RT Book, Section
A1 Mescher, Anthony L.
SR Print(0)
ID 1184201100
T1 Organs Associated with the Digestive Tract
T2 Junqueira's Basic Histology Text and Atlas, 16e
YR 2021
FD 2021
PB McGraw Hill
PP New York, NY
SN 9781260462982
LK accessmedicine.mhmedical.com/content.aspx?aid=1184201100
RD 2024/04/23
AB Organs  Associated  with  the  Digestive  Tract  SUMMARY  OF  KEY  POINTSSalivary  GlandsSalivary  glands  have  secretory  units  of  either  protein-secreting  serous  cells,  usually  organized  in  round  or  oval  acini,  or  of  mucin-secreting  mucous  cells  in  elongated  tubules.Parotid  glands  have  only  serous  acini;  sublingual  glands  are  mixed  but  have  primarily  mucous  tubules,  some  with  serous  demilunes;  submandibular  glands  are  also  mixed  but  have  mainly  serous  acini.Salivary  secretory  units  are  drained  by  simple  cuboidal  intercalated  ducts,  which  merge  as  simple  columnar  striated  ducts,  which  merge  further  as  the  larger  interlobular  or  excretory  ducts.Cells  of  striated  ducts  have  mitochondria-lined,  basolateral  membrane  folds  specialized  for  electrolyte  reabsorption  from  the  secretion;  excretory  ducts  are  unusual  in  having  stratified  cuboidal  or  columnar  cells.PancreasPancreatic  islets  of  endocrine  cells  are  embedded  in  exocrine  serous  acinar  tissue,  which  comprises  most  of  the  pancreas  and  in  which  the  cells  secrete  hydrolytic  digestive  enzymes  for  delivery  to  the  duodenum.Each  pancreatic  acinar  cell  is  pyramidal,  with  secretory  (zymogen)  granules  in  the  narrow  apical  end  and  Golgi  complexes,  much  rough  ER,  and  a  large  nucleus  at  the  basal  end.Intercalated  ducts  draining  pancreatic  acini,  including  their  initial  centroacinar  cells  that  insert  into  the  acinar  lumen,  secrete  bicarbonate  ions  (HCO3−)  to  neutralize  chyme  entering  the  duodenum  from  the  stomach.LiverLiver  hepatocytes  are  large  epithelial  cells  with  large  central  nuclei  (polyploid  and  often  binucleated),  much  smooth  and  rough  ER,  and  many  small  Golgi  complexes.Hepatocytes  have  many  functions,  including  endocrine  (plasma  protein  secretion),  exocrine  (bile  secretion),  glucose  storage  (glycogen  granules),  and  detoxification  (using  SER  and  peroxisomes).In  the  liver,  hepatocytes  are  organized  into  irregular  plates  to  form  polygonal  hepatic  lobules  in  which  the  hepatocyte  plates  radiate  toward  a  small  central  vein.Each  hepatic  lobule  is  surrounded  by  sparse  connective  tissue  that  is  more  abundant  in  the  portal  areas  at  the  corners.Portal  areas  or  tracts  contain  a  small  lymphatic  and  the  portal  triad:  a  portal  venule  branch  from  the  portal  vein,  a  hepatic  arteriole  branch  of  the  hepatic  artery,  and  a  bile  ductule  branch  of  the  biliary  tree.In  the  lobules  the  portal  venule  and  hepatic  arteriole  both  branch  into  irregular  sinusoids  between  the  hepatic  plates  where  the  nutrient-rich  and  O2-rich  blood  mixes,  flows  past  hepatocytes,  and  drains  to  the  central  vein.The  endothelium  of  the  hepatic  sinusoids  is  discontinuous  and  fenestrated;  between  it  and  the  hepatocytes  is  the  perisinusoidal  space  (of  Disse)  where  exchange  occurs  between  the  hepatocytes  and  blood  plasma.The  sinusoidal  endothelium  includes  many  specialized  stellate  macrophages  or  Kupffer  cells,  which  recognize  and  remove  effete  erythrocytes,  releasing  iron  and  bilirubin  for  uptake  by  hepatocytes.Also  present  in  the  perisinusoidal  spaces  are  hepatic  stellate  cells  (or  Ito  cells)  containing  many  small  lipid  droplets  for  storage  of  vitamin  A  and  other  fat-soluble  vitamins.Between  adherent  hepatocytes  in  the  hepatic  plates  are  grooves  called  bile  canaliculi,  sealed  by  tight  junctions,  into  which  hepatocytes  secrete  water  and  bile  components,  including  bilirubin  and  bile  acids.In  each  hepatic  lobule,  all  bile  canaliculi  converge  on  the  bile  canals  (of  Hering),  which  join  the  bile  ductules  in  the  portal  areas  and  eventually  all  merge  to  form  the  left  and  right  hepatic  ducts.Biliary  Tract  and  GallbladderAll  ...