Anterior triangle embryology Flashcards
Contents of pharyngeal apparatus
- pharyngeal arches
- pharyngeal pouches
- pharyngeal grooves
- pharyngeal membranes
Pharyngeal arches
- supports gils in lower forms
- begin to develop at the lateral wall of the cranial end of the foregut (primordial pharynx) during 1st part of 4th week
- arches appear as rounded elevations containing cells of neurocrest
- pharynx widens cranially at the stomodeum and narrows inferiorly to continue with the esophagus
Stomodeum
-anterior end of foregut-site of future mouth
Each arch contains
- blood vessel-artery
- cartilage-forms the skeleton of the structures derived from the arch
- muscular component-gives rise to some of the muscles of head and neck
- nerve-supplies the muscosa and the muscles derived from the arch
First arch
- mandibular arch
- develops two prominences
- -maxillary prominence-gives rise to maxilla
- -mandibular prominence-gives rise to mandible
Muscles of arch one
-muscles of mastication, mylohyoid, anterior belly of digastric, tensor tympani & tensor veli palatini
Nerve of first arch
-CN V
Second arch
- known as hyoid arch
- major contribution to the formation of hyoid bone
Muscles of 2nd arch
-are the muscles of facial expresssion, stapedius, stylohyoid, and posterior belly of digastric
Nerve of 2nd arch
-CN VII
Third arch
- contributes to formation of hyoid bone
- one muscle belongs to this arch–stylopharyngeua muscle
Nerve of 3rd arch
-CN IX
Fourth arch
-contributes to the formation of the muscles and cartiliages of larynx
Nerve of 4th arch
-CN X
Pharyngeal membranes
- ectoderm of the grooves on the outside of the pharyngeal wall make contact with the endoderm of the pouchies on the inside to form the pharyngeal membranes
- the first membrane gives rise to the tympanic membrane of ear
- rest of membranes disappear
By the end of 4th week
- there are 4 pairs of well developed arches
- 5th and 6th arches never develop completely and are not visible from the outside
