development of the lungs

Question 1

special characteristics of the lungs

Answer 1

late to functional development

only system not to be operational before birth

Question 2

development respiratory diverticulum

Answer 2

forms at week 4
ventral out pouching of foregut from splanchnopleure
respiratory epithelium derived from splanchnic endoderm
supporting mesenchyme from splanchnic LP mesoderm

Question 3

starts of the development of the lungs

Answer 3

first bifurcation creates the primary bronchi

Question 4

stage 1 of the development of the lungs

Answer 4

embryonic stage

• primary bronchial buds branch into secondary bronchi
• secondary bronchi branch and create tertiary bronchi, vasculogenesis also occurs around airway buds

Question 5

secondary bronchi

Answer 5

called lobular bronchi because they are equal to the number of lobes

Question 6

tertiary bronchi

Answer 6

future bronchopulmonary segments

Question 7

stage 2 of development of the lungs

Answer 7

pseudo glandular phase
final number of bronchopulmonary segments are fromd
terminal bronchiole branches develop from tertiary bronchi
still has thick wall and dense mesenchyme

Question 8

stage 3

Answer 8

canalicular phase (w28-36)
terminal bronchioles bud into respiratory bronchioles, alveolar ducts and primitive alveoli 
walls thin and epithelium begins to differentiate

Question 9

stage 4

Answer 9

saccular stage
develop alveolar sacs - primitive alveoli
type 1 and 2 pneumocystis develop
surfactant begins being produced in a greater quantity and quality

Question 10

stage 5

Answer 10

alveolar stage
alveolarisation - septation and multiplication of alveoli
primitive alveoli continue to differentiate into definitive alveoli
further thinning of airspace walls
form and differentiate in craniocaudal fashion

Question 11

stage 5 divided into

Answer 11

two stages
63w - 2/3 years - first phase of alveolarisation
2/3 years - 18/22 years - second phase of alveolarisaton
until 18-22 years: enlargement of terminal bronchioles and alveoli

Question 12

first stage 5

Answer 12

fast

Question 13

second tage 5

Answer 13

slow

enlargement of terminal bronchiole and alveoli

Question 14

stage 6 - microvascular maturation

Answer 14

birth - 3-21 years
time Fram remains uncertain
fusion of aveolar capillary networks

Question 15

septum transversum

Answer 15

becomes the central tendon of the diaphragm

foremost mesenchymal tissue of the embryonic disk, cranial to the cardioogenc centre

Question 16

movement of the septum transverse

Answer 16

originally cranial to the cariogenic centre
cranial part of head tail folding drags it in front of the yolk sac
arrests caudally to the heart

Question 17

what becomes the central tendon of the diaphragm

Answer 17

septum transversum

Question 18

where does the diaphragm muscle develop

Answer 18

under the tongue C3-5
migrate ventrally and caudally, through the lateral aspect of body wall
within the developing pleuropericardial folds

Question 19

developing lung buds

Answer 19

push on coelomic space dorsal to the phrenic nerve

the body wall grows outward faster so the pleural space is always going to be larger

Question 20

tracheoosophageal fistula

Answer 20

when the oesophagus doesn’t directly connect to the stomach
connected to the trachea
with or without concurrent atresia of trachea/oesophagus

Question 21

congenital diaphragmatic hernia

Answer 21

incomplete fusion of septum transversum and pleuroperitoneal fold
50% mortality rate

part of the colon comes up through the unfused pleuroperitoneal canal

Question 22

asymmetric branching abnormalities

Answer 22

unilateral agenesis - no development of a lung
aplasia - bronchi but no lung tissue (almost a lung)
hypoplasia - some lung tissue but no alveoli, just conductive tubes

Question 23

unilateral agenesis

Answer 23

missing lung - trachea not bifurcated

Question 24

branching abnormality - aplasia

Answer 24

bronchi but no lung tissue

Question 25

branching abnormality - hypoplasia

Answer 25

some lung tissue but no alveoli

Question 26

surfactant production

Answer 26

only starts 24-34 weeks - variable
holds smaller airways open by reducing surface tension of the fluid around the alveoli
results in equalised air flow to variably sized air sacs
needs to be constantly produced in high quantity and quality

Question 27

lack of surfactant

Answer 27

cannot retain air once inflated = respiratory distress syndrome
damage and developmental impairment and mortality
low survival

Question 28

purpose of surfactant

Answer 28

x10 drop in surface tension

Question 29

respiratory distress syndrome

Answer 29

lack of surfactant at birth

Question 30

considerations for pre term birth

Answer 30

1. surfactant to be produced
2. lungs need to have minimal diffusion distance
3. diaphragm needs to be able to do the work of breathing
4. thorax needs to be rigid enough to resist the diaphragm

Question 31

when is surfactant produced enough

Answer 31

usually 28 weeks

Question 32

when does the saccular stage happen

Answer 32

28-36 weeks
term is 38 weeks
therefore primitive alveoli are still forming 2 weeks before birth
surfactant may not be being formed enough in time for birth if premature

Question 33

movement of septum transversum

Answer 33

originally cranial to the cariogenic centre
head part of head tav folding drags t is from of the heart
arrests at the underside of the heals

Question 34

what do the pleuralpericardall folds do

Answer 34

petition the chest into 3 cavities

means that the other side can function even if one is collapsed

Question 35

plueropericardal and plueroperitoneal folds

Answer 35

plueropericardal fold s the fold created by the phrenic nerve
pluertoperitoneal fold is the space occluded by the pleuropericardial fold

Question 36

pericardioperitoneal canals are closed by

Answer 36

plueroperitoneal fold to form pleuroperitoneal membrane

Question 37

muscular ingrowth from the body wall

Answer 37

forms part of the diaphragm

Question 38

oesophageal mesentery forms

Answer 38

crura of the diaphragm

Question 39

pre term birth implication of compliance

Answer 39

preterm babies have not sufficiently red ribs

when the diaphragm moves, the walls collapse with the diaphragm and volume/pressure isn’t changed