Embryology

Question 1

At what day does the upper limb bud appear?

Answer 1

Day 24

Question 2

At what day does the lower limb appear?

Answer 2

25/26 days

Question 3

What are HOX genes?

Answer 3

Genes resulting from a combination of expression of SHH, FGF’s , they are regionally expressed in limbs and determine which skeletal element is formed

Question 4

Which genes are expressed in the upper limb?

Answer 4

HOXd 9-13 genes

Question 5

What genes can you remove that and result in the radius and ulna not being formed?

Answer 5

HOXa 11, HOXd 11

Question 6

How do limb buds elongate?

Answer 6

By the proliferation of mesenchyme

Question 7

What do lower limbs buds form opposite?

Answer 7

The lumbar and sacral segments

Question 8

What do upper limbs buds form opposite?

Answer 8

The caudal cervical segments

Question 9

How does the Apical ectodermal ridge form?

Answer 9

The ectoderm thickens at the apex of each bud

Question 10

What role does the Apical Ectodermal RIdge have?

Answer 10

Is a multilayered epithelial structure that exerts an inductive influence on limb mesenchyme

Question 11

What does the mesenchyme adjacent to the AER consists of ?

Answer 11

Undifferentiated rapidly proliferating cells

Question 12

What do the mesenchyme proximal to the AER differentiate into?

Answer 12

Blood vessels and cartilage bone models

Question 13

What are the steps of the fingers and toes forming?

Answer 13

Limb buds,
Paddle shaped hand plates and flipper shaped foot plates,
Digital rays,
Notches between digital rays, 
Webbed fingers and toes,
Separate digits of fingers and toes

Question 14

What mediates apoptosis in fingers and toes?

Answer 14

Bone morphogenetic proteins

Question 15

How do cartilaginous precursors of limb bones develop?

Answer 15

By chondrification within the mesoderm in the 6th week

Question 16

How does ossification appear in week 8 to 12

Answer 16

Primary centres of ossification appear in response to growth factors

Question 17

how do the upper limbs rotate?

Answer 17

Rotate 90degress laterally

So that extensors are on the lateral and posterior surfaces

Question 18

How do the lower limbs rotate?

Answer 18

90degress medically so that the extensors are on the anterior surface

Question 19

How does the dermatomal pattern develop?

Answer 19

During the 5th week, peripheral nerves grow from the developing limb plexus into the mesenchyme of the limbs

Question 20

Define Amelia defect?

Answer 20

Total absence of limbs

Question 21

Define meromelia?

Answer 21

Partial absence

Question 22

Define phocomelia?

Answer 22

Some long bone absence

Question 23

Define micromelia?

Answer 23

All parts present but small

Question 24

Define polydactyly

Answer 24

Presence of more than 5 digits on the hands or feet

Question 25

Define the types of syndacyly?

Answer 25

Cutaneous (simple webbing between the digits) and osseous (fusion of bones)

Question 26

Is syndactyly more common in feet or hands?

Answer 26

Feet

Question 27

What birth defect of the limbs does thalidomide cause?

Answer 27

Meromelia

Question 28

Another name for congenital clubfoot?

Answer 28

Talipes equinovarus

Question 29

How is the foot positioned in talipes equinovarus?

Answer 29

Is turned medically and th foot is inverted

Question 30

Cause of talipes equinovarus

Answer 30

Multifactoral (genetic and environmental factor), abnormal position or restricted movement of the fetus’s lower limb in the utero

Question 31

Define abnormal development of acetabulum

Answer 31

Congenital dislocation of the hip, common after breech

Question 32

Types of developmental dysplasia of the hip?

Answer 32

Abnormal development of acetabulum, generalised joint laxity