Mammary Glands Anatomy PDF

Pectoral Region The Mammary Gland - Shape and type (Fig. 26): it is a modified sweat gland (rudimentary in male), hemispherical in shape and the covering skin contains the nipple and areola. It has a circular base and an axillary tail. - Position (F...

Pectoral Region The Mammary Gland - Shape and type (Fig. 26): it is a modified sweat gland (rudimentary in male), hemispherical in shape and the covering skin contains the nipple and areola. It has a circular base and an axillary tail. - Position (Figs. 26, 27): It lies in the superficial fascia of the pectoral region at the front and side of the thorax. The base of the mammary gland extends from the 2nd rib above to the 6th costal cartilage below and from the lateral border of the sternum medially to the mid-axillary line laterally. Its base lies on the deep fascia covering the pectoralis major (pectoral fascia) and serratus anterior muscles as well as the aponeurosis of the external oblique muscle The axillary tail. it is a tongue-like prolongation from the superolateral quadrant of the gland which curves around the lower border of pectoralis major muscle, pierces the deep axillary fascia and extends upwards into the axilla. N.B. The mid-axillary line is a vertical line passing in the midline of the axilla midway between its anterior and posterior fold - Structure: A- Internal structure (Figs. 28, 29): The mammary gland consists of 16-20 lobes embedded in the fat of the superficial fascia and arranged in a radial manner converging towards the nipple. The lobes are supported and separated into fascial compartments by fibrous septa called Cooper's ligaments extending from the skin to the deep fascia on the chest wall and suspending the breast to the skin. Each lobe collects its secretion into a lactiferous duct. All lactiferous ducts converge upon the nipple. As it passes deep to the areola, each lactiferous duct widens to form a lactiferous sinus and then becomes narrow again traversing the nipple to open on its summit. N.B. The gland is small in children. It enlarges in young females at puberty due to increase in the amount of superficial fascia and fat (stroma). The second enlargement occurs during the first pregnancy as result of proliferation of the glandular tissue and the gland reaches its maximum size during lactation.  Pectoral Region Pectoralis major rib External oblique muscle & aponeurosis Fig. 26: Mammary gland: extent anterior & underlying structures. ">....>----.._X Axillary tail 12 o clock Superior Supenor /.medial lateral : / ' I. Inferior lateral 9 t ·.'· --J :' :-r ·-·. ' 3 Inferior medial 6 Right breast Fig. 27: Quadrants of t he breast and the tail  Pectoral Region B- Covering skin (Nipple and Areola) (Fig. 28): The nipple is a conical projection placed usually over the 4th intercostals space and is traversed by the lactiferous ducts which open on its summit. The position of the nipple changes after the 1st childbirth and lactation where it lies at a variable lower level. The areola is a circular area of pigmented skin which surrounds the base of the nipple. In virgins the areola is pinkish and becomes darker in color during the first pregnancy and never returns pinkish again. It contains a number of sebaceous (areolar) glands. -Arterial supply (Fig. 29): 1. Lateral thoracic artery: from the 2nd part of the axillary artery, supplies mainly the lateral half of the breast. 2. Perforating branches of the internal mammary artery, especially in the 2nd, 3rd & 4th intercostal spaces, supply mainly the medial half of the breast. 3. Lateral branches of the posterior intercostal arteries (are a minimal source) share in supplying the lateral half. 4. Pectoral branch of acromiothoracic artery of the second part of Axillary artery. - Lymphatic drainage (Fig. 30,31): the lymphatics of the breast are arranged as two plexuses: A. Superficial (subareolar) plexus: it lies under the skin of the areola: It receives afferents from the mammary gland and sends its efferents to the deep lymphatic plexus, through interlobular lymph vessels. B. Deep lymphatic plexus: it lies on the deep fascia on which the mammary gland lies. It receives its afferents from the four quadrants of the mammary gland and the superficial plexus. It sends its efferents along the blood supply as follows: 1. Lateral quadrants: send efferents: Mainly to the pectoral group of axillary lymph nodes. From the tail to the subscapular group of axillary lymph nodes. From the upper lateral part to the infra-clavicular nodes (a superficial group lying outside the axilla). Its efferents pierce the anterior wall of the axilla to drain finally into apical group of axillary lymph nodes. N.B. Few lymphatics from the lateral part follow the posterior intercostals arteries backwards to reach the para-aortic lymph nodes inside the thorax.  Pectoral Region Gland lobules Suspensory ligaments Areola Nipple anterior Lactiferous duct Lactiferous sinus Fig. 28: Internal structures of the breast Clavfde 2 00 rib Pectoral fascia Gland lobules Lactiferous sinus Fig. 29: Sagittal section of the breast  Pectoral Region 2. Medial quadrants: send efferents: Mainly to the parasternal lymph nodes which lie along the internal mammary artery inside the thorax. Some lymphatics cross the middle line to the deep plexus of the opposite side. Some lymphatics from the lower medial part pierce the abdominal wall to reach the subdiaphragmatic plexus N.B. The axillary lymph nodes commonly receive more than 75% of the lymph from the breast while most of the reminder, from the medial and lateral halves of the gland, enters the parasternal nodes. Clinical importance: In cancer breast: *If the malignant tumor invades the fibrous septa and may pull on the overlying skin leading to retraction of the nipple. Obstruction of the superficial lymphatics caused oedema of the skin which is pitted by the attachments of the hair follicles and the skin appears as an orange peel a condition called peau d'orange. Breast abscess should be drained by a radial incision to avoid spread of infection to the neighboring lobes and to minimize the damage of the radially arranged ducts.  Pectoral Region Internal mammary (thoracic) artery Lateral thoracic artery Anterior perforating branches Fig. 30: Mammary gland {arterial supply) - S: Supraclavicular LN 1: Apical group & infraclavicular LN C: Central group of LN L: Lateral group of LN A: Anterior group of LN P: Posterior group of LN PS: Parasternal LN R: Plexus of lymphatics on rectus sheath and subphrenic plexus Fig. 31: Lymphatic drainage of the breast