Cardiac Muscle Tissue
The cardiac muscle cells are striated and are joined
end to end, resulting in a complex network of
interlocking cells (fig. 1-11). Cardiac muscles are
involuntary muscles and are located only in the heart.
These tissues are responsible for pumping blood
through the heart chambers and into certain blood
Nerve tissue is the most complex tissue in the
body. It is the substance of the brain, spinal cord, and
nerves. Nerve tissue requires more oxygen and
nutrients than any other body tissue. The basic cell of
the nerve tissue is the neuron (fig. 1-12). This highly
specialized cell receives stimuli from, and conducts
impulses to, all parts of the body.
organs and body systems are composed of two
or more kinds of tissue that perform specialized
functions within the body.
As a group of similar cells forms tissues, two or
more kinds of tissues grouped together and performing
specialized functions constitute an organ. Organs are
grouped together to form systems (such as the urinary
system, composed of the kidneys, ureters, bladder, and
THE SKELETAL SYSTEM
parts of bone and their functions.
The skeleton, the bony framework of the body, is
composed of 206 bones (fig. 1-13). It supports and
gives shape to the body; protects vital organs; and
provides sites of attachment for tendons, muscles, and
ligaments. The skeletal bones are joined members that
make muscle movement possible.
ANATOMY OF BONES
Osteology is the study of the structure of bone.
Bone is made up of inorganic mineral salts (calcium
and phosphorus being the most prevalent) and an
organic substance called ossein. If human bones were
soaked in dilute acid until all inorganic mineral salts
were washed out, all that would remain would be a
flexible piece of tissue that could be easily bent and
twisted. Inorganic mineral salts give bone its strength
Bone consists of a hard outer shell, called compact
bone, and an inner spongy, porous portion, called
cancellous tissue (fig. 1-14). In the center of the bone
is the medullary canal, which contains marrow.
There are two types of marrow, red and yellow. Yellow
marrow is ordinary bone marrow in which fat cells
predominate. It is found in the medullary canals and
cancellous tissue of long bones. Red marrow is one of
the manufacturing centers of red blood cells and is
found in the articular ends of long bones and in
At the ends of the long bones is a smooth, glossy
tissue that forms the joint surfaces. This tissue is called
articular cartilage because it articulates (or joins)
with, fits into, or moves in contact with similar
surfaces of other bones. The thin outer membrane
surrounding the bone is called the periosteum. An
important function of the periosteum is to supply
nourishment to the bone. Capillaries and blood vessels
run through the periosteum and dip into the bone
surface, supplying it with blood and nutrients. The
Figure 1-11.Cardiac muscle tissue.