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Rob  Swatski  Associate  Professor  of  Biology  

HACC  –  York  Campus  

Chapter  21    

The  Cardiovascular  System:      Blood  Vessels  &  Hemodynamics  

Textbook images - Copyright © 2014 John Wiley & Sons, Inc. All rights reserved.

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Blood  Vessels  Structure  &  FuncHon  

Arteries  &  Arterioles  

Veins  &  Venules   Capillaries  

Hemodynamics  

Circula4on   Regula4on  

Types  of  Blood  Vessels  

Arteries:  transport  blood  away  from  

heart  

Arterioles:  transport  blood  to  capillaries    

Capillaries:  gas  &  solute  exchange  

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Types  of  Blood  Vessels  

Venules:  drain  blood  

from  capillaries  into  larger  veins  

Veins:  return  blood  to  the  heart  

Vaso  Vasorum:  transport  blood  to  4ssues  of  BV  

wall  

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Anastomosis  

End  artery  

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Layers  of  the  Artery  

Wall  

Tunica  externa  

Tunica  media  

Tunica  interna  

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Layers  of  the  Artery  Wall  

Tunica  externa  

Elas4c  &  collagen  fibers  

Tunica  media  

Circular  smooth  muscle  

External  elasHc  lamina  

Tunica  interna  

Internal  elasHc  

lamina  &  basement  membrane  

Endothelium  (simple  

squamous  epithelium)  

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Transverse  SecHon  Through  an  Artery  

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FuncHonal  ProperHes  of  Arteries  

ElasHcity  (elas4c  lamina)  

ContracHlity  (smooth  muscle)  

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SympatheHc  Nervous  System  

RegulaHon  

VasoconstricHon  (Vasospasm)  

VasodilaHon  (NO,  K+,  H+)  

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ElasHc  Arteries  

=  ConducHng  arteries  

Largest  diameter  &  thicker  elas4c  lamina  (elas4c  

lamellae)  

Less  smooth  muscle  

Pressure  reservoir  

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Muscular  Arteries  

=  DistribuHng  arteries  

Medium  diameter  &  thinner  elas4c  

lamina  

More  smooth  muscle  &  thicker  

walls  

Stronger  vasoconstric4on  

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Arterioles  

Very  small  diameter  &  less  smooth  muscle  

Deliver  blood  to  capillaries  

Regulate  blood  flow  

Adjust  arterial  blood  pressure  

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Metarterioles  

Regulate  blood  flow  into  capillaries  

Precapillary  sphincters  

Thoroughfare  channel  

VasomoHon:  fills  bed  5-­‐10x/min  

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Blood  Flow  Into  Capillary  Bed  

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Blood  Flow  Into  Thoroughfare  Channel  

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Capillaries  Connect  arterioles  

to  venules   Capillary  bed   MicrocirculaHon   Gas,  nutrient,  &  waste  exchange  

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ConHnuous  Capillaries  

Endothelium  with  “leaky”  4ght  junc4ons  

Intercellular  cleQs  

In  skeletal  &  smooth  muscle,  lungs,  connec4ve  

4ssue  

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Fenestrated  Capillaries  

Endothelium  with  many  fenestraHons  

(pores)  

Intercellular  cleds  

In  kidneys,  small  intes4ne,  glands,  choroid  plexuses  

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Glomerulus  

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Sinusoids  

Endothelium  with  incomplete  basement  membrane  

Very  large  fenestra4ons  &  intercellular  cleds  

In  liver,  bone  marrow,  spleen,  pituitary  gland  

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Venules  Drain  capillary  beds  

Thin  walls  &  less  smooth  muscle    

Blood  reservoir  

Postcapillary  venules:  very  porous  endothelium  

Microcircula4on,  emigra4on  of  WBCs  

Lead  to  muscular  venules  

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Veins  

Have  same  3  layers  as  arteries  

Thinner  walls  with  valves  

Lifle  smooth  muscle  &  no  elas4c  

lamina    

Thicker  tunica  externa  

Adapt  to  changes  in  volume  &  pressure  

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Venous  (Vascular)  Sinuses  

Very  thin  walls  

No  smooth  muscle  

Surrounded  by  dense  CT  for  support  

Superior  sagifal  sinus,  coronary  sinus  

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Other  Differences  

Between  Veins  and  Arteries  

Veins  are  more  abundant  

Veins  can  be  found  in  double  sets  called  anastomoHc  veins  

Many  superficial  veins  in  SubQ  layer  

Deep  veins  

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Varicose  Veins  Dilated,  twisted  superficial  veins  caused  by  leaky  

valves  

Congenital  or  due  to  physical  

stress  

Blood  pools-­‐up  in  veins  

Higher  pressure  forces  fluids  into  

ECF  

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Varicose  Veins  

In  legs,  esophagus,  anal  

canal  (hemorrhoids)  

Why  is  it  uncommon  for  deeper  veins  to  

become  varicose?  

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Anastomoses  

2  or  more  BVs  supplying  same  

region  

Angiogenesis  

Collateral  circulaHon  

(alternate  routes)  

Ex:  circle  of  Willis,  coronary  circulaHon  

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Blood  DistribuHon  

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Capillary  Exchange  

Transfer  of  chemicals  b/w  

blood  &  inters44al  fluid  

Through  diffusion,  transcytosis,  and  

bulk  flow  

Across  endothelium,  

through  cleds  &  fenestra4ons  

O2,  CO2,  glu,  AA,  hormones,  solutes  

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Blood-­‐Brain  Barrier  (BBB)  No  diffusion  of  water-­‐soluble  

solutes  

Con4nuous  capillaries  with  4ght  junc4ons  

No  cleds  or  fenestra4ons  

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Transcytosis  

Moves  substances  through  

endothelium  

Uses  vesicular  transport  

(endocytosis  &  exocytosis)  

Transports  larger,  lipid-­‐insoluble  molecules  (proteins)  

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Bulk  Flow  

Moves  large  amounts  of  substances  in  same  direc4on  

Faster  transport  rates  (high  to  low  pressure)  

Regulates  blood  &  inters44al  fluid  volumes  

FiltraHon  &  ReabsorpHon  

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FiltraHon  

Moves  substances  out  of  blood  and  into  inters88al  

fluid  

Blood  HydrostaHc  Pressure  (BHP)  

IntersHHal  Fluid  OsmoHc  

Pressure  (IFOP)  

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ReabsorpHon  

Moves  substances  from  inters44al  fluid  into  capillaries    

Blood  Colloid  OsmoHc  Pressure  (BCOP)  

IntersHHal  Fluid  

HydrostaHc  Pressure  (IFHP)  

Net filtration pressure (NFP)

Blood plasma

Blood flow from arteriole into capillary

Lymphatic fluid (lymph) returns to Lymphatic

capillary Key: BHP = Blood hydrostatic pressure IFHP = Interstitial fluid hydrostatic pressure BCOP = Blood colloid osmotic pressure IFOP = Interstitial fluid osmotic pressure NFP = Net filtration pressure

Blood flow from capillary into venule

BHP = 16 mmHg

BCOP = 26 mmHg

IFHP = 0 mmHg

Interstitial fluid IFOP =

1 mmHg

BCOP = 26 mmHg

BHP = 35 mmHg

Tissue cell

N F P

Net filtration at arterial end of capillaries (20 liters per day)

(BHP + IFOP)

Pressures promoting filtration

Net reabsorption at venous end of capillaries (17 liters per day)

(BCOP + IFHP)

Pressures promoting reabsorption

Arterial end Venous end

NFP = (35 + 1) – (26 + 0) = 10 mmHg

NFP = (16 + 1) – (26 + 0) = –9 mmHg

Net filtration Net reabsorption

N F P

= –

Result

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Net  FiltraHon  Pressure  (NFP)  Net  outward  pressure  =    10  mmHg  at  arterial  end  

Net  inward  pressure  =    9  mm  Hg  at  venous  end  

85%  of  filtered  fluid  returns  to  capillaries  via  lympha4cs  (3L/

day)  

Volume  Reabsorbed  

Volume  Filtered  

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Starling’s  Law  of  the  Capillaries  

Edema  

Due  to  excess  filtraHon  

High  blood  pressure  

(hypertension)  

High  capillary  permeability  (leaks  plasma  proteins)  

Due  to  poor  reabsorpHon  

Low  plasma  proteins  (lowers  

BCOP)  

Slow  protein  synthesis  or  loss  due  to  liver  or  renal  problems  

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Blood  Pressure  (BP)  

Cardiac  Output  (CO)   Volume  

Viscosity   Velocity   Resistance  

ElasHcity   Venous  Return  

Factors  AffecHng  Hemodynamics  

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Resistance  

Opposi4on  to  blood  flow  due  to  

fric8on  

Highest  in  arterioles,  

capillaries,  &  venules  

Vascular  resistance:  varies  with  diameter,  viscosity,  length  

Systemic  Resistance:  total  

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Blood  Pressure  (BP)  

Due  to  ventricular  systole  (120  mmHg  in  

aorta)  

BP  increases  as  CO  increases  

BP  decreases  away  from  led  ventricle  

35  mmHg  @  capillaries  

0  mmHg  @  right  atrium  

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Venous  Return  Volume  of  blood  flow  returning  to  heart  from  veins  

Skeletal  muscle  pump:  muscle  contrac4on  &  

valves  

Respiratory  pump:  moves  blood  into  

right  atrium  

Lower  thoracic  pressure  à  Higher  

abdominal  pressure  during  

inhala4on  

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Velocity  of  Blood  Flow  

Inversely  related  to  BV  cross-­‐sec4onal  

area  

Flow  is  slowest  where  cross-­‐

sec4onal  area  is  highest  

Velocity  decreases  from:  aorta  à  arteries  à  capillaries  

Velocity  increases  from:  veins  à  right  atrium  

3-­‐5  cm2  

40  cm/sec  

4500-­‐6000  cm2  

0.1  cm/sec  

14  cm2  

15  cm/sec  

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Factors  that  Increase  Blood  Pressure  

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Control  of  BP  and  Blood  

Flow  Cardiovascular  

Center:  in  medulla  oblongata  of  brainstem  

Sympathe4c  &  parasympathe4c  

control  

Regulates  HR,  contrac4lity,  &  BV  

diameter  

Vasomotor  nerves:  adjust  BV  diameter  

vasodilator  center  

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vasomotor  tone  

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Neural  RegulaHon  

of  BP  Baroreceptors:  in  major  arteries  

CaroHd  sinus  reflex:  maintains  

brain  BP  

AorHc  reflex:  maintains  general  

systemic  BP  

If  BP  decreases:  HR,  contrac4lity,  &  vasoconstric4on  

increase      

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Syncope  (FainHng)  

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Syncope  A  sudden  loss  of  consciousness  due  to  cerebral  ischemia  (fainHng)  

Vasodepressor  syncope  

Sudden  emo4onal  distress  

SituaHonal  syncope  

Pressure  stress  of  coughing,  defeca4on,  urina4on    

Drug-­‐induced  syncope  

Diure4cs,  an4-­‐hypertensives,  vasodilators,  tranquilizers  

OrthostaHc  hypotension  

BP  decrease  upon  standing  

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Chemoreceptor  Reflexes  

CaroHd  bodies  &  AorHc  bodies  

Detect  changes  in  blood  O2,  CO2,  H+    

Hypoxia,  hypercapnia,  acidosis  

S4mulate  CV  center:  increases  

vasoconstric4on  &  respiratory  rate  

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Hormonal  RegulaHon  of  

BP  

Renin-­‐Angiotensin-­‐Aldosterone  system  (RAA)    

Ac4vated  by  drop  in  BP  or  reduced  blood  flow  to  kidney  

Kidneys  à  Renin  

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Renin  

Angiotensin    (vasoconstricHon)  

Aldosterone    (H2O  &  salt  

reabsorpHon)  

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Hormonal  RegulaHon  of  BP,  cont.  

Epinephrine  &  Norepinephrine  

Increases  HR  &  contrac4lity  à  

raises  BP  

ADH  (AnHdiureHc  Hormone)  [aka  vasopressin]  

Triggers  vasoconstric4on  à  raises  BP  

Promotes  reabsorp4on  of  H2O  into  blood  à  

increases  blood  volume  &  decreases  urine  output  

ANP  (Atrial  NatriureHc  PepHde)  

Triggers  vasodila4on  à  lowers  BP  

Increases  loss  of  Na+  and  H2O  in  urine  à  lowers  blood  volume  

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Pulse  Alterna4ng  

expansion  &  recoil  of  elas4c  arteries  ader  every  le<  ventricle  systole  

ResHng  pulse  rate:  avg  70-­‐80  bpm  

Tachycardia:  >100  bpm  

Bradycardia:  <50  bpm  

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Measurement  of  BP  

Sphygmomanometer  (BP  cuff)  

Korotkoff  sounds:  provide  info  about  systemic  resistance    

Systolic  BP:  ventricular  

contrac4on  (120  mmHg)  

Diastolic  BP:  ventricular  relaxa4on  

(80  mmHg)  

Pulse  pressure:  difference  b/w  

systolic  &  diastolic  BP  (=  40  mmHg)  

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Shock  Poor  CO:  cannot  deliver  enough  O2  

&  nutrients  

Cell  membrane  dysfunc4on  &  abnormal  metabolism  

Cell  death  due  to:  poor  perfusion,  

switch  to  anaerobic  

respira4on,  &  lac4c  acid  build-­‐up  

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Weak,  but  rapid,  res4ng  pulse  (tachycardia)  

Clammy,  cool,  pale  skin  (vasoconstric8on)  

Altered  mental  state  (cerebral  ischemia)  

Hypotension   Low  cardiac  output  (CO)   Swea4ng  (sympathe8c  s8mula8on)  

Thirst  (loss  of  ECF)   Acidosis  (lac8c  acid  build-­‐up)  

Decreased  urine  forma4on  

(vasoconstric8on,  increased  aldosterone  &  

ADH)  

Signs  &  Symptoms  of  Shock  

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Types  of  Shock  

Hypovolemic  

Decreased  blood  or  body  fluid  volume  

Hemorrhage,  poor  fluid  intake,  excessive  

swea4ng,  vomi4ng,  diarrhea  

Cardiogenic  

Poor  heart  func4on  

MI,  ischemia,  valve  disorders,  high  preload/aderload,  arrhythmias,  

poor  contrac4lity  

ObstrucHve  

Blockage  of  blood  flow  

Pulmonary  embolism  

Vascular  

Inappropriate  vasodila4on  

Anaphylac4c,  sep4c,  or  neurogenic  shock    

Hypovolemic shock

CONTROLLED CONDITION Blood volume and blood

pressure

RECEPTORS

CONTROL CENTER CONTROL CENTER CONTROL CENTER

Liver and lungs Hypothalamus and posterior pituitary

Cardiovascular center in medulla oblongata

EFFECTORS

Adrenal cortex

Kidneys Blood vessels

Heart

Increased blood volume

Increased systemic vascular resistance Increased blood

pressure

Return to homeostasis when responses bring blood volume and blood pressure back to normal

Increased sympathetic stimulation and hormones from adrenal medulla

ADH in blood Angiotensin II in blood

Increased secretion of renin

Decreased rate of nerve impulses

Inputs

Outputs

Disrupts homeostasis by moderately decreasing

Baroreceptors in kidneys (juxtaglomerular cells)

Baroreceptors in arch of aorta and carotid sinus

ADH

EFFECTOR

RESPONSE RESPONSE RESPONSE

Kidneys conserve salt and water

Blood vessels constrict

Heart rate and contractility increase

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Decreased  elas4city  of  aorta  

Smaller  size  of  cardiac  muscle  fibers  

Decreased  CO,  but  maximum  HR   Increased  systolic  BP  

Increased  total  cholesterol  &  LDL;  decreased  HDL  

Increased  risk  of  conges4ve  heart  

failure,  coronary  artery  disease,  

atherosclerosis  

Aging  &  the  Cardiovascular  System  

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Hypertension  

Chronically  high  BP  (systolic  >  140  mmHg;  diastolic  >  90  mmHg)  

Primary  hypertension:  most  common  (no  

iden4fiable  underlying  cause)  

Secondary  hypertension  (has  iden4fiable  cause)  

Damages  BVs,  heart,  brain,  &  kidneys  before  onset  of  no4ceable  

symptoms  

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Lose  weight   Reduce  alcohol   Increase  exercise  

Reduce  salt  Eat  healthy  diet  to  maintain  K+,  Ca+2,  

and  Mg+2  Don’t  smoke  

Manage  stress  

Meds:  diure4cs,  beta-­‐blockers,  

vasodilators,  Ca+2  channel  blockers    

Treatment  of  Hypertension  

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