The basal layer refers to which part of the body?

The basal layer specifically refers to a fundamental component of the skin known as the basal cell layer, which is the lower layer of the epidermis. This layer is vital as it consists of cells that continuously divide and push older cells towards the surface, where they eventually die and shed. The basal layer is responsible for producing new skin cells, thus playing an essential role in the skin's overall health and regeneration.

The other options pertain to different types of tissue in the body. Muscle tissue is responsible for movement, nervous tissue deals with transmitting signals throughout the body, and connective tissue serves to support and bind other tissues together. Each of these has distinct functions and structures that do not relate to the specific function of the basal layer within the skin.