Breast Anatomy PDF

ANATOMY OF THE BREAST  Introduction The primary function of the breasts, as mammary glands, is the feeding and nourishing of an infant with breast milk during the maternal lactation period. The round shape of the breast helps to limit the loss of maternal body heat. Mil...

ANATOMY OF THE BREAST  Introduction The primary function of the breasts, as mammary glands, is the feeding and nourishing of an infant with breast milk during the maternal lactation period. The round shape of the breast helps to limit the loss of maternal body heat. Milk production depends upon a higher- temperature environment for the milk- production function of the mammary gland tissues, the lactiferous ducts.  Surface anatomy The breast is located on the anterior thoracic wall. It extends horizontally from the lateral border of the sternum to the mid-axillary line. Vertically, it spans between the 2nd and 6th Intercostal cartilages. It lies superficially to the Pectoralis Major (PM) and Serratus Anterior muscles  Regions of the breast The breast can be considered to be 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 PM – towards the Axillary fossa.  Parts of the breast 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 areolae. There are numerous sebaceous glands within the areolae – – these enlarge during pregnancy, – secreting an oily substance that acts as a protective lubricant for the nipple.  Composition of the breast The breast is composed of mammary glands surrounded by a connective tissue stroma. Mammary Glands Connective Tissue Stroma  Mammary Glands The mammary glands are modified sweat glands. They consist of a series of ducts and secretory lobules (15-20). Each lobule consists of many alveoli drained by a single lactiferous duct. These ducts converge at the nipple like spokes of a wheel.  Connective Tissue Stroma The connective tissue stroma is a supporting structure which surrounds the mammary glands. It has a fibrous and a fatty component. The fibrous stroma condenses to form suspensory ligaments (of Cooper). These ligaments have two main functions: – Attach and secure the breast to the dermis and underlying pectoral fascia. – Separate the secretory lobules of the breast.  Pectoral Fascia The base of the breast lies on the pectoral fascia – – a flat sheet of connective tissue associated with the PM muscle. It acts as an attachment point for the suspensory ligaments. There is a layer of loose connective tissue between the breast and pectoral fascia – – known as the retro - mammary space. This is a potential space, often used in reconstructive plastic surgery.  Vasculature Arterial supply to the medial aspect of the breast is via the internal thoracic artery, a branch of the subclavian artery. The lateral part of the breast receives blood from four vessels: – Lateral thoracic and ) originate from the axillary artery. – thoracoacromial branches ) 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 4thintercostal spaces. Mammary branch – originates from the anterior Intercostal artery. The veins of the breast correspond with the arteries, draining into the Axillary and internal thoracic veins.  Lymphatic Drainage The lymphatic drainage of the breast is of great clinical importance due to its role in the metastasis of breast cancer cells. There are three groups of lymph nodes that receive lymph from breast tissue – the axillary nodes (75%) – parasternal nodes (20%) – posterior intercostal nodes (5%).  Lymphatic drainage of skin over the breast The skin of the breast also receives lymphatic drainage: Skin – drains to the – Axillary, – inferior deep cervical and – infraclavicular nodes. Nipple and areola – drain to the subareolar lymphatic plexus. Disposition of the Axillary lymph nodes Importance of Lymphatic of the breast Approximately 75% of the lymph from the breast travels to the axillary lymph nodes on the same side of the body, whilst 25% of the lymph travels to the parasternal nodes (beside the sternum bone). A small amount of remaining lymph travels to the other breast and to the abdominal lymph nodes.  The Axillary lymph nodes (ALN) ALNs include the pectoral (chest), subscapular (under the scapula), and humeral (humerus-bone area) lymph-node groups, These drain to the central axillary lymph nodes and to the apical axillary lymph nodes.  Nerve Supply The breast is innervated by the anterior and lateral cutaneous branches of the 4th to 6th Intercostal nerves. These nerves contain both sensory and autonomic nerve fibres (the autonomic fibres regulate smooth muscle and blood vessel tone). It should be noted that the nerves do not control the secretion of milk. This is regulated by the hormone Prolactin, which is secreted from the anterior pituitary gland.  Clinical significance The most frequent benign conditions are puerperal mastitis, fibrocystic breast changes and mastalgia. Lactation unrelated to pregnancy can occur as galactorrhea (spontaneous milk flow) from the adverse effects of drugs, (e.g. antipsychotic medications), extreme physical stress, or endocrine disorders. In a newborn infant, the capability of lactation is a consequence of the mother's circulating hormones (prolactin, oxytocin, etc.) in his or her blood stream, which were introduced by the shared circulatory system of the placenta. The lymphatic drainage of the breasts is especially relevant to oncology because breast cancer is common to the mammary gland, and cancer cells can metastasize (break away) from a tumor and be dispersed to other parts of the body utilizing the lymphatic system.  Clinical significance contd. Breast cancer Breast cancer is the most common cause of cancer death among women. It is one of the leading causes of death among women. Factors that appear to be implicated in decreasing the risk of breast cancer are – regular breast examinations by health care professionals, – regular mammograms, – self-examination of breasts, – healthy diet, and exercise to decrease excess body fat.  Clinical significance contd. Breast cancer Both females and males develop breasts from the same embryological tissues. Normally, males produce lower levels of estrogens and higher levels of androgens, namely testosterone, which suppress the effects of estrogens in developing excessive breast tissue. In boys and men, abnormal breast development is manifested as gynecomastia, the consequence of a biochemical imbalance between the normal levels of estrogen and testosterone in the male body. Around 70% of boys temporarily develop breast tissue during adolescence. The condition usually resolves by itself within two years. When male lactation occurs, it is considered a symptom of a disorder of the pituitary gland. What is she doing?  Can we adjourn? Let us call it a day.