K12 -SGHS 2011 Embryology Questions

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Introduction

The following questions were part of a SGHS Year 9 team research project on the history of medicine in the field of Embryology. The answers I provided have had to be a little selective in order to meet a quick deadline. I will update these responses online in a less stressful manner when such a deadline does not loom. You should perhaps also look here again for updates to my answers.

These should not be seen as complete answers, but a work in progress. I am always happy for students to contact me with questions about development, answering them online allows others to benefit from the responses.

--Mark Hill 13:11, 23 August 2011 (EST)

How significant is embryology in our modern society?

  • Reproduction has always been an important topic, not only in humans, but also for food production in animals and plants. Historic studies focussed on animal and plant reproduction for food and many of our modern animals and plants have come from an understanding of breeding to produce the best livestock or crops.
  • In modern society, people are continuing to make decisions that affect development, either to reproduce (aid pregnancy) or not (pregnancy prevention) and much research is still going into understanding the best mechanisms for both these processes.
  • Significantly in recent years in vitro fertilisation (or assisted reproductive technologies) and new stem cell research has only just begun to show the potential that both can have to society, health and disease.
  • All of the above have led to significant ways in how reproduction is understood scientifically, legally and ethically today.
  • The recognition scientifically can also be seen by the many nobel prizes that have been award for research that directly stems from developmental research.
    • Including last year Nobel Prize in Physiology or Medicine 2010 - Awarded to Robert G. Edwards "for the development of in vitro fertilization" who battled societal and establishment resistance to his development of the in vitro fertilization procedure, which has so far led to the birth of around 4 million people. (More? In Vitro Fertilization)
Links: Medicine Nobel Awards in development

Can you give us examples of situations where knowledge of embryology has been useful and vital for a normal birth?

A newborn infant (perinatal period)

Understanding when specific events occur during a pregnancy have led to changes in many things associated with pregnancy.

  1. Menstrual cycle endocrinology changes (for successful pregnancies or pregnancy prevention).
  2. Maternal age and genetic abnormalities (increasing maternal age has increasing genetic abnormalities associated with the ageing oocyte (egg), including trisomies)
  3. Knowledge that twinning events (monozygotic) occur in the first few weeks of development and the later the twinning event the more serious the developmental effect (conjoined).
  4. First trimester for development of major body systems (lifestyle changes, maternal nutrition, first trimester diagnostic screening)
  5. Maternal nutrition (folate required for neural tube (early nervous system) development, iodine required for fetal neural development).
  6. Understanding that some systems continue to develop in the second and third trimesters (neural, genital, respiratory). Respiratory only maturing just before birth, leading to respiratory distress, is the cause of many problems in premature infants.

How closely is embryology linked with genetics?

There is an extremely close linkage.

  • Today much of embryology studies are molecular studies, looking at the mechanisms involved in signalling between cells and tissues to regulate not only tissue development (muscle, bone, nervous, skin, organs etc) but also patterning (body axes, musculoskeletal, organ and tissue positions in the body). Molecular Development - Genetics
  • The other side of this understanding, is when things go wrong. Abnormal Development - Genetic
  • The understanding of genetic inheritance mechanisms have helped understand how certain traits (good and bad) are passed on to our offspring. Genetic Inheritance
  • Many of the mechanisms that are tightly regulated in development (such as mitosis and cell differentiation) can also have an impact on postnatal health (such as in cancers).
  • Resolving the human genome (2000) has only provided a "roadmap" of all the gene players we still need to understand how these interact and are regulated during development.


Links:

Can you name a few different ways and examples of how deformities/abnormalities can be formed?

X-Linked recessive (carrier mother)

Three major types of congenital abnormalities:

  1. genetic - due to inheritance from our parents, or a recombination of their genetics, or mutations that occur in genes or chromosomes during development. Genetic Trisomy 21 Philadelphia chromosome
Genetic Links: Introduction | Genetic risk maternal age | Trisomy 21 | Trisomy 18 | Trisomy X | Fragile X | Williams | Philadelphia chromosome | Hydatidiform Mole | Prenatal Diagnosis | Neonatal Diagnosis | International Classification of Diseases | Molecular Development - Genetics
  1. environmental - due to exposure to various conditions during embryonic and fetal development. Any of these that affect normal development are called "teratogens". Environmental
Environmental Links: Introduction | Low Folic Acid | Iodine Deficiency | Nutrition | Drugs | Australian Drug Categories | USA Drug Categories | Thalidomide | Herbal Drugs | Illegal Drugs | Smoking | Fetal Alcohol Syndrome | TORCH Infections | Viral Infection | Bacterial Infection | Zoonotic Infection | Toxoplasmosis | Malaria | Iodine Deficiency | Maternal Diabetes | Maternal Hyperthermia | Maternal Inflammation | Biological Toxins | Chemicals | Heavy Metals | Radiation | Prenatal Diagnosis | Neonatal Diagnosis | International Classification of Diseases | Fetal Origins Hypothesis
  1. unknown - may be caused by either or both of the above, but we do not understand the mechanism. This forms a large group of abnormalities that we do not yet know how they occur.

There is also the interaction between these 3 mechanisms that can affect normal development. Interestingly, development can also be extremely robust, where quite normal outcomes can occur under quite trying conditions.


Links: Human Abnormal Development

Does the embryology of animals closely relate to the research of embryology of humans?

Much of what we know today about human development stems from an understanding of animal development and animal models. I will give a few examples below.

  1. The mechanisms of development have been strongly conserved between species so in many cases can be easily applied to an understanding of human development.
  2. Using animal models we can understand the timing of specific developmental events and the importance of this to the whole animal development.
  3. Importantly there occur in many animal species developmental diseases similar to those that occur in humans.

Frog

Frog lifecycle
  • Historically studies of the frog 1930's identified early events of development following fertilisation. Frog Development Frog Embryology History
  • Understanding issues about early patterning of the new embryo.
  • Formation of the main germ layers by "gastrulation".
  • Hormonal control of reproduction and reproductive cycles.

Chicken

  • Studies of the chicken allowed establishment of a developmental time (1900's, 1950's) Chicken Development
  • Chicken/quail hybrid studies identified how a small population of cells (neural crest) contribute to the development of many different tissues. Nicole Le Douarin

Fly

  • The molecular biology revolution (1980's) led to the development of the fly model for understanding developmental mechanisms at a molecular level. Fly Development
  • Much of our understanding of "patterning" in development comes from studies of fly mutants where pattern is disrupted.
  • This also showed the strong conservation of developmental mechanisms, as the same patterning genes in the fly pattern animal and human development.

Mouse

  • The molecular biology revolution also led to the mouse model of development. Mouse Development
  • Its genome was one of the first to be sequenced.
  • Human diseases can mimicked in mice by "knocking out" the disease genes.
  • These animals can not only mimic the effects seen in humans but provide a tool for understanding potential therapeutics for these diseases.

Zebrafish

Zebrafish lavae
  1. The embryonic zebrafish is transparent, you can see inside the embryo and watch organs and tissues develop, especially if they have been labeled.
  2. The entire genome is being sequentially "knocked out" gene by gene, to see the effects of every gene upon development, and making these mutants available to other researchers.


Links: Animal Development

Are there any limitations of animal research being applicable to human research?

  • There are some limitations as not all species have the same reproductive cycles (menstrual, oestrus) anatomy or postnatal development (puberty, menopause).
  • Some animals models are not affected by teratogens (things that affect normal development) in the same way as humans. This can be seen in thalidomide effects and some other agents.
  • Some postnatal developmental functions, such as neural development and puberty, do not easily translate into animal models.


Links: Animal Development

Could you name a few significant individuals and discoveries that helped shape the study of embryology as we know it today?

I need to develop this answer, but begin by looking at the Embryology History page and Nobel Prizes in Medicine.

  • 1880 - Wilhelm His (1831-1904) German embryologist historic study Anatomie menschlicher Embryonen (1880).
  • 1910-30 - Franklin P. Mall (1862-1917) Carnegie Institute of Washington established a collection of embryos for staging human development.
  • 1935 - Hans Spemann Nobel Prize in Medicine "for his discovery of the organizer effect in embryonic development".
  • 1941 - Norman Gregg (1892-1966) was a Sydney ophthalmologist who in 1941 identified the link between maternal rubella infection and developmental abnormalities (atypical congenital cataracts, congenital heart defects, infants small-for-gestational age) initially in his own practice. This had coincided with a rubella epidemic that occurred between 1940 to 1941.
  • 1977 - William McBride, an Australian clinician and also reported independently in Germany by Widukind Lenz identified thalidomide as a teratogenic agent causing a "thalidomide embryopathy".
  • 1978 - Robert G. Edwards 2010 Nobel Prize in Medicine "for the development of in vitro fertilization".
  • 1995 - Edward B. Lewis, Christiane Nüsslein-Volhard, Eric F. Wieschaus Nobel Prize in Medicine "for their discoveries concerning the genetic control of early embryonic development".
  • 2002 - Sydney Brenner, H. Robert Horvitz, John E. Sulston Nobel Prize in Medicine "for their discoveries concerning "genetic regulation of organ development and programmed cell death".

IVF and the ethical, moral and legal issues of it?

Louise Brown, the first IVF baby as an adult.

I am happy to discuss and focus upon the biology of IVF. The ethical, moral and legal issues are for another forum and group of experts. (Still working on this answer)

  • The development of human stem cells has been also aided by IVF as these were the first eggs available to establish these cells. Stem Cells


Links: In Vitro Fertilization

What is the future of embryology in your opinion? Is it going to make the world only produce ‘perfect babies’

  • There will always be problems associated with development, it is the most complex biological mechanism we know generating billions of cells with many different specialised function from a single cell.
  • Our understanding of this process improves every day with research but the aim was and is never to produce perfect babies, but to understand the biology of development and when things go wrong.
  • Society has in the past shown a willingness to adopt the many benefits research can bring to health and we know that there can also be mistakes made through a lack of understanding (e.g. thalidomide, alcohol, smoking, maternal diet, lifestyle and environment). Understanding some of these developmental affects has led to changes in society. Such as:
    • decreasing smoking and drinking during pregnancy.
    • improving maternal diet with folate and iodine supplementation.
    • establishing a system of drug classifications based upon the drug affect upon development.
    • improved management of mothers with health or genetic problems during pregnancy.
  • We also are beginning to understand that what occurs during development can also have life-long health consequences.
    • This is the "fetal origins of disease" hypothesis originally called the Barker Hypothesis.


Maybe not "perfect babies", but certainly healthier babies through understanding development! And from that, maybe a few more researchers to help out with our understanding.....


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Cite this page: Hill, M.A. (2014) Embryology K12 -SGHS 2011 Embryology Questions. Retrieved August 2, 2014, from //php.med.unsw.edu.au/embryology/index.php?title=K12_-SGHS_2011_Embryology_Questions

What Links Here?
Dr Mark Hill 2014, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G