Developmental aspects of lung disease

Question 1

What are the 5 stages of structural lung developments and when do they occur?

Answer 1

Embryonic 3-8 weeks
Pseudoglandular 5-17
Canalicular 16-26
Saccular 24-38
Alveolar 36- 2/3 years

Weeks are subject to opinion etc

Question 2

What happens in embryonic stage?

Answer 2

The lung (derived from the yolk sac) buds off from the foetal foregut, and divides from the oesophagus. Develops as a respiratory diverticulum. At week 5 - 2 primary lung buds visible, going onto divide into lobar buds (2 left and 3 right).

Weeks 3-8

Question 3

What is the lung derived from?

Answer 3

Endoderm - yolk sac

Question 4

What are the blood vessels and connective tissue surrounding the lungs derived from?

Answer 4

mesoderm

Question 5

What happens at pseudoglandular phase?

Answer 5

The lobar buds further divide and branch into (eventually 16-25) primitive lobar segments.

Development of specialised cells eg cilia & mucus glands.

Weeks 5-17

Question 6

How many primitive segmental bronchi are formed in the Pseudoglandular phase?

Answer 6

16-25

Question 7

What happens in the canalicular phase?

Answer 7

Weeks 16-26

Lung develops distal architecture.
Terminal bronchioles, alveolar sacs and capillary blood vessels form gas exchange units.

Epithelial cells develop further into type 1 and type 2 pneumocytes and start producing surfactant (lipoprotein) - presence of which make it possible with intensive care to deliver baby prematurely.

Question 8

What is the limit of viability?

Answer 8

The limit at which a baby can be born and is more likely to survive than die!

Thanks to advances is currently at about week 24.

Question 9

What happens in the saccular phase?

Answer 9

weeks 26-38

Alveolar sacs begin to further develop (grow and become well formed).
Increased surfactant production and bronchioles elongate.
Reduction in interstitial tissue.

Question 10

What happens in the alveolar stage?

Answer 10

Weeks 36+

Lungs able to independently support breathing, final alveolar structures form.

Question 11

Alveolar air sac numbers, health birth - school age?

Answer 11

Birth 20-60 million, school age = 200-300 million

Question 12

What are congenital abnormalities? Are they congenital lung abnormalities common?

Answer 12

Abnormalities that develop whilst the baby is developing. They are rare.

Question 13

How are congenital abnoramilites picked up?

Answer 13

Routine antenatal ultrasound scans - MRI if we need more

May present in childhood

Question 14

How do congenital abnormlities present in newborn? Childhood?

Answer 14

Newborn: increased resp rate (Tachypnoea), Respiratory distress and feeding issues

Child: Stridor/wheeze, recurrent chest infections (pneumonia), cough, feeding issues

Question 15

What is laryngomalacia?? URT/LRT? How does it present? Intervention

Answer 15

URT
“malacia” = floppyness/softening
So Floppy larrynx, can lead to collapse of larynx/voice box. Presents Stridor, worse with feeding/upset/excited.
Usually improves by itself in the first year as airway increases in size.

Question 16

What is Tracheomalacia? Causes? Presetation? Intervention?

Answer 16

Floppy trachea.
Can be one off isolated case or genetic caused by something else abnormal pushing against the trachea.
Stridor/Wheeze/inspiratory sounds, Barking cough/ recurrent “croup”, breathless on exertion.
No intervention for treatment, but management includes physio and antibiotics if unwell as mucus etc may block if airway/will struggle to cough up all.

Question 17

Tracheo-Oesophegeal fistular? When diagnosed? Presentation? Treatment?

Answer 17

Trachea and Oesophagus don’t fully separate/ oesophagus ends in an atresia and there is a fistular (connection where there shouldn’t be one) between the trachea and stomach.
diagnosed post natally and antenatally
choking, cough with feeding, colour change, unable to pass ng (nasogastric tube)
Surgery. Complications include tracheomalacia, strictures, leak and reflux

Question 18

What is Congenital Pulmonary Airway Malformation? When detected? Treatment?

Answer 18

When the lungs haven’t formed quite right. (eg massve right bulla and compressed lung)
80% detected antenatally
Time, many resolve spontaneously in utero. If asymptomatic - conservative management. May need surgery, risk of malignant change.

Question 19

When does the diaphargm develop?

Answer 19

weeks 7-18

Question 20

What is congenital diaphragmatic hernia? Which side? Which side worse outcome? Most common type? When diagnosed? Treatment? Prognosis?

Answer 20

When the diaphargm didn’t quite form right and you may have stomach/other organs compressing lungs/within lung space.
Usually the left side, but the right side has worse outcomes.
Most common is Bochdalek (90%)
Most diagnosed antenatally.
treatment may be surgery.
prognosis dependant on degree of lung size.

Question 21

Neonatal/pre term: What is transient tachypnoea? Treatment?

Answer 21

Rapid breathing that goes away.
Usually when babies are born (especially with caesarean section) if fluid in lungs isn’t absorbed as well as it should for the babies first breath. May need oxygen/respiratory help for the first few days then will settle down.

Question 22

Preterm/some term infants - RDS what is? AKA? Treatment? What does lung look like?

Answer 22

Respiratory distress syndrome (hyaline membrane disease)
Insufficient surfactant produced (usually as born prematurely and so baby will struggle to breathe as alveoli will collapse.
Surfactant replacement, ventilation strategies, optimized nutrition, antenatal steroids - promote lung development if child expected to be preterm,
Look looks kind of foggy. ground glass like appearance (like a “hyaline membrane”)

Question 23

Neonatal lung disease: Chronic lung disease, what is? aka? Causes, represent? Why does it lead to increased childhood respiritory morbidity? In later life?

Answer 23

Associated with prematurity - ongoing oxygen requirement at term. aka bronchopulmonary dysplasia
Multifactoral causes, thought to be due to increased inflammation and infection and resulting respiratory insult that all results from being born prematurely.
Leads to increased childhood respiratory morbidity as increased tendencies for infections.
Later life may present as COPD type symptoms.

Question 24

What individual factors/early life events/environmental and lifestyle/allergic diseases at the age of 15 may affect the lungs and therefore lung diseases in adult life?

Answer 24

Individual: Age, Gender and height

Early life events: birth weight, port term oxygen, lung infections, parental atopy, maternal age at delivery, maternal smoking/second hand smoke, season of birth, breastfeeding, peak weight/height velocity

Environment and lifestyle: Smoking, air pollution, sunlight (vitD), BMI

Allergic diseases: Asthma, Rhinitis, Allergies (aeor-food allergen sensitization)

Question 25

What is remodelling? What can cause it? What changes can occur?

Answer 25

Alteration of the airway structure from external influences (Change in the epithelium cells etc)

Causes: environmental factors eg smoking, chronic diseases as a child eg chronic lung disease of prematurity/asthma/infection - abnormalities in the airways.

reduction in lumen size and increased mucus plugging, increased mucus production, interstitial change, vaso dilation, desquamatation, leukocyte infiltration, hyperplasia and muscle hypersectretion, eosinophilia, oedema, Occulsion with mucus plugs, collagen depositioo.

Question 26

What can chronic inflammation lead to?

Answer 26

diseases such as COPD

Question 27

Can lung deficits established by school age be tracked into adult life? What are they more likely to cause and what is currently being done to potentially help?

Answer 27

Yes, most likely to cause diseases such as COPD in later life. 
To help:
Diet
Exposure avoidance
Physical activity

Question 28

What is the 3rd leading cause of death in the world?

Answer 28

COPD