Limb System

Question 1

limb develops from..

Answer 1

lateral mesoderm

Question 2

what regulates the patterning in the formation of the limbs

Answer 2

homeobox genes

Question 3

how many homeobox genes are there

Answer 3

13

Question 4

when are the upper limb buds visible

Answer 4

day 26-27

Question 5

when are the lower limb buds appear

Answer 5

1-2 days after the upper ones

Question 6

what does the limb bud consist of

Answer 6

a mass of mesenchyme that is convered by ectoderm

Question 7

where is the mesenchye in the limb bud derived from

Answer 7

the somatic layer of lateral mesoderm

Question 8

what is the area at the apex of the limb bud where the ectoderm thickens

Answer 8

AER apical ectodermal ridge

Question 9

what is needed for the AER to get information

Answer 9

BMP signaling

Question 10

what is the multi layer epithelial structure that is induced by underlyinh mesenchyme

Answer 10

AER

Question 11

wat kind of influence does the AER have on limb mesenchyme

Answer 11

indutive influence ( makes it grow and develop)

Question 12

what is at the posterior of the limb bud

Answer 12

ZPA- zone of polarizing activity

Question 13

the fibroblasts growth factors from the AER activate the mesenchymal cells aggreagates at the posterior part of the limb bud called the ZPA, the activation allows for..

Answer 13

Shh -sonic hedgehog genes

Question 14

what do the mesenchymal cells that are close to the AER do

Answer 14

they become blood vessels and cartilage bone models

Question 15

in what week have mesenchymal tissue in the handplates condensed to for digital rays

Answer 15

week 6

Question 16

when do the digita rays in the foot plates form digital rays

Answer 16

week 7

Question 17

what is responsble for the tissue breakdown in the interdigital regions

Answer 17

programmed cell death- apoptosis

Question 18

what is apoptosis mediated by

Answer 18

BMP and TGF-beta superfamily

Question 19

what forms the:

• scapula
• clavicle
• humerus
• radius
• ulna
• carpals
• metacarpals
• phalanges

Answer 19

lateral plate mesoderm

Question 20

which bone undergoes both forms of ossification

Answer 20

clavicle

Question 21

when do chondrification centers appear

Answer 21

5th week

Question 22

when is the whole limb cartiligenous

Answer 22

6th week

Question 23

osteogeneis of long bones start when

Answer 23

week 7

Question 24

what forms a large muscle mass in each limb that will later seperate into extensor and flexor

Answer 24

myoblasts

Question 25

cervical myotome contributes to what

Answer 25

muscles of pectoral girdle

Question 26

lumbosacral myotomes do become..

Answer 26

pelvic girdle

Question 27

which limb rotates laterally 90 degrees on long axis

Answer 27

upper limb

Question 28

which limb rotates medially 90 degrees

Answer 28

lower limb

Question 29

wat forms the neurilemmal and myelin sheath

Answer 29

the neural crest cells that are the precursor for schwan cells surrounding the motor and sensor nerve fibers

Question 30

when do peripheral nerves grow from the limb plexuses into the mesenchym of limb

Answer 30

week 5

Question 31

what is the area of skin that is supplied by a single nerve and its spinal ganglion

Answer 31

dermatome

Question 32

what is the blood suplly to the limbs

Answer 32

branches of the intersegmental arteries that come from the aorta

Question 33

wat is the primordial vascular pattern

Answer 33

there are primary axial artery and its branches, they drain to the marginal sinus

Question 34

what forms the proximla part of the right subclavian

Answer 34

aortic arc 4

Question 35

what forms the distal part of the right subclavian

Answer 35

7th intersegmetnal artery and entire left subclavian artery

Question 36

where axis artery end

Answer 36

terminal plexus ( subcav-> axis-->?

Question 37

terminal plexus helps form what

Answer 37

deep and superficial palmar arch

Question 38

what is responsibel for the formaiton of new vessels

Answer 38

angiogenesis

Question 39

primary axial artery becoes.

Answer 39

brachial artery in the arm and common interosseous artery in forearm

Question 40

in lower limb what is primary axial artery represented by

Answer 40

deep artery of thigh

Question 41

in leg primary axial artery becomes t

Answer 41

tibial arteries

Question 42

when is the most critical days of develoment

Answer 42

24-36th day of fertilization

Question 43

exposure to thalidomide when... will there be severe limb defects like amelia

Answer 43

day 33

Question 44

which one has patial absence of hands, amelia or meroamelia

Answer 44

meroamelia

Question 45

what are genetic factors that can mess limbs up

Answer 45

chromsomsal abnormalities

Question 46

what are the two test that are done to make sure the femur is not falling out of the shallow head of acetabulum

Answer 46

Barlow test and ortolani test

Question 47

which test do you pull the leg laterally and down

Answer 47

ortolani test

Question 48

amnion can seperate from chorion and do what

Answer 48

wrap around digits or neck

Question 49

what is it when there is an absence of one or more central digits and the hand and foot are divided into two parts

Answer 49

lobster claw deformities

Question 50

when radius doesnt form at what time does this happen

Answer 50

week 5

Question 51

polydacryly?

Answer 51

supernumerary digits

Question 52

what is the most common club foot ?

Answer 52

talipes equinovarus

Question 53

in what percent is club foot bilateral

Answer 53

50%

Question 54

club foot is more frequent in who

Answer 54

males