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MOLECULAR BASIS OF DISEASE > 4. MECHANISMS OF DISEASE III: DURING EMBRYOGENESIS > Flashcards

4. MECHANISMS OF DISEASE III: DURING EMBRYOGENESIS Flashcards

1
Q

What are the two main periods of embryogenesis?

A
  1. EMBRYONIC PERIOD - First 8 weeks, when most of the organogenesis occurs
  2. FOETAL PERIOD - The remaining period iin utero which involves growth & modelling
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2
Q

What are the 7 processes of human development?

A
  1. FERTILISATION
  2. CLEAVAGE
  3. BLASTULATION
  4. GASTRULATION
    5, NEURULATION
  5. SOMITOGENESIS
  6. ORGANOGENESIS
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3
Q

What is cleavage?

A
  • Cleavage refers to a series of mitotoc divisions without growth
  • Zygote - 2 cell -> 4 cell -> Morula
  • The zygote undergoes many cleavages as it travels through the uterine tube to the uterus before it implants at around 10 days
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4
Q

What is blastulation?

A
  • Blastulation refers to the fromation of a blastocyst
  • The Morula undergoes a process of compaction where the cells rearrange, getting closer to from a blastocyst
  • Blastocyst consists of 32 - 46 cells at around day 4/5
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5
Q

What are the two cell layers of the blastocyst?

A
  1. Outer trophoblast

2. Inner embryoblast - gives rise to the inner cell mass

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6
Q

What is the blastocoele?

A
  • The blastocoele is a fluid filled cavity which is located between the trophoblast & the embryoblast
  • The trophoblast cells secrete fluid into cavity
  • The blastocoele displaces the inner cell mass to one side
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7
Q

What two cell layers does the inner cell mass give rise to?

A
  • Inner cell mass differentiates into:
    1. EPIBLAST
    2. HYPOBLAST
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8
Q

What is the bilaminar disc?

A
  • The epiblast & hypoblast form the bilaminar disc
  • The epiblast is located above the hypoblast
  • Cells of the epiblast rearrange to from the amniotic cavity which is located in between the epiblast & hypoblast
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9
Q

What is gastrulation?

A
  • Gastrualtion refers to the formation of the three germ layers
  • The blastocyst/blastula is rearranged into a gastrula
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10
Q

What are the three germ layers?

A
  1. ECTODERM
  2. ENDODERM
  3. MESODERM
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11
Q

What is the primitive streak & how does it form?

A
  • The primitive streak originates at teh caudal end of the epiblast & grows cranially
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12
Q

What is the primitive groove?

A
  • The primitive groove is a shallow depression within the primitive streak
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13
Q

What happens during invagination of the epiblast?

A
  • Cells of the epiblast ingress/invaginate through the primitive groove into the underlying hypblast
  • The ingressing epiblast cells dipslace the hypoblast to give rise to the endoderm & primitive mesoderm
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14
Q

What two germ layers arise from the hypoblast?

A
  1. ENDODERM

2. MESODERM

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15
Q

What germ layer does the epiblast give rise to?

A
  • ECTODERM
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16
Q

What is the trilaminar disc?

A
  • Once the three germ layers have formed, the bilaminar disc becomes the trilaminar disc
17
Q

What is neurualtion?

A
  • Neurulation is the process by which the neural plate folds back on itself to form the neural tube beneath the ectoderm
18
Q

How does the notochord form?

A
  • Once the primitive streak has extended towards the cranial end, it begins regressing
  • As the primitive streak regresses it lays down a chord like structure known as the NOTOCHORD underneath the ectoderm within the mesoderm
19
Q

How does the neural plate from?

A
  • The notochord releases extracellualr signals which causes the overlying ectoderm to form the NEURAL PLATE
  • The neural plate is a thickening of the ectoderm
20
Q

How does the neural plate become the neural tube?

A
  • The neural folds of the neural palte fuse to form a ring which is the neural tube
  • The neural tube begins by closing in the middle first, between the hindgut & spinal cord
  • It then continues anteriorly & posteriorly until teh whole tube is fused
21
Q

What is somitogenesis & which germ layer is involved in somitogenesis

A
  • Somitogenesis is the process by which somites from
  • The cells of the mesoderm differentiate into somites
  • Somites are precursors of muscle & bones
22
Q

What are neural crest cells?

A
  • Neural crest cells are cells of the ectoderm which invaginate into the mesoderm
23
Q

What is the puprose of body/embryonic folding?

A
  • Embryonic folding allows organs to be enclosed

- Mesoderm & endoderm give ris to oragns which need to be enclosed

24
Q

Waht two planes does embryonic folding occur on?

A
  1. HORIZONTAL PLANE

2. MEDIAN PLANE

25
Q

What folds are produced through embryonic folding on the horizontal & median plane?

A
  • Horizontal plane = two lateral folds

- Median palne = cranial & caudal body folds

26
Q

What main structure does the endoderm differentiate into?

A
  • Endoderm differentiates into Gi tract
  • As embryonic folding occur, teh endoderm moves towards the midline & fuses to form the primitive gut tube
  • The primitve gut tube forms the foregut, midgut & hindgut
27
Q

What are the main events of embryonic folding?

A
  • Heart & septum move from margin to centre
  • Yolk sac, allantois & stalk make umbilical cord
  • Prochordal & cloaclal paltes form gut tube
28
Q

What are the 5 main events organogenesis?

A
  • Organogenesis refers to teh development of organs
    1. Development of somitic derivatives - bone, muscle
    2. Development of sensory structures - eyes, ears
    3. Limb formation - forelimbs then hindimbs
    4. Formation of face structures - jaw, nose, tongue, palate
    5. Formation of genital structure
29
Q

What type of diseases can occur due to defects in embryogenesis?

A
  • Congenital malformations or diseases

- If the defects occur earlier on, the resulting diseases will be more severe

30
Q

What are 4 causes of disease?

A
  1. SINGLE GENE MUTATIONS - one gene mutation produces a characteristic effect (Mendelian disease)
  2. CHROMOSOMAL ANOMALIES - Abnormalities with chromosome number due to rearrangement e.g trisomy
  3. POLYGENIC DISORDER - several genes causing disease
  4. ENVIRONMENTAL - diet, infection, toxic compounds
31
Q

What is multi-factorial aetiology?

A
  • Congenital diseases have a multifactorial aetiology, meanining it’s caused by a combination of intrinsic & extrinsic causes
32
Q

What are the desirable characteristics of a model organism to study embryogenesis?

A
  • It would be unethical to study embryogenesis with a human embryo so other models need to be used
    1. Represenattive/relevant
    2. Accessibility/availability
    3. Experimental manipulation
    4. Gentics of organism are known
    5. Cost/space
33
Q

What model organisms can be used to study disease during embryogenesis?

A
  1. Drosophila
  2. Flat worms
  3. Vertebraes
  4. Zebrafish
34
Q

What properties of zebrafish make it an ideal organism for study?

A

+ Embryos of zebrafish are transparent amking it easy to study changes
+ Cheap & easy to maintain
+ 70% of zebrafish genes are homologous with humans & 84% of disease genes

MOLECULAR BASIS OF DISEASE (4 decks)

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