DEVELOPMENT OF OROFACIAL STRUCTURES AND ITS CLINICAL CORRELATIONS

DEVELOPMENT OF ORO-FACIAL STRUCTURES AND ITS CLINICAL CORRELATIONS The images on slides 9 and 10 are from Thomas A Marino Ph D. marino@astro. temple. edu while those of 16 and 17 are from a website. The owner of this website is hereby duly acknowledged. I also appreciate the contribution of Prof. Cary Engleberg for the images on slides 5 -8.

SLIDE 2: THE INTRODUCTION n The rationale n Methodology n The vision and mission of the Dental School, CHS, KNUST

SLIDE-3: THE LEARNING OUTCOMES n Describe and illustrate the pre-embryonic period of human development, which is weeks 1 -3 (refer slides 3 -5) n Describe and illustrate development of branchial arches, the face and palate n Enumerate various types of facial clefts with illustrations n Describe and illustrate development of the tongue n Describe and illustrate development of the mandible, its growth and the fate of Meckel’s cartilage n Describe and illustrate development of maxilla n Describe derivates and anomalies of branchial arches , clefts and pouches n Diagnose various types of facial clefts images n Self assessments and references

SLIDE 4: PRE-EMBRYONIC WEEK 1 1. Formation of zygote 2. The zygote undergoes series of division to form morula which differentiates into blastocyst

SLIDE 5: PRE-EMBRYONIC WEEK 1 - BLASTOCYST DIFFERENTIATION 1. Thus formed, blastocyst differentiates into embryoblast layer and trophoblast layer. 2. Trophoblats differentiate into syncytiotrophoblasts and cytotrophoblasts

SLIDE 6: PRE-EMBRYONIC WEEK 2 1. At 9 th day, blastocyst completely embedded into endometrial wall 2. At days 11 and 12, the syncytiotrophoblasts erode into endometrial blood vessels to establish uteroplacental circulation 3. By end of 2 nd week, secondary yolk sac is formed and amniotic cavity appears 4. Also, at this time, a bilaminar embryonic disc forms from inner cell mass

SLIDE 7: PRE-EMBRYONIC WEEK 3 1. Formation of trilaminar disc at week 3. 2. The 3 -layered disc named ectoderm, mesoderm and ectoderm. 3. Neural folds formed as a result of invagination of ectoderm (A and B). 4. Population of ectodermal cells adjacent to the folds gives rise to neural crest cells (C). 5. The crestal cells migrate widely (D) and failure of these cell to migrate to the face gives rise to Treacher Collins syndrome

SLIDE 8: THE BRACHIAL ARCHES, POUCHES AND CLEFTS 1. Identifiable elements of brachial apparatus at 5 th week 2. Arrangement of the three components of brachial apparatus 3. A number of adult structures derivable from the brachial apparatus (ref slides 16 and 17)

SLIDE 9: THE NERVES OF THE ARCHES 1. Mandibular div of trigeminal nerve 2. The facial nerve 3. Glossopharyngeal nerve 4. Vagus and accessory

SLIDE 10: DEVELOPMENT OF THE FACE AND PALATE 1. 2. 3. 4. 5. 6. Recognizable face starts from 5 primordia. Mandibular processes are the fist to merge. Formation of Meckel's and Reichert’s cartilages. Formation of nasal tip, columella, prolabium, fraenulum and primary palate from globular process. Fusion of maxillary process with medial fold of globular process. Development of secondary palate.

SLIDE 11: THE FACE AT 8 TH WEEK By the 8 th week, the face has acquired a more human appearance with the following feature in place: 1. Complete closure of lower facial fissures and grooves 2. Formation of primitive lower and upper jaws with complete fusion of max an mand processes 3. Better definition of upper lip and lower nasal regions 4. Formation of furrow at the nasal bridge

SLIDE 12: VARIOUS TYPES OF FACIAL CLEFTS

SLIDE 13: DEVELOPMENT OF THE TONGUE n Appearance of a median tongue bud in the floor of the pharynx at end of 4 th week n Formation of lateral tongue buds from the proliferation of ventromedial 1 st brachial arches n Formation of the anterior 2/3 of the tongue n Development of posterior 1/3 of the tongue n The general mucosal sensory innervations of anterior 2/3 n Innervations of the vallate papillae n Innervations of intrinsic and extrinsic muscles

SLIDE 14 -DEVELOPMENT AND GROWTH OF MANDIBLE AND THE FATE OF MECKEL'S CARTILAGE n Development of mandible preceded by meckel’s cartilage which appears in 6 th week n Appearance of mandible as a band of dense conn. Tissue which ossifies at 7 th week n Mapping of the ramus by condensation of fibrous tissue far away from the cartilage n Development of TMJ by mesenchyme between condyle and temporal bone n Growth of the mandible occurring by remodelling n Fate of Meckel's cartilage

SLIDE 15 -DEVELOPMENT AND GROWTH OF MAXILLA 1. Development of maxilla by intramembraneous ossification 2. Growth of maxilla

SLIDE 16 -DERIVATIVES AND ANOMALIES OF THE 1 ST ARCH, CLEFT AND POUCH 1. Derivatives of the mesoderm of the 1 st arch 2. Anomalies of the mesoderm of the 1 st arch 3. Derivatives of the ectoderm of the first brachial cleft 4. Anomalies of the ectoderm of the 1 st brachial cleft 5. Development and anomalies of the 1 st brachial pouch

SLIDE 17 -DERIVATIVES AND ANOMALIES OF THE 2 ND BRACHIAL ARCH, CLEFT AND POUCH 1. Derivatives of 2 nd arch (hyoid) 2. Anomalies of the 2 nd arch 3. Derivatives and anomalies of the 2 nd brachial cleft. 4. Derivatives and anomalies of the 2 nd brachial pouch

SLIDE 18: DIAGNOSIS OF VARIOUS TYPES OF ORO-FACIAL CLEFTS

SLIDE 19: SELF ASSESSMENT 1 n What is the name of the first pharyngeal arch? n What is the sensory and motor nerve supply of the first pharyngeal arch? n What is the expression of the second pharyngeal arch on the tongue? n When are the primary and secondary palates formed? n At what age in utero do simple jaw movements commence? n When does the modern TMJ develop?

SLIDE 20: SELF ASSESSMENT 2 7. How is zygote transported to the uterus? 8. Name the layers of newly formed blastocyst 9. What is the embryologic failure that gives rise to Treacher- Collins syndrome? 10. What is the site of ossification of maxilla and when does it appear?

SLIDE 21 -ANSWERS TO SELF ASSESSMENTS 1 AND 2 1. The Mandibular Arch 7. Ciliary action of the uterine tube 2. The Trigeminal Nerve 8. 3. The depression marking the site of the Thyro-glossal 'duct Embryoblast the inner layer that becomes future embryo and the outer layer, trophoblast 4. Primary palate at about 6 weeks, Secondary palate at 8 - 12 weeks 9. Failure of neural crest cells to migrate to the face 5. From about 6+ weeks. 10. 6. From about 16 weeks in utero, after secondary cartilage growth has carried the condylar region into relationship with the Temporal bone. The site of developing deciduous canine and it appears during the 8 th week in utero

SLIDE 22: TEXTBOOKS AND REFERENCES 1. 2. 3. 4. 5. 6. 7. 8. Berkovitz BKB, Hollland GR, Moxham BJ. A colour atlas and textbook of oral anatomy, histology and embryology 2 nd Ed 1992; Wolfe Publishing CO Ltd PP 231 -247 or the latest edition if available Ten-Cate AR. Oral histology, development, structure and function 5 th ed, 1998 CV Mosby Co or the latest 6 th Edition 2003 Avery JK Essentials of Oral Histology and Embryology A Clinical Approach 2 nd Ed, 2000 C V Mosby Co or the latest edition if available e. Medicine Head and Neck Embryology July 15 2002 Schoen JD, Edmonds JL Brachial anomalies 2003 Texas Paediatric Otolaryngology Center e. Medicine Face Embryology November 12 2003 Http: //www. emedicine. com/ent/topic 136. htm Grays textbook of anatomy-the latest edition if available