Session 1.1g - TeachMeAnatomy - Muscles of the Thoracic Cage Flashcards
How many muscles make up the thoracic cage?
Five
What are the muscles that make up the thoracic cage?
- The intercostals (external, internal and innermost)
- Subcostals
- Transversus thoracic
What do the muscles of the thoracic cage do?
These muscles act to change the VOLUME of the thoracic cavity during respiration.
What do pectoralis major, minor, serratus anterior and the scalene muscles have in common with regards to the thoracic cage?
They do not comprise the thoracic wall, but do ATTACH to it.
As well as the 5 muscles that makes up the thoracic cage, there are some other muscles that do not comprise the thoracic wall, but do attach to it. What are these muscles?
- Pectoralis major
- Pectoralis minor
- Serratus anterior
- Scalene muscles
Where do the intercostal muscles lie?
In the intercostal spaces between ribs.
Which muscles lie in the intercostal spaces between ribs?
Intercostal muscles
How are the intercostal muscles organised?
Into three layers
- external
- internal
- innermost
How many external intercostal muscles are there?
11 pairs
In what direction do the external intercostals run?
Inferoanteriorly from the rib above to the rib below
What are the external intercostals continuous with?
The external oblique of the abdomen.
What are the attachments of the external intercostals?
Originate at the lower border of the rib, inserting into the superior border of the rib below.
Where do the external intercostals originate?
Lower border of the rib
Where do the external intercostals insert?
Superior border of the rib below
What is the action of the external intercostals?
Elevates the ribs, increasing the thoracic volume
What is the innervation of the external intercostals?
Intercostal nerves (T1-T11).
What type of muscles are internal intercostals?
Flat muscles
Where do the internal intercostals lie?
Deep to the external intercostals
What direction do the internal intercostals run?
Like the external intercostals, they run from the rib above to the one below, but in an opposite direction (inferoposteriorly)
Compare and contrast the internal intercostals?
Like the external intercostals they run from the rib above to the one below
However, they run in the opposite direction to external intecostals:
- external = inferoanteriorly
- internal = inferoposteriorly
What are the internal intercostals continuous with?
The internal oblique muscle of the abdominal wall
What are the attachments of the internal intercostals?
Originates from the lateral edge of the costal groove and inserts into the superior surface of the rib below.
Where do the internal intercostals originate?
From the lateral edge of the costal groove
Where do the internal intercostals insert?
Into the superior surface of the rib below
What is the action of the internal intercostals?
The interosseous part reduces the thoracic volume by depressing the ribcage, and the interchondal part elevates the ribs.
What does the interosseous part of the internal intercostals do?
Reduces the thoracic volume by depressing the ribcage
What do the interchondral part of the internal intercostals do?
Elevates the ribs