RT Book, Section
A1 Davé, Utpal P.
A1 Koury, Mark J.
A2 Kaushansky, Kenneth
A2 Lichtman, Marshall A.
A2 Prchal, Josef T.
A2 Levi, Marcel M.
A2 Press, Oliver W.
A2 Burns, Linda J.
A2 Caligiuri, Michael
SR Print(0)
ID 1135461624
T1 Structure of the Marrow and the Hematopoietic Microenvironment
T2 Williams Hematology, 9e
YR 2015
FD 2015
PB McGraw-Hill Education
PP New York, NY
SN 9780071833004
LK hemonc.mhmedical.com/content.aspx?aid=1135461624
RD 2024/04/20
AB SUMMARYThe  marrow,  located  in  the  medullary  cavity  of  bone,  is  the  site  of  hematopoiesis  in  humans.*  The  marrow  produces  approximately  6  billion  cells  per  kilogram  of  body  weight  per  day.  Hematopoietically  active  (red)  marrow  regresses  after  birth  until  late  adolescence,  after  which  it  is  focused  in  the  lower  skull,  vertebrae,  shoulder  and  pelvic  girdles,  ribs,  and  sternum.  Fat  cells  (yellow  marrow)  replace  hematopoietic  cells  in  the  bones  of  the  hands,  feet,  legs,  and  arms.  Fat  comprises  approximately  50  percent  of  red  marrow  in  the  adult.  Further  fatty  replacement  of  the  red  marrow  continues  slowly  with  aging,  but  hematopoiesis  can  be  expanded  when  demand  for  blood  cells  is  increased.The  marrow  stroma  consists  principally  of  a  network  of  sinuses  that  originate  at  the  endosteum  from  cortical  capillaries  and  terminate  in  collecting  vessels  that  enter  the  systemic  venous  circulation.  The  trilaminar  sinus  wall  is  composed  of  endothelial  cells;  a  thin  basement  membrane;  and  adventitial  reticular  cells  that  are  progenitors  of  chondrocytes,  osteoblasts  and  adipocytes.  Stem  cells  can  leave  and  reenter  marrow  as  part  of  their  normal  circulation.Hematopoiesis,  the  proliferation  and  differentiation  of  stem  cells  and  their  progeny  in  the  intersinus  spaces,  is  controlled  by  a  complex  array  of  stimulatory  and  inhibitory  cytokines,  cell–cell  contacts,  and  interactions  with  the  extracellular  matrix.  In  this  unique  environment,  lymphohematopoietic  stem  cells  differentiate  into  all  the  blood  cell  lineages.  Mature  cells  are  produced  and  released  to  maintain  steady-state  blood  cell  levels.  The  hematopoietic  system  also  can  respond  to  meet  increased  demands  for  additional  cells  as  a  result  of  blood  loss,  hemolysis,  inflammation,  immune  cytopenias,  and  other  causes.