The area of the neck immediately above the thoracic inlet is understood to be the root of the neck. Via this space the structures pass both into and out of the thoracic cavity.The thoracic inlet is a space bounded by 1st thoracic vertebra, 1st rib and manubrium sterni.
The clinical relevance of the area is the fact that the numerous essential structures, like carotid and subclavian arteries, the trachea and esophagus and large veins are all packed together into this comparatively small space consequently, any additional decline in this space may result in dreadful results the decrease in space might be caused by a number of clinical circumstances like tumor of apex of lung (pancoast tumor), enlarged thyroid gland, cervical rib, etc.
The cervical pleura, encloses the apex of the lung in the root of the neck. It originates into the root of the neck about 3.4 cm above the 1st costal cartilage but not above the neck of the first rib because of obliquity of the 1st rib. It increases 2.5 cm above the medial third of the clavicle.
- Subclavian artery.
- Scalenus anterior.
- Neck of first rib and structures crossing in front of it.
- Scalenus medius.
- Lower trunk of brachial plexus.
- Vertebral bodies.
- Trachea and esophagus.
- Recurrent laryngeal nerve in the tracheoesophageal groove.
- Thoracic duct on the left side.
- Large blood vessels of the neck.
- Structures crossing in front of the neck of 1st rib from medial to lateral side are:
- Sympathetic chain.
- First posterior intercostal vein.
- Superior intercostal artery.
- First thoracic nerve (large ascending branch of its ventral ramus).
Lymph Trunks at the Root of the Neck
The lymph from head and neck region is returned to the venous blood via right and left lymph trunks, which converge in the root of neck in the junction of internal jugular and subclavian veins. The different lymph trunks which converge on the left and right side of the root of the neck are as described in the subsequent text:
On the Right Side of Neck
Right jugular trunk extends along the ventrolateral aspect of the internal jugular vein. It drains lymph from right half of the head and neck.
Right subclavian trunk stretches along the axillary and subclavian veins and pulls lymph from the right upper limb and superficial tissues of the right half of the thoracoabdominal wall to the umbilicus anteriorly and iliac crest posteriorly.
Right bronchomediastinal trunk ascends over the trachea. It drains lymph from right lung, bronchi and trachea and right half of the mediastinum.
The right jugular and subclavian trunks may link to create right lymphatic duct, which finishes in a similar way to that of the thoracic duct.
On the Left Side
Left Jugular trunk drains lymph from left half of the head and neck. Its course and result is comparable to that on the right side.
Left subclavian trunk drains the lymph from the left upper limb and left half of thoracoabdominal wall in the exact same manner as that of right subclavian trunk.
Left bronchomediastinal trunk is comparable to that of the right trunk but empties more of the heart and esophagus.
Thoracic duct starts in the abdomen as an upward continuation of cisterna chyli at the lower border of the 12th thoracic vertebra. It enters the thoracic inlet along the left border of the esophagus. In the neck, it arches laterally at the level of the transverse process of the 7th cervical vertebra.
Its arch climbs 3 or 4 cm above the clavicle and curves anteriorly in front of the vertebral system (i.e., vertebral artery and vertebral vein) and left sympathetic trunk and behind the carotid system (i.e., left common carotid artery, left internal jugular vein and left vagus nerve). Ultimately, the duct descends in front of the arched (first part) subclavian artery and ends by opening into the junction of the left subclavian and internal jugular veins.
Relationships of the Thoracic Duct
The relationships of the thoracic duct arch in the neckare as follows:
- Left common carotid artery.
- Left vagus nerve.
- Left internal jugular vein.
- Vertebral artery and vein.
- Sympathetic trunk.
- Thyrocervical trunk and its branches.
- Prevertebral fascia.
- Phrenic nerve.
- Scalenus anterior muscle.
The thoracic duct is the longest and largest lymphatic trunk within the body. It empties the lymph from entire of the body with the exception of the right upper quadrant.
Tributaries in the Neck
Aside from the tributaries in the thorax and abdomen, the thoracic duct gets the subsequent tributaries in the neck:
- Left jugular trunk.
- Left subclavian trunk.
- Left bronchomediastinal trunk.
Recurrent Laryngeal Nerve
It runs on either side in the tracheo-esophageal groove.
Trachea and Esophagus
The trachea stretches from the lower border of the cricoid cartilage in the level of the lower border of C6 vertebra to the level of sternal angle in the level of lower border of T4. It can be palpated in the midline just above the jugular notch. This part of trachea is crossed by the isthmus of thyroid gland, inferior thyroid veins, the thyroidea ima artery (if present) and jugular venous arch.
The esophagus starts in the neck just below the cricopharyngeus at the lower border of C6 vertebra. It is located on longus colli behind the trachea. The thoracic duct is located on its left lateral border before arching over the triangle of the vertebral artery on the left side.
These veins collect blood from the head and neck, upper limbs, thoracic wall and anterior abdominal wall. Every vein is composed by the union of corresponding internal jugular and subclavian veins behind the medial end of the clavicle. They finish by joining to create superior vena cava behind the lower border of the right first costal cartilage in the margin of the sternum.
The right brachiocephalic vein descends just about vertically. In the neck, it is located on the cervical pleura lateral to the brachiocephalic trunk. The phrenic nerve and internal thoracic artery is located posterior to it on the other hand anterior to it be located sternohyoid and sternothyroid muscles.
The left brachiocephalic vein runs obliquely to pass behind the upper part of the manubrium sterni to join the right brachiocephalic vein and is for that reason considerably longer.
Both veins get the vertebral, greatest intercostal and inferior thyroid veins. The right lymphatic duct, right jugular trunk and right subclavian trunk go into the right vein. The thoracic duct and left superior intercostal vein goes into the left vein.