Download Lobes of thyroid gland and carotid sheath (with its contents).

VISCERA
OF
THE NECK
THYROID
GLAND
OBJECTIVES
Definition.
Position.
Shape.
Surfaces and borders.
Isthmus.
Relations.
Blood and lymphatic drainage.
Clinical points.
Thyroid
Gland
It is a highly vascular endocrine gland
situated in the front of the neck.
It is formed of two bear-shaped lobes
connected by median isthmus.
It is enclosed with the larynx and trachea by
the pretracheal fascia so it moves with them
during swallowing.
Its apex extends upward to the oblique line
of the thyroid cartilage, and its base reaches
down to the 4-5 tracheal ring.
It isthmus extends across the midline in
front of the 2nd, 3rd and 4th tracheal rings.
A pyramidal lobe may be present.
Relations
Anterolateral (superficial):
– Skin, superficial fascia containing platysma,
transverse cervical nerve & anterior jugular
vein, investing deep fascia, sternomastoid,
sternohyoid and omohyoid (enclosed in
pretracheal fascia).
Posterolateral (posterior):
– Carotid sheath containing common carotid
artery, internal jugular vein and vagus nerve.
Medial:
– Larynx, pharynx, cricothyroid muscle and
external laryngeal nerve (above).
– Tracheal, esophagus and recurrent laryngeal
nerve (below).
Blood supply and lymph drainage
Arterial blood supply:
1. Superior thyroid artery from external carotid artery.
2. Inferior thyroid artery from thyrocervical trunk from
1st part of subclavian artery.
3. Thyroidea ima artery from brachiocephalic or arch
of aorta.
Venous drainage:
1. Superior thyroid vein to internal jugular vein.
2. Middle thyroid vein to internal jugular vein.
3. Inferior thyroid veins to left brachiocephalic vein.
Lymph drainage:
1. Deep cervical lymph nodes.
2. Paratracheal lymph nodes.
Clinical points of thyroid gland
Movement of the gland:
– The gland moves upward during deglutition
(swallowing) because it is enclosed within the
pretracheal fascia.
Goitre:
– Means enlargement of the size of the gland.
– It can not extend upward, but it can extend downward
and may be retrosternal.
– It may compress the trachea.
Thyroidectomy:
– Means surgical removal of the thyroid gland.
– Because the close relationship between the gland and
the laryngeal nerves (external and recurrent), they may
be damaged during the operation.
– Parathyroid gland may be also removed in total
thyroidectomy operations.
Trachea
It is a mobile cartilaginous and
membranous respiratory tube.
It begins at the lower border of cricoid
cartilage (at the level of the 6th cervical
vertebra) as a continuation of the
larynx.
It ends at the sternal angle (between 4th
and 5th thoracic vertebrae) by dividing
into right and left main bronchi.
Relations of Trachea
Anterior:
– Skin, superficial fascia, investing deep
fascia, pretracheal fascia, isthmus of thyroid
gland, jugular arch, thyroidea ima artery,
sternothyroid and sternohyoid muscles.
Posterior:
– Right and left recurrent laryngeal nerves,
esophagus and vertebral column.
Lateral:
– Lobes of thyroid gland and carotid sheath
(with its contents).
Esophagus
It is a muscular tube (10 inches long).
It begins at the lower border of cricoid
cartilage (at the level of the 6th cervical
vertebra) as a continuation of the
pharynx.
It ends in the abdomen by opening into
the stomach.
At its beginning, it lies in the midline
but as it descends in the neck, it
inclines to the left side.
Relations of Esophagus
Anterior:
– Trachea and recurrent laryngeal nerves.
Posterior:
– Prevertebral fascia, longus coli and
vertebral column.
Lateral:
– Lobes of thyroid gland and carotid
sheath (with its contents).
Arterial supply in the neck:
–Branches from inferior
thyroid artery.
Lymph drainage in the neck:
–Deep cervical lymph nodes.
Nerve supply in the neck:
–From recurrent laryngeal and
sympathetic trunk.