Untitled Quiz

Study Notes

Typical intercostal nerves (3rd-6th) enter the intercostal space between the parietal pleura and internal intercostal membrane.
They run forward inferior to the vessels in the costal groove between the internal intercostal and innermost intercostal muscles.
Branches of typical intercostal nerves include:
- Communicating branch: each intercostal nerve to the sympathetic trunk.
- Collateral branches: arise near the angle of the ribs and innervate the intercostal muscles.
- Lateral cutaneous branch: anterior cutaneous branch, muscular branch (intercostal, subcostal, transversus thoracis, levator costarum, serratus posterior m).

1st and 2nd intercostal nerves course on the internal surface of the 1st and 2nd ribs.
7th-11th intercostal nerves, after giving rise to the lateral cutaneous branch, cross the costal margin and supply the abdominal skin and muscles, becoming thoraco-abdominal nerves of the anterior abdominal wall.
1st intercostal nerve has no anterior cutaneous branch and often no lateral cutaneous branch.
Ventral ramus of the first thoracic spinal nerve has superior and inferior parts.

Posterior intercostal arteries: one in each of the 11 spaces, with the 1st and 2nd arising from the superior intercostal artery of the costocervical trunk of the 2nd part of the subclavian artery, and the lower 9 arteries and subcostal artery arising from the descending thoracic aorta.
Anterior intercostal arteries: the upper 6 from the internal thoracic artery, and the lower 3 from the musculophrenic artery.

Posterior intercostal veins: on the right side, 2nd-3rd (4th) posterior intercostal veins unite to form the right superior intercostal vein, which drains into the azygos vein, while on the left side, 2nd-3rd (4th) posterior intercostal veins unite to form the left superior intercostal vein, which drains into the left brachiocephalic vein.
Anterior intercostal veins: 9 pairs, with the 1st-6th anterior intercostal veins draining into the internal thoracic vein, and the 7th-9th anterior intercostal veins draining into the musculophrenic vein.

The thoracic wall is the part of the trunk that forms a narrow opening superiorly and a large opening inferiorly.
The thoracic skeleton forms the osteocartilaginous thoracic cage, consisting of the thoracic part of the vertebral column, the sternum, and costal cartilages.
The superior thoracic aperture (thoracic inlet) is bounded by the 1st thoracic vertebra posteriorly, a pair of 1st ribs and their costal cartilage, and the superior border of the manubrium anteriorly.
The inferior thoracic aperture (thoracic outlet) is bounded by the 12th thoracic vertebra, the 11th and 12th pairs of ribs, and the costal cartilages of ribs 7-10.

The intercostal space separates the ribs and contains three muscles of respiration (intercostal).
The internal surface of the thoracic wall is lined with the endothoracic fascia, which is lined with the parietal pleura internally.
The intercostal muscles occupy the intercostal space, with three layers: superficial (external intercostal), intermediate (internal intercostal), and deepest (transversus thoracis and innermost intercostal).

Podcast