Age-related anatomical variation and morphometric studies on the optic tectum in post-hatch broiler chicken

In this investigation the morphological and morphometrical features of the optic tectum in post-hatch broiler chicken were studied macroscopically and microscopically. The present study was conducted on 70 day old broiler chicks which were reared up to 42 days. The whole experimental period of study was divided into seven groups (from group I to VII) at weekly interval (days 0, 7, 14, 21, 28, 35 and 42). The optic lobes were paired and spherical to oval eminences located on the ventro-lateral part of the midbrain in broiler chicken. There was significant increase in length and width of the optic lobes with the advancement of age. Histological analysis of optic tectum shows six basic layers from the external surface to internal one towards the optic ventricle. Different layers of optic tectum were identified as stratum opticum, stratum griseum superficial, stratum griseum central, stratum album central, stratum griseum periventriculare and stratum fibrosum periventriculare with several types of neurons. Among all six layers of the optic tectum the stratum griseum superficial layer showed very high degree of secondry differentiation and evolved into nine sub- layers in all age groups of broiler chickens. Three main cell types had been identified that is, small to medium sized stellate shaped neuron, pyramidal neuron and fusiform neuron, beside these multipolar neuron were also evident. The thickness of all layers of optic tectum significantly increases with the advancement of age of the birds. The optic ventricle was lined with a layer of cuboidal ependymal cells.