Physiology of Fertilization in Mammals

Abstract

ERTILIZATION, the union of ova and spermatozoa, takes place internally in mammals. The spermatozoa are ejaculated into the vagina and transported to the upper part of the fallopian tubes where fertilization occurs. Thus our knowledge of fertilization is far less advanced in mammals than in lower forms due to the difficulty of physiological experimentation in vitro. The physiology of ferti-lization in mammals, however, can be analyzed on the following bases: the physio-logical integrity of spermatozoa and ova capable of fertilization, their transport, the proper time of their meeting, the mechanism of sperm penetration into the ova, the formation and union of male and female pronuclei, and the activation as well as the segmentation of the fertilized ova. The reader is referred to reviews by Anderson (12) on mammalian spermatozoa, Mann (200) on the metabolism of semen, Pincus (237) on mammalian ova, Hartman (146,148) on the physiology of sperm and ova, Asdell (14) on fertilization in different species, and Hammond (132) on the fertility of mammals. PHYSIOLOGY OF SPERMATOZOA IN RELATION TO FERTILIZATION