Hymen Vaginal orifice
(a and fo)The genital tubercle, urogenital fold, and labioscrotal folds that appear during the fourth week of development may differentiate into (c and d) male external reproductive organs or (e and f) female external reproductive organs.
The birth of a live, healthy baby is against the odds, considering human development from the beginning. Of every 100 secondary oocytes that are exposed to sperm, 84 are fertilized. Of these, 69 implant in the uterus, 42 survive one week or longer, 3 7 survive six weeks or longer, and only 31 are born alive. Of those that do not survive to birth, about half have chromosomal abnormalities that are too severe to maintain life. Table 23.1 summarizes the stages of prenatal development.
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.