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Breast Anatomy Surface Anatomy The breasts are paired structures located on the anterior thoracic wall in the pectoral region They lie superficially to the pectoralis major and serratus anterior muscles Each has a base, apex and axillary process/Axillary tail of Spence Each extends: • Horizontally from the lateral border of the sternum to the mid-axillary line • Vertically from the 2ⁿᵈ to the 6ᵗʰ rib The breast can be considered to be Surface anatomy composed of two regions: • Circular body – largest and most prominent part of the breast • Axillary tail – smaller part, runs along the inferior lateral edge of the pectoralis major towards the axillary fossa • At the centre of the breast is the nipple, composed mostly of smooth muscle fibres. Surrounding the nipple is a pigmented area of skin termed the areola. There are numerous sebaceous glands within the areola called Montgomery glands – these enlarge during pregnancy, secreting an oily substance that acts as a protective lubricant for theDivision into quadrants For clinical and descriptive purposes, the breast is divided into four quadrants: • Upper Outer Quadrant (UOQ): This includes the axillary tail and is the most common site for breast cancer due to the denser presence of glandular tissue • Upper Inner Quadrant (UIQ) • Lower Outer Quadrant (LOQ) • Lower Inner Quadrant (LIQ)Anatomical structure The breast lies on deep fascia related to the pectoralis major muscle and other surrounding muscles. A layer of loose connective tissue (the retromammary space) separates the breast from the deep fascia and provides some degree of movement over underlying structures. This is a potential space, often used in reconstructive plastic surgeryAnatomical structure The breasts consist of mammary glands and associated skin and connective tissue The mammary glands are modified sweat glands. They consist of a series of ducts and secretory lobules Anatomical structure • The glandular part of each breast is organized into 15-20 lobes • Each lobe contains smaller units called lobules where milk is produced during lactation • Each lobe is drained by a lactiferous duct • These ducts transport milk from the lobules to the nipple • Before reaching the nipple, each duct expands to form a lactiferous sinus which serves as a small reservoir for milk • These sinuses are clinically significant,Anatomical structure Connective tissue stroma • The connective tissue stroma forms the supportive framework of the breast, interspersed between the glandular components. It has a componentnd a fattyAnatomical structure Cooper’s Ligaments (Suspensory ligaments) The fibrous stroma condenses to form suspensory ligaments (of Cooper). These fibrous bands run from the subcutaneous tissue of the breast to the pectoralis major fascia. They: • Provide structural support and maintain the breast’s shape • Separate the secretory lobules of the breast Over time, or due to hormonal changes, pregnancy, or weight fluctuations, Cooper’s ligaments may stretch, leading to breast sagging In breast cancer, these ligaments can become Neurovascular supply of the breast Arterial supply The medial part of the breast – The internal thoracic artery which is a branch of the subclavian artery The lateral part of the breast receives blood mainly from four vessels: • Lateral thoracic and thoracoacromial branches – Originate from the axillary artery • Lateral mammary branches – Originate from the posterior intercostal arteries (derived from the aorta). They supply the lateral aspect of the breast in the 2nd 3rd and 4th intercostal spaces • Mammary branch – originates from the anterior intercostal artery Venous drainage Neurovascular supply of the breast Innervation Innervation of the breast is via: • Supraclavicular nerves - Originate from the cervical plexus and supply the upper and lateral aspects of the breast • Anterior and lateral cutaneous branches of the second to sixth intercostal nerves The nipple is innervated by the fourth intercostal nerve These nerves contain both sensory and autonomic nerve fibres (the autonomic fibres Lymphatic drainage of the breast Approximately 75% of lymphatic drainage from the breast is is via lymphatic vessels that drain laterally and superiorly into axillary lymph nodes which are divided into five groups: • Pectoral (Anterior) • Subscapular (Posterior) • Central • Lateral • Apical These groups all drain into the apical nodes Most of the remaining drainage is into parasternal nodes (20%) deep to the anterior thoracic wall and posterior intercostal nodes (5%) The skin of the breast also receives lymphatic drainage:Lymphatic drainage of the breast – Breast cancer Common presentations associated with breast cancer are due to blockages of the lymphatic drainage Excess lymph builds up in the subcutaneous tissue, resulting in clinical features such as swelling, nipple deviation and retraction Lymphatic drainage of the breast – Breast cancer •Metastasis commonly occurs through the lymph nodes. It is most likely to be the axillary lymph nodes that are involved. They become stony hard and fixed. Following this, the cancer can spread to distant places such as the liver, lungs, bones and ovary •initially via the lymphatics, a sentinel lymph node biopsy (SLNB) allows for the assessment of potential lymphatic spread in confirmed breast cancer •SLNB involves removal of the sentinel lymph node, which is the first lymph node (or nodes) intoThank you for listening Any questions?