Embryo of Head/Neck Flashcards
1
Q
Head and Neck Development occurs between what weeks?
A
4-10 weeks
2
Q
The bones of the head can be divided into what?
A
Neurocranium and Viscerocranium
3
Q
What does the Neurocranium form?
A
Bones of the cranial base and vault
4
Q
The neurocranium is primarily derived from what?
A
Dermal bones (intermembranous ossification)
5
Q
What is the Viscerocranium?
A
Bones of the face and pharyngeal arches
6
Q
The viscerocranium is derived from what?
A
intermembranous and endochondral ossification (dermal and endochondral bones)
7
Q
Describe a Fontanelle
A
Space between the bones of the skull in a fetus or newborn
8
Q
Why do newborns have fontanelles?
A
Allows for more flexibility during birth
9
Q
When will fontanelles close (be specific)?
A
Posterior fontanelle: 3 months
Anterior fontanelle: 15 months
10
Q
What are pharyngeal arches (branches)?
A
- Bilateral structures that develop off of the pharyngeal foregut
- Will form many structures of the head and neck
11
Q
How are pharyngeal arches numbered?
A
Arches 1-6 (Arch 5 does not appear in humans)
12
Q
What supplies each pharyngeal arch?
A
Their own aortic arch vessel (derived from truncus arteriosus)
13
Q
What is associated with each pharyngeal arch?
A
- Pharyngeal cleft (groove)
- Pharyngeal Pouch
- Pharyngeal Membrane
14
Q
Describe Pharyngeal Cleft
A
External indentation in between two pharyngeal arches (4 in total)
15
Q
Describe Pharyngeal Pouch
A
Internal indentation in between two pharyngeal arches (4 in total)
16
Q
Describe Pharyngeal Membrane
A
Lining in between a pharyngeal groove and pharyngeal pouch (4 in total)
17
Q
What is the name given to the 1st pharyngeal arch?
A
Mandibular arch
18
Q
The 1st pharyngeal arch is split into what sections?
A
Upper Maxillary prominence
Lower Mandibular prominence
19
Q
The 1st pharyngeal arch surrounds what structure?
A
Stomodeum (primordial mouth)
20
Q
What germ layers are found in pharyngeal arches?
A
Ectoderm, Mesoderm, Endoderm
21
Q
Describe the contents of pharyngeal arches (4)
A
- Aortic arch vessel
- Cranial nerve
- Muscle components (paraxial mesoderm)
- Cartilage (neural crest cells)
22
Q
Where does the muscle come from in pharyngeal arches?
A
Paraxial Mesoderm
23
Q
Where does cartilage come from in pharyngeal arches?
A
Neural Crest Cells
24
Q
Cartilage in pharyngeal arches will contribute to what general structures?
A
Some Skeletal structures and ligaments in the head/neck
25
Describe the Nerve Derivative: Pharyngeal Arch 1
Trigeminal (CN V): Maxillary prominence [V2] and mandibular prominence [V3]
26
Describe the Nerve Derivative: Pharyngeal Arch 2
Facial Nerve (CN VII)
27
Describe the Nerve Derivative: Pharyngeal Arch 3
Glossopharyngeal (CN IX)
28
Describe the Nerve Derivative: Pharyngeal Arch 4
Superior Laryngeal Branch of Vagus (CN X)
29
Describe the Nerve Derivative: Pharyngeal Arch 6
Recurrent Laryngeal Branch of Vagus (CN X)
30
Describe the Muscle Derivative: Pharyngeal Arch 1
1. Muscles of Mastication
2. Mylohyoid
3. Digastric: Anterior Belly
4. Tensor Tympani
5. Tensor Veli Palatini
31
Describe the Muscle Derivative: Pharyngeal Arch 2
1. Muscles of Facial Expression
2. Digastric: Posterior Belly
3. Stylohyoid
4. Stapedius
32
Describe the Muscle Derivative: Pharyngeal Arch 3
Stylopharyngeus
33
Describe the Muscle Derivative: Pharyngeal Arch 4
1. Constrictors of Pharynx
2. Cricothyroid
3. Levator Veli Palatini
34
Describe the Muscle Derivative: Pharyngeal Arch 6
Intrinsic muscles of larynx
35
Describe the Cartilaginous Derivative: Pharyngeal Arch 1
1. Malleus
2. Incus
3. Anterior Ligament of Malleus
4. Sphenomandibular Ligament
36
Describe the Cartilaginous Derivative: Pharyngeal Arch 2
1. Stapes
2. Styloid Process
3. Lesser Horn of Hyoid
4. Upper Body of Hyoid
5. Stylohyoid Ligament
37
Describe the Cartilaginous Derivative: Pharyngeal Arch 3
1. Greater Horn of Hyoid
2. Lower Body of Hyoid
38
Describe the Cartilaginous Derivative: Pharyngeal Arch 4
Laryngeal Cartilages (thyroid, cricoid, arytenoid, corniculate, and cuneiform cartilages)
39
Describe the Cartilaginous Derivative: Pharyngeal Arch 6
Laryngeal Cartilages (same as arch 4)
40
Pharyngeal Pouch 1 forms what?
1. Tympanic Cavity of middle ear
2. Auditory (eustacian) tube
41
Pharyngeal Pouch 2 forms what?
Palatine Tonsil
42
Pharyngeal Pouch 3 forms what?
1. Dorsal portion: inferior parathyroid gland
2. Ventral portion: left and right pouches fuse to be thymus gland
43
Pharyngeal Pouch 4 forms what?
1. Dorsal Portion: superior parathyroid gland
2. Ventral Portion: forms ultimobranchial body
44
What does the Embryonic structure ultimobranchial body become?
Parafollicular cells (C-cells) of the thyroid
45
1st Pharyngeal Cleft and Membrane forms what?
Cleft: External auditory meatus
Membrane: Tympanic membrane
46
2nd - 4th Pharyngeal Cleft and Membrane form what?
Cleft: Cervical Sinus (will eventually overgrow)
Membrane: No adult structures
47
(T/F) Ectopic Superior Parathyroid Glands occur when the 2nd pharyngeal pouch fails to properly migrate.
False. The 4th pouch would have failed to migrate
48
(T/F) Ectopic Thymus Glands occur when the ventral 3rd pouch fails to migrate
True
49
Craniofacial problems can occur when what structure does not migrate?
Neural Crest Cells
50
What substances can cause neural crest cells to not migrate properly during development?
Alcohol and retinoic acid (Vitamin A) [known as craniofacial teratogens]
51
What physical characteristics occur when neural crest cells fail to migrate to the head and neck?
Hypoplasia of mandible, facial defects, malformed ears
52
What disease has been associated with craniofacial abnormalities?
Zika virus has shown neural crest cell migration errors
53
What is a cervical cyst?
A remnant of the cervical sinus that can appear anywhere along the anterior/parallel to the SCM.
54
What types of cervical fistulas are there?
External and Internal
55
Define Internal Cervical Fistula
Opening that extends into the pharynx
56
Define External Cervical Fistula
Opening that extends outside the neck
57
Where does the tongue begin development?
Floor of the pharynx from the 1st four pharyngeal arches and occipital somites
58
What does the 1st pharyngeal arch form in relation to the tongue?
Median tongue bud (medial lingual swellings) and two distal tongue buds (lateral lingual swellings) which overgrow the medial tongue bud
59
What do the medial and lateral tongue swellings form and what is the innervation?
Mucosa of the anterior 2/3 tongue
Nerve: V3
60
What does the 2nd pharyngeal arch form in relation to the tongue?
Copula (which does get overgrown)
61
What does the copula do? What is the innervation?
Taste from anterior 2/3 tongue
Nerve: Chorda tympani branch of CN VII (facial nerve)
62
What does the 3rd and 4th pharyngeal arch form?
Hypopharyngeal (hypobranchial) eminence
63
What does the Hypopharyngeal Eminence do?
(Bonus: Where does it come from)
Forms the mucosa of the posterior 1/3 tongue and receives taste/general sensory from the region via CN IX (Glossopharyngeal)
(Bonus: 3rd and 4th Pharyngeal Arches)
64
What do occipital somites form? Innervation?
Intrinsic muscles of the tongue and "most" extrinsic tongue muscles (palatoglossal is not)
CN XII (Hypoglossus)
65
Where does the thyroid gland begin formation?
Thyroid bud (primordium) from between the anterior 2/3 and posterior 1/3 of tongue
66
After formation of the Thyroid Bud (Primordium), what happens next?
The bud migrates (descends) down the developing neck
67
Where does the Thyroid bud remain connected during development?
Floor of the pharynx via the thyroglossal duct
68
After the thyroglossal duct fuses, what is the only remnant left?
Pit of the tongue called the foramen cecum
69
What is it called when the thyroid gland is found in areas it typically should not be?
Ectopic Thyroid Gland
70
What is it called when an individual has a fluid-filled sac formed from remnants of the throglossal duct?
Thyroglossal duct cyst
71
What is it called when an individual has a canal that connects a thyroglossal duct cyst to the outside of the neck?
Thryoglossal fistula
72
What is it called when an individual has thyroid tissue that extends superiorly from the isthmus of thyroid?
Pyramidal lobe (remanent of thyroglossal duct)
73
What swellings/prominences form around the stomodeum that form the face?
1. Frontonasal prominence
2 & 3. Maxillary prominence
4 & 5. Mandibular Prominence
74
The frontonasal prominence is derived from what tissue?
Mesenchyme
75
What develops off the frontonasal prominence?
Nasal placode
76
What do nasal placodes develop into?
Nasal pit and raised tissue on either side of the pit (medial and lateral nasal process)
77
Once the Nasal processes form, what happens?
They will fuse and become the intermaxillary segment
78
What does the intermaxillary segment form (prior to fusing with the maxillary process)
1. Philtrum
2. Premaxilla (part of maxilla with incisors)
3. Primary Palate (anterior triangular part)
79
The intermaxillary segment will fuse with what?
Maxillary process
80
The Intermaxillary segment fuses with the maxillary process to form what?
Upper lip and jaw
81
How is the palate formed?
Fusion of the primary palate (formed from intermaxillary segment) and the secondary palate
82
How is the secondary palate formed?
Fusion of the left and right palatine shelves that grow off the maxillary prominences
83
What does the secondary palate form prior to fusion with primary palate?
Posterior hard palate and all of the soft palate
84
In what direction does the palatine shelves fuse?
Anterior - posterior
85
Define a Cleft Lip (in relation to Embryology)
Failure of the maxillary prominences to fuse with the intermaxillary segment
86
A cleft lip is most common in who?
Males
87
Define a Cleft Palate (in relation to Embryology)
Failure of palatine shelves to fuse
88
A cleft palate is most common in who?
Females
