Chapter 53: Chest Wall & Breast Anatomy

Chest Wall & Breast Anatomy anatomical overview details the structure and clinical relevance of the chest wall and mammary gland, beginning with the osseo-cartilaginous frame consisting of twelve pairs of ribs, the sternum, and the twelve thoracic vertebrae. The discussion highlights the anatomy of a typical rib, including the crucial internal costal groove which houses the intercostal neurovascular bundle, a vital consideration during procedures like thoracocentesis. Common congenital deformities, specifically Pectus excavatum (sunken chest) and Pectus carinatum (pigeon chest), are described, noting the cardiopulmonary significance of severe defects. The chapter examines the complex set of joints governing respiratory movement, such as the costovertebral and costotransverse articulations, and the sternocostal joints, emphasizing that the first costal cartilage connects to the manubrium via a fibrous synarthrosis. The intrinsic chest wall muscles, including the three layers of intercostals (external, internal, innermost) and the transversus thoracis, are detailed, along with the location and clinical significance of the variable sternalis muscle. The vascular supply is thoroughly mapped, noting the importance of the internal thoracic artery anteriorly, which is the vessel of choice for coronary artery bypass grafting (CABG) and gives off key perforating branches. Innervation is segmental, derived from the thoracic spinal nerves; special attention is given to the intercostobrachial nerve (lateral cutaneous branch of T2), which is frequently injured during breast-related surgeries. Furthermore, the text thoroughly explores the female breast, defining its borders, soft tissue components, and support structures, notably the suspensory ligaments (Cooper’s ligaments), which help maintain shape. The microstructure and development of the gland, including hormonal changes during thelarche and lactation (which transitions lobules from Type 1 to Type 4), are explained. Clinically, the lymphatic drainage pathway is paramount, with (greater than) 75% of lymphatics flowing to the five groups of axillary lymph nodes (Levels 1, 2, and 3), necessitating sentinel lymph node biopsy (SLNB) for cancer staging. Finally, various surgical approaches for accessing the thoracic cavity are covered, including sternotomy, thoracotomy incisions (posterolateral, anterolateral, and ‘clam shell’), and advanced regional pain management techniques like Pecs and TTP blocks.