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Flashcards in H&N Deck (409)
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91

Structurally, what do the arches do?

Separate stomodeum from developing heart

92

Describe the structure of the branchial arches

Ectoderm - lines outside
Endoderm - lines inside
Mesenchymal tissue - core

Each has own nerve, blood, muscle and cartilage
Nerve and blood supply structures formed

93

Describe branchial grooves and pouches

Groove: ectodermal cleft between adjacent arches
Pouch: endodermal outpocketing from rostral foregut

94

What is the branchial membrane?

Site of contact between groove and pouch

95

Describe the mandibular arch

Forms the face
Has mandible and maxillary processes
Surrounds stomodeum

96

What is the stomodeum?

Depression between brain and pericardium in embryo which is primitive oral and nasal cavity
Formed by ectoderm, contacts endoderm at oropharyngeal membrane

97

What is the palatoglossal arch?

Physical remnant of branchial arches
Site of the oropharyngeal membrane separating oral cavity and pharynx

98

What are the cartilages of the mandibular arch?

Malleus
Incus
Ant. ligament of malleus
Sphenomandibular ligament

99

The stapes, styloid process, stylohyoid ligament and lesser horn and upper 1/2 body of hyoid bone are the cartilages of which arch?

2nd - hyoid arch

100

The 3rd arch has what cartilages,

Greater horn and lower 1/2 body of hyoid bone

101

The 4 and 6 arches have what cartilage?

Cartilages of pharynx

102

What are the derivatives of the pouch of each arch?

1. Tubotympanic recess - auditory tube, tympanic cavity
2. Lining (crypts of palatine tonsils)
3. Inf. parathyroid glands and thymus
4. Sup. parathyroid glands and C-cells (calcitonin)

103

The groove of which arch is the only one to form structures in adults and what does it form?

Mandibular
Groove - external auditory meatus
Membrane - tympanic membrane
Pouch - auditory tube

104

What does the face develop from? Name them

5 primordia
Frontonasal prominence - forehead, bridge of nose
2 maxillary prominences - cheeks, upper jaw
2 mandibular prominences - chin, lower jaw

105

What are nasal placodes?

Ectodermal thickenings on frontonasal prominence

106

How and when do the maxillary prominences grow?

Week 5
Ventrally (down)
Medically (toward midline)

107

How and when do nasal pits form?

Week 6
Ectoderm in centre of each nasal placode invaginates

108

What does the formation of nasal pits do?

Divides frontonasal prominence into lateral and medial nasal processes on each side of embryonic face

109

Describe the growth of the face in week 6

Medial nasal processes grow medially, fuse in middle forming intermaxillary process
Maxillary prominences grow, fuse with intermaxillary process forming philtrum and primary palate

110

What can happen if the medial nasal prominences don't fuse?

Lead to formation of bifid nose

111

How is the primary palate formed?

From internal swelling of intermaxillary process

112

How does the 2ndary palate form?

From 2 lateral palatine shelves

Develop as internal projection of maxillary prominences
Shelves grow down on either side of tongue from maxillary prominences while nasal septum grows down from base of skull
When tongue descends into throat palatine shelves rotate upward

113

Where do the palatine shelves fuse and with what?

At midline with nasal septum

114

How does a cleft lip occur?

Failure of maxillary prominences to fuse with intermaxillary process

115

How can a cleft lip be restored?

Using nasal retainer
Maintains shape of nasal passage after surgery, helps mound and approximate parts of cleft before surgery

116

What is a X-bite?

Abnormal occlusion in which mandibular teeth enclose the maxillary

117

How does a cleft palate occur?

Failure of palatine shelves to fuse OR
tongue too large or oral cavity too small for palatine shelves to rotate up and fuse

118

What is Meckel's cartilage?

Cartilage of 1st branchial arch associated with formation of mandible

119

Describe the growth of the mandible in week 6

Meckel's cartilage develops rod surrounded by fibrocellular capsule
2 cartilages don't meet, separated by symphysis
On lateral aspect of symphysis condensation of mesenchymal forms

120

What happens to the mandible in week 7?

Intramembranous ossification beings in mesenchyme, spreads ant. and post. to form bone
Ant. to midline of developing jaw, don't fuse forms mandibular symphysis