Histo Flashcards
The central nervous system (CNS) appears at
the beginning of the third week
The CNS starts as
the neural plate
the neural plate and it’s location
slipper shaped plate of thickened ectoderm located in the mid- dorsal region in front of the primitive node.
the neural plate lateral edges elevate to form
neural folds.
With further development, the neural
folds
continue to elevate,
other in the midline, and finally fuse, forming the neural tube.
How is the neural tube formed
When the lateral edges of neural plate elevate to neural folds which continue to elevate and then approach each other in the middle of the
Fusion of neural fold begins in
cervical region
Once fusion is initiated, the open ends of the neural tube form
the cranial and caudal neuropores
the cranial and caudal neuropores functions
communicate with the overlying amniotic cavity.
Closure of the cranial neuropore proceeds in what location
cranially from the initial closure site in the cervical region and from a site in the forebrain that forms later.
Final closure of the cranial neuropore occurs at …..closure of the caudal neuropore occurs approximately ……
the 18 to 20-somite stage (25th day);
3 days later (28th day).
cephalic end of the neural tube shows three dilations
(1) the prosencephalon, or forebrain;
(2) the mesencephalon, or midbrain; and
(3) the rhombencephalon, or hindbrain.
Simultaneously, the cephalic end of neural tube forms two flexures:
1) the cervical flexure
2) the cephalic flexure
the cervical flexure location
at the junction of the hindbrain and the
spinal cord
the cephalic flexure location
in the midbrain region.
When the embryo is 5 weeks old, the prosencephalon consists of two parts:
telencephalon
Diencephalon
telencephalon is formed by
a midportion and two lateral outpocketings: the primitive cerebral hemispheres
Diencephalon is characterised by
outgrowth of the optic vesicles, pituitary, epiphysis etc.
rhombencephalon (hind brain) also consists of two parts
metencephalon
myelencephalon
metencephalon later forms
pons and cerebellum
myelencephalon later forms
medulla oblangata.
The boundary between metencephalon and myelencephalon is marked by
pontine flexure.
What separates the mesencephalon from the rhombencephalon.
rhombencephalic isthmus (a deep furrow)
The lumen of the spinal cord, the central canal, is continuous with
that of the brain vesicles.
fourth ventricle
The cavity of the rhombencephalon
third ventricle,
Cavity of diencephalon
lateral ventricles.cavities of
cerebral hemispheres
What connects the third and fourth ventricles?
The lumen of the mesencephalon
When lumen of mesencephalon becomes very narrow and is then known as
aqueduct of Sylvius.
Each lateral ventricle communicates with the third ventricle through
interventricular foramina of Monro
