Development of the respiratory system Flashcards
What does the ectoderm develop and what does this have?
develops a neural groove and the tips of the walls of this groove are called the neural crest
What does the lateral plate mesoderm divide into?
2 layers
- parietal (somatic)
- Visceral (splanchnic)
What does the parietal layer of mesoderm form?
body walls
What does the visceral layer of lateral plate mesoderm form?
surround the organs
What does the parietal layer of the lateral plate mesidern ‘merge’ with?
ecotderm
What two processes occur during lateral folding of the trimlaminar embryo?
- primitive tolk sac becomes “pinched”. Primitive yolk sac will become the digestive tract or the gut tube. While this takes place, the visceral layer of the lateral plate mesoderm will envelope to the future gut tube
- The leading edge of the ectoderm and the pariteal layer of lateral plate mesoderm will move antero-medially
Draw a diagram illustrating what happens during lateral folding of the trilaminar embryo
Draw a diagram of the trilaminar embryo
What fuse together in the ventral mid line at the end of lateral folding?
parietal layer of lateral plate mesoderm and ectoderm
What becomes the parietal pleura?
parietal layer of lateral plate mesoderm
What are the main features of the embryo at the end of lateral folding
- a cavity (the coelom) which will become the thoracic abdominal cavity (the cavities are continuous cia the pericardio-peritoneal canals until the diaphragm forms)
- A body wall (thoracic wall) made out of a surface of ectoderm and pariteal layer of lateral plate mesoderm deep to it
- The gut tube, suspended by visceral layer of lateral plate mesoderm
What also occurs while lateral folding is taking place?
cranio-caudal folding
Draw what an embryo looks like at the end of lateral folding of the trilaminar embryo
What happens when the embryo is about 4 weeks old?
In the cervical portion of the gut tube, in the ventral midline, the respiratory diverticulum starts to appear
How does the respiratory diverticulum expand?
Ventrally and towards the chest, in front of the gut tube
How is the respiratory diverticulum separated from the gut tube?
trans-eosphgeal ridges grow towards each other
What does the diverticulum bifurcate into? And what subsequently happens?
2 branches
later these 2 branches expand and dilate. terminal ends of these dilations are called lung buds that will become lungs
What does the gut tube into?
the digestive tract between the mouth and the anus
When do pharyngeal arches start to appear?
4th-5th weeks of development
What are pharyngeal arches separated by?
pharyngeal clefts
How many pharyngeal arches are there? How are they numbered and what elements do they contain?
5
Numbered 1,2,3,4,6
- cartilaginous element
- an artery (aortic arch)
- a nerve (Cranial)
What is maintained even though the tracheo-esophgeal septum separated the gut tube from the upper respiratory tract
laryngeal opening
What does the upper end of the respiratory diverticulum become?
larynx
What does the middle section of the respiratory diverticulum become?
trachea
What does the lower end of the respiratory diverticulum become?
tertiary bronchi, broncioles and the alveoli
What does the bronchial tree push against as it grows and expands?
visceral layer of lateral plate mesoderm; which develops into visceral pleura
Where is the epithelium of the respiratory system derived from?
endoderm
The lung develops in 4 overlapping stages. What are these?
- Pseudoglandular
- Canalicular
- Terminal Saccular
- Alveolar
What 2 stages are no compatible with life?
- Pseudoglandular
- Canalicular
What secretes surfactant? And from when?
type 2 pneumocytes
from 20 weeks
From when can the foetus survive?
28 weeks
What are the four sources of origin of the diaphragm?
- pleura-peritoneal folds
- pleura-peritoneal folds fuse with septum transversum
- Mesentary of the oesphagus
- Muscular in-growth from the body wall
What does the septum transversum form?
the central tendon of diaphragm
contains myoblasys frim the somites in C3,4,5 (phrenic nerve)
What do the crura develop from?
mesentary of the oesphagus
What causes a diaphragmatic hernia
failure of fusion
Explain the 5 types of tracheo-esophgeal fistula
A + B = congenital abnormalities of the trachea and oesophagus, there is communication between the trachea and oesphagus, usually companied by esophageal atresia (gut = disconnected)
C, D + E = When the baby attempts to feed milk enters the trachea causing choking and possibly pneumonia. there is also the potential for retrograde passage of gastric acid from the GI tract into the respiratory system
What is the most common congenital disorder of the respiratory system?
oesophgeal atresia
What occurs in oesophgeal atresia?
During a normal pregnancy, the foetus swallows amniotic fluid which is resorbed from the gut and returned to the maternal circulation
If oesophageal atresia develops, this circulation of fluid is prevented and polyhydramnios develops (excess amniotic fluid)
What are the 3 different types of diaphragmatic hernia?
What causes respiratory distress syndrome?
deficiency in surfactant
