GENITAL ORGANS OF THE SOW 



521 



Each teat has a single duct which widens superiorly and opens freely into a 

 roomy lactiferous sinus or milk cistern (Sinus lactiferus). The lactiferous duct 

 or teat canal is linetl by a glandless nmcous membrane which is covered with 

 stratified squamous epithelium; the lower part (ca. 1 cm.) of the canal is narrow, 

 and is closed by a sphincter of unstriped muscle. The mucous membrane of 

 the sinus forms numerous folds which render the cavity multilocular. 



Vessels and Nerves. — The blood-supply is derived from the external pudic 

 arteries. The veins form a circle at the base of the udder, irom which the blood 

 is drained by three trunks, viz., the very large subcutaneous abdominal ("milk 

 vein"), the external pudic, and the perineal vein. The lymphatics are numerous, 

 and pass to the supramammary glands cliic^fiy. The nerves are derived from the 

 inguinal nerves and the posterior mesenteric plexus of the sympathetic. 



GENITAL ORGANS OF THE SOW 



The ovaries are concealed in the bursa ovarii, owing to the large extent of the 

 mesosalpinx. Tliey are more rounded than in the bitch, and have a distinct hilus. 



Fig. 417. — Genital Organs of Sow, Dorsal View. The Vagina and Cervix Uteri are Slit Open. 

 1, Labia vulvae; 2, glans clitoridis; 3, vulva; 4, external urethral orifice; 5, vagina; 6' , cervix uteri; 6, 

 corpus uteri; 7, cornua uteri, one of which is opened at 7' to show folds of mucous membrane; 8, Fallopian tube; 

 5', abdominal opening of tube; 9, ovaries; iO, ovarian bursa; i 7, broad ligaments of uterus; i^, urinary bladder. 

 (From Leisering's Atlas.) 



They are situated usually as in the cow, but their position is quite variable in 

 animals which have borne young. The surface commonly presents rounded promi- 



