Anatomical studies on prenatal development of brain in Gaddi sheep

Abstract

The present study was conducted on the brain of 54 Gaddi sheep fetuses to study gross anatomy, histogenesis, organogenesis and histochemistry at different stages of gestation. The prenatal brain samples were divided into four groups viz. Group-I (30-60 days), Group-II (61-90 days), Group-III (91-120 days) and Group-IV (121 days- till full term) based on their age (days) obtained by the formula, Y = 2.74X + 30.15, where Y is the age of embryos in days and X is the CRL in centimeters. A significant increase was recorded in the length of the head, width of head, length of cranium, length of face, inter auricular distance and transverse distance between lateral and medial canthi among all the groups with the advancement of the gestational period. Fifty percent of the brain weight and body weight the fetus had at the full term was attained at approximately 17 weeks of gestation. A significant (plt0.05) increase in weight of cerebrum was noticed from Group II to Group III of gestation. A significant increase in the width and thickness of cerebrum was noticeable from Group II to Group III and further to Group IV. A significant increase was observed in the weight of the cerebellum from Group I to Group III and further to Group IV. The length, width and height of the brainstem exhibited a significant increase with the advancement of gestational age. The surface of cerebral hemisphere was observed to be lissencephalic at 47 days of gestation. The longitudinal fissure and transverse fissure were visible at 47 days of gestation. The external granular layer in cerebellum was unique to the fetal cerebellum of Group I. The cerebellum was present as a dumbbell shaped structure having centrally located cerebellar vermis and two laterally located cerebellar hemispheres as early as 67 days of gestation. Corpora quadrigemina consisting of rostral and caudal colliculi were observed on the dorso-caudal surface of the brain at 67 days of gestation in Gaddi sheep fetuses. Purkinje cells were organized as a distinct layer in developing