Final answer:
The outer layer of skin is called the epidermis, which is a barrier to water and pathogens and is made up of keratinocytes filled with keratin.
Step-by-step explanation:
The outer layer of skin is called the epidermis. The epidermis is the outermost layer of the skin in mammals and is responsible for providing a barrier against water and pathogens. It is composed of keratin-filled cells known as keratinocytes.
Beneath the epidermis lies the dermis, which is thicker and contains blood vessels, sweat glands, hair follicles, and sebaceous glands. Even deeper is the subcutaneous tissue, also known as the hypodermis, which is primarily made up of fat and connects the skin to underlying bone and muscle.