Final answer:
Attachment sites in biology are areas where different structures connect. They can be observed in the human body where tendons and ligaments attach to projection bone markings, as well as in microscopic images.
Step-by-step explanation:
Attachment sites refer to areas where two different structures are connected. In biology, attachment sites are often found in the human body, where tendons and ligaments attach to projection bone markings. For example, in the posterior view of the skull, attachment sites can be seen for the muscles and joints that support the skull. Attachment sites can also be observed in microscopic images, such as the electron micrograph of an in-dwelling catheter, which shows bacteria attached to the layers of extracellular substrate.