Morphometric study of the neurons in human hypoglossal nerve nucleus during early gestation

Abstract

Hypoglossal nerve, XII cranial nerve is responsible for the motor innervation of the tongue muscles, which assists in various motor activities such as chewing, swallowing, vocalization. Thus, weakness of this nerve will lead to weakness and deviation of the tongue to one side. Clinically besides these functions it is also responsible for the most important function such as modulation of respiration and drinking behavior. Thus, a detailed study about the cell dynamics, which involves the development of neurons in the hypoglossal nerve nucleus becomes essential. 12 foetuses [Gestational age 10 – 24 weeks] were included in the study. They were divided into 4 groups based on their gestational age and CRL measurements. Hypoglossal nucleus extends throughout the length of medulla oblongata in the para-median plane. Tissues were collected from hind brain section and section of medulla. The tissues will be processed by routine histological procedure were stained with hematoxylin & eosin and also with Holmer’s Silver nitrate to study the histological details. Morphometric study covered the cell dimensions and volumes of hypoglossal neurons and its nucleus. From these data, coefficients were drawn to identify the proportion of growth between cell and nuclear volume. Morphometric analysis of hypoglossal nerve neurons in human from 10^th to 24^th gestational week concludes that the primitive migratory cells seen in the initial period and later it will become round neuroblast. In the initial 16 weeks nucleus occupied the entire volume of the cell.

Keywords: Hypoglossal nerve nucleus, Deglutition, Mastication, Morphometry, Histogenesis