Lung Developement Flashcards
Describe the pulmonary vasculature in adults
PVR=low resistance
needed for gas exchange
Bronchi
Proximal Large airways with cartilage
Bronchioles
Distal, smaller airways
NO CARTILAGE
Acini
- all respiratory structures below terminal bronchioles
- respiratory bronchioles
- alveolar ducts
- alveoli
Epithelial of lungs is derived from?
Foregut Endoderm
The connective tissue, smooth muscle, blood vessels of the lungs is derived from what layer in utero?
Splanchic Mesoderm
Developement of the lungs in utero is dependent on?
interaction between splanchic mesoderm and pulmonary endoderm
Describe the affinity of O2 of fetal hemoglobin relative to dadult hemoglobin
- Fetal hemoglobin has a higher affinity for oxygen than adult Hemoglobin
Stages of Lung Developement:
2 fundamental phases: time is variable
- Organogenesis: Week 4-16
- establish air-conducting system/organ
- Embryonic: Week 4-5
- Pseudoglandular: Week 5-17
- Differentation: Week 16+
- develop the respiratory surface area for breathing and cell differentiation for specific fxns.
- alveoli have not developed before canalicular
- Canalicular: 16-25
- Saccular: 24-40
- Alveolar: week 36-8 years after conception
Lung Developement: Embryonic Stage
- Week 4-5
- Features:
- 2 Lung buds:
- outpouching from the foregut endoderm into surrounding splanchic mesenchyme
- 2 Lung buds:
- Vascular:
- pulmonary circulation present by 5 weeks
- extra pulmonary artery then lobular arteries form
Differentiation of lung tissue during pseudoglandular stage:
- Takes place in a centrifugal direction (proximal out)
- epithelium of central conducting airways differentiate into ciliated cells and goblet cells
- After week 10: develop
- chest wall
- smooth muscle cells
- bronchial glands
- Peripheral sections-cuboidal epithelium for branching to continue
What blood vessels form during pseudo-glandular stage?
- Pre-acinar arteries and veins form by vasculogenesis
- use airway as template
- formed by week 17
Pseudoglandular Stage: Lung features
- Features:
- conducting airways develop
- Terminal bronchioles are formed
- goblet cells
- cilia cells
- extensive airway branching
- Terminal bronchioles are formed
- After week 10 central conducting airways develop:
- cartilage
- smooth muscle
- bronchial glands
- periphery-cuboidal epitheliulm to allow further development of bronchial tree
- Differentation of lung tissue takes place in centrifugal direction
- proximal to distal
- conducting airways develop
is a child born before the 16-17th week viable?
- all elements of the lung are developed except those involved in gas exchange (pseudoglandular stage)
- fetuses will not survive because there is no surfactant or alveoli for gas exchange
Lung Developement: Canalicular stage
- Features: week 17-27
-
Formation of the acinus
- form respiratory bronchioles and alveolar duts
- some alveoli form
- Type II pneuomocytes differentiate into Type I Pneuomocytes
- Type II begins producing surfactant @ week 26
- form respiratory bronchioles and alveolar duts
- Bronchi and Bronchiole lumens become larger
- interstitial tissue between each airspace thins
- Vascular:
- proliferation of capillaries
- intra-acinar arteries and veins form by angiogenesis
- proliferation of capillaries
- Respiration is possible at end of staage
- weigh 1,000g
- week 26-29 before enough surfactant is produced
Lung Developement: Saccular Stage
- Features: 28-36 weeks
- Blood-air barrier formed
- fusion of epithelial and endothelium basement membranes
- Alveoli continue to develop
- septation increases surface area
- type I and II pneumocytes develop and differentiate
- Vascular:
- alveolar duct arteries form
What is the paradoxical respiration
- thorax and abdomen move in opposite directions during respiration:
- thorax contract
- abdomen extend
Lung developement: Alveolar stage
- Week 36-8 y.o.
- Formation of squamous epithelium to prepare for gas exchange
- alveoli continue to develop until 8 years old
-
Vascular:
- alveolar arteries continue to form
Lungs at birth:
- Fluid is cleared through mouth and nose, pulmonary capillaries, pulmonary arteries, veins, and lymphatics
- After birth, mainly increase the number of respiratory bronchioles and alveoli
- not the size of alveoli
*
- not the size of alveoli
Tracheo-esophageal Fistula (TEF)
- Failure of the tracheoesophageal septum to form
- incidence: 1:3000 births
- Risk factors:
- genetic
- enviromental
- immunology
- 50% of infants with a esophageal atresia (EA) or TEF have another birth defect, especially cardiac abnormalities
Lung pathologies in neonates:
- TEF
- Pulmonary hypoplasia
- BPD
- Meconium aspiration
Bronchoplmonary Dysplasia (BPD)
- Chronic lung disease in infants who received respiratory support with mechanical ventilation and prolonged oxygenation.
- primary risk factor:
- premature birth
- other risk factors:
- male sex
- smoking
- drug use
- malnutrition
Meconium Aspiration Syndrome
- serious condition
- newborn breathes a mixture of meconium (First feces) and amniotic fluid into lungs during delivary
At what stage do you stop developing alveoli?
8 y.o.
How many lobes are in the right vs left lung?
Right lung: 3 Lobes
Left lung: 2 lobes
What has developed by the end of the pseudoglandular stage?
- Development of chest wall, mediastinum, diaphgram, pleural splaces descend during this stage
- by the end of this stage, all elements of the lungs are developed except those involved in gas exchange
Pulmonary Hypoplasia:
- aka congenital diaphragmatic hernia
- Occurs during pseudoglandular stage
- failure of the chest well/diaphgram to develop causes a herniation
- 1 in 2,500 newborns
- leads to morbidity and mortality
- caused by exposure to enviromental toxicants during week 3-4
