Embryology 3 Flashcards
What is a summary for the development of the respiratory system?
1) Tubular outgrowth from foregut (oesophagus)
2) This outgrowth will develop into the trachea and lung buds
3) Trachea will seperate from oesophagus and lung buds will proliferate
4) Proliferating lung buds will invaginate laterally into the pleural cavities, so forming visceral and parietal pleural and the pleural cavity
5) Meanwhile, transverse septal ‘shelf’ will begin to develop between thorax and abdomen, below the pleural cavities
6) This shelf is composed of 4 components, which fuse to form the diaphragm
7) But sometimes things go wrong with the embryonic tracheal, lung and diaphragmatic formation which results in congenital abnormalities
When does folding of the embryo occur?
Week 3
What does folding give rise to?
Gut tube
What does the gut tube form from?
Endoderm
What does the trachea and lungs form from?
Foregut
What is step 1 in development of the respiratory system?
Development of the trachea and the lungs
When does development of the trachea and the lungs occur?
Week 4 of gestation
Where does the development of the trachea and lungs begin from?
Ventral wall of foregut
What is A?
Hindgut
What is B?
Yolk sac
What is C?
Foregut
What is D?
Primitive gut
What is E?
Notochord
What is F?
Neural tube
What is the process of the development of the trachea and lungs?
1) Respiratory primordium starts as a median outgrowth (diverticulum) - laryngotracheal groove - from vental part of the foregut
2) Diverticulum (part of endoderm) becomes invested (covered) with mesoderm on its outside and enlarges to form trachea and lung buds
3) A septum (oesophagotracheal septum) develops between the oesophagus and trachea, completely seperating them
What is the diverticulum part of?
Endoderm
What does the diverticulum become covered by to form the trachea and lung buds?
Mesoderm
What is the median outgrowth called that goes on to form the trachea and lung buds?
Laryngotracheal groove (diverticulum)
What septum develops between the oesophagus and trachea to completely seperate them?
Oesophagotracheal septum
When is the development of the trachea and lung buds completed?
Week 8
What sometimes happens to the oesophagotracheal septum?
It does not completely seperate the trachea and the oesophagus
What are examples of diseases due to the septum not completely seperating the trachea and oesophagus?
Fistula
Atresia
What is a fistula?
Abnormal or surgically made passage between a tubular organ and the body surface, or between two hollow or tubular organs
What is an abnormal or surgically made passage between a tubular organ and the body surface, or between two hollow or tubular organs called?
Fistula
What is an atresia?
A condition in which an orifice or passage in the body (usually abnormal) is closed or absent
What is the condition in which an orifice or passage in the body (usually abnormal) is closed or absent called?
Atresia
What stage is after the development of the trachea and lung buds (stage2)?
Development of the pleural cavities and pleurae
What is the process for the development of the pleural cavities and the pleurae?
1) As the lungs develop they acquire a layer of visercal pleura from the splanchnic mesoderm
2) The thoracic wall becomes lined by a lyer of parietal pleura, derived from somatic mesoderm
3) Gap between parietal and visceral pleurae called pleuroperitoneal canals (eventually becomes pleural cavities)
4) Pleuropericardial folds form around primitive heart deperating pleural cavities from pericardial cavity
What does the visceral and parietal pleura develop from?
Splanchnic mesoderm
What develops into the pleural cavity?
Pleuroperitoneal canals
What does the pleuroperitoneal canals eventually develop into?
Pleural cavities
How is the pleural cavities seperated from the pericardial cavity?
Pleuropericardial folds form around primitive heart
What happens after the pleural membranes have formed?
They differentiate:
1) Lung buds punch into the visceral mesoderm
2) Mesoderm which covers the outside of the lung develops in the visceral pleural
3) Somatic mesoderm covering the body wall from the inside becomes the pleura, with the space between ebing the pleural cavity
What happens after the differentiation of the pleura?
Differentiation of the lung buds
What stages can the foetal period be divided into?
Pseudoglandular stage (7-17 weeks)
Canalicular stage (17-27 weeks)
Saccular stage (27-40 weeks)
When is the pseudoglandular stage from?
7-17 weeks
When is the canalicular stage from?
17-27 weeks
When is the saccular stage from?
27-40 weeks
What happens during the pseudoglandular stage?
Setup of all pulmonary structures except elements needed for gas exchange
What happens during the canalicular stage?
Terminal bronchioles give rise to tubular tubes that make up respiratory part of the lung
Differentiation of epithelium into type II pneumocytes which will synthesis surfactant and flat cell type I pneumocytes
What happens during the saccular stage?
Formation of alveolar sacs
Alveolar sacs progressively divide into smaller subunits leading to the formation of the alveoli
What stage is the postnatal period composed of?
Alveolar stage
When is the alveolar stage from?
Week 32 to 8 years
What happens during the alveolar stage?
Formation of alveoli from terminal sacs
95% off adult-like alveoli formed postnatally
Alveoli enlarge
Number of respiratory bronchioles (and alveoli) increase as lungs enlarge, by age 8 number of alveoli reaches adult number (about 300 million)
What percentage of adult like alveoli form postnatally?
95%
By what age do you have your adult number of alveoli?
Age 8
How much alveoli do you have by age 8?
About 300 million
What does congenital conditions mean?
Present at birth
What is a condition present at birth called?
Congenital
What are examples of congenital conditions?
Surfactant and respiratory distress syndrome
Accessory lobes
Lobe of azygos vein
Ageneis of lung
What does RDS stand up for?
Respiratory distress syndrome
What is respiratory distress syndrome also known as?
Hyaline membrane disease (HMD)
What does HMD stand up for?
Hyaline membrane disease
What percentage of neonatal disease does respiratory distress syndrome make up?
30%
What is the major cause of respiratory distress syndrome?
Surfactant deficiency
What is respiratory distress syndrome?
Babies lungs are not fully developed and cannot provide enough oxygen
What are accessory lobes?
Additional lobes
What are additional lobes called?
Accessory lobes
What is lobe of azygos vein?
Laterally displaced azygos vein creates a deep pleural fissure onto the right upper lobe
What is it called when a latterally displaced azygos vein creates a deep pleural fissure onto the right upper lobe?
Lobe of azygos vein
What is ageneis of the lung?
Unilateral or bilateral absence of lung tissue
What is unilateral or bilateral absence of lung tissue called?
Ageneis of the lung
What occurs after differentiation of the lung buds (step 4)?
Development of the diaphragm
What are the 4 surrounding embryonic structures that develop into the diaphragm?
Septum transversum
Pleuroperitoneal membranes
Dorsal mesentery of oesophagus
Muscular ingrowth from lateral body walls
What does the septum transversum become?
Central tendon
What develops into the central tendon?
Septum transversum
What does the pleuroperitoneal membranes become?
Primitive diaphragm
What is the primitive diaphragm developed from?
Pleuroperitoneal membranes
What does the dorsal mesentery of oesophagus become?
Median portion and crura of diaphragm
What develops into the median portion and crura of the diaphragm?
Dorsal mesentery of oesophagus
What does the muscular ingrowth from lateral body walls develop into?
Peripheral parts of the diaphragm
What develops into the peripheral parts of the diaphragm?
Muscular ingrowth from lateral body walls
Where is the septum transversum initially location?
Opposite C3-C5 somites (week 3)
When is the septum transversum location opposite C3-5 somites?
Week 3
What does the septum transversum do during the development of the diaphragm?
Migrates from C3-5, bringing down the spinal nerves with it (phrenic nerves)
What nerve supplies the diaphragm?
Phrenic (C3-5)
What congenital abnormalities can occur during the development of the diaphragm?
Failure of the diaphragm to completely close during development
Herniation of the abdominal contents into the chest
Pulmonary hypoplasia
What is pulmonary hypoplasia?
Incomplete development of the lungs, resulting in a low number of bronchopulmonary segments
What is incomplete development of the lung, resulting in a low number of bronchopulmonary segments known as?
Pulmonary hypoplasia
What is a hernia?
General term used to describe a bulge or protrusion of an organ through a structure or muscle that usually contains it
What are some examples of different kinds of hernia?
Posterolateral hernia
Anterior hernia
Central hernia
What is A?
Posteolateral hernia
What is B?
Anterior hernia
What is C?
Central hernia
What is a hiatal hernia?
Upper part of your stomach bulges through an opening in the diaphragm
What is it called when the upper part of your stomach bulges through an opening in the diaphragm?
Hiatal hernia
What are examples of hiatal hernia?
Sliding hiatus hernia
Paraeosophageal hiatus hernia
What is A?
Sliding hiatus hernia
What is B?
Paraeosophageal hiatus hernia
