Embryology 4 - The Oropharyngeal Apparatus Flashcards

1
Q

A core of mesenchyme covered externally by ectoderm and internally by endoderm

A

Pharyngeal Arch

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2
Q

What is the mesenchyme derived from in teh third week?

A

Mesoderm

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3
Q

During the fourth week, most of the mesenchyme is derived from _______ cells that migrate into the ________

A

Neural crest cells; pharyngeal arches

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4
Q

When the neural crest cells migrate into the arches, what does their differentiation into mesenchyme produce?

A

Maxillary and mandibular prominences

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5
Q

Components of a pharyngeal arch?

A
  • Artery
  • Cartilaginous rod
  • Muscular component
  • Sensory and motor nerves
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6
Q

Where does a pharyngeal arch artery arise from?

A

Truncus arteriosus from primordial heart

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7
Q

What does the pharyngeal arch cartilaginous rod form?

A

The skeleton of the arch

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8
Q

What does the muscular component of the pharyngeal arch differentiate into?

A

Muscles of the head and neck

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9
Q

Where are the sensory and motor nerves of the pharyngeal arches derived from?

A

Neuroectoderm of the primordial brain

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10
Q

The pharyngeal arches are the main formative elements of what structures?

A
  • face
  • nasal cavities
  • mouth
  • pharynx
  • larynx
  • neck
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11
Q

During the fifth week, what happens to the second pharyngeal arch? What is produced?

A
  • Second pharyngeal arch enlarges and overgrows the third and fourth
  • Forms the cervical sinus
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12
Q

What happens by the end of the seventh week?

A

Second and fourth arches disappear - gives head and neck smooth contour

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13
Q

What does the primordial pharynx join when it widens cranially and caudally?

A
  • Cranially = stomodeum
  • Caudally = esophagus
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14
Q

The pharyngeal endoderm lines the internal aspects of the pharyngeal arches and passes into the diverticula = ________

A

Pharyngeal pouches

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15
Q

How many pairs of pharyngeal pouches are there?

A

4 (the 5th is rudimentary or absent)

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16
Q

What separates the pharyngeal pouches from the pharyngeal grooves? How many layers?

A

Pharyngeal membrane = 2 layers (no mesoderm)

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17
Q

Where are the pharyngeal grooves located?

A

On the outside of the embryo

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18
Q

The first pharyngeal arch separates into what two prominences?

A

Maxillary and mandibular

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19
Q

What does the maxillary prominence give rise to?

A

Maxilla, zygomatic bone, part of vomer

20
Q

What does the mandibular prominence give rise to?

A

Mandible (and also forms the temporal bone)

21
Q

What do the second and third pharyngeal arches form?

A

The hyoid bone

22
Q

The first and second pharyngeal cartilages give rise to what?

A

Ossicles of middle ear and styloid process of temp bone

23
Q

The fourth and sixth pharyngeal arches give rise to what?

A

Laryngeal cartilage

24
Q

The third and fourth pharyngeal arches give rise to what?

A

The epiglottis

25
Which pharyngeal arch is rudimentary and eventually disappears?
5th
26
Muscles from first pharyngeal arch?
- Muscles of mastication - Muscles of middle ear
27
Muscles from second pharyngeal arch?
- Stapedius - Stylohyoid - Posterior belly of digastric - Auricular - Muscles of facial expression
28
Muscles from third pharyngeal arch?
- Stylopharyngeus
29
Muscles from fourth pharyngeal arch?
- Cricothyroid - Levator veli palatini - Constrictors of pharynx
30
Muscles from sixth pharyngeal arch?
- Intrinsic muscles of the larynx
31
First arch nerve?
Trigeminal nerve (not V1)
32
Second arch nerve?
Facial nerve
33
Third arch nerve?
Glossopharyngeal nerve
34
Fourth arch nerve?
Superior laryngeal (vagus nerve)
35
Sixth arch nerve?
Recurrent laryngeal (vagus nerve)
36
What does the first pharyngeal pouch expand into?
Tubotympanic recess (responsible for hearing)
37
When the tubotympanic recess contacts the first pharyngeal groove, what forms?
Tympanic membrane (eardrum)
38
What does the cavity of the tubotympanic recess become?
Tympanic cavity and mastoid antrum
39
The connection of the tubotympanic recess with the pharynx elongates and forms the __________
pharyngotympanic tube (eustachian tube)
40
What does the second pharyngeal pouch eventually give rise to?
Palatine tonsils
41
What does the third pharyngeal pouch develop into?
- Inferior part of parathyroid glands (dorsal part) - A thymus (ventral part)
42
What does the fourth pharyngeal pouch develop into?
Superior part of the parathyroid gland
43
First endocrine gland to develop in the embryo?
Thyroid gland
44
When does the thyroid gland begin to form? From what?
24 days post-fertilization from thickening in floor of primordial pharynx
45
For a short tie, what is the thyroid gland connected to the tongue by?
Thyroglossal duct
46
When is the thyroid gland usually located at its final site in the neck?
By week 7