Superior thoracic aperture
Encyclopedia
The superior thoracic aperture refers to the superior opening of the thoracic cavity. It is also referred to anatomically as the thoracic inlet and clinically as the thoracic outlet. The clinical entity called the Thoracic outlet syndrome
refers to the superior thoracic aperture, not the inferior thoracic aperture
.
The superior thoracic aperture is bounded by: the first thoracic vertebra (T1
) posteriorly, the first pair of rib
s laterally (more specifically, the first ribs form lateral C-shaped curves posterior to anterior), the costal cartilage of the first rib and the superior border of the manubrium
anteriorly.
articulates with the manubrium
to form the anterior border of the thoracic inlet.
Superior to the thoracic inlet is the root of the neck
, and the superior mediastinum
is related inferiorly.
The brachial plexus
is a superolateral relation of the thoracic inlet. The brachial plexus emerges between the anterior and middle scalene muscles
, superior to the first rib, and passes obliquely and inferiorly, underneath the clavicle, into the shoulder and then the arm. Impingement of the plexus
in the region of the scalenes, ribs, and clavicles is responsible for thoracic outlet syndrome
.
This is not an exhaustive list. There are several other minor but important vessels and nerves passing through, and an abnormally large thyroid gland may extend inferiorly through the thoracic inlet into the superior mediastinum
.
The oesophagus lies against the body of the T1 vertebra, separated from it by the prevertebral fascia
, and the trachea lies in front of the oesophagus, in the midline, and may touch the manubrium. The apices of the lungs lie to either side of the oesophagus and trachea, and is separated from them by the other vessels and nerves listed above. Furthermore, they extend slightly superior past the level of the inlet (e.g. the horizontal plane of the first rib).
Thoracic outlet syndrome
Thoracic outlet syndrome is a syndrome involving compression at the superior thoracic outlet involving compression of a neurovascular bundle passing between the anterior scalene and middle scalene...
refers to the superior thoracic aperture, not the inferior thoracic aperture
Inferior thoracic aperture
-Anatomy:The inferior thoracic aperture is much larger than the superior thoracic aperture. In layman's terms, it is the round opening whose edges are the lowest ribs...
.
Boundaries
The thoracic inlet is essentially a hole surrounded by a bony ring, through which several vital structures pass.The superior thoracic aperture is bounded by: the first thoracic vertebra (T1
Thoracic vertebrae
In human anatomy, twelve thoracic vertebrae compose the middle segment of the vertebral column, between the cervical vertebrae and the lumbar vertebrae. They are intermediate in size between those of the cervical and lumbar regions; they increase in size as one proceeds down the spine, the upper...
) posteriorly, the first pair of rib
Rib
In vertebrate anatomy, ribs are the long curved bones which form the rib cage. In most vertebrates, ribs surround the chest, enabling the lungs to expand and thus facilitate breathing by expanding the chest cavity. They serve to protect the lungs, heart, and other internal organs of the thorax...
s laterally (more specifically, the first ribs form lateral C-shaped curves posterior to anterior), the costal cartilage of the first rib and the superior border of the manubrium
Manubrium
The manubrium or manubrium sterni is the broad, upper part of the sternum. Located ventrally with a quadrangular shape, wider superiorly and narrower inferiorly, it articulates with the clavicles and the first two ribs.-Borders:The superior border is the thickest and presents at its center the...
anteriorly.
Relations
The clavicleClavicle
In human anatomy, the clavicle or collar bone is a long bone of short length that serves as a strut between the scapula and the sternum. It is the only long bone in body that lies horizontally...
articulates with the manubrium
Manubrium
The manubrium or manubrium sterni is the broad, upper part of the sternum. Located ventrally with a quadrangular shape, wider superiorly and narrower inferiorly, it articulates with the clavicles and the first two ribs.-Borders:The superior border is the thickest and presents at its center the...
to form the anterior border of the thoracic inlet.
Superior to the thoracic inlet is the root of the neck
Neck
The neck is the part of the body, on many terrestrial or secondarily aquatic vertebrates, that distinguishes the head from the torso or trunk. The adjective signifying "of the neck" is cervical .-Boner anatomy: The cervical spine:The cervical portion of the human spine comprises seven boney...
, and the superior mediastinum
Mediastinum
The mediastinum is a non-delineated group of structures in the thorax, surrounded by loose connective tissue. It is the central compartment of the thoracic cavity...
is related inferiorly.
The brachial plexus
Brachial plexus
The brachial plexus is a network of nerve fibers, running from the spine, formed by the ventral rami of the lower four cervical and first thoracic nerve roots...
is a superolateral relation of the thoracic inlet. The brachial plexus emerges between the anterior and middle scalene muscles
Scalene muscles
The scalene muscles are a group of three pairs of muscles in the lateral neck, namely the scalenus anterior, scalenus medius, and scalenus posterior.They are innervated by the spinal nerves C4-C6....
, superior to the first rib, and passes obliquely and inferiorly, underneath the clavicle, into the shoulder and then the arm. Impingement of the plexus
Plexus
A plexus is a part of nervous system. Plexus has a slightly different definition in vertebrates and in invertebrates.- In vertebrates :In vertebrates, a plexus is an area where nerves branch and rejoin. The electrical signals do not mix; rather, the fibres travel together with their electrical...
in the region of the scalenes, ribs, and clavicles is responsible for thoracic outlet syndrome
Thoracic outlet syndrome
Thoracic outlet syndrome is a syndrome involving compression at the superior thoracic outlet involving compression of a neurovascular bundle passing between the anterior scalene and middle scalene...
.
Contents
Structures that pass through the superior thoracic aperture include:- tracheaVertebrate tracheaIn tetrapod anatomy the trachea, or windpipe, is a tube that connects the pharynx or larynx to the lungs, allowing the passage of air. It is lined with pseudostratified ciliated columnar epithelium cells with goblet cells that produce mucus...
- oesophagus
- thoracic ductThoracic ductIn human anatomy, the thoracic duct of the lymphatic system is the largest lymphatic vessel in the body. It is also known as the left lymphatic duct, alimentary duct, chyliferous duct, and Van Hoorne's canal....
- apexes of the lungs
- nerves
- phrenic nervePhrenic nerveThe phrenic nerve originates mainly from the 4th cervical nerve, but also receives contributions from the 5th and 3rd cervical nerves in humans....
- vagus nerveVagus nerveThe vagus nerve , also called pneumogastric nerve or cranial nerve X, is the tenth of twelve paired cranial nerves...
- Recurrent laryngeal nerveRecurrent laryngeal nerveThe recurrent laryngeal nerve is a branch of the vagus nerve that supplies motor function and sensation to the larynx . It travels within the endoneurium...
s - sympathetic trunkSympathetic trunkThe sympathetic trunks are a paired bundle of nerve fibers that run from the base of the skull to the coccyx.-Structure:...
s
- phrenic nerve
- vessels
- arteries
- left and right common carotid arteries
- left and right subclavian arteries
- veins
- internal jugular veinInternal jugular veinThe two internal jugular veins collect the blood from the brain, the superficial parts of the face, and the neck.-Path:On both sides and at the base of the brain, the inferior petrosal sinus and the sigmoid sinus join to form the internal jugular vein...
s - brachiocephalic veinBrachiocephalic veinThe left and right brachiocephalic veins in the upper chest are formed by the union of each corresponding internal jugular vein and subclavian vein...
s - subclavian veinSubclavian veinThe subclavian veins are two large veins, one on either side of the body. Their diameter is approximately that of the smallest finger.-Path:Each subclavian vein is a continuation of the axillary vein and runs from the outer border of the first rib to the medial border of anterior scalene muscle...
s
- internal jugular vein
- arteries
- lymph nodeLymph nodeA lymph node is a small ball or an oval-shaped organ of the immune system, distributed widely throughout the body including the armpit and stomach/gut and linked by lymphatic vessels. Lymph nodes are garrisons of B, T, and other immune cells. Lymph nodes are found all through the body, and act as...
s and lymphatic vessels
This is not an exhaustive list. There are several other minor but important vessels and nerves passing through, and an abnormally large thyroid gland may extend inferiorly through the thoracic inlet into the superior mediastinum
Mediastinum
The mediastinum is a non-delineated group of structures in the thorax, surrounded by loose connective tissue. It is the central compartment of the thoracic cavity...
.
The oesophagus lies against the body of the T1 vertebra, separated from it by the prevertebral fascia
Prevertebral fascia
The prevertebral fascia is a fascia in the neck.-Variations:In some literature, the prevertebral fascia also includes the rest of the fascia extending around the vertebral column and enclosing all muscles laterally and posteriorly to it...
, and the trachea lies in front of the oesophagus, in the midline, and may touch the manubrium. The apices of the lungs lie to either side of the oesophagus and trachea, and is separated from them by the other vessels and nerves listed above. Furthermore, they extend slightly superior past the level of the inlet (e.g. the horizontal plane of the first rib).