development of the respiratory system Flashcards
when does implantation occur?
what are the 2 layers that form and from where?
- implantation occurs by days 7/9
- two layers of cells form from the inner cell mass - epiblast and hypoblast (bi-laminar disc)
describe the process of gastrulation?
where do all 3 layers arise from?
formation of the 3 germ layers
- all 3 layers arise from the epiblast via gastrulation that starts on day 17
- ectoderm, endoderm and mesoderm
what are the 3 main things that the ectoderm gives rise to?
- surface ectoderm (skin, tooth enamel)
- neural tube (CNS)
- neural crest (cranial and sensory ganglia)
what 3 things will mesoderm give rise to?
1) paraxial mesoderm (somites)
2) intermediate mesoderm (urogenital system)
3) lateral plate mesoderm (smooth muscle/connective tissue)
what will the endoderm give rise too?
gut tube
liver
pancreas
bladder
liver
describe the development of the body cavities and the role of mesoderm?
what does the parietal and visceral layers form?
what day does the happen?
- the mesoderm develops into 3 parts, paraxial, intermediate and lateral plate mesoderm.
- the lateral plate is divided into parietal (somatic) and visceral (splanchnic) by the development of the intra embryonic coelom.
- parietal layer forms the body walls
- visceral layers form connective tissue of respiratory system
- day 21
what does the intra embryonic coelom form?
the intra embryonic coelom will form a horse shoe shape around the developing head (this is entrapped during folding)
what are the 2 folding planes of the embryonic disc?
1) cranio-caudally
2) laterally
what does lateral folding cause?
what will this cavity be lined with?
- causes the closing of the body walls and the “entrapment” of intra-embryonic coelom into closed body cavity.
- the cavity will be lined by somatic lateral plate mesoderm, gut tube/mesentery by visceral lateral plate mesoderm.
What do the 2 layers of the lateral plate mesoderm cover/fuse with during lateral folding?
What movement occurs during lateral folding?
What ends up being pinched?
What lines the yolk sac?
What does this form?
What 3 things will the primitive yolk sack form during development?
During lateral folding, the parietal layer of lateral plate mesoderm fuses with the ectoderm to form the surface ectoderm
- The visceral layer of lateral plate mesoderm coves the endoderm
- During lateral folding, the lateral parts of the tri-laminar disk start to move anteriorly and medially towards each other, with them both eventually meeting and fusing In the midline
- This results in the primitive yolk sack being pinched (the yolk sac is lined by endoderm)
- This process forms a gut tube from the endoderm/yolk sac, and a connection between the gut tube and the yolk sac called the vitelline duct
During development, the primitive yolk sack will form:
1) The gut tube
2) GU systems
3) Respiratory systems
When is lateral folding complete?
What has happened to the surface ectoderm?
What will the CNS develop from?
What will the surface endoderm end up forming?
What does the parietal layer of lateral plate mesoderm form?
What does the intraembryonic coelom form?
Lateral folding is complete when the lateral foldings have met anteriorly in the midline and fused
The surface ectoderm has detached itself from the neural groove to become the neural tube
The CNS will develop from the neural tube
The surface ectoderm will eventually form the serous membranes e.g pericardium, pleura, peritoneum
The parietal layer of lateral plate mesoderm will fuse with the ectoderm to form the thoracic wall/body walls (and parietal pleura)
The intraembryonic coelom forms body cavities (thoracic, abdominal, pelvic) in between the visceral and parietal lateral plate mesoderm
The diagram has been takin from a transverse section above the vitelline duct, so it can’t be seen
What is the dorsal mesentery?
What does the dorsal mesentery do?
What is inside the dorsal mesentery?
The dorsal mesentery is part of the visceral lateral plate mesoderm that extends between the posterior abdominal wall and the gut tube
The dorsal mesentery serves as the root of gut tube, and suspends the gut tube through attachment to the posterior abdominal wall
In the dorsal mesentery, we have the arteries that supply various parts of the gut tube
What is the diverticulum?
When does is appear?
What does the diverticulum develop into?
When do the tracheo-oesophageal ridges/folds grow?
How do they move as they grow?
What does the respiratory diverticulum divide into?
How is the gut tube divided up?
What does the foregut form?
The diverticulum is a growth that appears anterior to the gut tube in the midline
- It appears at about week 4
- The diverticulum develops into part of the respiratory system
- The tracheo-oesophageal ridges/folds grow as the diverticulum grows
- As these ridges/folds grow, they start to move towards each other, with the aim being to separate the gut tube from the respiratory diverticulum (with the exception of the laryngeal orifice – comes later)
- The respiratory diverticulum will divide into 2 lung buds, which will grow, expand, and dilate to become part of the lungs
- The gut tube is divided into the foregut, midgut, and hindgut
- The foregut developed into the oesophagus, stomach, and part of the duodenum
what does the 2 plane folding cause?
the 2 lane folding will cause the development of the heart and septum transverse and the associated intra-embryonic coelom will move caudally
what happens to these primitive body cavities?
- the continuous primitive body cavities must under go partitioning.
- lung buds invaginate into pericardioperitoneal canals forming pleural cavities and pleuropericadial folds
