Anatomy - Thyroid Gland

How many fascial compartments are there in the neck? (C7 level)

4 Pre-vertebral (deep) fascia Investing fascia Carotid sheaths Pre-tracheal fasica

How many parathyroid glands are there?

4 Superior and inferior parathyroid glands are located bilaterally

What are strap muscles?

4 muscles between the manubrium and the hyoid bone Their function is to pull the hyoid and some of the larynx inferiorly

What is the foramen caecum?

A pouch which pierces down through the tongue, attaches to the hyoid bone, and descends down again (its path shows how the thyroid gland descends through development)

What composes the skeleton of the larynx?

Hyoid bone Thyroid cartilage (superiorly) Cricoid cartilage (inferiorly)

What structures are located in the pre-tracheal fascia?

Oesophagus Trachea Thyroid gland Strap muscles Recurrent laryngeal nerves

What is the thyroid isthmus?

The central band (horizontal) that connects the two lateral lobes of the thyroid gland

What is the pyramidal lobe?

An anatomical variation Most commonly originates from the left lateral lobe It can attach superiorly to the thyroid cartilage, or even as high as the hyoid bone

Where are the carotid sheaths located in relation to the thyroid gland?

Anterolaterally

What is the embryology of the thyroid gland?

Begins at the midline of the junction between the anterior and posterior tongue - this is called the foramen caecum The gland migrates inferiorly whilst remaining attached to the thyro-glossal duct, and reaches final position in week 7 of development

What are carotid sheaths?

Bilateral tubes of deep fasica Attach superiorly to the base of the skull - around both the jugular foramen and the carotid canal

What do parathyroid glands look like on dissection?

Dark nodules on the lateral lobes of the thyroid gland

Sternothyroid muscle

Deep strap muscle From the sternum to the thyroid cartilage

Thryohyoid muscle

Deep strap muscle From the thyroid cartilage to the hyoid bone

What muscles are located within the superficial fascia of the neck?

Platysma muscles

What muscles are located in the pre-vertebral (deep) fascia?

Postural neck muscles Cervical vertebrae

Where do the recurrent branches of the vagus nerve arise?

Right subclavian artery Arch of the aorta

Sternohyoid muscle

Superficial strap muscle Between the sternum and the hyoid bone

Omohyoid muscle

Superficial strap muscle Superior and inferior belly From the shoulder to the hyoid bone Contains a change in direction of pull (due to fascial sling attachment)

What is the blood supply to the thyroid gland?

Superior and inferior thyroid arteries (bilaterally) Thyroid IMA artery (in some patients) - a branch in the midline off of the brachiocephalic trunk

How are the thyroid and parathyroid glands drained of lymph?

Superior deep cervical lymph nodes (above the sternocleidomastoid) Inferior deep cervical lymph nodes (below the sternocleidomastoid) Lymph is returned to either the right lymphatic duct or the thoracic duct

What is the venous drainage of the thyroid gland?

Superior, middle and inferior thyroid veins Superior and middle drain into the internal jugular veins Inferior drains into the left brachiocephalic vein

How is the thyroid related to the larynx and the trachea?

The lateral lobes attach to the lateral aspects of cartilage and to the trachea The isthmus lies anterior to the 2nd and 3rd cartilages of the trachea

Where are the parathyroid glands located?

The posterior surfaces of the thyroid gland's lateral lobes

What is the difference between thyroid cartilage and cricoid cartilage?

Thyroid cartilage is NOT a ring Cricoid cartilage is made of complete rings of cartilage

What is meant by ectopic thyroid tissue?

Thyroid tissue which can be located at any position in the migratory path from which the thyroid descended during development

What muscles are located in the investing fascia?

Trapezius Sternocleidomastoid

What structures are located within the carotid sheaths?

Vagus nerves Deep cervical lymph nodes Carotid arteries Internal jugular veins

Platysma muscles

Very superficial, flat muscles Innervated by the facial nerve Considered as muscles of facial expression