Embry 4 Flashcards

1
Q

what is pharyngeal arch?

A

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

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2
Q

what happens during the fourth week?

A

During the fourth week, most of the mesenchyme is derived from neural crest cells that migrate into the pharyngeal arches
- migration of neural crest cells into the arches and their differentiation into mesenchyme produces the maxillary and mandibular prominences

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3
Q

a pharyngeal arch contains

A

○ A pharyngeal arch artery that arises from the truncus arteriosus of the primordial heart and passes around the primordial pharynx to enter the dorsal aorta
○ A cartilaginous rod that forms the skeleton of the arch
○ A muscular component that differentiates into muscles in the head and neck
○ Sensory and motor nerves that supply the mucosa and muscles derived from the arch
§ derived from neuroectoderm of the primordial brain.

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4
Q

what is the main formative elements of the face, nasal cavities, mouth, larynx, pharynx, and neck?

A

the pharyngeal arches

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5
Q

During the fifth week, the second pharyngeal arch enlarges and overgrows the third and fourth arches, forming

A

cervical sinus

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6
Q

when does the second to fourth pharyngeal grooves and the cervical sinus disappear
, giving the neck a smooth contour

A

by the end of the 7th week

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7
Q

what widens cranially where it joins the stomodeum, and narrows caudally where it joins the esophagus

A

primordial pharynx

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8
Q

the primordial pharynx is derived from what?

A

the foregut

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9
Q

what is the pharyngeal pouches

A

The pharyngeal endoderm lines the internal aspects of the pharyngeal arches and passes into diverticula (outpouchings)

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10
Q

how many pairs of pharyngeal pouches are there?

A

four pairs of pharyngeal pouches; the fifth pair is rudimentary or absent

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11
Q

how is the pharyngeal membrane formed

A

endoderm of the pouches contacts the ectoderm of the pharyngeal grooves and together

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12
Q

what does the pharyngeal membrane separate?

A

separates the pharyngeal pouches from the pharyngeal grooves

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13
Q

when does the pharyngeal arches begin to develop?

A

early in the fourth week

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14
Q

when the pharyngeal arches begin to develop, what cells migrate into the ventral parts of the future head and neck regions?

A

neural crest cells

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15
Q

what are the first pair of pharyngeal arches turn into

A

the jaws

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16
Q

the first pharyngeal arch separates into 2 prominences, what are the prominences?

A

maxillary prominence and the mandibular prominence

17
Q

what does the maxillary prominence give rise to?

A

maxilla, zygomatic bone, and a portion of the vomer

18
Q

what does the mandibular prominence forms?

A

mandible and the squamous temporal bone

19
Q

what does the second and third pharyngeal arches form?

A

the hyoid bone

20
Q

what does the first and second pharyngeal cartilages give rise to?

A

the ossicles of the middle ear and the styloid process of the temporal bone

21
Q

what give rise to the laryngeal cartilage?

A

fourth and sixth pharyngeal arches

22
Q

what give rise to the epiglottis?

A

3rd and 4th pharyngeal arches

23
Q

what does the fifth pharyngeal arch form?

A

it is rudimentary - nothing is derived from it, and it disappears

24
Q

the first pharyngeal pouch expands into a ?

A

tubotympanic recess

25
Q

The expanded distal part of this recess contacts the first pharyngeal groove -> contributes to the formation of the ?

A

tympanic membrane (eardrum)

26
Q

the cavity of the tubotympanic recess becomes the ?

A

tympanic cavity and mastoid antrum

27
Q

The connection of the tubotympanic recess with the pharynx elongates and forms the ?

A

pharyngotympanic tube (auditory tube, Eustachian tube)

28
Q

the second pharyngeal pouch eventually gives rise to parts of the ?

A

palatine tonsils

29
Q

by the sixth week, the third pouch develops:

A

○ Into parathyroid glands – dorsal part (inferior pair)
○ Into a thymus – ventral part

30
Q

the fourth pouch also develops into ?

A

parathyroids - the superior pair

31
Q

what is the first endocrine gland to develop in the embryo?

A

thyroid gland

32
Q

For a short time, the thyroid gland is connected to the tongue by a narrow tube, what is it called?

A

thyroglossal duct

33
Q

the thyroid gland begins to form 24 days after fertilization from a median endodermal thickening in the floor of the primordial pharynx, this thickening forms a small outpouching called

A

thyroid primordium