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Flashcards in Early Embryonic 3 Deck (12)
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Describe differention of the mesoderm into the notochord

Mesoderm differentiates into the notochord during gastrulation. The notochord signals the ectoderm to convert to nueroectoderm which is thicker and the edges start to fold forming the nueral tube

1

Describe the differentiation of mesoderm into somites

The first lair of somites appears at day 20 in the occipital region. More sppear in cranio-caudal sequence at 3 pairs/day until 42 pairs, some dissapear leaving 31
-somites appear as regular block of mesoderm arranged around a small cavity, then organaised degeneration of the ventral walls forms sclerotome

2

Describe differentiation of the mesoderm into the intermediate mesoderm and lateral plate (somatic and splanchic)

Appearance of somites organaises the mesoderm into segments. The lateral plate mesoderm splits into somatic and splanchic, with the intraembryonic coelem between
Mesoderm in between is the intermediate mesoderm

3

Describe the formation of the coelom

As the mesoderm differentuates the intra embryonic coelom is formed between the somatic and splanchic mesoderm.
As the embryo folds laterally the lateral branches of mesoderm connect to form the coelom

4

List derivatives of the paraxial mesoderm

Axial skeleton
Dermis
Muscles of axial body wall
Some limb muscles

5

List derivatives of the somatic mesoderm

Connective tissue of limbs
Axial body wall

6

Splanchic mesoderm

Smooth musculature
Connective tissue and vasculature of gut

7

I mediate mesoderm

Urogenital system e.g. Kidney, ureter, gonads

8

Describe the cephalo-caudal folding of the embryo

To start heart lies at cranial end
moves inwards with folding, until it ends up in the future chest
The yolk sac extends out of the embryo to form connection between yolk and gut

9

Describe lateral folding of the embryo

Draws together margins of disc:
-Creating ventral body wall
-Amniotic membrane around disc so embryo suspended within amniotic sac
-pull connective stalk vertically

Creates the primordium of the gut from the yolk sac, puts the heart snd primordium of the diaphgram in the right place creating a new cavity within

10

Describe the differentiation of the somites into dermatone, myotome and sclerotome and the fate of these in ,ater development

Organaised degradation of somites forms sclerotome
Further organaisation of the dorsal portion forms the dermomyotome
Myotome proliferates and migrates and the dermatome disperses

Dermatome - skin(dermis)
Myotome - muscle
Sclerotome - hard tissue (bone)

11

Explain use of dermatone and myotome when describing innervation of skin and muscles in the adult

Dermatome is strip of skin supplied by a single spinal nerve
Myotome is a muscle group supplied by a single spinal nerve

Neural tube produces nerve that innervates the dermomyotome