VAN 211: Veterinary Histology and Embryology (2+2)

MAMMARY GLANDS

• The mammary gland is a compound tubuloalveolar gland. The capsule is fibroelastic and from the capsule, tough connective tissue septa containing elastic fibres, smooth muscle and adipose tissue enter the gland and separate the gland into lobes and lobules.
• The amount of inter lobular connective tissue varies considerably with the functional status of the gland, being greatly reduced in a lactating gland.
• The parenchyma consists of secretory tubules with alveoli lined by short columnar or cuboidal epithelium resting on a delicate basement membrane.
• The appearance of epithelium depends on the phase of secretion.
• During the onset of milk formation the granular cells are taller and show fat globules at the luminal end.
• After extrusion of secretion, cells become flattened because the apical portions are cast off as secretion (apocrine gland).
• The cell borders are indistinct. In a lobule, alveoli in different phase of secretion may be seen, with high or flattened epithelium.
• Ducts: (lactiferous ducts) smallest ducts are lined by secretory epithelium. Larger ducts by columnar and still larger ones by two-layered columnar epithelium. Towards the termination there is stratified squamous epithelium.
• Non-functional gland: Shows abundant interstitial connective tissue. Parenchyma shows only ducts and few alveoli.