Flashcards in Embryology Deck (24)
Where does fertilisation happen?
Ampulla of the uterine tubes
What are the key events in the first 7 days post fertilisation?
D1: Fertilised and becomes a zygote
D3: Becomes a morula (ball of cells)
D4: Enters uterus as a blastocyst
D7: Trophoblast (edge) cells implant into uterus and surround inner cell mass
What does the inner cell mass split into between wk 1-2?
Epiblast (becomes amniotic fluid)
Hypoblast (becomes yolk sac)
Between these is the embryonic disc which becomes the embryo
What key event happens 3 weeks into development?
Primative streak forms (from caudal to rostral end). The three germ layers form
What is the notochord from and what does it do?
Notochord forms from the mesoderm, it secretes proteins to differentiate ectoderm tissue:
No inhibition from notocord proteins: Cell becomes skin
Inhbition from notochord proteins: Cell becomes neural
What is the role of sonic hedgehog protein? Where is it produced from?
Secreted from mesoderm, cells which receive:
High conc: Become specialised glial cells
Med conc: Become motor neurons
Low conc: Become interneurons
Sonic hedgehog binds to a receptor on neural cells coded for by which gene?
Where are neurons produced in the embryo?
Produced in central canal of neural tube and travel from ventricular (inner) zone to the marginal (outer zone) where they grow and migrate to the brain
How do cells move in the primiative streak?
Migrate along glial fibres from caudal (tail) end to rostral (head) end
How can cocaine/ alcohol/ radiation affect embryo growth?
Prevent nerve cell migration = misplacement of cells = retardation/ epilepsy
By what process do axons grow?
Growth cones (neural cell outgrowings) search for signal molecules and causes advancement/ turning/ pausing
How does the brain remove improper connections?
Initially a child has double the number of neurons and adult has. Sculpting action removes improper or redundant connections as nerves need constant presence of trophic factors (nerve growth factor) to survive
Why is childhood critical to development?
Physical/ social deprevation = Less neurons made
Stimulation = More neurons made
Where does myelination take place?
From back of brain to front (so frontal lobe often not fully myelinated til 20's)
Where does the neural plate form from?
Ectodermal tissue just opposite the primitive streak
What is neurulation?
At D20 the edges of the neural plate begin to elevate, forming neural folds, the groove formed is the neural tube- this becomes the brain and spinal cord
When does the neural tube close?
Rostral (head) end: D25
Caudal (tail) end: D27
What are the three primary vesicles formed at 3wks?
From which brain regions does the cerebrum originate embryologically?
Proencephalon > telencephalon > cerebrum
The diencephalon consists of what and forms from which primary vesicle at 3wks?
Thalamus, hypothalamus, epithalamus
From proencephalon > diencephalon
Where does the midbrain (brainstem) originate embryologically?
What forms from the metencephalon?
Rhombencephalon > metencephalon > pons + cerebellum
Where does the medulla oblongata originate from embryologically?
Rhombencephalon > myelencephalon > medulla oblongata