embryo skull, arches, face

Question 1

What bones form the neurocranium, cranial base and viscerocranium

Answer 1

neurocranium: Vault bones (interparietal part of occipital, parietal, frontal, squamous temporal)
cranial base:ethmoid, sphenoid, petrous temporal and occipital bones
viscerocranium:

Question 2

How are neuroranium, cranial base, and viscerocranium formed?

Answer 2

cartilage=endochondralossification
membranous=intramembranous ossification

Neurocranium –>Membranous : vault bones
–>Cartilaginous: Cranial base bones (basicranium)
Viscerocranium
• Cartilaginous: ossicles, hyoid bone
• Membranous: face bones

Question 3

What is the spheno-occipital synchondrosis and when does it close?

Answer 3

Synchondrosis type joints join frontal , ethmoid, sphenoid and occipital bones for longitudinal and
lateral growth. Spheno-occipital synchondrosis fuses around 15-17 years.

Large angle –> square jaws and overbite
Small angle –> wide angled mandibles and
mandibular protrusion

Question 4

What is the cranial base angle and how does it affect the shape of the face?

Answer 4

between occipital and sphenoid bones. Predicts the position of the mandible and susceptablity tomalocclusions

Question 5

What types of cells converge in the pharyngeal arches?

Answer 5

Condensations of mesenchyme & neural crest cells

Question 6

What types of tissues do these pharyngeal arch cells produce?

Answer 6

• Cranial nerve (V, VII, IX, X)
• Cartilage that will either remain (eg. thyroid and cricoid) or become surrounded with intramembranous bone ( mandible, maxilla).
• Artery (aortic arch)

Neural crest cells migrate through and interact with
the pharyngeal arch mesenchyme to form the bones,
cartilage, skin, arteries & nerves of the face

Question 7

Describe the embryological origins and any migrations of the auditory system

Answer 7

From Pharyngeal grooves and pouches
Groove 1. ext acoustic meatus
Pouch
1. tympanic cavity / auditory tube

Question 8

What are the underlying developmental steps that lead to cleft lip and palate?

Answer 8

LIP: Maxillary and medial nasal prominences normally fuse to form continuous upper lip
• Cleft lip due to failure of this fusion.
PALATE:Palatine processes of maxilla fuse with septum to separate oral from nasal cavities. a failure in the
fusion of palatine processes

Question 9

Describe the embryological origins and any migrations of palatine tonsil

Answer 9

Pharyngeal pouch 2–>palatine tonsil

Question 10

Describe the embryological origins and any migrations of thymus,

Answer 10

Pharyngeal Pouch

3. thymus and parathyroid migrate down into neck
4. parathyroid and C cells of thyroid migrate down into neck

Question 11

Describe the embryological origins and any migrations of parathyroid and thyroid glands.

Answer 11

Thyroid descends from base of tongue through foramen cecum, thyroglossal duct, anterior to hyoid bone & larynx.

Question 12

Pharyngeal arches develop into NERVE

Answer 12

Mandibular Arch: trigeminal V
Hyoid Arch: facial VII
3rd Arch:glossopharyngeal IX
4th & 6th Arch:vagus X

Question 13

Pharyngeal arches develop into BONE/Cartilage

Answer 13

Mandibular Arch: mandible, maxilla, zygoma, ossicles, temporal
Hyoid Arch: styloid p, hyoid, stapes
3rd Arch: hyoid
4th & 6th Arch :Larynx

Question 14

Pharyngeal arches develop into muscles

Answer 14

Mandibular Arch: masticators, ant digastric, tensor tynpani
Hyoid Arch: facial expression, post digastric, stylohyoid, staepedius
3rd Arch: stylopharyngeous
4th & 6th Arch :pharynx, larynx

Question 15

Facial development

Answer 15

Face is formed by medial migration and fusion of
maxillary, mandibular, nasomedial and nasolateral
processes
All from 1st pharyngeal arch