Development of Skeletal Tissue

Question 1

What is the primary skeletal progenitor tissue?

Answer 1

Mesenchyme

Question 2

What is mesenchyme derived from

• in the trunk:
• in the head:

Answer 2

What is mesenchyme derived from:

• in the trunk: paraxial mesoderm, somatic mesoderm
• in the head: Neural crest ectomesenchyme, head mesoderm

(mesoderm becomes mesenchyme)

Question 3

The mesenchyme is derived from

• In the trunk
  
  • paraxial mesoderm
  • domatic mesoderm
• In the head
  
  • Neural crest ectomesenchyme
  • head mesoderm

Question 4

WHat is the “master gene” for Bone?

WHat is the master gene for cartilage?

Answer 4

bone-RUnx2 gene is an osteoblast specific transcription factor

cartilage- sox9 is a chondroblast specific transcription facotr

**expression activates the expression of several genes that are activated only i nbone or cartilage forming cells

**these genes apparently are not involved in patterning of skeletal elements

Question 5

What would happen to a null mutant for runx2

Answer 5

no bones!

skull-fibrous CT

partially calcified cartilagenous skeleton

small with short limbs

Question 6

what is the initial step of developing supporting tissues?

Answer 6

condensation of preskeletal mesenchyme

Question 7

epithelial mesenchymal interactions are usually involved in __________ formation

**give 3 examples

Answer 7

epithelial-mesenchymal interactions are usually involved in support tissue formation

• AER/mesenchyme- limb
• Neural tube/mesenchye- skull , vertebrae
• notochord/mesenchyme-skull, vertebrae

Question 8

How is vitamin D involved in calcium homesotasis and bone formation?

Question 9

what are ossification centers and what can they be used as a measure of?

Answer 9

• areas in the skeleal primordium where ossification occurs
• can be used as a measure of skeletal maturation and development
• primary and secondary

Question 10

what is a primary ossification center?

Answer 10

• the initial center to appear: shaft of long bone, center of flat bone
• first aooears at 7 weeks of development
• a bone may have one center or multiple centers

Question 11

what is a secondary ossification center?

Answer 11

appear in perinatal, postnatal or post pubertal period

ends of long bone (epiphysis), heads of ribs etc.

close in 20s-30s

hormonal control of maturation, estrogen, thyroid hormone

Question 12

what is bone age? how do we measure skeltal growht and maturation?

Answer 12

bone age-amount o fepiphyseal cartilage retaines

comparison of bone and chronological ages is a measue of skeletal growth and mutation

Question 13

where do generalized skeletal tissue dysplasis usually affect? what is often wrong?

Answer 13

• may affect all or part of skeleton
• often affect growth and may result in short or tall stature
• often a component of the ECM is defective
• often there is a recognized genetic component

Question 14

What is mucopolysaccharidoses?

Answer 14

defect in synthesis, storage or transport of a particular lysosomal enzyme; results in accumulation of substrate

Question 15

what is marfans?

Answer 15

alteration of fibrilin production

Question 16

what can increased amounts of growth hormone lead to?

How about decreased amounts?

Answer 16

increased- gigantism

decreased-pituitary nfantilism (type of dwarfism)

Question 17

decreased amount sof thyroid hormone can lead to what?

Answer 17

decreased amounts lead to cretinism (a type of dwarfism

Question 18

bone can form by 2 ways what are they?

Answer 18

• directly from mesenchyme (intermembranous ossification) or by replacing a cartilage model (endochondrial ossification)

Question 19

primary and secondary ossification centers from ________

Answer 19

in bones

Question 20

determination of ______________ is a useful indicator of skeltal growth and maturation

Answer 20

determination of the amount of epiphyseal cartilage (bone age) is a useful indicator os skeletal growth and maturation