Your Dog's Skin
The skin contains your dog's body. It protects the internal organs, bones, and joints from injury and prevents harmful organisms from entering the body. Although it does serve a protective purpose, canine skin is thin and sensitive, more susceptible to damage than human skin. That's one of the reasons it has a protective covering of fur. Skin consists of three layers: the epidermis, the dermis, and the subcutis.
The epidermis is the outer layer, which you can see beneath the fur. Some parts of the epidermis are delicate and sensitive, such as the groin or the area where the legs meet the body. Tougher, thicker sections of epidermis cover the nose and paw pads. The epidermis contains cells that produce keratin, a protein that's a major component of skin, hair, and toenails; melanin, which gives skin its color; and cells that help the skin generate immune responses.
If your dog has a bare belly — or if you have a hairless dog — you can see what color his skin is. It's usually pink or light brown, sometimes with black spots.
The middle and thickest layer of the skin is called the dermis. It consists mainly of collagen fibers, with some elastic fibers to keep the skin supple. Among the cell types found in the dermis are mast cells, which help control inflammation. Also part of the dermis are the epidermal appendages: hair follicles, which produce hair; sebaceous glands, which secrete sebum, an oily substance that helps lubricate the skin and coat; and sweat glands. Dogs have two types of sweat glands. The apocrine sweat glands, found throughout the body, produce a scented fluid that may play a role in sexual attraction. The eccrine sweat glands, located in the paw pads and the nasal pad, help dogs regulate their body temperature.
Supporting the dermis and the epidermis is the subcutis, which is also known as the hypodermis. It's made up of fat cells and connective tissue, through which nerves and blood vessels supply the skin.