Internal intercostal muscle

Dr Daniel J Bell ◉ and Assoc Prof Craig Hacking ◉ ◈ et al.

The internal intercostal muscles are important muscles of respiration. They number eleven on each side and are located in the intercostal spaces, reducing the transverse dimension of the thoracic cavity during expiration.

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Article:

Gross anatomy
Blood supply
Innervation
Action
Related articles
References

Images:

Cases and figures

Gross anatomy

The internal intercostal muscles are the middle muscle of the three intercostal muscles and arise from the costal groove of the rib above. The fibers run in a downwards, backwards and lateral direction (perpendicular to the external intercostal muscles) and insert into the superior border of the rib below. Anteriorly, the lower muscles become continuous with the internal oblique muscles in the anterolateral abdominal wall. As their name indicates, they are internal to the external intercostal muscles.

Blood supply

arterial supply: anterior and posterior intercostal arteries
venous drainage: internal thoracic vein and intercostal veins

Innervation

Muscular branches from the intercostal nerves of the respective intercostal space (T1-T11), which run with the intercostal vessels under the costal groove in between the internal and innermost intercostal muscles.

Action

Internal intercostal muscle contraction causes reduction in volume of the thoracic cavity in the transverse dimension, expelling air from the lungs during expiration. They are weaker than the external intercostal muscles.

References

Anatomy: Thoracic

Anatomy: Thoracic

thoracic skeleton
- thoracic cage
  - ribs
    - typical ribs
    - atypical ribs
    - variant anatomy
  - costal cartilage
  - sternum
- thoracic spine
- articulations
muscles of the thorax
spaces of the thorax
thoracic viscera
- tracheobronchial tree
  - trachea
- lungs
- heart
  - cardiac chambers
  - heart valves
  - pectinate muscles
  - cardiac fibrous skeleton
    - aortic annulus
  - coronary arteries
    - coronary arterial dominance
    - myocardial segments
    - left main coronary artery (LMCA)
      - ramus intermedius artery (RI)
      - circumflex artery (LCx)
        
        obtuse marginal branches (OM1, OM2, etc))
        
        Kugel's artery
      - left anterior descending artery (LAD)
        
        diagonal branches (D1, D2, etc)
        
        septal perforators (S1, S2, etc)
    - right coronary artery (RCA)
      - conus artery
      - sinoatrial nodal artery
      - acute marginal branches (AM1, AM2, etc)
      - inferior interventricular artery (PDA)
      - posterior left ventricular artery (PLV)
    - congenital anomalies
  - innervation of the heart
  - fetal circulation
    - foramen ovale
    - fossa ovale
  - pericardium
    - pericardial space
    - oblique pericardial sinus
    - transverse pericardial sinus
    - pericardial recesses
      - aortic recesses
        
        superior aortic recess
        
        inferior aortic recess
      - pulmonic recesses
        
        right pulmonic recess
        
        left pulmonic recess
      - postcaval recess
      - pulmonary venous recesses
        
        right pulmonary venous recess
        
        left pulmonary venous recess
    - pericardial ligaments
    - epicardial fat pad
- esophagus
  - Zenker diverticulum
  - Killian-Jamieson diverticulum
- thymus
  - retrocaval thymus
- breast
  - nipple-areola complex
  - terminal ductal lobular unit
  - axillary tail
    - foramen of Langer
  - mammary fat
  - Montgomery glands
    - Montgomery tubercles
  - Cooper ligaments
    - crests of Duret
  - retromammary space (Chassaignac bursa)
  - lymphatic drainage
    - Sappey plexus
    - intramammary lymph nodes
  - variants
    - supranumerary nipple (polythelia)
    - accessory breast tissue (polymastia)
    - breast hypoplasia
    - amastia
    - amazia
blood supply of the thorax
- arteries
  - thoracic aorta (development)
  - pulmonary trunk
    - left pulmonary artery
      - aberrant left pulmonary artery
    - right pulmonary artery
- veins
  - superior vena cava (SVC)
    - superior cavoatrial junction
    - variant anatomy
  - inferior vena cava (IVC)
    - inferior cavoatrial junction
  - coronary veins
    - cardiac veins which drain into the coronary sinus
      - great cardiac vein
      - middle cardiac vein
      - small cardiac vein
      - posterior vein of the left ventricle
      - vein of Marshall (oblique vein of the left atrium)
    - anterior cardiac veins
    - venae cordis minimae (smallest cardiac veins or thebesian veins)
  - pulmonary veins
    - bronchial veins
  - thoracoepigastric vein
lymphatics
innervation of the thorax

Article information

rID: 37684

System: Chest, Musculoskeletal

Section: Anatomy

Tag: muscles, thoracic wall, stub, refs

Synonyms or Alternate Spellings:

Internal intercostal muscles
Intercostales interni

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Cases and figures

Figure 1: Intercostal space Figure 1: Intercostal space

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