Physiological study of the fibre component of eln innervating thyroid gland

Many studies in anatomical literatures reported that the external laryngeal nerve (ELN), one of the superior laryngeal branches of the superior laryngeal nerve (SLN) is not a purely motor nerve as was thought earlier. Some anatomists have established that the ELN innervates the thyroid gland through a branch. Sun and Chang, 1991 reported thatthe thyroid gland receives branches from the ELN which may be sympathetic in nature. In a recent study, Vijesh and Sun, 2012 proved that ELN is a mixed nerve and prove the thyroid glandular branch is postganglionic sympathetic in nature, which may play an important function in vasomotor and secretory functions of thyroid gland. This present study aims to understand the function of the branch of ELN innervating the thyroid gland. This study is unique in itself since no such study has been reported till now .Surgical procedures have been conducted by making a cut between the thyroid gland and the branch of the ELN that innervates the upper pole of the thyroid gland in dogs. Three experimental groups A, B and C were formed. Every group had a dog used as sham. Thyroid glands were collected from the dogs after 4, 6 and 8 days post surgeries. Blood samples were collected both before and after surgery from all groups. Some thyroid glands showed the presence of colloid goiter with single cuboidal or flattened epithelial cells surrounding the follicles. Follicles of variable sizes and of colloid material in the interfollicullar spaces were seen in group A. Group B and C showed similar kind of follicles along with different kinds of colloids. Group B and C showed significant increase in the TSH and T4. This result suggests that the branch of ELN innervating the thyroid gland may be sympathetic nature.