Forensic Pathology for Police - Brainshare Public Online Library

94 6 Overview of Anatomy and Physiology
is an important aid in temperature and body water regulation. Various metabolic
processes, such as vitamin D metabolism, require sunlight via the skin. The skin is
also vital for various bodily functions that many of us take for granted, such as the
sense of touch and the ability to move and interact with others and our environment.
In the practice of forensic pathology, the skin is extremely important. Much
of what we refer to as the “external examination” portion of an autopsy involves
evaluation of the skin. We may use permanent features of the skin, such as pigment
characteristics, scars, and tattoos, in identifying a body. There are postmortem
changes that involve the skin, such as livor mortis or lividity (settling of blood),
and various decompositional changes. The skin is frequently the site of specific
injuries and its response to various injurious forces results in specific injury patterns.
Recognition of these patterns allows forensic pathologists to categorize the injury
into a specific type. Examples include blunt force injuries (abrasions, lacerations,
contusions), thermal injuries (burns), electrical injuries, gunshot wounds, etc.
Musculoskeletal System
Many textbooks consider the musculoskeletal system as two separate entities, the
muscular system and the skeletal system, but for this introductory presentation,
they will be considered together. The bones represent the skeletal component of
the musculoskeletal system. They provide support and protection for the rest of the
body, and they allow movement via the presence of moveable joints that separate
yet connect one bone to another. Bones are very active metabolically, particularly
when it comes to calcium metabolism; they also contain bone marrow, where
blood cells are produced. Certain specialized bones are necessary for our sense of
hearing.
From a gross standpoint, bones can be “long bones,” such as the bones of our
arms and legs, or they can be “flat bones,” such as the bones of our skull. The end
of a long bone is referred to as a metaphysis, the long central part is called the diaphysis,
and where the two connect is called the epiphysis (Fig. 6.2). It is within the
epiphysis (the epiphyseal plate) that long bone growth occurs during childhood and
into adolescence (Disc Image 6.3). In growing bones, the epiphyseal plates remain
“soft” and are evident grossly as well as by X-ray. However, once a bone stops
growing, the epiphyseal plates become calcified (hardened) and incorporated into
the rest of the bone. With certain flat bones, such as those that occur in the skull,
several bones actually fuse as a person grows older to form a single skull (the skull
is actually made up of frontal, temporal, parietal, occipital, sphenoid, ethmoid, and
other bones) (Fig. 6.3). Whether they are long bones or flat bones, a bone’s outer
solid, hard surface is referred to as the cortex (cortical bone), and the inner part of
a bone is referred to as medullary bone. Medullary bone is composed of a scaffoldlike
arrangement of thin but hard structures called trabeculae that surround the bone
marrow spaces. It is also called “spongy” bone, since it is reminiscent of what a
sponge looks like. Bone marrow (containing blood-producing cells and fat) fills the
spaces that exist within medullary bone.