الفهرس 
EMBRYOLOGY AND ANATOMYOnly 14 pages are availabe for public view
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Abstract
Delayed passage of meconium is a considerable event in premature infants. Failure of a full-term newborn to pass meconium within the first 24 hours may be an early sign of intestinal obstruction. The intestinal obstruction, whether mechanical or functional, in premature infants was investigated by many studies; it was hypothesized that the functional intestinal obstruction was due to the immaturity of neuromuscular components of the internal anal sphincter.
This study was designated to illustrate the histological and immunohistochemical developmental changes of the anal canal with special reference to the internal anal sphincter of guinea pigs from 3rd trimester of gestation to full maturity.
Mating four adult male guinea pigs and ten adult females was done, and the pregnant females were divided into 2 groups. One group (three females) were sacrificed at the 3rd trimester, the rest of females (seven females) continued their full gestational period.
The offspring (forty animals) were grouped as follows:
Group I: 10 embryos were sacrificed at
Group II: 10 animals were sacrificed at the 1st day of life.
the 3rd trimester
Group III: 10 animals were sacrificed at 4 weeks of age
Group IV: 10 animals were sacrificed at 16 weeks of age (adult group).