Mammary Gland (2nd Year) PDF

Mammary Gland Dr. Ereny Fekry Lecturer of Histology Mammary Gland Mammary gland is an exocrine compound tubuloalveolar gland.  They are of the same structure in both sexes. In females:  by the onset of puberty the breasts develop by the effect of hormones. Female mammary gland enlar...

Mammary Gland Dr. Ereny Fekry Lecturer of Histology Mammary Gland Mammary gland is an exocrine compound tubuloalveolar gland.  They are of the same structure in both sexes. In females:  by the onset of puberty the breasts develop by the effect of hormones. Female mammary gland enlarges under effect of estrogen due to accumulation of adipose C.T. + branching of duct system  Full development occurs at about 20 years of age, with minor cyclic changes during each menstrual period.  Major cyclic changes during pregnancy & lactation, in which mammary gland assume its full morphologic and functional state.  Atrophy occurs after the age of 40 and throughout menopause.  Male breast: Rudimentary system of simple ducts and small amount of C.T. Occasionally, it enlarges slightly at puberty due to accumulation of adipose tissue. However, this enlargement is usually minimal, self-limited and reversible. Structure of the Mammary Gland Mammary Gland Parenchyma Stroma Alveoli + Duct( )C.T septa( )system A) Stroma: 1-Inter-lobar septa: From reticular layer of dermis, straight ,complete regular septa of dense irregular C.T extend back to the deep pectoral fascia dividing the substance of each breast into 15-20 separate lobes. 2- Inter-lobular septa: From the interlobar septa ,thinner, incomplete irregular interlobular septa extend into the substance of the lobes dividing them into inter communicating lobules Contain adipose tissue. 1+ 2 called suspensory ligament of Cooper. 3- Intralobular CT: Loose CT From papillary layer of dermis. In the interior of lobules, surround the parenchyma Structure of the Mammary Gland Mammary Gland Parenchyma Stroma Duct system +( )C.T septa( )Alveoli B) Parenchyma: (Duct system + Alveoli) a) Duct system: o The gland consists of 15 to 20 lobes radiating out from the nipple and separated from each other by C.T. o In each lobe the intralobular ducts collect to form single lactiferous duct. o Each lobe is drained by its own lactiferous duct leading directly to the nipple, where it opens onto the surface (12-20 small terminal openings of the lactiferous ducts). o Before reaching the nipple, each duct is dilated to form a lactiferous sinus then narrows before passing through the nipple. In the resting state: 1. Intra-lobular duct (smaller duct): Lined by simple columnar epithelium. 2. Lactiferous sinus & Lactiferous duct leading to it: are lined by stratified cuboidal epithelium. 3. Lactiferous duct near the opening at the nipple: lined by stratified squamous keratinized epithelium. Structure of the Mammary Gland Mammary Gland Parenchyma Stroma Duct system +( )C.T septa( )Alveoli  b) Alveoli (secretory unit): o Mammary glands are activated by elevated surges of estrogen & progesterone during pregnancy to become lactating. o At this time, the terminal portion of the duct branch and grow and the alveoli develop and mature.  L.M  E.M  Process of secretion (lipids & protein).  L.M:  The alveoli of lactating MG are composed of cuboidal cells partially surrounded by a meshwork of stellate myoepithelial cells.  Nucleus: single, rounded & vesicular.  Cytoplasm: vacuolated, with basal basophilia.  Milk appears in their lumen as vacuolated acidophilic secretion. E.M: Several Golgi complexes, abundant rER (for protein synthesis), mitochondria, Abundant SER, many lipid droplets (lipid synthesis), and numerous vesicles containing milk proteins and lipids. Accordingly, the secretions of alveolar cells are of 2 kinds: 1. Lipids: a) Lipids are stored as spherical droplets in the cytoplasm of the alveolar cell. b) Small droplets coalesce to form larger and larger droplets that move to the periphery of the cell. c) The droplet become enveloped with a portion of the apical cell membrane (cytoplasmic bleb, that consists of a central lipid droplet, surrounded by narrow rim of cytoplasm and enclosed by a plasmalemma). d) Finally, these droplets pass out into the lumen by apocrine mode of exocytosis. 2. Proteins: Large amounts of proteins are made on rough endoplasmic reticulum, processed through the Golgi appratus and packaged into secretory vesicles which secreted from the apical end of the cell by merocrine mode of exocytosis. Colostrum: The first secretion of the mammary gland after delivery. Protein rich fluid.  Milk: A fluid containing proteins, lipid, lactose, lymphocytes, monocytes, antibodies, minerals and fat-soluble vitamins.  The nipple, is a protuberance (conical raised area) covered by stratified squmaous epithelium, containing 12-20 small terminal openings of the lactiferous ducts. Its core is composed of dense collagenous connective tissue with elastic fibers and smooth muscle cells. Covered by pigmented skin, richly supplied by sensory nerveendings.  The areola, is a pigmented skin around the nipple, contains sweet gland, and areolar glands; Montgomery glands (modified sebaceous glands), producing lubricating and protective secretion that discourage microbial growth. During pregnancy and lactation, increased melanin pigmentation occurs with enlargement of Montgomery glands.  Difference between lactating & resting MG:  Lactating MG:  Stroma : 1. Thin fibrous septa 2. Little or no fat 3. Reduced intralobular C.T.  Well developed parenchyma: as pregnancy progresses, the breasts enlarge as a result of hypertrophy of the glandular parenchyma and engorgement with secretion: 1. Well developed duct system, the terminal portions of the ducts branch and grow. 2. Well developed numerous alveoli, that develop and mature. 3. Alveoli that show signs of secretory activity (well developed cell organelles) & become distended with secretion.  Resting MG: Has the same basic architecture as the lactating MG, except that it is smaller and:  Well developed stroma: 1. Thick interlobar and interlobular dense CT septa. 2. Good amount of fat cells in the subcutaneous tissue, interlobar & interlobular septa. 3. Lobules are filled with loose cellular intralobular CT.  Parenchyma: 1. Duct system only. 2. NO developed alveoli. Hormonal Control of the Breast  Estrogen: Responsible for breast enlargement at puberty by accumulation of adipose C.T. & branching of the duct system.  Estrogen + progesterone + human chorionic somatomammotropin: Responsible for development of alveoli and increase in breast size during pregnancy.  Prolactin: Responsible for start of milk secretion from alveoli during lactation.  Oxytocin: Responsible for stimulating contraction of myoepithelial cells surrounding alveoli & ducts squeezing milk secretion towards duct system. Post-lactational changes: After weaning, alveoli undergo degeneration and dead cells are removed by macrophages and breast returns to resting state. Colostrum: First secretion of mammary gland after delivery. It contains less lipids, more proteins and is rich in antibodies (mostly IgA) that provides some degree of passive immunity for the newborns. It also contains minerals and fat- soluble vitamins. Milk: Fluid containing proteins, lipid, lactose, lymphocytes, monocytes, antibodies, minerals and fat-soluble vitamins. Breast cancer in females ranks first in Egypt. Early detection via self-examination, mammography and early treatment improve the prognosis and significantly reduced mortality from breast cancer. Difference between resting & lactating MG Resting MG Lactating MG  1 2 Identif Identif y? y?