Prob 6 Thyroid(2)

8/3/2019 Prob 6 Thyroid(2)

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Thyroid

Gland



Gland

Embryology

The thyroid gland

develops as a

thickening in the

pharyngeal floor that

elongates inferiorly as

the thyroglossal duct,

dividing into two lobesas it descends through

the neck.



After migration of the

thyroid to its final

position the thyroglossal

duct usually disappears,

but ectopic thyroidtissue can be found

anywhere along the

thyroglossal tract. This

can produce a number of problems in adult life.



Superiorly; to the middleof thyroid cartilage

Inferiorly; usually to the 5th or 6th tracheal ring

Laterally; just medial to thecommon carotids

Surface Anatomy



Thyroid gland is located in the

anterior part of the lower

neck, extending from the 5thcervical (C5) to the 1st

thoracic (T1) vertebrae. It

consists of two lobes (right

and left) connected by athin, median isthmus

overlying the 2nd to 4th

tracheal rings, typically

forming an "H" or "U" shape. A pyramidal lobe is also often present and it projects upwards from the

isthmus as seen in the diagram. A fibrous or muscular band frequently

connects the pyramidal lobe to the hyoid bone, reflecting the

embryological origin of the gland .



Strap Muscles

• Also called “Infrahyoid ms.”

• They include:

− Omohyoid.

− Sternohyoid.

− Thyrohyoid.

− Sternothyroid.

• They attach the hyoid bone to inferior structures

and depress the hyoid bone, providing a stable pointof attachment for the suprahyoid muscles.





• The lateral surface of the thyroid is covered by the

sternothyroid muscle, and its attachment to the

oblique line of the thyroid cartilage prevents the

superior pole from extending superiorly under the

thyrohyoid muscle.

• The sternohyoid and sternothyroid muscles are

joined in the midline by an avascular fascia that must

be incised to retract the strap muscle laterally in

order to access the thyroid gland during

thyroidectomy.



The thyroid is surrounded by

a sheath that binds the

thyroid to the larynx and

the trachea, which is whyit moves up when

swallowing.

Pretracheal Fascia





• Beneath the visceral layer of the pretracheal,

deep cervical fascia, the thyroid gland is

surrounded by a true inner capsule, which is

thin and adheres closely to the gland.



• The capsule sends

projections into thethyroid forming septae

and dividing it into lobes

and lobules.

• Dense connective tissue

attachments secure the

capsule of the thyroid to

both the cricoid cartilage

and the superior tracheal

rings.



• The thyroid gland is a highly vascular organ.

• Main Arterial blood supply comes from:

– Superior Thyroid artery>> 1st branch of the Ex. Carotid – Inferior Thyroid artery>> The major branch of

thyrocervical trunk.

– Thyroid Ima artery>> Branch of the Aorta

Blood Supply

These vessels lie between the fibrous capsule and the pretracheal

layer of deep cervical fascia





The sup. thyroid a. is accompanied by the

Int. branch of the sup. laryngeal n.

The inf. thyroid a. is accompanied by the

Recurrent laryngeal n.



Venous Drainage

• There are three mainveins that drain the

venous plexus on the

anterior surface of the

thyroid, between the

true and false capsule of

the gland:

‗ Superior ‗ Middle

‗ Inferior

Drain into theint. jagular v.

To the Lt.

brachiocephalic v.



Lymphatic drainage

• Lymphatic drainage of the

thyroid gland is quite

extensive and flows

multidirectionally

• Immediate drainage flows

first to the periglandular

nodes, then to the

prelaryngeal (Delphian),

pretracheal, andparatracheal nodes along

the recurrent laryngeal

nerve, and then to

mediastinal lymph nodes.



Nerve Supply

The nerves are derived

from:

• Superior• Middle

• Inferior

cervical sympathetic

ganglia



The recurrent laryngeal nerve

• a branch of the vagus nerve that supplies motor

function and sensation to the larynx (voice box). It

travels within the endoneurium. It is the nerve of the 6th Branchial Arch.

• It is referred to as "recurrent" because the branches

of the nerve innervate the laryngeal muscles in the

neck through a rather circuitous route: it descendsinto the thorax before rising up between the trachea

and esophagus to reach the neck.



• The nerve splits into anterior and posterior rami

before supplying muscles in the voice box—

itsupplies all laryngeal muscles except for the

cricothyroid, which is innervated by the external

branch of the superior laryngeal nerve.

• The recurrent laryngeal nerve enters the pharynx,along with the inferior laryngeal artery and inferior

laryngeal vein, below the inferior constrictor muscle

to innervate the Intrinsic Muscles of the larynx

responsible for controlling the movements of the

vocal folds

http://en.wikipedia.org/wiki/Muscle

http://en.wikipedia.org/wiki/Cricothyroid_muscle

http://en.wikipedia.org/wiki/Superior_laryngeal_nerve

http://en.wikipedia.org/wiki/Inferior_laryngeal_artery

http://en.wikipedia.org/wiki/Inferior_laryngeal_vein




http://en.wikipedia.org/wiki/Inferior_laryngeal_artery

http://en.wikipedia.org/wiki/Superior_laryngeal_nerve

http://en.wikipedia.org/wiki/Cricothyroid_muscle

http://en.wikipedia.org/wiki/Muscle



• The left laryngeal nerve, which is longer, branches from the

vagus nerve to loop under the arch of the aorta, posterior to

the ligamentum arteriosum before ascending. On the other

hand, the right branch loops around the right subclavian

artery. As the recurrent nerve hooks around the subclavian

artery or aorta, it gives off several cardiac filaments to thedeep part of the cardiac plexus. As it ascends in the neck it

gives off branches, more numerous on the left than on the

right side, to the mucous membrane and muscular coat of

the oesophagus; branches to the mucous membrane andmuscular fibers of the trachea; and some pharyngeal

filaments to the superior pharyngeal constrictor muscle.

http://en.wikipedia.org/wiki/Vagus_nerve

http://en.wikipedia.org/wiki/Arch_of_the_aorta

http://en.wikipedia.org/wiki/Ligamentum_arteriosum

http://en.wikipedia.org/wiki/Right_subclavian_artery


http://en.wikipedia.org/wiki/Subclavian_artery


http://en.wikipedia.org/wiki/Aorta

http://en.wikipedia.org/wiki/Cardiac_plexus

http://en.wikipedia.org/wiki/Oesophagus

http://en.wikipedia.org/wiki/Vertebrate_trachea

http://en.wikipedia.org/wiki/Superior_pharyngeal_constrictor_muscle

http://en.wikipedia.org/wiki/Superior_pharyngeal_constrictor_muscle

http://en.wikipedia.org/wiki/Vertebrate_trachea

http://en.wikipedia.org/wiki/Oesophagus

http://en.wikipedia.org/wiki/Cardiac_plexus

http://en.wikipedia.org/wiki/Aorta





http://en.wikipedia.org/wiki/Ligamentum_arteriosum

http://en.wikipedia.org/wiki/Arch_of_the_aorta

http://en.wikipedia.org/wiki/Vagus_nerve









Damage to Recurrent

Laryngeal nerve

• The nerve is best known for its importance in thyroid

surgery, as it runs immediately posterior to this gland. If it is

damaged during surgery, the patient will have a hoarse

voice. Nerve damage can be assessed by laryngoscopy,during which a stroboscopic light confirms the absence of

movement in the affected side of the vocal cords.

• Similar problems may also be due to invasion of the nerve

by a tumor or after trauma to the neck. A common scenario

is paralysis of the left vocal cord due to malignant tumour in

the mediastinum affecting the left branch of the recurrent

laryngeal nerve. The left cord returns to midline where it

stays.

http://en.wikipedia.org/wiki/Thyroid

http://en.wikipedia.org/wiki/Hoarse

http://en.wikipedia.org/wiki/Laryngoscopy

http://en.wikipedia.org/wiki/Stroboscope

http://en.wikipedia.org/wiki/Tumor

http://en.wikipedia.org/wiki/Physical_trauma

http://en.wikipedia.org/wiki/Physical_trauma

http://en.wikipedia.org/wiki/Tumor

http://en.wikipedia.org/wiki/Stroboscope

http://en.wikipedia.org/wiki/Laryngoscopy

http://en.wikipedia.org/wiki/Hoarse

http://en.wikipedia.org/wiki/Thyroid



•If the damage is unilateral , the patient may present

with voice changes including hoarseness.

•Bilateral nerve damage can result in breathing

difficulties and aphonia, the inability to speak.

•The right recurrent laryngeal nerve is more

susceptible to damage during thyroid surgery due to

its relatively medial location.

http://en.wikipedia.org/wiki/Aphonia

http://en.wikipedia.org/wiki/Aphonia



Parathyroid Gland

• Usually four – two on

each side (2-8 is normal).

• Lie on the posterior

surface of thyroid withinits fascial capsule .

• May be embedded

within thyroid gland.

• Regulatecalcium/phosphate

levels.

• Required for life.



1. Yellow-brown, ovoid or lentiform structures.

2. Weight ~ 50 mg each.

3. Measuring about 6 mm long in their greatest diameter.

4. Lie between thyroid lobes & carotid sheath.

5. Close proximity to:

a. Tracheoesophageal groove b. longus colli muscles

6. Position of superior glands is more constant at the level

of the middle of the posterior border of the thyroid

gland.7. Inferior glands lie close to the inferior poles of the

thyroid gland.

8. Aberrant glands may lie between trachea & thyroid.



• Have a rich blood supply from:

the inferior thyroid arteries or from anastomoses between

the superior and inferior vessels.

• The venous drainage into:

the superior, middle, and inferior thyroid v. veins.

• Lymph Drainage:

Deep cervical and paratracheal lymph nodes.

• Nerve Supply:

Superior or middle cervical sympathetic ganglia.

control the calcium in our bodies--how much calcium is

in our bones, and how much calcium is in our blood .



Clinical Approach to

thyroid swelling



History

• Local symptoms:

– Lump (painful or painless)

– Dysphagia – Dyspnoea

– Hoarseness

– Pain



Cont.

• Endocrine symptoms

– Hyperthyroidism: nervousness, irritability,

palpitation, diarrhea, hot intolerance, amenorrhea

– Hypothyrodism: slow thought, dry skin, cold

intolerance , constipation,

– Euthyroid



Physical Examination

• Local examination:

– Size, shape, surface, consistancy, movement withsallowing, tenderness

– Percuss over manbrium.

– Ascultation

• General xamination

– Hand: pulse, tremor

– Eye: lid retration, lid lag, exophthalmos,chemosis

– Cardiovascular, nervous, …etc



Differential Diagnosis

• Diffuse enlargement: – Thyroiditis

– Iodine deficiency

– Physiological ( pregnancy ,puberty)

– Graves disease

• Multinodular enlargement: – Multinodular goiter

– Cancer: lymphoma, anaplastic,

medulary• Solitary nodule:

– Cyst,

– Adenoma

– Cancer: follicular, papillary



Differential Diagnosis



Complications of Thyroid

swelling• Tracheal obstruction by compression .

• Secondary thyrotoxicosis .

• Cyst formation .

• Hemorrhage into a nodule.

• Calcification may occur in long

standing cases .



Complications of Thyroid

swelling

• Retrosternal extension .

• Malignancy

• Metastasis from thyroid cancer

1. locally

2- distal



Investigation

hypothyroidismhyperthyroidismTest

DecreasedincreasedfreeT3, T4

IncreaseddecreasedTSH

Hypoactive (cold)Hyperactive (hot)Radioactive iodine scan

Antithyroid perioxidaseor antithyroglobulin(hashimato’s thyroditis)

TSH receptor,antithyroglubin,antimicrosomalantibodies ( Graves

disease)

Antibodies

• Thyroid function tests and Autoantibodies:



Cont.

• Ultrasound

• Aspiration of cyst

• Fine needle aspiration cytology (FNAC)

• Open biopsy



Treatment

• Analgesic and anti inflammatory drugs

– Inflammatory goiter

• Replacement therapy (thyroxine)

– Hypothyroidism

• Antithyroid drugs ( carbimazole, PTU)

– Hyperthyroidism



Cont.

• Surgical excision:

– Large goiter, unresponsive to medication, Cancers

• Radioactive iodine

– Unfit for surgery



Thyroidectomy



Complication of thyroid

surgery• Damage to recurrent laryngeal nerve ….. leading

to palsy & causing hoarseness.

• Damage to external branch of superior laryngealnerve … leading to palsy & hoarseness

• Hypocalcaemia …caused by damage toparathyroids

• Haemorrhage…causing laryngeal oedema &

respiratory compromise.



56 year old attended the surgical clinic for an

ant. neck swelling. It was associated withpain radiating to the air and change in hisvoice.

The swelling has a special shape and ismoving with deglutition. Two moreswellings are palpable on the Rt. side at themedial edge of the sternomastoid ms.

The surgeon diagnosed a thyroid swellingand decided to remove the gland.



During the operation, the surgeon incised the

skin, subcutaneous fat and a thin ms.transversely, after which he opened thedeeper fascia and separated the related ms.

longitudinally. ? Infrahyoid muscles:

On reaching the ant. Surface of the gland, thesurgeon ligated the related artries and veins.

• Omohyoid

• Sternohyoid

• Thyrohyoid

• Sternothyroid

?



The surgeon was carefully looking in aspecific location for a nerve.

Furthermore, he was also very careful topreserve tiny structures behind each pole of

the thyroid gland.

?Importance

?Importance

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Prob 6 Thyroid(2)