Forensic Pathology for Police - Brainshare Public Online Library

Specific Organ Systems 93
functions. In fact, the skin is the largest organ system in our bodies and the term
“cutaneous” is sometimes used to describe it. Grossly, we are all familiar with skin.
There are different types of skin: thick skin occurs on the palms of the hands and
the soles of the feet and hair-bearing skin occurs in many locations, particularly on
the scalp, in the axilla (armpit), and in the groin region, but also in other locations,
with some differences between male and female hair growth patterns.
Microscopically, skin has two basic parts, separated by a basement membrane.
The most superficial (close to the surface) part is called the “epidermis” which is
an epithelial surface made-up of multiple layers of squamous cells referred to as
keratinocytes. At the very upper surface of the skin, the keratinocytes convert into
a protective layer of keratin. Skin cells are constantly growing, with lower layers of
cells (just above the basement membrane) moving upward, becoming keratinized,
and then sloughing-off. The epidermis also contains various other cells, including
melanocytes, which produce melanin pigment, which is responsible for giving skin
its pigmentation.
Underneath the epidermis is the “dermis.” This contains connective tissue (collagen,
elastin, etc.), blood vessels, nerve fibers and sensing devices, and structures
referred to as the skin “adnexa,” which are actually parts of the epidermis that have
grown downward into the dermis. The adnexal structures include things like hair
follicles, sweat glands, and other glands. The “subcutis” refers to the soft tissues
(primarily fat, or adipose, tissue) that underlie the dermis. Strictly speaking, this is
distinct from the skin, and it is frequently referred to as “subcutaneous tissue.” It can
be thought of as an interface between the overlying skin and the underlying musculoskeletal
tissues. Figure 6.1 shows the microscopic appearance of the epidermis
and part of the underlying dermis.
Fig. 6.1 A high-power microscopic view of the skin
The skin carries out many important functions. It is a protective barrier against
all sorts of external elements (sun, germs, toxins, other injurious agents) and it