Preface This course covers the basic topic of embryology, beginning with the female reproductive cycle, including the various factors that affect fertilization, and gametogenesis. Following that will be a variety of chapters that will cover the various development features that occur at different stages of the pregnancy. Chapter one will include a discussion of the female reproductive cycle, including the hormones involved in ovulation. There needs to be a progressive and orderly release of certain hormones in order to have ovulation. Ovulation is necessary for fertilization and for the continuation of a pregnancy. Chapter two will cover aspects of gametogenesis, including the way the egg cell develops in the female and the way the sperm cell develops in the male prior to fertilization. In actuality, there are similarities in the processes of meiosis in males and females, but there are significant differences as well. The third chapter of the course will include a discussion of fertilization, the formation of the zygote, the way a zygote transforms into a blastula, and the process of gastrulation, in which a disc-shaped embryo becomes a three-dimensional structure. In the fourth chapter of the course, we will have a discussion of how twins are made. There are two types of twins. Identical twins come from the same egg cell, while fraternal twins are the result of a woman ovulating two eggs at the same time and having both of those eggs fertilized by separate sperm. The fifth chapter of the course will involve a discussion of the placenta and how it forms. There are tissues separate from the embryo itself that burrow into the uterine wall and differentiate to become the human placenta that carries forth throughout the pregnancy and nourishes the fetus. In chapter six, there will be a thorough discussion of the second week of embryogenesis. It is during this time that embryo is disc-shaped and begins to develop from a few cells into a trilayered organism. Cells begin to differentiate into the ectoderm, the mesoderm, and the endoderm. In the seventh chapter of the course, the way the embryo develops into a three-dimensional structure will be the focus of the discussion. During this time, some of the earliest organs begin to develop, with the circulatory system developing first.
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