The present study deals with the embryonic development of the early and the intermediate embryonic stages of Columba livia domestica inner ear or the membranous labyrinth (10,15,20,22,26,30,33,36 and 47 mm total body length). During the early development (10 mm stage), neuroepithelium of the ventral rhompencephalon evaginates laterally to form an ectoderm thickening, the otic placode. The latter invaginates forming the otocyst that subsequently gives all other components of the membranous labyrinth. The surrounding mesenchyme is the origin of cartilaginous capsule of the ear. The endolymphatic duct is the first appeared structure in 15 mm stage, followed by cochlear duct (in 22 mm stage) and finally the three semicircular ducts. The latter begin in 26 mm stage and end in 47 mm stage .The inner ear contains sensory organs; the macula of ( utriclus , sacculus) and the crista ampullaris ( of the three semicircular canals ) and the basilar papillae of the cochlear duct; not only for the sense of hearing but also for the equilibrium ,stability and balance. The sensory organs of the intermediate stages (36 and 47 mm stages) showed no differentiation to hair or supporting cells. In the intermediate stage (47 mm stage), the inner ear has undergone a considerable development in its structure. It consists of a dorsal vestibular part including two connecting sacs (utriculus and the sacculus) and three semicircular canals and ventral cochlear part (the cochlear duct).

Abstract:The present study investigates the effects of different doses of "trichloroethylene" TCE on the axial and appendicular skeleton of day 18 mice fetuses maternally treated with TCE. The experimental females (90 virgin females) were divided into three groups; the first one (G1) was the control that treated with the solvent only (corn oil), the second (G2) and the third (G3) treated groups with low (24 mg/kg) and high (240 mg/kg) doses of TCE, respectively. Oral administration of TCE to female mice once daily for a period of 21 days before mating and till 17 th day of pregnancy, caused a significant decrease in the body weight and body length of treated fetuses. Stereoscopic examination for the obtained 18 th day fetuses showed severe skeletal alterations included incomplete ossification for some bones of skull, vertebrae, fore and hind limbs and significant reduction in the length of most long bones of both limbs. These alterations indicated that TCE treatment induced growth retardation confirmed by great reduction in body weight and body length. The results suggest that TCE has teratogenic effects on maternally treated 18-day-old albino mice fetuses.