10. Developmental Aspects of Lung Disease Flashcards
What are the 5 main stages of lung development?
- embryonic
- pseudo-glandular
- canalicular
- saccular
- alveolar
During lung morphogenesis what is the period in weeks for embryonic development?
3-8 weeks
sdevelopment?
5-17 weeks
During lung morphogenesis what is the period in weeks for pseudo-glandular development?
5-17 weeks
During lung morphogenesis what is the period in weeks for canalicular development?
16-26 weeks
During lung morphogenesis what is the period in weeks for saccular development?
24-38 weeks
During lung morphogenesis what is the period in weeks for alveolar development?
36 week- ~2-3 years
Is there overlap between lung morphogenesis stages?
Yes
Lungs develop as a branch from what structure?
from laryngo-tracheal groove
What other URT structures are formed from the laryngo-tracheal groove?
larynx and trachea
What 3 structures are formed in the mesoderm at embryonic stage of lung development?
- eosophagus
- primary bronchial tubule
- blood vessels
What type of organ is the bronchial tubule at embryonic stage?
liquid-secreting organ (which travels up to the mouth)
What makes up the primary bronchial tubule at the embryonic stage? (what’s inside it/its constituent)
amniotic fluid (fluid filled tubes)
How many branches are formed at the pseudo-glandular stage of lung development?
21 branches
Signs of which connective tissue type are found in the pseudo-glandular stage of lung development?
shows signs of cartilage
Are cells active or non-active looking in pseudo-glandular lung morphogenesis?
active looking cells (glandular)
What occurs at canalicular stage in terms of branches and blood vessels?
- more branches develop
- more blood vessels begin to form
What type of epithelium forms at canalicular stage of lung morphogenesis?
squamous epithelium (rather than cuboidal)
What is happening to the airway in canalicular stage of lung morphogenesis?
it’s becoming more sponge-like and thinner
What are the alveolar walls like in the alveolar stage of lung morphogenesis?
Very thin walls formed and air or fluid filled at this stage
What postnatal lung growth continues until teenage years?
alveolar septation (more alveoli made after gestation)
How many alveoli are there roughly at birth?
100-150 million
How many alveoli are there roughly at 3-8 years?
200-600 millon
At the end of which lung morphogenesis stage can life outside the uterus survive?
at the end of canalicular phase
What is the term used to describe the embryonic and pseudo-glandular phases of lung morphogenesis?
Organogenesis
What is the term used to describe the canalicular, saccular and alveolar phases of lung morphogenesis?
differentiation
At how many weeks does the embryonic period end in general?
at 8 weeks of gestation
At how many weeks does the foetal period start and end?
starts at 8 weeks and continues until the end of gestation
What are 3 main features of embryonic and pseudoglandular stage of lung morphogenesis?
- formation of major airways and accompanying blood vessels form (trachea +main bronchus in embryonic and bronchi and bronchioli in pseudoglandular)
- formation of bronchial tree and portions of respiratory parenchyma (functional part of the organ)
- birth of the acinus (region of lung supplied with air from one of the terminal bronchioles)
Appearance of lung buds and main pulmonary arteries, trachea and main bronchi.
What are 3 main features of canalicular stage of lung morphogenesis?
- last generations of the lung periphery formed and all conducting airways (repsiratory airways form; respiratory bronchioles and alveolar ducts)
- wall structure and epithelial cell differentiation
- air-blood barrier formed
What are the 3 main features of saccular stage of lung morphogenesis?
- expansion of air spaces as respiratory airways form
- surfactant detectable amniotic fluid/ is detected
- saccules and alveoli appear (300 million at birth)
What is the main feature of the alveolar stage of lung morphogenesis?
secondary septation
During which week of gestation does surfactant production start for stabilising the structures?
Approx. week 25 (and increases until week 40)
What is surfactant full of?
proteins and lipids
Which parts of the respiratory system are more likely to be affected by congenital problems in the early stages?
major airways
Which parts of the respiratory system are more likely to be affected by congenital problems in later stages?
Alveoli (numbers or restriction of air)
Alveoli mainly multiple during which time period after birth?
2-4 years
Does airway double in size after several years after birth?
yes, it doubles in size, 300-600 million alveoli form
At which lung morphogenesis stages does congenital lung disease occur?
at embryonic and pseudoglandular stages (early)
What are 3 examples of congenital lung disease at embryonic stage? (all affect large airways)
- tracheal, laryngeal stenosis
- pulmonary agenesis
- tracheo-oesophageal fistula
What does “stenosis mean”?
narrowing down
What does “agenesis” mean?
failure for organ to develop in embryo (non-appearance)
What does “fistula” mean?
permanent abnormal passageway between two organs in the body or between an organ and the exterior of the body
If embryonic stage has congenital problems affecting the major airways, what structures do congenital problems at pseudoglandular stage affect?
lungs themselves at this stage
What are 3 common congenital lung disease at pseudoglandular stage? (all affect lungs)
- pulmonary sequestration
- custadenomatoid malformation
- cyst formation
What is pulmonary sequestration?
- affects lower resp. tract
- consists of non-functioning mass of normal lung tissue that lacks normal communication with tracheobronchial tree
- receives its arterial blood supply from systemic circulation
What is cystadenomatoid malformation?
Malformation of the airways where lung lobes contain cysts rather than lung tissue
Cyst formation?
Cysts found in lungs and mainly contain air (sometimes fluid or solid mass)
How are cysts mainly detected in congenital lung disease?
Through CT scans or x ray which shows calcification of cyst
When are problems in diaphragm usually seen?
during early lung growth (variety of primitive tissue contributes to diaphragm)
When does diaphragm stop developing in a foetus?
~18 weeks
What does the term “hypoplasia” mean?
incomplete development or under development of an organ or tissue
What are 2 common diaphragmatic abnormalities?
- diaphragmatic hernia
- eventration
What 2 conditions associated with the lungs can diaphragmatic hernia lead to?
- pulmonary hypoplasia
- persistent pulmonary hypertension
What is eventration?
herniation of intestines (protrusion of abdominal contents through weakness or defect of the abdominal wall)
What main functional changes in the lungs occurs at birth? (2)
- changes function from fluid secretion to fluid absorption
- pulmonary vasodilation
Does gas exchange occur in the first few breaths?
No
What does the term “tachypnea” mean?
rapid breathing (tachy= fast, pnea=breathing)
What does transient tachypnea cause and why?
a “wet lung”; because there isn’t a rapid shift from fluid secretion to absorption
What is the role of surfactant?
Stabilises the alveoli and reduces their surface tension (since higher pressure exists in alveoli) as well as promotes gas exchange
What is surfactant made of?
phospholipids and lipophillic proteins (detergent)
What cells produce surfactant?
Type 2 pneumocytes (lamellar bodies)
What is a common neonatal surfactant deficiency called?
Hyaline Membrane Disease (RDS; respiratory distress syndrome is a consequence of it)
What are the treatment option for hyaline membrane disease (leading to RDS) (6)
- antenatal glucocorticoids
- surfactant replacement (stimulates mature cells within hours to produce necessary surfactant)
- oxygen
- CPAP
- Mechanical ventilation
- intubation
What is a common neonatal chronic lung disease?
BPD: bronchopulmonary dysplasia/CLDP
What do neonatal lung disease such as BPD (bronchopulmonary dysplasia) increase the risk of in the affected child? (3)
- increased risk of developing asthma
- increased severity bronchiolitis
- future COPD
What are the antenatal (before birth) origins of adult lung disease (COPD)? (4)
- in utero nicotine exposure
- nutrition
- low birth weight/ prematurity (antenatal steroids)
- micronutrients/ vitamins
What are post-natal (after birth) origins of adult lung disease (CODP)?
- infection (Barker hypothesis)
- growth
- ETS (+/- alpa1 AT deficiency)
- environmental pollution
- micronutrients/ vitamins (folic acid and vitamin D)
What do all cases of adult COPD have in common?
they are all influenced by gene-environment interactions
Do males or females have smaller airways?
males
What do antenatal steroids stimulate?
surfactant systems
What effect does nicotine have on the airways?
restricts the size of airway growth
What effect on lungs do antenatal and post-natal conditions have?
antenatal: impedes lung development
post-natal: stops lung maturing
At what age boundaries are humans at their peak lung function?
from 20-40 years
Is there a single factor which can cause lung disease?
- No; several genetic-environmmental factors needed for lung function decline.
- once several factors and genetic predispositions build up, a treshold is reached and lung disease develops
- smoking rapidly declines lung function but some people have a genetic predisposition too which creates a greater risk of developing cancer
Can it be possible to live long and smoke a lot?
Yes; but it’s extreme minority, most end up losing lung function and become seriously ill with lung disease.
Specific genetics are needed which the vast majority of population don’t have to not develop cancer from smoking (most people will).
COPD is what number on the leading cause of death table in the world?
3rd
What is the biggest factor leading to COPD?
heavy smoking
What 3 factors lead to remodelling of airway/lung parenchyma?
- antenatal programming
- gene interactions
- environmental exposures
Does low lung function that is tracked throughout life increase the risk of future COPD?
Yes