Figure 1.

Hierarchical structure of the pancreatic islet. A: Human islets reside in the pancreas as sparse “islands” of endocrine cells embedded within exocrine tissue. Blood vessels supply individual islets with glucose and collect secreted hormones to send throughout the body. The most common cell type within the islet is the β-cell, responsible for secreting insulin when glucose levels are elevated following a meal. Insulin travels with glucose in the bloodstream to cells of the body, allowing those cells to take in the glucose. B: Blood vessels penetrating into human islets form a double basement membrane with the islet cells, comprised of membrane-bound integrins that link the actin within the β-cells to a network of ECM proteins. Integrins are depicted binding laminins, which form a trimeric branching network that connects to tetrameric collagen type IV networks via bridging molecules such as nidogen.