14 



BIOLOGY OF EGGS AND IMPLANTATION 



Richard J. Blandau, Ph.D., M.D. 



PROFESSOR OF ANATOMY, UNIVERSITY OF WASHINGTON SCHOOL OF MEDICINE, SEATTLE, WASHINGTON 



I. Introduction 797 



II. Methods 798 



A. Methods for Recovering Mammalian 



Eggs and Embryos 798 



1. Collecting ova from the oviducts. . 798 



2. Collecting free ova from the uterus 798 



3. Recovery of attached embryos. . . . 799 



B. Egg Culture and Preservation in 



Vitro 799 



C. Intraspecific Egg Transfer 800 



D. The Production of Eggs by Superovu- 



lation " 801 



III. Biology of the Mammalian Egg 802 



A. Oogenesis 802 



B. Growth, Composition, and Size of the 



Mammalian Egg 807 



C. Egg Membranes 811 



1. The zona pellucida 811 



2. The mucous or "albuminous" layer 815 



D. The First Maturation Division ...... 81G 



E. The Ovulated Egg 817 



F. Respiratorv Activity of Mammalian 



Eggs. . .". : 818 



G. Transport of Tubal Ova 819 



IV. Fertilization and Implantation 827 



A. The Cumulus Oophorus and Sperm 



Penetration 828 



B. The Zona Pellucida and Sperm Pene- 



tration 832 



C. Sperm-Egg Interacting Substances.. 834 



D. Sperm Penetration of the Vitelline 



Membrane 834 



E. Fertilization in Vitro 835 



F. Fate of the Unfertilized Egg 83(i 



G. Formation of the Second Polar Body, 837 

 H. Pronuclei Formation, Syngamy, and 



First Segmentation Division 838 



I. Fate of the Cytoplasmic Components 



of the Fertilizing Sperm Flagellum. 841 

 J. Supernumerary Spermatozoa and 



Polyspermy in Mammalian Ova. . . 844 

 K. Stages of Development and Location 



of Eggs 845 



L. The Age of the Elgg at the Time of 



Fertilization 848 



M. Implantation 850 



N. Spacing and Orientation of Ova in 



Utero 852 



O. Blastocyst Expansion 858 



P. Embryo-endomet rial Relationships . . 860 

 V. References 8(i5 



797 



I. Introduction 



In recent years there has been much more 

 intense research activity on the morphology, 

 physiology, and biochemistry of sperma- 

 tozoa and semen of mammals than on their 

 eggs and the fluids forming their environ- 

 ment. The significant increase in the in- 

 vestigations of the male gametes is due 

 largely to stimuli resulting from the neces- 

 sity of perfecting techniques of artificial 

 insemination in domestic animals and of 

 elucidating the problems of infertility and 

 contraception in man. A distinct advantage 

 with respect to investigations of the male is 

 the ready availability and large number of 

 gametes which can be obtained from a 

 single subject. In contrast, the mammalian 

 egg is available in restricted numbers and 

 then only at very specific times in the re- 

 productive cycle. Furthermore, there are 

 very real difficulties in maintaining mam- 

 malian eggs in a normal physiologic state 

 after they have been removed from their 

 usual environment. 



Even though there have been notable ad- 

 vances in the investigations of the compli- 

 cated physiologic and biochemical mecha- 

 nisms which exist in the development, 

 storage, transport, and syngamy of the 

 gametes since Dr. Carl G. Hartman's erudite 

 discussions of the subject in 1932 and 1939, 

 our understanding of the fundamental prob- 

 lems involved in maintaining the continuous 

 stream of life from generation to generation 

 is still in its infancy. As we proceed 20 years 

 later, it will be clear that the older methods 

 of classical histology have not yet outlived 

 their usefulness. But it will also be ap- 

 parent that many of the advances which 

 have been made, particularly in the in- 

 vestigation of mammalian materials, can 



