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Development of digestive and respiratory systems

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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 tubepharyngeal, foregut, midgut and hindgut. the derivatives of the diverticulalung 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 bronchi Make proper learning outcomes Allantois 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 embryobody folds The 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 Tube Notochord MIDGUT PHARYNX FOREGUT Amnion Brain Amniotic cavity HINDGUT stomach Pd Cloacal plate Bladder D Liver Oral plate Heart Cr. Ca. Lung bud Pericardial cavity Yolk sac V Median 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 tissue 2 2 1 3 T.S of oesophagus Splanchnic mesoderm Submucosal and muscular layers 3 3 Endoderm Epithelial 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
Pharynx Pharynx and oesophagus. The short rostral tip of the pharyngeal region form the pharynx The 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 in a short oesophagus resulting in hiatal diaphragmatic hernia pocketing of stomach between pleuro-peritoneal membranes Bronchial bud Cr. Ca. Oesophagus Schematic diagram of ventral view of gut tube showing development of pharynx and oesophagus

10 Morphogenesis Of The Foregut. The Monogastric Stomach: The Dog
B Dorsal mesogastrium/fold of peritoneum form body wall forms greater omentum Dorsal mesogastrium Oesophagus Oesophagus Ventral Mesogastrium/ Lesser omentum Caudal Cr. Ca. Cranial Duodenum Cystic diverticulum/ gallbladder Stomach Duodenum Pylorus Hepatic diverticulum/liver A Ventral mesogastrium Morphogenesis 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 carnivores The 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 sinus stomach Dorsal aorta Peritoneum (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
D Long 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. Ca Cr V Sequence of withdrawal of loop determines final position of the intestines. Cranial limb returns first and forms the small intestines Caudal limb follows and forms part of the small intestine and the large intestines (Small intestines) Amniotic cavity Foregut Midgut Amnion Chorion Pharynx Notochord (Large intestines) Brain Yolk sac Heart Herniated loop

14 Development 0f pancreas, liver and gall bladder
Dorsal pancreatic diverticulum Stomach Dorsal mesogastrium Oesophagus Duodenum Diaphragm Ventral pancreatic diverticulum Hepatic Diverticulum/ liver Ventral mesogastrium Diaphragm Blood vessels Cystic Diverticulum/gall bladder

15 Development Of The Respiratory Diverticulum
Foregut (A).The L-T groove forms on ventral floor, at level of 4th pharyngeal arch Tracheo-oesophageal groove Laryngo-tracheal Grove(L-T) B (B). L-T gives rise to larynx and trachea Pharynx Oesophagus Larynx D Cr Ca. Trachea V ( C ). Bifurcation of lung bud , forms about 14 bifurcations Pharynx Pharynx C Tracheo-oesophageal septum Cr. Trachea Ca. Bronchial bud Oesophagus A and B, lateral view C, ventral view

16 Endoderm Mesoderm C RIGHT
Ventral Views of branching of trachea into principal bronchi and lobar bronchi RIGHT LEFT Pharynx Trachea Principal bronchi Parietal pleura Pleural cavity Pleuroperitoneal canal Visceral pleura Cr. Ca. Endoderm Trachea Respiratory epithelium, glands of trachea,bronchi, larynx and lungs D Principal bronchi Parietal pleura Mesoderm Cartilage,muscle,blood vessels and connective tissues of trachea bronchi,larynx and lungs lobar bronchi Viscera pleura

17 Species differences in lobes of lungs
LEFT RIGHT (dorsal view) Cranial lobe Trachea Species differences in lobes of lungs Minor differences Right lung has four lobes in Most species cranial, middle,accessory and caudal lobes Left lung has three lobes cranial(2parts) and caudal lobes B Middle lobe Caudal lobe Accessory lobe Canine lungs Terminal bronchioles Mesoderm C Alveolar cells Cr. Ca. Terminal sac Terminal sac stage of lung development (stage 4&5)

18 Malformations DIGESTIVE SYSTEM Stenosis of gastrointestinal tract
Atresia aniimperforate ani; failure of anal membrane to break down Oesophageal stenosis RESPIRATORY SYSTEM Larygotracheal abnormalities Tracheal hypoplasia/stenosisabnormal narrowing of the trachea in part or entirely. Collapsed tracheatracheal lumen is partly occluded and the tracheal cartilages flattened. Tracheal atresia total lack of tracheal patency. Subglottic stenosismalformations of larynx Pulmonary abnormalities. Accessory lungs an extra lung bud in abnormal site e.g. neck, abdomen. Pulmonary hypolasiadecreased lung development Pulmonary agenesis/aplasiaabsence of lung, very rare. Congenital pulmonary cystspart of bronchial tree loses connection with main bronchusendodermal secretions form cysts. 3. Respiratory distress syndromedifficulties in neonatal breathing difficultiesinability of alveolar epithelial cells to form enough surfactants. 4 .Neonatal maladjustment syndromeexample immotile cilia syndromeabnormal structure

19 Summary Digestive system
The gut tube is formed by folding of the splanchnopleure Divisions 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.pp Carlson, B., “Patten’s Foundations of Embryology”. 6th. Edition. Mcgraw Hill. London.pp Noden, D.M., & de LaHunta, A., “The Embryology of Domestic Animals”. Pp

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