Development (L5-L9) Flashcards
1
Q
Name the primary germ layers
A
- Ectoderm
- Mesoderm
- Endoderm
- Neural Crest/Ecto-mesenchyme
2
Q
Where does ectoderm come from and what does it develop into?
A
From epiblast; develop into: skin, neural tube etc.
3
Q
Where does mesoderm come from?
A
From the migratory cells of the epiblast layer
4
Q
Where does endoderm come from
A
from the hypoblast layer
5
Q
When do pharyngeal arches appear?
A
in the 4th-5th week
6
Q
What lines the outer surface of the pharyngeal arches?
A
Ectoderm
7
Q
What lines the inner surface of the pharyngeal arches?
A
Endoderm
8
Q
What does each pharyngeal arch contain?
A
An artery, nerve, cartilage, muscles
9
Q
What is the 1st arch?
A
Mandibular arch
10
Q
What cartilage is in the 1st arch?
A
Meckel’s cartilage
11
Q
What does meckel’s cartilage form
A
- Bones: Incus & Malleus
- Ligaments: Sphenomandibular & Sphenomalleolar
12
Q
What does the 1st arch give rise to?
A
- body of tongue
- muscles of mastication (temporalis, masseter, pterygoid, mylohyoid, anterior body of digastric)
13
Q
Which nerve supplies the mandibular arch?
A
CN V (Trigeminal)
14
Q
Which arteries supply the 1st/ mandibular arch?
A
Carotid / Maxillary artery
15
Q
Name a disease caused by the degeneration of the mandibular arch
A
Treacher-Collin’s syndrome
16
Q
What is the 2nd arch called?
A
Hyoid arch
17
Q
Which cartilage is in the 2nd arch
A
Reichert’s cartilage
18
Q
What forms from the Reichert’s cartilage?
A
Stapes, Lesser horn and superior hyoid body, styloid process, stylohyoid ligament
19
Q
Which muscles form from the hyoid arch?
A
Muscles of facial expression and posterior belly of digastric muscle
20
Q
Which nerve supplies the hyoid arch?
A
Facial nerve (CN VII)
21
Q
What does the 2nd arch give rise to?
A
- Thyroid gland
- Tonsil
22
Q
Which nerve supplies the 3rd arch?
A
CN IX (Glossopharyngeal nerve)
23
Q
Which muscle does the 3rd arch supply
A
Stylopharyngeus muscle
24
Q
What does the 3rd arch form?
A
- greater horn of hyoid
- inferior hyoid body
- root of the tongue
25
What cartilage does the 4th arch give rise to?
Thyroid cartilage
26
What structures does the 4th arch give rise to?
Pharynx & Epiglottis
27
Which nerve supplies the 4th arch?
CN X (Vagus) - superior laryngeal branch
28
Which muscles do the 4th arch form?
Pharyngeal constrictor and muscles of the soft palate
29
Which nerve supplies the 6th arch?
CN X (Vagus) - Inferior laryngeal nerve
30
What does the 1st cleft/groove give rise to?
External auditory meatus; Ear drum
31
What does the 1st pouch give?
- Eustachian tube
- Middle ear cavity
- Tympanic membrane
- Ventral part obliterated by tongue
32
What does the 2nd pouch give?
Tonsillar fossa & Ventral part obliterated by tongue
33
What does the 3rd pouch give?
Inferior parathyroid gland & Thymus
34
What does the 4th pouch give?
Superior parathyroid gland (will fuse with the inferior one)
Also becomes the parafollicular (C cells) associated with the thyroid gland that produces calcitonin
35
Name the 5 facial processes
Frontonasal process, paired maxillary process, paired mandibular process
36
When does development of the face start?
At 4 weeks
37
What is "fusion" VS true fusion?
"Fusion" involves the fusion of prominences by elimination of furrow whereas true fusion involves the fusion of separate processes
38
Name an example of "fusion"
Between the medial nasal prominence
39
Give an example where true fusion takes place
Between the medial nasal prominence and the maxillary process
40
Which facial structure does the frontonasal prominence contribute to?
Forehead, bridge of nose
41
Which facial structure does the medial nasal prominence contribute to?
Philtrum of lip, crest and tip of the nose
42
Which facial structure does the lateral nasal prominence contribute to?
Alae of nose
43
Which facial structure does the maxillary prominence contribute to?
Cheeks, lateral upper lip
44
Which facial structure does the mandibular prominence contribute to?
Lower lip
45
What do mesenchymal cells give?
Osteoblasts and chondroblasts
46
When does ossification of the mandible begin?
Week 6-7
47
When does ossification of the maxilla begin?
Week 8
48
When does ossification of the palate and nasal capsule begin?
Week 8
49
What is the primary palate derived from?
Medial nasal prominences (part of frontonasal prominence)
50
What is the secondary palate formation?
It is the contact of lateral palatal shelves at the midline.
51
What is the function of the secondary palate?
It separates the nasal airway and the oral cavity
52
State the functions of the secondary palate
1. Mastication (Bolus formation)
2. Sensation of taste and texture
3. Speech
53
Describe the growth of the palatal shelves
Initially, the palatal shelves develop medially and downwards. At week 8, they then rapidly elevate (flip upwards into a horizontal orientation) and grow towards each other.
54
Name a source of extrinsic force involved in palatal shelve elevation
Tongue - withdrawal of the tongue due to head lifting from cardiac plate; Meckel's cartilage growth in the 1st pharyngeal arch and increased height of nasal cavity
55
Describe the intrinsic shelf force w.r.t palatal shelve elevation
- A turgor pressure is generated by hydration of the extracellular matrix by hyaluronan, a glycosaminoglycan (GAG).
- Proliferation of mesenchymal cells result in shortening via contractile microfilaments produces the force
- Partly directed by Type I collagen which provides strength and is very flexible
56
Name 3 sources of palatal fusion problems
1. Lack of matrix factors (lack of expression of HA by HA synthase 1/2/3)
2. Failure to fuse (completely/incompletely) - cleft palate
3. Epithelial remnants - epithelial cell rests/ cystic potential
57
What allows the fusion of palatal shelves with just itself and not with other epithelial?
Specific sticky surface glycoprotein
58
How does the midline disintegrate during fusion of the palatal shelves?
Epithelial-mesenchymal transition - switching of epithelial cells to mesenchymal
59
What precedes the mandible?
Meckel's cartilage
60
What does Meckel's cartilage precede?
Mandible
61
What role does Meckel's cartilage play in mandible formation?
It serves as a template for the formation of the mandible (bone formation follows the line of cartilage)
62
What structure(s) does the posterior extremity of Meckel's cartilage give?
Malleus of inner ear & Sphenomalleolar ligament
63
Where is the position of the Meckel's cartilage?
It extends from the otic capsule (bony capsule of developing inner ear) to a midline symphysis
64
Where is the primary ossification site of the mandible?
Between the incisive and mental nerve
65
Is there a change in ossification type of mandible from primary to secondary cartilage sites?
Yes, from intramembranous ossification to endochondral ossification
66
Name some growth factors involved in the formation of the mandible
VEGF (vascular endothelial growth factor)
TGFB (transforming growth factor-beta)
BMPs
67
What forms where the mandibular bone envelopes the inferior alveolar nerve?
Mental foramen
68
Name the 3 mandibular secondary cartilage
1. Symphyseal
2. Coronoid
3. Condylar
69
State when the symphyseal cartilage appear and disappear
Appears at 16 weeks
| Disappears at 1st year after birth
70
State when the coronoid cartilage appear and disappear
Appears at 14-16 weeks
| Disappears before birth
71
State when the condylar cartilage appear and disappear
Appears at 10-12 weeks
| Disappears at about 20 years of age
72
Function of the condylar cartilage
Produces cartilage when jaw starts to work; allowing endochondral sites formation
73
Function of the symphyseal cartilage
Allows for fusion of the 2 mandible when it disappears
74
How is the primary cartilage different from the secondary cartilage?
- Primary cartilage uses intramembranous ossification whereas secondary cartilage uses endochondral ossification
- Primary cartilage has hyaline cartilage; Secondary cartilage has fibrocartilage
- Primary cartilage uses interstitial growth; Secondary cartilage uses appositional growth
75
List 3 developmental abnormalities of the mandible
1. Agnathia - no mandible
2. Micrognathia - very small mandible
3. Macrognathia - very large mandible
76
What results in agnathia and micrognathia?
Lack of ectomesenchyme in the mandibular arch
77
What disorder is macrognathia associated with?
Genetic; pituitary disorders - e.g. acromegaly
78
When does development of the tongue start?
at 4 weeks iul
79
Which pharyngeal arch is involved in the development of the tongue?
Arch 1, 3, 4
80
Which part of the tongue does pharyngeal arch 1 form
anterior 2/3rds of the tongue
81
Which part of the tongues does pharyngeal arch 3 form?
posterior 1/3rd of the tongue
82
What does pharyngeal arch 4 form in relation to the tongue
Tongue muscles
83
What is the anterior 2/3rd and posterior 1/3rd of the tongue separated by?
Sulcus terminalis
84
What does the first pharyngeal arch contain in relation to the tongue?
2 lingual swelling &
| 1 tuberculum impar (medial swelling)
85
What does the third pharyngeal arch contain in relation to the development of the tongue?
Hypobranchial eminence
86
What causes the detachment of the anterior 2/3rd of the tongue?
Ectoderm grows between anterior 2/3rd of the tongue and the underlying arch. Ectoderm degenerates except in the midline, resulting in separation of tongue except for the midline frenulum.
87
Where does the anterior 2/3rd of the tongue come from and name its general sensory sensation innervation
Pharyngeal arch 1;
| CN V
88
Where does the posterior 1/3rd of the tongue come from and name its general sensory sensation innervation
Pharyngeal arch 3;
| CN IX
89
Name the 3 types of tongue development abnormalities that could occur
1. Failure of fusion
2. Imperfect detachment - ankyloglossia
3. Growth disorders
90
What growth disorders of the tongue can there be?
1. Aglossia
2. Microglossia - small tongue
3. Macroglossia - large tongue
91
Which pharyngeal arch does the thyroid gland develop from?
Arch 2
92
What is the development of the thyroid gland associated with?
Tongue development
93
What follows the formation of the thyroid tissue?
Disintegration of the thyroglossal duct
94
Name 3 abnormalities of thyroid development
1. Ectopic thyroid gland
2. Persistent thyroglossal duct
3. Pathological changes to remnants of the thyroglossal duct (Thyroglossal cyst / Thyroglossal fistula)
