Presentation on theme: "Embryology of the Head, Face and Oral Cavity"— Presentation transcript:
1Embryology of the Head, Face and Oral Cavity Raj Gopalakrishnan B.D.S., Ph.D.Oral and Maxillofacial PathologyDept. of Diagnostic and Biological SciencesUniversity of Minnesota School of Dentistry
2Prenatal DevelopmentFigure from Ten Cate’s Oral Histology, Ed., Antonio Nanci, 6th edition
3Differentiation of the Morula into Blastocyst Figure from Ten Cate’s Oral Histology, Ed., Antonio Nanci, 6th edition
4Formation of Two-Layered Embryo (2nd week of gestation) Called bilaminar germ diskEctodermEndodermPre/prochordal plateFirm union between ectodermal andendodermal cells occur at prechordalplateFigures obtained from “Before We Were Born; Moore and Persaud, 6th edition, 2003”.
5Formation of Three-Layered Embryo: Gastrulation (3rd week) Triploblastic embryoFigure from Ten Cate’s Oral Histology, Ed., Antonio Nanci, 6th edition
6Formation of Three-Layered Embryo: Gastrulation (3rd week) Figures obtained from “Before We Were Born; Moore and Persaud, 6th edition, 2003”.
7First 3 weeks: Leads to formation of triploblastic embryo Next 3-4 weeks: differentiation of major tissues and organsincludes head and face and tissues responsiblefor teeth developmentdifferentiation of nervous tissue from ectodermdifferentiation of neural crest cells (ectoderm)differentiation of mesodermfolding of the embryo (2 planes-rostrocaudal and lateral)
8Formation of neural tube and neural groove Neural tube undergoes massive expansion to form the forebrain,midbrain and hindbrainFigures obtained from “Before We Were Born; Moore and Persaud, 6th edition, 2003”.
9Components of the mesoderm Along the trunk paraxial mesoderm breaks up into segmentedblocks called somitesEach somite has: sclerotome- 2 adjacent vertebrae and disksmyotome-muscledermatome-connective tissue of the skin over the somiteIn the head region the paraxial mesoderm only partially fragments to form a seriesof numbered somatomeres which contribute to head and neck musculatureIntermediate mesoderm: urogenital systemLateral plate mesoderm: connective tissue of muscle annd viscera; serousmembranes of the pleura; pericardium and peritoneum; blood and lymphatic cells;cardiovascular and lympahtic systems, spleen and adrenal cortex.Figure from Ten Cate’s Oral Histology, Ed., Antonio Nanci, 6th edition
10In the head, the neural tube undergoes massive expansion to form the forebrain, midbrain and hindbrainThe hindbrain segments into series of eight bulges calledrhombomeres which play an important role in development of the head
11Folding of the Embryo Head fold forms a primitive stomatodeum or oral cavity; leadingto ectoderm lining the stomatodeumand the stomatodeum separated fromthe gut by buccopharyngeal membraneOnset of folding is at 24 days andcontinues till the end of week 4Embryo just before folding (21 days)Figure from Ten Cate’s Oral Histology, Ed., Antonio Nanci, 6th edition
12Figure from Ten Cate’s Oral Histology, Ed., Antonio Nanci, 6th edition
13Neural Crest CellsGroup of cells separate from the neuroectoderm, migrate anddifferentiate extensively leading to formation of cranial sensoryganglia and most of the connective tissue of the headEmbryonic connective tissue elsewhere is derived form mesodermand is known as mesenchymeBut in the head it is known as ectomesenchyme because of itsorigin from neuroectodermLook up Fig 2-12 in text book for derivative of the germ layersand neural crest
14Avian neural crest cells Figure from Ten Cate’s Oral Histology, Ed., Antonio Nanci, 6th edition
15Head Formation (one of the first are the occipital somites) RhombomeresFigure from Ten Cate’s Oral Histology, Ed., Antonio Nanci, 6th edition
16Neural Crest Cell Migration Figure from Ten Cate’s Oral Histology, Ed., Antonio Nanci, 6th edition
17Pharyngeal arches expand by proliferation of neural crest cellsForebrain(prosencephalon)Midbrain(mesencephalon)r3Hindbrain(rhombencephalon)r5Couly et al., 2002
18Migration of cranial neural crest cells Anterior midbrainFNMETGPosterior midbrainETGMdAnterior hindbrainETGMdImai et al., 1996
19Clinical CorrelationTreacher Collins Syndrome is characterized by defects ofstructures that are derived form the 1st and 2nd branchial arches andis due to failure of neural crest cells to migrate properly to thefacial region
20Sagittal section through a 25-day embryo Buccopharyngeal membrane ruptures at 24 to 26 daysSagittal section through a 25-day embryoFigure from Ten Cate’s Oral Histology, Ed., Antonio Nanci, 6th edition
2226-day embryoFigure from Ten Cate’s Oral Histology, Ed., Antonio Nanci, 6th edition
23The pharyngeal apparatus groove/cleftpoucharchmembraneesophagusThe pharyngeal apparatus1234Branchial arches form in the pharyngeal wall (which has lateral plate mesoderm sandwichedbetween ectoderm and endoderm) as a result of lateral plate mesoderm proliferation andsubsequent migration by neural crest cellsThe Developing Human by Moore & Persaud
25Sagittal view of the branchial arches with corresponding grooves between each arch. Pharyngeal pouches are seen in the wall of the pharynx. The aortic arch vasculatureleads from the heart dorsally through the arches to the face
26Fate of the Pharyngeal Grooves and Pouches First groove and pouch: external auditory meatustympanic membranetympanic antrummastoid antrumpharyngotympanic or eustachian tube2nd, 3rd and 4th grooves are obliterated by overgrowth of the secondarch forming a cervical sinus – if persists forms the branchial fistulathat opens into the side of the neck extending form the tonsillar sinus2nd pouch is obliterated by development of palatine tonsil3rd pouch: dorsally forms inferior parathyroid glandventrally forms the thymus gland by fusing with thecounterpart from opposite side
274th pouch: dorsal gives rise to the superior parathyroid gland ventral gives rise to the ultimobranchial body (whichgives rise to the parafollicular cells of the thyroid gland)5th pouch in humans is incorporated with the 4th pouch
28(A) Tissue from arch II and V growing towards each other (arrows) to make branchial arches and grooves disappear(B) Resulting appearance following overgrowth(C) Contribution of each pharyngeal pouch
29Anatomy of the Branchial Arches Cartilage of 1st arch: Meckel’sCartilage of 2nd arch: Reichert’sOther arches not namedSome mesenchyme around cartilagegives rise to striated muscleEach arch also has an artery and nerveNerve: two components (motor andsensory)Sensory nerve divides into 2 branches:Posttrematic branch: covers the anteriorhalf of the arch epitheliumPrettrematic: covers the posterior halfof the arch epitheliumFigures obtained from “Before We Were Born; Moore and Persaud, 6th edition, 2003”.
30Meckel’s cartilage: Has a close relationship with the developing mandible BUT DOES NOT CONTRIBUTE TO ITIndicates the position of the future mandible. The mandible develops by intramembranous ossification. The malleus and the incus develop by endochondral ossification ofthe dorsal aspect of this cartilage. Innervation: V cranial nerveReichert’s: Dorsal end: stapes and styloid processVentral end: lesser horns of hyoid bone and superiorpart of the body of the hyoid boneInnervation: VII cranial nerveCartilage of the 3rd arch: inferior part of the body and greaterhorns of the hyoid boneCartilage of 4th and 6th arches: fuse to form the laryngeal cartilage
31Table obtained from “Before We Were Born; Moore and Persaud, 6th edition, 2003”.
32Aortic Vasculature Development At 4 weeks the anterior vessels have passed through each branchial arch tissueand have disappeared. The pouches project laterally between each arch.At 5 weeks the 3rd branchial arch vessel becomes the common carotid, whichsupplies the face by means of the internal carotid and stapedial arteries.Face, Neck and Brain are supplied by the common carotid through internal carotid.But by 7 weeks the circulation of face and neck shifts from the internal carotid toexternal carotid. The internal carotid continues to supply the brain.
33Details of the aortic arch changes during early development Details of the aortic arch changes during early development. Aortic arch vessels numbers1,2 and 5 disappear . Arch 3 becomes the common carotid artery. Arch 4 becomes thedorsal aorta and enlarges so that the common carotid arises from the aorta. Arch 6 becomesthe right and left pulmonary arteries
34Shift in the vascular supply to the face Face and brain are supplied first by the internal carotid arteryFacial vessels detach from the internal carotid and attach to theexternal carotid
35Muscle cells in the first arch become apparent during the 5th week and begin to spread withinthe mandibular arch into each muscle site’sorigin in the 6th and 7th week. These form themuscles of mastication – masseter, medialpterygoid, lateral pterygoid and temporalismuscle. They all relate to the developing mandibleBy 7 weeks the muscles of 2nd arch growupward to form the muscles of face.As these muscles grow and expand theyforms sheet over the face and forms themuscles of facial expression
36Masticatory muscles of the mandibular arch Facial muscles grow fromthe 2nd branchial arch to coverthe face, scalp and posteriorto the ear
38Cartilages derived from the branchial archesArch 1: Meckel’s cartilage and incusArch 2: Stapes, stylohyoid and lesserhyoidArch 3: Greater hyoidArch 4 and 6 thyroid andlaryngeal cartilage
39Anomalies of the head and neck Congenital auricular sinuses and cystsBranchial cystsBranchial sinusesBranchial fistulaBranchial vestiges(cartilaginous or bony remnants)DermatlasDermatlas
40Apparent fusion of facial processes by elimination of furrows True fusion of facial processes bybreakdown of surface epitheliumFigure from Ten Cate’s Oral Histology, Ed., Antonio Nanci, 6th edition
41Development of the Face The face develops between the 24th and 38th days of gestationOn 24th day, the 1st branchial arch divides into maxillary and mandibular archesFigures obtained from “Before We Were Born; Moore and Persaud, 6th edition, 2003”.
42Frontonasal processFigures obtained from “Before We Were Born; Moore and Persaud, 6th edition, 2003”.
43Figures obtained from “Before We Were Born; Moore and Persaud, 6th edition, 2003”.
44Figures obtained from “Before We Were Born; Moore and Persaud, 6th edition, 2003”.
45Formation of the LipsMiddle portion of the upper lip: Formed by the fusion of the medialnasal process of both sides along with the frontonasal processLateral portion of the upper lip: Fusion of the maxillary processesof each side and medial nasal processLower lip: Formed by the fusion of the two mandibular processesUnusual fusion between maxillary process and lateral nasal processleading to canalization and formation of the nasolacrimal duct
46Human embryo at 7 weeksFigure from Ten Cate’s Oral Histology, Ed., Antonio Nanci, 6th edition
48Pituitary Gland Development Ectodermal in origin and develops from 2 sources:An upgrowth from the ectodermal roof of the stomatodeumcalled hypophysial diverticulum (Rathke’s Pouch) - adenohypophysisA downgrowth from the neuroectoderm of the diencephaloncalled the neurohypophysial diverticulum – neurohypophysisDuring the 4th week of development, a hypophysial diverticulum(Rathke’s pouch) projects from the roof of the stomatodeum and liesadjacent to the floor (ventral wall) of the diencephalon. By the 5thweek, this pouch has elongated and has become constrictedat its attachment to the oral epithelium and is in contact with theinfundibulum (derived from the neurohypophysis)
49Figures obtained from “Before We Were Born; Moore and Persaud, 6th edition, 2003”.
50Figures obtained from “Before We Were Born; Moore and Persaud, 6th edition, 2003”.
51Derivation and Terminology of the Pituitary Gland Oral Ectoderm Adenohypophysis Pars distalis(hypophysial diverticulum (glandular portion) Pars tuberalisfrom roof of stomodeum) Pars intermediaNeuroectoderm Neurohypophysis Pars nervosa(neurohypophysial (nervous portion) Infundibular stemdiverticulum from Median eminencefloor of diencephalon)Clinical Significance: Craniopharyngiomas develop from remnantsof stalk of hypophysial diverticulum (in pharynx of sphenoid bone)
52Formation of the palate (weeks 7 to 9) Palate develops from the primary palate and the secondary palateThe primary palate develops at about 28 days of gestationPrimary palate develops from the frontonasal and medial nasalprocesses and eventually forms the premaxillary portion of the maxillaThe secondary palate develops between 7th and 8th week of gestationand completes in the 3rd monthThe critical period of palate development is from the end of 6th weektill the beginning of 9th week
53Formation of the secondary palate (starts between 7 to 8 weeks and completed around 3 months)Figure from Ten Cate’s Oral Histology, Ed., Antonio Nanci, 6th edition
54Figure from Ten Cate’s Oral Histology, Ed., Antonio Nanci, 6th edition
56Formation of the Tongue The tongue begins to develop at about 4 weeks. The oral part (anterior two-thirds) develops from two distal tongue buds (lateral lingual swellings) and a median tongue bud (tuberculum impar) [1st branchial arch]. Innervation: V nerve The pharyngeal part develops from the copula and the hypobranchial eminence [2nd, 3rd and 4th branchial arches]. Innervation: IX cranial nerve The line of fusion of the oral and pharyngeal parts of the tongue is roughly indicated in the adult by a V-shaped line called the terminal sulcus. At the apex of the terminal sulcus is the foramen cecum.Muscles of the tongue develop form the occipital somites and innervated by hypoglossal nerve
57Lingual swellingTuberculum imparFigures obtained from “Before We Were Born; Moore and Persaud, 6th edition, 2003”.
59The lingual papillae appear by the end of 8th week Vallate and foliate papillae appear first, fungiform andfiliform (10-11 weeks) papillae appear laterTaste buds develop during the 11 to 13 weeks by inductiveinteraction between epithelial cells of the tongue and invadinggustatory nerve cells from chorda tympani, glossopharyngealand vagus nerves
60Thyroid gland development (4 to 7 weeks) Figures obtained from “Before We Were Born; Moore and Persaud, 6th edition, 2003”.
63Development of Jaw Bones Figure from Ten Cate’s Oral Histology, Ed., Antonio Nanci, 6th edition
64Development of Mandible Figure from Ten Cate’s Oral Histology, Ed., Antonio Nanci, 6th edition
65Figure from Ten Cate’s Oral Histology, Ed., Antonio Nanci, 6th edition
66Figure from Ten Cate’s Oral Histology, Ed., Antonio Nanci, 6th edition
67Fate of Meckel’s Cartilage Posterior – malleus of the inner earSphenomandibular ligamentAnteriorly, may contribute to mandibleby endochondral ossification (some evidence)Rest are resorbed completely
68Secondary CartilagesThree secondary (growth) cartilages govern further growth ofmandible until birthCondylar cartilage (most important)Coronoid cartilageSymphysial cartilage
69Appears during 12th week and occupies most of the ramus and is quickly ossified byendochondral ossification, with a very thinlayer of cartilage present in the condylar head.This remnant persists until 2nd decade of lifeand is important for growth of mandibleAppears at 4 months anddisappears immediatelyFigure from Ten Cate’s Oral Histology, Ed., Antonio Nanci, 6th edition
70Development of Maxilla Develops from one center of ossification in maxillary process ofthe 1st branchial archCenter of ossification is angle between the divisions where theanterosuperior dental nerve is given off from inferior orbital nervefrom where it spreads posteriorly, anteriorly and superiorlyNo arch cartilage is present, so maxilla develops in closeassociation with the nasal cartilageOne secondary cartilage also contributes to maxilladevelopment: zygomatic cartilage