WK 11

• respiratory tract forms early in development, but not funcitonal until after birth
• Lateral folding of the embryo creates the primitive gut tube. foregut (oral cavity to duodenum)
• Primordial pharynx is the most cranial part of the foregut around which pharyngeal arches/pouches develop, Ends in stomodeum (early opening of future mouth) ~week 5
• Beginning of 4th week, neural crest cells migrate into head region. 4 prominent bulges + 1 non-visible = pharyngeal arches. Each contains an aortic arch artery.
• Pharyngeal arches

  1. maxilla CN V
  2. ear, m. facial expression, hyoid CN VII
  3. upper pharynx, hyoid CN IX
  4. /6. LARYNX, PALATE, LOWER PHARYNX, THYROID CN X
• TRANSITION TO INDEPENDENT BREATHING REQUIES:

  sufficient surfactant production. transformation from secretory to gas-exchanging capability. establishment of separate pulmonary/systemic circulation.
• fetal breathing movement required to:

  condition respiratory muscles + stimulate development with fluid pressure gradients
• Infant respiratory distress syndrome (IRDS): primarily disease of prematurity. 60% neonates ~28 weeks at birth. 10% ~34 weeks at birth. 5% near term (36+). Cause: lack of surfactant --> alveolar collapse --> respiratory insufficiency
• IRDS signs + symptoms: hypoxia, hypercapnia, acidosis, grunting, retraction, nasal flaring, cyanosis, diffuse 'ground glass' lungs on x-ray. treatment: maternal corticosteroids before birth to accelerate lung maturation, exogenous surfactant after birth.
• pharynx develops as cranial part of foregut
• intraembryonic coelom forms thoracic and abdominal cavities; septum transversum separates these and forms the diaphragm
• lungs bud out from pharynx in embryonic phase
• lung development has 5 phases: embryonic, pseudoglandular, canalicular, saccular, and alveolar
• alveolar-capillary barrier has 2 cell layers: alveolar epithelial and pulmonary capillary endothelium
• capillary endothelium: squamous cell, thin cytoplasmic extension that branch outward. tight junction connections. become leaky in pneumonia, acute respiratory distress syndrome from inflammatory factors.
• alveolar fibroblasts function as an interstitial brace. prevent overinflation of lungs. also do repairs.
• type 1 epithelial cells: less numerous, more volumous. thin cytoplasmic extensions, spread over basement membrane around the capillary meshwork. Thin sheets wrap around pulmonary capillary.
• type 1 cannot undergo mitosis, therefore must be replaced. type 2 pneumocyetes can. type 1 cells connect via tight junctions. type 2 more numerous. type 2 = cuboidal, secrete surfactant, facilitate transepithelial transport of solute to keep the alveoli dry, and proliferate into type 1 cells
• lamellar bodies are where surfactant resides. they're extruded onto the surface of the alveoli to reduce tension and prevent lung collapse
• the left lung has an inferior thinning known as the lingula (for the heart)
• the oblique fissure separates the superior and inferior lobe of the left lung
• the bronchial arteries are branches of the thoracic aorta
• the left lung has 2 lobes
• the right lung has 3 lobes
• sibson's fascia covers the apex of the lung
• Function

  ·         Bronchial arteries bring blood to the lungs for NUTRIENT supply

  ·         Pulmonary arteries bring blood to the lungs for GAS EXCHANGE

  Blood Type

  ·         Bronchial arteries bring oxygenated blood

  ·         Pulmonary arteries bring deoxygenated blood 
• heparin is a direct activator of antithrombin 3
• apixaban is a factor Xa inhibitor
• dabigatran is a fibrinogen conversion to fibrin inhibitor
• 2,7,9,10 are activated by gamma carboxylation via vitamin k
• hirudin is a naturally occuring peptide from leeches, which is a thrombin inhibitor
• cor pulmonale = RV hypertrophe/dilation 2ndary to pulmonary hypertension
• warfarin mean halflife = 40 hours. 92% urine elimination
• von willebrands disease is most common clotting disorder. autosomal dominant.
• Pt evaluates extrinsic pathway
• TT measures conversion of fibrinogen to fibrin. focuses on common pathway
• aPTT measures intrinsic pathway