Embryology of the Skull and its contents

Question 1

What kind of cell type does the neurocranium form from?

Answer 1

forms from head mesoderm

Question 2

What kind of cell type does the viscerocranium form from?

Answer 2

branchial arch mesenchyme

Question 3

What are the two divisions of the neurocranium?

Answer 3

cartilaginous and membranous

Question 4

How does the cartilaginous neurocranium form?

Answer 4

intracartilaginous ossification

Question 5

How does the membranous neurocranium form?

Answer 5

intramembranous ossification

Question 6

What is craniosynostosis?

Answer 6

premature or abnormal ossification of sutures (deforms skull)

Question 7

What is encephalocele?

Answer 7

when the brain is forced to herniate out through deformed skull

Question 8

What are the symptoms of spina bifida occulta?

Answer 8

Often asymptomatic; tuft of hair on skin over underlying unfused vertebral arch

Question 9

What is spina bifida cystica?

Answer 9

a larger defect in closure, when there is a herniation through an unformed bony spinal arch

Question 10

What is spina bifida with myeloschisis?

Answer 10

the worst scenario - the spinal cord itself is split and open to the outside

Question 11

What are the 3 primary brain vesicles?

Answer 11

1. forebrain
2. midbrain
3. hindbrain

Question 12

What are the 3 brain flexures?

Answer 12

1. midbrain flexure (cephalic)
2. cervical flexure (between hindbrain and spinal cord)
3. pontine flexure (roof of hindbrain)

Question 13

What are the 5 secondary brain vesicles and what do they form from?

Answer 13

FOREBRAIN gives rise to telencephalon and diencephalon
MIDBRAIN gives rise to mesencephalon
HINDBRAIN gives rise to metencephalon and myelencephalon

Question 14

From what do each of the ventricles of the brain arise?

Answer 14

lateral ventricles: telencephalon
3rd ventricle: diencephalon
4th ventricle: myelencephalon
cerebral aqueduct: mesencephalon

Question 15

Where do the pons and cerebellum come from?

Answer 15

metencephalon

Question 16

What does the choroid plexus do?

Answer 16

secretes cerebral spinal fluid into ventricles and spinal canal

Question 17

What is the part of the brain that “makes us human”, and why?

Answer 17

telencephalon “endbrain”

forms cerebral hemispheres

Question 18

What is hydrocephalus?

Answer 18

CSF flow is blocked; ventricles enlarge; impairs brain development

Question 19

The DIencephalon has many DIverticula - name 6

Answer 19

thalamus
hypothalamus
optic nerves
retinas
pineal gland
infundibulum

Question 20

What 2 structures meet to form the pituitary? Which is anterior and which is posterior?

Answer 20

Rathke’s pouch (from the stomodeum) and the Infundibulum (diencephalon) MEET and form the pituitary…
Rathke’s pouch = adenohypophysis = anterior
Infundibulum = neurohypophysis = posterior

Question 21

What is cranium bifidum?

Answer 21

defect in formation of calvaria “split skull”

Question 22

What can happen when there is cranium bifidum?

Answer 22

MENINGOCELE: meninges herniate through skull defect

Question 23

What are some defects that happen when the rostral neuropore fails to close?

Answer 23

meroanencephaly, anencephaly: partial or complete failure of brain formation

exencephaly: some or all of brain forms outside skull
polyhydramnios: excessive amniotic fluid

Question 24

Why is polyhydramnios a red flag?

Answer 24

red flag for neural defects…means that fetus can’t control swallowing