Head/Neck Development lecture Flashcards
What is the pharyngeal apparatus? How many arches are there?
- series of arches that develops in the lower face and in the visceral part of the neck
- remnants of gill arches of aquatic vertebrates
- 5 pairs of arches: 1,2,3,4,6
- 1st arch has 2 swellings
When do pharyngeal arches develop?
- 1st arch on day 22
- craniocaudal succession after than
- 6th and final arch by day 29
Each pharyngeal arch consists of a _________ core lined on the outside with _______ and inside with ______.
- mesenchymal core (mesoderm and neural crest ectoderm)
- ectoderm on outside
- endoderm on inside
Neural crest cells migrate into each arch and form __________. Where do they migrate from?
- cartilage
- midbrain and hindbrain regions
Pharyngeal arches are separated by ________ and all except _____ disappear. What is the remnant cleft(s)?
- pharyngeal clefts
- 1
- external auditory meatus
Name 3 things each pharyngeal arch contains.
- central cartilaginous skeletal element derived from neural crest cells
- striated muscle rudiments derived from head mesoderm innervated by an arch-specific cranial nerve
- aortic arch artery
The first pharyngeal arch has 2 prominences associated with it. Name them and what they contain.
- mandibular and maxillary prominences which give rise to the lower and upper part of the jaw, respectively
- each contain a central cartilaginous element
- central cartilage of maxillary prominence is palatopterygoiquadrate bar
- central cartilage of mandibular prominence is Meckel’s cartilage
Both the maxillary and mandibular prominences are formed largely from ________.
-neural crest cells that migrate from NC folds in midbrain and hindbrain
What bones does arch 1 give rise to?
- template for mandible and 2 ossicles: malleus and incus
- Merkel’s: malleus, sphenomandibular ligament, anterior ligament of the malleus
- Maxillary: incus and small bone called alisphenoid located in orbital wall
What is the second arch cartilage called? What bones does this arch give rise to?
- Reichert’s cartilage
- stapes of middle ear, styloid process of temporal bone, fibrous stylohyoid ligament, and the lesser horns (cornua) and upper rim of body of the hyoid bone
Where does the 3rd arch cartilage come from and what bones does this arch give rise to?
- caudal hindbrain
- forms rest of hyoid bone
What bones do the 4th and 6th arches give rise to?
-thyroid and cricoid cartilages and intrinsic laryngeal cartilages (larynx)
Where are the motoneuron cell bodies and sensory cell bodies of cranial nerves found?
- motor: cell bodies in the brain
- sensory: cranial nerve ganglia
In the trunk, all sensory nerves are derived from neural crest cells. What about some sensory neurons in the head?
-neural crest cells and special areas of ectoderm known as neurogenic ectodermal placodes
Skeletal muscles that develop in each arch is innervated by _________.
-a specific mixed cranial nerve
What provides sensory innervation of the face?
-ophthalmic, maxillary, and mandibular divisions of the trigeminal nerve
Which cranial nerves are associated with each arch?
- Arch I: CN V3
- Arch 2: CN VII
- Arch 3: CN IX
- Arch IV, VI: CN X
Give the muscles, skeletal elements, and cranial nerve from arch 1
- 4 muscles of mastication (masseter, temporalis, medial and later pterygoid), anterior belly of digastric, mylohyoid, 2 tensors (tensor tympani and tensor veli palatini)
- mandible, malleus, incus, sphenomandibular ligament
- V3
Give the muscles, skeletal elements, and cranial nerve from arch 2
- ocularis oculi, orbicular oris, buccinator, plastysma, digastric posterior belly, stylohyoid, stapedius
- hyoid (superior part), styloid process, stapes, stylohyoid ligament
- Facial nerve CN VII
What is the smallest muscle in the human body?
-stapedius
Give the muscles, skeletal elements, and cranial nerve from arch 3
- stylopharyngeus
- hyoid (inferior part)
- Glossopharyngeal n CN IX
Give muscles, skeletal elements, and cranial nerve from arch 4
- Pharyngeal branch of Vagus CN X: levator veli palantini, uvular muscle, 3 constrictors, salpingopharyngeus, palatoglossus, palatopharyngeus
- Superior laryngeal branch of Vagus CN X: cricoidthyroid muscle, thyroid cartilage and epiglottis
Give muscles, skeletal elements, and cranial nerve from arch 6
- recurrent branch of vagus CN X
- lateral cricoarytenoid, posterior cricoarytenoid, transverse arytenoid, oblique arytenoid, thyroarytenoid (vocalis), aryepiglottis
- cricoid, arytenoid, corniculate, cuneiform cartilages
What innervates muscles of palate and with what exception?
-Pharyngeal branches of X innervate all muscles of palate except tensor veli palatini which is innervated by V3
