Abstract
Twelve samples of mammary glands (6 immature and 6 lactating ewes) were used for this study. Specimens of glands were immediately dissected and fixed in 10% formalin sol. The specimens were processed according to paraffin technique, sectioned at 5-6µm and stained by hematoxylin and eosin, Masson's Trichrom stains. In both immature and lactating ewes the mammary glands were covered by skin. In immature ewes the mammary quarter was composed of few mammary lobes that separated by very thick inter lobar adipose tissue. The lactating quarter was composed of huge mammary lobes and lobules without adipose tissue. In immature the lobe was consisted of few small lobules that composed of few of mammary alveoli while the lactating lobes had large sizes lobules and each had large alveoli which lined by tall cuboidal cells and supported by fibrous tissue and myo epithelial cells. In both immature and lactating ewes, the gland and teat cisternae were showed many of mucosal folds which lined by pseudo stratified columnar epithelium and supported by fibrous connective tissue. The teat cisterna of both immature and lactating was composed three layers; mucosal cisterna, fibro muscular layer and skin. The teat canal was lined by pseudo stratified squamous epithelium and the sub epithelial connective tissue showed well developed venous sinus and fibro muscular. Statistical analysis was revealed significant differences between the values of all parameters of immature and lactating ewes. Apparent surface areas of the lobe in immature and lactating were 122143.063±23.21 µm2 & 992541.188±33.81 µm2 respectively. Surface areas of lobule in immature and lactating were 1042.938±21.02 µm2 & 91565.977±25.60 µm2 respectively. Surface areas of alveoli in immature and lactating were 994.238±11.39 µm2 & 4584.270±19.26 µm2 respectively. Epithelial heights of alveoli in immature and lactating were 10.290±1.01 µm & 23.012±2.81 µm respectively. Thickness of inter lobar tissue in immature and lactating ewes 677.393±23.67 µm and 361.401±10.86 µm respectively. Thickness of inter lobular connective tissue in immature and lactating were 112.969±±11.48 µm and 90.281±9.81 µm respectively.

Key words: mammary gland, ewes, immature, lactating, histological