& PARATHYROID

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Note: this teamwork is involving only the anatomy part of the lecture, embryology part is covered by the Embryology team, Don’t forget to check their work also. The main 3 parts (layers) of the deep fascia or deep cervical fascia of the

1- Investing layer.it surrounds the sternocleidomastoid muscle (anteriorly), trapezius muscle (posteriorly), parotid, submandibular and sublingual gland (salivary glands). 2- Pretracheal layer.it surrounds the & thyroid 3- Prevertebral layer. It surrounds the vertebral muscles of the neck.

Thyroid gland

Each lobe is pear- shaped, with its apex Endocrine, butterfly shaped gland. (superiorly) reaches up to the oblique line of NOTE: thyroid cartilage.(sternothyroid muscle insertion) Every gland in our body is covered by a Its base (inferiorly) lies at the level of 4th or 5th capsule(layer), Consists of right & left lobes. tracheal rings. & we can say that the thyroid gland is composed of two The 2 lobes are connected to each other in the capsules: midline by a narrow isthmus, which overlies the Inside the pretracheal facial capsule, there is 1-the pretracheal 2nd 3rd & 4th tracheal rings. another capsule. layer (outer So, it s surrounded by 2 membranes capsule.) 2-fibrous C.T It is surrounded by a facial sheath derived . from the pretracheal layer of the deep cervical capsule (inner fascia. capsule) 3rd small pyramidal lobe is often present which projects from the upper border of the isthmus superior & inferior usually to left of middle line. Parathyroid glands Relation to Pyramidal lobe is connected to hyoid bone by a the rounded fibrous or smooth muscular band called levator posterior glandulae thyroideae. border anastomosis between superior & inferior thyroid This represents the fibrosed & obliterated arteries. thyroglossal duct. NOTE: -50% of people have the pyramidal lobe. -The pyramidal lobe is the remnant of the thyroglossal duct.

RELATION OF THYROID GLAND

Posteriorly (or Anterolaterally (4S) Medially posterolaterally)

Above Below

Carotid & pharynx Trachea & esophagus 1. Sternothyroid. Carotid sheath & its contents sheath is 2. Sternohyoid. which are (vagus nerve, also 3. Superior belly of omohyoid common ”& internal” carotid Recurrent laryngeal nerve in between them derived (most lateral) artery, internal jugular & (supplies the focal cords & the mucous of the larynx) from the 4. Sternomastoid.(overlying the 3 deep cervical lymph nodes) & external laryngeal nerve deep muscles) fascia. Cricothyroid (produces tension and elongation of the vocal folds so aids phonation) & inferior constrictor muscles ARTERIAL SUPPLY the the laryngealnerve It It runs along the It It It isa branch from the descends isthmus fellow the the lobe, superior Superior Superior thyroid (from (from the other side) carotid to to anastomosis withits to to the with the external laryngeal nerve) ( → upper border artery 2 1 Inferior thyroid artery has many branches such as: NOTE: vagus upper pole - - descending branch ascending branch external nerve of of → of of the arch It → If present ascends Thyroidea brachiocephalic brachiocephalic → trachea the anastomosis anastomosis with superior the thyroid artery (directly) from from supply the postero artery. isthmus aortic , it arises in in front of to reach or from or from ima . From the - It inferior pole thyroid of gland The The ascends Then Then it reaches the Then Then it curves recurrent recurrent laryngealnerve thyrocervical trunk behind the gland to the of level behind descends medially it . Inferior Inferior thyroid (or (or between posterior behind the the behind of downwards. 1 st crosses either in aspect of the gland & part of 2 branches) carotid sheath subclavian cricoid cartilage front artery, . or Clinical notes External laryngeal nerve Recurrent laryngeal nerve (more dangerous)

The inferior thyroid artery is closely associated with it. This nerve can be found , in a triangle*. It runs close to the superior thyroid artery before turning The relationship of the recurrent laryngeal nerve and the medially to supply the . High ligation of inferior thyroid artery is highly variable in that the nerve can the superior thyroid artery during thyroidectomy places this lie deep or superficial to the artery, or between the branches nerve at risk of injury, so it should be ligated within the of the artery, and be different on either side of the neck. upper pole of the gland. So, Consideration of this nerve and its branches must be given during thyroidectomy

Its lesion will cause horsiness of voice. Its lesion may results in impaired breathing & speech.

*The triangle is bounded: 1-laterally→ NOTE: Bilateral lesion is more dangerous than unilateral 2-medially→ trachea lesion (because it will compensate from the other side) 3-superiorly→ thyroid lobe.

Veins Lymph & & 1-Superior thyroid vein → internal -Deep cervical. (chain alongside the )

2- Middle thyroid vein → internal jugular vein -paratracheal lymph nodes.

VENOUS DRAINAGE LYMPHATIC LYMPHATIC 3- Inferior thyroid vein → left 2 4 position position the at border about about superior superior small small of of the has has a 6 ovoid bodies, ovoid bodies, of of the gland. posterior mm. long mm. constant parathyroid parathyroid middle . They They lie gland,(between gland,(between the sometimes sometimes usually at the level of usually of at the level 2 They They lie inferior inferior capsule capsule the the thyroid tissue thyroid tissue membranes) facial facial capsule within inferior parathyroid parathyroid within outside of the of the the pole. . facial facial the the or or . the the 2 ARTERIES LYPHATIC NERVES NODES superior superior & inferior thyroid arteries sympathetic sympathetic ganglia Deep cervical paratracheal& superior, middle and inferior There There is Superior & middle cervical lymphnodes. thyroid veins no innervation known secrotomotor known secrotomotor (vasomotor). . . . MCQ’s 1-Which of the following tracheal cartilage located behind isthmus of 6-Which one of the following is medial to thyroid gland? thyroid gland: A- sternomastoid. A- 1st, 2nd and 3rd tracheal rings. B- vagus nerve. B- 2nd, 3rd and 4th tracheal rings. C- trachea. C- 3rd, 4th and 5th tracheal rings. D- common carotid artery. D- 4th, 5th and 6th tracheal rings. 7-Inferior thyroid artery branch of? 2-Thyroid gland surrounded by 2 membranes. It’s capsule and? A- internal carotid artery. A- investing layer. B- external carotid artery. B- pretracheal layer. C- thyrocervical of subclavian artery. C- prevertebral layer. D- aortic arch. D- carotid sheath. 8-After thyroidectomy patient complained of horsiness of 3-Pyramidal lobe is connected to hyoid bone by a fibrous or muscular the voice. When the surgeon ligation the superior thyroid band called? artery he damaged the nerve near it. Which one of the A- thyrohyoid. following nerve is endanger in ligation of the STA? B- levator glandulae thyroideae. A- external laryngeal. C- sternohyoid. B- recurrent laryngeal. D- coricohyoid. C- internal laryngeal. D- superior laryngeal. 4-Which of the following muscles lies anterolaterally to the thyroid gland? A- inferior belly of omohyoid. 9-Middle thyroid vein drainages into? B- sternohyoid. A- internal jugular vein. C- coricohyoid. B- . D- levator glandulae thyroideae. C- left brachiocephalic vein. D- right brachiocephalic vein. 5-Which one of the following is posterior to thyroid gland A- sternomastoid. 10-Where are the two superior parathyroid gland site in B- recurrent laryngeal nerves. relation to the thyroid gland? C- trachea. A- at superior of the posterior border of the gland. D- common carotid artery. B- at the middle of the posterior border of the gland. C- at the inferior of the posterior border of the gland. THANK YOU FOR CHECKING OUR WORK GOOD LUCK DOCTORS

Key Answers: 1-B 2-B 3-B 4-B 5-D 6-C 7-C 8-A 9-A 10-B

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