Embryology 3 Flashcards
what does splanchnic mean?
surrounds organs
development of airways: where does the tubular outgrowth come from?
from the foregut (oesophagus)
what will the tubular outgrowth develop into?
trachea and lung buds
what happens before the lung buds start proliferating?
trachea separates from oesophagus
what do the lung buds do when they start proliferating? what do they form?
invaginate the pleural cavities laterally, forming visceral and parietal pleural and pleural cavity
what structure begins to develop between thorax and abdomen?
transverse septal “shelf”
how many components make up the transverse septal “shelf”?
4
what happens if problems occur in development?
congenital abnormalities
on which week does the tubular outgrowth come out of the foregut?
4th week
which of the 3 layers makes up the visceral and parietal pleura?
mesoderm
which part of the mesoderm gives the visceral and parietal pleura
visceral: mesoderm which covers the outside of the lung
parietal: mesoderm which covers the body wall from the inside
when does the lung bud begin pseudo glandular?
7th week
when do canals develop on the distal end of the buds? (canalicular development)
17th week
when does saccular development take place? (primitive alveoli)
27th week
when do the alveolar start developing?
40th week
which component of the transverse septal “shelf” forms the tendinous part of the diaphragm?
septum transversum
which components of the transverse septal “shelf” forms the muscular part of the diaphragm?
2 pleuroperitoneal membranes (form primitive diaphragm), peripheral body of wall muscle (form peripheral parts of diaphragm)
which component of the transverse septal “shelf” forms crura of diaphragm? (and median portion of diaphragm)
mesentery of oesophagus
at what point is the primitive gut tube formed?
folding of embryo, week 3
what are the two extremities of the gut called at week 3?
hindgut and foregut
which sac forms the inside of the gut?
yolk sac
where do the trachea and lungs develop?
from ventral wall and foregut
where does the respiratory primordium (tissue at its earliest stage) come from?
median outgrowth called the laryngotracheal groove (diverticulum) from ventral part of the foregut
which of the 3 layers gives the diverticulum?
endoderm
what is the diverticulum surrounded by on its outside?
mesoderm, then enlarges to form trachea + lung buds
how does the forgut and the respiratory diverticulum get separated?
oesophagotracheal septum develops between oesophagus and trachea, completely separating them
what is a fistula?
an abnormal or surgically made passage between a hollow or tubular organ and the body surface, or between two hollow or tubular organs, i.e.: between 2 epithelialized surfaces
how common is tracheoesophageal fistula (TOF)? what type of abnormality is it?
TOF is a common congenital abnormality
what is atresia?
a condition in which an orifice or passage in the body is (usually abnormally) closed or absent
does the visceral pleural come from the splanchnic or the somatic mesoderm?
splanchnic
does the parietal pleural come from the splanchnic or the somatic mesoderm?
somatic
EMBRYONIC PERIOD what day does the lung appear? under which form?
26th day, in the form of a respiratory diverticulum in the ventral part of the digestive tract
EMBRYONIC PERIOD what does the respiratory diverticulum create?
a median trachea and two lateral pockets
EMBRYONIC PERIOD what other component develops at the same time?
vascular connections
EMBRYONIC PERIOD at which aortic arch do the pulmonary arteries individuate?
6th aortic arch
FOETAL PERIOD what happens during the pseudoglandular stage?
setup of all pulmonary structures except elements needed for gas exchange
FOETAL PERIOD what happens during the canalicular stage?
- terminal bronchioles give rise to tubes that make up the respiratory part of the lung
- differentiation of epithelium into cuboidal secretory cells (type 2 pneumocytes) which will synthesise the surfactant, and flat cells (type 1 pneumocytes)
FOETAL PERIOD what happens during the saccular stage?
- formation of alveolar sacs separated by primary septa
- alveolar sacs will be progressively divided into smaller subunits by secondary septa, leading to the formation of alveoli
POSTNATAL PERIOD what happens during the alveolar stage?
- formation of alveoli from terminal sacs
- about 95% adult-like alveoli formed postnatally
- alveoli enlarge
- number of respiratory bronchioles (and alveolar ducts and alveoli) increase as lungs enlarge
- by 8y of age number of alveoli reaches adult number
how many alveoli does an adult have?
about 300m
what does RDS/HMD stand for?
surfactant + respiratory distress syndrome (= hyaline membrane disease)
what percentage of neonates are affected by RDS?
2%
what percentage of neonatal disease is RDS?
30%
what is the major cause of RDS?
surfactant deficiency
what other congenital conditions can come from the respiratory system development?
- accessory lobes
- lobe of azygos vein (vein ends up surrounded by lung)
- agenesis of lung
where is the septum transversum located in week 3? (before formation of diaphragm)
opposite C3-C5
which way does it migrate during development of diaphragm?
caudally (getting closer to thoracic region)
which spinal nerves does it bring with it? how does this compare with the root of the phrenic nerves?
C3-C5, coincidence? i think not
what 3 types of congenital abnormalities can affect the diaphragm?
- failure of the diaphragm to completely close during development
- herniation of the abdominal contents into the chest
- pulmonary hypoplasia
what is a hernia?
general term to describe a bulge or protrusion of an organ through the structure or muscle that usually contains it
what two types of hernia can you get with the diaphragm?
diaphragmatic hernia, opposed to hiatal hernia
what is a diaphragmatic hernia?
tendinous part of diaphragm moves anteriorly, posteriorly or centrally
what is a hiatal hernia? what are the 2 types of hiatal hernia?
protrusion of the stomach across the diaphragm because the diaphragm is too weak:
- sliding hiatus hernia (stomach goes up oesophagus a wee bit)
- paraesophageal hiatus hernia (stomach protrudes NOT in the oesophagus)
