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0. Basic Concepts / Orientations

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1. What are the five major regions of the mesoderm? I suggest you be able to draw a

diagram of their relative positions.

Dorsal

Mesoderm -

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2. What major tissues are formed from each mesodermal territory?

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2. What major tissues are formed from each mesodermal territory?

Splanchnic Mesoderm

Visceral mesoderminner branch of lateral mesoderm

lays alongside the endoderm (yellow)

Lateral Mesoderm

Becomes part of the musculature of

the digestive system

Becomes incorporated into the

endodermal structures (intestinal

muscles) which eventually becomes a

composition of both endodermal and

mesodermal tissue.

Somatic Mesoderm

outer branch of lateral mesodermLays alongside body wall (ectoderm)

Somatic Somitic dont confuse with somiteSoma = body

Somitic = segmented mass of mesoderm in the vertebrate animal

Coelom :

Lateral plate forms the coelom with its two branches.

Definition of coelom cavity surrounded by mesoderm.

Most of our guts or organs are hanging out in the coelom

Literally a carved out (saved) area were organ s will be

allowed, their formation to expand into.

Echo 09:26 12:30

Slides 8-9

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3. What is presomitic mesoderm?

4. What is paraxial mesoderm?

Dorsal (top) view Notochord

is beneath the neural tube

(cant see)

Anterior-Posterior view (slice)

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5. What is a somite?

A somite is a condensed pinched off bit of paraxial mesoderm.

It is the source of:Spine, Muscles, Tendons, & underlying tissues of the skin.

It contains stems cells that will differentiate into

* Cartilaginous eventually

becomes boney. Ribs andVertebrae for example

* A large portion

of skeletal muscle

*Dermis this is underlying the epidermis of our skin

(beneath the epidermis) and is derived from the

Dermatome.

* A portion of the Skeletal Muscle

Prof Thomsen didnt discuss 4&5

but he did talk about the Head

paraxial (pre-somitic) mesoderm.

Headsome of the skull

structures & vertebrae of thehead are derived from paraxial

mesoderm.

These structures are derived from

the somites way up in the front

of the body (most anterior)

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6. Describe the progression of somite formation over time along the A-P axis

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7. What is the function of FGF expression in the presomitic mesoderm?

8. What is the evidence for a somite clock?

9. What is the Hairy gene, and how does its expression change as the somite clock runs?10. What is the proposed/speculated pathway for the somite clock?

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11. What does Hairy/Hes gene expression regulate?

12. How does the Notch signal transduction pathway work? What is the ligand(s)?

Notch Regulated Genes:

Targets Include:

Hairy1/Hes

Lunatic Fringe

Delta

& others