Embryology part 2 Flashcards
What does the ectoderm go on to form ?
The epidermis of the skin and the neural tube
What does the paraxial mesoderm go on to from ?
The dermatome, myotome and sclerotome
What does the intermediate plate mesoderm go onto form ?
The urogenital system (kidneys and reproductive)
What does the lateral plate mesoderm go onto form ?
The peritoneum, pleura and body cavities
What does the endoderm go onto form ?
The respiratory system
What happens to the bilaminar plate after the mesoderm has split?
It starts to fold and this creates the head and the bottom
What is teratology ?
The study of the things which can go wrong during a babies development
What are some examples of teratogens?
Environmental factors = Drugs, alcohol, tobacco, infectious agents, radiation, virus
Genetics
What affects the risk which a teratogen poses ?
- The period of exposure. The earlier on the terogen is encountered in the pregnancy the more risk it carried. (3-8 weeks is the greatest risk)
- Dosage
- Genetic constitution of the embryo some are more susceptible to teratogens
Suggest some investigations that can be antenatally to find the damage done by a teratogen
Bloods
Ultrasound
Invasive tests such as chronic villus sampling
Suggest some investigations that can be postnatally to find the damage done by a teratogen
looking for hip stability, issues with fingers and toes, hearing
From what tissue does the respiratory system develop ?
The endoderm
Describe the endoderm
It gives rise to the primitive tube which has a hindgut, a midgut and a foregut.
Which part of the endoderm does the respiratory system develop from ?
The foregut
Describe the development of the respiratory system
The trachea and lung buds grow out from the ventral wall of the primitive foregut and form the lung bud
The foregut will become the oesophagus and the trachea will remain in front of the oesophagus
How does the oesophagus and lung bud separate ?
The oesophagotracheal septum develops.
What does the lung tissue develop from ?
The mesoderm
How does the pleura of the lungs form ?
The splanchnic mesoderm is pushed towards the somatic mesoderm so that they become completely surrounded by both layers.
What is the visceral pleura from ?
The splanchnic mesoderm
What is the parietal pleura from ?
The somatic layer of the mesoderm
Is the pleural cavity complete ?
No because the pleura is still continuous with the heart and the abdomen (peritoneal cavity)
What happens to end this continuation ?
A pericardioperitoneal canal
A lateral plate of somatic mesoderm grows and separates the lungs and heart. This is called the pleuropericardial fold and will becomes the pericardium of the heart.
What is the Pseudoglandual stage ?
7-17 weeks where the lung structures develop except the respiring parts
What are the names of the stages ?
Embryonic Pseudoglandual Canalicular Saccular Alveolar
What is the canalicular stage ?
17-27 weeks where the formation of the respiratory parts comes i.e. alveolar ducts from and the epithelium starts to differentiate into type 1 and type 11 pneumocytes
What is the saccular stage ?
27-40 weeks where there is formation of alveolar sacs, primitive alveoli and surfactant and gas exchange begins
What is the alveolar stage ?
32 weeks to 8 years where there is growth of alveoli and alveolar sacs
What are the four things which come together to create the diaphragm ?
Septum transversum
Pleuroperitoneal folds
Skeletal muscle
Dorsal mesentery
How does the septum transversum create the diaphragm ?
Forms the central tendon
How does the pleuroperitoneal folds create the diaphragm?
They are somatic mesodermal folds which grown in from the sides and fuse with the transversum
How does the skeletal muscles form the diaphragm ?
it grows in a covers the pleuroperitoneal folds and forms the muscular part of the diaphragm
How does the dorsal mesentery help create the diaphragm ?
Attaches the oesophagus to the thoracic wall. It is then covered in skeletal muscle to form the diaphragmatic crura.
Name some congenital lung conditions ?
- Tracheoesophageal fistula and oesophageal atresia
- Neonatal respiratory distress syndrome
- Lung agenesis
- Congenital abnormalities of diaphragm
Describe Tracheoesophageal fistula and oesophageal atresia
If that oesophagotracheal septum doesn’t develop properly then the child will have a tracheosophageal fistula (TOF) or a Oesophageal Atresia. A fistula is an abnormal passage between 2 epithelialized tubes or surfaces. TOF is a common congenital abnormality. Atresia is a condition in which an orifice or passage in the body is closed or absent.
Describe Neonatal respiratory distress syndrome
Neonatal respiratory distress syndrome (Hyaline membrane disease). It is caused by surfactant deficiency and therefore partial collapse of alveoli. Debris consisting of blood elements accumulate which have a glassy (hyaline) appearance. It affects 2% of neonates and makes up 30% of neuronal disease.
Describe Lung agenesis
Lung agenesis. This is failure of lung bus to develop/branch (this will have happened on one side otherwise I’m guessing child wouldn’t have been born) it can also happen because there is insufficient mesoderm to allow formation or the presents or teratogens.
Describe Congenital abnormalities of diaphragm
Congenital abnormalities of diaphragm development occur as a result of two major defects. 1. the failure of the diaphragm to completely close during development, this is called a hernias. 2. the pulmonary hypoplasia. Hernia is a general term to describe a profusion of an organ through the structure or muscle that usually contains it.
