(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
