fiber bundles that have a high tensile strength in order to attach muscles to bones
(tendons) and to hold bones together at their joints (ligaments).Cartilageis a strong
but yet flexible support material consisting of collagenous fibers and a
protein-carbohydrate complex called chondrin. Cartilage provides support in
locations such as the nose, the ears, the rings that reinforce the windpipe, and the
cushioning discs between vertebrae.Boneis a combination of mineralized con-
nective tissue andflexible collagen that supports the body of most vertebrates. The
interior of bones contains a spongy tissue calledmarrow.Bloodis categorized as a
connective tissue because, like other connective tissues, it has an extensive extra-
cellular matrix. This matrix is in the form of a liquid calledplasma. This liquid has
red blood cells, white blood cells, and platelets suspended in it. Red blood cells
carry oxygen throughout the body, white blood cells act against invaders such as
bacteria and viruses, and platelets are involved in the clotting of blood.
Muscle tissueis composed of long, excitable cells that are capable of consid-
erable contraction. The three main types are skeletal muscles (which are responsible
for voluntary movements of the body), cardiac muscles (which form the contractile
walls of the heart), and visceral muscles (which are in the walls of the digestive
tract, bladder, arteries, and other internal organs).
Nervous tissuesare the cells that make up the central and the peripheral nervous
systems. The neural tissue in the central nervous system forms the brain and spinal
cord. In the peripheral nervous system, the neural tissue forms the cranial nerves
and spinal nerves.
In humans and most animals, a number of specialized functional units called
organsare composed of multiple layers of different types of biological tissues. In the
human body there are over 70 organs that have various sizes and functions. Some of
the major organs include the bladder, brain, eyes, heart, kidneys, liver, lungs, skin,
spleen, stomach, and thyroid. As an example of layers and their functions, the human
stomach consists of an arrangement of four tissue layers. From the inner to the outer
layer these are a thick epithelium that secrets mucous and digestive juices, a layer of
connective tissue followed by a layer of smooth muscle, andfinally another layer of
connective tissue. A collection of certain organs that carry out a specific function is
called anorgan system. These include the digestive, cardiovascular, muscular,
skeletal, nervous, respiratory, endocrine, and lymphatic systems.
1.7 Summary
Biophotonics technology deals with the interaction between light and biological
matter. The techniques and tools used in this discipline have become indispensable
for basic life sciences research and for biomedical diagnosis, therapy, monitoring,
and surgery. Among the diverse applications are biomedical imaging techniques,
microscopic and spectroscopic procedures, endoscopy, tissue pathology, bloodflow
monitoring, light therapy, biosensing, laser surgery, dentistry, and health status
monitoring.
20 1 Overview of Biophotonics