Breast Introduction PDF

# INTRODUCTION ## I. BREAST A. Modified sweat gland embryologically derived from the skin 1. Breast tissue can develop anywhere along the milk line, which runs from the axilla to the vulva (e.g., supernumerary nipples). B. The terminal duct lobular unit is the functional unit of the breast (Fig. 1...

# INTRODUCTION ## I. BREAST A. Modified sweat gland embryologically derived from the skin 1. Breast tissue can develop anywhere along the milk line, which runs from the axilla to the vulva (e.g., supernumerary nipples). B. The terminal duct lobular unit is the functional unit of the breast (Fig. 16.1); lobules make milk that drains via ducts to the nipple. C. Lobules and ducts are lined by two layers of epithelium. 1. Luminal cell layer - inner cell layer lining the ducts and lobules; responsible for milk production in the lobules and protection in the ducts 2. Myoepithelial cell layer - outer cell layer lining ducts and lobules; contractile function propels milk towards the nipple. D. Breast tissue is hormone sensitive. 1. Before puberty, male and female breast tissue primarily consists of large ducts under the nipple. 2. Development after menarche is primarily driven by estrogen and progesterone; lobules and small ducts form and are present in highest density in the upper outer quadrant. 3. Breast tenderness during the menstrual cycle is a common complaint, especially prior to menstruation. 4. During pregnancy, breast lobules undergo hyperplasia. - Hyperplasia is driven by estrogen and progesterone produced by the corpus luteum (early first trimester), fetus, and placenta (later in pregnancy) 5. After menopause, breast tissue undergoes atrophy. E. Galactorrhea refers to milk production outside of lactation. 1. It is not a symptom of breast cancer. 2. Causes include nipple stimulation (common physiologic cause), prolactinoma of the anterior pituitary (common pathologic cause), and drugs.