EMBRYOLOGY - Central Nervous System Flashcards
What is the embryological origin of the central nervous system (CNS)?
Central nervous system (CNS) has an ectodermal origin
What is neurulation?
Neurulation is the formation of the neural tube from the neural plate
How is the neural plate formed?
Notochord stimulates the differentiation of the overlying ectoderm into the neuroectoderm which thickens to form the neural plate
Describe how the neural plate forms the neural tube
The lateral edges of the neural plate fold to form neural folds which fuse to form the neural tube
Which two regions are last to fuse during the closure of the neural tube?
Rostral neuropore
Caudal neuropore
How are the neural crest cells formed?
After closure of the neural tube, cells from the neural folds separate from the overlying ectoderm and form a cluster of cells known as the neural crest cells
Which main structure do the neural crest cells give rise to?
Peripheral nervous system (PNS)
Which structures are formed by the neural canal (centre of the neural tube) in adult life?
Central canal in the spinal cord and the ventricular system in the brain
What are the three layers of the neural tube?
Germinal layer
Mantle layer
Marginal layer
What is formed by the germinal layer of the neural tube in adult life?
Ependymal cells
Which two cells types make up the mantle layer of the neural tube?
Immature neurones
Spongioblasts
Which three cell types are derived from the spongioblast cells in the mantle layer of the neural tube?
Oligodendrocytes
Astrocytes
Microglia
What is formed by the mantle layer of the neural tube in adult life?
Grey matter
What is formed by the marginal layer of the neural tube in adult life?
White matter
What are the three primary vesicles formed during brain development?
Prosencephalon
Mesencephalon
Rhombencephalon
What are the five secondary vesicles formed during brain development?
Telencephalon
Diencephalon
Mesencephalon
Metencephalon
Myelencephalon
What are neural tube defects?
Failure of complete closure of the neural tube
What is the difference between open and closed neural tube defects?
Open neural tube defects have an opening of the skin that exposes the neural tissue and has leaking cerebrospinal fluid (CSF) whereas closed neural tube defects have no visible opening of the skin
List four examples of neural tube defects
Anencephaly (cerebral aplasia)
Meningocele
Meningoencephalocele
Meningomyelocele
What is Anencephaly (cerebral aplasia)?
Absent cerebral hemispheres caused by failure of telencephalon vesicle to develop
What is Meningocele?
Protrusion of the meninges covered by skin through the cranium or the vertebral column
What is Meningoencephalocele?
Protrusion of the meninges and brain tissue through the cranium, covered by skin
What is the name of the hole in the skull that a meningocele or meningoencephalocele?
Cranioschisis
What is Meningomyelocele?
Protrusion of the meninges and spinal cord through a spina bifida or rachischisis
What is the difference between spina bifida and rachischisis?
Spina bifida is the failure of closure of one vertebrae whereas rachischisis is the failure of closure of several vertebrae
Which region of the spine is most prone to Meningomyelocele?
Sacrocaudal region
What are the three clinical signs of Meningomyelocele in the sacrocaudal region of the spine?
Urinary and/or faecal incontinence
Paraphimosis
Weak gait in hindlimbs
Which teratogenic antifungal drug can cause Meningocele, Meningoencephalocele or Meningomyelocele in cats?
Griseofulvin
List two examples of neural migration disorders
Lissencephaly
Polymicrogyria
What is Lissencephaly?
Absence of gyri and sulci in the cerebral cortex (smooth brain) caused by slowed of failed neural migration
What is Polymicrogyria?
Excessive gyri and sulci in the cerebral cortex caused by abnormal neural migration
What are the three clinical signs of Lissencephaly and Polymicrogyria?
Blindness
Cognitive dysfunction
Seizures
What is Hydranencephaly?
Loss of one or both of the cerebral hemispheres which are replaced by cavities of cerebrospinal fluid (CSF)
What is Congenital Hydrocephalus?
Accumulation of cerebrospinal fluid (CSF) in the brain cavities caused by obstruction of the flow or absorption of the cerebrospinal fluid (CSF)
What is the main clinical sign of congenital hydrocephalus?
Enlarged, dome-shaped head
What is the main clinical sign of Cerebellar Aplasia?
Unable to stand after birth
What is the main clinical sign of Cerebellar Hypoplasia?
Cerebellar ataxia
Which breeds of dog are most susceptible to Chiari-like malformation?
Cavalier King Charles Spaniels
Brachiocephalic breeds
What are the two main clinical signs of Chiari-like malformation?
Spinal pain
Neck scratching
