Embryology Flashcards

1
Q

How many branchial arches are there + how many branchial arches does the neck develop from

A

6

5

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2
Q

What is mesenchyme

A

Embryonic connective tissue

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3
Q

What 2 regions of the embryo is there no mesoderm and why is this

A

Head and tail region - to form a hole for the mouth and anus

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4
Q

Which germ layer are the somites derived from + what do they help develop

A

Paraxial mesoderm

Cranial skeleton

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5
Q

Where do branchial arches develop around

A

Around the future mouth and pharynx

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6
Q

What week gestation do pre-branchial arches form

A

4

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7
Q

What does each branchial arch contain (3)

A

A skeletal element
Artery
Nerve

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8
Q

Why does the neck only develop from 5 branchial arches when there’s 6 in total

A

Arch 5 disappears

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9
Q

How many mesenchymal processes does the face develop from + name them

A

5:
1 frontonasal process
2 maxillary processes
2 mandibular processes

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10
Q

1st branchial arch innervated by what nerve

A

CN V3

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11
Q

2nd branchial arch innervated by what nerve

A

Facial nerve

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12
Q

3rd branchial arch innervated by what nerve

A

Glossopharyngeal nerve

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13
Q

4th branchial arch innervated by what nerve

A

Superior laryngeal nerve (branch of vagus)

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14
Q

6th branchial arch innervated by what nerve

A

Recurrent laryngeal nerve (branch of vagus)

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15
Q

Cranial vault (neurocranium) formed of flat bones which is formed by what type of ossification

A

Membranous

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16
Q

Base of skull formed of irregular bones which is formed by what type of ossification

A

Endochondral

17
Q

Viscerocranium (Facial skeleton) formed by what embryologically

A

Mesenchyme of branchial arches and sensory capsules

18
Q

Name a congenital facial defect

A

Cleft lip + palate

19
Q

What causes cleft lip

A

failure of fusion of the maxillary and medial nasal (frontonasal) processes (failure of formation primary palate)

20
Q

What causes cleft palate

A

failure of fusion of the palatine shelves (failure of formation of the secondary palate)

21
Q

Name a congenital abnormality of the head

A

Craniosynotosis

22
Q

What is craniosynotosis

A

Skull bones fused too early

23
Q

Which branchial arch is affected in treacher collins syndrome

A

1st branchial arch abnormality

24
Q

Some cells at the crest of the neural fold (before fully becoming a closed tube) in the ectoderm midline separate to form what kind of cells

A

Neural crest cells - mix with mesoderm in the head and neck region of embryo

25
Q

What 3 tissues make up branchial arches

A

Ectoderm
Mesoderm + neural crest cells
Endoderm

26
Q

What branchial arch do the maxillary processes arise from

A

1st branchial arch mesoderm

27
Q

What branchial arch do the mandibular processes arise from

A

1st branchial arch mesoderm

28
Q

What tissue do the frontonasal processes arise from

A

Mesenchyme superior to future mouth

29
Q

Describe how the face forms from the mandibular & frontonasal (medial nasal) processes (4)

A
  1. The 2 mandibular processes fuse in the midline
  2. Ectoderm thickens to form 2 NASAL PLACODES which push inwards (invaginates) to form NOSTRILS, thus separating the frontonasal process –> 2 LATERAL NASAL PROCESSES
  3. The nasal placodes migrate downwards and fuse, forming a MEDIAL NASAL PROCESS in the midline
  4. The medial nasal process further grows downwards and laterally to form a process called the PHILTRUM
30
Q

Describe the formation of the palate (3)

A
  1. Medial nasal process grows downwards and forms the philtrum –> PRIMARY PALATE
  2. From the maxillary processes, 2 palatine shelves grow inwards
  3. The palatine shelves meet in the midline to form the SECONDARY PALATE

ORAL CAVITY AND NASAL CAVITY ARE NOW SEPARATE

31
Q

Cleft lip is due to failure of fusion of what processes

A

Maxillary and medial nasal (frontonasal) processes

32
Q

Cleft palate is due to failure of fusion of what processes

A

Palatine shelves (they fuse to form the secondary palate)

33
Q

Structures arising from 1st branchial arch (4)

A

Anterior belly of digastric
Muscles of mastication -
Malleus + incus (of ossicle)
Anterior 2/3 tongue

34
Q

Structures arising from 2nd branchial arch (4)

A

Muscles of facial expression
Posterior belly of digastric
Stapes
Suprahyoid muscles

35
Q

Structures arising from 3rd branchial arch (3)

A

Lower hyoid bone
Infrahyoid muscles
Posterior 1/3 tongue

36
Q

Structures arising from 4th branchial arch (2)

A

Thyroid cartilage

Larynx

37
Q

Structures arising from 6th branchial arch (1)

A

Cricoid cartilage