Presentation on theme: "Development of digestive and respiratory systems M.A.Kai-Kai."— Presentation transcript:
Development of digestive and respiratory systems M.A.Kai-Kai.
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
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.
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)
Heart Pericardial cavity Oral plate Amnion Amniotic cavity Brain Notochord Yolk sac Liver FOREGUT MIDGUT HINDGUT PHARYNX Differentiation Of Gut Tube D V Ca. Cr. Pd Median section through 18 days gestation of pig Bladder Cloacal plate stomach Lung bud
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 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 --the outer layer(3) is mesoderm and visceral peritoneum forms the outer connective tissue 1 2 2 3 3 3 Splanchnic mesoderm Submucosal and muscular layers Endoderm Epithelial surface T.S of oesophagus
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.
Pharyngeal and Foregut region 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 Oesophagus Pharynx Schematic diagram of ventral view of gut tube showing development of pharynx and oesophagus Ca. Cr.
Morphogenesis Of The Foregut. The Monogastric Stomach: The Dog Dorsal mesogastrium Ventral mesogastrium Oesophagus Stomach Duodenum Cystic diverticulum/ gallbladder Hepatic diverticulum/liver A Pylorus Duodenum Ventral Mesogastrium/ Lesser omentum Dorsal mesogastrium/fold of peritoneum form body wall forms greater omentum D B The embryonic stomach is suspended dorsally and ventrally by the dorsal and ventral mesogastrium, a derivative of the splanchnopleure. (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(180 o ) twice, 90 o 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. 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. (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. Oesophagus Cranial Caudal Cr.Ca.
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 (contains allantoic connection) stomach Dorsal aorta Peritoneum
Morphogenesis Of The Foregut-hindgut and growth of foregut forms the Mitosis and growth of foregut forms the intestinal loop. is suspended by dorsal mesentery through which passes the artery(CMA). Gut tube is suspended by dorsal mesentery through which passes the cranial mesenteric artery(CMA). acts as for looping of the intestines. CMA acts as axis for looping of the intestines. limb develops a,the Caudal limb develops a diverticulum,the caecum. Hindgut forms distal colon,rectum and cloaca. Intestinal loop enlongates, and rotates twice(360 o) clockwise around cranial mesenteric artery.
Morphogenesis Of The Intestinal Loop 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 Cr Ca D V Chorion Notochord Brain Heart Amnion Amniotic cavity Midgut Foregut Pharynx Yolk sac Herniated loop (Small intestines) (Large intestines) 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.
A B C Development Of The Respiratory Diverticulum Laryngo-tracheal Grove(L-T) Tracheo-oesophageal groove Foregut Pharynx Larynx Oesophagus Trachea Pharynx Tracheo-oesophageal septum (A).The L-T groove forms on ventral floor, at level of 4 th pharyngeal arch A and B, lateral view C, ventral view (B). L-T gives rise to larynx and trachea ( C ). Bifurcation of lung bud, forms about 14 bifurcations D V Cr Ca. Cr. Ca. Bronchial bud Oesophagus Pharynx
RIGHT LEFT Pharynx Trachea Parietal pleura Pleural cavity Pleuroperitoneal canal Principal bronchi Visceral pleura Trachea Principal bronchi lobar bronchi Parietal pleura Viscera pleura C D Ventral Views of branching of trachea into principal bronchi and lobar bronchi Cr. Ca. Endoderm Respiratory epithelium, glands of trachea,bronchi, larynx and lungs Mesoderm Cartilage,muscle,blood vessels and connective tissues of trachea bronchi,larynx and lungs
LEFTRIGHT Trachea Cranial lobe Caudal lobe Accessory lobe Canine lungs Alveolar cells Mesoderm Terminal sac Terminal bronchioles Terminal sac stage of lung development (stage 4&5) B C Cr. Ca. Middle lobe 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 (dorsal view)
Malformations DIGESTIVE SYSTEM Stenosis of gastrointestinal tract Atresia ani imperforate ani; failure of anal membrane to break down Oesophageal stenosis RESPIRATORY SYSTEM 1. 1. 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 2. 2. 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
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.
References. 1. Gilbert, S., “Developmental Biology”. 7 th Edition. Sinauer. Sunderland, Masachusetts.pp511-512. 2. Carlson, B., “Patten’s Foundations of Embryology”. 6 th. Edition. Mcgraw Hill. London.pp547-557. 3. Noden, D.M., & de LaHunta, A., “The Embryology of Domestic Animals”. Pp292-305.