Muscles of the Thoracic Wall Quiz

Muscles of Respiration

• The serratus posterior inferior muscle is said to depress the inferior ribs and prevent them from being pulled superiorly by the diaphragm.
• Recent studies suggest that the serratus posterior inferior muscle functions to stabilize the scapula and assist in forceful inspiration.

Muscles Implicated in Chronic Pain

• The serratus posterior inferior muscle is implicated as a source of chronic pain in myofascial pain syndromes.

Role of Levatores Costarum Muscles

• The levatores costarum muscles assist in normal inspiration by elevating the ribs.

Layers of Intercostal Muscles

• The external intercostal muscles form the superficial layer of the intercostal muscles.
• The internal intercostal muscles form the inner layer of the intercostal muscles.

Accessory Muscles of Respiration

• The pectoralis minor muscles primarily act on the upper limbs but can also function as accessory muscles of respiration.

Non-True Muscles of the Thoracic Wall

• The pectoralis major muscle is NOT considered a true muscle of the thoracic wall.

Elevation of the Ribs

• The scalene muscles are responsible for elevating the superior four ribs and increasing the anterior-posterior dimension.

Forced Inspiration

• The scalene muscles primarily elevate the ribs during forced inspiration.

Depression of the Ribs

• The internal intercostal muscles are responsible for depressing the ribs during active (forced) respiration.
• The serratus posterior inferior muscle weakly depresses the ribs.
• The levatores costarum muscles are believed to act similarly to the internal intercostal muscles, depressing the ribs during active (forced) respiration.