The integumentary system encompasses the skin and its appendages. The skin, or cutis, covers the entirety of the body’s exterior surface. The skin is divided into two layers that differ in function, histological appearance, and embryological origin. 

The epidermis, or outer layer, is generated by an epithelium of ectodermal origin. The thicker dermis layer beneath is composed of connective tissue and arises from the mesoderm. Below these two layers is a subcutaneous layer of loose connective tissue called the hypodermis, which connects the skin to the underlying structures. Hair, nails, sweat, and sebaceous glands are all epithelial in origin and generally referred to as the skin’s appendages. 

Sebaceous glands secrete their secretory product into the hair follicles’ higher regions. As a result, they are located in areas of the skin with hair. Sebaceous glands are also present in several body parts that lack hair, such as the lips, oral surfaces of the cheeks, and external genitalia.

Hair is an integumentary system component that extends downward into the dermal layer, which is contained in the hair follicle. Each hair is fixed at its root in a tubular invagination of the epidermis called a hair follicle, which extends into the dermis and, in most cases, a short distance into the hypodermis.

References
Integumentary system. Physiopedia. (n.d.). Retrieved from https://www.physio-pedia.com/Integumentary_System
Slomianka, L. (n.d.). Blue histology – integumentary system. Retrieved from http://lecannabiculteur.free.fr/SITES/UNIV%20W.AUSTRALIA/mb140/CorePages/Integumentary/Integum.htm