Lec 34 Flashcards
(30 cards)
Formation of what defines all major body axes ?
Primitive streak
When the primitive streak forms in the caudal midline of the embryonic disc , this defines the ?
Cranial caudal axis
When the ps forms in the midline , this defines the ?
Medial lateral axis
At the time of the primitive streak formation, the future —— axis of the embryonic disc is roughly equivalent to its ectoderm - endoderm axis
dorsal - ventral
With body folding the —— axis becomes better defined
Dorsal - ventral
When the epiblast is viewed looking down at it from inside the amniotic cavity , what lies to the right of the primitive streak represents the —— of the embryo , and what lies to the left represents its —— .
Thus , formation of the primitive streak also defines the left - right axis
right side
left side
Before gatrulation the embryonic disc was —— symmetrical
Bilaterally
——— at the primitive node sweep the symmetry breaking molecule ( Nodal ) toward the — side of the embryo , where it stimulates a cascade of genes ( — genes ) on the left side through the activation of Pitx2 gene also on left side
Ciliary currents , left , 24
What is responsible for the position of the stomach, heart , spleen, and asymmetrical lobation of the lungs?
Pitx2 gene
What acts as a barrier to prevent signals from crossing over to the right side
Lefty1
The genes regulating right sided development are not well
Defined
abnormal sidedness occurs Once a person has
failure of establishment of normal left right asymmetry
A person with abnormal sidedness suffers from
1- Dextocardia
2- Situs inverse totalis ( 1 in 10,000 )
What is the formation of the brain and spinal cord?
Neurulation
The process by which the neural plate , neural folds and neural tube form
Neurulation
The dermal cells overlying the Notochordal process becomes —— to form the —— . ( day 17 )
The two edges of the —— come nearer to each other to fuse. ( day 19 )
The neural plate becomes —— along the midline to form the —— . ( day 20 )
conversion of neural groove to —— . ( day 21 )
thick , neural plate
neural fold
depressed , neural groove
neural tube
A cut through the embryo reveals the —— approach each other in the —— where they fuse
neural folds , midline
Fusion begins at —— and proceeds cranially and caudally forming the ——
cervical region , neural tube
until fusion is complete , The cranial and caudal ends of the —— are called the ———— .
neural tube , cranial & caudal neuropores
☆ the cranial neurpores closes on day —
☆ the caudal neuropore closes on day —
25 , 28
The lateral edges of the neural folds first begin to fuse in the —— region on day — then fusion proceeds in both directions, cranially and caudally
cervical , 22
The neuron folds — forming the portion of the —— that will be the — and the —— .
The caudal neuropore closed up about — days — the cranial neuropore
fuse , neuron tube , brain , spinal cord
2 , after
broader —— of the —— forms the — , and the narrow —— forms the —— .
cephalic portion , neural tube , brain , caudal portion , spinal cord
Neural tube defects NTDs result when ——— ? , these defects arise during ———?
neurulation fails to occur normally
weeks 3-4 of gestation
