| Popis: |
The mammary glands of rats during and after lactation were examined by scanning electron microscopy.In the lactating mammary gland the luminal surface of the secretory epithelial cells were covered with microvilli, relatively sparse and short, and characterized by the presence of two distinct types of secretory materials: large lipid droplets with varying grades of protrusion and small protein granules randomly distributed. Fracture of the secretory epithelial cells revealed both the the presence of a connection of the protruding lipid droplet to the apical cytoplasm by a thin bridge, and openings of holes containing protein granules into the alveolar lumen.After weaning, the mammary alveoli underwent gradual and progressive involution. Three to seven days later, the luminal surface of the secretory epithelial cells became irregularly undulated and almost completely lost either their protruding lipid droplets or protein granules. Occasionally, necrotic secretory epithelial cells with exploded cytoplasm were detached from the adjacent cells. By the 10th day, involution of the mammary gland was further advanced. A marked collapse of the alveoli was noticed associated with focal luminal obliteration. |
