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Flashcards in Development Of The Limbs Deck (28):
1

During which time period of gestation do the limb buds appear?

The end of the 4th week

2

Describe the overall structure of the limb bud

Made up of mesenchymal cells from the lateral mesoderm covered in ectoderm

3

What is the name given to the thickened ectoderm at the apex of the limb bud?

Apical ectodermal ridge (AER)

4

The apical ectodermal ridge (AER) is responsible for determining which axis during development of limbs?

Proximal to distal

5

The zone of polarising activity (ZPA) forms which axis during development of limbs?

Anterior to posterior

6

What feature is responsible for determining the dorsal to ventral axis during limb development?

The ectoderm

7

The zone of polarising activity (ZPA) has what role during development of the limbs?

Signalling centre for patterning and maintaining the AER
Generation of asymmetry in the limbs

8

How are digital rays produced in the hand and foot plates?

Condensation of the mesenchyme within the plates beginning with the border rays

9

What substance forms models of the proximal bones during limb development?

Hyaline cartilage

10

What happens between the digits in order to get rid of the tissue that is not needed?

Apoptosis

11

As the AER regresses by apoptosis, does it remain anywhere during development of the limbs?

At the tips of the digital rays

12

What is syndactyly?

Fusion of digits (either just connective tissue or bone also)

13

What is polydactyly?

Extra digits

14

What is amelia?

Complete absence of a limb

15

What is meromelia?

Partial absence of one or more limb structures

16

What is phocomelia?

Where the hands or feet are attached directly to the trunk- limbs are grossly underdeveloped or absent

17

An intrinsic error in the coordination of morphogenesis during limb development is known as what?

Malformation

18

Deformation in morphogenesis is formed by what process during limb development?

Constriction bands (entrapment of fatal parts in utero)

19

How might disruption of morphogenesis during limb development occur?

Via external agents such as thalidomide or infections (HSV, rubella)

20

The upper limb bud appears opposite which spinal segments?

Caudal cervical

21

The lower limb bud appears opposite which spinal segments?

Sacral and spinal segments

22

At what stage of gestation do digits become apparent?

7th-8th week

23

The ventral compartment forms the ________ muscle mass compartment during limb development

Flexor

24

The dorsal compartment forms the _________ muscle mass compartment during limb development

Extensor

25

The upper limb rotates in which direction?

Laterally
(Thumb moves laterally)

26

The lower limb rotates in which direction?

Medially
(The big toe rotates medially)

27

Before rotation of the limbs how are the thumbs, palms and elbows of the upper limb placed?

The thumbs face up, the palms face each other and the elbows point out

28

Before rotation of the limbs how are the feet and knees positioned?

Soles of the feet are facing one another and the knees point out