Chandrasekhara Rao, T.S(MAJOR)Pramod Kumar, DRaghavender, K.B.PGirish Kumar, VSANTHI LAKSHMI, M2018-09-272018-09-272006-10http://krishikosh.egranth.ac.in/handle/1/5810074279THESESABSTRACT : The present work was undertaken on 509 embryos and fetuses of Buffalo belonging to 112 age groups starting from 26 d to 310 d to study the prenatal development of facial and cranial bones and also the relationship of the developing skull with other structures of the head at different stages. Developmentally the bones of the buffalo skull were divisible into four groups i.e. Cartilaginous neurocranium, Membranous neurocranium, Membranous viscerocranium and Cartilaginous viscerocranium. The bones of the chondrocranium consisted of lower part of squamous occipital, exoccipital, basioccipital, petrous temporal, tympanic bulla, basisphenoid, presphenoid, ethmoid and turbinates. The frontal, parietal, interparietal and upper part of squamous occipital formed the desmocranium. The premaxilla, maxilla, palatine, pterygoid except its hamulus, malar, squamous temporal, tympanic ring, lacrimal, nasal, vomer and mandible except its condyle constituted membranous viscerocranium. The Meckel’s cartilage and its derivatives malleus and incus, mandibular condyle, Reichert’s cartilage and its derivatives including stapes, tympanohyoid, hyoid, styloid process of temporal and hamulus pterygoideus formed the cartilaginous viscerocranium. The chondrocranium was divisible into basal plate, prechordal part and paired otic and nasal capsules around sensory epithelia. The basal plate cartilage formed the basioccipital, exoccipital and lower part of the squamous occipital. The otic capsule formed petrous temporal bone and tympanic bulla. The prechordal part formed basisphenoid caudally and presphenoid cranially. The nasal capsule formed the ethmoid, turbinates, nasal septum and nasal cartilages. The bones of the cartilaginous neurocranium and cartilaginous viscerocranium were formed by endochondral ossification while intramembranous bone formation was seen in the bones of the membranous neurocranium and membranous viscerocranium. The bones of floor of the cranium except basioccipital were ossified from multiple centers. Most of the facial bones except mandible, vomer and hyoid as well as calvarial bones were ossified from single centers. Most of the chondrocranium was cartilaginous at 45 d. The ossification of skull first appeared in mandible, maxilla and malar at 45 d. Early ossification of lacrimal, squamous temporal and tympanic ring was evident at 49 d. The ossification of palatine was first observed at 53 d while premaxilla and vomer showed ossification at 56 d. The ossification of nasal bone was observed at 61 d. The ossification of desmocranium first appeared in frontal at 49 d. Parietal and interparietal bones showed ossification at 60 d and 64 d respectively. The ossification of chondrocranium first appeared in occipital and sphenoid at 62 d. The last bone of the skull to ossify was the dorsal turbinate. The maxillary sinus appeared first at 92 d among the sinuses of the skull. Five fontanelles in total i.e. unpaired anterior fontanelle, paired mastoid and sphenoidal fontanelles were observed. Wormian bones were observed at frontonasal junction in a few cases. The craniofacial index of skulls of 98 d to 310 d was ranged from 4.3: 1.8 to 13.7:13.5. The otic and optic vesicles were evident at 26 d. The enamel organs of premolars of upper jaw and incisors and premolars of lower jaw were evident at 62 d. The formation of choroid plexuses of ventricles was evident at 43 d while development of pituitary was observed at 41 d.ennullThesis