Lecture 2 -Anatomy of Brain Flashcards
Neurulation Steps (7):
1) Germ Disc Formation:
2) Notochord Formation
3) Neural Plate Formation
4) Growth and Bending
5)Neural Tube Formation
6) Neural Crest Formation
7)CNS and PNS Development
1) Germ Disc Formation:
At around day 14 of human embryo development, a structure called the trilaminar germ disc forms. It’s made up of three layers: ectoderm, mesoderm, and endoderm.
2)Notochord Formation
Some cells in the mesoderm migrate to the middle of the germ disc’s back, creating a structure that looks like a pencil. This is called the notochord or notochordal process.
3) Neural Plate Formation
The notochord has a special role. It signals the ectoderm cells just above it to become thicker and change into a structure called the neural plate.
4) Growth and Bending:
The neural plate’s ends start to grow upward and bend toward each other, like two hands coming together in a clap.
5) Neural Tube Formation
As the ends of the neural plate meet, they form a tube-like structure called the neural tube. This tube separates itself from the rest of the ectoderm.
6) Neural Crest Formation
At the same time, the ends of the neural plate also separate from the newly formed neural tube, creating another group of cells called the neural crest.
8) CNS and PNS Development
The neural tube goes on to become the precursor of most of the central nervous system (CNS), which includes the brain and spinal cord. The neural crest becomes the precursor of most of the peripheral nervous system (PNS).
Spinal Bifida
Neural tube does not fully seal itself (usually in the lower spine)
What is spina bifida meningocele?
Involves an opening in the spine where the meninges and cerebrospinal fluid (CSF) protrude, but the spinal cord remains inside and undamaged
What is spina bifida myelomeningocele?
The most severe form, where both the spinal cord and the meninges protrude through an opening in the spine. The exposed spinal cord may be damaged, leading to neurological deficits, and surgery is necessary for closure.
Spinal Bifida Oculta
Small opening in the vertebrae, typically without protrusion of the spinal cord, often with no noticeable symptoms.
Neurological Problems Associated with Bifida
1)Hydrocephalus (excess amount of CSF)
2) Chiari Malformation: The cerebellum, a part of the brain, gets pushed down through the base of the skull into the upper neck
What happens during the early differentiation of the central nervous system (CNS)? (By 4 weeks)
By 4 weeks of development, the neural tube bends at the anterior end and differentiates into the prosencephalon (forebrain), mesencephalon (midbrain), rhombencephalon (hindbrain), and the spinal cord.
What occurs around 6 weeks of CNS development?
Around 6 weeks, the brain’s divisions become more pronounced, the prosencephalon splits into the diencephalon and telencephalon, and the telencephalon starts to separate into two hemispheres along its dorsal midline.
