组织学与胚胎学第二十章 女性生殖系统.ppt

模板来自于 / * Figure 22–25?Mammary gland. Shown here is the sequence of changes that occur in the alveolar secretory units and duct system of mammary glands before, during, and after pregnancy and lactation. (1) Before pregnancy, the gland is inactive, with small ducts and only a few small secretory alveoli. (2) Alveoli develop and begin to grow early in a pregnancy. (3) By midpregnancy, the alveoli and ducts have become large and have dilated lumens. (4) At parturition and during the time of lactation, the alveoli are greatly dilated and maximally active in production of milk components. (5) After weaning, the alveoli and ducts regress with apoptotic cell death. ? * Figure 22–26?Alveolar development in the breast during pregnancy. (a) The mammary glands of adult, nonpregnant women are inactive, with small ducts and few lobules (L) having secretory alveoli which are not well-developed. The structure with the large lumen in each lobule is part of the duct; the smaller structures are the small, undeveloped alveoli. The breasts are composed largely of connective tissue (CT), having considerable fat. (b) The glands become active during pregnancy, with the duct system growing rapidly and the secretory units of each lobule becoming much larger and more extensively branched. In this micrograph adipocytes (A) are included, but these are only a small fraction of those present. (c) During lactation, the lobules are greatly enlarged and the lumens of both the numerous glandular alveoli (A) and the excretory ducts (D) are filled with milk. The intralobular connective tissue is more sparse and difficult to see, except for small septa (arrows). All X60, H&E. ? * Figure 22–27?Actively developing and lactating alveoli. Glandular alveoli develop completely only during pregnancy and begin milk production near the end of pregnancy. (a) Alveoli (A) develop as spherical structures composed of cuboidal epithelial cells surrounded by the contractile processes of myoepithelial cells (M). Devel