Which connective tissue layer is discussed in the chapter on the integumentary system but is truly not a part of it

Hypodermis layer.

Explanation:

Hypodermis layer is connective tissue layer that is present on the integumentary system but it is not part of integumentary system. This Hypodermis layer is a fatty layer that connects the skin to our body, its only function is to attach the skin with the body. The integumentary system refers to an organ system which made outermost part of the body that consist of skin, hair, nails, and exocrine glands around which hypodermis layer is present.

option c is the correct answer.

not only is it colder, it also becomes darker, less salty, and more dense.