Embryo-Respiratory System

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  1. Respiratory System
    • Endoderm
    • Primitive pharynx-6th arch
    • Laryngotracheal groove-transcient and invaginates to form the laryngotracheal diverticulum-forms the respiratory bud
    • Tracheoesophageal folds-migrate towards midline to form tracheoesophageal septum (trachea and esophagus as own tube now)
    • Larngotracheal tube
  2. Trachea
    • Endoderm
    • -epithelium (lining of trachea) and glands
    • -lungs
    • Spanchnic mesenchyme
    • -cartilage
    • -connective tissue-B.V. and lymph
    • -muscles (smooth)
  3. Foregut
    • Esophagus
    • -endoderm
  4. Abnormalities in foregut
    • esophageal atresia-tracheoesophageal folds migrating towards midline and something goes wrong
    • liquid/food into lungs-connection of esophageus into trachea
    • can be seen on ultrasound and corrected with surgery
  5. Bronchi and Lungs
    • Endoderm
    • Lung bud
    • Bronchial buds
    • -Primary bronchus-left and right lung
    • -secondary bronchi-lobar-three on right (superior, middle, inferior); two on left: superior, inferior
    • -segmental bronchi-ten right, nine left
    • bronchialpulmonary segment-24 weeks, 17 orders of branches, terminal bronchioles
    • *Conduction system intact-way to get air into lungs
  6. Pseudoglandular (5-17 weeks) Lung Development
    • Connective tissue-mesoderm
    • -not close enough to sacs to have gas exchange
    • -can't survive
  7. Canalicular (16-24 weeks) Lung Development
    • Vascularization-mesoderm
    • respiratory bronchioles and terminal sacs (primitive alveoli)
    • +/- survival-depends: closer to 24 50% chance
  8. Terminal sac (24 weeks-birth) Lung Development
    • Differentiation of cells
    • gas exchange
    • squamous epithelium=type I pneumocytes-gas exchange flat-endoderm
    • lymphatic capillaries-mesoderm
    • secretory epithelial cells=type II pneumocytes-surfactant-protein that reduces surface tension and keep alveoli open so don't collapse down-endoderm
    • -will survive
  9. Alveolar (+8 years)
    • Alveolocapillary membrane-mesoderm (gas exhange and vascular capillaries touching) and endoderm (squamous epithelium
    • Primitive alveoli-form more primitive alveoli-endoderm-up to 3 years-some up to 8 years
    • -mature alveoli
  10. Formation of the Body Cavities: Coelom and Mesenteries
    • Pericardial cavity: heart
    • Pericardioperiotoneal canals: partitions form in each canal (lungs develop here)
    • -seperates pericardial cavity from the pleural cavities
    • -seperate pleural cavities from the peritoneal cavity (abdomine)
    • Pleural cavities: lung
    • Peritoneal cavity: abdomen
    • *pictures*
  11. Pericardial Cavity
    • 4th week
    • lateral folds
    • -endocardial primordia (heart inner lining start with 2 heart tubes)-mesoderm
    • -pericardial coelom-lateral to heart tubes
    • -somatic vs. splanchinic layers-mesentaries suspend heart and GI tract from wall-double layers of spanchnic mesoderm
    • Head folds
    • -heart-most cephalic (mesoderm)
    • -septum transversum-above heart-moves below after folding (mesoderm)
    • septum transversum
    • -become diaphragm
    • pericardioperitoneal canals-surround space for lungs/surround heart and septum transversum
  12. Pericardioperitoneal Canals
    • Two
    • Lies lateral to the proximal part of the foregut (esophagus) and dorsal to the septum transversum
    • one continuous tube
    • arbitrarily divide it into 3 regions
    • -region 1 and 3 become pleural cavities
  13. Pleuropericardial Folds
    • Due to growth of the bronchial buds into the pericardioperiotoneal canals (mesoderm)
    • Enlarge and form partitions that separate the pericardial cavity from the pleurla cavities
    • Formation of: pleural cavity, pericardial cavity(heart), primitive mediastimun (between lungs)
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Embryo-Respiratory System
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