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Flashcards in Early Embryonic 2 Deck (17)
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0

Define the bilaminar disc

Epiblast and hypoblast derived from embryoblast
Later forms trilaminar disc with formation of primitive streak

1

Define the germ layer

A layer from which other developed tissues originate from

2

What is the ectoderm?

Outermost layer of cells, giving rise to the epidermis and nerve tissue

3

What is the endoderm?

Innermost layer of cells giving rise to the gut lining

4

What is the mesoderm?

Middle germ layer, gives rise to muscle and bone

5

What is the primitive streak?

Narrow groove that develops on the dorsal(outer) surface of the epiblast
Orientates the embryo

6

What is gastrulation?

Reorganaisation of germ layers into the ectoderm, mesoderm and endoderm establishing the origin of all tissues

7

What is the trilaminar disc?

3 germ layers
Ectoderm, mesoderm and endoderm

8

List derivatives of the ectoderm

Skin
Hair, nails
Brain and spinal chord
Peripheral nerves
Retina and iris of eye

9

List mesodermal derivatives

Smooth,skeletal and cardiac muscle
Connective tissue
Bone
Cartilage
Blood and blood vessels
Urinary system

10

What are the endodermal derivatives?

Lining of digestive tract
Digestive glands
Gut derivatives e.g. Lungs

11

Describe migration and invagination during week 3

Cells on the epiblast migrate towards the primitive streak
They invaginate the epiblast and displace the hypoblast creating trilaminar disc
As more cells migrate through the streak they spread laterally and cephalod mesoderm spreads out between the ecto and endoderm leaving two gaps

12

Why does the mesoderm leave two gaps?

Vascularised so areas with gaps will becom necrotic and disintegrate leaving future mouth and anus

13

What is the notochord?

The notochord defines the phylum chordata, basis for the axial skeleton, drives formation of the nervous system

14

How is the notochord formed?

Prenotochordal cells of epiblast migrate through cranial part of primitive pit forming a solid rod of cells running in the midline eith an important signalling role

15

What happens to the notochord?

It regresses
The vestigial remenant in adults is the nucleus pulposus of intervertebral discs which acts as a shock absorber

16

What ensures correct left right development?

Molecular signals from primitive node are wafted by cilliated cells to left side