EMBRYOLOGY - Central Nervous System

Question 1

What is the embryological origin of the central nervous system (CNS)?

Answer 1

Central nervous system (CNS) has an ectodermal origin

Question 2

What is neurulation?

Answer 2

Neurulation is the formation of the neural tube from the neural plate

Question 3

How is the neural plate formed?

Answer 3

Notochord stimulates the differentiation of the overlying ectoderm into the neuroectoderm which thickens to form the neural plate

Question 4

Describe how the neural plate forms the neural tube

Answer 4

The lateral edges of the neural plate fold to form neural folds which fuse to form the neural tube

Question 5

Which two regions are last to fuse during the closure of the neural tube?

Answer 5

Rostral neuropore
Caudal neuropore

Question 6

How are the neural crest cells formed?

Answer 6

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

Question 7

Which main structure do the neural crest cells give rise to?

Answer 7

Peripheral nervous system (PNS)

Question 8

Which structures are formed by the neural canal (centre of the neural tube) in adult life?

Answer 8

Central canal in the spinal cord and the ventricular system in the brain

Question 9

What are the three layers of the neural tube?

Answer 9

Germinal layer
Mantle layer
Marginal layer

Question 10

What is formed by the germinal layer of the neural tube in adult life?

Answer 10

Ependymal cells

Question 11

Which two cells types make up the mantle layer of the neural tube?

Answer 11

Immature neurones
Spongioblasts

Question 12

Which three cell types are derived from the spongioblast cells in the mantle layer of the neural tube?

Answer 12

Oligodendrocytes
Astrocytes
Microglia

Question 13

What is formed by the mantle layer of the neural tube in adult life?

Answer 13

Grey matter

Question 14

What is formed by the marginal layer of the neural tube in adult life?

Answer 14

White matter

Question 15

What are the three primary vesicles formed during brain development?

Answer 15

Prosencephalon
Mesencephalon
Rhombencephalon

Question 16

What are the five secondary vesicles formed during brain development?

Answer 16

Telencephalon
Diencephalon
Mesencephalon
Metencephalon
Myelencephalon

Question 17

What are neural tube defects?

Answer 17

Failure of complete closure of the neural tube

Question 18

What is the difference between open and closed neural tube defects?

Answer 18

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

Question 19

List four examples of neural tube defects

Answer 19

Anencephaly (cerebral aplasia)
Meningocele
Meningoencephalocele
Meningomyelocele

Question 20

What is Anencephaly (cerebral aplasia)?

Answer 20

Absent cerebral hemispheres caused by failure of telencephalon vesicle to develop

Question 21

What is Meningocele?

Answer 21

Protrusion of the meninges covered by skin through the cranium or the vertebral column

Question 22

What is Meningoencephalocele?

Answer 22

Protrusion of the meninges and brain tissue through the cranium, covered by skin

Question 23

What is the name of the hole in the skull that a meningocele or meningoencephalocele?

Answer 23

Cranioschisis

Question 24

What is Meningomyelocele?

Answer 24

Protrusion of the meninges and spinal cord through a spina bifida or rachischisis

Question 25

What is the difference between spina bifida and rachischisis?

Answer 25

Spina bifida is the failure of closure of one vertebrae whereas rachischisis is the failure of closure of several vertebrae

Question 26

Which region of the spine is most prone to Meningomyelocele?

Answer 26

Sacrocaudal region

Question 27

What are the three clinical signs of Meningomyelocele in the sacrocaudal region of the spine?

Answer 27

Urinary and/or faecal incontinence
Paraphimosis
Weak gait in hindlimbs

Question 28

Which teratogenic antifungal drug can cause Meningocele, Meningoencephalocele or Meningomyelocele in cats?

Answer 28

Griseofulvin

Question 29

List two examples of neural migration disorders

Answer 29

Lissencephaly
Polymicrogyria

Question 30

What is Lissencephaly?

Answer 30

Absence of gyri and sulci in the cerebral cortex (smooth brain) caused by slowed of failed neural migration

Question 31

What is Polymicrogyria?

Answer 31

Excessive gyri and sulci in the cerebral cortex caused by abnormal neural migration

Question 32

What are the three clinical signs of Lissencephaly and Polymicrogyria?

Answer 32

Blindness
Cognitive dysfunction
Seizures

Question 33

What is Hydranencephaly?

Answer 33

Loss of one or both of the cerebral hemispheres which are replaced by cavities of cerebrospinal fluid (CSF)

Question 34

What is Congenital Hydrocephalus?

Answer 34

Accumulation of cerebrospinal fluid (CSF) in the brain cavities caused by obstruction of the flow or absorption of the cerebrospinal fluid (CSF)

Question 35

What is the main clinical sign of congenital hydrocephalus?

Answer 35

Enlarged, dome-shaped head

Question 36

What is the main clinical sign of Cerebellar Aplasia?

Answer 36

Unable to stand after birth

Question 37

What is the main clinical sign of Cerebellar Hypoplasia?

Answer 37

Cerebellar ataxia

Question 38

Which breeds of dog are most susceptible to Chiari-like malformation?

Answer 38

Cavalier King Charles Spaniels
Brachiocephalic breeds

Question 39

What are the two main clinical signs of Chiari-like malformation?

Answer 39

Spinal pain
Neck scratching