Devo of Vertebral Column, Ribs and Sternum

Question 1

How does the scleratome form?

Answer 1

Cells in the ventromedial/ventral half of the somite are influenced by Shh and noggin

In response, the ventral somite cells express Pax1 and Pax9 – induces proliferation and epithelium to mesenchyme transformations

The newly formed mesenchymal cells is the scleratome

Question 2

How does scleratome mesenchyme become a vertebrae?

Answer 2

Resegmentation: the cranial half of one somite merges with the caudal half of the next adjacent somite

As a result, vertebrae become intersegmental with respect to the orignal somite segmental pattern.

Skeletal muscles derived from dermomyotomes can span adjacent vertebrae

Question 3

What does the central subdomain of scleratome tissue produce?

Answer 3

Pedicle

Proximal rib

Question 4

What does the Ventral subdomain of scleratome tissue produce?

Answer 4

Vertebral body, IV disc

Question 5

What does the Dorsal subdomain of scleratome tissue produce?

Answer 5

Dorsal part of neural arch, spine

Question 6

What does the Lateral subdomain of scleratome tissue produce?

Answer 6

Distal rib

Question 7

What does the Somitocoel subdomain of scleratome tissue produce?

Answer 7

Vertebral joints, IV disc, proximal ribs

Question 8

Cells from the cranial half of scleratome contribute to:

Answer 8

Vertebral body, small parts of neural arch and distal rib

Question 9

Cells from the caudal half of the scleratome contribute to:

Answer 9

Vertebral body, transverse process, most of neural arch and proximal part of main part of distal rib

Question 10

What do cells from the cranial and caudal parts of the scleratome form?

Answer 10

Cranial half forms vertebral body, small parts of neural arch and distal rib

Caudal half forms vertebral body, transverse process, proximal rib, main part of distal rib and main part of neural arch

Question 11

What gene determines the type of vertabra that will form and where it will form?

Answer 11

Hox genes

And retinoic acid

Question 12

By what method do vertebra become bone?

Answer 12

Endochondral ossification

Question 13

How do the ribs form?

Answer 13

Costal processes expand laterally

Proximal portion of rib forms from cells of central scleratome and somitocoel

Distal portion is derived from lateral scleratome cells

Question 14

How does the sternum form?

Answer 14

Begins independently as cartilage bars on either side of midline

Derived from Somatic mesoderm

Bars fuse after embryo folding

Secondary segmentation forms Sternebrae

Refusion of sternebrae forms body of sternum

Cranial most sternebrae forms manubrium

Xiphoid process forms at caudal end

Question 15

What is hemivertebrae?

Answer 15

A remainder of a vertebra that did not form completely

Question 16

What is spina bifida?

Answer 16

Series of conditions where one or a few adjacent vertebrae have unfused spinous processes

Spina bifida occulta is the mildest form, asymptomatic

Question 17

What is sacrilization?

Answer 17

Occurs if fifth lumbar vertebrae is incorporated into sterum

Question 18

What is Kippel-Feil sequence?

Answer 18

AKA brevicollis

Rare, recessive

Characterized by presence of several fused cervical vertebrae

Neck is shortened, low nuchal hair line

Limited spine mobility

Associated with genitourinary and cardiopulmonary defects and hearing loss

Question 19

What is scoliosis?

Answer 19

Abnormal curvature of the spine

Congenital form may be caused by hemivertebrae

Seven times more common in females

Question 20

What is lumbarization?

Answer 20

When the first sacral vertebra is not included in the sacrum

Question 21

What is Rachischisis?

Answer 21

A condition where many or all vertebrae have unfused spinous processes