Walls Of Thorax

Question 1

Thoracic wall

Answer 1

Thoracic cage forms skeletal framework of walls of thorax.
Gap between them are intercostal spaces filled by intercostal vessels and nerves and muscles.
9 intercostal spaces anteriorly and 11 intercostal spaces posteriorly.

Question 2

Intercostal muscles

Answer 2

1) External intercostal muscles extending from tubercle of rib posteriorly to costochondral junction anteriorly.
2) Internal intercostal muscle extending from lateral border of sternum to angle of rib.
3) Transverse thoracis muscle which is divisible into 3 parts - subcostalis , intercostalis intimi and sternocostalis.

Nerve supply is by intercostal nerves and actions are
1) To prevent intercostal spaces being drawn in during inspiration and bulging outwards during expiration.
2) External intercostal elevate ribs during deep inspiration.
3) Internal intercostal depress ribs during deep expiration.