Craniofacial Development Flashcards
What are the pharyngeal arches?
Bars of paraxial mesoderm between the pouches and clefts.
When do the pharyngeal arches appear in humans?
In the 4th and 5th weeks of development.
What does the paraxial mesoderm of the arches go on to make?
Muscles.
Which muscles are derived from the 1st pharyngeal arch? Which nerve are they innervated by?
MUSCLES OF MASTICATION + anterior belly of digastric, mylohyoid
Vc
Which muscles are derived from the 2nd pharyngeal arch? What are they innervated by?
Muscles of facial expression, VII
Which muscle is derived from the 3rd pharyngeal arch? What supplies it?
Stylopharyngeus, IX
Which muscles are derived from the 4th pharyngeal arch? Which nerve are they innervated by?
Muscles of vocalisation and swallowing, superior laryngeal branch of vagus X
Which muscles are derived from the 6th pharyngeal arch? Which nerve are they innervated by?
Internal muscles of larynx, recurrent laryngeal branch of vagus.
What do the arch cartilages arise from?
Neural crest cells.
What is the origin of neural crest cells?
Ectoderm
Where do the neural crest cells emigrate into the arches from?
The dorsal region/crest of the embryonic neural tube. From the hindbrain and midbrain in the head.
What kind of cell are neural crest cells?
Stem cells
Which cartilages do neural crest cells form from the 1st arch?
Palatopterygoquadrate cartilage
Meckel’s cartilage
Which cartilages do neural crest cells form form the 2nd arch?
Reichert’s cartilage
Which bones are formed from the 1st arch?
Allisphenoid
Malleus
Incus
Which bones and ligaments are formed from the 2nd arch?
Stapes
Styloid process
Stylohyoid ligament
Lesser cornu of hyoid
Which bones are formed from the 3rd arch?
Body of hyoid
Greater cornu of hyoid
Which cartilages are formed from the 4th arch?
Thyroid cartilage
Cricoid cartilage
Which arches do cardiac neural crest cells migrate through? What do they go on to form?
4th and 6th arches, aorticopulmoary septum
Name 3 ways of fate mapping.
1) chimeric quail-chick grafting (replace chick neural tube + crest with quail, identify quail cells with quail specific antibody)
2) labelling neural tube with fluorescent dye
3) genetic lineage tracing in mice
What do cranial neural crest cells form? (13)
Many cartilages+bones of the skull Tooth pulp+odontoblasts Pericytes, connective tissue, smooth muscle of arteries Thymus+parotid gland mesenchyme Melanocytes Parasympathetic ganglia Olfactory ensheathing cells Schwann cells Dermis Meninges of forebrain Peripheral somatosensory neurons
What do nerve-dwelling neural crest cell progenitors give rise to? (neural crest cells colonising peripheral nerves)
Melanocytes
Post-ganglionic parasympathetics
Where are the cell bodies of peripheral somatosensory neurons?
Trunk dorsal root ganglia
Trigeminal ganglion
Superior ganglia of VII, IX and X
Where do vagal neural crest cells come from?
Caudal hindbrain
Where do peripheral special sensory and viscerosensory neurons come from?
Cranial neural placodes
Which cranial nerves contain viscerosensory fibres? Which ganglia of these nerves do they arise from?
VII, IX, X, inferior ganglia
What are cranial neural placodes?
Bilateral patches of thickened neurogenic surface ectoderm, paired on either side of the head.
What does the otic placode form? (VIII)
The entire inner ear, special sensory neurons of the ear, cranial nerve VIII
What does the olfactory placode form?
The entire olfactory epithelium, including olfactory receptor cells
What does the lens placode form? (II)
The lens of the eye.
Is the trigeminal nerve mainly made up of cranial neurogenic placode or neural crest cells?
Neural crest cells
What does the geniculate ganglion form? (VII)
Some of the viscerosensory neurons in the geniculate ganglion (inf ganglion VII). Their axons transmit information from taste buds in the ant 2/3 tongue to the nucleus of the solitary tract in the medulla.
What does the petrosal placode form? (IX)
Viscerosensory neurons in the petrosal ganglion (inf ganglion IX). Their axons transmit information from the nucleus of the solitary tract to:
Taste buds from post 1/3 tongue
General visceral information from pharynx
Chemoreceptors and mechanoreceptors in the carotid body and sinus.
Where do neural crest derived cells in the superior ganglion IX transmit information? What information
Somatosensory information from the post 1/3 tongue, pharynx, auditory tube and middle ear to trigeminal sensory nucleus.
What does the nodose placode form? Where do their fibres transmit information to and from?
Viscerosensory neurons in the nodose ganglion (inferior ganglion of X). Information to the nucleus of the solitary tract from the
Taste buds in the epiglottic vallecula
General visceral info from pharynx, larynx
Chemoreceptors and mechanoreceptors in the aortic bodies and aortic arch
What does the first pharyngeal cleft form?
The EAM
What does the first pharyngeal pouch form?
The middle ear and Eustachian tube.
