Embryo - Dev. of Muscular System

Question 1

What do somites become?

Answer 1

Vertebrae, back muscles, dermis of skin

Question 2

Mesoderm -> Paraxial mesoderm -> _____

Answer 2

Somites

Question 3

Mesoderm -> _______ -> Somites

Answer 3

paraxial mesoderm

Question 4

Somites are more segmented cranially or caudally?

Answer 4

Cranially, and are more unsegmented caudally

Question 5

Sclerotome

Answer 5

1. Ventral medial portion of somites that have become mesenchymal and wrapped around the neural tube.
2. Eventually differentiates into vertebrae and ribs.

Question 6

Dermatome

Answer 6

1. Formed by cells in between the upper dorsomedial and ventrolateral portion of somites.
2. Forms the dermis of the back

Question 7

PAX-1 expressed by somites is induced by what and causes what?

Answer 7

1. Induced by SHH and noggin from notochord and floor plate of neural tube
2. Controls chondrogenesis and vertebrae formation

Question 8

Dermomyotome signalling, what, from where

Answer 8

WNT from Dorsal neural tube activates PAX3 which demarcates the dermomyotome.

Question 9

Mid dorsal somite (dermatome) becomes _____ when _____ is expressed?

Answer 9

NT-3 directs the dermatome to become dermis

Question 10

The dorsomedial portion of the somite becomes _____ and expresses _____ when _____ is expressed.

Answer 10

1. It becomes muscle precursor cells
2. Expresses MYF5 (muscle specific gene)
3. WNT induces all of this

Question 11

Paraxial mesoderm gives rise to?

Answer 11

Axial skeleton and skeletal muscle

Question 12

Segmentation of axial mesoderm is controlled by _____

Answer 12

Hox genes

Question 13

Segmentation Clock

Answer 13

Waves of gene expression that end up building somites proximal to distal

Question 14

PAX1 is expressed by ______

Answer 14

sclerotome

Question 15

MYOD is expressed by cells that become _____ muscles.

Answer 15

Hypaxial

Question 16

MYF5 is expressed by cells that become ______ muscle cells

Answer 16

epaxial

Question 17

Type I diabetes can lead to ______

Answer 17

Sirenomelia/lower limb defects (in utero the fetus can have “frog-legs”