• Author / Uploaded
• Julienne Rowelie Aujero Sanchez

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EMBRYOLOGY OF RESPIRATORY SYSTEM January 19, 2016

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Dr. Dee Berto    

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The respiratory tract is derived from foregut mesoderm Lung buds from during 4th week Initially appear as the respiratory diverticulum, which is a ventral outgrowth of foregut endoderm MESODERM dependent process: retinoic acid triggers a release of TBX4 in the foregut endoderm which induces growth and differentiation of trachea and lungs SPLITTING OF FOREGUT AND RESPIRATORY DIVERTICULUM Trachea-esophageal ridges: longitudinal ridges that fuse to separate trachea from esophagus 1. Lung bud is open 2. Expands caudally 3. Ridges fuse 4. Divides foregut into trachea and esophagus

ESOPHAGUS     

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Pahaba ng pahaba Muscular coat is from splanchic Upper 2/3 striated- VAGUS Lower 1/3 smooth muscleSPLANCHIC PLEXUS **tracheoesophageal fistuladefect in mesoderm  Polyhydramnios  G.i problems  respiratory **blind pouch VATER- vertebral anomalies, anal atresia, tef, esophageal atresisa, renal atresia VACTERL- VATER+ Cardiac defects and Limb defects.

LARYNX   

Endoderm- epithelial lining Mesenchyme- cartilages and muscles 4th to 6th pharyngeal arches

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Recanalized at 10 weeks Cartilage also develops Ventricles of the larynx will form, has several folds forming the vocal cords. All laryngeal muscles innervated by VAGUS nerve 4th pharyngeal arch- superior laryngeal nerve 6th pharyngeal arch- recurrent laryngeal nerve (also supplies laryngeal nerve) **Laryngeal Atresia- congenital high airway obstruction syndrome (CHAOS) Air trapped in lungs, diaphragm flattened d/t expanding lungs

TRACHEA   

Endoderm Visceral splanchic mesoderm **tracheal atresia- no chance of survival

SEGMENTAL BRANCHING AND DEVELOPMENT OF BRANCHIAL TUBES 1. 2. 3. 4.

Trachea into 2 primary bronchi L and R divide into secondary bronchi 2 on left, 3 on right 7th week- 18 bronchopulmonary segments of the adult lung

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Endodermal/mesenchymal interactions important in producing bronchopulmonary segment Signaling molecules important for lung budding and branching morphogenesis Retinoic acid Fibroblast growth factor 10Fibroblast growth factor receptor 2 – stimulating epithelial growing Bone morphogenetoc protein (BMP4) signaling to stop elongating at the tip SHH- sonic hedgehog protein inhibit release of fibroblast growth facor 10

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Tip di na maggrow, yung sides na lang magcontinue maggrow kaya nagbbranch out sya  If branching is EARLY If branching is LATE CONGENITAL LUNG CYSTS- late. Formation of cyst

LUNGS 1. Pseudoglandular phase  5th-16th week  Development of lower conducting airways and vascular supply  Branching continues to form terminal bronchioles (15-25 branches)  Resembles exocrine gland  Epithelial differentiation- tall columnar epithelium  Respiration not possible**premature child 2. Canalicular phase 17th-24th week 1) Birth of acinus 2) Epithelial differentiationSimple Cuboidal Epithelium 3) Beginning of surfactant synthesis by Type II Pneumocytes  Child born 6 months poor prognosis 3. Terminal sac or saccular sac 24th to 37th  Initiation of alveolarization  Surfactant starts to appear  Surfactant-evens the surface tension  Type 2 pneumocyte produces surfactant  Small alveoli smaller tension=collapses  Big alveoli- surfactant  RDSrespiratory distress syndromehyaline membrane disease 4. Alveolar phase Continued development of alveolar proliferation

a. b. c. d. e. f.

Bronchi Bronchioles Terminal bronchioles A A A

GROWTH CAVITY     

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OF

LUNGS

IN

THE

BODY

Intraembryonic coelom Somatic mesodermparietal peritoneum Splanchic mesenchymevisceral peritoneum Dorsal mesentery hang like a sling Lung buds punch a hole in the visceral mesoderm causing it to invaginate developing the visceral pleura (lung covering) outer portionparietal pleura (lung covering) Lungs and heart still in one cavity, needs SEPARATION. a. 5 weeks- pleuropericardial folds grow from lateral towards the midline b. 6 weekspleuropericardial membrane reaches midline c. 7 weeks d. 8 weeks lungs grow and expand into pleural cavity Separating abdominal and thoracic cavities Septum transverumcentral tendon of diaphragm. It partially divides the 2 cavities Week 4 develops in transverse manner, front to back Thoracic 7 Thoracic 12 **partial separation ST continues on, it will stop when it reaches foregut. 2 openings: 1. Pericardioperitoneal canals Should be closed by pleuroperitoneal membrane which grows. Myoblast enter ST with nerve innervation at 5th week from ventral rami of C3-C5= PHRENIC NERVE

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Defects in PCP canals= congenital diaphragmatic hernia = lung will develop abnormally

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