Embryology: Development of digestive system image556 Trávící systém II - 33 •· Embryo folding – incorporation of •endoderm to form primitive gut. •· Outside of embryo – yolk sac and •allantois. •· Vitelline duct Trávící systém II - 34 •Stomodeum (primitive mouth) ð the oral cavity + the salivary glands •Proctodeum ð primitive anal pit •Primitive gut ð whole digestive tube + accessory glands • •Proctodeum •Tracheo- •esophageal •septum Trávící systém III - 22 •pharynx •forgut •midgut •hindgut •The epithelium of gut and glandular cells of associated glands of the gastrointestinal tract develop from endoderm •The connective tissue, muscle tissue and mesothelium derive from splanchnic mesoderm •The enteric nervous system develops from neural crest • • • •Tissues in GIT •primitive gut • • foregut midgut hindgut • from above ductus to cloacal • pharyngeal omphalomesentericus membrane • membrane and yolk sack • st11oralm stage11cloacal •Pharyngeal membrane •Derivatives of • •foregut – pharynx, (+ respiratory diverticle), esophagus • stomach, cranial part of duodenum • (+ liver, gall bladder pancreas), •midgut – caudal part of duodenum, small intestine and • part of large intestine (cca 1/3 of colon transv.) • •hindgut – the rest of large intestine, rectum, upper part of • the anal canal Trávící systém II - 45 • •Rectum •Liver •bile duct •pancreas •Foregut •Midgut •Hindgut Oral cavity •primitive mouth pit – stomodeum •lined with ectoderm •surrounded by: - processus frontalis (single) - proc. maxillares (paired) - proc. mandibulares (paired) •pharyngeal membrane (it ruptures during the 4th week, primitive gut communicates with amniotic cavity) • File:Gray44.png 002f Pharyngeal (branchial) apparatus •Pharyngeal arches • appear in weeks 4 - 5 •on the ventral side of the pharyngeal gut; •each arch contains cartilage, nerve, aortic arch artery and muscle; •pharyngeal clefts and pouches are located between the arches; •membrana obturans parL5001 Pharyngeal arches Pharyngeal pouches Pharyngeal clefts - 4 weeks, PowerPoint Templates, Images, Diagrams, Slides • • • •ectoderm •endoderm •membrana •obturans Early+development+of+the+pharyngeal+grooves+and+pouches •Fate of pharyngeal pouches and clefts • early later •Sinus cervicalis •+ tympanic cavity • •Tympanic membrane •Structures derived from Arches • ARCH Nerve Muscles Skeletal Structures Ligaments 1 (maxillary/mandibular) trigeminal (V) malleus, incus ant lig of malleus, sphenomandibular ligament 2 (hyoid) facial (VII) stapes, styloid process, lesser cornu of hyoid, upper part of body of hyoid bone stylohyoid ligament 3 glossopharyngeal (IX) greater cornu of hyoid, lower part of body of hyoid bone 4 & 6 superior laryngeal and recurrent laryngeal branch of vagus (X) thyroid, cricoid, arytenoid, corniculate and cuneform cartilages •Structures derived from Pouches •Each pouch is lined with endoderm and generates specific structures. POUCH Overall Structure Specific Structures 1 tubotympanic recess tympanic membrane, tympanic cavity, mastoid antrum, auditory tube 2 intratonsillar cleft crypts of palatine tonsil, lymphatic nodules of palatine tonsil 3 inferior parathyroid gland, thymus 4 superior parathyroid gland, ultimobranchial body • • parL5001 •primitive pharynx •thyroid gl. • • • •laryngotracheal diverticle •(respiratory diverticle) 250px-Development •esophagus •Esophagus development •below respiratory diverticle, •behind larynx and trachea Esophagus development •differentiation of epithelium from endoderm •during the 8th week endoderm proliferates and temporarily closes esophageal lumen •other tissues and structures in the wall arise from splanchnic mesoderm 950 •mesoesophageum dorsale gives rise to dorsal mediastinum and mediastinal pleura •mesoesophageum ventrale disappears •esophagus •Mesenteries – suspensory duplicature derived from mesoderm and mesenchyme (a fold of tissue that attaches organs to the body wall) • •mesooesophageum •dorsal wall of body •Teratology • •Esophageal atresia – failure of recanalization or •septum deviation •Susp.: polyhydramnios, fetus cannot swallow • •Esophageal stenosis – narrow lumen, incomplete recanalization • •Tracheoesophageal fistula – defect in septum • • Trávící systém II - 36 •· in the 4th week – spindle dilatation of distal forgut in median plane •· endoderm – epithelium and glandular cells •· splanchnic mesoderm – other tissues of stomach wall • •Stomach development •90º Trávící systém II - 36 • • • • •Rotation around longitudinal axis: - left side → ventrally, - right side → dorsally. •Uneven growth of ventral and dorsal wall: - curvatura minor (to the right), - curvatura major (to the left). •Rotation around sagital axis : - curvatura minor (cranial position), - curvatura major (caudal position). Trávící systém II - 37 •Sagital rotation axis Trávící systém II - 40 •foregut midgut •duodenum •Teratology • •Pyloric stenosis – muscular hypertrophy, unknown •etiology • •Duodenal stenosis – incomplete recanalization • •Duodenal atresia – polyhydramnios • • vomiting • • •The derivatives -the distal duodenum, jejunum, and proximal ileum + -the distal ileum, cecum, appendix, ascending colon, and proximal 2/3 of transverse colon. • •the midgut grows faster than the embryo, creating: - duodenal loop - umbilical loop •Midgut Trávící systém II - 43 • • • • •Duodenal loop and umbilical loop •Umbilical loop herniates into the umbilical cord (physiologic herniation, in week 6-10) •Flexura •duodenojejunalis •forgut •midgut Duodenum development • • •Duodenal loop – 2 limbs: upper limb (from foregut) lower limb (from midgut) •Week 5 – 8, duodenum is temporarily obliterated •On top of loop – diverticles (for liver, gallbladder, pancreas) • • • Trávící systém III - 38 •The liver bud (hepatocystic diverticle) appears at the distal end of the foregut (week 4) and divides into hepatic and cystic diverticles, later ventral pancreatic bud and dorsal pancreatic bud (week 5). Both pancreatic buds meet and fuse (week 6). Trávící systém II - 40 •Liver, gall bladder, pancreas • • Septum transversum Trávící systém II - 41 Trávící systém II - 42 •liver Pancreas rotation cartoon •Due to rotation of stomach, mesenteries and umbilical loop, duodenal loop changes its position (from front to the right) and becomes retroperitoneal organ (together with pancreas) •Spleen •- derives from mass of cells in dorsal mesogastrium during week 5 • Intestines development •Umbilical loop – 2 limbs: cranial – jejunoileal limb (jejunum, major part of ileum) caudal – ileocecal limb (rest of ileum, caecum + appendix, colon ascendens and 2/3 of colon transversum) •A. mesenterica sup. – axis of rotation •week 6 – physiologic herniation into the umbilical cord, week 10 – reposition into abdominal cavity • L13I7 Trávící systém II - 44 loadBinaryCA3S4KPL • • • • • • • •90º • •180º •after 270º •rotation -In the umbilical cord, the midgut loop rotates 90° counter-clockwise direction around the axis of the superior mesenteric artery. -Upon returning, the gut undergoes another 180° counter-clockwise rotation, placing the cecum and appendix near the right lobe of the liver. -The total rotation of the gut is 270°. • •The distal end of the hindgut – the cloaca. •Derivatives of the hindgut: the distal 1/3 of the transverse colon, descending colon, sigmoid colon, rectum and upper part of anal canal (above the pectinate line). •Hindgut L13I9 •Division of the cloaca - urorectal septum divides the cloaca into a ventral urogenital sinus and a dorsal anorectal canal. • •The cloacal membrane breaks down during the 7th week. •Distal to the pectinate line (site of the former cloacal membrane), the epithelium of the anal canal derives from ectoderm of proctodeum (primitive anal pit) • Mesenteries •double layer of peritoneum enclosing organs and connecting them to the body wall image985 •Ventral mesentery exists only in region of distal part of esophagus, stomach (lesser omentum) and upper part of duodenum •Dorsal mesentery forms dorsal meso- gastrium (greater omentum), dorsal mesoduodenum, mesentery proper (jejunum, ileum) • •Thank you for your attention the_end__by_m0thyyku