Lower Limb Development

Question 1

what week does AER form

Answer 1

wk 5 (ectoderm)

Question 2

week 4/5

Answer 2

Lower limb buds lie opposite
to the developing lumbar and
sacral portions of the spinal
cord

Question 3

Preaxial compartment contains

Answer 3

developmentally ventral muscles (includes flexors

Question 4

Postaxial compartment contains

Answer 4

developmentally dorsal muscles (includes extensors)

Question 5

Future hallux is directed

Answer 5

superiorly/cranially and associated with preaxial border

Question 6

Future 5th digit is directed

Answer 6

inferiorly/caudally and associated with postaxial border

Question 7

week 6

Answer 7

coronal to sagital rotation
established thigh and leg segments
buddha sit: knees lateral, soles of feet medial
toe rays visible

Question 8

week 7

Answer 8

medial rotation of 90 degrees
knees now cranial
feet start to be pronated
tootsies with webbing

Question 9

week 8

Answer 9

splayed tootsies

equine supination of foot and adducted compared to leg

Question 10

equinus means

Answer 10

foot is plantar flexed

Question 11

he preaxial border and future hallux begin on the superior aspect of the limb bud and end on the

Answer 11

The preaxial border and future hallux begin on the superior aspect of the limb bud and end on the medial
side of the limb.

Question 12

The postaxial border and future 5th digit begin on the inferior aspect on the limb bud and end

Answer 12

The postaxial border and future 5th digit begin on the inferior aspect on the limb bud and end on the lateral
side of the limb.

Question 13

Three Stages Of Endochondral

Ossification

Answer 13

1. Mesenchymal
2. Cartilaginous*
3. Osseous
   * During this stage joints form

Question 14

Week 5 skeletal

Answer 14

Mesenchymal condensations in
proximal limb (e.g., femur) are
distinct

Question 15

Week 6 skeletal

Answer 15

Chondrocytes form the first hyaline 
cartilage models & joints form
• Mid-week: femur, tibia, & to a lesser 
extent, the fibula chondrify
• End of week: tarsals and metatarsals
chondrify

Question 16

Week 7 skeletal

Answer 16

Chondrification is occurring in all

elements except distal phalanges

Question 17

Week 8 skeletal

Answer 17

Distal phalanges of the toes chondrify

Question 18

Week 12 skeletal

Answer 18

Many, but not all primary 
ossification centers are present 
in long bones. For example, the 
navicular is usually the last 
lower limb bone to start 
ossification ( ~3 yrs)

Appearance of primary centers
of ossification will be covered as
we visit each bone.

Question 19

~ Week 5 arterial

Answer 19

Primordial Blood Supply = Axis a.
Arises from a branch of the umbilical artery
Terminates as foot plexus

Over next couple of weeks
Axis a. regresses
External iliac a. elongates to form Femoral

Question 20

Week 8 arterial

Answer 20

Adult pattern achieved
Remnants of the Axis 
include:
 inferior gluteal 
 artery to sciatic 
nerve (can also come off 
inferior gluteal itself)
 segment of popliteal
 segment of fibular 
(peroneal)

Question 21

ROTATION of Hindlimb

Answer 21

Preaxial border has moved ventrally
Postaxial border has moved dorsally

Most, but not all dorsal muscles have moved superiorly
Those that remain are associated with the postaxial border
Most, but not all ventral muscles have moved inferiorly
Those that remain are associated with the preaxial border

Question 22

Posterior division branches form nerves

that supply the developmentally

Answer 22

dorsal muscles

Question 23

Anterior division branches form nerves that supply

the supply developmentally

Answer 23

ventral muscles

Question 24

ventral division of lumbar plex

Answer 24

obturator

Question 25

Developmental Anomalies: POTENTIAL CAUSES

Answer 25

``` Genetic factors  Mutant genes  Environmental factors  Multifactorial inheritance  Reduced vascular supply ```

Question 26

Congenital Hip Dysplasia

Answer 26

Abnormal development of the the hip joint  Commonly associated with joint capsule

Question 27

Talipes Equinovarus/Congenital Clubfoot

Answer 27

midfoot Cavus • forefoot Adduction • heel Varus • ankle Equinus