Embryology

1. BIRTH DEFECTS OF LIMBS
DR. RABIA INAM GANDAPORE
ASSISTANT PROFESSOR
HEAD OF DEPARTMENT ANATOMY
(DENTISTRY-BKCD)
B.D.S (SBDC), M.PHIL. ANATOMY (KMU),
DIP. IMPLANT (SHARJAH, BANGKOK, ACHERS) , CHPE
(KMU),CHR (KMU), DIP. ARTS (FLORENCE, ITALY)

2. TIMING OF LIMB MALFORMATION
• CRITICAL PERIOD OF LIMBS DEVELOPMENT IS END OF 4RTH WEEK AFTER FERTILIZATION.
• BY 7TH
WEEK FORMATION OF ALL THE PARTS OF THE UPPER AND LOWER LIMBS IS COMPLETE.
• MAJOR MALFORMATIONS APPEAR BY THE 7TH
WEEK OF FETAL DEVELOPMENT.
• MAJOR UPPER LIMB DEFICIENCIES OCCUR AT 28 DAYS.
• MAJOR LOWER LIMB DEFICIENCIES OCCUR AT 31 DAYS.

4. EXTREMITY ANOMALIES CATEGORIZED AS:
• TERMINAL: THOSE IN WHICH MISSING SEGMENT EXTENDS TO THE END OF THE EXTREMITY.
• INTERCALARY: ABSENCE OF THE MIDDLE PORTION OF THE LIMB, PROXIMAL AND DISTAL
PORTIONS ARE PRESENT.

5. TERMINOLOGIES
• PREAXIAL: REFERED TO RADIAL SIDE OF THE UPPER LIMB AND TIBIAL SIDE OF THE LOWER LIMB.
• POST AXIAL: REFFERED TO THE ULNAR SIDE OF THE UPPER LIMB AND FIBULAR SIDE OF THE
LOWER LIMB.
• AMELIA: COMPLETE ABSENCE OF THE LIMB/LIMBS.
• HEMIMELIA: ABSENCE OF ONE OF THE PAIRED BONES.
• PHOCOMELIA: ABSENCE OF ARM AND FORE ARM IN THE UPPER LIMB, THIGH OR LEG IN THE
LOWER LIMB. HANDS AND FEET SPROUT DIRECTLY FROM THE TRUNK.

7. • MEROMELIA: PARTIAL ABSENCE OF LIMB.
• ECTROMELIA: TOTAL OR PARTIAL ABSENCE OF ONE OR MORE LONG BONES OF LIMBS.

10. CAUSES
• GENETIC FACTORS
• CHROMOSOMAL ABNORMALITIES ASSOCIATED WITH TRISOMY 18.
• MUTANT GENES
• AS IN BRACHYDACTYLY, ABNORMAL SHORTNESS OF FINGERS,OR
OSTEOGENESIS IMPERFECT IN WHICH FRACTURES OCCUR EVEN BEFORE BIRTH.

11. • MUTANT GENES:
• AS IN BRACHYDACTYLY,ABNORMAL SHORTNESS OF FINGERS OR OSTEOGENESIS IMPERFECTA.
(FRATURES OCCURRING BEFORE BIRTH).
• ENVIRONMENTAL FACTORS
• TERATOGENS- ALCOHOL, THALIDOMIDE.

12. • COMBINATION OF GENETIC AND ENVIRONMENTAL FACTORS.
• VASCULAR DISRUPTION AND ISCHAEMIA.
• MECHANICAL FACTORS
• EFFECT OF OLIGOHYDRAMNIOS.

13. ANOMALIES
• BRACHYDACTYLY: SHORTNESS OF THE DIGITS AS A RESULT OF REDUCTION IN THE LENGTH
OF PHALANGES.
• THIS IS A DOMINANT TRAIT.
• ASSOCIATED WITH SHORTNESS OF STATURE.

14. • POLYDACTYLY: MORE THAN FIVE DIGITS IN HANDS AND FEET, ALSO CALLED AS
SUPERNUMERARY DIGITS.
• HANDS MOSTLY MEDIAL DIGITS ARE EXTRA.
• FEET MOSTLY LATERAL DIGITS ARE EXTRA.

16. • SYNDACTYLY: WEBBING OF DIGITS
• CUTANEOUS –APOPTOSIS
• OSSEOUS: MOSTLY BETWEEN 3RD
AND 4RTH FINGERS.

17. • CONGENITAL CLUB FEET: ALSO CALLED TALIPES EQUINOVARUS
• OCCURS IN 1 IN 1000 LIVE BIRTHS.
• IT IS THE MOST COMMON MUSCULOSKELETAL BIRTH DEFECT.
• SOLES OF FEET TURN MEDIALLY AND FEET ARE INVERTED.
• B/L IN 50% CASES.
• MORE COMMON IN MALES.
• MULTIFACTORIAL CAUSES: BOTH GENETIC AND ENVIRONMENTAL.

19. DEVELOPMENT OF DYSPLASIA OF THE HIP
• 1 IN 1500 LIVE BIRTHS
• MORE IN FEMALES
• UNDERDEVELOPED ACETABULUM
• DISLOCATION ALMOST ALWAYS AT BIRTH
• GENERALIZED JOINT LAXITY

20. CLEFT HAND AND FOOT
• CONSISTS OF A CLEFT BETWEEN 2ND
AND 4RTH METACARPAL BONES.
• 3RD
METACARPAL BONE IS ABSENT.
• THUMB,INDEX FINGER,4RTH AND 5TH
FINGERS ARE FUSED.
• CAUSE IS MUTATION IN PITX1 GENE.

21. MARFAN SYNDROME
• INDIVIDUALS ARE LONG THIN SLENDER.
• LONG THIN LIMBS.
• LONG THIN FACE.
• CAUSE IS MUTATION IN FIBRILLIN.