4.3 Thoracic Wall: Vessels & Nerves

Thoracic Wall: Vessels & Nerves

Overview of the Thoracic Wall

  • Vessels and Nerves: Essential components for understanding blood supply, drainage, and nerve distribution in the thoracic wall.

  • Mnemonic to Remember: "VAN" (Vein, Artery, Nerve) is used to describe the typical arrangement of vessels in the intercostal spaces.

Anatomy of the Thoracic Wall

Blood Supply

  • Key Arteries:

    • Subclavian Artery: Supplies blood to the upper limb, neck, and parts of the thorax.

    • Axillary Artery: Continuation of the subclavian artery, supplying the thoracic and pectoral regions.

    • Thoracic Aorta: The main arterial supply from the heart to the thorax.

  • INTERCOSTAL VESSELS & NERVES
    Intercostal space containing intercostal muscles & intercostal
    • vein, artery, nerve – VAN - Near angle of rib, they travel along costal
    grooves
    • Follow same path (arteries travel with veins and nerves) – also – collateral

  • Branches of the Thoracic Aorta:

    • Posterior Intercostal Arteries: Supply blood to intercostal spaces 3-11 and are branches directly from the thoracic aorta.

    • Anterior Intercostal Arteries: Branch from the internal thoracic artery, which is a branch of the subclavian artery, supplying the first two intercostal spaces.

  • Diaphragm Blood Supply:

    • Supplied by Musculophrenic Artery (from the internal thoracic artery) and Inferior Phrenic Arteries (branches of the abdominal aorta).

Venous Drainage

  • Key Veins:

    • Azygos Vein (right): Drains posterior thoracic wall.

    • Hemiazygos Vein (left inferior): Drains lower left regions.

    • Accessory Hemiazygos Vein (left superior): Drains upper left regions.

      Venous Pathway:

    • Posterior intercostal veins drain into the azygos system, while anterior intercostal veins drain into the Internal Thoracic Vein, which then leads to the Subclavian Vein.

  • Major Lymphatic Vessel: Thoracic Duct - Drains lymph from the lower body and left side of the upper body into the venous system.

Nerve Supply

  • Posterior ramus supplies skin (sensory) and muscles (motor) of the back

  • Anterior ramus (intercostal nerves) innervate the skin and muscles of the anterior and lateral thorax and abdomen (intercostal
    muscles, rectus abdominus and abdominal obliques

  • Intercostal Nerves (T1-T12): These are branches of the anterior rami of thoracic spinal nerves.

  • T1-11 = intercostal nerves, T12 = subcostal nerve

    • T1: Joins the brachial plexus.

    • T2: Supplies the floor of the axilla and parts of the arm.

    • T3-T6: Provide sensory and motor innervation to the intercostal muscles in their respective spaces.

    • T7-T11: Supply the anterior abdominal wall.

    • T12: Known as the subcostal nerve supplying the lower anterior abdominal wall.

  • Cutaneous Branches:

    • Anterior and lateral branches provide sensory innervation to the skin of the thorax, while collateral branches accompany the intercostal vessel.

Summary of Key Structures

  • Blood Supply:

    • Thoracic aorta, subclavian artery, axillary artery.

  • Venous Drainage:

    • Azygos vein, hemiazygos vein, accessory hemiazygos vein, thoracic duct for lymphatic drainage.

  • Nerve Innervation:

    • Intercostal nerves from T1-T12 supply the thoracic wall and parts of the abdomen.

Additional Notes

  • The Intercostal Muscles play a crucial role in respiration, with blood supply from both the intercostal arteries and the internal thoracic artery.

  • There are complex anastomoses between anterior and posterior intercostal arteries, ensuring adequate blood supply throughout the thoracic wall.

  • Autonomic fibers from intercostal nerves can innervate multiple body areas, illustrating the complex neural control present in thoracic innervation.

Further Reading

  • Explore anatomy books or resources on thoracic vascular anatomy for more detailed illustrations and comprehensive understanding of thoracic structures.