Histology of Mammary Gland PDF

H istology of mammary gland Presented by/ class 13 A S—u—p e r v i s e d by/DR :lamyaaFarghly  Objectives The embryology and 01. structure of the mammary gland Resting mammary 02. gland Lactating mammary gland Mammary...

H istology of mammary gland Presented by/ class 13 A S—u—p e r v i s e d by/DR :lamyaaFarghly  Objectives The embryology and 01. structure of the mammary gland Resting mammary 02. gland Lactating mammary gland Mammary gland during 03. menopause Hormonal effect on development of mammary gland the embryological origin of mammary gland Ectoderm : The ectoderm is responsible for the formation of ducts and alveoli. Mesenchyme : The mesenchyme is responsible for the formation of vessels and connective tissue. Structure of mammary gland 1- The covering skin: It is covered by thin skin rich in subcutaneous fat. The skin forms a brownish elevation called the nipple that consists of dense connective tissue and smooth muscle fibers. The nipple has 15-20 openings; each one belongs to one lactiferous duct Structure of mammary gland The lactiferous ducts dilated before their terminal opening at the summit of the nipple to form the lactiferous sinuses. The pinkish area around the nipple is called the areola. It becomes highly pigmented during pregnancy. The skin covering the nipple and areola is richly supplied by sensory nerve endings (their stimulation by the suckling infant, initiates and maintains the secretion of milk Structure of mammary gland :- 2 - The glandular tissue: consists of: A.Stroma: of connective tissue B- Parenchyma: ducts& secretory units (alveoli(، -It differs according to physiological periods of the female During childhood The mammary glands are rudimentary: - 1- Stroma: small amount. 2- Parenchyma: consists of only few ducts lined with flat epithelial cells. 2- Resting mammary gland ( adult nonpregnant female ) Stroma : A- Capsule: absent. B- Thick interlobar connective tissue septa : arise from the reticular layer of the dermis. radiating from the nipple and divide the gland into -15 Structure of mammary gland C- Interlobular connective tissue septa: divide each lobe into lobules. It is rich in adipose tissue. D- Highly cellular intralobular connective tissue: arises from the papillary layer of the dermis. contains fi broblasts, lymphocytes& plasma cells. Structure of mammary gland.2. Parenchyma : Each lobule is formed of: Numerous, small & branching intralobular ducts. The alveoli are rudimentary. Lining epithelium of the duct system- 1-The intralobular ducts: lined Structure of resting mammary gland 2-The interlobular ducts: the epithelium changes from columnar to two layers of cuboidal cells. 3- The lactiferous duct and lactiferous sinus: lined by stratifi ed squamous epithelium. Resting mammary gland At puberty, the mammary glands develop mainly by the eff ects of estrogens & progesterone. A-Estrogens: 1-growth of stroma. 2-deposition of fat. 3-proliferation of the ducts. 4-development of nipples. B-Progesterone: 1-Growth of the lobules. 2-Growth of alveoli (secretory units). III- Mammary gland during pregnancy Under the eff ects of high levels of estrogensandprogesterone,prol actina and human chorionic somatomammotropin: Proliferation and branching of the duct system+ Proliferation of the alveoli by budding from the intralobularduct massive growth of the breast. III-Mammary gland during pregnancy Late in pregnancy: well established lobules contain alveoli which begins to secrete clostrum (a serous fluid rich in protein and withlow fat) further enlargement of the breasts. IV- Lactating mammary gland Milk synthesis is stimulated by prolactin and chorionic somatomammotropinwhile milk ejection is caused by oxytocin The lobular pattern of the gland is very evident: with large number of the secretory alveoli contain milk. Reduction in the connective tissue stroma IV- Lactating mammary gland Milk secretion involves 2 modes of secretion: of 1Merocrinesecretion: protein, stored inside secretory granules and exocytosedat the apical part of the cell. 2Apocrine secretion: of lipid droplets, leave the cell with small amount of cytoplasm and surrounded by a part of the apical cell membrane. I. lactating mammary gland The myoepithelial cells: 1- Those surround the alveoli: are stellate, surround the secretory cells by their processes. Function: squeeze the alveol to push the milk from the lumen to the duct system IV- lactating mammary gland 2- Those surround the duct system: are spindle , oriented longitudinally along the ducts between the epithelium and basal lamina IV- mammary gland The alveoli of adjacent lobules may appear in diff erent grades of activity: 1- Groups of alveoli consist of high pyramidal cells with milk granules at the apical parts of the cells. 2- Another groups show milk accumulated in the lumen with sheding of the apical parts of the cells leaving cuboidal cells. IV- mammary gland 1Another groups from which the milk was suckled, leaves cuboidal cells with empty lumen. 2Another group show regenerating columnarcells but still without milk granules in their apical parts.  V-Mammary gland of menopause Involution of the glands, characterized by: 1- Stroma: atrophic changes with loss of collagen and elastic fibers. 2- Parenchyma: atrophy of the secretory portion and partly of the ducts. Hormones affect development of mammary gland Thank you ——