2.1. Introducing the Muscles of the Thorax
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The Main Groups of Thoracic Muscles
There are three main groups of thoracic muscles:
- The intercostal muscles, which lie in-between the ribs in the intercostal spaces. These are named depending on how deep they lie, i.e. they are called the external, internal and innermost intercostal muscles.
- The diaphragm. This is a muscular sheet with two domes and a central tendon. It is the main muscle used in normal, quiet breathing. It also marks the inferior boundary of the thoracic cavity.
- 'Assisting' muscles in respiration, namely serratus anterior, serratus posterior, pectoralis major, pecotralis minor and subclavius. These muscles are only used during forced inspiration or expiration.