Pulmonology Flashcards
What is the respiratory tract derived from?
Endoderm
Lung forms from ventral bud of the esophagus–> foregut
Branching dependent on the underlying mesodermal mesenchyme
Describe the vascular supply of the pulmonary system
Pulmonary vasculature forms from branches off the 6th aortic arch- supply intrapulmonary structures, regulate gas exchange
Bronchial arterial system comes off the aorta- supplies conducting airways, visceral pleura, connective tissue, pulmonary arteries
Pre-acinar arteries: adjacent to airways up to and including nonrespiratory bronchioles
develop by angiogenesis (formation of new vessels from pre-existing ones), growth corresponds with airway development, complete by ~16 weeks
Intra-acinar arteries: adjacent to respiratory bronchioles and alveolar ducts, develop by vasculogenesis (de novo vessel formation from mesoderm), growth corresponds with alveolar development, birth to 8-10 years
Aveolarization is enhanced by:
VITAMIN A
THYROXINE
Alveolarization delayed by:
Postnatal steroids
supplemental oxygen
nutritional deficienies
mechanical ventilation
insulin
inflammation
Name the developmental stages of the lung and GA of development
- Embronic ~5 weeks
- Pseudoglandular ~15 weeks
- Cannalicular ~25 weeks
- Saccular ~35 weeks
- Alveolar ~36+ weeks
Every Preemie Can Suck Air
Name major developments in each pulmonary developmental stage
Embryonic: lung forms from ventral bud of esophagus, pulmonary vascular development from 6th aortic arch
Pseudoglandular: all large airway bronchi up to terminal bronchi established, begin to produce amniotic fluid, pneumocyte precursors, separation of thorax and peritoneal cavity (7 weeks)
Canalicular: branch out to terminal bronchioles,
type II pneumocytes begin to differentiate to type I, lung is viable! (adult # of airways completed by 24 weeks)
Saccular: sacs form from the terminal bronchioles, last generation of air spaces completed, gas exchange via alveolar-capillary membranes
Aveolar: alveoli form and increase in diameter, microvascular growth and vessel maturation
Describe type I and type II pneumocytes
Type I:
- fried-egg with tight junctions
- 90% of surface
- gas exchange
- derived from type II cells
Type II:
- cuboidal shape
- 10% of surface
- surfactant metabolism and secretion
- progenitor to type I cells
Fetal lung fluid maintained airway volume similar to _____
funtional residual capacity (20-30ml/kg)
near term FLF production rate is low (4-5ml/kg/hr)
Describe fetal lung fluid production during gestation
epithelial cell has ACTIVE chloride secretion into future air spaces–> osmotic gradient–> flow of liquid into fetal lung
Fetal lung fluid production inhibited by epinephrine (naturally increased with stress of delivery) and beta-adrenergic agonists
Describe how fetal lung fluid is absorbed (3 stages)
PRENATAL (35%):
- decreased formation and secretion of FLF
- ENaC absorbs sodium –> fluid to interstitium
- Increased lymphatic oncotic pressure, low fetal alveolar protein–> fluid to pulmonary lymphatics
ACTIVE LABOR (30%):
- vaginal squeeze
- catecholaline surge–> increasing transepithelial Na+ transport
- Higher cortisol and thyroid hormone concentrations–> increased transepithelial Na+ transport
POSTNATAL (35%):
- lung distention leading to increas in transpulmonary presures–> fluid to interstitium
- increased lymphatic oncotic pressure and low fetal alveolar protein –> fluid to pulmonary lymphatics
Most physiologically active component of surfactant
DPPC: dipalmitoyl phosphatidylcholine
50%
Which surfactant proteins are hydrophilic?
A and D
Which surfactant proteins are induced by steroids?
A, B and C
Which surfactant proteins are hydrophobic?
B and C
Which surfactant proteins are critical for surfactant function?
B and C
Which surfacant protein originates from chromosome 10?
A and D
Which surfactant protein originates from ch 8?
C
Which surfactant protein originates from ch 2?
B
Which surfactant proteins participate in host defense?
A and D
What is the function of surfactant protein A?
- Tubulin myelin formation
- host defense
What is the function of surfatant protein B?
- CRITICAL FOR SURFACTANT FUNCTION
- tubular myelin formation
- surface adsorption of phospholipds
severe respriatory failure soon after birth, surfactant administration i
What is the function of surfactant protein C?
- CRITICAL FOR SURFACTANT FUNCTION
- promotes surface adsorption of phospholipids
What is the function of surfactant protein D?
- host defense
- anti-oxidant
- surfactant lipid homeostasis
What is the most common known genetic cause of surfactant deficiency?
ABCA3 deficiency
Autosomal recessive
lack DPPC and PG, decrease laminar bodies
Clinically looks similar to protein B deficiency