Presentation on theme: "Development of digestive and respiratory systems"— Presentation transcript:
1 Development of digestive and respiratory systems M.A.Kai-Kai.I am least happy about this lecture. There seems to be far too much detail on the stomach and intestinal regions at the expense of respiratory, liver and pancreas
2 Learning Objectives UNDERSTANDING: development of the gut tube from the splanchnopleure.the diverticula of the gut tubepharyngeal, foregut, midgut and hindgut.the derivatives of the diverticulalung buds, thymus, gastrointestinal tract, liver and pancreas.morphogenesis of the stomach and intestines by--rotations and positional shifts that result in the definitive positions of the GI-tract.Morphogenesis of the respiratory system the laryngotracheal groove, the lung bud, the laryngotracheal tube, branching of the bronchiMake proper learning outcomesAllantois as a diverticulum?Surely not species differences in the pancreatic ducts!!
3 Formation Of The Gut Tube(1) Folding of somatopleure and splanchnopleure of a flat 12 day dog embryobody foldsThe cranial,caudal and lateral flexures/body folds.Rapid growth of the cranial end results in enlarged head process.Lateral body folds grow downwards and ventrally towards midline.Not clear to me that this diagram is showing what you want it to show. No sign of folds or enclosure of endoderm. I have covered the basic body folding (caudal, rostral, body sides ) in the membranogenesis lecture. We should stick to the same diagrams
4 Formation Of The Gut Tube(2) Body folds(BF) consists of inner splanchopleure and outer somatopleure. BF meet in ventral midline forming inner endodermal gut tube opened at the umbilicus(pig)I don’t find this very helpful - especially ‘umbilicus forming ‘ when the aperture is so open. The dorsal view tells us nothing
5 The Intestinal Portal Tube Dorsal view not useful
6 Median section through 18 days gestation of pig Differentiation Of Gut TubeNotochordMIDGUTPHARYNXFOREGUTAmnionBrainAmniotic cavityHINDGUTstomachPdCloacal plateBladderDLiverOral plateHeartCr.Ca.Lung budPericardialcavityYolk sacVMedian section through 18 days gestation of pig
7 Derivatives Of The Gut tube/Oesophagus Gut tube consists of three layers.--inner epithelium(1) derived from endoderm forms the different functional cells of the mucosa of the GI-tract.--the hepatocytes of the liver and secretory cells of pancreas.--the middle layer(2) of mesoderm forms the stroma, supporting cells and the striated and smooth muscle.--the outer layer(3) is mesoderm and visceral peritoneum forms the outer connective tissue2213T.S of oesophagusSplanchnic mesodermSubmucosal and muscular layers33EndodermEpithelial surface
8 Morphogenesis Of The Gut tube Development of the gut involves processes of:Elongation by rapid differential mitosis and enlargement.,Herniation of part of the gut into the umbilical stalk.Rotation of several local regions of the gut.Histogenesis and functional maturation.
9 Pharyngeal and Foregut region PharynxPharynx and oesophagus.The short rostral tip of the pharyngeal region form the pharynxThe caudal part of pharyngeal region and rostral foregut forms the oesophagus.Oesophagus elongates to match growth of cervical,and thoracic and abdominal regions.Failure to maintain growth rate results ina short oesophagus resulting in hiatal diaphragmatic hernia pocketing of stomach between pleuro-peritoneal membranesBronchialbudCr.Ca.OesophagusSchematic diagram of ventral viewof gut tube showing developmentof pharynx and oesophagus
10 Morphogenesis Of The Foregut. The Monogastric Stomach: The Dog BDorsal mesogastrium/fold of peritoneum formbody wallforms greater omentumDorsal mesogastriumOesophagusOesophagusVentralMesogastrium/Lesser omentumCaudalCr.Ca.CranialDuodenumCystic diverticulum/gallbladderStomachDuodenumPylorusHepatic diverticulum/liverAVentral mesogastriumMorphogenesis Of The Foregut. The Monogastric Stomach: The Dog(i) A. Lateral view of the gut tube. The embryonic stomach is suspended dorsally and ventrally by the dorsal and ventral mesogastrium, a derivative of the splanchnopleure.(ii).The stomach rotates(180o) twice, 90o each in counterclock direction(iii) B. At end of rotation stomach lies transverse in the abdomen.With differential growth stomach forms large fundus and narrow pylorus.Stenotic pylorus common in dogs.(iv). Dorsal mesogastrium grows caudally, forms 2-layered sac, the greater omentum and omental bursa.Ventral mesogastrium forms the lesser omentum and connects the liver to the lesser curvature.
11 Morphogenesis Of The Foregut-hindgut Derivatives and development of the intestines in carnivoresThe distal foregut-->develops into cranial duodenum, liver, and pancreas.The midgut--> caudal duodenum, jejunum. ileum, caecum, colon (ascending).The hindgut-->colon (transverse, descending), cloaca.The cloaca--> rectum, bladder, urogenital sinusstomachDorsal aortaPeritoneum(contains allantoic connection)
12 Morphogenesis Of The Foregut-hindgut Mitosis and growth of foregut forms the intestinal loop.Gut tube is suspended by dorsal mesentery through which passes the cranial mesenteric artery(CMA).CMA acts as axis for looping of the intestines.Caudal limb develops a diverticulum,the caecum.Hindgut forms distal colon,rectum and cloaca.Intestinal loop enlongates, and rotates twice(360o) clockwise around cranial mesenteric artery.Morphogenesis Of The Foregut-hindgut
13 Morphogenesis Of The Intestinal Loop DLong intestinal loop herniates into the coelomic cavity of the umbilical cord.Abdominal cavity expands to accommodate the intestine the midgut returns to the body cavity.CaCrVSequence of withdrawal of loopdetermines final position of the intestines.Cranial limb returns first and forms thesmall intestinesCaudal limb follows and forms part of the small intestine and the large intestines(Small intestines)Amniotic cavityForegutMidgutAmnionChorionPharynxNotochord(Large intestines)BrainYolk sacHeartHerniated loop
14 Development 0f pancreas, liver and gall bladder Dorsal pancreaticdiverticulumStomachDorsalmesogastriumOesophagusDuodenumDiaphragmVentral pancreaticdiverticulumHepaticDiverticulum/liverVentralmesogastriumDiaphragmBlood vesselsCysticDiverticulum/gall bladder
15 Development Of The Respiratory Diverticulum Foregut(A).The L-T groove forms on ventral floor, at level of 4th pharyngeal archTracheo-oesophagealgrooveLaryngo-trachealGrove(L-T)B(B). L-T gives rise to larynx and tracheaPharynxOesophagusLarynxDCrCa.TracheaV( C ).Bifurcation of lung bud , forms about 14 bifurcationsPharynxPharynxCTracheo-oesophagealseptumCr.TracheaCa.BronchialbudOesophagusA and B, lateral viewC, ventral view
16 Endoderm Mesoderm C RIGHT Ventral Views of branching of trachea into principal bronchi and lobar bronchiRIGHTLEFTPharynxTracheaPrincipalbronchiParietal pleuraPleural cavityPleuroperitonealcanalVisceralpleuraCr.Ca.EndodermTracheaRespiratory epithelium,glands of trachea,bronchi,larynx and lungsDPrincipalbronchiParietalpleuraMesodermCartilage,muscle,bloodvessels and connective tissues of tracheabronchi,larynx and lungslobarbronchiViscerapleura
17 Species differences in lobes of lungs LEFTRIGHT(dorsal view)Cranial lobeTracheaSpecies differences in lobes of lungsMinor differencesRight lung has four lobes inMost speciescranial, middle,accessoryand caudal lobesLeft lung has three lobescranial(2parts) and caudal lobesBMiddle lobeCaudal lobeAccessory lobeCanine lungsTerminalbronchiolesMesodermCAlveolar cellsCr.Ca.Terminal sacTerminal sac stage of lung development (stage 4&5)
18 Malformations DIGESTIVE SYSTEM Stenosis of gastrointestinal tract Atresia aniimperforate ani; failure of anal membrane to break downOesophageal stenosisRESPIRATORY SYSTEMLarygotracheal abnormalitiesTracheal hypoplasia/stenosisabnormal narrowing of the trachea in part or entirely.Collapsed tracheatracheal lumen is partly occluded and the tracheal cartilages flattened.Tracheal atresia total lack of tracheal patency.Subglottic stenosismalformations of larynxPulmonary abnormalities.Accessory lungs an extra lung bud in abnormal site e.g. neck, abdomen.Pulmonary hypolasiadecreased lung developmentPulmonary agenesis/aplasiaabsence of lung, very rare.Congenital pulmonary cystspart of bronchial tree loses connection with main bronchusendodermal secretions form cysts.3. Respiratory distress syndromedifficulties in neonatal breathing difficultiesinability of alveolar epithelial cells to form enough surfactants.4 .Neonatal maladjustment syndromeexample immotile cilia syndromeabnormal structure
19 Summary Digestive system The gut tube is formed by folding of the splanchnopleureDivisions of gut tube into pharyngeal, foregut, midgut and hindgut regions.Each part of gut tube forms specific parts of the gastrointestinal tract, digestive glands and non-digestive organs.Morphogenesis of the stomach involves;--displacement of the stomach--differential growth and enlargement--reorientation.Development of the intestines involves elongation, herniation and rotation.Respiratory system.The pharyngeal and rostral foregut form the laryngo-trachral groove ventrally.The larynx develops cranially.The Trachael groove bifurcates into two tracheo-oesophageal grooves one on either side.The tracheal part develops into the respiratory tree by successive branching. Trachea bifurcates into 2 principal bronchi, then lobar and secondary bronchi. The branching form at different levels of bronchi down to alveolar sacs.
20 References.Gilbert, S., “Developmental Biology”. 7th Edition. Sinauer. Sunderland, Masachusetts.ppCarlson, B., “Patten’s Foundations of Embryology”. 6th. Edition. Mcgraw Hill. London.ppNoden, D.M., & de LaHunta, A., “The Embryology of Domestic Animals”. Pp