1.3: Week 3- Trilaminar Germ Disc ✅ Flashcards

1
Q

After implantation, what is the bilaminar embryo made up of?

A

2 layers sandwiched between 2 cavities

Epiblast and Hypoblast between amniotic cavity and blastocyst cavity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the most characteristic event during week 3?

A

Gastrulation-> trilaminar embryo

Establishes 3 germ layers in the embryo

-ectoderm
-mesoderm
-endoderm

Begins with formation of primitive streak of the surface of the epiblast

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Germ layer

A

Group of cells in an embryo

The layers interact with each other as embryo develops
-eventually give rise to all organism’s tissues and organs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Ectoderm

A

Outer body tissues

-skin, nails, teeth

-nerves, eyes, lining of mouth

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Mesoderm

A

Middle tissues

-blood and lymph, bone and notochord, muscle

-excretory and reproductive systems

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Endoderm

A

Inner lining

-digestive system

-lining of respiratory, excretory and reproductive systems

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What stage is highly sensitive for teratogenic insult?

A

Initiation of gastrulation

(Teratogens are things that cause abnormalities if fœtus is exposed)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

When is organogenesis?

A

Weeks 3-8 aka Embryonic period

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What axes does the human body have?

A

3

Rostrocaudal (AP)- front of brain to back

Dorsoventral- back to front

Left-right

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

When do axes need to be established?

A

Before organ formation

Axis establishment begins in the primitive node

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Notochord: what, when formed, where?

A

Signaling center, for induction of axial skeleton and neural plate (neurulation)

Formed during gastrulation by mesoderm

Extends through length of future vertebral colum and up to anterior end of midbrain
-splits embryo into 2 equivalent sides

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What does the notochord signal?

A

The ectoderm

To form the thick and flat neural plate (neuroectoderm)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Neurulation

A

Folding of neural plate into neural tube-> which later differentiates into CNS (spinal cord and brain)

Forms primitive CNS

Neurula

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

NTDs

A

Neural tube defects-> defects of brain or spinal cord

-when it fails to close in specific regions

Most common are spinabifida and anencephaly

Factors that cause NTD
-genetic
-nutritional (insufficient folate-B9)
-environmental
-multi factorial)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Types of NTDs

A

Anterior
-Anencephaly
-Iniencephaly

Middle
-Craniorachischisis
-Encephalocele

Posterior
-Open spinal bifida
-Closed spina bifida

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Folic acid relevance regarding NTDs

A

Folic acid supplementation before conception and during trimester 1 can reduce NTDs by 50%

In US, added folic acid to grains-> 28% decline in NTD affected pregnancies

17
Q

Laterality

A

Establishment of left-right axis

Determined by left-right asymmetric gene expression

-nodal cilia’s rotary action drives and maintains expression

Establishment of left side: FGF8-> NODAL-> PITX2

18
Q

PITX2

A

Transcription factor and master-gene for left-sidedness

19
Q

Establishment of anteroposterior axis

A

Regulated by combinatorial expression of Homeobox (HOX) genes

HOX genes are:
-transcription factors
-expression regulated by different levels of Retinoic acid (RA)
-highly conserved

20
Q

Laterality defects

A

Situs invertus

1:10,000

Genetic- >100 genes linked

Isolated or syndromic

21
Q

Types of situs inversus

A

Situs inversis totalis- all organs reversed

Situs ambiguous (heterotaxy)- one or more organs reverse
-big issue