HISTOLOGY 155 



spindles form and atypical, parthenogenetic development occurs. The 

 antra fill with blood and later the granulosa cells hypertrophy to form 

 corpora lutea atretica around the degenerating ova. 



According to Engle (34), "A count of atretic follicles at four stages of the 

 estrous cycle shows that there is a cyclic variation, both in the number of 

 pseudomaturation spindles and in the total number of atretic follicles. The 

 destruction is at its highest point during the first day of the diestrum, and at 

 its lowest on the second day." 



The oviduct. — The oviduct is often called the uterine tube or Fallopian 

 tube. It is a narrow, coiled tube which connects the periovarian space 

 with the uterus. The part nearest to the ovary, called the ampulla, ends 

 in a funnel-shaped opening, the infundibulum (Fig. 76). The fringe-like 

 edges of the ampulla, the fimbriae, extend into the periovarian space. The 

 ampulla is continuous with the narrow isthmus, while the distal end of the 

 oviduct, the intramural part, runs for a short distance within the wall of 

 the uterus entering the lumen slightly eccentrically (pars interstitialis). 

 Simple columnar epithelium lines the entire length of the lumen of the 

 oviduct. In the ampulla these cells are tall, possess centrally located 

 oval-shaped nuclei, strongly acidophilic cytoplasm and long motile cilia. 

 Scattered among these cells are some non-ciliated club-shaped cells, which 

 at certain phases of the estrous cycle protrude into the lumen (2). There 

 is a short transitional zone between the ampulla and the isthmus, where 

 ciliated and non-ciliated cells intermingle. The latter gradually prevail, 

 and the rest of the oviduct is lined by low columnar cells without cilia. 



The lamina propria consists of fibrous connective tissue. The mucous 

 membrane of the ampulla forms narrow, high longitudinal folds. In the 

 isthmus a few broad, low folds are present, while in the intramural part the 

 folds are again somewhat higher. The muscular coat, which is formed by 

 circularly arranged smooth muscle fibers, surrounds the mucous membrane. 

 It is progressively better developed toward the intramural part. The tube 

 is surrounded by a serous membrane which attaches it to the mesotubarium. 

 As the intramural part of the oviduct enters eccentrically into the lumen of 

 the uterus, it forms a papillary projection, the colliculus tubarius (Fig. 76). 

 The projecting colliculus tubarius and encirchng sulcus make difiicult the 

 injection of fluid into the oviduct from the uterus. 



Uterus. — The uterus is composed of two horns which join to form an 

 undivided caudal part, the corpus uteri (Fig. 75). The lumen of the uterine 

 horn is lined by simple, columnar cells. Projecting down from the lumen 

 are simple branched tubular uterine glands which are lined by low columnar 



