Thyroid Flashcards by Dr Me

Largest endocrine gland in the body is ?

Thyroid gland

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Shape of thyroid gland?

Butterfly shape

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Weight of thyroid gland?

Around 20gm ( 8 + 4 + 8)

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Measurement of thyroid gland?

4 * 2.5 * 2 cm

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Importance of knowing measurement ?

In subtotal thyroidectomy we leave part measuring as normal

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Site of thyroid?

Lower part of the front of neck opposite the 5th 6th and 7th cervical vertebrae

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Where does the apex and base of thyroid gland lie?

Apex lies on the thyroid cartilage below the oblique line

Base lies at the level of 6th tracheal ring

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Site of isthmus of thyroid?

Opposite the 2nd 3rd and 4th tracheal rings

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Whats the value of thyroid and tracheal rings ?

Cause goiter causes dysnea but its should be severe in order to compress the c shaped rings.

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Capsules of the thyroid gland?

True capsule from the stroma of the gland

False capsule from pre tracheal fascia

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Attachment of pretracheal fascia?

Attach to hyoid bone and thyroid cartilage superiorly. To carotid sheath from sides and to fibrous pericardium and arch of aorta inferiorly

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Why does the thyroid gland moves up and down with deglutination?

Cause it is inside pretracheal fascia. Pretracheal fascia attached to hyoid bone. And digastric ms moves the hyoid bone superiorly during deglutination

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What are the contents of pretracheal fascia?

Thyroid gland
Parathyroid gland
Thyroglossal cyst (if present)
Lymph node (Delphi)

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Superficial relations of thyroid gland?

Skin
SC tissue (yellow)
Platysma muscle
Investing layer of deep cervical fascia
Stenomastoid ms
Strapmuscles
Pretracheal fascia

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Value of strap muscles in thyroid surgery?

supplied by ansa cervicalis from below cut ms as high as possible

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Action and nerve supply of sternomastoid?

If 1 ms – face to opposite side
If both flexion of neck
N supply spinal part of accessory nerve

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What are the strap muscles?

Sternothyroid
Sternohyoid
Omohyoid

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Medial relations of thyroid gland?

Lower part ( trachea, esophagus with recurrent laryngeal N in between)
Upper part (cricoid and thyroid cartilage, crycothyroid ms and inf constrictor of the pharynx (pharynx and larynx)

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Surgical importance of relations of thyroid gland?

Dysphagia and dysnea may occur with its enlargement due to its relation to trachea and osophagus
Pyramidal lobe must be removed in sistruck’s operation

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What causes the thyroid to enlarge retrosternally?

Sternothyroid ms

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Posterior relations of thyroid gland?

Sympathetic chain and Carotid sheath which contain:

Carotid artery
Internal jugular vein
The vagus

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Ansa means?

Neck

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Origin of platysma muscle?

Penniculus carnosus ( the whole body covered by it durin embryogenesis only 3 ms left)

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What are the reminants of penniculus carnosus?

Platysma ms
Dartos ms (in scrotum)
Corrigator cutis ani

Nerve supply of platysma muscle?

Cervical br of facial nerve

Surgical importance of platysma muscle?

It should be sutured separately with no attachment sup or deep to it or else ugly scar

11 steps of subtotal thyroidectomy ?

1. Supine position 2. Pillow interscapular area 3. Ring under head for support 4. Elevate bed 15° 5. Sterilize from mandible to nipple(betadine) 6. Collar incision 2 cm above suprasternal notch 7. Retractors to sternomastoid 8. Cut strap ms as high as possible 9. Ligate middle thyroid V 10. STA ligate within gland 11. ITA ligate away from gland

Why do you put pillow in interscapular region for ?

Hyperextension of neck

Why do you elevate bed 15°?

Well drainage of the vessels

How long is the collar incision?

From post border of sternomastoid to post border of sternomastoid

Why do u incise 2 cm superior to supra sternal notch?

Healing is not so good with excessive granulation tissue causing post operative keloid

Why middle thyroid V is the first vein to be ligated?

It is the shortest

What to keep in mind while ligating middle thyroid V?

Congenital anomaly… non RLN in 1 to 2% people

Why STA is ligated within gland?

To avoid injury to EXT laryngeal N

From where does external laryngeal n comes?

From superior laryngeal nerve. It gives both internal LN and external LN

Injury to Ext laryngeal n leads to?

Loss of high pitched voice and voice fatigue (opera singers)

Why ITA is ligated away from gland?

To avoid injury to RLN

RLN injury leads to?

``` Complete paralysis (voice) Incomplete paralysis (respiration) ```

Complication of subtotal thyroidectomy?

1. Bleeding 2. Injury to n and vessels 3. Keloid if … 4. Tetany if parathyroid excised 5. Respiratory obst ( if too tight suture or bleeding into it)

Arterial supply of thyroid?

1. Superior thyroid artery 2. Inferior thyroid artery 3. Thyroid ima artery (present in some ppl) 4. Accessory tracheal & esophageal arteries

Ima means?

Aorta

Superior thyroid artery is from?

1st br of ext carotid A. related to external laryngeal n.

Inferior thyroid artery is from?

From thyrocarvial trunk which is a br of 1st part of subclavian A.its terminal br near the gland are in close relation to RLN( inbetween above or below terminal branches)

Thyroid ima artery is from?

Arch of aorta or innominate artery present in 1 to 3% people (may cause severe

Accessory tracheal and osophageal arteries ?

In ligament of berry’s

What is ligament of berry?

Thickened part of the pretracheal fascia that joins trachea to the thyroid gland

What supplies the thyroid gland after subtotal thyroidectomy ?

Accessory tracheal and osophageal arteries

Surgical importance of STA?

Should be ligated within the gland to avoid injury to the ext laryngeal nerve

Surgical importance of ITA?

Should be ligated away from the gland to avoid injury to RLN and also should be ligated in continuity, do not cut (slippery of ligature – stump falls in chest – hemothorax) if occurred ttt by thoracotomy

Branches of thyrocervical trunk?

1. Inferior thyroid artery 2. Transverse cervical artery 3. Supra scapular artery

What is the venous drainage of the thyroid gland?

1. Superior thyroid vein 2. Middle thyroid vein 3. Inferior thyroid (10 to 12 veins)

Drainage of superior thyroid vein?

To internal jugular vein or common facial vein

Drainage of middle thyroid vein?

It crosses the common carotid to join internal jugular vein

Drainage of inferior thyroid veins ?

From the isthmus over the front of the trachea to join the left innominate vein

Surgical importance of middle thyroid vein?

Shortest vein so first to be tied and cut in surgery

Lymphatics drainage of thyroid gland?

1. Peripheral part to upper and lower deep cervical LN 2. Medial parts of both lobes a. Prelaryngeal LN over cricothyroid membrane b. Pretracheal LN c. Deep cervical LN – paratracheal LN (mediastinal)

Another name for pre laryngeal LN ?

Gland of Poirier

The structure of thyroid gland?

Formed of follicles likes with cuboidal epithelium( which is the parynchyma) and vascular CT stroma. No basement membrane