(1.2) Embryology Flashcards
What is the forebrain also called? Describe its changes into its adult derivatives.
Primary Vesicle = Forebrain (Prosencephalon)
1) Secondary Vesicle -> Telencephalon & Diencephalon
2) Telencephalon -> Cerebral Hemispheres
2) Diencephalon -> Thylamus
What is the midbrain also called? Describe its changes into its adult derivatives.
Primary Vesicle = Midbrain (Mesencephalon)
1) Secondary Vesicle -> Mesencephalon
2) Mesencephalon -> Midbrain
What is the hindbrain also called? Describe its changes into its adult derivatives.
Primary Vesicle = Hindbrain (Rhombencephalon)
1) Secondary Vesicle -> Metencephalon & Myelencephalon
2) Metencephalon -> Pons & Cerebellum
2) Myelencephalon -> Medulla Oblongata
Describe the formation of Notochord and its role at developing the nervous system.
- Prenotochordal cells migrate from Primitive Pit -> Notochord -> Neurulation
- Neurulation: Ectoderm -> Neural Plate -> folds -> Neural Tube (at cranial region and proceeds both cranially and caudally)
What are Neuropores? What may be the consequences if its development fails (4)?
- Neurulation causing the Ectoderm becoming Neural Plate, which folds into Neural Tube, the blind openings become the Anterior & Posterior Neuropores
- They should close in normal development, if fails:
a) Anencephaly = cranial neuropore unclosed, lack of brain structure
b) Spina Bifida = caudal neuropore unclosed, two types:
b1) Spina Bifida Occulta = lack of fusion in vertebral arches
b2) Spina Bifida Cystica = cyst of meninges (meningocele) or cyst of neural tissues (meningomyelocele)
c) Rachischisis = flattened neural mass
What is Anencephaly?
Cranial Neuropore fails to close -> lack of brain structure
What is Spina Bifida Occulta?
Caudal Neuropore fails to close -> lack of fusion of the vertebral arches
What is Spina Bifida Cystica? Name the two types.
Caudal Neuropore fails to close -> cyst of:
- Meninges = Meningocele
- Neural tissues = Meningomyelocele
What is Rachischisis?
Flattened neural mass
How is neural tube defect detected? And how can it be prevented?
- Detected by raised Alpha-fetoprotein & by Ultra Sound Scan
- Prevented by Folate diet intake in 1st trimester
Due to rapid elongation of the neural tube at the brain, flexures are created. What are their names and where are they?
- Cephalic Flexure at Midbrain
- Cervical Flexure at Hindbrain and Spinal Cord Junction
What is the importance of landmark L3&L4?
- Landmark for Lumbar Puncture
- Spinal cord stops growing while Vertebral Column continues elongate, therefore nerve roots terminate at L2, and branch off as Cauda Equina
- Puncture at here prevents damaging Spinal Cord
The Spinal Cord enlarges at two positions, where are they and what do they form?
- At C4-T1 of vertebral column -> Brachial Plexus (nerve roots C5-T1)
- At T11-L1 of vertebral column -> Lumbosacral Plexus
a) Lumbar Plexus (nerve roots L1-L4)
b) Sacral Plexus (nerve roots L4-S4)
c) Pudenal Plexus (nerve roots S2-S4)
How and why is Lumbar Puncture performed at different position in babies from adults?
- Spinal cords stop elongating at 3 months, while the Vertebral column continues to grow.
- Spinal roots branch off at L2 vertebral column, an adult Lumbar Puncture between L3&L4
- However, in babies, Lumbar Puncture should be performed at a lower position, to avoid damaging the nerve roots
What is Cauda Equina?
The nerves that branch off after the Spinal Cord terminates at L2
From which secondary vesicle does the Medulla form from?
Myelencephalon
From which secondary vesicle does the Pons and Cerebellum form from?
Metencephalon
From which secondary vesicle does the Thalamus form from?
Diencephalon
From which secondary vesicle does the Cerebral Hemisphere form from?
Telencephalon
Describe the mature developments of the Neuroectoderm Tube.
- The lumen -> Ventricles
- 3 dilations of the tube at the cranial end -> Prosencephalon (Forebrain) + Mesencephalon (Midbrain) + Rhombencephalon (Hindbrain)
- The caudal tube -> Spinal Cord
