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Body Systems > Respiratory strand: Lecture 7 - Development of Lungs > Flashcards

Respiratory strand: Lecture 7 - Development of Lungs Flashcards

1
Q

How is the respiratory tract divided anatomically?

A
  • Upper respiratory tract

- Lower respiratory tract

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2
Q

What does the upper respiratory tract consist of?

A
  • nasal cavities
  • nasopharynx
  • oropharynx
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3
Q

What does the lower respiratory tract consist of?

A

-trachea
-bronchi
-bronchioles
-terminal bronchioles
-respiratory bronchioles
-alveolar ducts
-alveolar sacs
-alveoli
diagram slide 3

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4
Q

What structure divides the URT from the LRT?

A

The larynx

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5
Q

What are the 3 germ layers?

A

ectoderm
mesoderm
endoderm

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6
Q

Which germ layer does the inner epithelial lining come from?

A

endoderm

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7
Q

Which germ layer does the connective structures like blood vessels come from?

A

mesoderm

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8
Q

Give 5 developments of the embryo by week 4?

A
  • yolk sac visible
  • somites visible
  • CNS development
  • gut tube formed
  • respiratory diverticulum (lung bud) appears in ventral wall of foregut
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9
Q

How is the gut tube divided?

A

-foregut (area above septum transverse)
-midgut (yolk sak)
-hindgut (anything distal/below yolk sak)
image slide 5

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10
Q

What occurs in the gut tube?

A

Its where we develop our respiratory system via the respiratory diverticulum

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11
Q

What occurs on day 22?

A

Lung bud forms

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12
Q

In which direction does the lung bud grow?

A

ventrocaudally

front and tail ways

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13
Q

What separates the respiratory diverticulum from the foregut?

A

tracheoesophageal ridges

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14
Q

What is happening in this image?

slide 6

A
  • ventrally, trachea and lung bud divide to form two lung buds
  • yellow and blue tube separate to form oesophagus and trachea
  • separate trachea and oesophagus then a trachea septum
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15
Q

What is a fistula?

A

An abnormal communication/ connection

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16
Q

What is a TOF?

A

Tracheoesophageal fistula -

abnormal connection between trachea and oesophagus

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17
Q

Why might a TOF occur?

A

from incomplete division of the foregut into oesophageal ad respiratory portions

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18
Q

What is oesophageal atresia?

A

slide 7 configuration A

  • closed or absent oesophagus
  • distal part of oesophagus still connected to trachea - narrowed so much it closes
  • upper oesophagus ends abruptly; lower oesophagus forms fistula with trachea
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19
Q

What is the effect of a Tracheoesophageal Fistula with Oesophageal Atresia?

A
  • abdomen rapidly distends as stomach fills with air (air goes down trachea and escapes into oesophagus and then stomach)
  • stomach contents can make way up to the respiratory system from the oesophagus
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20
Q

What is an H type tracheoesophageal fistula?

A

-much more rare than TOF
-isolated fistula
-milk may be ‘driven’ into respiratory system
slide 9

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21
Q

What does the VACTERL or VATER acronym stand for? why is it important?

A 
V-  Vertebral defects 
A- Anal atresia 
(C)- Cardiac defects
T - Tracheo-oesophageal fistulas 
E- Esophageal atresia 
R - Renal abnormalities 
(L) - Limb defects 
TOF's are usually associated with other congenital abnormalities - most commonly cardiac defects
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22
Q

What happens during partitioning of oesophagus and respiratory diverticulum?

A

Right and left lung buds form

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23
Q

What happens during week 5?

A
  • further growth and differentiation results in formation of main bronchi
  • main bronchi form secondary bronchi (3 right, 2 left)
24
Q

What happens during week 6?

A

-further branches results in the formation of the tertiary bronchi - these will each supply a bronchopulmonary segment / bronchial tree (10 right, 8 left)
image slide 11

25
Q

What happens by week 16?

A

branching continues to form terminal bronchioles

26
Q

What happens by week 26?

A
  • forms respiratory bronchioles

- gaseous exchange can occur (although inefficient)

27
Q

What happens by week 36?

A

first alveoli develop

28
Q

How is branching regulated?

A

-By the interaction of the epithelium (derived from the foregut) with the overlying visceral mesoderm

29
Q

What do the cartilage, smooth muscle, connective tissue and capillaries form from?

A

Formed from visceral mesoderm

30
Q

Which germ layer forms the pleura?

A

Mesoderm

31
Q

How do we ensure the branching pattern is correct?

A

Its regulated by the mesoderm and endoderm - they send signals and communicate with each other to stimulate the correct branching pattern

32
Q

What does the mesoderm split into?

A

The visceral mesoderm and parietal mesoderm

33
Q

What does the visceral mesoderm form?

A

The visceral pleura

34
Q

What does the parietal mesoderm form?

A

The parietal pleura

35
Q

What is pulmonary agenesis?

A
  • Failure to form a lung

- complete absence of bronchi and vasculature

36
Q

When does this occur?

A

When a lung bud fails to split

37
Q

What are the two types of pulmonary agenesis?

which is the most severe?

A

unilateral or bilateral

bilateral genesis is incompatible with life

38
Q

What is the clinical presentation of unilateral pulmonary agenesis?

A
  • child usually develops respiratory distress
  • remaining lung is compromised, usually by LRT infection
  • 60% have other congenital anomalies including cardiac lesions, diaphragmatic hernias, and skeletal abnormalities
  • agenesis of the right lung is associate
39
Q

If you have left agenesis, what will your right lung look like?

A

it will be enlarged as its compensating

40
Q

What is pulmonary hypoplasia?

A
  • all components are developed, but incompletely developed
  • severity of hypoplasia determines the degree of respiratory compromise
  • may be found in association with congenital diaphragmatic hernia (CDH)
41
Q

Whats the definition of hypoplasia?

A

Fails to form fully

42
Q

What is branching morphogenesis?

A
  • Supernumerary lobes and segments
  • when branching pattern goes wrong
  • little functional significance
43
Q

Explain the 4 periods of maturation of the lung?

A
  1. Pseudoglandular
  2. Canalicular
  3. Saccular/ terminal sac
  4. Alveolar

image slide 17 - little overlap between each process

44
Q

When is the pseudo glandular period?

A

5-17 weeks

45
Q

What occurs in the pseudo glandular period?

A
  • branching of the respiratory tree has occurred to form terminal bronchioles
  • respiration is NOT possible; therefore foetus could not survive
46
Q

When is the canalicular period?

A

16-25 weeks

47
Q

What occurs during the canalicular period?

A
  • terminal bronchioles give rise to respiratory bronchioles, which give rise to alveolar ducts
  • mesodermal tissue becomes highly vascularised
  • respiration is possible towards end of canalicular period as some terminal sacs have developed at the ends of the respiratory bronchioles
  • inefficient gaseous exchange can occur: better prognosis for birth at this point
48
Q

When is the terminal sac period?

A

26 weeks - birth

49
Q

What occurs during the terminal sac period?

A
  • further terminal sacs (primitive alveoli) develop
  • epithelium thins and capillaries come into ‘contact’ with epithelium
  • blood-air barrier formed
  • surfactant forms a film over the internal walls of terminal sacs
  • decreases surface tension thus facilitating inflation
  • foetus born prematurely (24 weeks) can survive if given intensive care but may suffer from respiratory distress
50
Q

What does surfactant do?

A

Prevents alveoli from collapsing when theres low pressure

51
Q

When is the alveolar period? (where we develop alveolar sacs)

A

36 weeks- 8 years

-95% of mature alveoli do not develop after birth

52
Q

Why do the lungs develop mostly after birth?

A

Due mainly to an increase in the number of respiratory bronchioles and alveoli

53
Q

When do breathing movements start?

A

in utero

this serves to remove amniotic fluid (we inspire it)

54
Q

What happens to any remaining lung fluid at birth?

A

Its reabsorbed by capillaries

55
Q

Why do you have a good chance of survival if you’re born from 26 weeks onwards?

A

Surfactant is produced in sufficient qualities

56
Q

What will occur for a birth at 23 weeks?

A
  • laboured breathing
  • increased rate of breathing
  • mechanical ventilation needed
  • damage to alveolar lining; fluid and serum proteins leak into alveolus
  • bronchopulmonary dysplasia (abnormal formation)
57
Q

What does glucocorticoid treatment do?

A

Accelerates fatal lung development and surfactant production
this must be taken before birth to increase surfactant

Body Systems (24 decks)

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