Head and neck: development Flashcards
What are the 3 major areas of growth in the head?
skull base
face
cranial vault (calvarium)
What causes the skull base to elongate?
cartilage and endochondral ossification
How does the face grow?
Facial bones grow inferiorly and enlarge via endochondral ossification
how does the cranial vault grow?
Mesenchyme forms models that ossify via intramembranous ossification
bones enlarge radially until they meet
How do the flat, paired bones of the skull (frontal, parietal, posterior occipital, parietal region of temporal) form?
From somatic mesoderm via intramembranous ossification
what is the “soft spot” of the skull called? what bones create this spot?
anterior fontanelle
front, left and right parietal bones
What causes a divot in the skull when it is still developing?
dehydration
What is the only true synovial joint of the skull?
temporomandibular joint
allows condylar process of mandible to articulate with temporal bone
What allows for smooth movement between the mandible and temporal bone?
fibrocartilage disc
What are the pharyngeal arch muscles and their innervations?
1) muscles of mastication - CN V3 - mandibular
2) muscles of facial expressions - CN VII - Facial
3&4) muscles of pharynx and palate - CN IX, X - glossopharyngeal, vagus
6) muscles of phonation - CN X - recurrent fibers of vagus
What does the auricle develop from?
6 auricular hillocks that fuse and migrate and eventually form the mature auricle
What can malformations of the external ear be indicative of?
1st and 2nd arch problems
What do the auricular hillocks come from?
1st and 2nd pharyngeal arches
Failure of cervical sinus to obliterate can result with what?
branchial fistulae or cysts
What is the branchial fistulae?
openings from the skin or oral region that extend to cervical cyst
what are branchial cysts?
isolated, fluid-filled sacs that do not open to either the skin or pharynx
how is the thyroid developed?
thyroid gland “descends,” leaving a pit (foramen cecum) to mark origin from tongue
body growth pulls thyroid inferiorly past hyoid to anterior trachea
What are some abnormalities during thyroid migration?
Path of migration - can pass through tongue, anterior to hyoid, thyroid and cricoid cartilage
thyroglossal duct cysts - thyroid tissue lodged along path of thyroglossal duct
pyramidal lobe - extends from thyroid gland superiorly along path of thyroglossal duct
how does a unilateral cleft lip happen?
failure of medial nasal prominence and maxillary process fusion
how does a oblique facial cleft happen?
failure of medial + lateral nasal prominence and maxillary prominence fusion
how does a bilateral cleft lip happen?
failure of medial nasal prominence bilaterally and maxillary processes fusion
what is the philtrum connected to?
incisive bone/primary palate
what does the philtrum contribute to in terms of teeth and palate?
contributes 4 incisor teeth to maxilla
fuses with rest of hard palate
what is holoprosencephaly? what are the two types? what type of appearance can happen?
failure of cerebral hemispheres and lateral ventricles to separate
semilobar and alobar
cyclopia
