URS Flashcards

What are the two main types of tooth implantation in squamates?

Pleurodont and acrodont

What is pleurodont implantation?

Teeth are attached to the pleura (i.e., medial side of the parapet or labial ridge of the tooth-bearing bone)

What is acrodont implantation?

Teeth are attached to apical margin of the bone

What type of tooth implantation has been accepted as the ancestral state for Squamata and the total clade Lepidosauria?

Pleurodont

The teeth of pleurodont reptiles are continuously replaced. What are the two main modes based on the position of the replacement tooth and the resorption pits?

Replacement on the lingual side and replacement on the posterior end of the tooth

What pleurodont reptiles have continuous replacement of teeth on the lingual side?

Iguanians and gekkotans

What pleurodont reptiles have continuous replacement of teeth on the posterior end of the tooth?

Varanoideans, monstersaurians

What are supernumerary teeth, and other dental anomalies, likely the result of?

Disruptions (upregulation) to the SHH, Wnt, FGF, and/or BMP signaling pathways during development in the dental epithelium

What does Wnt stand for?

Wingless-related

What do Wnt (wingless-related) proteins form?

A large family of secreted ligands that can activate a number of intracellular signaling pathways

What does SHH stand for?

Sonic hedgehog

What are SHH signals?

Additional signals produced by the dental epithelial cells during the first phases of the thickening of the dental lamina in the enamel knot, and by the ameloblast progenitor cells

Explain what the SHH receptor is and how it works

Patch is a multipass protein largely expressed in the dental mesenchyme, totally absent in the epithelium

What does the highly localized presence of the SHH receptor Patch in the dental mesenchyme suggest?

That they are involved in the regulation of the dental bud assessment

What is SHH indispensable for?

Dental placodes

What does FGF stand for?

Fibroblast growth factor

What does BMP stand for?

Bone morphogenetic protein

What is BMP?

Belong to the TGFB family, and are expressed widely between the epithelium and mesenchyme in the developing tooth germs

Explain what the dental epithelium does

A cell type that is derived from the ectoderm and forms the outer layer of the tooth. Interacts with the mesenchyme to form the tooth structure, with the epithelium generating enamel and the mesenchyme producing dentin. The interaction between these two cell types is essential for the proper development and function of the tooth

Explain what the dental mesenchyme does

A cell type that is derived from the neural crest and forms the inner layer of the tooth. Interacts with the epithelium to form the tooth structure, with the epithelium generating enamel and the mesenchyme producing dentin. The interaction between these two cell types is essential for the proper development and function of the tooth

What is the dental lamina?

A band of epithelial tissue seen in histologic sections of a developing tooth

What is an enamel knot?

Transient signaling center in the developing tooth that regulates cusp formation and tooth morphogenesis

What are ameloblast progenitor cells?

Specialized cells responsible for the formation of tooth enamel

What is a multipass protein?

An integral membrane protein that spans the lipid bilayer multiple times

What are dental placodes?

Dynamic signaling centers that coordinate interactions between the epithelium and the underlying mesenchyme, leading to the formation of fully functional teeth

What is the TGFB family of proteins and what do they do?

Transforming growth factor beta superfamily. They are a group of structurally related cell regulatory proteins which play crucial roles in cell growth, differentiation, and tissue homeostasis. Involved in regulation of growth, development, and immune responses

What are fibroblasts?

Specialized cells in connective tissue that produce collagen and the extracellular matrix, forming the structural framework of tissues and playing a key role in wound healing