Thoracic Muscles and Diaphragm Anatomy

Thoracic Muscles

• Thoracic muscles are a group of muscles in the chest that form the chest wall.
• They include the diaphragm, intercostal muscles, subcostal muscles, and transversus thoracis muscle. These muscles are crucial for breathing.
• The diaphragm is the primary muscle for respiration. It is a dome-shaped muscle that separates the thoracic cavity from the abdominal cavity.
• Intercostal muscles are located between the ribs and facilitate rib movement during breathing.
• Subcostal muscles are involved in compressing the thoracic cavity.
• Transversus thoracis muscle helps to pull the ribcage downwards.
• Different muscles have different origins and insertions, impacting their functions in the thorax.

Diaphragm

• The diaphragm is a crucial muscle for respiration.
• It's a large, dome-shaped muscle that separates the thoracic and abdominal cavities.
• The diaphragm’s central tendon is a key structural component.
• The diaphragm has openings for major blood vessels and the esophagus to pass through.
  • Aortic hiatus
  • Esophageal hiatus
  • Caval opening
• The phrenic nerves are vital for diaphragm function as they stimulate it.
• Pericardial branches of the phrenic nerves innervate the pericardium.

Pectoral Muscles

• The pectoralis major is a large, fan-shaped muscle located on the anterior chest wall.
• It's responsible for adduction, medial rotation, and flexion of the humerus.
• The origin of the pectoralis major is at the medial half of the clavicle and anterior part of the chest.
• It inserts onto the intertubercular sulcus of the humerus.
• The pectoralis minor is a smaller, triangular muscle located beneath the pectoralis major.
• It helps to depress and protract the scapula.
• The subclavius muscle sits beneath the clavicle. It depresses the clavicle and stabilizes the sternoclavicular joint.
• These muscles aid in shoulder and chest movements, including breathing.

Intercostal Muscles

• External, internal, and innermost intercostal muscles form the intercostal space groupings.
• Intercostal muscles play a primary role in rib movement related to breathing.
• Intercostal nerves, arteries, and veins supply the intercostal muscles.
• Collateral branches supply other surrounding anatomical structures.

Other Thoracic Muscles

• Subcostal muscles are positioned between ribs. They aid in stabilizing the lower ribs.
• Transversus thoracis muscles are positioned within the lower part of the ribcage and have a function to help draw ribs downwards.

Thoracic Wall Breathing Movements

• Breathing involves movements of the ribs and sternum.
• Pump handle movements describe superior and anterior sternum movements.
• Bucket handle movements describe the elevation of the ribs.