This model shows a part of placental units to explain these observations.,every substance is produced from different places,some units start production earlier than other units ,according to placental maturity with progress of pregnancy,This explains the

1
THE PLACENTAL FACTORY MODEL

• This model shows a part of placental units to
  explain these observations.,every substance is
  produced from different places,some units start
  production earlier than other units ,according to
  placental maturity with progress of
  pregnancy,This explains the maximum values
  observed at or near term, which means all the
  units are working..If we imagine that a defect
  well occur at any time or at any place in the
  factory the result is pregnancy loss.The
  following is explanation of the factory model
• 1-cholesterol,2-DHEA,3- oxytocin ,
  4-progesterone,5-estrogen,
• 6-CRH,7-ACTH,8-oxytocin uterine
  antagonist,9-oxytocin breast antagonist,10-store
  room.11-hypothalamus and pituitary glands,
• 12-peripheral tissues,13-uterus and 14-breast,
  the rooms indicate place of production and site
  of action of others,the lines indicate the
  transport mechanisms. All different endocrine
  methods aplly for the placental products as can
  be seen in the fig.2

2
Fig(2) The placental factory model
11-HTP
12-per.tissues
1-chol
13 uterus
8-OUA
2-DHEA
3-oxytocin
9-OBA
14-breast
6 CRH
5-estr
4-prog
8-OUA
ACTH
6 CRH
7 ACTH
5-estr
8-OUA
ACTH
9-OBA
8-OUA
9-OBA
5-estr
4-prog
6-CRH
9-OBA
ACTH
6 CRH
8-OUA
ACTH
10-store
6 CRH
3
Fig-1- the placental feedback mechanism.this is
positive in normal pregnancy till
maturity.Conception results in increased
sex-steroid hormones,which stimulate the
hypothalamus and posterior pituitary glands to
synthesize and release oxytocin.This hormone
interacts with its receptor in uterus,breast and
placenta. before maturity it acts mainly on the
placenta to produce placental CRH.This hormone is
known to stimulate placental ACTH production.This
stimulates the synthesis and release of oxytocin
antagonists by the placental and peripheral
tissues.these antagonists interact with oxytocin
receptors in the uterus and breast till maturity
and delivery in normal gestations.
4
Fig-1-Placental Feedback Mechanism
Conception
Estrogenprogesterone
Hypothalamus post pituitary
Per ,tissues
OBA
breast
Oxytocin
CRH
Placenta
ACTH
Uterus
OUA