Repaso Examen 1

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Advanced  Human  Physiology  and  Anatomy   Marimar  de  la  Cruz  Review   Prof.  John  Uscian   Chapter  XIII:  The  Circulatory  System     Test  Date:  October  12,  2010  

 

• The  circulatory  system  consist  of  a  major  pump;  the  heart,  and  various  smaller,  pump-­‐like   mechanisms  that  together  move  two  forms  of  liquid  tissues  (blood  and  lymph)  through  an   extensive  network  of  tubular  structures  of  the  body.  

o Functions:  

 delivery  of  nutrients  to  the  cells  

 movement  of  wastes  away  from  the  cell    hormone  delivery  

 immunological  properties    clotting  abilities  

 water  and  ion  balance  

 distribution  of  heat  of  metabolism  

o Two  components:  cardiovascular  system,  lymphatic  system.    

Cardiovascular  System  

• Made  up  of  blood  vessels  and  the  heart.  

• Two  divisions  through  which  the  blood  can  travel:   o Pulmonary  circulation  

 Takes  oxygen-­‐poor  blood  from  the  heart  to  the  lungs  and  then  returns  oxygen-­‐ rich  blood  to  the  heart.  

 Right  half  of  the  heart  ejects  blood  into  it.   o Systemic  circulation  

 Takes  oxygen-­‐rich  blood  to  all  of  the  other  organs  of  the  body  and  returns   oxygen-­‐poor  blood  to  the  heart.  

 Left  half  of  the  heart  ejects  blood  into  it.  

• Arteries  take  blood  away  from  the  heart  and  veins  return  blood  to  the  heart.   • Heart  

o Two  pumps  that  beat  as  one.  

o Pericardium:  fibrous  membrane  that  surrounds  the  heart.  

 Pericardial  cavity  (area  between  the  pericardium  and  the  heart)  is  filled  with   pericardial  fluid.  

 The  pericardial  fluid  functions  as  a  sort  of  lubricant  that  reduces  friction   between  the  beating  of  the  heart  and  the  surrounding  tissues.  

o The  heart  wall  is  compromised  of  three  tissues:  

 Epicardium/  visceral  pericardium:  inner  pericardium  layer  that  comes  in   contact  with  the  heart  

 Myocardium:    heart  muscle  tissue  made  up  of  cardiocytes,  thickest  component   of  heart  wall,  confers  capacity  to  contract.  

 Endocardium:  simple  squamous  epithelium  that  makes  up  the  inside  lining  of   the  heart,  inner  surface  facilitates  movement  of  blood,  heart  valves  form  from   endocardium  folds.  

o Atria:  upper  chambers  of  the  heart  

 right  atrium:  receives  blood  from  superior  and  inferior  vena  cava  and  coronary   sinus.  

 left  atrium:  receives  blood  from  pulmonary  veins    interatrial  septum:  divides  atria  

o Ventricles:  lower  chambers  of  the  heart,  pump  the  blood  into  the  arteries.    right  ventricle:  pumps  into  the  trunk  of  the  pulmonary  artery    left  ventricle:  pumps  blood  into  the  aorta  

 interventricular  septum:  divides  ventricles.  thickest  near  the  apex.   o Atriventricular  valves:  ensure  blood  flows  from  atria  to  ventricles  

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o Papillary  muscles:  conical  muscles  arranged  as  pillar-­‐like  structures  

 chordae  tendineae:  connective  tissue  that  attaches  them  to  the  atrioventricular   valves  

o Pulmonary  valve:  ensures  blood  flow  from  right  ventricle  to  pulmonary  artery   o Aortic  valve:  ensures  blood  flow  from  left  ventricle  to  aorta  

o Aorta:  largest  artery  of  the  body  

o Pulmonary  artery:  directs  blood  from  the  right  ventricle  into  the  lungs.  branches  into   right  and  left  pulmonary  arteries  which  go  into  the  right  and  left  lungs.  

o Heart  is  supplied  with  oxygen-­‐rich  blood  via  the  coronary  arteries,  this  blood  is   returned  to  the  right  atrium  by  the  coronary  sinus  and  pulmonary  veins.   • Mechanical  Events  of  the  Heart  Contraction  Cycle:  

o Left  ventricle  contracts  with  about  seven  times  more  force  than  the  right  ventricle.   o Systole:  ventricular  contraction.  

 isovolumentric  contraction:  volume  of  the  ventricles  is  constat  but  blood   pressure  increases  as  myocardium  begins  to  contract  after  receiving  a  signal.  

• atrial  diastole:  atrial  fill  with  blood  and  increase  volume  as  they  relax.    Ejection  of  blood  from  ventricles:  BP  continues  to  rise  until  threshold  pressure  

and  the  aortic  valve  opens,  at  almost  the  same  instant  the  pulmonary  valve   opens.  

 Late  systole:  BP  decreases  until  valves  close   o Diastole:  ventricular  relaxation.  

 BP  in  the  ventricles  continues  to  fall  and  atria  continue  to  fill  with  blood  until   ventricular  pressure  falls  below  that  of  atria  and  atrioventricular  valves  open.   the  ventricles  fill  almost  to  capacity  during  the  first  third  of  diastole.  

 At  termination  of  the  2/3  of  diastole  an  action  potential  is  generated  by  the   sinoatrial  node.  

 The  action  potential  causes  atria  to  contract  (atrial  systole),  it  travels    through   the  interventricular  septum  into  the  walls  of  the  myocardium  causing  the   ventricles  to  enter  systole  and  contract.  

• Cardiocytes  and  other  aspects  of  heart  histology  

o Heart  skeleton  is  made  up  of  fibrous  connective  tissue  that  extends  from  the  atria  to   the  ventricles.  

 This  tissue  lacks    electrical-­‐conducting  properties.   o Cardiocytes:  heart  muscle  cells  that  make  up  the  myocardium.  

 Binucleated  

 Actin  and  myosin  filaments  arranged  in  sarcomeres    Striated  but  not  as  much  as  skeletal  muscle.  

 Sarcoplasmic  Reticulum  less  developed  that  in  skeletal  muscle.    No  dilated  cisternae.  

 T  tubules  in  close  proximity  to  sarcoplasmic  reticulum  at  fewer  areas,  resulting   in  less  efficient  transfer  of  action  potential  and  slower  onset  of  cardiocyte   contraction.  

 Cannot  function  with  a  significant  oxygen  debt.  

 Enriched  with  mitochondria  that  aerobically  produce  sufficient  ATP  for  the   heart  to  function  under  normal  physiological  demands.  

 Joined  to  one  another  forming  spiraled  sheet-­‐like  structures.  

 Intercalated  disks:  bind  adjacent  cardiocytes,  folds  in  their  membranes  enable   adjacent  cells  to  fit  with  increased  contact  area.  

 Desmosomes:  cardiac  tissue  structures  that  join  cardiocytes.  

 Gap  junctions:  small  protein  channels  that  join  the  cytosol  of  one  cell  to  that  of   an  adjacent  one,  enable  ion  flow  and  action  potential  progression.  

• Heart  Conducing  System:  

o Structured  such  that  the  action  potential  generated  by  the  sinoatrial  node  stimulates   the  atria  to  contract  first  and  the  ventricles  to  follow.  

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o Progression  of  Action  Potential:  Action  potential  is  generated  by  the  SA  node  (located   at  the  junction  of  the  superior  vena  cava  and  the  right  atrium),  it  migrates  along  the   intermodal  pathways  to  the  AV  node  making  the  atria  contract.  The  action  potential   moves  to  the  bundle  of  his  (av  bundle,  located  in  the  superior  portion  of  the  

interventricular  septum)  that  diverges  into  two  segments;  the  right  and  left  bundle   branches,  these  convey  the  action  potential  towards  the  apex  through  the  

interventricular  septum.  The  action  potential  reaches  the  purkinje  fibers  in  the  walls  of   the  ventricles  causing  them  to  contract.  

o The  Purkinje  fibers  convey  action  potentials  much  more  rapidly  than  other  cardiac   tissues  because  of  the  gap  junctions  and  the  well  developed  intercalated  discs  in  the   cardiocytes  that  comprise  these  fibers.  

o The  SA  node  is  made  up  of  cardiocytes  that  can  produce  action  potentials  at  higher   rates  than  other  cardiocytes.  

o It  takes  0.04  seconds  for  the  action  potential  to  move  from  the  SA  node  to  the  AV  node   and  0.1  seconds  in  getting  to  the  bundle  of  his,  a  total  0.15  second  delay  that’s  enough   for  the  atria  to  contract  completely  before  systole,  where  the  ventricles  contract   starting  from  the  heart’s  apex.  

• Cardiocyte/Myocardium  Electrical  Properties  

o Depolarization  of  cardiocytes  is  a  function  the  opening  voltage-­‐gated  fast  Na+  channels.  

The  action  potential  rises  from  -­‐90mV  to  +20mV  membrane  potential  at  which  point   they  close.  

o Repolarization  depends  upon  voltage-­‐gated  slow  Ca+2  channels  and  voltage-­‐gated  K+  

channels.  Voltage-­‐gated  K+  channels  open  and  drops  the  membrane  potential  from  

+20mV  to  0mV,  at  almost  the  same  time  the  Ca+2  channels  open  and  the  influx  of  

calcium  slows  the  rate  of  repolarization  lengthening  it  several  hundred  milliseconds   (by  bringing  the  positive  charge  into  the  cell  and  slowing  the  rate  of  K+  diffusion  

through  like  charge  repulsion).  

o Full  repolarization  occurs  when  the  voltage-­‐gated  Ca+2  channels  close  and  the  K+  

channels  open  once  again  causing  a  sudden  large  outflux  of  potassium  brings  the   membrane  back  to  -­‐90mV.  

• Depolarization  and  Repolarization  of  the  SA  node  

o Depolarization  is  initiated  by  the  opening  of  voltage-­‐gated  slow  Ca+2  channels  open  and  

the  action  potential  rises  from  -­‐60mV  to  -­‐40mV.  This  opens  more  calcium  channels   which  rises  the  membrane  potential  to  +20mV.  At  this  point  calcium  channels  close  and   voltage-­‐gated  K+  channels  open  inducing  a  rapid  repolarization.  

o Normally  70-­‐80  depolarization-­‐repolarization/heartbeats  per  minute.  

o If  SA  node  fails  the  AV  node  can  take  over  but  only  produce  40  to  50  heartbeats  per   minute.  If  this  fails  the  AV  bundle  can  take  over  at  30  beats  per  minute.  

o Ectopic  pacemakers  (ectopic  foci)  can  take  over  the  heartbeat  under  certain  

circumstances  in  which  the  ectopic  foci  action  potentials  are  enhanced,  the  SA  node   rythmicity  is  lowered  or  the  conduction  pathways  from  the  SA  node  to  other  regions  is   reduced.  Example:  dead  cells  because  of  heart  attack.  

• Myocardium  Refractory  Period:  

o Refractory  Period:  time  during  which  a  tissue  cannot  be  activated  after  it  has  been   stimulated.  

o Two  refractory  periods  associated  with  cardiocytes:  

 Absolute  refractory  period:  stimulation  cannot  induce  contraction.  

 Relative  refractory  period:  stimulation  has  a  lessened  capacity  to  stimulate  the   cell  to  contract.  

o The  long  plateau  of  the  myocardium  action  potential  (when  Ca+2  channels  are  open)  

enables  it  to  rest  and  is  an  absolute  refractory  period.  It  plays  a  key  role  in  preventing   titanic  contractions.  

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• Electrocardiogram:  image  obtained  by  an  electrocardiograph  of  the  heart’s  electrical  activity.   o Three  waves  are  normally  produced:  

 P  wave:  depolarization  of  the  atria  

 QRS  wave:  depolarization  and  signals  the  initiation  of  ventricular  contraction    T  wave:  ventricular  repolarization  

o Ion-­‐rich  fluids  of  the  body  propagate  electrical  activity  in  the  body.  

o Absence  of  P  waves  and  a  normal  QT  interval  indicate  atrial  fibrillation  in  which  the   atria  quiver.  It  is  caused  by  ectopic  pacemakers  whose  activities  overwhelm  the  regular   signals.  

• Cardiac  Output,  Blood  Pressure,  and  Heart  Sounds  

o At  rest  the  heart  pumps  about  72  times  per  minute.  

o Average  Stroke  Volume:  volume  of  blood  pumped  through  each  cardiac  cycle;  end-­‐ diastolic  volume  minus  end-­‐systolic  volume.  

o During  rigorous  physical  activity  the  output  may  increase  by  five  times.  

o Cardiac  reserve  =  additional  amount  of  blood  pumped  when  active  -­‐  amount  of  blood   pumped  when  at  rest.  

o Blood  Pressure  is  the  result  of  the  person’s  cardiac  output.   o Mean  Arterial  Pressure:  average  blood  pressure  in  the  aorta  

 MAP  =  (Cardiac  Output)(Peripheral  Resistance:  total  resistance  against  which   the  blood  is  pumped)  

o At  the  end  of  systole  BP  in  the  ventricles  drop  slightly  below  that  of  BP  in  the  aorta   causing  a  little  bit  of  blood  to  be  pushed  back  and  making  the  aortic  valve  close.  The   closing  of  the  valve  causes  a  slught  uncrease  in  aortic  BP  known  as  dicrotic  notch  or   incisura.  Through  diastole  aortic  BP  continues  to  decrease  until  it  reaches  80  mm  Hg   prior  to  systole  where  it  peaks  at  120  mm  Hg.  

o Sound:  

 Lubb:  closing  of  AV  valves  

 Dub:  closing  of  aortic  and  pulmonary  valves   • Heart  Regulation  

o Intrinsic  Heart  Regulation  Factors:  are  independent  of  neural  and  hormonal  factors    The  volume  of  blood  returning  to  the  heart  (venous  return)  during  diastole  

affects  the  amount  of  blood  that  will  be  ejected  from  the  ventricles  during   systole.  

 Increased  venous  return  makes  increased  end-­‐diastolic  volume  and  increased   stretch  of  the  ventricular  walls,  known  as  preload.  Greater  preload  means   grater  cardiac  output.  

 Cardiac  muscle  like  skeletal  muscle  exhibits  a  stretch  vs.  tension  relationship   but  it  is  not  stretched  optimally  prior  to  contraction  under  normal  end-­‐diastole   volumes.  When  preload  increases  the  muscle  stretches  more  and  the  force  of   contraction  and  stroke  volume  are  increased.  

 Starling’s  law  of  the  heart  correlates  the  effectiveness  of  heart  pumping  with   preload  volume  changes.    

• Increased  blood  volume  returned  to  heart;  increased  cardiac  muscle   stretch,  increased  contraction  force,  slightly  increased  heart  rate,   increased  stroke  volume  and  hence  increased  cardiac  output.   • Decreased  blood  volume  returned  to  the  heart;  decreased  cardiac  

muscle  stretch,  slightly  decreased  heart  rate,  decreased  stroke  volume   and  hence  decreased  cardiac  output.  

 When  the  right  atrium  is  stretched  to  a  greater  extent  as  a  result  of  greater   blood  being  returned  to  it  by  the  very  large  systemic  veins,  this  stimulates  the   SA  node  (because  it  is  located  in  the  right  atrium)  to  generate  action  potentials   at  a  higher  rate.  

• The  direct  effect  is  to  increase  the  Ca+2  of  the  cells  comprising  the  SA  

node  making  it  produce  more  action  potentials  per  unit  time.    There  are  forces  that  resist  the  ejection  of  blood  from  the  ventricles  like  the  

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 Afterload:  aortic  pressure  force  that  the  left  ventricle  must  overcome  to  eject   blood  into  this  artery.  The  effect  of  afterload  is  insignificant  as  long  as  it  doesn’t   exceed  170  mm  Hg,  at  this  point  the  capacity  of  the  ventricles  to  pump  blood  is   negatively  impacted.  

 Increased  physical  activity  stimulates  dilation  of  blood  vessels  so  that  an   increase  in  blood  volume  movement  results.  

 The  contraction  of  skeletal  muscles  in  the  arms  and  legs  and  other  areas  in   which  veins  are  embedded  accounts  for  most  of  the  blood  returned  to  the  atria.  

• During  elevated  physical  activity  they  contract  more  often  and   therefore  return  more  blood.  

 Valves  within  the  veins  prevent  the  backflow  of  blood   o Extrinsic  Heart  Regulation  Factors:  

 Two  divisions  of  the  autonomic  nervous  system  innervate  the  heart.   • Parasympathetic  can  decrease  heart  output  by  10-­‐20%,  having  an  

inhibitory  effect.  

o The  parasympathetic  fibers  are  contained  in  the  vagus  nerve.   Preganglionic  extend  to  the  ganglia  in  the  heart  wall  and  the   Postganglionic  extend  to  the  SA  and  AV  nodes,  myocardium  and   coronary  blood  vessels.  

o The  heart  can  decrease  to  20-­‐30  beats  per  minute  through  more   forceful  stimulation  than  usual.  

o If  the  rate  of  volume  returned  is  constant  stroke  volume  may  be   increased  because  the  heart  has  more  time  to  strech  and  fill   with  blood  since  it  is  beating  slower.  

o Releases  acetylcholine  which  bind  to  acetylcholine-­‐gated  K+  

channels  causing  it  to  open  and  thus  hyperpolarizing  the  cells   making  it  harder  to  depolarize  them  and  giving  required  more   time  to  achieve  depolarization.  

• Sympathetic  can  increase  heart  output  by  50-­‐100%.  

o Fibers  originate  in  thoracin  nerves  (T2,  T3,  T4)  sinapse  with   cervical  and  upper  thoracic  ganglia,  the  postganglionic  fibers   extend  to  the  myocardium.  

o Called  cardiac  nerves  they  innervate  the  SA  node,  the  AV  node,   cornary  blood  vessels,  and  ventricle  myocardium.  

o Causes  the  heart  rate  and  contraction  force  to  increase   maintaining  it  at  a  20%  greater  force  than  in  the  absence  of   these  nerves.  

o Heart  rate  can  increase  to  250-­‐300  beats  per  minute.  

o Stroke  volume  may  increase  as  well  but  beyond  a  certain  heart   rate  the  blood  volume  will  diminish  because  of  a  shortened   diastole  decreasing  the  stroke  volume.  

o Norepinephrine  interacts  with  beta-­‐andregenic  receptors  and   causes  increased  production  and  accumulation  of  cAMP  which   increases  cardiocyte  permeability  to  Ca+2  through  the  opening  

of  cardiocyte  membrane  slow  calcium  channels.  

 Estrinsic  factors  can  regulate:  blood  pressure,  blood  O2  levels,  blood  CO2  levels,  

and  blood  pH  by  negative  feedback.    Hormonal  Extrinsic  Heart  Regulation:  

• Adrenal  Medulla  secretes  epinephrine  and  norepinephrine  due  to   sympathetic  stimulation.  The  hormones  travel  through  the  bloodstream   into  the  heart  and  bind  to  beta-­‐andregenic  receptors.  

• Relationship  of  Heart  Function  to  Maintenance  of  Homeostatic  Parameters  

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 Cardioregulatory  center  of  the  medulla  oblongata  receives  messages  from  these   receptors;  it  increases  heart  rate  via  its  cardioacceleratory  center  and  

decreases  it  through  its  cardioinhibitory  center.  

 When  bp  increases,  the  vessel  walls  stretch,  more  signals  are  sent  from   baroreceptors  to  the  cardioregulatory  center,  it  sends  action  potentials  along   the  parasympathetic  nerve  fibers  stimulating  a  slower  beating  of  the  heart.    When  bp  decreases,  the  vessel  walls  stretch  less,  less  signals  are  sent,  the  

cardioregulatory  center  sends  action  potentials  through  the  sympathetic  nerve   fibers.  

 This  is  termed  the  baroreceptor  reflex.  

o Chemoreceptor  Reflex:  detects  changes  in  pH  and  CO2  levels  through  chemorepectors  

that  are  located  in  the  medulla  oblongata.  

 A  decrease  in  blood  pH  and  increase  in  CO2  levels  causes  it  to  send  messages  

through  sympathetic  nerve  fibers  so  that  heart  rate  can  be  increased,   increasing  the  rate  at  which  CO2  can  be  exhaled.  

 There  are  chemoreceptors  in  the  carotid  and  aortic  arteries  that  detect  low   oxygen  levels.  These  cause  the  heartbeat  to  decrease  and  narrow  the  blood   vessels  via  vasoconstriction  decreasing  the  heart’s  need  for  oxygen.  

o Ions  can  affect  heart  rate  and  stroke  volume.  

 Increased  levels  of  potassium  can  bring  heart  block,  loss  of  action  potentials.   o Elevated  temperature  will  somewhat  increase  heart  rate.  

• The  Blood  Vessels   o Capillaries  

 Smallest  and  most  extensive  of  all  blood  vessels.    Average  diameter  of  7-­‐9  µm,  and  1mm  in  length.  

 Made  up  of  a  single  cell  layer  of  endothelial  cells,  simple  squamous  epithelial   cells,  the  same  ones  that  line  the  surface  of  the  chambers  of  the  heart  and  the   innermost  layer  of  all  blood  and  lymph  vessels.  

 The  lumen  of  the  capillaries  is  occupied  by  blood.    The  endothelial  cells  rest  upon  a  basement  membrane.  

 Adventitia:  loose  connective  tissue  surrounding  the  peripheral  margins  of  and   joining  to  the  basement  membrane.  

 Percapillary  cells  occur  intermittently  between  the  endothelial  cells  and  the   basement  membrane.  Fibroblasts,  macrophages,  undifferentiated  smooth   muscle  cells.  

 Three  forms  of  capillaries:   • Continuous  capillaries:  

o Diameter:  7-­‐9  µm.  

o No  spaces  between  endothelial  cells  which  make  this  capillaries   less  permeable  to  molecules.  

o Common  throughout  the  body;  nervous  and  muscle  tissues.   • Fenestrated  Capillaries:  

o Diameter:  0.07-­‐0.1  µm  

o Very  porous  and  thin  cell  membrane  due  to  fenestrae  (pores  in   the  endothelium  wall).  

o In  tissues  that  require  very  permeable  capillaries;  intestinal   villi,  glomeruli  of  the  kidney,  CNS  coroid  plexus.  

• Sinousoidal  capillaries:   o Diameter:  9  µm  

o Less  developed  basement  membrane.  

o Larger  fenestrae  than  fenestrated  capillaries.  

o Tissues  that  require  large  molecules  to  be  moved;  endocrine   glands  

o Sinusoids:  sinusoidal  capillaries  with  a  large  diameter    Can  move  large  molecules  and  even  cells  in  some  

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 common  in  liver  or  bone  marrow.   o Venous  Sinuses:  

 Even  greater  diameter.    Common  in  the  spleen.  

 Large  spaces  occur  between  cells.  

 Arterioles  supply  blood  to  capillaries  which  form  a  network  that  occurs   throughout  tissues  until  the  capillaries  begin  to  form  venules  which  return   blood  to  the  heart.  

 Arterial  capillaries:  occurring  closest  to  arterioles    Venous  capillaries:  occurring  closest  to  venules  

 Precapillary  Sphincters:  smooth  muscles  that  occur  at  the  junction  of  an   arteriole  and  a  capillary,  it  will  constrict  or  dilate  the  capillary  by  constriction   and  relaxation  of  the  muscle.  

o Arteries  and  Veins  

 Contain  three  tissue  layers:   • Tunica  intima  

o Endothelial  cells  surrounded  by  basement  membrane   o Sorrounded  by  a  thin  layer  of  connective  tissue  called  the  

lamina  propia.  

o Elastic  fibers  form  the  internal  elastic  membrane,  which   separates  the  tunica  intima  from  the  next  layer;  tunica  media.   • Tunica  media  

o Made  up  of  smooth  muscle  cells,  if  they  contract  

vasoconstriction  occurs  and  the  volume  of  blood  flow  is   diminished,  if  they  relax  vasodilation  occurs  and  there  is  an   increase  in  blood  flow.  

o Collagen  and  elastic  fibers  are  also  preset  but  vary  in  abundance   according  to  each  particular  vessel.  

• Tunica  externa  (tunica  adventitia)  

o Made  up  of  connective  tissue,  it  can  be  dense  or  loosely,  that   joins  connective  tissue  surrounding  the  blood  vessel.  

o Arteries  

 Large  elastic  arteries   • Closest  to  the  heart  

• Bp  fluctuates  according  to  diastole  and  systole  

• Tunica  media  not  well  developed  to  prevent  vasoconstriction.   • Elastic  tissue  well  developed  facilitating  expansion  and  contraction  

between  systole  and  diastole.   • Tunica  intima  well  developed.   • Tunica  adventitia  thin.  

 Muscular  arteries  

• All  arteries  that  are  too  small  to  be  considered  large  elastic  ones.   • Thick  walls  

• Tunica  media  is  made  up  of  25-­‐40  layers  of  smooth  muscle.   • Elastic  membrane  of  Tunica  intima  is  well  developed.   • Tunic  adventitia  thick  collagenous  layer.  

• Distributing  arteries:  medium-­‐  sized  muscular  arteries.  

Vasoconstriction  and  vasodilation  enable  them  to  regulate  blood  flow  to   various  tissues  and  organs.  

• The  smaller  ones  of  40  µm  in  diameter  have  a  tunica  media  comprised   of  3-­‐4  smooth  muscle  layers.  

o Arterioles  

 Lead  from  small  muscular  arteries  to  capillaries.    Three  tunic  layers  are  recognizable.  

 Tunica  intima  lacks  elastic  membrane.  

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 Vasoconstriction  and  vasodilation  regulate  blood  flow.   o Veins  and  Venules  

 Venules:  

• Receive  blood  from  capillaries,  to  which  they  are  similar  in  structure   except  for  the  diameter  which  is  40-­‐50  µm  for  these  vessels.  

• Endothelium  surrounded  by  a  basement  membrane.  

• Smooth  muscle  cells  surround  the  endothelium  intermittently.   • Nutrients  can  cross,  but  their  capacity  to  do  so  decreases  with  

increasing  vein  size.    Small  veins  

• 200-­‐300  µm  in  diameter.  

• Completely  surrounded  by  a  alayer  of  smooth  muscle.  

• Tunica  adventitia  comprised  of  collagenous  connective  tissue.  

• All  veins  grater  than  200  µm  in  diameter  have  valves  that  allow  blood   to  flow  only  in  the  direction  of  the  heart.  

 Medium  veins:  diameter  in  between  small  and  large  veins.    Large  veins:  

• Transport  bloos  from  medium  veins  to  heart.   • Thin  tunica  intima.  

• Tunica  adventitia  best  develop  tissue  layer,  comprised  of  collagenous   connective  tissue.  

o Vasa  vasorum:  

 Small  blood  vessles  that  supply  nutrients  to  the  walls  making  up  arteries  and   veins  with  diameter  in  excess  of  1  mm  by  forming  a  network  of  capillaries  in   the  tunica  media  and  the  tunica  adventitia.  

• Nervous  Regulation  of  Blood  Vessels:  

o Sympathetic  nerve  fibers  innervate  the  majority  of  blood  vessel  walls  via  unmyelinated   nerve  axons.  

o Sympathetic  stimulation  causes  vasoconstriction,  parasympathetic  stimulation  results   in  vasodilation.  

o Adjacent  smooth  muscle  cells  have  cytosols  linked  via  gap  junction  so  stimulation  can   cause  a  large  portion  of  a  vessel  to  constrict.  

o Enlarged  nerve  axons  synapse  with  smooth  muscle  cells  in  the  tunica  media.   • Pulmonary  Circulation:  

o Blood  is  ejected  from  the  right  ventricle  into  the  pulmonary  trunk.  

o Pulmonary  trunk  gives  way  into  the  right  and  left  pulmonary  arteries,  which  take  the   blood  to  the  right  and  left  lungs.  

o The  blood  then  passes  to  capillaries  that  encircle  alveoli  (terminal  sacs  at  the  end  of  the   bronchioles,  the  smallest  ling  air  passageways).  

o In  here  oxygen  diffuses  into  the  blood  and  carbon  dioxide  difuses  out.  

o From  the  capillaries  the  blood  moves  to  venules,  small  veins,  medium  veins,  large  veins   called  theright  and  left  pulmonary  veins  that  direct  the  blood  to  the  left  atrium  so  it  can   be  passed  to  the  left  ventricle  and  then  the  systemic  circulation.  

• Systemic  Circulation:  

o Recieves  oxygen-­‐rich  blood  in  the  aorta  as  it  is  pumped  in  the  left  ventricle.  

o Distributes  it  through  the  body  directing  it  through;  large  elastic  artery  branchings  of   the  aorta,  muscular  arteries,  arterioles,  and  capillaries.  Through  this  path  oxygen   diffuses  from  higher  concentration  in  the  blood  plasma  to  lower  concentration  in  the   interstitial  fluid,  then  to  lower  concentration  as  it  diffuses  into  the  cells  and  then  the   mitochondria.  

o Carbon  Dioxide  diffuses  form  the  cells  towards  the  interstitial  fluid  and  then  towards   the  capillaries,  venules,  small  veins,  medium  veins,  and  large  veins.  

o The  superior  and  inferior  vena  cava  return  the  blood  to  the  right  atrium  from  where  ir   re-­‐enters  the  pulmonary  circulation.  

• Systemic  Arteries:  

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 Ascending  aorta:  2  inches  long.  

• The  right  and  left  coronary  arteries,  which  supply  the  heart  with  fresh,   oxygen-­‐rich  blood,  branch  from  this  part  of  the  aorta.  

 Aortic  arch:  posteriorly  directed  arch  to  the  left.  

• Branchicephalic:  branches  at  the  level  of  the  clavicle  to  form  the  right   common  carotid  artery,  which  directs  blood  to  the  right  side  of  the  head   and  neck.  

•  Common  carotid  artery:  

o Left  common  carotid  artery:  transports  blood  to  the  left  side  of   the  head  and  neck.  

o Right  common  carotid  artery   • Subclavian  artery:  

o Left  subclavian  artery:  transports  blood  to  the  left  upper  limb.    Descending  aorta:  

• Longest  portion,  extends  through  the  torax,  abdomen  and  above  the   pelvis.  

• Thoracic  Aorta:  occurs  within  the  torax.  

o Left  and  right  bronchial  arteries  supply  the  left  and  right  lungs.   o Esophageal  arteries  supply  the  esophagus.  

o Posterior  intercostals  supply  the  thoracic  walls  

• Abdominal  Aorta:  between  diaphragm  and  part  of  the  descending  aorta   that  gives  way  to  the  two  common  iliac  arteries.  

o Common  Iliac  arteries:  

 External  iliac  supplies  the  lower  limb  

 Internal  iliac  supplies  the  hip,  pelvis,  lower  back,  urinary   bladder,  vagina,  uterus,  rectum,  and  external  genitalia.   • Systemic  Veins:  

o Superior  Vena  Cava:  returns  systemic  blood  from  the  head,  thorax,  neck,  and  upper   limbs  

o Inferior  Vena  Cava:  returns  blood  from  the  abdomen,  pelvis,  and  lower  limbs.   o Coronary  sinus:  returns  blood  from  the  heart  walls.  

 Cardiac  Veins:  drain  blood  from  the  heart  walls  to  the  coronary  sinus.   o Major  veins  that  return  blood  to  the  superior  and  inferior  vena  cava:  

 Right  and  Left  Brachiocephalic  veins:  receive  blood  from  the  internal  and   external  jugular  veins  

• External  Jugular  Vein:  from  head  and  neck  region  to  the  left   brachiocephalic  vein  

• Internal  Jugular:  from  cranium,  anterior  head,  face  and  neck  to   subclavian  veins.  

o The  joining  of  these  to  the  left  and  right  subclavian  veins  from   the  brachiocephalic  veins.  

• Right  and  Left  subclavian  veins:  from  upper  extremities  to   brachiocephalic  vein.  

• Internal  Thoracic  veins:  receive  blood  by  anterior  intercostal  veins  and   drain  to  brachiocephalic  veins  

o Anterior  intercostal  veins:  from  anterior  thoracic  wall  to   internal  thoracic  veins  

 Renal  Vein:  from  kidney  to  inferior  vena  cava  

 External  and  Internal  Iliac  veins:  from  lower  limbs,  join  to  form  common  iliac   veins,  which  drain  to  the  inferior  vena  cava.  

 Femoral  veins:  from  lower  limbs  to  external  iliac  veins.   • Vessels  of  the  Lymphatic  System:  

o Lymphatic  System:  drains  the  interstitial  fluid  away  from  the  tissues  of  the  body.   o Lymph:  interstitial  fluid  inside  the  lymph  vessels  

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o The  simple  squamous  endothelial  cells  of  the  lymph  capillaries  have  a  looser  

association  with  one  another  making  them  especially  permeable  to  the  interstitial  fluid   (it  does  not  easily  flow  back  out  because  they  work  like  valves).  

o Lymph  vessels  are  lacking  in  CNS,  tissues  that  lack  blood  vessels  and  bone  marrow.   o Interstitial  fluid  forms  via  bulk  flow  from  a  greater  pressure  inside  the  capillaries  and  

towards  a  lower  pressure  outside.  

o Lymph  capillaries  unite  to  form  larger  lymph  vessels  that  contain:  endothelial  cells   forming  the  inner  layer,  elastic  membrane  surrounding  the  endothelial  cells,  a  middle   layer  consisting  of  smooth  muscle  surrounded  by  elastic  fibers,  and  thin  fibrous   connective  tissue  comprising  the  outermost  layer.  Smaller  vessels  have  regularly   spaced  bulges  due  to  the  one-­‐way  valves.  

o Mobility  of  lymph  is  thought  to  result  from:  contraction  of  the  surrounding  skeletal   muscles,  contraction  of  the  smooth  muscle  making  up  the  lymph  vessel  middle  layer,   thoracic  pressure  changes  resulting  from  respiration.  

o Lymph  nodes  occur  intermittently  along  the  lymphatic  system  vessels.  

 Function  as  filtering  stations  removing  bacteria  and  other  disease-­‐causing   agents;  this  is  critical  because  the  lymph  returns  to  systemic  circulation   through  the  right  or  left  subclavian  vein  and  thus  become  plasma  again.  

o As  lymph  vessels  progress  towards  the  subclavian  veins  they  unite  and  become  larger.    The  vessels  from  the  right  limb  and  the  right  side  of  the  head  and  neck  direct  

lymph  to  the  right  lymphatic  duct  (smaller  than  the  thoracic  duct).   • If  an  individual  has  more  than  one  the  first  one  will  drain  into  the  

subclavia  vein  while  the  additional  two  drain  into  the  right  internal   jugular  vein  and  the  brachiocephalic  vein.  

 The  thoracic  duct  receives  lymph  from  all  other  areas  of  the  body;  thorax,   abdomen,  lower  limbs,  left  upper  extremity,  and  left  side  of  the  head  and  neck.   o The  thoracic  duct  enlarges  to  form  the  cisterna  chili  in  the  upper  abdominal  region;  

this  portion  receives  lymph  from  the  abdomen  and  the  lower  limbs.   • Lymphatic  System  Function  

o Fluid  balance  in  the  body.   o Absorbtion  of  ingested  fat  

 Lymph  vessels  called  lacteals  received  the  absorbed  products  of  lipid  digestion   from  epithelial  cells  of  small  intestine.  

o Defense  by  filtering  microorganisms  and  other  substances  from  the  lymph.    Lymph  nodes  receive  lymph  from  an  afferent  lymph  vessel  filter  it  and  the  

lymph  exits  through  an  efferent  lymph  vessel.  

 Lymph  nodes  are  especially  abundant  in  the  inguinal  nodes  of  the  groin  area,   auxiliary  nodes  in  the  armpit  area,  and  cervical  nodes  in  the  neck  region.   o Lymph  node:  

 Capsule:  layer  of  dense  connective  tissue  that  surrounds  the  lymph  node    Trabeculae:  delicate  extensions  of  the  capsules  that  establish  an  internal  

skeleton  within  the  lymph  node.  

 Reticular  fibers  from  a  fibrous  network  beteen  the  trabeculae  and  the  capsule.   Theese  make  up  the  tissues  of  the  lymph  with  lymphocytes  and  macrophages.    Lymph  sinuses  are  areas  containing  only  reticulated  fibers.  

 Outer  region  is  called  cortex  and  it  is  comprised  of  lymph  tissues  separated  by   more  diffuse  lymphatic  tissues,  trabeculae,  and  lymph  sinuses.  

 The  inner  region  is  de  medulla  and  it  is  made  up  of  branched,  diffuse  lymphatic   tissues  called  medullary  cords.  

 The  presence  of  microorganismso  stimulates  the  proliferation  of  lymphocytes,   these  newly  generated  lymphocytes  can  leave  the  blood  and  travel  to  other   lymphatic  tissues.  

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o A  fibrous  capsule  surrounds  the  spleen;  trabeculae  extend  in  from  the  inner  portion  of   the  spleen.  

 Red  Pulp:  associated  with  venous  blood    White  Pulp:  associated  with  arterial  blood    Functions:  

• Formation  and  storage  of  RBC   • Breakdown  of  old  RBC  

• Storage  of  half  of  the  body’s  monocytes  (can  become  macrophages  and   enter  lymph  nodes)  

• Contains  only  efferent  lymphatic  vessels  making  it  possible  to  pass   monocytes  destined  to  become  macrophages.  

o Thymus  gland  is  bilobed  and  located  near  the  sternum,  it  grows  until  puberty,   produces  lymphocytes.  

• Factors  Affecting  Blood  Circulation:  

o Pressure,  flow,  resistance,  and  mechanisms  regulating  blood  flow  affect  Blood   circulation.  

o We  can  regard  a  linear  portion  of  blood  within  a  vessel  as  being  made  up  of  a  series  of   cross-­‐sectional,  ring-­‐shaped  liquid  layer  from  the  wall  of  the  vessel  towards  the  center.   o The  layers  nearest  the  wall  experience  grater  resistance  and  move  slower.  

o Laminar  flow:  streamlined  flow  of  a  fluid  through  a  tubular  structure.  

o Laminar  flow  is  disrupted  by  constriction,  an  uneven  surface,  a  sudden  turn,  or  some   such  change  in  the  character  of  the  vessel  and  results  in  turbulence.  

o Rate  of  blood  flow  is  the  volume  of  blood  moving  through  a  vessel  segment  per  unit   time  (L/min).  

o In  order  to  blood  flow  there  must  be  a  difference  in  pressure  between  two  points  in  a   vessel,  and  it  is  countered  by  resistance  to  this  flow.  

o Pouiseuille’s  Law:  Q=  ΔP  r4  π/  ηL  8  

 Q:  Blood  Flow  

 ΔP:  pressure  difference  between  two  points  

 L:  length  between  the  two  points    r:  radius  of  the  blood  radius  

 π:  3.14  

 η:  Liquid  viscosity:  fluid’s  resistance  to  flow  

o Blood  viscosity  is  the  result  of  it’s  cellular  component  called  hematocrit  which  makes  it   three  times  as  viscous  than  water.  

o Critical  closing  pressure:  pressure  at  which  a  blood  vessel  collapses  causing  tissues  to   be  deprived  of  blood  and  making  them  susceptible  to  be  necrotic.  

o Law  of  LaPlace:  the  force  causing  a  vascular  wall  to  stretch  is  proportional  to  both   blood  vessel  diameter  and  blood  pressure.  

 F  =  D  x  P  

 F:  force  required  to  move  the  blood    D:  diameter  of  blood  vessels  

 P:  blood  pressure  

o In  areas  of  the  blod  vessel  that  have  been  weakened  an  aneurism  can  form,  this  is  a   bulge  that  results  from  pressure  pushing  on  that  wall  area.  

o Compliance:  a  vessel’s  tendency  to  increase  in  volume  in  accordance  with  increased  bp.    C  =  ΔV/  VP  

 Blood  vessels  with  high  compliance  stretch  in  response  to  little  pressure   increase,  the  ones  that  exhibit  low  compliance  stretch  little  in  response  to   pressure  increases.  

o Veins  have  a  higher  level  of  compliance  than  arteries  and  are  used  as  blood  storage   areas,  more  blood  is  found  in  veins.  

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o There  is  a  direct  relationship  between  arterial  pressure  decreases  in  the  systemic   circulation  and  resistance  to  blood  flow,  the  further  from  the  aorta  the  greater  the   resistance  to  flow.  

o Pulse  Pressure:  difference  between  systolic  and  diastolic  pressures,  heart  stroke   volume  (directly  related)  and  vascular  compliance  (inversely  related)  factor  into  pulse   pressure.  

o Capillaries  deliver  nutrients  and  remove  wastes.  BP  in  the  capillaries  is  more  than  in   the  surrounding  interstitial  fluid  and  thus  fluid  moves  into  the  interstitial  space  via   bulk  flow  and  fluid  is  moved  into  the  capillaries  via  osmosis.  

o The  plasma  is  much  higher  in  dissolved  proteins  tha  canoot  exit  the  capillaries  and  so   the  blood  osmotic  pressure  moves  water  and  smaller  solubilized  substances  from  the   interstitium  into  the  capillary.  There  is  a  net  loss  of  capillary  fluid  and  a  net  gain  of   interstitial  fluid.  

o Because  of  pressure  difference  (higher  at  capillary  arteriole  junction)  more  interstitial   fluid  entering  the  capillary  via  osmosis  near  the  capillary-­‐venule  end.  

o Gravity  increases  BP  when  standing  causing  more  fluid  to  leave  the  vessel.   • Regulation  of  Blood  Flow  in  Tissues:  

o Can  be  controlled  by:    nervous  system  

 mechanisms  within  close  proximity  to  those  tissues  receiving  blood    both  of  the  above  

o How  these  factor  affect  depend  upon  the  metabolic  state  of  the  body.  

o Blood  flow  to  the  skin  can  function  to  cool  the  body  through  heat  dissipation.   o Various  stimuli  cause  changes  in  blood  flow  to  tissues.  (Table  XIII.1  p421)   o Hormonal  regulation  result  from  increased  epinephrine  and  lesser  amounts  of  

norepinephrine  from  the  adrenal  medulla.   • Blood,  a  Fluid  form  of  connective  tissue  

o Formed  element:  cellular  blood  component  45%  of  the  blood    95%  erythrocytes  (25%  of  the  total  cells  of  the  body)  

• biconcave  disk  shape  provides  a  higher  surface  area  to  low  volume  ratio   that  facilitates  rapid  diffusion.  

• 7.5  µm  in  diameter   • lack  a  nucleus  

• filled  with  hemoglobin  

• transport  oxygen  and  carbon  dioxide   • cannot  reproduce  

 5%  leukocytes  

• Spherical  Shape  

• nucleus  but  lack  hemoglobin   • five  different  forms  

o Granulocytes:  cytolasms  contain  granule  like  structures    Neutrophils  

• nucleus  made  up  of  four  lobes  joined  to  one   another  via  thin  filaments  

• Phagocytize  

• 10-­‐12  µm  diameter  

• Granules  stain  pink  to  redish-­‐purple  when   stained  with  a  neutral  agent  

 Basophils  

• Nucleus  made  up  of  two  lobes  that  are  not   clearly  distinguished.  

• Puerple  stained  granules  with  basic  agent.   • 10-­‐12  µm  diameter  

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 Eosinophils  

• nucleus  made  up  of  two  lobes  

• Granules  stained  orange  to  bright  red   • 11-­‐14  µm  diameter  

• Inflammatory  response,  attacks  certain  parasitic   annelids  

o Agranulocytes    Lymphocytes  

• Spherical  nucleus  

• Establishes  a  thin  preiperal  margin  about  the   nucleus  6-­‐14  µm  

• Releases  antibodies  that  kills  invasive  agents,   important  component  of  allergic  reactions,   controls  the  immune  system  

 Monocytes  

• Nucleus:  spherical,  kidney-­‐like,  horseshoe-­‐like   • Cytoplasm  makes  up  a  greater  amount.  

• 12-­‐20  µm  diameter   • phagocytizes   o Platelets:  

 Portions  of  cells  enclosed  in  a  membrane.    Contain  granules.  

 2-­‐4  µm  diameter  

 cause  blood  to  clot  and  release  chemicals  that  modulate   the  clotting  of  blood  

o Plasma:  liquid  matrix  55%  of  the  blood  

 Made  up  of  91%  water  and  9%  non-­‐water  substances.  

 Colloidal  solution:  made  up  of  suspended  material  that  does  not  settle  out  of   solution.  

 Composed  of:   • Proteins:  

o Albumin:  maintains  blood  viscosity  and  osmotic  pressure,   regulates  pH  functions  as  a  buffer.  

o Globulin:  movement  of  various  nutrients,  ions,  and  hormones;   also  functions  as  components  of  the  immune  system  

o Fibrinogen:  clotting  properties  

• Ions:  form  membrane  potentials,  generate  action  potentials,   maintenance  of  blood  pH.  

• Nutrients:  glucose,  amino  acids,  cholesterol,  triacylglicerol,  and   vitamins  

o promote  metabolic  activities   • Wastes:  

o H+,  uric  acid,  NH3,  NH4+,  creatinine;  removed  through  the  

kidneys  

o Bilirubin:  degraded  RBC,  incorporated  into  bile  and  excreted   from  the  body  via  the  intestines.  

o Lactic  Acid:  can  be  metabolized  by  the  liver  into  glucose   • Gases:  

o Oxygen,  Carbon  Dioxide  

o Nitrogen:  majority  of  dissolved  gas  within  plasma   • Regulatory  Components:  

o hormones  and  enzymes   o Physiological  Roles  played  by  blood:  

 Maintenance:  pH,  distribution  of  heat  of  metabolism,  and  prevention  of  blood   loss  through  clotting  properties.  

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• Nutrients  (oxygen,  simple  sugars,  lipids  and  amino  acids)  

• Wastes  (carbon  dioxide,  broken  down  cells,  macromolecules,  smaller   molecule  ions)  

• Hormones  from  endocrine  tissue  to  target  cell   • Cells  conferring  immunological  properties.    Protection:  

• WBC  and  other  blood  components  eliminate  invasive  agents  that  could   compromise  the  function  of  or  destroy  the  body.  

• Loss  of  blood  is  also  prevented  through  clotting  properties  of  blood.   o Carbonic  anhydrase:  present  in  erythrocytes  and  catalyzes  the  conversion  of  water  and  

carbon  dioxide  into  carbonic  acid.  

 Blood  carbon  dioxide  is  transported  in  the  form  of  carbon  dioxide  so  that  the   concentration  gradient  makes  carbon  dioxide  is  moving  towards  the  blood.   o Each  hemoglobin  binds  4  oxygen  molecules;  280,000  hemoglobin  molecules  make  up  

an  erythrocyte.  

 When  carbon  dioxide  is  in  high  concentation  it  binds  to  heme  groups.  

o Erythropoietin:  glycoprotein  hormone  produced  by  the  kidney  synthesized  in  response   to  low  blood  oxygen  levels  causing  blood  erythrocytes  to  increase.  

Figure

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Referencias

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