Final answer:
The strength of adhesion between cells connected by cadherins is determined by calcium ion presence, interactions with cytoskeletal elements, mechanical forces, and the properties of the extracellular environment, as well as the structure of desmosomes that involve cadherins linking to intracellular proteins and the cytoskeleton.
Step-by-step explanation:
The strength of adhesion between opposing cells held together by cadherins is determined by several factors. These cadherins are crucial for forming adherens junctions, which are components of the cellular 'glue' that binds cells into cohesive tissues. The adhesion strength is impacted by the presence of calcium ions, as cadherins depend on calcium to function properly. Additionally, the interactions between cadherins and cytoskeletal elements, such as intermediate filaments and actin, are also vital. Mechanical forces at the cell-material interface active generate force, which in turn influences the strength of these cell-cell adhesions by promoting contact and structural integrity within tissue layers.
Adhesion is further influenced by desmosomes, which are specific types of adherens junctions. Belt desmosomes, or zonula adherens, encircle cells, binding them tightly to neighbors, while spot desmosomes, macula adherens, resemble rivets that fasten cells at particular points. Both types of desmosomes rely on cadherins which bridge the cell membranes and are anchored to intracellular plaque proteins that connect to the cytoskeleton. This structural setup promotes strong intercellular attachments.
Moreover, forces generated from the contraction of actin filaments and the mechanical properties of the cells' physical environment modulate adhesion. The contractile nature of cells, dependent on the rigidity of the surroundings, also contributes to the adhesive strength of cadherin-mediated junctions.