Skin histology

The skin covers and helps protect the body from its environment.

It’s also known as the integument, which is part of the integumentary system.

The integumentary system also consists of structures that are derivatives of the skin, such as nails, hair, and glands within the skin, like sweat glands.

The skin can be split into two general types: thick skin and thin skin.

Thick skin has a much thicker outer layer of epidermis that helps to protect the body in places where it’s regularly exposed to slightly harsher physical conditions.

That’s why it’s typically found in places such as the palms of the hands and soles of the feet.

Thick skin can also be differentiated from thin skin because it doesn’t have hair follicles or oil-producing glands called sebaceous glands.

It does still contain sweat glands though.

The overall thickness is often more than 5mm, whereas thin skin is typically only between 1-2mm thick.

Thin skin has all the same structures as thick skin except it has a thinner epidermis and additional structures such as hair follicles and sebaceous glands.

If we compare histologic images of thick skin and thin skin at low magnification, we can see the three main layers that make up the skin.

At the top of the image is the surface epidermal layer or epidermis that’s significantly thicker in thick skin.

Hair follicles are only found in thin skin, and as we can see in this image, they’re located in the middle layer called the dermis or dermal layer.

The third and deepest layer is called the hypodermis, which consists mainly of adipose and loose connective tissue, although this image of thick skin doesn’t include the hypodermis.

Now, if we look at just the epidermis, there are sub-layers that make up the epidermis.

Starting from the base of the skin is the stratum basalis, spinosum, granulosum, lucidum, and corneum at the surface.

The Stratum Lucidum can only be seen histologically in very thick skin.

If we take a closer look at the epidermis of both thick skin and thin skin, we can see that the stratum basalis is only a single-layer of cuboidal or columnar germ cells.

These cells are attached to a basement membrane that’s normally too thin to see under the microscope.

These cells have a high level of mitotic activity, dividing to produce all the cells that migrate up to the surface of the skin.