Respiratory System and Body Cavity Flashcards
How many body cavities are created after embryonic folding?
1
Where does the endodermal gut tube form?
In the centre (surrounded by visceral mesoderm)
What is the lining of the respiratory tube?
Derivative of endoderm
After how many does is the gut tube formed?
26
What is the gut tube in communication with?
Cavity of respiratory diverticulum
How does the gut tube and respiratory diverticulum separate?
There are pinch points at the junction between respiratory and oesophags which fuse and separate
What are the swellings called?
Laryngeal swellings
What does the foregut get split into?
Trachea and oesophagus
As the bronchial tree grows, what does it carry with it?
Layer of mesoderm
What is the lining of the bronchial tree?
Endoderm
How many lobes does the right lung bud have?
3
How many lobes does the left lung bud have?
2
What is a fistula?
Abnormal communication between 2 spaces
What is a blind end?
When there is no connection to the trachea (oesophageal atresia)
Describe the maturation of lungs in the embryonic period (26 days - 6 weeks)
Respiratory diverticulum forms and initial segments arise
Describe the maturation of lungs in the pseudoglandular period (6 - 16 weeks)
14 generations of branching occurs and terminal bronchioles arise
Describe the maturation of lungs in the canalicular stage (16 - 28 weeks)
Terminal bronchioles give rise to 2-3 respiratory bronchioles which branch into 3-6 alveolar bronchioles
Describe the maturation of lungs in the saccular stage (28 - 36 weeks)
Terminal sacs are formed and capillaries establish close contact with alveoli
What are the airways lined with?
Endodermal lining (tall columnar cells)
As alveoli develop, the cells lining the respiratory cells differentiate into what and why?
Squamous cells to minimise distance for oxygen and CO2 to diffuse across
What cells form the blood-air barrier?
Squamous cells (type 1) and some cuboidal cells (type 2)
What do type 2 cells do?
Produce surfactant which refuces surface tension
Where does the septum transversum initially start off?
Very head end (cranial) of embryo
What is located cranially to the heart tube?
Solid wedge of mesoderm
What separates the thorax and abdomen?
Septum transversum (but does not reach posterior body wall)
What are pericardio peritoneal canals?
Connecting space around the heart to the space around the peritoneal
As the septum transversum migrates towards thorax, what does it take with it?
Phrenic nerve (C3,4,5)
What organ forms in the septum transversum?
Liver
How do the pericardio peritoneal canals close?
Outgrowths from posterior body wall (pleuroperitoneal fold) grows medially and anteriorly before fusing with septum transversum and mesoderm
Where does the musculature for the diaphragm come from?
Septum transversum (innervated by phrenic nerve); ingrowth of body wall (local innervation)
What is a hernia?
Something that buldges from one place into another
What membrane is more likely to obtain a congenital diaphragmatic hernia?
Left pleuroperitoneal membrane (complete loss or thin membrane)
What part of the thorax develops with the lungs?
Left and right pleural cavity
What do the left and right pleural cavities contribute?
Cartilge and muscle to the lungs; covering layer of pleura
What name is given to the growth that divides the body cavity into the heart (anterior) and lungs (posterior)
Transverse growth
Describe what happens when the pleuroperitoneal folds migrate anteriorly
They pull a margin of the pleura cavirt posteriorly to surround the lungs
