PLACENTA 



272 



PLACENTA 



in maintaining gestation and regulating 

 maternal metabolism. 



In view of the manifold functions of 

 the placenta, which surpass in number 

 those of any other organ, it is not 

 surprising to find that it gives a great 

 many cytological and histochemical 

 reactions. Despite the variety of these, 

 none of them is specific for the placenta 

 alone. The placenta in this respect 

 differs, for example, from brain where 

 for various neuronal and glial elements 

 a variety of special cytological tech- 

 niques has been developed. 



For a general understanding of the 

 comparative anatomy and phylogeny 

 of the placenta, consult Grosser O. 

 (Frlihentwicklung Eihautbildung und 

 Placentation des Menschen und der 

 Saugetiere, 1927) Bergmann, Munich, 

 and Mossman, H. W. (Carnegie Contrib. 

 to Embryol., 1937, 26, 129-246). See 

 also the chapter by E. C. Amoroso on 

 Placentation in the forthcoming 3rd 

 edition of Marshall's Physiologj^ of 

 Reproduction. For the placentation 

 of the Primates consult Hill, J. P. 

 (Phil. Trans. Roy. Soc. Lond. Ser. B., 

 1932, 221, 45-78), Wislocki, G. B., and 

 Streeter, G. L. (Carnegie Contrib. to 

 Embryol., 1938, 27, 1-66) and Stieve, 

 H. (Ztschr. f. mikro-anat. Forsch., 1944, 

 54, 480-543). Various aspects of the 

 topography, growth and vasculariza- 

 tion of the human placenta are de- 

 scribed by Spanner, R. (Morph. Jahrb., 

 1935, 75, 374-392) and Ztschr. f. Anat. 

 u. Entwicklungsgesch., 1936, 105, 163- 

 242) and Stieve, H. (Ztschr. f. mikro- 

 anat. Forsch., 1940, 48, 287-449). 



Interest in placental cytology and 

 histochemistry was initiated by Hof- 

 bauer (Biologie d. menschlichen Pla- 

 zenta, 1905, Braumiiller, Vienna and 

 Leipzig) who investigated the placental 

 assimilation of iron, protein and fats 

 in man, and by Edwin Goldmann 

 (Beitrage z. klin. Chir., 1912, 78, 1-108) 

 who studied extensively the distribu- 

 tion and significance of glycogen, fat, 

 iron and hemoglobin in the placentas 

 and fetuses of mice and rats. 



In the past two decades with the de- 

 velopment of many new cytological 

 and histochemical methods, interest 

 in the placenta has been rekindled. 

 The human placenta has been investi- 

 gated by a variety of histochemical 

 techniques for the demonstration of 

 various proteins, carbohydrates, lipids, 

 enzymes and inorganic compounds. 

 Wislocki, G. B. and Bennett, H. S. 

 (Am. J. Anat., 1943, 73, 335-449) have 

 described the presence in the tropho- 

 blastic syncytium of birefringent, su- 

 danophilic droplets which react with 



phenylhydrazine and which are soluble 

 in acetone, and they concluded that 

 these reactions indicate the site of 

 formation of placental steroid hor- 

 mones. The Liebermann-Burchardt re- 

 action, the Schiff reaction and the 

 property of autofluorescence have been 

 introduced as further means of charac- 

 terizing placental steroid hormones in 

 histological sections (Dempsey, E. W. 

 and Wislocki, G. B., Endocrin., 1944, 

 35, 409-428). These investigators also 

 describe glycogen, revealed by Best's 

 carmine and Bauer's method, and iron, 

 demonstrated by both the Turnbull 

 blue reaction and microincineration. 

 The distribution of acid and alkaline 

 phosphatases has been explored (Demp- 

 sey, E. W. and Wislocki, G. B., Am. J. 

 Anat., 1947, 80, 1-33) by using Gomori's 

 methods with a variety of substrates 

 (glycerophosphate, fructose diphos- 

 phate, nucleic acid, adenylic acid and 

 lecithin) . Mucopolysaccharides as well 

 as glycogen have been investigated by 

 McManus' periodic acid-Schiff reaction, 

 metachromatic substances by their 

 responses to toluidin blue after basic 

 lead acetate fixation and lipids with 

 sudan black B (Wislocki, G. B. and 

 Dempsey, E. W., Am. J. Anat., 1948, 

 83, 1-30). The affinity of syncytium, 

 fibrin and fibrinoid of the human 

 placenta for acid and basic dyes has 

 been studied (Singer, M. and Wislocki, 

 G. B., Anat. Rec, 1948, 102, 175-193). 

 A basophilic substance abundantly 

 present in syncytium and cytotropho- 

 blast and digested by crystalline ribo- 

 nuclease has been identified as ribo- 

 nucleoprotein (Dempsey, E. W. and 

 Wislocki, G. B., Am. J. Anat., 1945, 

 76, 277-301). Some of the functional 

 activities of the placental trophoblast, 

 as revealed by histochemical studies, 

 have been summarized (Wislocki, G. 

 B., Dempsey, E. W. and Fawcett, D. 

 W., Obstet. and G}^. Survev, 1948, 3, 

 604-614). 



Our knowledge of the trophoblastic 

 cell columns and shell and of the basal 

 plate, as well as of the relationships of 

 of these structures to the underlying 

 basal decidua in the human placenta 

 has been materially advanced by the 

 use of cytological and histochemical 

 methods (Wislocki, G. B. and Bennett, 

 H. S., 1943, I.e.; Wislocki, G. B. and 

 Dempsey, E. W., 1948, I.e.). By these 

 means two types of cytotrophoblast 

 can be distinguished from the elements 

 of the maternal decidua (Wislocki, 

 G. B., Proc. Am. Assn. Anat., 1951). 



Tissue cultures of young human 

 placentas containing actively growing 

 cytotrophoblast produce gonadotropic 



