Pharyngeal Arches Flashcards
What does our pharyngeal apparatus consist of?
Phargyngeal arches, pouches, grooves, clefts and membranes. They will make our. nasal cavities, mouth, larynx, pharynx and neck
Describe the relationship between pharyngeal cleft, pharyngeal arch and pharyngeal pouch.
Clefts (aka Grooves) are the ectodermal structures on the external surface of the pharyngeal arches.
Arches are the structures themselves, which give rise to an artery, a cartilage part, a muscular part, and a nervous part.
Pouches are the endodermal internal surface of the arch.
How do the pharyngeal arches develop
Early in week 4: NCC migrate to the future head and neck. Arches 1 and 2 develop at the same time. 1st pair of arches (primordial jaw) appear as elevations lateral to the pharynx Arches 2-4 appear as ridges on each side of the future neck and head. 5/6 are rudimentary: we cannot see them on the surface of the embryo. 5th arch may not develop
What does each arch. consist of?
Core. of mesenchyme (mesoderm and NCC) covered. externally. by ectoderm and internally. by. endoderm.
First arch separates into what?
maxillary. and mandibular prominence.
Week 5: PA2 overgrows PA3/4 -> forms cervical sinus (a depression of ectoderm) End of 7 week: cervical sinus diappears
What are the general roles of the NCC, the paraxial mesoderm, the lateral plate mesoderm, and the pharyngeal endoderm in the developing pharyngeal arches?
Neural crest cells: make the maxillary and mandibular prominences, as well as the CT, bone, skin, and smooth muscle.
Paraxial mesoderm is called the myogenic mesoderm, because it forms the muscle primordium in each arch.
Lateral plate mesoderm gives rise to angioblasts which form endothelium.
Pharyngeal endoderm plays a regulatory role
What does a typical pharyngeal arch consist of?
- An artery arises from truncus arteriosus of the primordial heart: goes around primordial pharynx -> dorsal aorta 2. Cartilaginous rod makes the makes the skeleton of the arch. 3. Muscular component becomes the muscles in the head and neck. Sensory. and motor nerves will supply the mucosa and muscles that come from each arch. Nerves are made in the brain and grow in to the arch.
What muscles come from the first arch?
What cranial nerve innervates them?
Muscles of mastication.
CN V (only maxillary and mandibular division)
- sensory for head and neck
- motor for mastication muscles
What muscles come from the second arch? What cranial nerve innervates them?
Stapedius and the muscles of facial expression.
CN VII
- Motor for #smileandsaycheese
What muscle comes from the third arch?
What cranial nerve innervates it?
elevateanddilate
Stylopharyngeus M
CN 9 (IX)
What muscles come from the fourth arch?
What cranial nerve innervates them?
pushitpushitrealgood
Cricothyroid, levator veli palatini and the constrictors of the pharynx.
CN X’
- 4th: superior laryngeal branch of CN X and its recurrent laryngeal N
What muscles come from the sixth arch?
What cranial nerve innervates them?
Intrinsic muscles of the larynx.
CN X
#soundoff
In the second arch, the muscles of facial expression come from_________, and the superior (ocular) muscles come from the __________.
paraxial mesoderm
prechordal mesoderm
What is Meckel’s cartilage?
What is it’s function?
The cartilage of pharyngeal arch 1.
Used as a model for osteoblasts to form the mandible. After the mandible is created, Meckel’s cartilgae will degenerate.
Also, two dorsal nodules break off and serve as a precursor from the malleus and incus.
What is formed from the perichondrium of Meckel’s cartilage?
- Anterior ligament of the malleus.
- Sphenomandibular ligament.
Both the malleus and incus are from
NCC
What forms the stylohyoid ligament?
Riechert’s cartilage from PA 2.
Where does Riechert’s cartilage come from, and what does it make?
Riechert’s cartilage comes from pharyngeal arch 2, and makes the stapes and styloid process of the temporal bone.
It also makes the lesser cornu of the hyoid, and the ligament in between its structures - the s_tylohyoid ligament._
What is formed by the cartilage of the third pharyngeal arch?
Greater cornu of the hyoid bone.
What forms the body of the hyoid bone?
Hypopharyngeal eminence (from PA 3 and PA 4)
What is formed by the fourth and sixth arch cartilages?
Laryngeal cartilages.
What forms the lesser cornu, greater cornu, and body of the hyoid?
Lesser cornu = Reichert’s cartilage (PA 2)
Greater Cornu = Third arch cartilage
Body of Hyoid = Hypopharyngeal eminence (PA 3 and PA 4)
- Distinguish between the neural crest and paraxial derived components of the
pharyngeal arches.
Muscles of the pharyngeal arches come from paraxial and prechordal mesoderm mesoderm.
The endothelium of the lateral plate come from lateral plate mesoderm.
Pharyngeal arch cartilages are neural crest derived.
Our primordial pharynx is derived from what>
foregut
