Findings

At low magnification, several lobules of an active mammary gland during early pregnancy are shown. Secretory alveoli are numerous and enlarged with secretory products that can also be seen in ducts as well. Note the large excretory duct surrounded by dense interlobular connective tissue.

Comment

During pregnancy, estrogen and progesterone produced first by the corpus luteum, and then by the placenta induce ductal epithelium of the inactive gland to proliferate, enlarge, branch and form numerous secretory alveoli at the expense of interlobular connective tissue and adipose tissue. Alveoli initially secrete colostrum, a product rich in protein but not fat. Soon after parturition, alveoli secrete milk, a fluid rich in sugar, proteins and fat.

Preparation

Paraffin section, hematoxylin and eosin

View

Low-power light microscopy

Specimen

Mammary gland

Image Credit

V. Eroschenko, Ph.D.
Department of Biological Sciences
WAMI Medical Program
University of Idaho