Pharyngeal Arches: Development of the Face and Neck Flashcards Preview

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Flashcards in Pharyngeal Arches: Development of the Face and Neck Deck (112):
1

What are the two general phases of pharyngeal arch development?

1. Formation of pharyngeal stem
2. Development of Pharyngeal derivatives

2

List some birth defects involving the pharyngeal region

1. 1st Arch Syndrome
-Treacher-Collins
-Pierre Robin
-DiGeorge Syndrome
2. Auricular Cysts and sinus
3. Branchial Cysts, Sinus, Fistula
4. Cervical Thymus
5. Accessory Thymus
6. Thyroid
-Thyroiglossal Duct
-Thyroglossal Cysts

3

Define Cyst

Sealed Cavity filled with air, pus, fluid

4

Define Sinus

Cavity within a tissue, can open externally

5

Define Fistula

Abnormal connection between two structures

6

Define Migration

Movement of cells during development

7

Define proliferation

Growth in cell number through cell division

8

Define Genetics

Mutations change patterns in migration, proliferation, etc.

9

How many Pharyngeal arches are there?

6, but 5th does not form

10

How many Pharyngeal grooves are there?

4 pairs

11

How many Pharyngeal pouches are there?

4 or 5 pairs

12

Where is the pharyngeal membrane located?

Between arches

13

Where/When do pharyngeal arches emerge?

At neural tube closure around 4 weeks of development

14

T/F The Arches contain the ectoderm, mesoderm, and endoderm, and also neural crest

TRUE

15

The Oropharyngeal membrane breaks down during week ________ and connects ______ to _________

1. 4
2. Stomodeum
3. Primitive gut

16

List the components of pharyngeal arches

1. Aortic Arch
2. Cartilaginous rod
3. Muscular component
4. Nerve
5. Nueral Crest

17

What is the aortic arch in terms of it being a component of pharyngeal arches?

1. An artery that arises from the truncus arteriosus of the primordial heart
2. Aortic Arches arise from mesoderm, bridge between the truncus arteriosus and the dorsal aorta

18

What purpose does the cartilaginous rod serve?

-forms the skeleton of the arch
-Definite Structures are formed from these

19

What does the muscular component of pharyngeal arches do?

-Differentiates into muscles of the head and neck

20

What does the nerve in the pharyngeal arches do?

Supplies the mucosa and muscles derived from the arch

21

By the 3rd week the arches are primarily __________, but by the 4th week, primarily ___________ has migrated into the arches.

1. Mesenchyme
2. Neural Crest

22

What happens to the aortic arches of pharyngeal arches 1 and 2?

-They largely disappear
-There are some remains:
-Maxillary, ext. Carotic (1)
-Stapedial (2)

23

What happens to aortic arches 3, 4, and 6?

-They are remodeled to form portions of some large arteries
-Common and Int. Carotid (3)
-Aortic, Subclavian (4)
-Pulmonary (6)

24

Where do muscles come from?

The mesoderm of the individual arches

25

What are the muscular derivatives of Arch 1?

Muscles of Mastication

26

What are the muscular derivatives of Arch 2?

Muscles of Facial expression

27

What are the muscular derivatives of Arch 3?

Stylopharyngeus

28

What are the muscular derivatives of Arch 4?

Pharyngeal Constrictors

29

What are the muscular derivatives of Arch 6?

Laryngeal Muscles

30

What are the sensory modalities of cranial nerves derived from?

Neural Crest and Ectodermal Placode

31

What are the Motor cranial nerves derived from?

CNS

32

What 2 main processes are formed by the 1st arch?

1. Mandibular process
2. Maxillary Process

33

What does the Mandibular process form?

-Lower Lip
-Lower Face
-Lower cheek regions
-Chin
-Mandible
-Body of the tongue

34

What does the Maxillary process form?

-Midface
-Upper cheek regions
-Upper lip sides
-Secondary palate
-Maxilla
-Zygomatic bone

35

What bone is associated with the 2nd arch?

Hyoid

36

What nerves are a product of the 1st arch?

V2 and V3

37

What muscles are a product of the 1st arch?

-All the muscles of Mastication
-Mylohyoid
-Anterior Belly of the digastric
-Tensor Veli Palatini
-Tensor Tympani

38

What Skeletal components are a derivative of the 1st arch?

1. Meckel's Cartilage
2. Maxilla
3. Malleus
4. Incus

Others Not highlighted in red:
-Anterior ligament of malleus
-Sphenomandibular LIgament
-Zygomatic bone and process
-part of temporal bone
-Vomer
-Palatine bone

39

What nerves are a derivative of Arch 2?

Facial Nerve

40

What muscles are derived from arch 2?

All the muscles of facial expression

Also:
-Posterior belly of the digastric
-Stylohyoid
-Stapedius

41

What skeletal components are derived from arch 2?

1. Stapes
2. Styloid Process
3. Lesser horn and upper portion of body of hyoid
4. Stylohyoid ligament

42

What nerve is derived from arch 3?

Glossopharyngeal

43

What muscle is derived from arch 3?

Stylopharyngeus

44

What skeletal components are derived from arch 3?

Greater horn and lower portion of body of hyoid bone

45

What Nerves are derived from arches 4-6?

VAGUS
-Superior Laryngeal (4th arch)
-Recurrent Laryngeal (6th arch)

46

What Muscles are derived from the 4th arch?

1. Constrictors of the pharynx
2. Cricothyroid
3. Levator Veli Palatini

47

What muscles are derived from arch 6?

Intrinsic muscles of Larynx

48

What skeletal components come from Arches 4-6?

Laryngeal Cartilages

49

What is Treacher Collins syndrome?

-Congenital First arch syndrome
-Hypoplasia of arch derived facial bones:
-Malar
-Zygomatic
-Down slanting of palpebral fissures
-lower eyelid colobomas
-ear deformations
-Cleft palate and tooth defects

50

What Causes Congenital First arch syndromes?

Failure of the neural crest to proper migrate in to the 1st arch causing deficits in resulting tissues

51

What is Pierre Robin Sequence?

-Hypoplasia of the mandible (micrognathia)
-Misplacement of tongue (glossoptosis)
-Cleft Palate
-Defects to the eye and ear
-Airway obstruction


**Cause is unknown

52

Pharyngeal Grooves can also be called Pharyngeal ______

Clefts

53

What are pharyngeal Clefts?

Indentations or pits between arches, as seen from the exterior

54

What are clefts lined with?

Ectoderm

55

What is unique about cleft 1?

It is the only cleft NOT obliterated in development

56

Can clefts 2-4 persist?

Yes, in abnormal situations

57

Pharyngeal cleft 1 gives rise to what?

External Auditory Meatus

58

What would cause a preauricular sinus or cyst congenitally?

1st or 2nd arch defect
*These are often unilateral

59

What are two types of Branchial sinuses, cysts, or fistulas that can develop?

1. Lateral Cervical
2. Internal Branchial

60

Describe Lateral Cervical Sinuses, cysts, or fistulas

-Uncommon
-Open Externally (neck)
-Failure of 2nd groove or cervical sinus to obliterate

61

Describe Internal Branchial sinuses, cysts, or fistulas

-Rare
-Persistent 2nd pouch
-Open into intratonsillar cleft (into pharynx)

62

What are pharyngeal pouches?

They form as Pits INTERNALLY in the pharynx, between the arches

63

Pouch linings are ___________ in origin

Endodermal

64

What structure fuses on the midline during development but still retains bilateral characteristics?

Thymus

65

What does the first pharyngeal pouch give rise to?

The middle ear

Distal:
-Together with lining of 1st cleft, forms tympanic membrane (eardrum)
-Widens and forms tympanic cavity (middle ear)

Proximal:
-Stays narrow, forms auditory (Eustachian) tube

66

What are the ossicles in the middle ear derived from?

1st and 2nd arch cartilage (derived from neural crest)

67

What is the tympanic membrane in the middle ear derived from?

1st cleft/pouch membranes, later neural crest

68

What are the tympanic cavity and internal auditory meatus derived from?

1st pouch

69

What does the 2nd pharyngeal pouch give rise to?

Lining of the crypts in the palatine tonsils

70

Tonsils themselves are mostly composed of ________

Mesoderm

71

What does the 3rd pharyngeal pouch give rise to?

Inferior parathyroid gland and the thymus

72

What specifically does the dorsal wing of the 3rd pouch become?

Inferior parathyroid glands
-regulates body calcium and phosphate levels

73

What specifically does the Ventral wing of the 3rd pouch become?

Thymus
-Produces T-cells, part of the immune system

74

What does the 4th pharyngeal pouch give rise to?

1. Superior parathyroid gland
2. Ultimobranchial body

75

What specifically does the Dorsal wing of the 4th pouch give rise to?

Superior parathyroid glands
-Regulates body calcium and phosphate levels

76

What specifically is derived from the ventral wing of the 4th pouch?

Ultimobranchial body
-Embryonic structure will contain C-cells of thyroid (regulate calcium levels via calcitonin)

77

T/F the Ventral 4th pouch is sometimes considered a 5th pouch

TRUE

78

T/F Primordia originate at mature functional sites

FALSE, they need to migrate

79

What is Cervical Thymus?

-Abnormality resulting from defects in migration
-Cord of thymus persists in neck on path of descent
-This is rare

80

What is Accessory Thymus?

-Abnormality resulting from defect in migration
-Piece of thymus remaining in path of descent

81

List 4 typically benign abnormalities resulting from defects in migration

1. Undescended parathyroid gland
2. Accessory thymic Issue
3. Persistent cord of thymic tissue
4. Ectopic inferior parathyroid gland

82

What is DiGeorge Syndrome?

-Failure of 3rd and 4th pouches to differentiate into thymus, parathyroid
-Neural Crest Defects
-Sporadic, teratogens?
-Variability in severity and outcome

83

What are the predominan defects for DiGeorge Syndrome? (Catch 22)

Cardiac Abnormality (especially Tetralogy of Fallot)
Abnormal Facies
Thymic Aplasia
Cleft Palate
Hypocalcemia/Hypoparatthyroidism

84

What are the 4 things present in a heart showing Tetralogy of fallot?

1. Overriding Aorta
2. Pulmonic Stenosis
3. Ventricular Septal Defect
4. Right Ventricular hypertrophy

85

Generally speaking, define a pharyngeal membrane

They form where the epithelia of the grooves and pouches approach each other

86

What are the 2 pharyngeal membranes?

1. Oropharyngeal Membrane
2. Tympanic membraine

87

Describe the Oropharyngeal membrane

1. Strictly speaking, not a pharyngeal membrane
2. Breaks down in 4th week to connect the mouth (stomodeum) with the gut/pharynx
3. marks site where ectoderm and endoderm meet
4. Glossopalatine arch marks location, separates oral cavity from pharynx

88

Describe the Tympanic membrane

-Derived from layers between 1st cleft and 1st pouch
-1st ectoderm and endoderm only, then neural crest moves

89

What do Hox genes regulate?

A-P Identity

90

What are Hox genes involved in?

Bodily segmentation during embryonic development

91

What type of DNA sequence is a homeobox?

180 bp DNA sequence

92

As a transcription factor what to they turn on?

Cascades of other genes

93

What patterns the Neural crest in the Proximal-Distal orientation?

DLX genes

94

What does the tongue develop from?

The floor of the arches

95

Which arches form which parts of the tongue? Generally speaking

Arch 1: forms anterior 2/3 of the tongue epithelium

Arch 2: it is covered up as arch 3 portion grows

Arch 3: Forms most of the remaining 1/3 of tongue epithelium

Arch 4: Forms just a bit of tongue at the very back of the throat

96

For tongue development, what does arch 1 form at weeks 4 and 5 respectively?

Week 4: Forms median swelling: Median tongue bud (tubercular impar)

Week 5: forms lateral swellings: distal tongue buds (lateral lingual swellings)

97

What does arch 2 form at week 4 to develop the tongue?

Forms midline swelling called Copula

98

What does arch 2 form at 5-6 weeks to develop the tongue?

Is overgrown by hypopharyngeal eminence from Archese 3, 4

99

Where does epiglottis arise?

Posterior to hypopharyngeal eminence

100

What gives rise to the tongue muscles?

Occipital somites

101

What is the terminal sulcus on the tongue?

-Dividing line between oral tongue and pharyngeal tongue
-Dividing line between anterior 2/3 and posterior 1/2
-It is between CN V and CN IX innervation
-Except circumvallate Papillae--innervated by CN IX but anterior to the sulcus

102

What is the foramen cecum the sit for?

Thyroid primordium

103

T/F Origination of the thyroid is bilateral

FALSE, it originates on the midline

104

What is an endodermal diverticulum?

-Forms during the development of the thyroid gland just posterior to the floor of the 1st arch (This is not a pharyngeal pouch)
-It is NOT biliateral: originates on the midline
-Elongates into the thyroglossal duct

105

What is the thyroglossal duct?

-Elongation of the Diverticulum
-Gland remainsin contact with tongue early, but duct is normally obliterated later in development

106

Where does the Thyroglossal duct connect with the tongue?

Foramen Cecum

107

What are the thyroid anomalies?

Thyroglossal duct cysts and sinuses

108

Why do thyroid anomalies form?

Failure of thyroglossal duct to completely pinch off and degenerate

109

Where an thyroglossal anomalies form?

May form anywhere along the course followed by the thyroglossal duct

110

By what age are most thyroglossal anamolies seen?

Most seen by 5 yrs old

111

T/F most thyroid anomalies are symptomatic

FALSE

112

How does the pituitary gland form?

-Forms from the upward invagination of the oral ectodermin the stomodeum (Rathke's pouch)
**This is not a pharyngeal pouch
-Separates from the oral epithelium, moves into contact with diencephalon