Development of the Muscular System: Derivatives of the Mesodermal Layer

What is Paraxial Mesoderm

Longitudinal blocks of tissue on either side of the notochord

What does paracial mesoderm give rise to

Axial skeleton and skeletal muscle

What does intermediate mesoderm give rise to

urogenital system

What does the lateral plate mesoderm do

Gives rise to connextive tissue and skelton of the limbs and smooth muscle and viscera and blood vessels

How many somitomeres are there

7

Where are somites

caudal

What is growth/diffrentiation regulated by

HOX

What kind of mesoderm does sclerotome, myotome, and dermatome

Paraxial

What does splanchic somatic extraembroynic

Lateral

What does kidneys and gonad

Intermediate

What does the paraxial mesoderm condense to form

Somites

What model is used to describe somite segmentation

clock and wavefront

What regulates interactions between physically adjacent cells

notch

Where does notch protein accumulate

presomatic mesoderm

When does notch decrease

as the somite is established

What controls the boundaries of somite formation

Retionic acid

What contributes to the regulation of somite formation

FGF8 and WNT3a

Where are FGF8 and WNT3a primarily expressed

caudally

Where is less FGF8 and WNT3a detected

Cranially

1

neural tube

2

Somite

3

notochord

What does the somite divide into

3 parts

What are the parts of a somite

Sclerotome, dermamytome

Where is the sclerotome

Ventromedial part closest to notochord

What does the dermatome become

demis

What does the myotome do

gives rise to muscles

Where do sclerotome cells move

medially

Where do sclerotome cells condense

around notochord

Where does resegmentation take place

only in the sclerotome

What happens to the rostral and caudal halves of somites?

Segregate and refuse with their neighboring halves to form vertebrae

What is bound together

‘c’ of 4, ‘n’ of 5, for example

What forms the vertebrae

the sclerotome

What HOX does cervical

5

what hox does thoracic

69

what hox does lumbar, sacral, and coccygeal

10

Step one of molecular regulation of somite differentiation

Noggin and SHH induce the ventromedial portion of the somite to make a sclerotome

Step two of molecular regulation of somite differentiation

Sclerotome cells express PAX1

What does PAX1 do

Initiates cascade of cartilage and bone forming genes for vertebral formation

What does expression of PAC3 do

Marks dermamytome region of somite

What regulates PAX3

WNT proteins

What is step 4 of molecular regulation of somite differentiation

WNT targets dorsomedial portion of the somite

What does WNT express in the 4th step

MYF5

What does MYF5 form

epaxial muscle

Wgar stimulates MYOD

WNT, BMP4/FGF

Where is MYOD expressed from

dorsolateral somite

What does MYOD form

Hypaxial muscle

What is the midportion directed by

Neurotrophin 3

What does the midportion form

Dermis

What family are MYOD and MYF5 from

Myogenic regulatory factors

What marks dermamyotome region

Expression of PAX3

What do cords contain

root

what does spinal nerve contain

ramus

Where does intermediate mesoderm position itself

posterior abdominal wall

What does the intermediate mesoderm form

Gonads, ducts, accessory glands of urniary and repro tracts

What is sirenomyelia

fusion of lower limbs

What does diabetes do for caudal dysplasia

Increases the chances heavily

Where is somatic

wall of the body cavity

Where is splanchnic

Bisceral (innervated by autonomic)