Some Historical Elements On Embryology

FETUS Essential elements of embryology

FETUS

This Publication is in its18th year

FETUS Essential elements of embryology

16th Edition ABEDUR RAHMAN MBBS (DMC), M Phil (Medical Science) Post Graduate Training in Heart Diseases

Editorial Assistant Dr. Farzana Iqbal Some historical elements on embryology

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FETUS Published by Afrazul Haque Bhelejan Thakurgaon On behalf of Fetus Publications First published………. September, 1991. Second Edition………. September, 1993. Third Edition………. February, 1995. Fourth Edition………. September, 995. Fifth Edition………. January, 1997 Sixth Edition………. May, 1998 Seventh Edition………. March, 2000 Eighth Edition………. August, 2000 Ninth Edition………. May, 2002 Tenth Edition………. October, 2003 Eleventh Edition………. April, 2004 Twelfth Edition………. December, 2004 Thirteenth Edition………. February, 2006 Fourteenth Edition………. October, 2006 Fifteenth edition ………. January 2008 Sixteenth edition ………. December 2008

© MD. ABEDUR RAHMAN AII rights reserved. No part of this book may be reproduced or transmitted in any form or by any means without the written permission of the author.

Cover Design: Abedur Rahman Price: Taka Two hundred and sixty (260/=-) only. For all kinds of correspondence DR ABEDUR RAHMAN Phone: 01819-050041

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Dedicated to My father for the uncompromising principle of his life.

ACKNOWLEDGEMENTS I remember  Dr. A. Hye Fakir EX-Head of the department of anatomy, BSMMU.  Dr. Habibur Rahman. Some historical elements on embryology

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FETUS EX Head of the department of anatomy, SBMC  Dr. Shahid-UlIah EX-Head of the department of anatomy, RPMC  Dr. Kazi Rafiqul Haque Head of the department of anatomy, USTC. Chittogong  Late Dr. S.S. Banik. Ex-Associate Professor of anatomy, SSMC.  Dr. Motahar Hossain. Ex-Head of the department of anatomy, DMC.  Dr. Manjar-e-Shamim. Professor & Chairman of the department of anatomy, BSMMU.  Dr. Shamim Ara Head of the department of anatomy, DMC  Dr. Shafiq Haider Asst prof. of anatomy, CMC. for their good wishes to this publication  Dr. Nazrul Islam

Ex Head of the department of anatomy, SBMC  Dr. Rubaiual Morshed

Ex Asst. Professor, Pediatric Surgery, DMCH for their kind efforts in revising this book. I want to acknowledge my students Sristi (K-63, DMC) and Juthy (K-63, DMC) for their whole hearted co-operation in editing this 15th edition of the book; Ilias (K-62, DMC), Jewel(K-63, DMC), Pritom (K-63, DMC), Fauzia (NUB) for their constructive criticism for making necessary correction of in this edition. I am also grateful to the doctors and students of different institutions and medical colleges who made constructive criticism to make the book more helpful for the embryology students.

FOREWORDS Excellent one I have gone through the book and found that the author has been succeeded in presenting the essential elements of embryology in an excellent manner. The elements served here are authentic. I hope that this humble presentation will serve its Dr. Md. Nazrul Islam purposes well. My best wishes go to the author. MBBS, M. Phil (DU) 32 MS (Glasgow), MHPED Some historical elements on embryology (Australia) Principal and head of the dept. Of Anatomy Dinajpur Medical

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Really charmed to find the simplicity I have gone through the book Fetus by Dr. Abedur Rahman with interest & have been really charmed to find the simplicity of its presentation & diagrams which depict the wide subject of embryology into the small space of this handy volume. Student can peep into the memory of the whole aspect of embryology through this book instantaneously and comfortably even at rest or in leisure like the cow which enjoys the taste of food by cutting its jaw while at rest. I wish the promising young author & his book a glorious success in the days to come.

Dr. Kazi Rafiqul Huq Head, dept. of Anatomy USTC, Chittogong.

AUTHOR’S SAYINGS “The history of man for nine months preceding his birth would, probably, be far more interesting, and contain events of greater moment than all three score and ten years that follow it.” --- Samuel Taylor Coleridge ABOUT THE FIFTEENTH EDITION It is now well proved that ‘Fetus is the most read embryology book in our country. The last 12 editions of the book have proven that it is unique in its field. In

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FETUS this edition, I have tried my best to make it more useful for the students making necessary changes elsewhere. New to this edition A large number of new figures.  Some new professional Q answers.

 Some new information All praises for the Almighty. Thanks to all the anatomy teachers and students – past, present, and future. January 2007

Some historical elements on embryology

Dr Md Abedur Rahman

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Look for the other books by the same author 1.

D”P evW †cÖmvi cÖwZKvi I cÖwZ‡iva

2. Medical

Genetics

3. Essentials of

Biostatistics 4. Developments of Thesis or Dissertation

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CONTENTS 1. 2. 3. 4.

Part-1: Introduction Introduction to embryology Reproduction and Development Some basic concepts in embryology Some historical elements on embryology

Part-2: General Embryology 5. Gametogenesis: Conversion of germ cells into male & female gamete 6. Female reproductive cycles and ovulation 7. Pre-embryonic period – I: Fertilization, cleavage and implantation 8. Pre-embryonic period-II: Formation of germ layers (Gastrulation) 9. Embryonic period: Derivatives of germ layers 10.Fetal period Some facts concerning the fetus 11.Fetal membranes and placenta 12.Congenital malformations 13.Developmental genetics Part-3: Systemic Embryology 14.Cardiovascular system 15.Digestive system 16.Respiratory system 17.Diaphragm and septum transversum18.Urogenital system 19.Head neck and ear 20.Nervous system 21.Skeletal system 22.muscular system 23.Integumentary system Glossary Find • MCQs and • SAQs of First professional examination, • Part Wise Development in second part of the book termed FETUS - 2

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Sample Chapter 4 Some historical elements on embryology If I have seen further, it is by standing on the shoulders of giants.- Sir Isaac Newton

[This chapter is not essential for examination. The chapter has been added here for interested students] The Greeks Although some of their ideas were later shown to be incorrect, the Greeks make important contributions to the science of embryology. The first recorded embryological studies are in the books of Hypocrates, the famous Greek physician of the fifth century B.C. He wrote: Some historical elements on embryology

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FETUS "Take twenty or more eggs and let them be incubated by two or more hens. Then each day from the second to that of hatching, remove an egg, break it, and examine it, You will find exactly as I say, for the nature of the bird can be likened to that of man." In the fourth century B.C. Aristotle wrote the first known treatise on embryology, in which he described development of the chick and other embryos, many embryologists regard Aristotle as "The Founder of Embryology." despite the fact that he promoted the idea that the embryo developed from a formless mass that resulted from the union of semen with menstrual blood. Galen (second century A.D.) wrote a book entitled On the Formation of the Fetus, in which he described the development and nutrition of fetuses and the structures we now call the allantois, the amnion and the placenta. The middle ages Growth of science was slow during the medieval period, and few high points of embryological investigation undertaken during the age are known to us. It is cited in the Holy Koran that human beings are produced from a mixture of secretions from the male and the female. Several references are made to the creation of a human being from a sperm drop, and it is also suggested that the resulting organism settles in the woman like a seed six days after its beginning. (The human blastocyst begins to implant about six day after fertilization). The Koran also states than the sperm drop develops "into a clot of congealed blood. (An implanted blastocyst or a spontaneously aborted conceptus would resemble' blood clot). The developing embryo was considered to be come human at 4010 42 days and to no longer resemble an animal embryo at this stage. (The human embryo begins to acquire human Characteristics at this stage). The Holy Koran also states that the embryo develops within "three veils of darkness". This probably refers to (1) the maternal anterior abdominal wall, (2) the uterine wall and [3] the amniochorionic membrane. Space does not permit discussion of several other interesting references to human prenatal development that appear in the Koran. The book, 'The developing human (Islamic edition by Abdul Majeed A Azzindani) by Keith L. Moore reflects the more details of the facts of embryology cited in the Holy 'Koran'. The true scientist Moore had made a research work for 3 years on the subject 'embryology and the holy Koran and helped Mr. Azzindani in publishing an Islamic edition of his text in 1982. In our country, prof. Golam Moazzem had made a research work on the same subject which was published in 'Pakistan Journal of science ‘in 1962 (Vol.-14, no-6). The renaissance During the fifteenth century, Leonardo da Vinci made accurate drawings of dissections of the pregnant uterus and associated fetal membranes and introduced the quantitative approach by making measurements of embryonic growth. The Microscope Some historical elements on embryology

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FETUS It 1651, Harvey studied chick embryos with simple lenses and made new observations, especially on the circulation of blood. He also studied development of the fallow deer, but, when unable to observe early stages, concluded tl4at the embryos were "secreted by the uterus". Early microscopes were simple, but they opened a new field of observation. In 1972 de Graaf observed little chambers in the rabbit's uterus and concluded that they could not have been secreted by the uterus, but must have come from the organs that he called ovaries undoubtedly, these little chambers were

Figure: Reproduction of Leonard da Vinci’s drawing made in the 15th century A.D., showing a fetus in a uterus that has been incised and open. what we now call blastocysts. He described vesicular ovarian follicles, which are still sometimes called graafian follicles in his honor. Malpighi, - in 1675, studying what he believed were unfertilized hen's eggs, observed early embryos. As a result, he thought the egg contained a Some historical elements on embryology

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FETUS miniature chick. In 1677 Hamm and Leeuwenhoek, using an improved microscope, first observed human spermatozoa, but they misunderstood the sperm's role in fertilization: They thought it contained a miniature human being.

Wolff, in 1759, refuted both versions of the preformation theory after observing parts of the Embryo develop from "globules" (probably blastocysts). He examined unincubated eggs and could not see the embryos described by Malpighi. He proposed the layer concept, whereby division of the zygote produces layers of cells from which the embryo develops. His ideas formed the basis of the theory of epigenesis, which states that development results from growth and differentiation of specialized cells.

The preformation controversy finally ended around 1775, when spallantani showed that both the ovum and the sperm were necessary for development of a new individual. From his experiments, including artificial insemination in dogs, he Fig- .: Copy of a seventeenth century concluded that the sperm was drawing by Hartsoeker of a sperm. The the fertilizing agent. miniature human being within it was thought to enlarge after the sperm entered In 1818, Saint Hilaire and his son made the first significant an ovum studies of congenital malformations. They did experiments in animals that were designed to produce developmental abnormalities initiating what is now known as the science of teratology. In 1827, about 150 years after the discovery of the sperm, von Baer described the oocyte in the ovarian follicle of a dog. He also observed Some historical elements on embryology

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FETUS dividing zygotes in the uterine tube and blastocysts in the uterus, and contributed much knowledge about the origin of tissues and organs from the layers described by Malpighi. His significant and far-reaching contributions resulted in his later being regarded as 'Me Father of Modem Embryology". The cell theory Great advances were made in embryology when the cell theory, stating that the body was composed of cells and cell products, was established in 1839 by Schleiden and Schwann this concept soon led to the realization that the embryo developed from a single cell, the zygote. The chromosomes In 1859, Charles Darwin published on the Origin of Species, in which he emphasized the hereditary nature of variability among members of a species as an important factor in evolution. The principles of heredity were developed in 1863 by an Austrian monk named Gregor Mendel but medical scientists and biologists did not understand the significance of these principles in the study of mammalian development for many years. Flemming observed chromosomes in 1878 and suggested their probable role in fertilization. In1883,von Beneden observed that mature germ cells have a reduced number of chromosomes. He also described some features of meiosis, the process whereby the chromosome number is reduced. In 1902 Sutton and Boveri declared independently that the behavior of the chromosomes during germ cell formation and fertilization agreed with Mendel's principles of inheritance. In the same year, Garrod reported aleaptonuria as the first example of mendelian inheritance in human beings. Many consider him the 'Father of Medical Genetics. The first significant observations on human chromosomes were made in 1912 when von Winiwarter reported that there were 47 chromosomes in the ells of the body. In 1923 Painter concluded that 48 was the correct number, this conclusion was widely accepted until 1956, when Tjop and.Levan reported finding only 46 chromosomes in embryonic cells. Their descriptions and photomicrographs were so superior to those of previous workers that few cytologists doubted the accuracy of their counts. Once the normal chromosomal pattern was firmly established, it soon became evident that some persons with congenital abnormalities had an abnormal number of chromosomes. A new era in medical genetics resulted from the demonstration by Lejcune et al. in 1959 that infants with mongolism (now called Down syndrome) have 47 chromosomes instead of the usual 46 in their body cells. It is now known that chromosomal aberrations are a significant cause of congenital malformations and embryonic death. About 8 percent of all conceptuses are known to be chromosomally abnormal. (Source: 'The developing human' by Keith L. Moore.] Test tube baby Some historical elements on embryology

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FETUS One of the most revolutionary developments in the history of human reproduction is the technique of in vitro fertilization, pioneered by Edwards and Steptoe, which in 1978 led to the birth of Louise Brown, the "First test tube baby."

Molecular Biology of Human Development Rapid advances in the field of molecular biology have led to the application of sophisticated techniques (e.g., recombinant DNA technology, chimeric models, transgenic mice, and stem cell manipulation). These techniques are now widely used in research laboratories to address such diverse problems as the genetic regulation of morphogenesis, the temporal and regional expression of specific genes, and how cells are committed to form the various parts of the embryo. For the first time we are beginning to understand how, when, and where selected genes are activated and expressed in the embryo during normal and abnormal development. Endogenous retinoic acid has been identified as an important regulatory substance in embryonic development. Apparently, it a transcriptional activator for specific genes involved in embryonic patterning. The critical role of homeobox-containing (HOX) genes and other molecular factors in regulating early embryonic development is rapidly evolving. The Noble Prize for Physiology or Medicine was awarded in 1995 to Edward Lewis, Christiane Nusslein-Volhard, Eric Wieschaus for their discovery of genes that control embryonic development. These discoveries are helping us to understand the causes of spontaneous abortion and congenital anomalies. In 1997, Ian Wilmut and colleagues were the first to produce a mammal (a sheep dubbed Dolly) by cloning using the technique of somatic cell nuclear transfer. Since then, other animals (mice, cows, and pigs) have been cloned successfully from cultured differentiated adult cells. In human cloning has generated considerable debate because of social, ethical, and legal implications. Moreover, there is concern that cloning may result in infants born with birth defects and serious diseases Human embryonic stem cells are pluripotential and capable of developing into diverse cell types. The isolation and culture of human embryonic Stem cells hold great promise for the development of molecular therapies as a result of the sequencing of the human genome.

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