Prenatal study on the development of liver of Gaddi sheep

Abstract

Gross morphological, histological and histochemical studies were done on prenatal liver of Gaddi sheep. Total sixty samples were used for gross morphological study and from this twenty four samples were used for histological and histochemical studies. The prenatal liver samples were divided into four groups viz. group-I (1-60 days), group-II (61-90 days) and group-III (91- 120 days) and group-IV (121- full term) having 15 embryos/foeti in each group for gross morphological study and 6 samples in each group for histological and histochemical study. The prenatal liver consisted of two surfaces (visceral and parietal surface), two extremities (cranial and caudal) and two borders (lateral and medial border). Till full term, the liver was not completely oriented towards the right side of abdominal cavity. The mean body weight of sheep foetii increased significantly from group-I to group-IV. Liver accounted 9.07%, 8.45%, 6.15% and 5.49% of the total body weight in group-I, II, III and IV respectively. All biometrical parameters showed an increasing trend with the advancement of age except relative weight of liver and shape index. The right lobe of liver was largest followed by left and caudate lobe. First appearance of portal triad was observed at 76 days of gestation. Right lobe had maximum capsular thickness. Varying concentration of sudanophillic lipids and mucopolysaccharides were observed in different components of liver. In haemopoietic cells and hepatocytes the neutral mucopolysacchariders were present. The presence of bile pigments and glycogen was visible from 57 days of gestation. Iron particles were visisble from 97 days of gestation and bile canaliculi at 53 days of gestation. The concentration (ppm) of Mn, Co, iron, Se and Mo increased with the progression of gestation age. The Zn concentration was maximum between 61-90 days of gestation.While, the concentration of Cu and Ca was maximum between 1-60 days of gestation. Electron microcopy revealed that chromatin material became concentrated and there was decrease in number of mitochondria in post natal hepatocytes than the prenatal ones. The hepatocytes were clearly binucleated. Gall bladder appeared at 46 days of gestation. At 60 days of gestation the tunica mucosa, tunica submucosa, tunica muscularis and tunica serosa layers were clearly distinguishable. The thickness of tunica muscularis, tunica serosa and luminal diameter of gall bladder increased significantly with the advancement of gestational age. While, the thickness of tunica mucosa and submucosa was maximum in group-III. The presence of bile in gall bladder was observed from 53 days of gestation. Chenodeoxycholic acid, cholic acid and deoxycholic acid were three main bile acids identified in bile. newline