Thyroid Gland

Parathyroid Trachea Esophagus By Prof . Saeed Abuel Makarem

The deep cervical fascia of the neck is divided into 3 layers:

1- Investing layer.

2- Pretracheal layer.

3- Prevertebral layer.

Endocrine gland. Consists of right & left

lobes. The 2 lobes are

connected to each other by a narrow isthmus, which overlies the 2nd 3rd & 4th rings of the trache.

It is surrounded by a sheath derived from the pretracheal layer of cervical fascia.

Thyroid gland

Each lobe is pear shaped, with its apex reaches up to the oblique line of the thyroid cartilage.

Its base lies at the level of 4th or 5th tracheal rings.

Inside the pretracheal facial capsule, there is another capsule.

Each lobe is pear shaped, with its apex directed upward as for as the oblique line of the thyroid cartilage; its base is at the 4th or 5th tracheal ring.

The isthmus extends across the midline in front of the 2nd 3rd & 4th tracheal rings.

A small pyramidal lobe is often present which projects from the upper border of the isthmus usually to left of middle line.

Pyramidal lobe is connected to hyoid bone by a fibrous or muscular band called levator glandulae thyroideae.

This represents the fibrosed & obliterated thyroglossal duct.

Anterolaterally: Anterolaterally: Sternothyroid.Sternothyroid. Superior belly of Superior belly of

OmohyoidOmohyoid Sternohyoid.Sternohyoid. Sternomastoid.Sternomastoid. Posterolaterally:Posterolaterally: Carotid sheath & its Carotid sheath & its

contents.contents. MediallyMedially: : AboveAbove:: Larynx & pharynx .Larynx & pharynx . Below:Below: Trachea & esophagus.Trachea & esophagus. Recurrent laryngeal Recurrent laryngeal

nerve in betweennerve in between.. Cricothyroid muscle & Cricothyroid muscle &

external laryngeal external laryngeal nerve.nerve.

Relation of the isthmus

Anteriorly: sternothyroid,

sternohyoid, anterior jugular vein,

fascia & skin. Posteriorly: 2nd,3rd,&4th tracheal

rings. Terminal branches of

the 2 superior thyroid thyroid arteriesarteries which anastomosis along the upper border.

The rounded posterior border is related to the superior & inferior Parathyroid glands.

It is also related to the anastomosis between superior & inferior thyroid arteries.

:

Superior thyroid artery

From external carotid artery It descends to the upper pole of the lobe, with the external

laryngeal nerve. It runs along the upper border of

the isthmus to anastomosis with its fellow.

Thyroidea ima artery

If present, it arises from aortic arch or from brachiocephalic artery.

It ascends in front of trachea to reach isthmus.

Inferior thyroid artery

From thyrocervical trunk of 1st part of subclavian artery, ascends behind the gland to the level of cricoid cartilage.

Then it turns medially behind the carotid sheath.

The it reaches the posterior border of the gland & descends downwards.

The recurrent laryngeal nerve crosses either in front or behind the artery.

1- Superior thyroid vein internal jugular 2- Middle thyroid vein internal jugular3- Inferior thyroid vein left brachiocephalic

Veins of Thyroid Gland

Lymph Of the Thyroid Gland:

Deep cervical & paratracheal

Goiter

GOITER A non-neoplastic & non-inflammatory enlargement of the thyroid gland.

The thyroid glands develops high up close to foramen cecum of the developing tongue.

Then it descends along the thyroglossal duct to reach its final position by the 7th week.

Descent of the thyroid could be arrested at any point, or extends down to thorax.

Parathyroid glands Four small ovoid bodies,

about 6mm. Long. They lie within the facial

capsule of the gland. 2 superior parathyroid

has a constant position at the middle of posterior border of the gland.

2 inferior parathyroid usually at the level of the inferior pole.

They lie within the thyroid tissue or sometimes outside the facial capsule.

They are supplied by They are supplied by superior & inferior thyroid superior & inferior thyroid arteries.arteries.

Their veins are drained to Their veins are drained to superior, middle and superior, middle and inferior thyroid veinsinferior thyroid veins..

Lymph nodes:Lymph nodes: Deep cervical & Deep cervical &

paratracheal lymph nodes.paratracheal lymph nodes. Nerve supplyNerve supply:: Superior & middle cervical Superior & middle cervical

sympathetic ganglia.sympathetic ganglia.

10 to 15 cm long mobile tube.

Formed of cartilage & membrane.

Its diameter is about 2 cm in adult male.

It begins at lower border of cricoid cartilage (C 6).

It descends in the midline of the neck.

It ends at the level of the disc between T4 & T5.

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The trachea has a fibro -elastic wall which is supported by series of U-shaped bars of hyaline cartilage that keep the lumen patent.

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The posterior free ends of the cartilage are connected by smooth muscle, called the trachealis muscle.

Anteriorly: Skin, Superficial fascia,

investing cervical fascia

isthmus of thyroid gland,

Inferior thyroid veins jugular arch, thyroidea ima artery, left brachiocephalic

vein, sternothyroid &

sternohyoid

Posteriorly esophagus, recurrent laryngeal nerves (in between trachea and

esophagus) vertebral column. Laterally: Lobes of the thyroid gland

& carotid sheath. Blood supply: Inferior thyroid artery. Nerve : vagi, sympathetic trunk &

recurrent laryngeal Lymph: Pretracheal & Para

tracheal lymph nodes.

Muscular tube 25 cm or 10 inches long.

Extends from pharynx to stomach.

It begins at lower border of cricoid cartilage (C 6).

It begins in midline, but inclines to the left.

It descends in superior then posterior mediastinum of thorax.

Anteriorly trachea and recurrent

laryngeal nerves.

Posteriorly Prevertebral layer of

cervical fascia, longus coli muscle & vertebral column. Laterally: Lobe of thyroid gland, carotid sheath. Thoracic duct on left

side. BloodBlood: : Inferior thyroid artery. Lymph: deep cervical lymph nodes. Nerves: Recurrent

laryngeal and sympathetic trunk.