TY  - CHAP
M1  - Book, Section
TI  - Chapter 526. The Thyroid
A1  - Fisher, Delbert A.
A2  - Rudolph, Colin D.
A2  - Rudolph, Abraham M.
A2  - Lister, George E.
A2  - First, Lewis R.
A2  - Gershon, Anne A.
PY  - 2011
T2  - Rudolph's Pediatrics, 22e
AB  - The  thyroid  gland  develops  as  an  endodermal  diverticular  outpouching  from  the  floor  of  the  pharynx  during  the  third  week  of  gestation,  at  a  site  that  persists  as  the  foramen  cecum  at  the  base  of  the  tongue  in  adults.  The  medial  thyroid  anlage  descends  in  the  neck  anterior  to  structures  that  form  the  hyoid  bone  and  larynx.  During  its  descent,  the  anlage  remains  connected  to  the  foramen  cecum  via  an  epithelial-lined  tube  known  as  the  thyroglossal  duct.  The  epithelial  cells  making  up  the  anlage  give  rise  to  the  thyroid  follicular  cells.  Paired  lateral  anlages  originate  from  the  fourth  branchial  pouch  and  fuse  with  the  median  anlage  at  approximately  the  fifth  week  of  gestation.  The  lateral  anlages  are  neuroectodermal  in  origin  (ultimobranchial  bodies)  and  provide  the  calcitonin-producing  parafollicular  or  C  cells,  which  come  to  lie  in  the  superoposterior  region  of  the  gland.  Thyroid  follicles  are  initially  apparent  by  8  weeks,  and  colloid  formation  begins  by  the  11th  week  of  gestation.  The  growth  and  descent  of  the  thyroid  into  the  neck  requires  the  coordinated  action  of  multiple  transcription  factors.  TTF-1,  TTF-2,  and  PAX-8  are  expressed  just  before  and  after  the  appearance  of  the  thyroid  diverticulum.  Targeted  disruption  of  the  TTF-1  gene  in  mice  results  in  complete  absence  of  the  thyroid  gland,  whereas  disruption  of  PAX-8  results  in  a  small  thyroid  that  lacks  follicles.  
SN  - 
PB  - The McGraw-Hill Companies
CY  - New York, NY
Y2  - 2024/04/18
UR  - accesspediatrics.mhmedical.com/content.aspx?aid=7053164
ER  -