Embryology 2 Flashcards

1
Q

What happens during week 3?

A
  • Formation of germ layers – GASTRULATION
  • Formation of neural tube – NEURULATION
  • Development of somites
  • Early development of cardiovascular system
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2
Q

How is the primitive streak formed?

A

Formed in midline of epiblast by dipping in of cells (invagination)

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3
Q

What is formed after the primitve streak is formed?

A

Axis of embryo is formed

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4
Q

Where do epiblast layers migrate to?

A

Space between epiblast and the hypoblast layers

Cells displace the hypoblast

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5
Q

From the original epiblast, what three layers are formed?

A
  1. Ectoderm
  2. Mesoderm
  3. Endoderm

Trilaminar disk

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6
Q

What is gastrulation?

A

Formation of three germ layers

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7
Q

What layer does the primitive streak form from?

A

Ectoderm

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8
Q

What is the name given to the solid tube of cells formed from the ectoderm called?

A

The notochord

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9
Q

What is does the notochord do?

A

Induces ectodermal cells on midline to form neural tube

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10
Q

What is the precursor for the neural tube?

A

The neural plate

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11
Q

What is neurulation?

A
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12
Q

What is the effect of the neural tube on the mesoderm?

A

Causes the mesoderm to thicken

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13
Q

What happens after the mesoderm thickens?

A

It splits into three parts

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14
Q

What is the name of the three parts of the mesoderm?

A
  • Paraxial mesoderm
  • Intermediate plate mesoderm
  • Lateral plate mesoderm
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15
Q

What happens to the lateral plate of the mesoderm?

A

Lateral plate mesoderm splits to form a somatic and splanchnic mesoderm

Space formed in between: intraembryonic coelom

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16
Q

What does the paraxial mesoderm form?

17
Q

What does the intermediate plate mesoderm form?

A

Urogenital system (kidneys + repro)

18
Q

What does the lateral plate form

A

Body cavity and coverings. Peritoneum, pleura, and body cavities

19
Q

Segmentation of paraxial mesoderm forms?

20
Q

What does each paraxial mesoderm divide into?

A
  1. Dermatome
  2. Myotome
  3. Sclerotome
21
Q

What is the function of each of these divisions of the somites?

22
Q

What happens during 4th – 8th weeks – Embryonic period / Organogenetic period?

A
  • Folding into a tube (lateral folds) which started in 3rd week completes
  • Neural tube – forebrain, midbrain, hindbrain and spinal cord development
  • Heart starts to beat on Day 24
  • Gut formation from endoderm
  • Urogenital system formation from intermediate mesoderm
  • Body cavities from lateral plate mesoderm
  • 43 pairs of somites form in the paraxial mesoderm and differentiate further
  • Limb buds form
  • Neck development – pharyngeal arches
23
Q

Which lateral plate is on the inside when the lateral folding of the embryo has been completed?

A

The splanchnic

24
Q

What do the somatic mesoderm and the splanchnic mesoderm form?

A

Pleura:

Somatic = Parietal

Splanchnic = Visceral

25
Look
26
Summary of the three germ layers
27
Label the above structures
28
What are teratogens?
Environmental factors that cause abnormal development.
29
What is congenital rubella caused by?
Contraction of german measles when pregnant
30
What are the environmetnal teratogens?
Drugs – prescription / other Alcohol/ tobacco Infectious agents: ToRCH (Toxoplasma, Rubella, Cytomegalovirus, Herpes ) can transfer through placenta and affect developing embryo Others – eg: radiation
31
What are the genetic factors?
Too many/too few chromosomes: * Turner’s syndrome – 45 chromosomes single X * Down’s syndrome – 47 chromosomes trisomy 21 Structural changes – deletions of genes, segments of chromosomes Causes: * Increased maternal age * Damage from environmental factors such as radiation (eg: X-rays)
32
Which weeks have a high risk of death, low risk of teratogens?
Weeks 1 and 2
33
Which weeks whow a eriod of the greatest sensitivity to teratogens?
Weeks 3-8
34
Which weeks show a decreasing sensitivity to teratogens?
Weeks 9 - 38
35
What does the risk of a teratogen depend on?
* Exposure during critical periods of development * Dosage of drug/chemical/factor * Genetic constitution of embryo i.e. some more susceptible than others at equivalent doses etc
36
How are prenatal diagnosis of malformations made?
Blood - AFP Ultrasound scan – 12 week anomaly scan Invasive tests - chorionic villus sampling and amniocentesis
37
How are postnatal diagnosis of malformations made?
* Hip stability * Testes (descent) * Fingers and toes * Hearing