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1st year systems ADAM > Embryology 2 > Flashcards

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?

A

Somites

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?

A

Somites

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?

A
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
Q

Look

A
26
Q

Summary of the three germ layers

A
27
Q

Label the above structures

A
28
Q

What are teratogens?

A

Environmental factors that cause abnormal development.

29
Q

What is congenital rubella caused by?

A

Contraction of german measles when pregnant

30
Q

What are the environmetnal teratogens?

A

Drugs – prescription / other

Alcohol/ tobacco

Infectious agents: ToRCH (Toxoplasma, Rubella, Cytomegalovirus, Herpes ) can transfer through placenta and affect developing embryo

Others – eg: radiation

31
Q

What are the genetic factors?

A

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
Q

Which weeks have a high risk of death, low risk of teratogens?

A

Weeks 1 and 2

33
Q

Which weeks whow a eriod of the greatest sensitivity to teratogens?

A

Weeks 3-8

34
Q

Which weeks show a decreasing sensitivity to teratogens?

A

Weeks 9 - 38

35
Q

What does the risk of a teratogen depend on?

A
  • 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
Q

How are prenatal diagnosis of malformations made?

A

Blood - AFP

Ultrasound scan – 12 week anomaly scan

Invasive tests - chorionic villus sampling and amniocentesis

37
Q

How are postnatal diagnosis of malformations made?

A
  • Hip stability
  • Testes (descent)
  • Fingers and toes
  • Hearing

1st year systems ADAM (52 decks)

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