Muscle
Accessory muscles of respiration
Muscles recruited according to breathing demand
High-yield
Accessory does not mean that every named muscle is silent at rest. Recruitment depends on respiratory demand, mechanics and which attachments are stabilized.
Overview
Breathing uses a coordinated set of muscles whose contribution changes with effort and posture. Sternocleidomastoid and some shoulder-girdle muscles can assist inspiration, while scalenes can already be active during quiet breathing. Abdominal muscles assist active expiration.
Reference facts
- Origin
- Examples: sternocleidomastoid from sternum and clavicle; scalenes from cervical transverse processes; pectoralis minor from ribs 3–5
- Insertion
- Corresponding attachments: mastoid and superior nuchal line; first or second rib; coracoid process. Fixing one end changes the respiratory mechanical effect
- Innervation
- Sternocleidomastoid: accessory nerve with cervical contributions; scalenes: cervical anterior rami; pectoral muscles: pectoral nerves
- Action
- Additional inspiratory force can elevate the rib cage; abdominal contraction raises abdominal pressure during active expiration. Recruitment varies with demand and posture.
- Blood supply
- Separate regional supplies, including cervical branches for scalenes and thoracoacromial branches for pectoral muscles
Clinical correlation
Prominent neck-muscle activity can accompany increased respiratory effort. Its absence does not exclude severe airflow obstruction; stable patients with severe COPD do not invariably recruit sternocleidomastoid at rest.
Frequently asked questions
What does the accessory muscles of respiration do?
Additional inspiratory force can elevate the rib cage; abdominal contraction raises abdominal pressure during active expiration. Recruitment varies with demand and posture.
What nerve innervates the accessory muscles of respiration?
Sternocleidomastoid: accessory nerve with cervical contributions; scalenes: cervical anterior rami; pectoral muscles: pectoral nerves.
Where does the accessory muscles of respiration attach?
Origin: Examples: sternocleidomastoid from sternum and clavicle; scalenes from cervical transverse processes; pectoralis minor from ribs 3–5. Insertion: Corresponding attachments: mastoid and superior nuchal line; first or second rib; coracoid process. Fixing one end changes the respiratory mechanical effect.
What is the blood supply of the accessory muscles of respiration?
The accessory muscles of respiration is supplied by the separate regional supplies, including cervical branches for scalenes and thoracoacromial branches for pectoral muscles.