Topic 9 Embryonic Development

Question 1

Give one structure that develops from each of the pharyngeal arches. When do they start forming?

Answer 1

I: Maxilla

II: Upper Part of hyoid bone

III: Lower Part of hyoid bone

IV: Thyroid cartilage

VI: Cricoid cartilage

All but I involved with larynx formation

Question 2

What are the primary brain vesicles of a developing embryo (include both names)?

Answer 2

Proencephalon (forebrain)

Mesencephalon (midbrain)

Rhombencephalon (hindbrain)

Question 3

The hyoid bone derives from pharyngeal arches II and III.

TRUE or FALSE

Answer 3

TRUE

Question 4

What is the cause of neural tube defects? Give an example of a neural tube defect and some symptoms.

Answer 4

The neural tube should be completely closed by about 30 days after fertilisation. If the neural tube is not completely closed by this time, can lead to congenital defects.

Eg. Spina Bifida

• Incomplete closure of one or more sections of spinal cord
• Hydrocephalus (water head - accumulation of CSF in brain)
• Malformation of spine

Question 5

What causes ankyloglossia?

Answer 5

• also called ‘tongue-tie’
• results from failure of the lingual frenulum to degenerate with development (remains attached to entire interior tongue)
• can restrict tongue mobiity and affect articulation.

Question 6

Which primary brain vesicle gives rise to the mesencephalon?

Answer 6

Mesencephalon

Question 7

What is the likely consequence of a developmental defect in the fourth pharyngeal arch?

A. Malformed hyoid bone

B. Small jaw

C. Underdeveloped thyroid cartilage

D. Malformed cheekbones

Answer 7

C. Underdeveloped thyroid cartilage​

Question 8

What two important structures can be found in an adult diencephalon, and which primary vesicle did it arise from?

Answer 8

Thalamus (traffic control to relevent area of cortext)

Hypothalamus (endocrine system - maintains homeostasis)

Formed from proencephalon (primary) and diencephalon (secondary)

Question 9

What causes cleft palate?

Answer 9

• Incomplete midline fusion of the hard palate during development
• Results in a direct opening between the oral and nasal cavities - can affect chewing, swallowing and articulation

Question 10

Name one structures that might be affected by abnormal development of pharyngeal arch III.

Answer 10

• lower part of hyoid bone

Question 11

Which pharyngeal arch gives rise to the cricoid cartilage?

Answer 11

Pharyngeal arch V/VI

Question 12

Which secondary brain vesicles end up forming the adult brain stem?

Answer 12

​Mesencephalon

Metencephalon

Myencephalon

Question 13

What are the secondary brain vesicles of a developing embryo?

Answer 13

Telencephalon

Diencephalon

Mesencephalon

Metencephalon

Myencephalon

Question 14

Which embryonic structure eventually becomes the brain and spinal cord?

Answer 14

Neural tube

Question 15

Name two structures that might be affected by abnormal development of pharyngeal arch IV.

Answer 15

• thyroid cartilage

Question 16

What is the frontonasal prominance?

Answer 16

A region that forms just under the forebrain in a developing embryo that eventually forms the nose and forehead.

Question 17

What causes cleft lip?

Answer 17

Failure of the lip and nasal tissue to fuse properly during embryonic development.

Question 18

Which secondary brain vesicle is labelled with the letter G?

Answer 18

Diencephalon

Question 19

What are pharyngeal (brachial) arches?

Answer 19

• Tissue bulges on the lateral aspects of the embryonic head and neck
• Contain tissues that develop into bones, cartilages, muscles nerves and blood vessels
• Develop around Week 4