Pharyngeal arches Flashcards
What are the pharyngeal arches?
Developmental structures in embryonic development.
What week of development do they arise?
4th
How many arches are there?
Pairs 1-4
Pair 6
There is no 5th arch
Is there a 5th arch?
No
How do the arches form?
Endoderm outpouches from the foregut and comes into contact with the ectoderm. Neural crest cells migrate from the neural tube into the mesoderm (inbetween outpouchings)
What does the pharyngeal cleft consist of?
Ectoderm
What does the pharyngeal pouch consist of?
Endoderm
What does the mesenchymal core core consist of?
Mesoderm and neural crest cells.
What does each branchial arch give rise to?
Rod of cartilage
Muscles
Cranial nerve
Artery (aortic arch)
What genes pattern the rostral-caudal axis?
Hox genes
What genes pattern the dorsal-vental axis?
DLX genes
What is the embryonic origin of the viscerocranium (and frontal, temporal and sphenoid)?
Neural crest
What is the embryonic origin of the neurocranium (occipital and parietal)?
Paraxial mesoderm
What are the two processes of the first arch?
Maxillary swelling (becomes maxillar) Mandibular swelling (becomes mandible)
Which arch forms two processes?
1st
How do the maxillar and mandible bones form (what type of bone growth)?
Perichondral ossification
What is perichondral ossification?
The bones form by intramembranous ossification (dermal bone), but they are preceded by transient cartilage elements in the swellings, the surface of a cartilage element (perichondrium) becomes a periosteum, without replacement of cartilage.
What cartilage precedes the mandible?
Meckel’s cartilage
What cartilage template does the maxilla use?
Palatopterygoquadrate bar
What arch forms the frontonasal prominence?
1st
How does the nose form?
Medial nasal processes fuse to from the intermaxillary process.
Lateral nasal processes give rise to the side of the nose and fuse with the maxillary process from cheeks.
Which arch forms the muscles of mastication?
1st
Which nerve(s) innervates the mandibular and maxillary processes of the first arch?
The mandibular and maxillary branches of the trigeminal (V) nerve.
The mandibular nerve innervates the cranial side, and chrorda tympani (branch of facial) innervates caudal side.
Which arch has double innervation?
1st
What does the second arch contribute to?
Hyoid, styloid process and the stapes
What is the term for the cartilage in the second arch?
Reichert’s cartilage
What part of Reicherts cartilage ossifies to become the stapes?
Dorsal ends
What part of Reicherts cartilage ossifies to form the upper hyoid?
Ventral portion
What does the perichondrium between hyoid and styloid form?
Stylohyoid ligament
What innervates the second arch, what does it supply?
Facial (VII) nerve, motor to face muscles, sensory taste in anterior tongue
What does the third arch contribute to?
Hyoid, Stylopharyngeus muscle
What arches neural crest gives rise to laryngeal cartilages (thyroid and cricoid)?
4th and 6th
What muscles do the 4th arch contribute to?
Pharyngeal
What muscles do the 6th arch contribute to?
Laryngeal
What nerve is associated with the 3rd arch?
Glossopharyngeal (IX)
What nerve is associated with the 4th arch?
Vagus (X)
What nerve(s) is associated with the 6th arch?
Accessory (X and XI)
What does the cleft between the 1st and 2nd arch form?
External ear
What happens to other clefts (not first)?
Overgrown by the second arch
What leads to the formation of a branchial cyst?
Cleft tissue fails to dissapear, can open to the surface, called a fistula
What do the pouches form?
1st: middle ear and auditory tube
2nd: tonsils
3rd: thymus and inferior thyroid
4th: superior parathyroid and ultimo-branchial body
How does the tongue form?
From swellings on pouches 1-3
What innervates the sensory component of the tongue?
Anterior 2/3 = trigeminal
Taste anterior 2/3 = Facial
Posterior 1/3 = glossopharyngeal
What is the motor innervation for the tongue?
Hypoglossal and somatic intrinsic muscles
The first pharyngeal pouch forms the…
Pharyngo-tympanic tube
