Biological tissue
Biological tissue is a collection of interconnected
cells that perform a similar function within an organism.
The study of tissues is known as
histology, or, in connection with disease,
histopathology.
The classical tools for studying the tissues are the
wax block, the
tissue stain, and the
optical microscope, though developments in
electron microscopy,
immunofluorescence, and frozen sections have all added to the sum of knowledge in the last couple of decades.
With these tools, the classical appearances of the tissues can be examined in health and disease, enabling considerable refinement of clinical diagnosis and prognosis.
There are four basic types of tissue in the body of all
animals, including the human body and lower
multicellular organisms such as
insects. These compose all the organs, structures and other contents.
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Epithelium - Tissues composed of layers of cells that cover organ surfaces such as surface of the skin and inner lining of digestive tract. The tissues serve for protection, secretion, and absorption.
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Connective tissue - As the name suggests, connective tissue holds everything together.
Blood is considered a connective tissue. These tissues contain extensive
extracellular matrix.
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Muscle tissue - Muscle cells contain contractile filaments that move past each other and change the size of the cell. Muscle tissue also is separated into three distinct categories: visceral or
smooth muscle, which is found in the inner linings of organs;
skeletal muscle, which is found attached to bone in order for mobility to take place; and
cardiac muscle which is found in the heart.
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Nervous tissue - Cells forming the
brain,
spinal cord and
peripheral nervous system.
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Areolar connective tissue - A pliable, mesh-like
tissue with a
fluid matrix that funtions to cushion and protect body
organs.
Examples of tissue in other
multicellular organisms are
vascular tissue in
plants, such as
xylem and
phloem. Plant tissues are categorized broadly into three tissue systems: the
epidermis, the
ground tissue, and the
vascular tissue. Together they are often referred to as
biomass.
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Epidermis - Cells forming the outer surface of the
leaves and of the young plant body.
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Vascular tissue - The primary components of vascular tissue are the
xylem and
phloem. These two tissues transport fluid and nutrients internally.
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Ground tissue - Ground tissue is less
differentiated than other tissues. Ground tissue manufactures nutrients by
photosynthesis and stores reserve nutrients.
In
science fiction and
cyberpunk genres, biological tissue makes up part or components of
bioengineered and composite organisms such as
cybernetic organisms (cyborgs,
biomechanoids and
bioships). It may also be considered a material for creating
constructed beings and
androids. Examples of cyborgs include
RoboCop (cyborg with human parts) and
T-800 (cyborg with biological skin). Advanced machines may, however, take on a biological appearance, or act organically, without being made of biological tissue. Tissue with inert technology embedded within cells may be called
techno-organic material.
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Cellular differentiation* Raven, Peter H., Evert, Ray F., & Eichhorn, Susan E. (1986).
Biology of Plants (4th ed.). New York: Worth Publishers. ISBN 0-87901-315-X.
