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The study of prenatal development provides many clues for
understanding the physiology as well as the pathogeny of
malformations and many diseases. I became interested in the
analysis of human development as a young medical student more than
30 years ago, and I have stayed in this field all my life. In my
studies, I always tried to compare the events of different
disciplines such as genetics, anatomy, bio chemistry and
physiology. I learned that the development of a structure is, under
normal circumstances, strictly determined and that the development
of structures always precedes their proper function. There are no
changes in function without changes in structure. The life of every
cell is genetically preprogrammed and the program may be modified
by complicated interactions with environment. Recent progress in
our knowledge is basicly related to technology. However, using all
the tools of today's technology, we are still unable to understand
the basic normal development. After almost thirty years of work, I
am trying to present a subjective review of the development of the
human endocrine glands. I am presenting an image emerging from my
experience. I personally studied several hundred human embryos
using mostly anatomical, histochemical and some biochemical
techniques. I found much additional information in the literature."
A little picture is worth a million words. Chinese proverb Prenatal
human development is an extremely complicated process related to
genetics, biochemistry, anatomy, and physiology. There are no
developmental changes, either chemical or morphologic, without
simultaneous changes in molecular organization. The astonishing
buildup ofbiostructures always precedes their proper function. The
development of an embryo is genetically coded and is based on
interactions related to the selective switching on and off of
genes. Interactions are cell-to-cell mediated, mediated by
extracellular fluids, or mediated by special pathways. Every
substance involved in developmental is to be recognized by its
target. interactions, before triggering a metabolic or a
morphogenic event, Complex physical and immunologic recognitions
are involved in the process of differentiation. Small pieces of
evidence are collected to create a mosaic picture elucidating the
development. This picture is fascinating and represents the biggest
biological puzzle: the puzzle of development. There is no doubt
that analysis of human prenatal development is a basis for
understanding normal and pathologic relationships between structure
and function. Today, there are approximately 2000 different inborn
congenital anomalies and syndromes. This book attempts to present a
complete realistic account of human morphogenesis, the
differentiation of structures, using direct photographs of normal
specimens obtained from legal medical abortions of unwanted
pregnancies. Emphasis has been placed on contemporary techniques:
histochemistry and scanning electron microscopy. The text is as
simple as possible; meticulous detailed anatomic descriptions have
been omitted.
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