Anterior Thoracic Wall Flashcards
Name the muscles of the thoracic wall that anchor to the thoracic cage to act as accessory muscles of respiration.
The serratus posterior superior, serratus posterior inferior and the levator costarum.
What is the function of the serratus posterior superior and inferior?
The serratus posterior superior elevates the upper 4 ribs to increase thoracic volume. The serratus posterior inferior pulls down on the ribs preventing the diaphragm from pulling them up. This allows the diaphragm to effectively increase the thoracic volume as well.
List the remaining muscles that are found within the intercostal space - from superficial
to deep.
External intercostal, internal intercostal, and the 3rd layer composed of - from front to back: transversus thoracis, innermost intercostals, and subcostals.
Be able to label a diagram of a cross-section through the thorax showing you under- stand the arrangement of the 3 layers of intercostal muscles that form the thoracic wall.
The diagram on page 136 is critical to your understanding of the muscle layers and how they in turn become membranous, as well as the nerve and blood supply to the thoracic wall (intercostal space).
In which direction do the fibers of each of the layers extend?
External intercostals are directed inferior and medially (hands-in-pockets); internal intercostals go upward and medially (opposite to the externals), and the innermost intercostals are oriented in a similar direction to the internals.
Where does each fade into membranous attachments?
External intercostals become membranous anteriorly, internal intercostals become membranous posteriorly , and the muscles of the 3rd layer (transversus thoracis, innermost intercostals, and subcostals) are linked to one another by intervening membranes.
Where does the intercostal neurovascular bundle run between them.
Between the internal and innermost intercostal layers.
What are the 3 muscle groups that, when linked by a membrane, form the deepest layer of the intercostal mm.?
The transversus thoracis, innermost intercostals, and subcostals.
From what vessel do the posterior intercostal aa. arise?
The aorta
From which vessel do their anterior counterparts arise?
The internal thoracic (mammary) artery.
What structure(s) innervate the intercostal mm.?
The ventral rami of the true spinal (intercostal) nn.
In what order is each intercostal neurovascular bundle arranged?
From superior to inferior: interostal vein, intercostal artery and intercostal nerve (VAN).
What portion of the rib is designed to protect them?
The costal groove.
Which component of the neurovascular bundle is least protected by this?
The intercostal nerve.
What is the clinical implication of the intercostal nerve not being protected?
Insertion of a needle for thoracocentresis (removal of fluid from the pleural cavity) should have the needle placed mid-way between ribs to ensure the intercostal nerve of the upper rib is not punctured, nor is its collateral branch that passes close to the upper border of the lower rib.
