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A&P Test 2

by: Allison Collins
Allison Collins
GPA 3.88

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This study guide is for the second test and covers monogastric and ruminant digestive systems, embryology, and the cardiovascular system.
Anatomy and Physiology of Domestic Animals
Dr. Kevin Downs
Study Guide
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This 36 page Study Guide was uploaded by Allison Collins on Sunday April 3, 2016. The Study Guide belongs to ABAS 3450 at Middle Tennessee State University taught by Dr. Kevin Downs in Winter 2016. Since its upload, it has received 51 views. For similar materials see Anatomy and Physiology of Domestic Animals in Agricultural & Resource Econ at Middle Tennessee State University.

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Date Created: 04/03/16
Monogastric  Digestive  Anatomical  Terminology   •   Salivary  glands  –  produce  salivary  amylase,  which  begins  digestion   o   Not  present  in  all  species   o   Saliva  =  mucus  +  water  (serous  fluid)     o   4  types  of  salivary  glands   §   Parotid  –  largest  glands     •   Produces  only  serous  fluid   •   Located  just  in  front  of  each  ear   §   Mandibular  –  medium-­‐sized   •   Produces  mix  of  mucus  and  serous   •   Located  along  jawline   §   Sublingual  –  medium-­‐sized   •   Produces  mix  of  mucus  and  serous   •   Located  beneath  tongue   §   Buccal  –  small   •   Produces  only  mucus   •   Branches  off  of  parotid  gland  toward  nose  –  multiple   branches   •   Esophagus  –  transportation  of  ingesta  from  mouth  to  stomach  by  means   of  peristalsis  (peristalsis  works  in  a  variety  of  systems)   •   Cardiac  sphincter  –  prevents  chyme  from  re-­‐entering  esophagus     o   Low  pH  from  stomach  would  burn  esophagus   o   Opens  and  closes   o   Opens  to  esophageal  region   •   Esophageal  region  of  stomach  –  produces  nothing   •   Cardiac  region  of  stomach  -­‐  food  enters  from  esophageal  region   o   Expanding  pouch     o   Produces  mucus,  stores  chyme  (stomach  contents)   •   Fundic  region  of  stomach  -­‐  food  enters  from  cardiac  region   o   Largest  portion  of  stomach   o   Produces  mucus,  pepsinogen,  HCl   o   Has  thick  tissue  (more  cells)  that  aids  in  acid  production   •   Pyloric  region  of  stomach  –  food  enters  from  fundic  region   o   Chief  cells  –  produce  pepsinogen   o   Parietal  cells  –  produce  HCl   o   Pepsinogen  inactive  until  it  combines  with  HCl   §   Pepsinogen  +  HCl  =  pepsin   §   Pepsin  breaks  peptide  bonds,  thereby  digesting  protein   •   Pyloric  sphincter  –  controls  movement  of  chyme  into  duodenum   o   Between  pyloric  region  and  duodenum   o   Too  much  chyme  will  overload  the  neutralizing  system   •   Stomach  mucosa  –  lining   •   Duodenum  –  digestion  of  nutrients   o   Closer  to  right  body  wall   o   Attached  to  pancreas  and  gallbladder  –  chyme  enters  here   •   Pancreas     o   Produces  NaHCO  (sodi3m  bicarbonate)  which  acts  as  a  buffer   by  neutralizing  chyme   §   Discharges  into  duodenum   o   Produces  enzyme  that  digests  carbs,  proteins,  lipids   o   Much  smaller  than  liver,  yellowish  in  color ,  has  one  or  two  lobes   2   o   Endocrine  component  produces  insulin  and  are  also  important  in   carb  digestion   •   Liver   o   In  most  cranial  part  of  the  abdomen   o   Largest  gland  in  the  body,  reddish-­‐brown  in  color   o   Produces  bile  and  plays  in  protein,  carb,  and  fat  metabolism   o   Products  of  digestion  pass  through  hepatic  cells  before  entering   into  bloodstream   o   Discharges  into  duodenum     •   Gall  bladder  –  stores  bile,  emulsifies  fat  –  i.e.  suspends/separates  lipids   to  increase  surface  area   •   Small  intestine   o   Mesenteric  fat   §   Mesentery  conveys  vessels  and  nerves     o   Jejunum  –  absorption  of  nutrients   §   Identifiable  by  mesenteric  fat  and  villi  (tiny  projections   that  increase  surface  area  for  absorption   o   Ileum  –  absorption  of  nutrients   §   Identifiable  by  villi   o   Jejunum  and  ileum  tissue  layers  (deep  to  artificial):     §   lumen  à  epithelial  cells  à  villi  à  mucosa  à  muscularis   mucosae  à  submucosa  à  circular  smooth  muscle  à  cells   of  Auerbach’s  nerve  plexus  à  longitudinal  smooth  muscle   à  serosa   •   Muscularis  mucosae  –  thin,  weak  muscle  that  moves   villi   3   •   Cells  of  Auerbach’s  nerve  plexus  –  coordinates   circular  and  longitudinal  smooth  muscle  to  contract   –  i.e.  controls  peristalsis   •   Submucosa  –  produces  NaHCO     3 •   Large  intestine   o   Cecum  –  fiber  fermentation   §   Dead-­‐end  pouch  at  junction  of  ileum  and  colon   §   Much  larger  in  horses  and  rabbits  (fibrous  diets)   o   Ascending  coil  of  large  intestine  –  shorter  –  first  part  of  colon   o   Descending  coil  of  large  intestine  -­‐  longer  –  last  part  of  colon   o   Ileo-­‐colonic-­‐cecal  junction  –  regulates,  by  particle  size,  where   particles  should  go   §   Large  particles  go  to  large  intestine   §   Fine  particles  go  to  cecum   o   Rectum  –  most  dorsal  of  GI  tract  –  opens  to  anus   •   Anal  sphincter   o   Internal  –  thickening  of  circular  smooth  muscle  –  involuntary   o   External  –  striated  muscle  –  voluntary  control                     4               5                                             6                                             7                       8                                                                     9   Ruminant  Digestive  System   Terminology   Esophagus     •   Function:  transports  foodstuffs  from  mouth  to  reticulorumen     •   Splits  reticulum  and  rumen       Esophageal-­‐reticulo-­‐rumen  orifice   •   At  ending  of  esophagus  –  the  opening  between  esophagus,  reticulum,   and  rumen  –  only  exists  during  swallowing  and  regurgitating   •   When  animal  is  not  swallowing  or  regurgitating,  the  sphincter  keeps   closed  and  an  orifice  exists  only  between  reticulum  and  rumen  –  i.e.   becomes  the  reticulo-­‐rumen  orifice   10   o   When  this  is  the  case,  food  passes  between  reticulum  and   rumen  (through  the  reticulo-­‐rumen  orifice)  and  does  not  pass   back  into  or  from  esophagus   Reticulum   •   Food  enters  from  esophagus   •   Function:  mixes  rumen  contents  and  forms  bolus  by  means  of  passing   foodstuff  back  and  forth  through  reticulo-­‐rumen  orifice   •   Mucosa  of  reticulum  is  distinctive  honeycomb  patterns   o   Cellulae  reticuli  -­‐  the  “ground”  of  the  four-­‐,  five-­‐,  or  six-­‐sided   cells  of  the  honeycomb  pattern   o   Crests  –  walls  of  the  cells;  about  1  cm  high   o   Cornified  papillae  –  small,  stiff  projections  in  reticulum  that  line   the  crests  and  floors  of  the  cells   §   Work  with  the  cellulae  reticuli  to  grasp  incoming   food/objects     11     Rumen     •   Food  enters  from  esophagus   •   Houses  bacteria,  protozoa,  and  yeast     •   Function:  fermentation  of  fibrous  material   o   High  fiber  feed  generally  correlates  with  lower  quality   feedstuffs,  so  a  ruminant  must  consume  a  large  amount  of  feed   for  sufficient  nutrients   12   §   This  is  the  reason  that  the  ability  to  ferment  fibrous   material  is  essential  to  wild  ruminant  survival   o   The  animal  itself  doesn’t  make  the  fiber-­‐digesting  enzymes  –  the   microbes  do   §   Symbiotic  relationship:  microbes  receive  food  and  shelter,   host  benefits  from  the  byproduct  of  microbial  digestion  of   fiber   •   Closely  related  to  reticulum  in  structure  and  function   o   Reticulorumen  has  pH  of  about  7  –  an  acidic  environment  would   kill  microbes   •   Blindsacs  –  2  chambers  at  caudal  end  of  rumen;  dorsal  and  ventral   o   Septa  –  walls  of  blindsacs   •   Rumen  papillae  –  increases  surface  area  for  absorption  of  the   byproducts  of  fiber  fermentation   o   Carpet-­‐like  appearance   Reticulo-­‐rumen-­‐omasal  orifice  –  opening  located  at  dorsal  end  of  omasum   Omasum   •   Absorbs  water  in  digesta  –  when  opened,  contains  dry  digesta   •   Has  a  putty-­‐like  consistency  on  palpation   •   Floor  of  omasum  is  smooth  except  for  tooth-­‐like  projections  that  guard   the  opening     o   These  are  called  the  omasal  horn  papillae     •   Omasal  laminae  –  layers  within  the  omasum  –  increase  surface  area  for   water  absorption     •   pH  of  about  7   Omasal-­‐abomasal  orifice  –  opening  to  abomasum  at  ventral  end  of  omasum   and  dorsocaudal  end  of  abomasum     13       14   Abomasum     •   Function:  protein  digestion   o   Protein  comes  from  the  microbes  that  die  from  the  acidity  of  the   abomasum  (pH  of  about  2)  –  walls  of  microbial  cells  break  down,   exposing  the  protein  within  and  making  it  available  for   absorption  by  the  ruminant   •   Produces  HCl  and  pepsinogen  (like  the  monogastric  stomach)   o   Pepsinogen  has  no  purpose  until  it  is  combined  with  HCl  –   combination  produces  pepsin,  which  aids  in  protein  digestion     •   Digesta  in  abomasum  is  wet   •   Function  is  closest  of  the  4  chambers  to  the  monogastric  stomach     Rumination   •   A  ruminant’s  modified  (compartmentalized)  stomach  is  vital  to  its   survivability   •   Constant  grazing  during  the  day  to  fill  rumen  with  food  as  quickly  as   possible  –  very  little  chewing     •   At  night,  grazing  ceases  while  animal  hides  from  predators   o   At  this  time,  rumination  occurs  and  food  is  digested   •   Rumination:  ingesting  feedstuffs  very  quickly,  regurgitating  bolus  into   mouth,  chewing,  swallowing  again,  repeating   •   Breakdown  of  food  increases  surface  area  for  microbe  digestion   Steps  of  rumination     1.  Prehension  –  taking  food  into  mouth  by  means  of  tongue,  lips,  teeth,  etc.   -­‐    varies  by  species   2.  Mastication  (chewing)  –  very  little  occurs  at  initial  intake  of  food   3.  Deglutition  –  swallowing   15   4.  Regurgitation   5.  Remastication  –  more  thorough  than  first  time   6.  Deglutition  –  swallowing  again   7.  Repeat     Fermentation  of  feedstuffs  in  rumen   Feedstuffs  include:  carbs,  proteins,  lipids,  vitamins,  minerals,  water   •   When  feedstuffs  enter  rumen,  they  are  immediately  attacked  by   microbes   Carbohydrates  –  2  types   •   Starch  (complex)/sugar  (simple)–  not  much  is  typically  consumed  by   ruminants   o   That  which  is  consumed  is  broken  into  glucose   (monosaccharides)   •   Fiber   o   Composed  of  cellulose  (digestible)  and  lignin  (not  digestible)     o   Most  of  a  ruminant’s  diet  is  fibrous     o   Breaks  down  into  glucose  (monosaccharides)   •   Byproducts  of  fiber  fermentation   o   Certain  vitamins,  such  as  Vitamin  K  and  B  complex     §   Pass  directly  into  omasum   o   Volatile  Fatty  Acids  (VFA’s)     §   Include  propionate,  acetate,  and  butyrate   §   Used  to  generate  ATP  –  absorbed  across  rumen  wall  into   bloodstream   §   At  cellular  level:  VFA’s  enter  cell  respiration  at  Krebs  Cycle   16   •   Don’t  go  through  glycolysis  as  there  is  not  much   glucose  in  a  ruminant’s  diet   o   CO 2 and  CH 4  (methane)  –  released  through  mouth  as  a  belch   (eructation)     §   Loss  of  energy  (heat)  –  benefit  of  heat  regulation   Protein   •   Some  protein  bypasses  rumen  degradation  and  goes  direc tly  to  omasum   •   When  degraded,  microbes  break  protein  into  peptides ,  then  further  into   amino  acids   o   Microbes  further  break  amino  acids  into  carbon  skeletons  and   nitrogen     o   Nitrogen  then  combines  with  hydrogen  to  form  NH3  (ammonia)   §   Some  NH3  passes  to  the  liver  then  to  the  kidneys  and  is   disposed  in  urine  as  excess  nitrogen   §   Some  NH3  is  recycled  through  the  salivary  glands   o   Microbes  put  carbon  and  NH3  back  together,  re -­‐forming  the   amino  acids   §   Amino  acids  combine  to  form  polypeptides,  then  protein   •   Protein  passes  into  omasum   •   This  process  allows  ruminants  to  consume  low-­‐quality  protein  and   convert  it  to  better-­‐quality  protein   •   Another  source  of  protein  is  the  microbes  themselves,  which  burst  and   release  their  own  protein  when  they  enter  the  acidic  abomasum     Lipids  –  limited  in  the  ruminant  diet   •   The  small  amount  that  does  exist  in  ruminant  diet  is  converted  by   microbes  into  VFAs,  which  pass  across  the  rumen  wall  and  eventually  aid   in  Krebs  Cycle   NPN  (non-­‐protein  nitrogen)   17   •   Combines  with  carbon  and  is  converted  by  microbes   to  NH3     •   Microbes  use  NH3  in  reconstruction  of  amino  acids   à  protein   •   By  this  method  ruminants  are  able  to  glean  protein  from  non -­‐protein   sources   •   Excess  nitrogen  enters  the  nitrogen  pool  and  exits  the  body  in  urine     Summary  of  food’s  passage  through  a  ruminant   Rumination:  prehension  à  mastication  à  deglutition  à  bolus  formed  as   food  passes  between  rumen  and  reticulum  (esophageal-­‐reticulo-­‐rumen   orifice  exists  at  this  point)  à  regurgitationà  re-­‐mastication  à  deglutition   à  repeat   Digestion:  Rumen  à  reticulo-­‐rumen  orifice  à  reticulum  à  reticulo-­‐rumen-­‐ omasal  orifice  à  omasum  à  omasal-­‐abomasal  orifice  à  abomasum  à   pyloric  abomasum  à  duodenum  à  jejunum  à  ileum  à  cecum  à   ascending  coil  of  large  intestine  à  descending  coil  of  large  intestine  à  ileo-­‐ colonic-­‐cecal  junction  à  rectum  à  anus     **A  ruminant’s  GI  tract  would  be  the  same  as  a  monogastric’s  if  the  rumen,   reticulum,  and  omasum  were  replaced  with  the  cardiac  region  of  the   stomach**                   18   19     Embryology   Purpose  of  the  egg:  to  protect  and  nourish  the  embryo   Embryos  incubate  for  21  days  (remember:  incubation,  not  gestation)   Protection  –  the  shell   •   Made  of  calcium;  formed  in  the  uterus   •   Arch  shape  –  difficult  to  break  from  outside,  easy  from  inside   •   First  line  of  defense  against  microbes  –  however,  they  can  still  enter   through  the  pores   •   Inner  and  outer  shell  membrane   o   Fused  together;  formed  in  isthmus   o   Made  of  protein   o   Second  line  of  defense  against  microbes   •   Air  cell  –  only  place  inner  and  outer  membrane  aren’t  fused   o   At  wide  end  of  the  egg   o   Gets  larger  as  incubation  progresses   o   Embryo  breaks  into  it  and  starts  to  breath  air,  then  continues  to   break  through  cell  when  hatching   20       •   Cuticle  –  light  outer  protein  layer  that  dries  quickly  after  the  cell  is  laid   Nourishment  –  the  yolk   •   Was  originally  a  follicle  in  the  ovary   •   Majority  of  composition:  nutrients  for  the  embryo   •   Albumen  –  egg  white  –  composed  of  protein  and  water   o   Thick  albumen:  from  magnum   o   Thin  albumen:  from  uterus     •   Chalazae  –  on  either  pole  of  yolk  –  spun-­‐out  protein  fibers  from  thick   albumen,  formed  when  yolk  twists   21     •   Vitelline  membrane  –  thin  membrane  that  surrounds  the  yolk,  is  inside   the  yolk  sac   •   Germinal  disc  –  where  embryo  develops  if  fertilized   22   o   Blastoderm  –  fertile  disc  –  looks  like  a  donut  with  a  dark  middle     o   Blastodisc  –  infertile  disc  –  indescript  white  spot   •   Dark/light  yolk  layers  –  daytime/nighttime  –  hen  eats  during  the  day  and   the  nutrients  give  pigmentation  to  the  yolk   •   Latebra  –  tunnel  created  from  germinal  disc  to  center  of  yolk  –  unsure  of   function   3  extra-­‐embryonic  membranes   •   Amnion  –  very  thin  fluid-­‐containing  membrane  surrounding  embryo   o   Protects  embryo  by  absorbing  shock   o   Not  as  important  for  human  embryos  –  only  needed  before   implantation  of  egg  cell   o   Gets  tighter  around  embryo  as  incubation  progresses   23       •   Yolk  sac  –  enables  embryo  to  absorb  nutrients  from  the  yolk   o   Meckel’s  diverticulum  –  remnant  of  yolk  sac  attachment   o   Retains  shape  and  size  as  incubation  progresses     •   Chorio-­‐allantois  –  lines  the  shell     o   Enables  embryo  to  breathe  –  oxygen/carbon  dioxide  exchange     §   Gases  travel  through  pore  à  chorio-­‐allantois  à  blood  à   embryo   o   Store  waste  and  absorb  calcium   o   Spreads  over  entire  inside  of  shell  as  incubation  progresses   24       Hatch  position:  assumed  at  18  days   •   Correct:  head  toward  air  sac  (wide  end  of  egg),  head  under  right  wing   25       Shell/yolk  layers  from  outside  to  inside:   Cuticle  à  shell  à  outer  shell  membrane  à  inner  shell  membrane  à   chorio-­‐allantois  à  albumen  à  yolk  sac  à  yolk  à  amnion  à  amnionic   fluid  à  embryo     26   ß  5  days     27                                                                                                               28   CARDIOVASCULAR  SYSTEM   Physiology  of  the  heart  –  flow  of  blood   4  chambers  in  the  heart   •   2  pump  blood:  ventricles  –  left  and  right   o   Contract  at  the  same  time   o   One  is  very  thick,  one  very  weak   •   blood  goes  through  valves   •   2  return  blood:  atria  –  left  and  right  –  sit  on  top  of  ventricles     Flow  of  blood  through  the  heart  and  body   •   When  blood  moves  through  the  heart,  it’s  happening  all  at  the  same   time  –  constant  motion   •   For  the  purpose  of  notes,  we  are  starting  at  one  point  and  working  our   way  through   1.  Start:  left  ventricle  –  very  thick  –  bigger  pump  –  pumps  oxygenated  blood   to  the  body   2.  Oxygenated  blood  leaves  left  ventricle  through  aortic  semilunar  valve  –     •   semilunar:  looks  like  3  half  moons  into  aorta   3.  Oxygenated  blood  leaves  the  heart  through  the  aorta   •   Split  in  aorta:  large  diameter  split  to  the  right  (blood  to  body)  small   diameter  split  to  the  left  (blood  to  head)  –     4.  Blood  loses  oxygen  when  it  reaches  the  body  tissues   5.  Deoxygenated  blood  returns  to  the  right  atrium  through  the  two  vena   cava  (veins)  –  cranial  (from  the  head)  and  caudal  (from  the  body)   6.  Deoxygenated  blood  leaves  right  atrium  through  the  right  atrioventricular   valve  into  the  right  ventricle   29   7.  Right  ventricle  contracts,  deoxygenated  blood  goes  through   pulmonary   semilunar  valve  into  pulmonary  artery     8.  Pulmonary  artery  has  two  major  branches,  one  for  each  lung   •   This  is  the  only  time  an  artery  carries  deoxygenated  blood     9.  Blood  picks  up  oxygen  in  the  lungs   10.  Oxygenated  blood  returns  to  left  atrium  through  pulmonary  veins     •   This  is  the  only  time  when  veins  carry  oxygenated  blood     11.  Oxygenated  blood  returns  to  left  ventricle  through  left  atrioventricular   valve       Cardiac  cycle   Contractile  state  of  ventricles  or  atria  and  of  the  valves   –  typical  heart   sounds  (lub  dub)     •   Diastole  –  bottom  number,  relaxation   •   Systole  –  top  number,  contraction,  ventricle  contraction  mainly   o   Atria  do  contract  but  not  nearly  as  much   •   Happening  at  same  time  on  left  and  right  sides   •   Atrioventricular  valves  are  open  when  blood  is  flowing  into  the  ventric le,   semilunar  valve  is  closed   •   Loud  sounds  created  when  valves  close   1.  Isometric  relaxation:  atrioventricular  valves  closed,  semilunar  valves   closed,  diastole  in  ventricles  and  atria   2.  Rapid  filling  of  left  atrium:  diastole  in  ventricles  and  atria,  AV  valves  open,   SL  valves  closed  –  3  heart  sound   3.  Diastasis:  diastole  in  ventricles  and  atria,  AV  valves  open,  SL  valves  closed   30   4.  Atrial  systole  (emptying  of  atria):  diastole  in  ventricles  (blood  flows  into   ventricles),  systole  in  atria,  AV  valves  open,  SL  valves  closed  –  4  heart   sound   5.  Isometric  contraction  (ventricles  contract,  pushing  blood  out):  systole  in   ventricles,  diastole  in  atria,  AV  valves  closed  to  prevent  backflow,  SL  valves   open  and  blood  exits  to  aorta/pulmonary  arteries–  1  heart  sound   6.  Ejection  part  one  (blood  flows  out  of  ventricles)  –  ventricles  systole,  atria   diastole,  AV  valves  closed,  SL  valves  open   7.  Ejection  part  two  –  ventricles  systole,  atria  diastole,  AV  valves  closed,  SL   valves  open     nd 8.  2  heart  sound:  pressure  from  backflow  of  blood  sh uts  the  semilunar   valves   8.  Repeat  cycle     Orientation  of  the  heart   Surface  vasculature  –  heart  needs  its  own  blood  supply  for  oxygen  to  keep  it   pumping   •   Left/right  coronary  artery  –  sit  in  AV  groove  –  branch  out,  branches   service  the  heart  itself   o   Heart  attack  –  clot/plaque  blocks  an  artery     o   Bypass  surgery  –  take  vein  from  leg  and  bypass  the  blocked  vein   •   2  branches  of  coronary  artery  –  left  and  right  (left  includes  apex  of  heart)   Orientation:  surface  anatomy  –  ventricles:  tough  is  left,  soft  is  right   Aorta  vs  coronary  arteries   •   Aorta  is  in  back  of  the  heart  –  always  very  stiff  –  if  facing  the  aorta  the   left  ventricle/atrium  is  on  the  right  side   •   Coronary  artery  is  in  front  of  the  heart  –  goes  through  to  the  right  side  of   the  heart   31         Vocabulary   Pericardium  –  sac  surrounding  the  heart;  contains  pericardial  fluid  to   prevent  friction  during  the  heartbeat   Epicardium  –  very  thin  epithelial  layer  on  outside  of  heart   Apex  –  most  caudal  point  of  the  heart   •   Placed  close  to  the  sternum   •   Lies  to  the  left  of  the  median  plane   •   The  long  axis  that  joins  the  center  of  the  base  to  the  apex  slopes   caudoventrally   Left  ventricle  –  a  bottom  section  of  the  heart   •   Much  thicker  walls  (myocardia)  than  right  ventricle     •   Circular,  forms  the  entire  apex  of  the  heart   •   Sends  out  oxygenated  blood  through  the  medially  located  aorta   Right  ventricle  –  a  bottom  section  of  the  heart     •   Thicker  walls  than  atria,  thinner  walls  than  left  ventricle   •   Wrapped  around  the  right  and  cranial  aspects  of  the  left  ventricle   •   Receives  oxygenated  blood     •   Auricle  vs  atrium:  auricle  is  structure  on  the  outside  of  the  atrium,   flowerlike  appearance,  atrium  is  open  space  on  the  inside  –  not   interchangeable  terms!     Left  atrium  (auricle)  –  a  top  section  of  the  heart   •   To  the  left  of  the  medial  plane   •   Thin  walls   32   •   Receives  deoxygenated  blood  from  the  veins  including  vena  cava     Right  atrium  (auricle)  –  a  top  section  of  the  heart   •   Mostly  to  the  right  of  the  medial  plane   •   Thin  walls   •   Receives  deoxygenated  blood   •   Greater  part  forms  a  chamber  into  which  the  main  systemic  veins   discharge  –  including  the  caudal  vena  cava,  which  enters  the  caudodorsal   part  of  the  right  atrium   Aorta  –  largest  artery  in  the  body   •   Extends  from  left  ventricle  and  branches  into  two  coronary  arteries   Cranial  vena  cava  –  large  vein  that  carries  blood  from  the  head  and  upper   body;  Attaches  to  right  atrium;  carries  deoxygenated  blood   Caudal  vena  cava  –  large  vein  that  carries  blood  from  the  lower  body;   attaches  to  right  atrium;  carries  deoxygenated  blood   Pulmonary  arteries  –  carry  blood  from  the  right  ventricle  to  the  lungs  for   oxygenation   Pulmonary  veins  –  receive  oxygenated  blood  from  the  lungs  and  drain  into   the  left  atrium     •   Open  variously  into  the  roof  of  the  left  atrium;  do  not  have  valves     Paraconal  interventricular  groove  –  shallow  groove  that  descends  cranially   toward  the  apex  and  externally  divides  the  ventricles     Paraconal  artery  –  one  of  three  branches  of  the  coronary  artery     •   Crosses  ventrally  across  the  heart  in  the  paraconal  interventricular   groove   •   Branches  from  this  artery  supply  the  left  and  right  ventricles   Subsinuosal  interventricular  cavity  –  shallow  groove  that  descends  caudally   toward  the  apex  and  externally  divides  the  ventricles   33   Subsinuosal  artery  –  one  of  three  branches  of  the  coronary  artery;  lies  in  the   subsinuosal  interventricular  cavity   Atrioventricular  groove  –  groove  along  the  external  surface  of  the  heart  that   divides  the  right  atrium  and  right  ventricle   •   Contains  a  branch  of  the  right  coronary  artery     Right  coronary  artery  –  branches  from  the  aorta   •   Carries  oxygenated  blood   •   Branches  further  into  arteries  along  the  atrial  and  ventricular  walls     Left  atrioventricular  valve  –  bicuspid/mitral  valve   •   Composed  of  2  flaps  (cusps)  but  is  otherwise  comparable  to  that  of  the   right  side   Right  atrioventricular  valve  –  tricuspid  valve   •   Composed  of  3  flaps  (cusps)  that  attach  to  a  fibrous   ring  that  encircles   the  opening   Chordae  tendinae  –  fibrous  strands  that  join  the  cusps  of  the  valves   •   Generally  arranged  so  that  they  connect  each  cusp  to  two  muscles  and   each  muscle  to  two  cusps     •   This  prevents  cusps  from  turning  inside  out  into  the  atrium   during   ventricular  contraction     Papillary  muscle  –  located  in  the  ventricles;  attach  to  the  cusps  of  the   atrioventricular  valves  via  the  chordae  tendinae   Pulmonary  semilunar  valve  –  covers  the  opening  of  the  pulmonary  trunk     •   Situated  on  the  left  side  of  the  heart   •   Closed  by  backflow  of  blood  during  ventricular  relaxation  (diastole)   •   Composed  of  3  semilunar  cusps  that  fit  together  tightly  when  the  valve  is   closed     Aortic  semilunar  valve  –  generally  resembles  the  pulmonary  valve   34   •   Centrally  positioned   Pectinate  muscle  –  parallel  ridges  in  the  walls  of  the  atria   •   Resemble  the  teeth  of  a  comb     Moderator  band  –  muscular  band  of  tissue  found  in  the  right  ventricle     •   Vary  in  size  among  individuals     •   Provides  support  in  right  ventricle,  necessary  because  the  walls  are  so   weak  –  prevent  walls  from  exploding  during  contraction   Myocardium  –  thick  middle  layer  of  the  outer  wall  of  the  heart;  composed  of   cardiac  muscle   Endocardium  –  covers  the  internal  side  of  the  myocardium   •   A  thin  smooth-­‐surfaced  layer  continuous  with  the  lining  of  the  blood   vessels     Interventricular  septum  –  short  wall  separating  the  ventricles  from  each   other     35   36  


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