Mesodermal Layer

Question 1

Paraxial mesoderm (overview)

Answer 1

longitudinal blocks of mesoderm on either side of notochord

becomes axial skeleton and skeletal muscle

Question 2

Intermediate mesoderm (overview)

Answer 2

gives rise to urogenitals

Question 3

Lateral plate mesoderm (overview)

Answer 3

gives rise to connective tissues, appendicular skeleton
smooth muscle
connective tissue of viscera and blood vessels

Question 4

Paraxial M. —-> what two important structures on developing embryo

Answer 4

Somitomeres (cranially) and Somites (caudally from occipital region)

Question 5

Paraxial meso produces the ____ and somites

Answer 5

head

Question 6

somites develop into

Answer 6

sclerotome (cartilage), myotome (skeletal muscle), dermatome (dermis)

Question 7

the D.M.S

Answer 7

dermatomes, mytotomes, sclerotomes all from paraxial

Question 8

“clock” and wavefront model

Answer 8

somites develop according to this model of gene expression. there are four regions

it begins posteriorly and moves anteriorly (I think)

Question 9

“waves”

Answer 9

development of somites uses the segmentation clock of cyclic expression of NOTCH and WNT signaling pathways.

Question 10

Notch

Answer 10

notch protein accumulates in presomitic mesoderm destined to form the next somite and then decreases as that somite is established

the increase in notch protein activates other segment patterning genes that –> somite

Question 11

ok, so the “simple” version of notch

Answer 11

notch protein accumulates and activates other Somite differentiating genes

Question 12

what regulates the “boundaries” of each somite?

Answer 12

retinoic acid (RA) and FGF8 and WNT3

Question 13

RA is expressed in high concentrations ____ and ______ ______

Answer 13

cranially, but decreases concentration caudally

FGF8 and WNT3 expressed higher in caudal region

Question 14

RA, FGF8 and WNT3 concentrations

Answer 14

RA cranially, FGF8/WNT3 caudally

THESE control the segmentation clock and activity of NOTH pathway

Question 15

Sclerotomes

Answer 15

ventromedial portion closest to the notochord, develops into skeletal parts

Question 16

Dermamyotome

Answer 16

divides into the dermis

Question 17

Epidermis develops from ____ while dermis develops from

Answer 17

ectoderm, paraxial mesoderm

Question 18

myotome

Answer 18

develops into muscle

Question 19

which of the DMS move medially and concentrate around the notochord?

Answer 19

the sclerotomes

Question 20

which of the DMS is closest to surface ectoderm, and what does it do

Answer 20

dermomyotomes —->

dermatomes (dermis forming) and myotomes (muscle forming)

develops into

Question 21

Resegmentation

Answer 21

only occurs in sclerotome: they divide and then refuse with their neighbor to form vertebrae

Question 22

Sclerotomes do what

Answer 22

they condense around the notochord and form the vertebrae

Question 23

Hox gene control of somite development into vertebrae

Answer 23

it’s not a “one to one” basis but through hox gene interactions

Question 24

the “big” hox genes noted in class were

Answer 24

hox5-hox6 –> cervical v.
ho6-hox-9 –> thoracic
hox 9+ hox X–> lumbar/Sacral/Coccygeal

Question 25

epaxial genes =

Answer 25

MYF5

Question 26

hypaxial genes =

Answer 26

MYOD

Question 27

dermis forming genes =

Answer 27

NT-3

Question 28

MRFs

Answer 28

myogenic regulatory factors, essentially transcription factors

Question 29

Dermatome ---> Myotome --> Sclerotome -->

Answer 29

dermis + nerve component | epaxial/hypaxial muscles+ nerve component (dorsal/ventral rami)

Question 30

intermediate mesoderm

Answer 30

most to posterior wall to form gonads, ducts, accessory glands or urinary reproductive tracks

Question 31

Caudal Dysplasia

Answer 31

total or partial failure of development of the lower vertebrae, including sacrum results in associated abnormalities of lower extremities: spine, kidenys, gastrointestinal and genitourinary tracks BROAD range of symptoms/abnormalities

Question 32

Caudal Dysplasia MAY reflect _______ (3 things) but is highly associated with

Answer 32

toxic, infective, or ischemic insult there is a significant association with maternal diabetes

Question 33

Lateral Plate mesoderm ---> (from colorful image she showed a zillion times)

Answer 33

splanchnic mesoderm (circulatory system and visceral mesoderm), somatic mesoderm, extraembryonic mesoderm

Question 34

Somatic

Answer 34

wall of body cavity

Question 35

Splanchnic

Answer 35

viscera

Question 36

In the lateral plate mesoderm, splanchnic or somatic is closest to the intraembryonic coleom?

Answer 36

Splanchnic

Question 37

The embryonic gut tube is surrounded by

Answer 37

lateral plate splanchnic mesoderm, which is surrounded by lateral plate somatic mesoderm, which is surrounded by ectoderm on the surface

Question 38

somatiopleure

Answer 38

somatic mesoderm surrounding the splanchnic mesoderm which surrounds the gut tube