2. The thyroid glandThe thyroid gland
Lobes
Position
Blood supply
Development
Parathyroid glands
Tracheostomy
Related topicRelated topic
Plan of the neckPlan of the neck
3. The thyroid gland
derives its name
from the
thyroid cartilage
which resembles a
shield
(G. thyreos = shield)
4. Function
The thyroid gland is
an endocrine gland
that is responsible for
the secretion of
thyroxin and
thyrocalcitonin
5. Lobes
The thyroid gland
consists of two lobes
united in front of the
second, third and
fourth tracheal rings
by an isthmus of
gland tissue.
isthmusisthmus
6. Lobes
Each lobe is pear-
shaped consisting of
a narrow upper pole
and a broader lower
pole
upper poleupper pole
lower polelower pole
7. Thyroid scan
This nuclear scan uses
an injectable radioactive
compound. When
injected into the
bloodstream the
compound will be
concentrated in the
thyroid gland resulting in
an image of the gland
The test can be useful in
diagnosis of thyroid tumor
8. Position
It lies under cover of sternothyroid and
sternohyoid muscles on the side of the larynx
and trachea
sternothyroid
sternohyoid
9. Position
The upper pole of the thyroid cannot normally
rise above the level of the oblique lineoblique line of the
thyroid cartilage
Thyroid, upper pole
sternothyroid
thyrohyoid
cricothyroid
10. The thyroid gland is
caught in the pocket
of sternothyroid
thyroid
cricoidthyroidcartilage
sternothyroidsternothyroid
thyrohyoid
cricothyroid
Position
11. The lower pole of the
thyroid gland extends
along the side of the
trachea as low as the
sixth tracheal ring
1
2
3
4
5
6
Position
12. Because of the proximity of the thyroid gland to the trachea
and esophagus, goiter causes compression of the trachea
and esophagus resulting in dyspnea and dysphagia
respectively
esophagusesophagus
21. Pre-tracheal fascia
The pre-tracheal
fascia attaches the
thyroid gland to the
trachea and larynx
thus the thyroid
moves upwards on
swallowing, an
important diagnostic
feature for lumps in
the neck
thyroid
larynx
22. Blood supply
The thyroid gland is very
vascular
The vessels lie between
the capsule and the pre-
tracheal fascia.
In some pathological
conditions such as
thyrotoxicosis, owing to
its high vascularity, the
blood flow can be heard
with a stethoscope as a
bruit
23. Thyroid arteries
The main arteries are
the superior and
inferior thyroid
arteries.
superiorsuperior
thyroid a.thyroid a.
inferiorinferior
thyroid a.thyroid a.
24. Superiorthyroidartery
Arises from the
anterior surface
of the external
carotid
immediately
distal to the
carotid
bifurcation.
externalexternal
carotid a.carotid a.
carotidcarotid
bifurcationbifurcation
25. Superior thyroid artery
Arches downwards,
giving a
sternomastoid
branch and a
superior laryngeal
branch that enters
the larynx with the
nerve of the same
name
superior
laryngeal
a. & n.
27. Superior thyroid artery
before reaching the
upper pole of the
gland, and within the
pre-tracheal fascia, it
divides into two main
branches one for
either surface of the
gland
anterior posterior
28. Superior thyroid artery
the posterior branch
anastomoses with the
inferior thyroid artery
posterior br.
of superior
thyroid a.
inferior
thyroid a.
29. Inferior thyroid artery
Is a branch
of the
thyrocervical
trunk from
the
subclavian
artery. subclavian a.subclavian a.
thyrocervicalthyrocervical
trunktrunk
inferiorinferior
thyroid a.thyroid a.
30. Inferior thyroid artery
Ascends and
turns medially
at the level of
the cricoid
cartilage to
enter the back
of the gland
some distance
above the
lower pole.
31. Inferior thyroid artery
The tortuous course of
the inferior thyroid artery
is due to the fact that in
every swallow the thyroid
gland ascends a few
centimeters and must
naturally drag its blood
supply with it.
If this artery has no
capability to elongate, it
would be traumatized
32. Inferior thyroid artery
Divides outside the
pre-tracheal fascia
into four or five
branches that pierce
the fascia separately
to reach the lower
pole of the gland.
Remember that the superior thyroidRemember that the superior thyroid
artery divides within the pretrachealartery divides within the pretracheal
fasciafascia
33. The recurrent laryngeal nerve lies normally behind the
branches of the inferior thyroid artery
34. The recurrent laryngeal nerve lies normally behind the
branches of the inferior thyroid artery
but it is common for the nerve to pass between the
artery branches before they pass through the fascia.
35. The recurrent
laryngeal
nerve always
lies behind
the pre-
tracheal
fascia and if
this structure
remains intact
during
thyroidectomy
the nerve will
not have been
divided
recurrent laryngeal n.
inferior thyroid a.
36. Both thyroid arteries are
related to nerves which
must be avoided when
tying the arteries.
37. A little distance
behind the superior
thyroid artery is the
external laryngeal
nerve.
superior thyroid a.
external laryngeal n.
external laryngeal n.
internal laryngeal n.
superior laryngeal n.
39. To avoid injury to the
external laryngeal
nerve, the superior
thyroid artery is
ligated and sectioned
near the superior
pole of the thyroid
gland where it is notnot
so closely related to
the nerve as it is at
its origin.
40. Section of the
external laryngeal
nerve produces
weakness of voice,
since the vocal fold
cannot be tensed.
The cricothyroid
muscle is paralyzed
Cricothyroid tenses the vocal cordCricothyroid tenses the vocal cord
41. The recurrent laryngeal nerve has a variable
relationship to the inferior thyroid artery
because of its proximity to the inferior thyroid
artery and the pre-tracheal fascia it may be
injured while ligating the artery during
thyroidectomy
42. hence the advisability of
ligating the inferior
thyroid artery well lateral
to the gland before it
begins to divide into its
terminal branches.
the inferior thyroid artery
gives off esophageal
and inferior laryngeal
branches before its
terminal distribution into
the thyroid gland
site of
inferior
thyroid a.
ligation
site of
superior
thyroid a.
ligation
43. The variable relationship of the inferior thyroid
artery to the recurrent laryngeal nerve makes
thyroid surgery a potential risk to normal
speech
The recurrent laryngeal nerve supplies all the
intrinsic muscles of the larynx
44. it is advisable that a
surgeon about to perform
a thyroidectomy
examines the vocal cords
prior to operation, so that
if there is any problem
postoperatively one
knows at least the origin
of the lesion.
45. Recurrent laryngeal nerve damage
Is a complication of
thyroid surgery that
causes paralysis of
the vocal cords
When bilateral the
voice is almost
absent as the two
vocal folds cannot be
adducted.
46. Recurrent laryngeal nerve damage
A unilateral recurrent
laryngeal nerve injury
may not be noticed in
normal speech but
would be very
detrimental to a
singers career.
49. In operations of
partial or sub-
total
thyroidectomy,
all but the
posterior part of
the gland
excised
remaining
thyroid
tissue
50. the dangerous
anatomy lies in the
posterior lateral lobes
(recurrent laryngeal
nerve and the
parathyroid glands)
Recurrent
laryngeal n.
parathyroid
gland
51. The remains of
the gland are
located
alongside the
trachea and
contain the
parathyroid
glands, the
whole being
supplied with
blood by the
anastomosis
52. Thyroidae ima artery
In about 10% of
individuals, an unpaired
artery, the thyroidae ima
(L. ima = lowest) is a
small occasional artery
from the brachiocephalic
trunk, or left common
carotid artery, or direct
from the arch of the aorta
54. Thyroidae ima artery
The possible presence of
the thyroid ima artery
must be remembered
when incising the trachea
inferior to the isthmus.
As the thyroidae ima runs
anterior to the trachea, it
is a potential source of
serious bleeding
55. Thyroid veins
The veins are three in
number on each side
the superior
thyroid vein from
the upper pole follows
the artery and enters
the internal jugular
vein or the common
facial vein
Superior thyroid v.
Internal jugular v.
56. The middle thyroid
vein is short and
wide, it enters the
internal jugular vein
Thyroid veins
middle thyroid v.
Internal jugular v.
57. From the isthmus and
lower pole of the gland
the inferior thyroid
veins form a plexus
within the pre-tracheal
fascia that descends in
front of the trachea to
reach the left
brachiocephalic vein
Thyroid veins
inferior thyroid vv.
brachiocephalic v.
58. As the inferior thyroid
veins cover the anterior
surface of the trachea
inferior to isthmus, they
are potential sources of
bleeding during
tracheotomy (also
remember the situation of
the thyroidae ima artery).
Inferior thyroid
veins
59. Development of the thyroid gland
The gland begins as
a diverticulum from
the floor of the
embryonic pharynx
60. Development of the thyroid gland
The diverticulum
grows caudally
superficial to the
hyoid before dividing
into two lobes
The stem of the
diverticulum, the
thyroglossal duct,
normally disappears
hyoid
Thyroglossal duct
61. Development of the thyroid gland
After the tongue has
developed, it can be seen
that the point of
outgrowth of the
thyroglossal duct is the
foramen cecum (of
Morgagni) [Morgagni,
Giovanni Battista, 1682-1771, a
Padua anatomist and pathologist,
also known for hydatid of
Morgagni (appendix testis) and
anal columns (of Morgagni)].
62. Thyroglossal cyst
cysts derived from the
duct may also appear
anywhere between
the foramen cecum
and the normal
position in the midline
of the neck
1. Beneath foramen cecum
2. Floor of the mouth
3. Suprahyoid
4. Subhyoid
5. On thyroid cartilage
6. At level of cricoid cartilage
63. Thyroglossal cyst
Can be diagnosed
because
characteristically it
moves upwards as
the patient puts his
tongue out.
65. Although the
duct lies
ventral to the
hyoid bone,
it passes up
for a short
distance
behind the
body, which
therefore
has to be
excised with
the duct
67. Lingual thyroid
Rarely the thyroid
fails to descend
during development
resulting in the
development of a
lingual thyroid
68. Ectopic thyroid
Failure of descent
mar result in a
superior cervical
thyroid in the region
of the hyoid bone
the thyroid may
sometimes
descended too far
and be found in the
superior mediastinum
69. Parathyroid glands
Two on each side
They are yellow-brown
endocrine glands, about
the size of a small pea
(about 0.5x0.8 cm
ovoids)
They are important
because of their role in
calcium metabolism.
They secrete
parathormone that
mobilizes bone calcium
and increases gut and
kidney calcium
absorption
71. Superior parathyroid glands
more constant in
position
embedded in the
posterior surface of
the thyroid gland, a
short distance above
the entry of inferior
thyroid artery (and the
level of the cricoid
cartilage).
74. The thymusthymus also develops from the third pouch and
may therefore carry the inferior parathyroidparathyroid with it
when it descends into the thorax.
Parathyroid
development
75. Parathyroid glands, blood supply
The glands are
usually supplied by
the inferior thyroid
arteries but may also
be supplied by both
superior and inferior
thyroid arteries
posterior br.
of superior
thyroid a.
inferiorinferior
thyroid a.thyroid a.
76. Parathyroid glands
Awareness of the
close relationship
between the
parathyroid glands
and the thyroid gland
is essential to prevent
removal or damage of
the parathyroid
glands during
thyroidectomy.
78. The variability in position of the parathyroid glands may
create a problem during total thyroidectomy; in this case the
parathyroid glands are saved by following their small
vessels which are kept intact before the thyroid is removed.
79. When tracheostomy is done electively after
establishing an airway with an endotracheal tube,
a short transverse incision is made one cm below
the cricoid cartilage
Tracheostomy
EndotrachealtubeEndotrachealtube
85. The second tracheal
ring is precisely
identified and divided
vertically in the midline,
extending the incision
through the third ring in
most cases
The first ring is
preserved
Tracheostomy
86. A thyroid retractor gently
spreads the tracheal
opening.
The tracheostomy tube
with obturator is
introduced after
withdrawing the
endotracheal tube under
direct vision to a point
just above the stoma
Tracheostomy
retractor
Tracheostomy tube
Endotracheal tube
87. Tracheostomy
If more room is needed,
the fourth ring may be
partially divided
A transverse incision is to
be avoided.
The skin is closed loosely
The flange of the
tracheostomy tube not
only is tied with a tape
around the neck but also
is sutured to the skin.
Tracheostomy tube flange
4th
tracheal ring
88. Tracheostomy
The endotracheal tube is
removed only when the
tracheostomy tube has
been shown to provide a
satisfactory airway
If there is any question
about where the tip of the
tube lies, a flexible
bronchoscope may be
used to check the distal
position.
89. The tracheostomy tube
should be just large
enough to provide an
adequate airway for the
patient. Larger tubes can
only cause damage.
It must be remembered
that most women, even
when obese, have
tracheas smaller in
diameter than those of
men
Tracheostomy
91. Complications of tracheostomy
the anterior jugularanterior jugular
veinsveins may be
encountered as the
superficial fascia is
incised
They are avoided by
maintaining a midline
position
94. Complications of tracheostomy
The branches of the
superior and inferior
thyroid arteriesarteries may
anastomose acrossacross
the midlinethe midline
97. Complications of tracheostomy
In children the left
brachiocephalic vein
and the thymusthymus may
extend above the
suprasternal notch.
98. Complications of tracheostomy
The subclaviansubclavian arteryartery and veinvein may be
compromised by a tracheostomy to that is
incorrectly curved or is placed too low
Tube too curved Tube too low
99. Complications of tracheostomy
The existence of
fascial planes
predisposes to
surgicalsurgical
emphysemaemphysema,
particularly if the skin
is sutured too tightly.
Investing fascia
101. Complications of tracheostomy
Beware of over-
enthusiastic incision
into the trachea; the
esophagusesophagus is
immediately posterior.
trachea
esophagusesophagus
Thyroid & pretracheal fascia
Investing fascia
Skin & superficial fascia
