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GIT I 2010. Development of GIT Primitive gut – from oropharyngeal to cloacal membrane, connected with yolk sac by means of ductus omphaloentericus Development.

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Presentation on theme: "GIT I 2010. Development of GIT Primitive gut – from oropharyngeal to cloacal membrane, connected with yolk sac by means of ductus omphaloentericus Development."— Presentation transcript:

1 GIT I 2010

2 Development of GIT Primitive gut – from oropharyngeal to cloacal membrane, connected with yolk sac by means of ductus omphaloentericus Development from endoderm, ectoderm of stomodeum and proctodeum, and from splanchnopleura (visceral layerof mesoderm) Segmentation of endoderm – expressed Hox genes: Foregut – truncus coeliacus Midgut - a. mesenterica superior Hindgut – a. mesenterica inferior

3 Foregut Primitive pharynx and organs, which develop from it: aditory (eustachian) tube and tympanic cavity, tonsilla palatina, parathyroid glands, thymus) Respiratory system Oesophagus and stomach Duodenum Liver, gallbladder, bile ducts and pancreas

4 Development of face 4.week - reagion surrounding stomodeum – under control of induction from prosencephalic organisating centre – (mesoderm rostral to notochord) and rhombencephalic organisating centre (ventral to hindbrain) Derived from pharyngeal arches

5 Face Stomodeum and bucopharyngeal membrane Frontonasal prominence Nasal (olphactory) placodes Medial nasal processes Lateral nasal processes 1. pharyngeal arch Maxillary swellings (prominences) Mandibulary swellings (prominences)

6 Face Mandibular swellings fuse - mandible Medial nasal processes grow and fuse in midline (intermaxillary process), later they fuse with maxillary swellings – upper jaw – maxilla Lateral nasal processes are separated by nasolacrimal groove – during 6 th week they fuse with maxilla - nasolacrimal duct and sac.

7 Summary FNP forms forehead, tip and dorsum of the nose Lateral nasal processes – lateral part of the nose (alae) Medial nasal processes – intermaxillary segment - nasal septum, philtrum, premaxilla and primary palate Maxillary swellings – upper part of cheeks, upper lip, maxilla and secondary palate

8 Development of the nasal cavities Nasal placodes - nasal pits – primordium of nasal vesicles – in front of the brain Nasal vesicles are separated from oral cavity by nasal fin (keel) – after rupture of nasal vesicles – oral and nasal cavities fuse – primitive choana – dorsally from primary palate

9 Development of palate Primary palate – intermaxillary process (6.week) - medial nasal processes Secondary palate - laterally – palatine shelves – paralel to the tongue – in medio-caudal direction Growth of mandible moves tongue down – palatine shelves rotate upward into a horizontal position and fuse with each other, with primary palate and nasal septum Finished during 12 th week

10 Malformations: Cleft lip and cleft palate: Disturbed proliferative activity in mesenchymal tissue – shelves fail to meet in midline and to fuse – multifactorial heredity, trisomia 13 Oblique facial clefts – nasolacrimal groove persistency Macrostomia, microstomia

11 Tongue development Floor of the primitive pharynx Distal lingual buds - lateral lingual swellings Tuberculum impar – medial lingual bud Median groove – lingual septum Copula (2 nd arch) Hypopharyngeal eminence (3rd + 4 th arches) Entrance into the larynx

12 Hypopharyngeal eminence expands and overlaps copula Lateral lingual swellling fuse - septum Border between dorsum and root – terminal sulcus – transverse groove Foramen coecum

13 Development of the tongue Muscles – occipital myotomes Motoric inervation – hypoglossal nerve Sensoric inervation – trigeminus, glossopharyngeal and vagus nerves Taste buds - VII, IX. nerves (Thyroid gland - thyroglossal ducts – foramen caecum)

14 Tongue - structure Intrinsic muscles: skeletel muscle (3 directions) covered by mucosa Lingual septum and fascia – dense collagen connective tissue Surface of dorsum and apex – papillae Root of tongue - lingual tonsilla Lower part – submucosa, dorsal - mucosa fused with fascia

15 Extrinsic muscles of the tongue Genioglossal – symphysis of mandible- body of hyoid bone and tongue – forward Hyoglossal – major horns of hyoid bone - tongue - down Styloglossal -processus styloideus – tongue – upward and backward Palatoglossal – soft palate

16 Development of teeth Maxilla and mandible – labiogingival groove – lip and jaw Oral ectoderm - epithelium – dental lamina – tooth buds Mesenchyme from neural crest Dental papilla Bud stage Cap stage Bell stage

17 Bud stage Dental papilla – 10 proliferative centres – decidual teeth Permanent teeth – deep in dental lamina – lingually from decidual teeth or in dorsal region Activin (FGF) and BMP4 (TGFβ)

18 Cap stage Tooth bud Epithelial cells proliferate and invaginate into mesenchyme - enamel knot Ectoderm – enamel organ – outer enamel epithelium, inner enamel epithelium, enamel (stellate) reticulum Mesenchyme – dental papilla

19 Bell stage Mesenchyme differentiates into odontoblasts – production of predentin-dentin Inner enamel epithelium – ameloblast – enamel Root of tooth – development is postponed - dental sac – cement and periodontal ligaments Epithelial root sheath – induces development of root Inner epithelial cells induce - development of cementoblasts

20 Eruption Growing root pushes crown – mucosa around differenciates into gingiva (bony socket and ligaments) Decidual teeth – from 6.month (medial lower incisivi ) till the end of 2 nd year Permanent teeth – rooth of decidual tooth id resorbed – teeth are replaced Permanent teeth from 6 th year till adult (1st molar)

21 Tooth Crown – enamel Neck Root – cement Dentin Dental pulp, root canal apical foramen

22 Enamel 96% anorganic compounds (crystals of hydroxyapatite) 1% organic - proteins (amelogenin and enamelin) Amelogenin controls mineralization (linear calcification); enamelin – protease – necessary for reassembly of enamel Enamel: rods and interrod region, produced by ameloblasts After eruption covered by the membrane of Nasmyth - cuticle

23 Ameloblast Columnar cell, narrow and toll - ectoderm Reversal orientation - mito and terminal web under nucleus, apical region - GER,GC, secretory granules – glycoproteins of enamel matrix Apical process – Tomes´ process - extends into enamel Enames is produced between cell and basal lamina

24 Dentin Similar to bone: organic – 20% - collagen I., glycosaminoglycans; hydroxyapatite (70%), water (10%) Predentin – nonmineralized After mineralization – dentin Mineralization front – demarcation of dentin and predentin Dentin stays well-established even after necrosis of odontoblasts

25 Odontoblast Neural crest cells – surround dental papilla Nuclei in basal part of cell, polarized cell GER, GC, secretory granules Apical process in dentinal tube – canaliculi dentis, extends to enamel Cells connected by intercellular junctiones

26 Pulp Loose collagen connective tissue Mesenchyme-like elements Vessels, nerves, lymphatics Bodies of odontoblasts

27 Auxilliary structures Cement – similar to woven bone (cementocytes in lacunae ), fibers of Sharpey – attachment of ligaments Periodontal ligaments (attachment of tooth, periost of alveolar bone): gingival, transeptal, apical, horizontal, oblique, crestal Alveolar bone – woven bone Gingiva: stratified squamous epithelium, epithelial tentacle of Gottlieb (BL), gingival sulcus Lamina propria fuses with periost

28 Teeth Decidual teethPermanent teeth Incisor – dens incisivum Caninus – dens caninus MolarPremolar MolarPremolar Molar

29 Malformations: Numerical abnormalities (supernumerary teeth, partial or total anodontia) Amelogenesis imperfecta – X linked – affected gene for amelogenin Autosomal dominant – affected enamelin Dentinogenesis imperfecta Discolored teeth - tetracyclines

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