L11 - Pharyngeal Arches Flashcards
What structures characterize the head of the developing mammalian embryo?
Pharyngeal arches
Which layers are represented in pharyngeal arches but organized differently from the other body regions?
Germ Layers
- endoderm
- mesoderm
- ectoderm
How do monozygotic twins form?
Within the zona pellucida, we get the formation of:
- 2 blastocysts
The 2 blastocysts merge and we get 2 inner cell masses within 1 blastocyst.
The blastocyst divides as it emerges from the zona pellucida.
List 4 cellular responses that are induced by extracellular signals.
1) Morphological Changes of Cells
2) Division of cells
3) Apoptosis
4) Differentiation of Cells
What is paracrine signalling?
When one cell releases messenger molecules that act on another cell in the body.
What is autocrine signalling?
When one cell releases messenger molecules that act on itself.
What is contact-dependent signalling?
When two cells must have receptor-ligand contact to have an effect on each other.
What gives rise to the epidermis and it’s associated glands?
Surface Ectoderm
What develops into the CNS?
Neural Tube
What forms the neural tube?
Neuroectoderm
Which germ layer do neural crest cells arise from?
Ectoderm (Neuroectoderm)
What are neural crest cells?
Migratory cells that move to other parts of the body and give rise to a diverse cell lineage.
- melanocytes, cartilage, smooth muscle, bone etc.
What do neural crest cells mix with when they migrate to the pharyngeal arches and form head mesenchyme?
Mesoderm
What is the term for the process which permits migration of neural crest cells to different regions of the developing embryo?
Epithelial-mesenchymal transition (EMT)
What influences EMT (epithelial-mesenchymal transition) of neural crest cells?
EMT Effectors
List some EMT effectors.
Growth Factors
Cytokines
ECM
What is mesenchyme?
Mixture of mesoderm and neural crest cells
What are pharyngeal arches?
Six paired aggregations of mesenchyme on either side of the developing pharynx.
What is each pharyngeal arch covered by laterally?
Pharyngeal Cleft (Surface Ectoderm)
What is each pharyngeal arch covered by medially?
Pharyngeal pouch (Endoderm)
How are the three germ layers arranged for pharyngeal arches?
The surface ectoderm forms pharyngeal cleft on the lateral aspect of the arch.
The endoderm forms the pharyngeal pouch on the medial aspect of the arch.
The mesoderm combines with neural crest cells to form mesenchyme that makes the pharyngeal arch.
What is the direction of development of the pharyngeal arches?
Cranio-caudal
- Arch 1 appears first
Which pharyngeal arch disappears?
5
Which pharyngeal arches merge?
4 and 6
Which pharyngeal cleft expands over the clefts that are caudal to it?
2
Which pharyngeal cleft is the external auditory meatus derived from?
1
Which cranial nerve innervates the first pharyngeal arch?
Trigeminal (V)
Which cranial nerve innervates the second pharyngeal arch?
Facial (VII)
Which cranial nerve innervates the third pharyngeal arch?
Glossopharyngeal (IX)
Which cranial nerve innervates the fourth/sixth pharyngeal arch?
Vagus (X)
Which pharyngeal pouch are the auditory tube and guttural pouch derived from?
1
Which pharyngeal pouch are the palatine tonsils derived from?
2
Which pharyngeal pouch are the parathyroids III and stroma of thymus derived from?
3
Which pharyngeal pouch(s) are the parathyroids (IV) and stroma of thymus derived from?
4/6
Which pharyngeal arch are the constrictor muscles of the pharynx and intrinsic muscles of the larynx derived from?
4/6
Which pharyngeal arch are the muscles of facial expression and the caudal belly of the digastricus derived from?
2
Which pharyngeal arch is the stylopharyngeus muscle derived from?
3
Which pharyngeal arch are the muscles of mastication. mylohyoid and rostral belly of the digastricus derived from?
1
Which pharyngeal arch are the mandible, maxilla, auricle, malleus and incus bones derived from?
1
Which pharyngeal arch are some parts of the hyoid bone derived from?
3
Which pharyngeal arch are the auricle of the ear, stapes and majority of the hyoid apparatus derived from?
2
Which pharyngeal arch are the cartilages of the larynx derived from?
4/6
