and the cutaneous nerves that supply the skin.
The subcutaneous layer, also called the hypodermis, is a layer of variable thickness that ranges
from a thin layer of loose connective tissue to a
Subcutaneous layer of integument
Subcutaneous adipose tissue (left), adipose cell (callout)
Section of subcutaneous layer, 200x and 640x
Superfi cial veins and cutaneous nerves in the subcutaneous layer
Step dissection of antebracial integument, anterior view
11 Fat storage vacuole of adipose cell
Th e skeletal system forms the internal framework
for the soft tissues of the body. Th is is not a static framework, but a highly dynamic
internal scaff olding. It is dynamic in many ways. On one hand, because of its jointed
design, it shows extreme fl exibility of movement when acted upon by muscles.
At another extreme, the cells of skeletal tissue are constantly monitoring and
changing the micro-structure of this amazing tissue called bone, providing
the body. Th is dynamic framework also exhibits a tremendous capacity
for growth and repair. It is a storehouse of calcium ions, ions that play a
signifi cant role in many of the body’s functions.
bones. Th ese bones range in size from the small ear ossicles measuring
appendicular skeleton. Th e axial skeleton includes the cranium, vertebral column,
ribs, and sternum. Th e appendicular skeleton consists of the bones of the limbs and
their girdles. Th e individual bones of the skeleton come in a variety of shapes. Some are
long and tubular, while others have the spread-winged appearance of a butterfl y. Bones
can be grouped into four shape categories. Although not that meaningful, the four
categories descriptively group the bones. Th e four shape categories are: long bones,
this hollow tubular region. Th e short, fl at, and irregular bones are similar
in having outer plates of compact bone surrounding internal centers of
spongy bone. In general, long bones and short bones are found in the
appendicular skeleton, while fl at bones and irregular bones occur in
the axial skeleton. In the right hands, the skeleton can be a library of
information. Its markings, foramina, landmarks, and canals each tell a
story about the soft tissues of the body. A strong foundation of skeletal
anatomy is an important starting point in understanding anatomy.
Th is chapter covers bone tissue and the general structure of bones and
and blood vessels in circular arrangements called osteons.
The tissue bone has two general forms — trabecular or spongy bone and compact bone.
Trabecular bone is an internal bone that always resides deep to the more dense compact
bone. Like its name implies, trabecular bone has many small beams of bone tissue conBone Tissue
Anterior view, proximal half frontal section
Compact bone and callout of osteon
Transverse section, 100x and 400x
radiograph and are a clear indication that the individual is still growing.
or by developing within mesenchymal connective tissue
10 Zone of hypertrophied cartilage
11 Zone of proliferating cartilage
Radiograph of the wrist region of a child
The bones of the skeleton come in a variety of sizes and shapes. The form of each bone
emerges from its position and functional role in the skeletal system. In an effort to classify
the different bones of the body anatomists defi ne four general categories of bones based
illustrate the basic parts and features of a long bone.
All bones share basic features in common. Compact bone tissue
forms all the visible outer surface of the bone and can vary from a
paper-thin covering to a thick wall of bone. Trabecular bone tissue
page, and the page that follows depict changes in the skeleton from a newborn to an adult.
The fi rst appearance of the skeletal elements arises during the second month of embryonic life
when connective tissue and cartilage precursors to the bones arise. Slowly through fetal life,
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