Book 4 - Self Instructional Manual for Cancer Registrars - SEER ...

BreastThe breasts, or mammary glands, are modified sweat glands and, in some of the earlierclassification systems, were grouped with the inte[gumentary system. The breasts lie on top of thechest wall immediately over the pectoral muscles*, pectoralis major and peetoralis minor, and areattached to the pectoralis major by a layer of connective tissue, the pectoral fascia. On the lowerlateral aspect of the chest wall, the breasts are in contact with the serratus anterior muscles 2.Each breast consists of many separate glands that are connected by individual ducts (lactiferousducts) to the nipple. These glands constitute the lobes of the breast, 15 to 20 lobes (glands) for eachbreast. Each lobe is composed of many lobules which are formed from minute ducts and containsecreting cells (alveoli). The lobes are separated from each other by dense connective tissue and aresurrounded by quantities of adipose tissue (fat). Suspensory ligaments (Cooper's ligaments) run fromthe corium of the skin through the breast to the fascia overlying the chest wall.Located in the center of each breast is a nipple bordered by a circular pigmented area of skincalled the areola. The lactiferous ducts from the lobes of the breast converge in the nipple. Duringpregnancy, hormonal changes in the body stimulate the production of milk in the lobes (mammaryglands); the ducts transport the milk to the nipple.Figure 46. BREAST (sagittal view)_ H_roo la¢/. !_ ,Z 'Pectoratls minor "muHc L_ ms.Jo r1pectoral muscles--The function of the pectoralis major muscle is to adduct, flex, and rotate thehumerus inward. The pectoralis minor lies between the pectoralis major and serves to depressthe tip of the shoulder and help rotate the scapula downward and forward.2serratus anterior muscles--These muscles draw the scapula forward and rotate it to raise the tipof the shoulder.297