 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 2 nd 3 rd & 4 th 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 4 th or 5 th 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 5 th tracheal ring. The isthmus extends across the midline in front of the 2 nd 3 rd & 4 th 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:  Sternothyroid.  Superior belly of Omohyoid  Sternohyoid.  Sternomastoid.  Posterolaterally:  Carotid sheath & its contents.  Medially:  Above:  Larynx & pharynx.  Below:  Trachea & esophagus.  Recurrent laryngeal nerve in between.  Cricothyroid muscle & external laryngeal nerve.

 Relation of the isthmus  Anteriorly:  sternothyroid, sternohyoid,  anterior jugular vein, fascia & skin.  Posteriorly:  2 nd,3 rd,&4 th tracheal rings. thyroid arteries  Terminal branches of the 2 superior thyroid arteries 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 1 st 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 jugular 3- 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 7 th 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 superior & inferior thyroid arteries.  Their veins are drained to superior, middle and inferior thyroid veins.  Lymph nodes:  Deep cervical & paratracheal lymph nodes.  Nerve supply:  Superior & middle cervical 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. ..

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

19 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.  Blood:  Inferior thyroid artery.  Lymph:  deep cervical lymph nodes.  Nerves: Recurrent laryngeal and sympathetic trunk.