GENERAL EMBRYOLOGY anatomy basic science.pdf

General embryology

1. GENERAL EMBRYOLOGY

2. EMBRYOLOGICAL TERMS
•Sperm:Malegermcellproducedbytestes.
•Oocyte:Femalegermcellproducedbyovary.
•Fertilization:Unionoffemaleandmalegametes.
•Zygote:itisacellformedafterunionofmaleand
femalegametes.
•Cleavage:Celldivisionbymitosis.
•Morula:Morulaisacompactmassofcellsformedby
16cells.
•Blastocyst:Fluidentersthemorulaformingafluid
lakeinsidethemorula.Morulawhichistransferred
intothefluid-filledcavityiscalledtheblastocyst.

3. •Implantation: attachment of blastocystto the
endometriumand its embedding in the
endometrium.
•Gastrula: Formation of three germ layers, i.e.
endoderm, ectoderm and mesoderm.
•Neurula: Formation of neural tube from the neural
plate.
•Abortion: Expulsion of embryo or the fetus before
maturation.
•Prenatal period—
Embryonic period—0-56
th
day.
Fetal period—57
th
day to birth.

4. SIGNIFICANCE OF EMBRYOLOGY
•Withthestudyofdevelopment,anatomical
realationscanbeexplainedandbetterunderstood.
•Useofalcohol,smoking,drugs,viralinfectionsand
teratogensincludingtheexternalenvironmentare
blamedfortheabnormaldevelopment.The
incidenceoftheabnormaldevelopmentcanbe
reducedtotheminimumbyrenderingadviceand
adoptingpreventivemeasures.

5. GAMETOGENESIS
Includes;
•Spermatogenesis: The formation of spermatozoanis
known as spermatogenesis.
•Oogenesis: The process of formation of ovum is
known as oogenesis.

6. •Spermatogenesisisthe
processbywhichmale
primary sperm
cellsundergomeiosis,
andproduceanumber
of cells
termedspermatogonia,
fromwhichthe
primaryspermatocytes
arederived.Each
primaryspermatocyte
dividesintotwo
secondary
spermatocytes,and
each secondary
spermatocyte into
twospermatidsor
youngspermatozoa.

7. STRUCTURE OF A MATURE SPERM
•Length of a mature sperm is
50 microns.
•Parts of sperm:
1) Head: Head contains 23 pairs of
chromosome. Covered by acrosome.
2) Neck: contains one centriole.
3) Body ( middle piece): made of axial
filaments, mitochondrial sheath,
cytoplasm and cell membrane.
4) Tail: is the mobile part of sperm.

8. OOGENESIS
•Theprocess
of
formation
ofmature
ovum or
oocyteis
knownas
Oogenesis.

9. STRUCTURE OF A MATURE OVUM
•Coverings are:
1)Coronaradiata
2)Vitellinemem.
3)Zonapellucida-It
prevents the
implantationat
the abnormal
sites.

10. Human ？
Plant
Animal
FERTILIZATION

11. FERTILIZATION
•Theprocessin
which the
spermatozoon
penetratesinto
theovumtoform
fertilizedovum..
•Occursinthe
AMPULLA of
theuterinetube.

12. ovum
fertilized ovum
sperm

13. ①Fusion of the
membrane of
sperm and ovum
②The nucleus
of sperm
penetrate into
ovum
③Formation of
pronuclei
④Fusion of
pronuclei
Process of fertilization
Alteration of ovum 24 h

14. Significance of fertilization:
•Restoration of diploid no. of chromosome.
•Determination of sex.
•Restoration of cell size.

15. Movement and implantation of fertilized egg

16. Implantation at 7th day
Endometrium
Polar trophoblast
Inner cell mass
Cytotrophoblast

17. Bilaminar germ disc at 9th day
Hypoblast
Epiblast
Amniotic cavity
Syncytio-
trophoblast
Primary yolk sac

18. TRILAMINAR GERM DISC FORMATION
•Endoderm: First formed layer.
•Ectoderm:
•Mesoderm:
All tissues of the body are derived from one or
more of these layers.

19. FATE OF GERM LAYERS
ECTODERM ENDODERM MESODERM
HAIRS, NAILS, SKIN, LENSEPITHELIUM OF
OESOPHAGUS, STOMACH,
INTESTINE
HEART
ENAMEL OF TEETH EPITHELIUM OF
RESPIRATORY SYSTEM
KIDNEY
NERVOUS SYSTEM EPITHELIUM OF GREATER
PART OF VAGINA,
VESTIBULE AND
OVARY, TESTES
MUCOUSMEMBRANE OF
LIPS, CHEEKS, GUMS.
INNER SURFACE OF LABIA
MINORA
ALL MUSCLES
WHOLE OF THE LABIA
MAJORA, OUTER SURFACE
OF LABIA MINORA.
THYROID, PARATHYROID
GLAND, THYMUS GLAND
SKELETAL SYSTEM
SWEATGLAND,
SEBACEOUS GLAND,
MAMMARY GLAND
LIVER, PANCREAS,
HYPOPHSIS CEREBRI. PROSTATE GLAND.

20. PLACENTA

21. •Organ of metabolic exchange between the fetus and the
mother.
•Placental membrane is formed by:
1) Endothelium of the fetal blood vessels.
2) Surrounding mesoderm
3) Cytotrophoblast, and its membrane
4) Syncytiotrophoblast
•Functions of placenta:
1) Transport of oxygen, water, electrolyte, nutrition,
carbohydrate, lipids and vitamins from mother to the
fetus.
2) Excretion of CO2 and urea.
3) Maternal antibodies( IgG) gives immunity to the fetus.
4) Helps in exchange of gases and excretion products of
metabolism between fetus and mother.

22. NEURULATION
•The process of formation of the neural plate. Neural
fold and their fusion to form the neural tube is called
“Neurulation”.

23. UMBILICAL CORD
•Ropelikestructure
connectingumbilicusof
thefetustothecentre
ofthefetalsurfaceof
theplacenta.
•50cm long,2cm
breadth.
•Contents:
--2umbilicalarteries.
--1umbilicalvein.
--Wharton’sjelly.

24. TWINS AND MULTIPLE BIRTH
1.Twins
Monozygotic twins
Dizygotictwins/
Fraternal twins.

25. PLACENTA PREVIA
•Theconditioninwhich
the placentais
implantedinthelower
segmentoftheuterus.
•Extendingtothemargin
ofinternalos.
•Itcausesdifficulty
duringchildbirthand
maycausesevere
bleeding.

26. TEST TUBE BABY
•Areproducedbythein
vitrofertilization
•(outsidethebody).
•Fertilizationisdonein
suitablemedium,and
whentheembryoisat
the8-celledstage,itis
keptinsidetheuterus.

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