甲状腺的解剖.ppt

Thyroid Anatomy 13# Thyroid Anatomy 13/13 Thyroid Anatomy 12/13 Most of the anterolateral surface of the neck is covered by the thin platysma muscles, remnants of the panniculus carnosus of mammals (watch a dog shake its coat). This muscle is at the level of the superficial fascia and its underside provides an excellent plane of dissection exposing the deep fascia of the neck. Because of the inverted V-shaped gap in this layer anteriorly, dissection of flaps in a collar incision should begin laterally. Thyroid Anatomy 11/13 The sternocleidomastoid muscles flank the straps and cover the internal jugulars and carotid sheaths. They are enclosed in an encircling girdle of deep cervical fascia called the investing layer. This layer continues posteriorly to enclose the trapezius muscles (see neck clinical folio). The external jugular veins descend across the posterior portions of the sternocleidomastoids and anterior jugular veins descend along the straps anteriorly. Thyroid Anatomy 10/13 The thyroid is covered by the sternohyoid and sternothyroid (strap) muscles. These are enclosed in an intermediate layer of deep cervical fascia (see Thryoid Anatomy: 1) with the sternohyoids being apposed in the midline and the underlying sternothyroids being slightly more lateral. When mobilizing the straps it is important to stay in the plane deep to both muscles. The omohyoid muscles ascend diagonally across the upper part of the straps and are automatically mobilized with those muscles. Thyroid Anatomy 9/13 Venous drainage of the thyroid runs with the superior laryngeal arteries above, passes laterally (middle thyroid veins) directly into the internal jugular veins, and drains inferiorly into the brachiocephalic veins. The dominant lymphatic drainage accompanies the vessels within the loose areolar carotid sheaths. The veins form a plexus on the surface of the gland within the areolar thyroid (visceral) fascia. Remaining external to this capsule provides a relatively bloodless