Limb defects

What are the 4 types of congenital defects ?

1. Reduction defects (mero (partial) or amelia (full) absence of limb)

2. Duplication defects: polydactyl (6 fingers on one hand

3. Dysplasia: abnormal formation - anomalies in the signalling to cells. Syndactyly (fusion)

4. Deformation - physical forces deform the limb

What does melia mean ? Dactyly ? Podia ? Cheiria ?

• Melia: limbs

• Dactyly: fingers

• Podia: feet

• Cheria - hands

Common terms for limb anomalies: describe acheira ? Apodia ? Acheiriopodia ? Adactyly ? Amelia ? Ectromelia ? Arachnodactyly ?Brachydactyly ? Camptodactyl ? Clinodactyly ? Hemimelia ? Meromelia ? Oligodactyly ? Phocomelia ? Polydactyly ? Slit hand or foot ? Syndactyl ? Synostosis ? Triphalyngeal thumb ?

Acheira - absence of hand

Apodia - absence of foot

Acheiriopodia - absence of leg and foot (most likely bilateral

Adactyly - absence of all the digits on one limb

Amelia - absence of 1 limb

Ectromelia - absence of more than 1 limb

Arachnodactyl - elongated digits

Brachydactyly - shortened digits

Camptodactyly - flexure contracture of a digit (usually 4th or 5th) - inability to extend properly

Clinodactyly - little finger curling towards the ring finger.

Hemimelia - absence of pre or post axial structures

Meromelia - absence of part of a limb

Oligodactyly - absence of any number of digits

Phocomelia - absence of proximal limb structure.

Polydactyly - additional digits

Slit Hand or Foot - absence of central components of hand or foot.

Syndactyly - fusion of digits

Synostosis - fusion of bones

Triphalyngeal thumb - thumb has 3 phalynges not 2

What is the three etiology explanations ?

Genetic: mutations in a single gene, abnormal gene expression, chromosomal anomalies, single defect or syndrome

Environmental teratogens: Thalidomide, Varicella, Warfarin, Cocaine and FAS

Fetal maternal environmental factors: Hyperthermia, Oligohydramnios (linked to amniotic fluid, linked to clubfoot), Congenital varicella infection, Gestational diabetes

Triphalyngeal thumb is an example of ?

Dysplasia

The Apical Ectodermal Ridge (AER) disappears when:
A. All segments have been specified proximodistally
B. Ossification begins
C. The ZPA completes digit patterning
D. The dorsal–ventral axis is formed
E. Neural crest cells reach distal limb

A: All segments have been specified proximodistally

The earliest sign of digital formation is:
A. Chondrification of phalanges
B. Formation of digital rays
C. Apoptosis of interdigital tissue
D. Extension of dermatomes
E. Ossification centres appearing

Formation of the digital rays