Craniofacial Complex Flashcards
Functional Matrix
The functional relationship between soft tissue and skeletal units.
Size, shape, structure integrity, and location of each components results from secondary and compensatory responses to the operational demands of the functional matrix.
Consider biology, environment, and behavior.
Chondocranium
Base of the skull.
- Develops first during embryology
- Derived from endochondrial ossification
- Forms supportive platform on which remainder of skull develops
Dermatocranium
Creates the brain case.
- Develops second during embryology
- Derived from intramembranous ossification
- Fontanelle are reminants of the membrane at birth
Splanchnocranium
Contributes to facial structure.
- Formed last during embryology.
- Derived from intramembranous ossification.
- Does not complete formation until the end of puberty.
Primary Neurulation
-
During 3rd week of development:
- Transition from bi-laminar disc to tri-laminar disc.
- Longitudinal band of ectodermal cells expands to form the neural plate.
- Neural plate continues to expand and folds in the middle forming the neural groove.
- Neural groove deepens as neural folds on either side approach each other at the dorsal midline.
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During 4th week of development:
- Neural folds begin to fuse centrally.
- Fusion proceeds both caudally and rostrally forming the neural tube.
- As neural tube forms, it seperates from overlying ectoderm and sinks into underlying mesoderm.
- Leaves behind a group of cells from the crest of each neural fold ⇒ future neural crest cells.
-
Future neural crest cells migrate out of the neural folds, seperating the ectoderm from neural tube.
- Controlled by Hox Genes
- Neural tube expands forming the three primary vesicles:
- Prosencephalon ⇒ forebrain
- Mesencephalon ⇒ midbrain
- Rhombencephalon ⇒ hindbrain
Rhombomeres
The part of the neural tube that develops behind the rhombencephalon (hindbrain) develops a series of bulges ⇒ rhombomeres.
Neural Crest Cell
Migration
During 4th to 5th week of development:
Neural crest cells associated with specific rhombomeres migrate into the ventrolateral aspect forming the pharyngeal arches.
Six paired outpocketings:
1st pharyngeal arch: rhombomeres 1, 2, and 3
2nd pharyngal arch: rhombomeres 3 and 4
3rd pharyngal arch: rhombomeres 6 and 7
4th pharyngal arch: rhombomere 5
5th pharyngal arch: often never develops or degenerates quickly
6th pharyngal arch: rhombomere 5 (cannot be seen externally)
Pharyngeal Arches
Pharyngeal arches
- Composed of mesoderm
- Each arch is associated with a specific:
- cranial nerve
- muscle group
- artery
- skeletal or cartilaginous derivative
First Pharyngeal Arch
Derivatives
-
Cranial nerves:
- V2: maxillary division of trigeminal nerve
- V3: mandibular division of trigeminal nerve
-
Muscle:
- Muscles of mastication
- Tensor tympani
- Tensor veli palatini
-
Cartilage & Skeletal Elements:
- Part of sphenoid
- Incus
- Malleus
- Maxilla
- Mandible
- Zygomatic
- Squamous portion of temporal bone
-
Vessels:
- Maxillary artery
-
Other structures:
- Mucous membranes of anterior 2/3 of tongue
Second Pharyngeal Arch
Derivatives
-
Cranial nerves:
- VII: facial
-
Muscle:
- Muscles of facial expression
- Posterior belly of digastric
- Stylohyoid
- Stapedius
-
Cartilage & Skeletal Elements:
- Stapes
- Styloid process
- Stylohyoid ligament
- Lesser horns of hyoid
-
Vessels:
- Stapedial artery
Third Pharyngeal Arch
Derivatives
-
Cranial nerves:
- IX: glossopharyngeal
-
Muscle:
- Stylopharyngeous
-
Cartilage & Skeletal Elements:
- Greater horn of hyoid
-
Vessels:
- Common carotid
- Proximal internal carotid
Fourth Pharyngeal Arch
Derivatives
-
Nerves:
- CN X: vagus
- Superior laryngeal nerve
-
Muscle:
- Pharyngeal constrictors
- Cricothyroid
- Levator veli palatini
-
Cartilage & Skeletal Elements:
- Laryngeal cartilages
-
Vessels:
- Proximal right subclavian
- Arch of aorta
-
Other structures:
- Mucous membrane of posterior 1/3 of tongue
Sixth Pharyngeal Arch
Derivatives
-
Nerves:
- CN X: vagus
- Recurrent laryngeal nerve
-
Muscle:
- Intrinsic muscles of the larynx
-
Cartilage & Skeletal Elements:
- Laryngeal cartilages
-
Other structures:
- Mucous membranes of posterior 1/3 of tongue
Branchial Clefts & Pouches
Connective tissue between the pharyngeal arches form:
Branchial clefts externally ⇒ ectoderm
Branchial pouches internally ⇒ endoderm
First Branchial/Pharyngeal Pouch
Derivatives
- Mucosa of eardrum
- Tympanic cavity
- Auditory tube
- Mastoid antrum