HISTOLOGY & EMBRYOLOGY Teaching PPT Dept. of Anat., Hist. & Embry. School of Medicine Xi’an Jiaotong University

1. HISTOLOGY & EMBRYOLOGY Teaching PPT Dept. of Anat., Hist. & Embry. School of Medicine Xi’an Jiaotong University

2. HUMANEMBRYOLOGY Development of Face, Neck & Limbs Tianbao Song (宋 天 保)

3. Chapter 3 Development of Face, Neck and Limbs 1. Branchial Apparatus (weeks 4-5) 1.1 Position:both lateral sides of head, dorsoventrally placed.

4. 1.2 Components • Branchial arches:6 paired mesenchyme bars • Branchial grooves: 5 ectoderm invaginations • Pharyngeal pouches: 5 pairs of outpocketings from pharyngeal endoderm • Branchial membranes: appositional grooves and pouches

5. 1.3 Development • 1st pairof branchial arches →face • 2nd, 3rd, 4th, 6th pairs→neck

6. 2nd arches grow caudally → overlap 3rd, 4th, 6th arches → fuse with epicardial ridge → neck • Clefts 2,3,4→ cervical sinus → disappear

7. 2. Development of Face (weeks 4-8) 2.1. Primordia: 5 prominences aroundstomodeum. • Singlefrontonasal prominence • Pairedmaxillaryprominences • Pairedmandibular prominences

8. 2.2. Development 1) Mandibular prominences→lower jaw and lip 2)Frontonasal prominence (upper part)→forehead

9. medial nasal prominence nasal pits lateral nasal prominence → nasal placode → 3)Frontonasal prominence (lower part)

11. crest & tip of nose 4) Medial nasal prominences fuse→middle fuse upper jaw & lip Maxillary prominence→ lateral cheek

12. 5) Lateral nasal prominence→alae, lateral wall of nose; fuse Maxillary prominence→nasolacrimal duct 6) Maxillary prominence + mandibular prominence → smaller oral fissure.

13. 7)Stomodeum→ oral cavity Nasal pits→nasal cavity

14. 3. Development of Palate (wks 5-12) • 3.1 Primordia • Median palatine process (1) • Lateral palatine processes( 2 )

16. 3.2 Process: lateral and median palatine processes fuse → palate.

17. 4. Derivatives of Pharyngeal Pouches 4.1 1st pouch 1) Lateral →tympanic cavity Medial →pharyngotympanic tube 2) Branchial membrane →tympanic membrane Branchial groove →external auditory meatus

18. 4.2 2nd pouch Medial →tonsillar fossa,surface epithelium ofpalatine tonsil;Lateral → degenerates 4.3 3rd pouch Dorsal part → inferior parathyroids Ventral part → thymus Both migrate caudally.

19. 4.4 4th pouch Dorsal →superior parathyroids Ventral → degenerates 4.5 5th pouch→ ultimobranchial body → (in thyroid) Neural crest cells→ parafollicular cells

20. 5. Development of Limbs (wks 4-8) 5.1 Limb buds Somatic lateral mesoderm → upper & lower limb buds (mesodermal core + ectodermal cap) → elongated & fragmented → 3 portions Wk 4

21. 5.2 Hand & foot plates Terminal portions of limb buds → hand & footplates→ digital raysindistal ends → fingers & toes (wk 8)(apoptosis of tissues in between) Wk 6

22. 5.3 Bones & muscles • Somatic mesoderm → cartilages → bones; (and connective tissue) • Somitic mesoderm → myoblasts → muscles

23. 5.4 Rotation (wk 7) • Upper limb rotates 90°laterally • Lower limb rotates 90°medially

24. 6. Congenital Malformations • 6.1Cleft lip • Division of upper lip, unilateral or bilateral; • Failure of maxillary prominence to fuse with medial nasal prominence on the same side.

25. 6.2 Oblique facial cleft • Division extending from the upper lip to medial margin of orbit; • Failure of maxillary prominence to fuse with lateral nasal prominence on the same side.

26. 6.3Cleft palate • Failure of lateral palatine process to fuse with each other or with median palatine process. • Unilateral or bilateral, complete or incomplete, with or without cleft lip.

27. 6.4 Cervical cyst and fistula • Failure of closure of cervical sinus(cyst), may connect to surface or pharynx(fistula); • Cyst on lateral side of neck along anterior border of sternocleidomastoid muscle.

28. 6.5 limb abnormalities • Amelia & meromelia (phocomelia) • Polydactyly • Sirenomelus & syndactyly

29. SUMMARY • Primordia and malformations of the face, palate and limbs; • Derivatives of pharyngeal pouches;