lec 2 anatomy endo

1. Relations of Thyroid Lobes

➪ Anterolateral: Sternomastoid, sternohyoid, sternothyroid, sup.omohyoid

➪ Posterior: Carotid sheath (with contents), parathyroid glands

➪ Medial: Larynx, trachea, pharynx, esophagus, recurrent laryngeal nerve

2. Relations of Thyroid Isthmus

. Relations of Thyroid Isthmus

➪ Anterior: Skin, platysma, sternohyoid, sternothyroid, anterior jugular vein

➪ Posterior: 2nd–4th tracheal rings

➪ Upper border: Anastomosis of superior thyroid arteries

➪ Lower border: Inferior thyroid vein, thyroidea ima artery

3. Arterial Supply of Thyroid & Its Origin

3. Arterial Supply of Thyroid & Its Origin

➪ Superior thyroid artery: From external carotid artery

➪ Inferior thyroid artery: From thyrocervical trunk

➪ Thyroidea ima artery (if present): From aortic arch or brachiocephalic artery

4. Venous Drainage of Thyroid & Its Origin

4. Venous Drainage of Thyroid & Its Origin

➪ Superior Thyroid Vein: Drain into internal jugular vein

➪ middle Thyroid Vein: Drain into internal jugular vein

➪ Inferior Thyroid Vein: Drains into left innominate vein

5. Congenital Anomalies of Thyroid

Congenital Anomalies of Thyroid

➪ Incomplete descent (e.g. lingual thyroid)

➪ Thyroglossal cyst

➪ Thyroglossal fistula

➪ Agenesis → cretinism

➪ Ectopic thyroid tissue (thorax, bronchi, esophagus)

6. Origin of Parathyroid Gland

. Origin of Parathyroid Gland

Inferior parathyroid: From dorsal wing of 3rd pharyngeal pouch

Superior parathyroid: From dorsal wing of 4th pharyngeal pouch

Q1: Mention the arterial blood supply of the thyroid gland and the source of each

Answer:

1. Superior thyroid artery: Arises from the external carotid artery.

2. Inferior thyroid artery: Arises from the thyrocervical trunk (a branch of the subclavian artery).

3. Thyroidea ima artery (in 10% of cases): Arises from the brachiocephalic trunk or the arch of aorta.

Q2: Explain the surgical rules for ligating thyroid arteries and their relation to nearby nerves.

Answer:

1. Superior thyroid artery: Must be ligated near the upper pole of the gland to avoid injuring the external laryngeal nerve.

2. Inferior thyroid artery: Must be ligated away from the gland to avoid injuring the recurrent laryngeal nerve which runs close to it near the gland.

Q3: State the embryological origin of the parathyroid glands.

Answer:

1. Superior parathyroid glands: Develop from the dorsal part of the 4th pharyngeal pouch.

2. Inferior parathyroid glands: Develop from the dorsal part of the 3rd pharyngeal pouch (and migrate downward with the thymus