1st Lecture Embryology

7/27/2019 1st Lecture Embryology

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y

a developmental process that

represents an amazing integrationof increasingly complex

phenomena. The study of these

embryology,phenomena is called

Introduction to Embryology

Dr.eman khammas al-sadi


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the field includes investigations of the

1. molecular factors.

2. cellular factors.

3. structural factors. contributing to the

formation of an organism.

These studies are important because

they provide knowledge essential for

creating health care strategies forbetterreproductive outcomes


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Studying embryology hasresulted in

A. new techniques for prenataldiagnoses and treatments,

B. therapeutic procedures to overcomeproblems with infertility,

C. mechanisms to prevent birth defects,the leading cause of infant mortality.

These improvements are significant,not only to improved birth outcomesbut also for their long-term effectspostnatally.


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cognitive capacity and our behavioralcharacteristics are affected by ourprenatal experiences, and factors such asmaternal

1. smoking,2. nutrition,3. stress,

4. diabetes,5. etc., play a role in our postnatal health.in

combination with

1. molecular factors,2. cellular factors,determine our potential to develop certain

adult diseases, such as cancer and

cardiovascular disease.


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Fertilized eggimmediately prior

to fusion of the

male and female

pronuclei.

B. Seven-month-

old fetus
http://void%280%29/


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EmbryoLec2: chromosomal abnormalities

Lec3: S4: primordial follicle

S5,7,16,21,23

Lec5: S3,13,17,19,20

Lec6: S4,6 {slides: 14,15,17 short assay}

Lec7: S2,11,12

Lec8: S8,9,13,16,28 {slides: 17,18 }

Lec9: S6,7,12,13

Lec10: 22

Lec11: S{4,5, }S10,13,17,18,26

Lec12: S22,30


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During the past century,

embryology has progressed from an

observational science to one involving

sophisticated technological and molecularadvances.

Together, observations and modern

techniques provide a clearer understandingof

1. the origins of normal and abnormal

development

2. and, in turn, suggest ways to prevent andtreat birth defects.

In this regard, knowledge of gene function

has created entire new approaches to thesub ect.


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A BRIEF HISTORY OF

EMBRYOLOGY

embryogenesis or organogenesis

The process of progressing from a singlecell through the period of establishingorgan primordia (the first 8 weeks of

human development)

fetal period,

the period from(8 weeks until birth )

teratology

The study of the embryological origins

and causes for these birth defects


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Child with

phocomelia

(absence ofthe long

bones of the

limb)

caused by thedrug

thalidomide.
http://void%280%29/


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1. one-gene-one-proteinhypothesis.

through a variety of mechanisms, a singlegene may give rise to many proteins

Gene expression can be regulated atseveral levels:

(1) different genes may be transcribed,(2) nuclear (DNA) transcribed from a gene

may be selectively processed toregulate which RNAs reach the

cytoplasm to become messenger RNAs(mRNAs),

(3) mRNAs may be selectively translated,

(4) proteins made from the mRNAs may be


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There are approximately 35,000 genes inthe human genome, but these genescode for approximately 100,000 proteins.

Genes are contained in a complex ofDNA and proteins called chromatin, andits basic unit of structure is thenucleosome.

Genes reside within strands of DNA andcontain regions that can be translated intoproteins, called exons, and

untranslatable regions, called introns. . . A typical gene also contains a

promoter regionthat binds RNApolymerase for the initiation of

transcription
http://void%280%29/


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nucleosome consistsof an octamer ofhistone proteins and

approximately 140base pairs of DNA.

Nucleosomes keep theDNA tightly coiled,such that it cannot betranscribed.

In this inactive state,chromatin referred toas heterochromatin.

For transcription tooccur, this DNA mustbe uncoiled from thebeads.

In this uncoiled state,chromatin is referred toas euchromatin.
http://void%280%29/


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A typical gene also contains a promoter region that binds RNA polymerase for the

initiation of transcription; a transcription initiation site, to designate the first

amino acid in the protein;

a translation termination codon;

a 3untranslated region that includes a sequencethat assists with stabilization of the mRNA.

The RNA polymerase binds to the promoter region

that usually contains the sequence TATA, the TATA

box. Binding requires additional proteins called

transcription factors.

Different proteins can be produced from a

single gene by different processes


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Induction

is the process whereby one group ofcells or tissues (the inducer) causesanother group (the responder) tochange their fate.

The capacity to respond is calledcompetence and must be conferredby a competence factor.

Many inductive phenomena involveepithelial-mesenchymalinteractions.


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Signal transduction pathways include a signaling molecule (the ligand) and

a receptor.

The receptor usually spans the cellmembrane and is activated by binding with itsspecific ligand.

Activation usually involves the capacity tophosphorylate other proteins, most often as akinase.

This activation establishes a cascade ofenzyme activity among proteins thatultimately activates a transcription factor forinitiation of gene expression.


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Cell-to-cell signaling may be1. paracrine, involving diffusable factors,

2. orjuxtacrine, involving a variety ofnondiffusable factors.

Proteins responsible for paracrine signaling arecalled paracrine factors orgrowth and

differentiation factors (GDFs).

There are four major families of GDFs:

1. fibroblast growth factors (FGFs),

2. WNTs,

3. hedgehogs,

4. and transforminggrowth factor-s (TGF-s).


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Thank

you

Documents

1st Lecture Embryology