Embryology 3 Flashcards
Which four structures does the embryo need to develop in terms of the respiratory system?
Trachea
Lungs
Pleura
Diaphragm
What are the two layers of the bilaminar disc?
Epiblast
Hypoblast
What are the three layers of the trilaminar disc?
Ectoderm
Mesoderm
Endoderm
What is the name of the process which turns the bilaminar disc to the trilaminar disc?
Gastrulation
What else is found between the trilaminar disc?
Notochord
What happens during lateral folding?
Somatic mesoderm folds down to surround the splanchnic mesoderm of the intraembryonic body cavity
What happens to the yolk sac during the lateral folding process?
It gets absorbed into the primitive gut.
Where do the lungs and trachea form from?
Foregut part of the primitive gut tube
What does the folding of the embryo give rise to?
Primitive gut tube
Where does the primitive gut tube form from?
Endoderm
Where is the somatic layer of the mesoderm?
Close to the endoderm.
Where is the splanchnic layer of the mesoderm?
Close to endoderm/gut tube
At how many weeks do the lung buds form?
4
Where do the lung and trachea buds come from?
Bud out from the ventral/anterior wall of the primitive foregut (endoderm)
What are the lung and trachea buds closely surrounded by?
Lateral plate splanchnic (visceral) mesoderm
Where is the trachea related to the oesophagus?
Trachea lies anterior to oesophagus
What are the three portions of the gut?
Foregut
Midgut
Hindgut
What develops between the oesophagus/pharynx and the trachea, completely separating them?
Oesophagotracheal septum
What may occur is the oesophagotracheal septum doesn’t form?
Tracheoesophageal fistula (TOF) and Oesophageal Atresia
Define fistula
An abnormal passage between 2 epithelialized tubes or surfaces.
Define artesia.
Condition in which an orifice or passage in the body is closed or absent.
What type of pleura is the lung covered with?
Visceral
What type of pleura are the lungs lined with?
Parietal pleura
Describe the growing of the lung buds.
Each lung bud invaginates the wall of the coelomic cavity and then grwos to fill a greater part of the cavity.
Pleura then forms.
What happens to the coelomic cavity as a result of the lungs growing?
Reduced to a slitlike space known as the pleural cavity
Where does the pleura develop from?
Lateral plate mesoderm
Which layers of the lateral plate mesoderm forms-
1. the visceral pleura
2. the parietal pleura
- Visceral= splanchnic layer
- Parietal= somatic layer
Describe the formation of the pleural cavity
Lung buds push the splanchnic mesoderm towards the somatic mesoderm and become completely surrounded by both layers.
The space between the two layers will become the pleural cavity.
However, the space between the splanchnic and somatic mesoderm around the lungs is initially continuous with what?
What is this continuity called?
Pericardial and peritoneal cavity
Pericardioperitoneal canal.
Why does the pleural cavity need to be separated off from the pericardioal and peritoneal cavity?
To maintain the correct ventilatory pleural cavity pressures.
How is the the pericardoperitoneal canal separated from the pericardial cavity?
Formation of the pleuropericardial folds
Describe the structure of pleuropericardial folds.
Formed from the body wall and lined by somatic mesoderm
When is the Pseudoglandular stage?
7-17 weeks
What happens in the Pseudoglandular stage?
Development of lung except respiratory part
When is the Canalicular stage ?
Weeks 17-27
What happens in the Canalicular stage ?
Formation of respiratory part. Alveolar ducts form and epithelium starts to differentiate into Type I and Type II pneumocytes
When is the Saccular stage ?
Weeks 27-40
What happens in the Saccular stage ?
Formation of alveolar sacs, primitive alveoli and surfactant
At what stage does gas exchange begin to happen?
Saccular stage
When is the alveolar stage?
32 weeks-8 years old
What happens in the alveolar stage?
Proliferation of alveoli into alveolar scas
What is Neonatal Respiratory Distress Syndrome ?
Partial collapse of the alveoli
hat cuases Neonatal Respiratory Distress Syndrome?
Surfacing deficiency
What % of neonates are affected by Neonatal Respiratory Distress Syndrome?
2%
What happens because of the partial collapse of the alveoli?
Debris consisting of blood elements accumulate
->this gives a glassy appearance under the microscope because of hyaline membranes
What is lung agenesis caused by?
-Failure of lung bud to develop/ branch
-Insufficient mesoderm
-Teratogens
What is pulmonary hypoplasia?
Incomplete development of the lungs, resulting inan abnormally low number or size of bronchopulmonary segments or alveoli.
What closes off the pleural cavities from the peritoneal cavity of the abdomen?
Pleuroperitoneal folds/membranes forming the diaphragm
What part of the diaphragm does Septum transversum form?
Central tendon of the diaphragm
What forms the muscular part of the diaphragm?
Skeletal muscle ingrowth from the peripheral body wall
What does the dorsal mesentery of the oesophagus do?
Attaches the embryological oesophagus to the posterior thoracic wall
Skeletal muscle from the periphery covers the dorsal mesentery to form what?
Diaphragmatic crura.
Name the four structures which form the diaphrgam.
Septum transversum
Pleuroperitoneal folds
Skeletal muscle ingrowth from the peripheral body wall
The dorsal mesentery of the oesophagus
Name three weak areas in the developed diaphragm
Oesophageal hiatus
Foramen of Bochdalek
Foramen of Morgagni
What can happen at the Foramen of Bochdalek or the Foramen of Morgagni?
Diaphragmatic hernia
What can happen at the Oesophageal hiatus?
Hiatus hernia
Define hiatal hernia
Protrusion of an organ through the structure or muscle that usually contains it.
