090914 dev of skeletal tissue

Question 1

embryonic progenitor tissue from which skeletal tissue is derived

Answer 1

mesenchyme

Question 2

mesenchyme derived from

Answer 2

can be from more than 1 germ layer

Question 3

embryo has two types of tissues

Answer 3

mesenchyme

epithelial

Question 4

for skeletal tissue that’s not in the head, the mesenchyme is derived from

Answer 4

paraxial mesoderm (somites)
somatic mesoderm (part of lateral mesoderm)

Question 5

skeletal progenitor cells

Answer 5

often migrate or are displaced from original site of origin

skeletal tissue forming mesenchyme (STFM) often condenses into pre-skeltal condensations

Question 6

differentiation of STFM is influenced by

Answer 6

epithelial-mesenchymal interactions
specific transcription factors
other signaling molecules

Question 7

Sox 9

Answer 7

chondroblast-specific transcription factor; master gene

activates expression of several genes that are activated only in cartilage forming cells

not involved (as for Runx2 as well) in patterning of skeletal elements

Question 8

ex of epithelial mesenchymal interactions inovlved in support tissue formation

Answer 8

AER and mesenchyme for the limb
neural tube and mesenchyme for the skull and vertebrae
notochord and mesenchyme for the skull and vertebrae

Question 9

development of supporting tissues-initial step is?

Answer 9

condensation of preskeletal mesenchyme

Question 10

preskeletal condensation will be influenced by what?

Answer 10

Sox 9 to become cartilage or cartilage model of bone

or

Runx2 to become bone by intramembranous ossification

Question 11

sites of intramembranous ossification in development

Answer 11

skull, face, middle of calvicle

Question 12

first ossificiation centers appear when?

Answer 12

7 weeks

Question 13

secondary ossification centers appear when

Answer 13

perinatal, postnatal, postpuberal

Question 14

when do secondary ossification centers close

Answer 14

20-30s (remember the vertebrae)

Question 15

skeletal tissue dysplasias

Answer 15

often affect growth, can result in short or tall stature

often a component of ECm is defective

often there is a genetic component

Question 16

Marfan’s disease

Answer 16

alteration of fibrillin production

Question 17

mucopolysaccharidoses

Answer 17

defect in synthesis, storage or transport of glucosaminoglycans and hyaluronic acids, etc..results in accumulation of substrate

Question 18

altered growth hormone’s effects on skeletal growth

Answer 18

increased amts-gigantism

decreased amts-pituitary infantilism (type of dwarfism)

Question 19

altered thyroid hormone’s effects on skeletal growth

Answer 19

decreased amts-cretinism (type of dwarfism)

Question 20

achondroplasia

Answer 20

autosomal dominant mutation in the gene encoding fibroblast growth factor receptor 3 (FGFR3)

champagne pelvis
bow legs
short stature
proximal long bones affected (remember child in bathtub mneumonic)

Question 21

how do you get secondary bone from primary bone?

Answer 21

resorption by osteoclasts and then replacement

Question 22

osteopetrosis and treatment

Answer 22

osteoclast abnormality

treatment: bone marrow transplant

Question 23

blue sclerae indicates… and treatment

Answer 23

defect in collagen type I

treatment is to inhibit osteoclasts (will see lines where bone has been laid down due to treatment)