Thoracic Cavity Overview

Functions of the Thoracic Cavity

• Air movement: diaphragm, ribs assist in breathing.

• Protection: vital organs and abdominal viscera shielded.

• Passageway: for structures like esophagus, trachea, and blood vessels.

Component Parts of the Thoracic Cavity

• Thoracic Wall:
    - 12 thoracic vertebrae, 12 ribs per side, sternum and costal cartilages.

• Diaphragm:
    - Musculotendinous, affects thoracic volume during respiration.

• Mediastinum:
    - Midline partition; includes heart, pericardium.

• Pleural Cavities:
    - Right and left pleural cavities lined by pleura.

Relationships within the Thoracic Cavity

• Thoracic Apertures:
    - Superior: opens to the neck; passage for major structures.
    - Inferior: separated from abdomen by diaphragm.

• Breast anatomy:
    - Contains glands, vessels and lymphatics in pectoral region.

Key Features of Thoracic Structure

• Superior Mediastinum:
    - Contains trachea and aortic arch; marks rib II articulation.

• Venous System:
    - Drainage pathways include superior/inferior vena cava and azygos system.

Thoracic Wall Muscles and Functions

• Intercostal Muscles:
    - External: primarily for inspiration.
    - Internal: primarily for expiration.
    - Innermost: assist with internal intercostals.

• Other Muscles:
    - Subcostales and transversus thoracis involved in respiration.

Venous and Lymphatic Drainage

• Venous:
    - Intercostal veins drain into azygos system.

• Lymphatic:
    - Drainage includes parasternal, intercostal, and thoracic ducts.

Innervation

• Nerves:
    - Mainly intercostal nerves (T1 to T11) provide motor and sensory function to thoracic wall.

• Sympathetic Fibers:
    - Distributed to the periphery.