Which type of tissue forms the outermost layer of the skin?

The epidermis is the correct choice as it is the outermost layer of the skin. This layer serves as the primary barrier between the body and the external environment. It is composed mainly of keratinized stratified squamous epithelium, which provides protection against physical damage, pathogens, and dehydration. Additionally, the epidermis plays a vital role in the regulation of water loss and the synthesis of vitamin D when exposed to sunlight.

Understanding the structure of the skin, the epidermis is differentiated from the dermis, which lies beneath it, providing the skin with strength and flexibility, as well as containing blood vessels and nerve endings. The hypodermis (or subcutaneous layer) is located below the dermis and primarily consists of fat and connective tissue that insulates the body and allows for a certain level of mobility in relation to the underlying structures. The endodermis, on the other hand, is a term primarily used in botany and does not pertain to human or animal anatomy. This context highlights the unique role of the epidermis in overall skin integrity and health.