Thyroid gland - doctor2018.jumedicine.com€¦ · Recognize and understand imaging of the thyroid...
Transcript of Thyroid gland - doctor2018.jumedicine.com€¦ · Recognize and understand imaging of the thyroid...
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Thyroid gland
1. Recognize and understand the coverings of the thyroid gland and their clinical
importance.
2. Recognize and understand the main parts of the thyroid gland and their locations,
relations and connections.
3. Comprehend the blood supply of the thyroid gland, their relations with recurrent and
external laryngeal nerves.
4. Understand the embryological origins of the pituitary gland and its associated
malformations.
5. Grasp the clinical correlations of the midline structures of neck related to the thyroid
gland and differentiate between them and the those on the lateral side of the neck.
6. Recognize and understand imaging of the thyroid gland.
7. Grasp the histological structure of the thyroid gland and its cells under light.
- Attention please this is one of the most important glands in the human body as u may
examine lot’s of patients complaining of having issues with it.
So focus on what we are going through here.
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Gross anatomy
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Transverse sections through the neck at the
level of the second sixth cervical vertebrae
It is a midline structure
placed anteriorly
in the lower neck
at the level with
the 5th cervicalto the
1st thoracic vertebrae
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U need to examine the gland physically & know it’s location. So u should NEVER search for it in the upper part of the neck!!
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It consists of
Right and left lobesconnected
By
A narrow midline isthmus
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its apex being directed upward as far as
the oblique line on the lamina of the
thyroid cartilage it doesn’t extend
beyond it.
3- Lobs
Each lobe is pear shaped
Apex
base
attached to the side of the cricoid cartilage by a
lateral thyroid ligament
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its baselies below at the level of the fourth or
5th tracheal ring parallel to them.The rings are easily sensed under the skin. Covered by superficial & deep
fascia.
It should be noted that the normal thyroid gland is
nearly always asymmetric. The right lobe may be even
twice as large as the left lobe.
The right upper pole extends higher up in the neck, and
the lower pole extends lower sometimes, & this should
be taken in consideration as normal variation exists.. So
if u noticed a similar case don’t rush assuming a mass it
could be normal.
Note
The posteromedial aspects of the lobes are
When u remove these muscles which lies next to the apex u’llfind the cricoid cartilage.
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4- THE ISTHMUS
is often present, and it projects
upward from the isthmus
5- Pyramidal lobe
The isthmus extends
upwards &
downwards across
the midline in front
of
the 2ed, 3ed , and 4th
tracheal rings
& it’s variable in size.
A fibrous or fibromuscular band, the levator of the thyroid gland, musculus levator glandulaethyroideae, sometimes descends from the body of the hyoid to the isthmus or pyramidal lobe
if present.
Note
persists in at least 15% of
the population
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True capsule
False capsule
6- Coverings and fascia of the thyroid gland
The thyroid gland is surrounded by a
shiny capsule.
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A-True capsule, a thin fibrous
capsule,
U can see it after removing the
muscles around the gland. This
fascia is formed by condensation of
the stroma of the gland.
It fixes the gland by being
attached by means of dense
connective tissue to the cricoid
cartilage (part of the larynx) and
superior tracheal rings (part of the
trachea).
The True capsule of thyroid capsule is
much denser in front than behind and the
enlarging gland therefore tends
to push backwards, burying itself round the
sides and even the back of the
Clinical note
DyspneaDysphagia
4/2t9r/2a02c0 hea and esophagus.
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There’s nothing In front of the gland except of the strap muscles, fascia & skin(no bone) thus it enlarges anteriorly in late stages; however in the beginning it enlarges posteriorly.
A good ENT doc. Should have a consideration to investigate the thyroid
gland when a patient comes complaining of respiratory or
odynophagia problems because some cases can be asymptomatic regarding the thyroid & a patient won’t think of
visiting an endocrinologist but he would mostly complain :One or
both of them.
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B- False capsuleit is a loose sheath formed by the visceral
portion of the pretracheal layer of deep
cervical fascia external to the true
capsule. The peritracheal fascia separates
the gland from other organs & fixes it in
position.
The false capsule thickens between the
cricoid cartilage and thyroid gland to
form the
ligament of Berry(The suspensory ligament of the thyroid)
gland
(attaches the thyroid gland to trachea)
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Please get attention here: the true capsule exist in every organ & has to deal with the organ it self, which makes it irresponsible nether of the attachments nor of separation of the organ to near by structures USUALLY.
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The false capsule of the thyroid
gland also
attaches the gland to
the larynx and even to the hyoid
bone
This explains why the thyroid gland
follows the movements of the
larynx in swallowing moving up &
down .
This information is important because any pathologic neck
swelling that is part of the
thyroid gland will move upward when the patient isasked to swallow
It is clear that the false
capsule is attached to
Both the larynx and
trachea
Clinical note
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a large goitre will extend downwards into the
superior
mediastinum
(‘Plunging Goitre’)
The pretracheal layer of deep cervical fascia is attached to hyoid bone
Retrosternal Goiter
The attachment of the sternothyroid muscles to the thyroid
cartilage effectively binds down the thyroid gland to the larynx
This limits upward expansion of the gland
if any pathological condition induced it’s
enlargement. So it wouldn’t extend beyond
this area.
However, downward expansion has no limitation
causing Retrosternal Goiter behind the
manubrium & the sternum.
And
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Or
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7- Relations of the Lobes
C-The
sternothyroi
d
B-The
sternohyoid
D-The anterior
border of the
sternocleidomastoid
A-The
superior belly
of the
omohyoid
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If u were a surgeon who wants to remove the thyroid gland u have to be extremely careful dealing with the strap muscles that surrounds it, as well as the four parathyroid glands.
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The anastomosis between
the superior and inferior thyroid arteries.
Posterior view
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Posterolaterally:
The carotid sheath with the
common carotid artery, the
internal jugular vein, and the
vagus nerve
The larynx, the trachea, the pharynx,
and the esophagus. Associated with
these structures are the cricothyroid
muscle and its nerve supply, the
external laryngeal nerve. In the
groove between the esophagus and
the trachea is
the recurrent
laryngeal nerve
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Medially:
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A-The superior thyroid artery
B-The inferior thyroid artery
C- Sometimes the thyroidea ima.
A-The superior thyroid artery, a branch of
the external carotid artery, descends to the
upper pole of each lobe, accompanied by
The External Laryngeal Nerve
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The superior thyroid artery on each side is related
to the external laryngeal nerve, which supplies the
cricothyroid muscle.
Damage to the
external
laryngeal
nerve
results in an
inability to
tense the
vocal folds
and in
hoarseness
Thus, The Superior Thyroid Artery during surgery on the thyroid ,
is ligated near the gland to avoid injury to4/29/2020
the external larynDg
r.She
aa
tarlatnerve
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a branch of the thyrocervical trunk,
ascends behind the gland to the level of
the cricoid cartilage.
It then turns medially and downward to
reach the posterior border of the gland.
The recurrent laryngeal
nervecrosses either in front of or behind the artery,
or it may pass between its branches.
B-The inferior thyroid artery
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The terminal branches of the
inferior
thyroid artery
on each side are related to the
RECURRENT LARYNGEAL
NERVE.
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Thus, THE INFERIOR THYROID ARTERYduring
surgery on the thyroid ,
is ligated away from the gland to avoid injuryto
the recurrent laryngeal nerve
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C-The thyroidea ima, In
approximately 10% of people, a
thyroid ima artery
ascends on the anterior surface of
the trachea, which it supplies,
and continues to the isthmus of
the thyroid gland.
s
arises from the brachiocephalic trunk,
or the arch of the aorta,
from the right common carotid
ubclavian, or internal thoracic arteriesVari
ab
le
Clinical note
The possible presence of this artery
must be considered when performing
procedures in the midline of the neck
inferior to the isthmus because it is a 4p
/2o
9t/e20n
2t0ialsource of bleeding
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Lesions of the Laryngeal Nerves
The muscles of the larynx are innervated by
the recurrent laryngeal nerves, with the
exception of the cricothyroid muscle, which is
supplied by the external laryngeal nerve. Both
these nerves are vulnerable during operations
on the thyroid gland because of the close
relationship between them and the arteries
of the gland.
To be discussed next year
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9-The veins from the thyroid gland
C-The inferior thyroid vein
The inferior thyroid veins of the two
sides anastomose with one another as
they descend in front of the trachea.
They drain into the left brachiocephalic
vein in the thorax
A-Superior thyroid vein
which drains into the internal jugular vein;
B-The middle thyroid vein
which drains into the internal jugular vein;
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10-The lymphatic vessels of the thyroid gland
communicate with a capsular network of
lymphatic vessels
From this network, the vessels pass
initially to prelaryngeal, pretracheal,
and paratracheal lymph nodes, which
drain in turn to the superior and
inferior deep cervical nodes
Inferior to the thyroid gland, the
lymphatic vessels pass directly to the
inferior deep cervical lymph nodes
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The uppermost, just above the
thyroid
isthmus, in front of the cricoid
cartilage, and medial to
a pyramidal lobe, if present, is a
constant node group
of one to five nodes, which has
been termed
The Delphian node
enlargement of which is
indicative of metastasis
from thyroid or
laryngeal carcinoma.
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Edited by: Sarah Qudah.