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Mammary Cytology


Piglets suckling a sow.

Mammary Cytology Associated with Lactogenesis

The prelactating alveolar epithelial cells have an irregular shaped nucleus, minimal RER, a small inconspicuous Golgi, few microvilli at the apical surface, few mitochondria, and perhaps 1 or 2 fat droplets.

To the right is an electron micrograph of a nonlactating alveoli. Note the relative absence of RER, Golgi, etc.

Image of nonlactating bovine mammary tissue - transmission electon microscopy.

Immediately before and during parturition there is dramatic hypertrophy of the RER, hypertrophy of the Golgi, appearance of large vesicles containing casein micelles, release of granular material (casein micelles) into the lumen, an increase in the number of cytoplasmic fat droplets and their release into the lumen, an increase in the number of microvilli at the apical cell membrane, and an increase in the number of mitochondria per cell. Cell polarity becomes evident: the RER is primarily on the basal half of the cell, the nucleus is shifted to the basal portion of the cell, and the Golgi is apical to the nucleus.

To the right is an electron micrograph of a lactating epithelial cell (igher magnification than the one above). Note the large secretory vesicles (SV) and lipid droplets (LD), as well as the RER, microvilli (arrows), and other organelles characteristic of a lactating cell.

Image of lactating bovine mammary tissue - transmission electron microscopy.

See also the Mammary Structure - Independent Study Section on Mammary Microstructure for more on mammary cell ultrastructure.

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