Respiratory muscles

Muscle group:

• primary inspiratory muscle.

Innervation:

• phrenic nerve C3-C5.

Ventilation role:

• quiet and forced inspiration.

Other functions:

• generates dynamic transdiaphragmatic pressures by co-contract with the abdominal, internal intercostal, pelvic floor and intrinsic laryngeal muscles to regulate air flow for forced expiratory and body functions e.g. sighing, coughing, defecating
• aids venous and lymphatic return
• supports lower oesophageal sphincter function
• assists dynamic postural stability.

Muscles:

• internal intercostals
• external intercostals.

Muscle group:

• accessory inspiratory muscle
• expiratory muscle.

Innervation:

• spinal nerves T1-T11.

Ventilation role:

• quiet and forced inspiration (external intercostals only)
• forced expiration (internal intercostals only)
• forced expiratory actions e.g. cough.

Other functions:

• stabilises the rib cage and intercostal spaces when the diaphragm is contracting
• supports diaphragm function for efficient contraction.

Muscles:

• rectus abdominus
• external obliques
• internal obliques
• transversus abdominus.

Muscle group:

• accessory inspiratory muscle
• primary expiratory muscles.

Innervation:

• spinal nerves T6-T12.

Ventilation role:

• forced expiration
• forced expiratory actions e.g. cough.

Other functions:

• supports diaphragm function for efficient contraction—especially in sitting
• activates posterior pelvic tilt and trunk flexion movements
• facilitates postural stability for static and dynamic postural reactions.

Muscles and innervations:

• upper trapezius – accessory cranial nerve XI
• sternocleidomastoid – accessory cranial nerve XI and spinal nerve C2 and C3
• scalenes – spinal nerves C2-C7
• serratus anterior – long thoracic nerve of brachial plexus C5-C7
• pectoralis minor and major – lateral/medial pectoral nerves of brachial plexus C5-T1
• latissimus dorsi – thoracodorsal nerve C6-C8.

Other accessory muscles include the deep thoracic and paraspinal muscles.

Muscle group:

• accessory inspiratory muscles
• accessory expiratory muscles.

Ventilation role:

• forced inspiration
• forced expiration
• cough.

Other functions:

• activates head, neck, scapular and upper limb movements or stabilisation.