Question

state the change that takes place inthe neutras a) in a plantation of embroyo has occured b) female gemetes is not fertilized

Answer 1

This review of vertebrate placental structure attempts to integrate some of the considerable body of work done using electron microscopic and other techniques since Amoroso’s classic 1952 chapter. The reference list concentrates on the most recent work. Mossman (1987) provides the best comprehensive list of placental references. This chapter is mainly concerned with providing data to facilitate broad comparisons of structures and secretions both during development and in their final form with a view to relating them to the functional activity of the placenta. The remarkably wide variety of structures in the mature placenta develops from a basically similar repertoire of extraembryonic membranes as typified in the amniote egg, and the diversity can be further simplified by use of straightforward structural criteria. The major problem is to relate those criteria to the wide range of functions served by the placenta. A few non-amniotes have developed analogous structures which serve similar functions to the extraembryonic membranes, and these offer further insights into the requirements for successful fetal development (Hagan, 1951; Woollacott and Zimmer, 1975; Amoroso et al., 1979; Bone et al., 1985).