Lecture 7- MSK Development Flashcards Preview

Block 2 - MSK > Lecture 7- MSK Development > Flashcards

Flashcards in Lecture 7- MSK Development Deck (30):
1

When does limb development occur

- week 3-8

2

Stages of development

- Blastocyst: first 2 weeks
- Embryonic: week 3-8
- foetal: week 9+

3

Gestional age vs embryonic age

- Gestional age: time since last menstuation
- Embryonic age: time since fertilisation

4

When do limb buds appear

Week 4

5

When do hand plates and digital rays appear

Weeks 5,6

6

When do webbed digits appear

Weeks 7,8

7

Appearance of
- upper limb buds
- lower limb buds
- joints of hand

- mid 4th week
- 2 days later
- day 47

8

2 specialized structures in the limb buds

- Apical ectodermal ridge: ridge of cells around the dorsoventral axis
- Zone of polarizing activity: group of cells on posterior margin of limb bud

9

Limb positioning controls

- hox genes in embryonic trunk -> FGF10 on lateral plate mesoderm -> Wnt3 in overlying ectoderm -> dorms AER and induces expression of FGF8

FGF8: proliferation of mesenchyme cells
- positive feedback loop

10

Determining the identity of limbs

- Tbx5: forelimb
- TBx4 and Pitx1 hindlimb
- Tbx2/3: both limbs

11

Proximal distal axis of limb
- Signaling center
- molecular signal

- AER
- FGf8

12

Antero-posterior axis of limb bud
- signaling center
- molecular signal

- ZPA
- shh gradient posterior to anterior

13

Dorso-ventral axis of limb bud
- signaling center
- molecular signal

- Dorsal and ventral ectoderm
- Molecular signal: Wnt7a (dorsal), En-1 (ventral)

14

Programmed cell death

- shaping of limb structures
- BMP are involved in this process

15

Bone formation

- mesenchyme initially condences into cartilage
- ossification starts in shafts of long bones and secondary sites at the end of bones

16

Vasculature

First blood vessels formed by vasculogenesis
- vessels form de novo in embryonic mesenchyme
- Endothelial precursor cells form an aggregate and produce a small single-layered endothelial tube with a lumeb
- VEGF involved

17

Nerved

- develop as dermatomes
- first parallel then mixed up

18

Musculature

- muscle precursors migrate frm the somites of the animal into the limb to form muscles
- Lbx1 gene required for migration

19

Syndactyly

Fusion of digits
- BMP or Shh disruption

20

Polydactyly

- extra digits
- Shh disruption

21

Triphalangeal thumb

- shh disruption

22

Amelia

Absence of an entire limb
- early loss of Fgf signalining

23

Meromelia

Absence of part of a limb

24

Adactyly

Absence of digits: late loss of Fgf

25

Thalidomide effects

- loss of immature blood vessel
- mesenchymal cells cant proliferate
- longer exposure to FGF8 in AER
- more distal structures, less proximal structures

26

Developmental displasia of hip

1/1000
- female predominance
- first born
- increased risk with breech position and big baby

TREATMENT: Pavlik harness

27

Perthes disease

- hip of growing children
- more common in boys aged 4-10
- disruption of blood supply to part of femoral head
- softening and collapse of bone
- unknown cause
- inflammation, limping
- broomstick plasters
- good prognosis

28

Club foot (Talipes)

- most common muscoloskeletal defect in children
- constriction of feet in breech position -> inturned feet)
- males

TREATMENT
- gradual plastering technique
- 95% success rate

29

Toewalking

- walking on toes or ball of fooot
- can be habitual/idiopathic

TREATMENT
- stretching and strengthening

30

Calcaneal apophysitis: Sever's disease

- inflammation of growth plate
- heel pain
- one or both heal
- stress/overuse/obesity/ tight achilles tendon
- pain, limping, toewalking

TREATMENT
- reduce activity, calf stretcking, orthotis, ibuprofen