Download File

Thymus, Trachea & Oesophagus
Thorax Unit
Lecture 9 & 10
‫ حيدر جليل األعسم‬.‫د‬
Thymus
It is a pink, flattened, bi-lobed structure lying between sternum and
pericardium in anterior mediastinum. In newborn infants, it reaches its
largest size relative to size of body & may extend up through superior
mediastinum in front of great vessels into root of the neck.
Blood Supply of thymus is from inferior thyroid
and internal thoracic arteries.
Trachea
Trachea is a mobile cartilaginous & membranous tube. It is 11 cm long
and 2.5 cm in diameter. Tube is kept patent by presence of U-shaped
bars (rings) of hyaline cartilage embedded in its wall. Posterior free ends
of cartilage are connected by smooth muscle,
trachealis muscle. It begins in neck as a continuation
of larynx at lower border of cricoid cartilage at
level of 6th cervical vertebra. In thorax, trachea
ends below at carina by dividing into right & left
principal (main) bronchi at level of sternal angle.
Blood Supply of Trachea
Upper 2/3 by inferior thyroid arteries &
Lower 1/3 is supplied by bronchial arteries.
Lymph Drainage of Trachea: into pretracheal &
paratracheal lymph nodes & deep cervical nodes.
Nerve Supply of Trachea: is from vagi & recurrent
laryngeal nerves. Sympathetic nerves supply
trachealis muscle.
Trachea
Relations of Trachea:
Anteriorly: sternum, thymus, left brachiocephalic vein, origins of
brachiocephalic & left common carotid arteries, & arch of aorta
Posteriorly: esophagus & left recurrent laryngeal nerve.
Right side: azygos vein, right vagus nerve, and pleura
Left side: aortic arch, left common carotid & left
subclavian arteries, left vagus & left phrenic nerves
& pleura.
Bronchi
Trachea bifurcates behind arch of aorta into right & left principal
(primary or main) bronchi.
Right principal (main) bronchus is wider,
shorter, and more vertical than left.
Before entering hilum of right lung, it gives
off superior lobar bronchus.
On entering hilum, it divides into middle
and inferior lobar bronchus.
Left principal (main) bronchus is narrower,
longer, and more horizontal than right. It passes
to left below arch of aorta & in front of esophagus.
On entering hilum of left lung, principal
bronchus divides into a superior & an
inferior lobar bronchus
Esophagus
It is a tubular structure about 10 in. (25 cm) long that is continuous
above with pharynx & passes through diaphragm at level of 10th
thoracic vertebra to join stomach.
In neck, it lies in front of vertebral column
In thorax, it passes downward & to left
through superior & then posterior mediastinum.
At level of sternal angle, aortic arch pushes
esophagus over to midline.
In abdomen, It descends for about 0.5 inch
(1.3 cm) & then enters the stomach.
Relations of thoracic part of esophagus
Anteriorly: Trachea and left recurrent laryngeal nerve; left principal
bronchus, which constricts it; and pericardium, which separates
esophagus from left atrium.
Posteriorly: Bodies of thoracic vertebrae; thoracic
duct; azygos veins; right posterior intercostal arteries;
and, at its lower end, descending thoracic aorta.
Right side: Mediastinal pleura and terminal part of
azygos vein
Left side: Left subclavian artery, aortic arch, thoracic
duct, and mediastinal pleura.
Inferiorly to level of roots of lungs, vagus
nerves leave pulmonary plexus and join with
sympathetic nerves to form esophageal plexus.
Left vagus lies anterior to esophagus and right
vagus lies posterior.
Esophagus
Blood Supply of Esophagus
Upper 1/3: by inferior thyroid artery
Middle 1/3: by branches from descending thoracic aorta
Lower 1/3: by branches from left gastric artery.
Veins of upper 1/3 drain into inferior thyroid veins,
from middle 1/3 into azygos veins, and from
lower 1/3 into left gastric vein.
Lymph Drainage of Esophagus
Upper 1/3 of esophagus drain into deep cervical nodes,
Middle 1/3 into mediastinal nodes,
Lower 1/3 into nodes along left gastric blood vessels &
celiac nodes.
Nerve Supply of Esophagus
Esophagus is supplied by parasympathetic & sympathetic
efferent and afferent fibers via vagi & sympathetic trunks.
In lower part of its thoracic course, esophagus is surrounded by
esophageal nerve plexus.
Internal Thoracic Artery
It supplies anterior wall of body from clavicle to umbilicus. It is a branch
of first part of subclavian artery. It descends vertically on pleura behind
costal cartilages, one fingerbreadth lateral to sternum, and ends in 6th
intercostal space by dividing into
superior epigastric artery
musculophrenic arteries.
Internal Thoracic Artery
Branches
1. Two anterior intercostal arteries for upper six intercostal spaces
2. Pericardiophrenic artery
accompanies phrenic nerve & supplies
Pericardium.
3. Mediastinal arteries supply contents
of anterior mediastinum (Thymus)
4. Superior epigastric artery, enters
rectus sheath of anterior
abdominal wall & supplies
rectus muscle as far as umbilicus
5. Musculophrenic artery, runs
around costal margin of diaphragm
& supplies lower intercostal
spaces & diaphragm
Internal Thoracic Vein: accompanies
internal thoracic artery and drains into
brachiocephalic vein on each side.