Hidradenitis Suppurativa
Sweat glands are also called sudoriferous glands and are usually found all over the body. The two types are eccrine and apocrine.

Eccrine sweat glands are a simple coiled tube connected by a single duct to the surface. In dogs these are only found in deep layers of fat and in the footpads.
Apocrine sweat glands are also coiled with a single duct as eccrine, but their empty into hair follicles instead of the surface of the skin directly. Dogs with long hair have more of these in their external ear canal than dogs with short hair so they have a higher chance of developing otitis externa, or an outer ear infection (infection of the ear canal).

Which type of sweat gland is this picture and what would have to be there for it to be the other type?