriols thmslvs first xampl - rspons to local concntration of suppos... oxygn lvl in tissu carbon dioxid lvl in tissu in rspons... artriol smooth muscl rsistanc blood flow to th local tissu happns whn local mtabolic activity happns whn local blood flow has bn calld = blood flow dirct rspons of artriol what happns if oxygn lvls climb abov normal? scond xampl - rspons to local suppos artriol BP thn, artriol blood flow as a rsult, strtch of artriol smooth muscl smooth muscl rsponds by artriol as a rsult, rsistanc and blood flow calld dirct rspons of artriol with strtch-snsitiv fibrs found in and som othr organs / tissus what happns if artrial BP falls blow normal?

8 artriols rspons of influncs outsid artriols primarily from sympathtic autonomic nrvous systm rcptors for norpinphrin and pinphrin on smooth muscl clls in artriols in many tissus, artriols in cardiac muscl and skltal muscl artriols sam substancs - pi and norpi - lad to diffrnt rsponss how? othr chmical substancs also influnc artriols smooth muscl rlaxation - dilation smooth muscl contraction - constriction combination of insid and outsid influncs two xampls 1) xrcis blood flow skltal muscl skin hart brain GI tract kidnys rst 1.0 L/min 0.25 L/min 0.2 L/min 0.7 L/min 1.25 L/min 1.0 L/min how dos th chang during xrcis occur? xrcis 20.0 L/min 0.65 L/min 1.15 L/min 0.8 L/min 1.05 L/min 0.85 L/min 2) man artrial prssur (MAP) tissu tissu tissu tissu tissu tissu most artriols constrictd most artriols dilatd TPR TPR MAP MAP rmmbr, MAP =

9 short-trm rgulation of MAP artrial barorcptors baro = monitor systmic artrial barorcptors intrnal carotid artris to cardiovascular control cntr in brainstm aorta snsory ndings in wall of artry carotid artry barorcptor snsory affrnt axons lvatd artrial BP strtch of artrial wall dpolarization of snsory ndings frquncy of APs in barorcptor snsory affrnts normal artrial BP normal normal normal dprssd artrial BP if artrial BP in systmic artris dparts from normal... cardiovascular control cntr in brainstm coordinats a rflxiv rspons that tris to mov BP barorcptor rflx an xampl: suppos MAP bgins to du to strtch of artrial barorcptors dpolarization of snsory ndings AP frquncy in barorcptor affrnts to cardiovascular control cntr cardiovascular control cntr activats autonomic nrvous systm SA nod HR sympathtic activity parasympathtic activity hart vins artriols myocardium contractility SV constriction vnous rturn to hart EDV constriction CO TPR MAP

10 artriols anaphylactic shock (cardiovascular) shock = suddn, sharp drop part of a svr allrgic raction molculs rlasd by immun systm produc widsprad of vssl smooth muscl and of bood vssls artrial BP dangrous dclin in a quick, ffctiv tratmnt: capillaris smallst blood vssls 1 mm long 5-10 micron diamtr most numrous blood vssls billions and billions and billions thinnst-walld blood vssls on cll thick slow flow of blood 0.1 mm / sc ndothlial cll prim job: sit of hug surfac ara blood plasma blood plasma intrstitial fluid air sacs in lungs thr kinds of capillary walls 1 - slightly 2 - vry laky 3 - tight intrstitial fluid ndothlial clls blood 1 - slightly laky 2 - vry laky intrstitial fluid 3 - tight ndothlial clls blood from figur 14.17

11 capillaris xchang across capillary walls watr movmnt out of blood filtration primary factor: blood plasma intrstitial fluid watr movmnt into blood absorption primary factor: blood plasma intrstitial fluid albumin protins mad by livr clls prsnt in blood plasma artriol artriol sid capillary vnul sid vnul artriol nt prssur from figur capillary vnul not an ntirly qual xchang across capillary walls oftn slightly xcds with this imbalanc: dvlops

12 capillaris - functions swlling worsns whn flitration absorption blood prssur albumin protins in blood plasma solving this imbalanc lymphatic vins lymphatic capillaris xcss fluid (s figur 14.25) largst vins hart largst artris vins artris vnuls capillaris artriols vnuls carry blood rturning from capillaris thin walls, littl smooth muscl smallst vnuls rsmbl capillaris vins prim job: rturn pathway back to complianc: than artris blood volum... in systmic artris/artriols in systmic capillaris in hart in pulmonary circuit from figur in systmic vnuls/vins

13 vins - functions main rol - low rsistanc rturn to hart vnous rturn skltal muscl pump to hart to hart from figur skltal muscl rlaxd skltal muscl contractd vins - promot vnous rturn rspiratory and skltal muscl pumps sympathtic autonomic activity vnomotor ton blood volum