Structure of a Section through the Skin

A cross section through the skin reveals it’s comprised mainly of two layers: the epidermis on the outer side and the dermis beneath it. Below the dermis is a layer of subcutaneous fat, also known as the hypodermis.
The Epidermis: It is the outermost layer of the skin, providing a waterproof barrier and protecting the body from harmful substances. It is mainly made up of cells called keratinocytes, which produce a substance called keratin, a protein that offers protection against physical abrasion and harmful microorganisms.
The Dermis: Located beneath the epidermis, it is much thicker and contains collagen and elastin fibres that provide the skin with its flexibility and strength. It is here you’ll find hair follicles, sweat glands, sebaceous (oil) glands, blood vessels, lymph vessels, and nerves.
The Hypodermis: This layer is primarily composed of adipose tissue (fat cells) which insulate the body by trapping heat. It also provides a protective padding and a reserve of calories in case of food shortage. It is this layer that determines the thickness of the skin.
Some additional structures include Melanocytes, which are in the epidermis and produce melanin, a pigment that protects the skin from UV radiation. In the dermis, you’ll also find the endings of sensory neurons which respond to touch, pressure, pain, and temperature.
One must consider the role of sweat glands in homeostasis (maintaining a stable internal environment). Sweat glands produce sweat, which helps to keep the body cool when it becomes warm.
Sebaceous glands are connected to the hair follicles and they produce an oily substance called sebum, which keeps the skin supple and prevents it from drying out.
The ratio of the different structures can vary across the body. For example, the skin on your face has a higher density of sebaceous glands, while the skin on your palms and soles lacks hair follicles.
Blood vessels are vitally important in the skin. They transport nutrients and oxygen to the skin and help to control body temperature. When you’re hot, the blood vessels dilate (vasodilation) to bring more blood to the surface of the skin to increase heat loss. When you’re cold, they constrict (vasoconstriction) to conserve body heat.
Remember that deeper in the skin, you can also find sensory receptors for touch, pain, and temperature that send signals to the brain about the outside environment.