Development of pharyngeal arches Flashcards
What are the layers of the pharyngeal arches
- Mesoderm core
- Ectoderm
- Endoderm
What does the mesenchyme core come from?
Mesoderm an neural crest
What forms the pharyngeal clefts?
Ectoderm
What forms the pharyngeal pouches?
Endoderm
What are somitomeres?
- Ill defined segments of paraxial mesoderm
* Rostral to the somites
Paraxial mesoderm migration
- Migrates into the pharyngeal arches
* Forms mostly muscle tissue in the head
What are ectodermal placodes?
thickening of ectoderm that help give rise to sensory neurones/ganglia
What musculature forms from the first arch?
- Muscles of mastication
- Anterior belly of digastric
- Tensor tympani
- Tensor veli palatini
What musculature forms from the second arch?
- Muscles of Facial expression
- Stylohyoid
- Stapedius
- Posterior belly of digastric
What muscles form from the third arch?
Stylopharyngeus
What muscles form from the fourth arch?
- All muscles of pharynx apart from stylopharyngeus
- All muscles of the palate except tensor veli palatini
- Cricothyroid
What muscles form from the sixth arch?
All muscles of the larynx
What do major blood vessels form from?
Paraxial mesoderm
What is the origin of the ganglia
Neural crest and/or ectodermal placodes
What do the motor elements of cranial nerves form from?
Originates from the CNS
Nerves from 1st arch
• Trigeminal: opthalmic, maxillary, mandibular
Nerves 2nd arch
Facial nerve
Nerve 3rd arch
Glossopharyngeal
Nerve 4th and 6th arch
Vagus
What forms the cartilaginous elements in arches 1,2,3?
From the neural crest cells for the first 3 arches
Bones formed from the first arch
• Maxilla • Zygomatic bone • Mandible • Malleus • Incus (• Formed from meckel's cartilage)
Bones formed from the second arch
- Stapes
- Styloid process
- Lesser horn of hyoid
- Upper part of body of hyoid
Bones formed from the third arch
- Greater horn of hyoid
* Lower part of body of hyoid
Bone formed from the fourth and sixth arch
- Epiglottis
- Laryngeal cartilages
- Thyroid
- Cuneiform
- Corniculate
- Arytenoids
Artery of the first arch
maxillary
Arteries of the second arch
- Hyoid artery
* Stapedial artery
Arteries of third arch
- Common carotid
* Proximal internal carotid
Arteries of the fourth arch
- Aortic arch
* Subclavian artery
Arteries of the sixth arch
- Pulmonary arteries
* Ductus arteriosus
What forms from the paraxial mesoderm?
- All voluntary muscles
- Arteries
- neurocranium
- Meninges
- Dorsal skin
What forms from the lateral plate mesoderm?
- Laryngeal cartilages
* Regional connective tissue
What forms from the neural crest?
- Pharyngeal arch skeleton
- Viscerocranium
- Glandular connective tissue
- Parts of neurocrnaium
- Teeth
- Interacts with ectodermal placodes for ganglia/sensory nerve formation
What forms from the ectodermal placodes?
- Interact with the neural crest cells to form the neurones of sensory ganglia (V, VII, IX and X)
- Sensory apparatus
