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Lecture 8

BIO271 2014 Lecture 8.pdf

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Christopher Garside

  Lecture  8:  Circulatory  Systems  Part  1  –  Overview;  Components;   Diversity   Limits  of  Diffusion   -­‐ unicellular  organisms  and  some  small   metazoans  lack  circulatory  syste ms   o rely  on  diffusion   § rapid  over  small  distances,  but  is  very  slow  over  large  distances     § increase  distance  =  exponential  increase  of  time  required  to   cross   -­‐ large  animals  move  fluid  through  their  bodies  by   bulk  flow   o bulk  flow:  mass  movement  of  many  molecule s  together  (usually  from  an   area  of  high  pressure  to  a  region  of  low  pressure)   o transport  can  occur  faster  over  greater  distance   o requires  energy  to  increase  pressure  à  force  flow  from  an  area  of  high   pressure  to  low  pressure  (ex.  Heart)   -­‐ most  metazoans  large r  than  a  few  cells  have  circulatory  systems   o major  function   § transport  oxygen,  carbon  dioxide,  nutrients,  waste  products,  immune  cells,  and  signaling   molecules  throughout  the  body   -­‐ circulatory  systems  move  fluids  by  increasing  the  pressure  of  the  fluid  in  one  part  of  the  body   o fluid  flows  through  the  body,  “down”  the  pressure  gradient   o circulatory  systems  want  to  flow  unidirectionally  (pick  up  what  we  want  in  one  place,  and  drop  it  off   somewhere  else,  pick  up  the  waste  there)   o circulatory  systems  have  one  way  valves  (valves  that  can  only  open  in  one  direction)   o increase  in  pressure  in  one  chamber  causes  the  valves  to  open  in  only  1  direction  =  unidirectional  flow  of   fluids  around  the  body   o fluid  flows  through  the  body  down  pressure  gradients   o no  pressure  gradient?  Fluid  will  flow  randomly     Components  of  Circulatory  Systems   1. pump  or  propulsive  structures   -­‐ must  have  a  pump  to  develop  the  high  pressure   -­‐ for  ex.  A  heart   2. systems  of  tubes,  channels,  or  spaces   -­‐ a  way  to  get  from  the  heart  to  tissues   -­‐ one  way  valves  help  to  ensure  unidirectional  flow   3. fluid  that  circulates  through  the  system   -­‐ different  from  environmental  fluid     -­‐ for  ex.  blood   o substantial  diversity  in  the  structure  and  organization  of  these  components     Types  of  Pumps   -­‐ chambered  hearts   o contractile  chambers   § creates  the  high  pressure   § blood  enters  atrium   § blood  is  pumped  out  by  ventricle   § one  way  valves  allow  for  unidirectional  flow   -­‐ skeletal  muscle  (external  pump)   o brings  blood  back  to  the  heart   o squeeze  on  vessels  to  generate  pressure   o squeeze  on  blood  vessels  (mainly  veins)   à  unidirectional   -­‐ pulsating  or  contractile  blood  vessels   o peristalsis   § rhythmic  coordinated  contractions  of  vessel  wall  pumps  blood   § contraction  moves  forward,  while  relaxation  follows   à  coordinated   § if  peristalsis  is  well  coordinated,  you  wouldn’t  even  need  one  w ay  valves         Closed  and  Opened  Circulatory  Systems   -­‐ Open   o Circulatory  fluid  directly  contact  tissues   § Mixes  with  interstitial  fluid   § Hemolymph  à  directs  blood  to  specific  areas  of  the  body   (control)   § Hemocoel:  hemolymph  cavity   -­‐ Closed   o No  direct  contact  between  circulatory  fluid  and  tissues   § Distinct  from  interstitial  fluid  (between  tissues  and  blood)   o Molecules  must  diffuse  across  vessel  wall         Types  of  Fluid   -­‐ interstitial  fluid   o extracellular  fluid  that  directly  bathes  the  tissues   o becomes  lymph  once  it  enters  the  lymphatic  system   o lymphatic  system  returns  the  interstitial  fluid  back  into  the  venous  blood   flow   -­‐ blood  (closed  system)   o fluid  that  circulates  within  the  vessels  of  a  closed  circulatory  system   o in  an  open  circulatory  system,  its  hemolymph   -­‐ lymph   o fluid  that  circulates  in  the  secondary  circulatory  system  of  vertebrates;  the  lymphatic  system   o water  and  small  molecules  filter  out  of  small  blood  vessels  in  tissue  (ultrafiltration)  and  mix  with   interstitial  fluid   § ultrafiltrate  of  blood  plasma   § ultrafiltrate  mixes  with  t he  interstitial  fluid  and  drains  into  the  lymphatic  system   o lymph  is  pumped  through  lymphatic  system  and  back  into  primary  circulatory  system   -­‐ hemolymph   o fluid  that  circulates  in  an  open  circulatory  system     Body  Fluid  Compartments  (Human)   -­‐ total  body  water:  everything  external   to  the  body  doesn’t  count  (lungs,   kidneys,  digestive  tract  doesn’t   count)  à  42L  of  water   -­‐ intracellular  fluid:  2/3  of  body  water   is  found  within  cells  à  28L  out  of  the   42L  within  the  body  is  within  cells   o primary  contributor  to  total   body  water   -­‐ extracellular  fluid:  about  14L   à  the   other  1/3  of  total  body  water   o plasma  for  blood  (3L)  à  only   small  percent  of  the  total   body  water   o interstitial  fluid  –  fluid  that   surrounds  all  cells  à  11L  of   total  body  water     Bulk  Flow  in  Animals  Lacking  Circulat ory  Systems   § Not  a  true  circulatory  system   à  fluid  being   circulated  is  exactly  the  same  as  the  external  fluid   § But  external  fluid  has  all  the  oxygen  and  nutrients   they  need   -­‐ Sponge     o Flagellated  “choanocytes”  move  water   through  porocyte  into  body  cavity       § Choanocytes  produces  current  (almost  unidirectional  flow)   -­‐ Cnidarians   o Muscular  contractions  of  the  body  wall  pump  water  in  and  out  of  gastrovascular  cavity   -­‐ Flatworms   o Contractions  of  muscular  pharynx/body  wall  propel  fluid  through  gastrovascular  cavity   o Ciliated  flame  cells:  can  beat  like  Choanocytes   § Can  move  extracellular  fluid  to  all  the  tissues  in  the  body   o Pharynx:  only  part  that  has  communication  with  the  extracellular  fluid   à  all  comes  in  and  out  from  the   pharynx   -­‐ Lack  circulatory  systems  but  have  mechanisms  f or  propelling  fluids  around  their  bodies   -­‐ Bulk  flow  of  fluid  is  part  of  a  combined  respiratory,  digestive  and  circulatory  systems     Annelids  –  Majority  Closed   -­‐ 3  main  classes:   1) polychaete  –  tube  worms   -­‐ have  an  opened  circulatory  system   -­‐ peristaltic  contractions  release  blood  into  the  head  regions  of  this   animal   -­‐ hemolymph  percolates  back  through  the  body,  and  is  picked  up  and   returned  to  dorsal  vessels   -­‐ hemolymph  directly  baths  every  tissue   2) oligochaete  –  earth  worms     -­‐ closed  circualtory  system   -­‐ have  a  chmabered  heart(s)  –  pumping  blood  from  dorsal  vessel  to   ventral  vessel  to  all  the  tissues  of  the  body   3) hirudinia  –  leeches   -­‐ polychaetes  and  oligochaetes  circulate  interstitial  fluid  with  cilia  or   muscular  contractions  of  body  wall   o within  their  body’s,  cilia  moves  interst itial  fluid  around   o important  to  keep  moving  around  =  fresh  material  in  interstitial   fluid   o most  have  vessels  that  circulate  fluid  with  oxygen  carrier  protein   o circulatory  system  can  be  open  (polychaetes)  or  close  (oligochaetes)       Molluscs  –  Majority  Open   -­‐ all  have  hearts  and  some  blood  vessels   -­‐ most  have  open  systems   o blood  pumps  out  through  chambered  hearts,  through  blood  vessels,   into  sinuses  à  hemocoel  (where  hemolymph  baths  every  tissues  in  the   body)   -­‐ exception:  Cephalopods  (special  type  of  mollusk)   o very  active  mode  of  life  (these  animals  tend  to  have  closed  circulatory   systems)   o high  metabolic  rate     o circulatory  system  is  similar  to  birds  and  mammal  system   o multiple  hearts  pumping  blood  through  respiratory  surfaces   1. single  systemic  heart  pumping  blood  to  all  bod y  tissues,  blood  returns   to  a  pair  of  branchial  hearts   2. each  branchial  heart  pumps  blood  to  the  gills/across  the  gills   3. blood  returns  to  the  heart     Arthropods   -­‐ all  have  one  or  more  hearts  and  some  blood  vessels   -­‐ all  have  open  systems   -­‐ crustaceans   o has  a  single  dorsal  vessel   1. peristaltic  contractions  move  hemolymph  up  to  the  head  region   2. blood  is  released  to  the  hemocoel       3. fresh  hemolymph  percolates  back  to  through  the  body  tissues   4. picked  up  again  by  the  heart  and  circulates  again   o circulatory  system  become  more  comple x  in  larger  animalsà   structurally  open,  but  functions  like  a  closed  system   o small  sinuses  within  hemocoel  that  function  as  vessels   o some  control  over  distribution  of  blood  flow  in  body     -­‐ insects   o relatively  simple  open  circulatory  system   § but  high  metabolic  rate,  but  in  an  open  circulatory  system   it  cannot  have  it  high  because  it  cannot  rapidly  circulate   =   cannot  develop  high  pressure   § high  metabolic  rate  because  they  do  not  used  their  circulatory   system  for  respiratory  =  have  a  tracheal  system   § all  other  organisms  with  closed  circulatory  system,  use  their   circulatory  system  to  transport  respiratory  gases  to  active   tissues  à  insects  do  not  do  this  à  use  tracheal  system  to  diffuses   respiratory  gases  in  and  out   o multiple,  contractile  “hearts”  along  dorsal  vessel   o one  heart  per  segment  in  the  body  that  pumps  blood  up  into  the  head   region,  where  it  percolates  back  to  body  tissues   o also  have
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