Intercostal Muscles Anatomy

Study Notes

External Intercostal Muscles:
- Originate from the rib above and insert into the rib below
- Assist in inspiration by elevating the ribs and expanding the chest cavity
Internal Intercostal Muscles:
- Originate from the rib above and insert into the rib below
- Assist in expiration by depressing the ribs and reducing the chest cavity
Innermost Intercostal Muscles:
- Thin layer of muscle fibers between the internal intercostal muscles and the endothoracic fascia
- Assist in expiration by depressing the ribs and reducing the chest cavity

Intercostal Nerves: originate from the thoracic spinal nerves (T1-T12) and supply the intercostal muscles
Phrenic Nerve: supplies the diaphragm, which works in conjunction with the intercostal muscles during breathing

Inspiration: external intercostal muscles contract, elevating the ribs and expanding the chest cavity
Expiration: internal intercostal muscles and innermost intercostal muscles contract, depressing the ribs and reducing the chest cavity

Injury or paralysis: can lead to respiratory difficulties and impaired breathing
Surgical procedures: may involve the intercostal muscles, such as thoracic surgery or chest tube insertion

Intercostal muscles are situated between the ribs in the thoracic cavity
They facilitate breathing by expanding and contracting the chest cavity during inspiration and expiration

External Intercostal Muscles:
- Originate from the rib above and insert into the rib below
- Assist in inspiration by elevating the ribs and expanding the chest cavity
Internal Intercostal Muscles:
- Originate from the rib above and insert into the rib below
- Assist in expiration by depressing the ribs and reducing the chest cavity
Innermost Intercostal Muscles:
- Located between the internal intercostal muscles and the endothoracic fascia
- Assist in expiration by depressing the ribs and reducing the chest cavity

Intercostal Nerves:
- Originate from the thoracic spinal nerves (T1-T12)
- Supply the intercostal muscles
Phrenic Nerve:
- Supplies the diaphragm
- Works in conjunction with the intercostal muscles during breathing

Inspiration:
- External intercostal muscles contract
- Ribs are elevated and the chest cavity expands
Expiration:
- Internal intercostal muscles and innermost intercostal muscles contract
- Ribs are depressed and the chest cavity reduces

Injury or paralysis of intercostal muscles can lead to:
- Respiratory difficulties
- Impaired breathing
Surgical procedures involving intercostal muscles include:
- Thoracic surgery
- Chest tube insertion