The Chest Muscles

thoracic

Where the chest muscle connect

The chest muscles are the final components of the source of energy for speaking. Included in this group are the: intercostal muscles between ribs, muscles that connect the breastbone (sternum) to the collarbones (clavicles), and the muscles from the spine to the neck.

Effective Methods of Breathing

The most efficient method of breathing for relaxed speaking involves using the lower chest muscles, diaphragm, and abdominal muscles. During inhalation, each curved lower rib swings upward and outward, much like a pail handle as it is lifted away from the pail sides. During exhalation, your chest muscles relax, allowing the ribs to drop forwards and downward.

Collarbones

If you raise your relatively heavy collarbones repeatedly while you speak, you place unnecessary strain on your heart and oxygen supply. Often, people who use upper chest and shoulder (clavicular) breathing when they speak develop tight throats and harsh voices.Their breathing becomes shallow an frequent, sometimes resulting in grasping or "out- of - breath" sounds.
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Clavicular Breathing

Therefore, clavicular breathing is not recommended for speaking. An obvious external indication of clavicular breathing is the amount of shoulder raising that occur whenever a speaker inhales. This form of breathing can be useful during athletic activities when the lungs must be expanded suddenly to provide a little extra oxygen for a strenuous endeavor.

Air Supply

We have said that air supplies the power for all human speech. Remember that air is not sound or speech itself, any more than the air in a pipe organ or accordion is the sound that is produced. Air is the necessary "raw ingredient" needed to create sound. This air is captured, stored and controlled by the three components of the power source.

Intercostals

The intercostal muscles lie in the intercostal spaces between ribs. They are organised into three layers. These flat muscles lie deep to the external intercostals. Like the external intercostals, they run from the rib above to the one below, but in an opposite direction (inferoposteriorly). They are continuous with the internal oblique muscle of the abdominal wall.

  • Attachments: Originate at the lower border of the rib, inserting into the superior border of the rib below.
  • Actions: The interosseous part reduces the thoracic volume by depressing the rib cage, and the interchondral part elevates the ribs.
  • Innervation: Intercostal nerves (T1-T11).

External Intercostals

There are 11 pairs of external intercostal muscles. They run inferoanteriorly from the rib above to the rib below, and are continuous with the external oblique of the abdomen.

  • Attachments: Originate at the lower border of the rib, inserting into the superior border of the rib below.
  • Actions: Elevates the ribs, increasing the thoracic volume.
  • Innervation: Intercostal nerves (T1-T11).

Innermost Intercostals

These muscles are the deepest of the intercostal muscles, and are similar in structure to the internal intercostals.

They are separated from the internal intercostals by the intercostal neurovascular bundle and are found in the most lateral portion of the intercostal spaces.

  • Attachments: Originate at the lower border of the rib, inserting into the superior border of the rib below.
  • Actions: The interosseous part reduces the thoracic volume by depressing the rib cage, and the interchondral part elevates the ribs.
  • Innervation: Intercostal nerves (T1-T11)

Transversus Thoracis

These muscles of the thoracic cage are continuous with transversus abdominis inferiorly.

  • Attachments: From the posterior surface of the inferior sternum to the internal surface of coastal cartilages 2-6.
  • Actions: Weakly depress the ribs.
  • Innervation: Intercostal nerves (T1-T11).

Subcostals

The subcostal muscles are found in the inferior portion of the thoracic wall. They comprise of thin slips of muscle, which run from the internal surface of one rib, to second and third ribs below. The direction of the fibres parallels that of the innermost intercostal.

  • Attachments: These originate from the inferior surface of the lower ribs, near the angle of the rib. They then attach to the superior border of the rib 2 or 3 below.
  • Actions: Share the action of the internal intercostals
  • Innervation: Intercostal nerves
Muscles of the Thoracic Wall - 3D Anatomy Tutorial