Fertilized ovum

After insertion of an lUD, polymorphonuclear leukocytes and macrophages accumulate in the uterine cavity. These cells appear to phagocytize sperm and Hberate a blastotoxic toxin (92,93). Intrauterine devices also may create a hostile environment, perhaps because antibodies are produced that interfere with implantation of the fertilized ovum (93). 

Ectopic pregnancy Presence of a fertilized ovum outside the uterine cavity. 

Contraception is the prevention of pregnancy following sexual intercourse by inhibiting sperm from reaching a mature ovum (i.e., methods that act as barriers or prevent ovulation) or by preventing a fertilized ovum from implanting in the endometrium (i.e., mechanisms that create an unfavorable uterine environment). 

IUDs cause low-grade, intrauterine inflammation and increased prostaglandin formation. In addition, endometrial suppression is caused by the progestin-releasing IUD. They are spermicidal and also interfere with implantation of the fertilized ovum. Efficacy rates are greater than 99% with both perfect use and typical use. 

With the exception of certain viruses, the blueprint for all organisms is contained in code by deoxyribonucleic acid (DNA), a giant macro-molecule whose structure allows a vast amount of information to be stored accurately. We have all arisen from a single cell, the fertilized ovum containing two sets of DNA (packaged with protein to form chromatin), one set from our mother, resident in the nucleus of the unfertilized ovum, the second set from our father via the successful sperm. Every cell in the adult has arisen from this one cell and (with the exception of the germ cell and specialized liver cells) contains one copy of these original chromosome sets. 

Transgenic animals are produced by transferring cDNA into the pronucleus of a fertilized ovum. The resultant transgenic animal has the new gene (transgene) in all of its cells including its reproductive tissues. Transgenic animals are now widely used as experimental models in which to study human diseases. 

Progestins, of which progesterone is a prime example, induce endometrial maturation following ovulation, setting the stage for implantation of a fertilized ovum and pregnancy ... 

Preparation of endometrium for the implantation of fertilized ovum for further pregnancy. 

Inducing other changes in the uterine mucosa which may be unfavourable for the implantation of fertilized ovum. This action is important in minipills and postcoital pills. 

Implantation Attachment of the fertilized ovum (blastocyst) to the endometrium and its subsequent embedding in the compact layer, occurring 6 or 7 days after fertilization of the ovum. 

It plays a role in the implantation of the fertilized ovum in the uterus. 

Preventing implantation of the fertilized ovum should fertilization take place (Figure 61.8)... 

It is not known whether the predominant eflFect in the human female is interference with sperm physiology, fertilization, ovum transport, or nidation. Greater quantities of the glycoprotein which accumulates on all lUD surfaces should be isolated for use in studies to determine specifically which reproductive processes are inhibited. 

Corpus luteum—The site on the ovary from where the ovum was released the corpus luteum then releases hormones to prepare the endometrium for implantation of the fertilized ovum. 

Endometrium—The blood-rich interior lining of the uterus, where implantation of the fertilized ovum occurs. 

It has been suggested that the use of caffeine to improve the mobility of human sperm used in artificial insemination may be very risky, owing to the potential for chromosome damage and also possible damage to the fertilized ovum (SEDA-5, 32). 

Fig. 97.—A, Immature angiospermous ovule B, same, after embryo-sac e.s). has matured to form the female gametophyte nucellus nuc) outer integument (0. int) inner integument (t. int) embryo sac e.s.) micropyle mic) chalaza ch) funiculus (/) synergids s) ovum (0) polar nuclei p) antipodals a) C, fertilized and matured angiospermous ovule (seed). Note that the nucellus nuc) has been pushed out by the encroachment of the embryo sac, in which endosperm has formed by the fusion of the two polar nuclei with the second sperm nucleus from the pollen tube which has later divided to form numerous nuclei scattered about in the protoplasm of the embryo sac and accumulated protoplasm and laid down walls, within which nourishment was stored embryo em) from fertilized ovum testa t) from outer integument tegmen te) from maturation of inner. integument micropyle mic) hilum or scar (h), after funiculus became detached.

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