Gastrulation and Neurulation Flashcards
What is gastrulation?
Changing the bilaminar into the tri-laminar layers
What happens in week 3 of development?
A groove forms in the epiblast called the primitive streak with it ending with a primitive node at the centre
The anterior visceral endoderm of hypoblast defines the anterior side/ head
What function does the primitive pit give?
Gives the disc left and right
What occurs along the primitive streak and primitive node?
Epiblast cells start to differentiate and multiply and start to invade into the embryo
They then replace the hypoblast layer and turn it into the endoderm
They also invade outwards creating a third layer, the mesoderm
They also migrate anteriorly to from the notochord
Where does the notochord lie?
Beneath the epiblast
What occurs once the notochord has been formed?
The cells that lie anteriorly for the neural plate, made from columnar epithelium
At what day does a midline groove become apparent in the neural plate?
19
What happens in days 20-21?
Cells on neural plate thicken forming the neural fold and groove
What happens from day 22?
The edges of the neural tube close together and fuse
It is done this by actin filaments tightening and creating curvature
What are the two ends of the neural tube?
Rostral neuropore
Caudal neuropore
How long does it take for closure of the rostral neuropore?
25 days
How long does it take for closure of the caudal neuropore?
27 days
What happens if the rostral neuropore fails to close?
Anencephaly
What happens if the caudal neuropore fails to close?
Spina bifida
Where are neural crest cells found and what do they do?
They derive from the edges of the neural tube and undergo an epithelial to mesenchymal transition
What signal used to convert neural tissue into skin?
Bone morphogenic proteins
Chordin, noggin and follistatin
What cells develop from the neural crest cells?
Cranial nerve ganglia
Dorsal root ganglia
Autonomic ganglia
Adrenal Medulla
Schwann Cells
Peripheral glial
Smooth muscle of cardiac outflow
Odontoblasts
Craniofacial skeleton
Thyroid parafollicular cells
Melanocytes
What is Waardenburg’s Syndrome caused by?
PAX-3 gene deletion causing;
Pigment abnormalities
Deafness
Heterochromia of eyes
Telecanthus
What is Treacher Collins Syndrome caused by?
Defective protein called Treacle (TCOF 1 gene), failure of formation/apoptosis of neural crest cells
Symptoms of Treacher Collins Syndrom
Abnormal eye shape
Micrognathia
Conductive hearing loss
Underdeveloped zygoma
Malformed ears
What are the different flow of migrating mesoderm cells?
Paraxial
Intermediate
Lateral plate
What develops from the paraxial mesoderm?
Somites
Describe the formation of somites
Cells have a timer along the paraxial mesoderm
They go through cycles every 90mins defined by notch signalling clock
There is a wave of FGF signal that passes along the embryo
When the wave passes cells they are programmed to change into a part of a somite
If the wave passes early in the clock cycle they become the front end segment, if late the tail end
What does paraxial mesoderm give rise to?
Head and somites
Somites develop it sclerotome, myotome and dermatome
What does the intermediate mesoderm develop into?
Kidney and gonads
What does the lateral plate mesoderm develop into?
Splanchnic- covering of viscera
Cardiovascular system
Body walls
What is the midline mesoderm developing into?
Nucleus pulposus
What happens to the yolk sac?
The hypoblast and amniotic cavity close off the yolk sac and pinch it
This just leaves a thin tube called the endoderm
What day does the endoderm form?
17
What develops from the endoderm?
Gut tube
Lungs
Urinary bladder
What is the vitaline duct?
Connection between yolk sac and gut
What does the ectroderm develop into?
Epidermis
Lens and retina
Olfactory epithelium
Oral cavity epithelium
Sensory organs of ear
Glands- salivary, sweat and mammary
Adenohypophysis- anterior pituitary
