Vessels and nerves of the thoracic wall

Definitions & Key takeaways

The thoracic wall contains various blood vessels and nerves that supply the muscles, bones, and skin of the region.

The arterial supply to the thoracic wall comes from the posterior intercostal and subcostal arteries arising from the thoracic aorta; the internal thoracic and superior intercostal artery, and the superior and lateral thoracic arteries from the axillary artery. The veins of the thoracic wall are the intercostal veins that accompany the intercostal arteries and nerves, and drain into the brachiocephalic vein

The nerves of the thoracic wall include the intercostal nerves, which run between the ribs and supply the muscles and skin of the chest wall. 12 pairs of thoracic spinal nerves divide into posterior rami as well as anterior rami, which continue as the intercostal nerves.

Chapters:

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Introduction0:00–0:18

There are numerous vessels and nerves that course throughout the bony and muscular architecture of the thoracic wall, and they provide innervation and blood supply to the structures within and around the thoracic cage.
First, let’s have a look at the contents of the intercostal space, specifically the neurovascular bundle containing the intercostal nerve, artery and vein.

Thoracic neurovascular bundle0:18–1:03

It is important to remember the order of these structures, with the most superior structure being the intercostal vein and below it comes the artery and below the artery, the nerve.
To easily remember this, think V-A-N or think about a VAN that’s blue at the top, red in the middle and yellow in the inferior part.
The inferior portion of the ribs also have a costal groove which only provides partial protection for these structures, so they can be damaged during penetrating intercostal injuries or any intervention that requires intercostal access Now, let’s talk about the nerves.

Thoracic spinal nerves1:03–4:34

There are 12 pairs of thoracic spinal nerves which supply the thoracic wall. They leave the intervertebral foramina as soon as they are formed, dividing into anterior and posterior rami.
Now, the anterior rami of nerves T1 through T11 form the intercostal nerves that run along the intercostal spaces along the inferior borders of the ribs, with the third intercostal nerve travelling between the third and fourth ribs.
The anterior ramus of nerve T12 that courses inferior to the 12th rib is the subcostal nerve. The intercostal nerves give anterior and lateral cutaneous branches to innervate the thorax and abdominal wall, muscular branches to supply the muscles of the thoracic wall, and they give rami communicantes or communicating branches that connect the intercostal nerves to a sympathetic trunk on the same side.
The posterior rami of thoracic spinal nerves pass posteriorly, lateral to the articular processes of the vertebrae in order to supply the joints, deep back muscles and skin of the posterior thoracic region.
Now, the intercostal nerves are either typical or atypical, and the typical ones are the 3rd through the 6th pair. These nerves enter the medial-most parts of the posterior intercostal spaces.
Initially, they run within the endothoracic fascia just between the parietal pleura and the internal intercostal membrane.
Near the angles of the ribs, these nerves pass between the internal intercostal and the innermost intercostal muscles. From here, they continue to course in or inferior to the costal grooves, running inferior to the intercostal arteries.
Keep in mind that the arteries run inferior to the intercostal veins. Near the angles of the ribs, collateral branches arise and run along the superior border of the rib below.
The nerves continue anteriorly between the internal and innermost intercostals and supply these muscles and other muscles and also give rise to lateral cutaneous branches in the midaxillary line.
Anteriorly, the nerves appear on the internal surface of the internal intercostal muscle. Near the sternum, these nerves turn anteriorly and pass between the costal cartilages to become anterior cutaneous branches.
Atypical intercostals are the first 2 intercostal nerves which run on the internal surface of the 1st and 2nd ribs, not along the inferior margin in the costal groove, and the 7th through 11th nerves which eventually become thoracoabdomial nerves of the anterior abdominal wall.
Most thoracic spinal nerves, specifically T2 through T12, give rise to the dermatomal map of the trunk through their posterior ramus and the lateral and anterior cutaneous branches of its anterior ramus.
This dermatomal map extends from the posterior median line to the anterior median line and it represents the area of skin supplied by the spinal nerves.
Exact dermatomal distributions may vary depending on the source, however they are generally agreed upon with certain dermatomes acting as key landmarks.
For example, dermatome T4 includes the nipple, and T10 includes the umbilicus. Almost there.

Quiz4:34–4:48

Let’s see if you can identify the typical intercostal nerves in this picture. Alright, finally, let’s look at the arterial supply to the thoracic wall, which comes from the posterior intercostal and subcostal arteries arising from the thoracic aorta, the internal thoracic, or mammary, artery coming from the subclavian artery, and the supreme, or superior, intercostal artery arising from the costocervical trunk of the subclavian artery, and the superior and lateral thoracic arteries from the axillary artery.

Arterial supply4:48–5:31

With the exception of intercostal space 10 and 11, each intercostal space is supplied by a large posterior intercostal artery, and a small pair of anterior intercostal arteries.

Posterior intercostal arteries5:31–6:58

The posterior intercostal arteries of the 1st and 2nd intercostal spaces arise from the supreme or superior intercostal artery which is a branch of the costocervical trunk of the subclavian artery.
The posterior intercostal arteries of the 3rd through the 11th intercostal spaces arise posteriorly from the thoracic aorta.
All posterior intercostal arteries give rise to a dorsal branch that accompanies the posterior ramus of the spinal nerve to supply the spinal cord, vertebral column, back muscles and skin.
They also give rise to a small collateral branch that crosses the intercostal space and runs along the superior border of the rib below.
The posterior intercostal arteries accompany the intercostal nerves through the intercostal spaces. Close to the angle of the rib, the arteries enter the costal grooves, where they lie between the intercostal vein and nerve.
At first, the arteries run in the endothoracic fascia between the parietal pleura and the internal intercostal membrane and then they run between the innermost intercostal and internal intercostal muscles.
They have terminal and collateral branches that anastomose anteriorly with anterior intercostal arteries. Now, the ipsilateral pairs of anterior intercostal arteries supply the anterior parts of the upper 9 intercostal spaces.

Anterior intercostal arteries6:58–7:48

They pass laterally in the intercostal space, one near the inferior margin of the superior rib and the other near the superior margin of the inferior rib.
In the first 2 intercostal spaces they lie initially in the endothoracic fascia between the parietal pleura and the internal intercostal muscles.
They supply the intercostal muscles and send branches through them to supply the pectoral muscles, breast and skin. They’re missing from the inferior two intercostal spaces, because these spaces are supplied only by the posterior intercostal arteries and their collateral branches.

Internal thoracic arteries7:48–8:41

Then there are the internal thoracic arteries, previously called the internal mammary arteries, arise in the root of the neck from the inferior surfaces of the first parts of the subclavian arteries.
Then they descend into the thorax posterior to the clavicle and 1st costal cartilage. Then they descend on the internal surface of the thorax lateral to the sternum and posterior to the upper six costal cartilages and internal intercostal muscles.
After going down past the 2nd costal cartilage, the internal thoracic arteries run anterior to the transversus thoracis muscle.
They terminate in the 6th intercostal space by dividing into the superior epigastric and the musculophrenic arteries. They also directly give rise to the anterior intercostal arteries that supply the superior 6 intercostal spaces.
There is also the subcostal artery which is a branch of the thoracic aorta. It courses along the inferior border of the 12th rib, and provides blood supply to muscles of the anterolateral abdominal wall.

Subcostal artery8:41–8:56

Last, but not least, let’s have a quick look at the veins of the thoracic wall. The intercostal veins accompany the intercostal arteries and nerves and lie most superior in the costal grooves.

Venous drainage8:56–10:35

There are 11 posterior intercostal veins and one subcostal vein on each side. The posterior intercostal veins anastomose with the anterior intercostal veins, which are tributaries of the internal thoracic veins.
As they get close to the vertebral column, the posterior intercostal veins receive a posterior branch, which accompanies the posterior ramus of the spinal nerve of that level, and an intervertebral vein that drains the vertebral venous plexuses of the vertebral column.
Now, most posterior intercostal veins, specifically those who drain the 4th through the 11th intercostal space, end in the azygos or hemi-azygos vein system.
The azygos system conveys venous blood to the superior vena cava. The posterior intercostal veins of the 1st intercostal space enter directly into the right and left brachiocephalic vein.
The posterior intercostal veins of the 2nd and 3rd and sometimes 4th intercostal spaces join to form a trunk called the superior intercostal vein.
The right superior intercostal vein is usually the final tributary of the azygos vein, before it enters the superior vena cava.
The left superior intercostal vein usually empties into the left brachiocephalic vein. The internal thoracic veins are the companion veins of the internal thoracic arteries.And one last quiz before the recap - can you label the arteries in this picture?

Quiz10:35–10:46

##SummaryAll right, as a quick recap, The contents of the intercostal space can be easily remembered as VAN, meaning the most superior is the intercostal vein, below it comes the artery and below the artery, the nerve.

Review10:46–12:21

There are 12 pairs of thoracic spinal nerves that divide into a posterior rami as well as anterior rami that continues as the intercostal nerve.
The cutaneous branches of the T2 through T12 thoracic spinal nerves supply the dermatomes of the trunk that extends from the posterior median line to the anterior median line.
The arterial supply to the thoracic wall comes from the posterior intercostal and subcostal arteries arising from the thoracic aorta, the internal thoracic and superior intercostal artery, and the superior and lateral thoracic arteries from the axillary artery.
The veins of the thoracic wall are the intercostal veins that accompany the intercostal arteries and nerves and they mostly drain into the azygos system.
The posterior intercostal veins of the 1st intercostal space enter directly into the right and left brachiocephalic vein.
The posterior intercostal veins of the 2nd and 3rd and sometimes 4th intercostal spaces join to form a trunk called the superior intercostal vein.
of the 2nd and 3rd and sometimes fourth intercostal spaces join to form a trunk called