Development of Pharyngeal Arches Flashcards
What are the three main components of a pharyngeal arch?
- Mesenchymal core (from mesoderm and neural crest)
- Internal ectoderm pouch
- External cleft (ectoderm)
How many pharyngeal arches are there?
5
Pharyngeal arches 1, 2, 3, 4, (5 disappears) and 6
What is the stomodeum?
ending of GI gut tube
What are the two prominances of the 1st pharyngeal arch?
- upper maxillary
- lower mandibular
What are the two main sources of mesenchyme for each arch and what do they give rise to?
Each arch has a mesenchyme core from two main sources –
mesoderm and neural crest:
o Muscle (brachial muscles)
o Cartilage element
o Artery
o Cranial Nerve
What happens to paraxial mesoderm in the pharyngeal arches?
migrates into pharyngeal arches and elsewhere to form mostly muscle tissue of head (and some connective tissue/bone)
What is the contribution of the lateral plate mesoderm to the head?
Small
What is the function of the neural crest and the ectodermal placodes?
- Neural crest (ventral flow around placodes and into
pharyngeal arches – mesenchyme, ganglia, nerves)
- Ectodermal placodes (thickening of ectoderm that can
help give rise to sensory neurons
What are the muscles of the 1st pharyngeal arch?
- muscles of mastication
- anterior belly of digastric
- mylohyoid
- tensor tympani
- tensor vali palatini
What are the muscles of the 2nd pharyngeal arch?
- muscles of facial expression
- stylohyoid
- strapedius
- posterior belly of digastric
What are the muscles of the 3rd pharyngeal arch?
Stylopharyngeus
What are the muscles of the 4th pharyngeal arch?
- All muscles of the pharynx except stylopharyngeus
- All muscles of the palaye except tensor veli palatini
- Cricothyroid
What are the muscles of the 6th pharyngeal arch?
All the muscles of the larynx
What are the skeletal features of the 1st pharyngeal arch?
- Maxilla
- Zygomatic bone
- mandible
- malleus
- incus
- meckel’s cartilage
What are the skeletal features of the 2nd pharyngeal arch?
- Stapes
- styloid process
- stylohyoid ligament
- lessor horn of hyoid
- upper part body of hyoid
What are the skeletal features of the 3rd pharyngeal arch?
- Greater horn of hyoid
- lower part body of hyoid
What are the skeletal features of the 4th and 6th pharyngeal arch?
- Epiglottis
- Laryngeal cartilages
- Thyroid
- Cuneiform
- Corniculate
- Arytenoids
What nerves are derived from the 1st pharyngeal arch?
- Skin of face supplied by V1, V2 and V3
- Trigeminal V3 - muscles of mastication
What arteries are derived from the 1st pharyngeal arch?
Part of the maxillary
What nerve is derived from the 2nd pharyngeal arch?
Facial Nerve
What arteries are derived from the 2nd pharyngeal arch?
hyoid and stapedial arteries
What nerve is derived from the 3rd pharyngeal arch?
Glossopharyngeal
What arteries are derived from the 3rd pharyngeal arch?
common carotid arteries and proximal internal carotid
What nerves are derived from the 4th and 6th pharyngeal arches?
- vagus - superior laryngeal branche supplies the 4th arch
- recurrent laryngeal supplies the 6th arch
