EPIDERMIS

The outermost layer of the skin, which is composed of squamous cells. This layer includes two distinct types: thick skin and thin skin.

The epidermis is composed of five sublayers:

Stratum corneum: The top layer of dead, extremely flat cells. Cell nuclei are not visible.
Stratum lucidum: A thin, flattened layer of dead cells. Not visible in thin skin.
Stratum granulosum: A layer of rectangular cells that become increasingly flattened as they move to the surface of the epidermis.
Stratum spinosum: A layer of polyhedral-shaped cells that flatten as they get closer to the stratum granulosum.
Stratum basale: The innermost layer of elongated column-shaped cells. It consists of basal cells that produce new skin cells.

DERMIS

The thickest layer of the skin, which lies beneath and supports the epidermis. The main cells in the dermis are fibroblasts, which generate connective tissue as well as the extracellular matrix that exists between the epidermis and the dermis.

The dermis also contains specialized cells that help regulate temperature, fight infection, store water, and supply blood and nutrients to the skin. Other specialized cells of the dermis help in the detection of sensations and give strength and flexibility to the skin. Components of the dermis include:

HYPODERMIS

The innermost layer of the skin, which helps insulate the body and cushion internal organs. Composed of fat and loose connective tissue, this layer of the skin insulates the body and cushions and protects internal organs and bones from injury. The hypodermis also connects the skin to underlying tissues through collagen, elastin, and reticular fibers that extend from the dermis.

A major component of the hypodermis is a type of specialized connective tissue called adipose tissue that stores excess energy as fat. Adipose tissue consists primarily of cells called adipocytes that are capable of storing fat droplets.