Embryology of the Nervous System

Question 1

Which layer does the nervous system form from?

Answer 1

Ectoderm

Question 2

At what point does the cranial neuropore close?

Answer 2

18-20 somite stage (25 days)

Question 3

At what point does the caudal neuropore close?

Answer 3

27 days

Question 4

At what point is the neural tube closure complete?

Answer 4

At the end of the 4th week

Question 5

What is the consequence of the neural tube failing to close?

Answer 5

Neural tube defects: anencephaly, encephalocoele and spina bifida

Question 6

What happens in exencephaly/anencephaly?

Answer 6

The anterior neuropore fails to close: skulls fail to form, brain tissue degenerates and it is incompatible with life

Question 7

What is craniorachichisis?

Answer 7

Failure of the neural tube closure along the entire neuroaxis

Question 8

What happens in encephalocoele?

Answer 8

Herniation of cerebral tissue through a defect in the skull: failure in closure of the rostral neural tube. Variable degree of neurological defects

Question 9

What is the most common site of encephalocoele?

Answer 9

Occipital

Question 10

What are the three primary brain vesicles?

Answer 10

Prosencephalon, mesencephalon and rhomboencephalon

Question 11

What is formed by the prosencephalon?

Answer 11

Forebrain

Question 12

What is formed by the mesencephalon?

Answer 12

Midbrain

Question 13

What is formed by the rhomboencephalon?

Answer 13

Hindbrain

Question 14

Which secondary brain vesicles are formed from the prosencephalon?

Answer 14

Telencephalon, diencephalon and mesencephalon

Question 15

Which secondary brain vesicles are formed from the rhomboencephalon?

Answer 15

Metencephalon and myencephalon

Question 16

Where is the cephalic flexure found and when does it develop?

Answer 16

Between the midbrain and hindbrain - end of 3rd week

Question 17

Where is the cervical flexure found and when does it develop?

Answer 17

Between hindbrain and spinal cord - end of 4th week

Question 18

Where is the pontine flexure found and when does it develop?

Answer 18

Hindbrain between metencephalon and myencephalon - 5th week

Question 19

What structures are formed from the diencephalon?

Answer 19

Thalamus, hypothalamus, pituitary gland and pineal gland

Question 20

What structures are formed from the telencephalon?

Answer 20

Cerebral hemispheres, hippocampus and basal ganglia

Question 21

What structures are formed by the mesencephalon?

Answer 21

Superior and inferior colliculi

Question 22

What structures are formed from the rhombencephalon?

Answer 22

Metencephalon - cerebellum and pons

Myencephalon - medulla

Question 23

At what point in development does CSF begin to form and where is it produced?

Answer 23

5th week - choroid plexus

Question 24

Where does the CSF drain?

Answer 24

Subarachnoid space via the 4th ventricle

Question 25

What is hydrocephalus?

Answer 25

Accumulation of CSF which results in an enlarged brain and cranium

Question 26

What are the causes of hydrocephalus?

Answer 26

Genetic, prenatal viral infection, intraventricular haemorrhage and spina bifida cystica

Question 27

What type of cells line the neural tube?

Answer 27

Initially it is a single layer of neuroepithelial cells then it is pseudostratified epithelium

Question 28

At what level does a newborns spinal cord end?

Answer 28

L2/3

Question 29

Where are spinal nerves found in newborns and what happens to them?

Answer 29

Found at the level of origin - become elongated forming cauda equina

Question 30

What is the function of cortical folding?

Answer 30

Space saving and brings together brain regions allowing optimisation of brain wiring and functional organisation

Question 31

What is Lissencephaly and what is it caused by?

Answer 31

Failure of the gyri and sulci to develop - caused by defective neuronal development

Question 32

What are the consequences of lissencephaly?

Answer 32

Severe mental impairment, failure to thrive, seizures and abnormal muscle gyri

Question 33

What is polymicrogyria and what does it cause?

Answer 33

Excessive number of small gyri - varying neurological problems (e.g. mental retardation, seizures and motor deficits)

Question 34

What are the causes of intellectual impairment with no obvious gross brain defects?

Answer 34

Genetic, radiation, infectious agents (rubella. toxiplasmosis etc.), birth trauma and postnatal insults (head injury, infecions etc.) and alcohol abuse