Isthmus of the thyroid gland lies in front of the second, third and fouh tracheal rings. It is covered in front by skin and fascia, and by sternothyroid and sternohyoid muscles and by the anterior juglar veins. Upper end of each lobe of thyroid lies opposite C5 veebrae. The lower end of the lobe lies at the level of 5th or 6th tracheal ring corresponding to T1 veebrae.