prob 6 thyroid(2)
TRANSCRIPT
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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.
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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.
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Superiorly; to the middleof thyroid cartilage
Inferiorly; usually to the 5th or 6th tracheal ring
Laterally; just medial to thecommon carotids
Surface Anatomy
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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 .
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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.
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• 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.
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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
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• 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.
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• 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.
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• 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
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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.
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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.
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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.
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Nerve Supply
The nerves are derived
from:
• Superior• Middle
• Inferior
cervical sympathetic
ganglia
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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.
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• 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
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• 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.
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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.
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•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.
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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.
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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.
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• 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 .
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Clinical Approach to
thyroid swelling
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History
• Local symptoms:
– Lump (painful or painless)
– Dysphagia – Dyspnoea
– Hoarseness
– Pain
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Cont.
• Endocrine symptoms
– Hyperthyroidism: nervousness, irritability,
palpitation, diarrhea, hot intolerance, amenorrhea
– Hypothyrodism: slow thought, dry skin, cold
intolerance , constipation,
– Euthyroid
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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
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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
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Differential Diagnosis
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Complications of Thyroid
swelling• Tracheal obstruction by compression .
• Secondary thyrotoxicosis .
• Cyst formation .
• Hemorrhage into a nodule.
• Calcification may occur in long
standing cases .
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Complications of Thyroid
swelling
• Retrosternal extension .
• Malignancy
• Metastasis from thyroid cancer
1. locally
2- distal
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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:
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Cont.
• Ultrasound
• Aspiration of cyst
• Fine needle aspiration cytology (FNAC)
• Open biopsy
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Treatment
• Analgesic and anti inflammatory drugs
– Inflammatory goiter
• Replacement therapy (thyroxine)
– Hypothyroidism
• Antithyroid drugs ( carbimazole, PTU)
– Hyperthyroidism
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Cont.
• Surgical excision:
– Large goiter, unresponsive to medication, Cancers
• Radioactive iodine
– Unfit for surgery
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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.
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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.
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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
?