TISSUE TRANSPLANTATION TECHNIQUES 



APPLIED TO THE PROBLEM OF THE 



AGEING OF THE ORGANS OF REPRODUCTION 



P. L. KrOHN, B.A., B.M., B.Ch. 

 Department of Anatomy, University of Birmingham. 



The interpretation that is attached to the word "ageing" 

 depends very much on the particular tissue whose cells are 

 ageing. An individual neurone in the central nervous system, 

 for example, may divide by mitosis until the end of the first 

 year of life; it may increase in size later in life, and it is also 

 capable of regenerating a new piece of fibre if its axon is cut. 

 An unknown proportion of such cells dies as time goes on, 

 but seemingly none of them are ever replaced. The compon- 

 ents of other tissues, such as skin or the epithelium of the gut, 

 are continually being replaced and the cells that one sees in 

 an old animal are, therefore, not old in the way that neurones 

 are old, for they may just have been formed by the most 

 recent of a series of cell divisions which stretch back into 

 childhood and earlier. 'Both tissues have aged but the 

 individual cells that make up the tissues have not both aged 

 in the same way. 



Other types of specialised tissue, e.g. the mammary gland 

 or the uterus, undergo cycles of activity during the life of an 

 individual. The cells grow, mature, function, become atrophic 

 or senile and then after an interval for recuperation may 

 repeat the series of changes. The functional capacity of the 

 tissue alters as its experience of stimulation by hormones 

 increases with each cycle of activity. For the mammary 

 gland this is demonstrated by the increasing amount of milk 

 which is produced in successive lactations. The previous 

 experience of the uterus to hormone also conditions its^ 

 subsequent sensitivity to further stimuli. 



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