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Tissue is a group of similar cells with shared origin performing a specific function. In animals, the four main tissue types are epithelial, connective, muscle, and nervous. Plant tissues include epidermis, ground tissue, and vascular tissue. Histology is the study of tissue structure under a microscope, crucial for understanding cell and tissue functions. Histology relies on preparing slides through fixation, processing, embedding, sectioning, and staining. Hematoxylin and eosin are common stains, highlighting nuclei and cytoplasm respectively. Histology finds applications in education, archaeology, disease diagnosis, and forensic investigations.

Tissue Definition and Examples in
Biology
Types of Plant and Animal Tissues
By
Anne Marie Helmenstine, Ph.D.
Anne Marie Helmenstine, Ph.D.
Chemistry Expert
 Ph.D., Biomedical Sciences, University of Tennessee at Knoxville
 B.A., Physics and Mathematics, Hastings College
Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and
consultant. She has taught science courses at the high school, college, and graduate levels.
Updated on November 26, 2019
In biology, a tissue is a group of cells and their extracellular matrix that share
the same embryonic origin and perform a similar function. Multiple tissues
then form organs. The study of animal tissues is called histology,
or histopathology when it is concerned with diseases. The study of plant tissues
is called plant anatomy. The word "tissue" comes from the French word "tissu,"
which means "woven." French anatomist and pathologist Marie François
Xavier Bichat introduced the term in 1801, stating that body functions could be
understood better if they were studied at the level of tissues rather than
organs.
Key Takeaways: Tissue Definition in Biology
 A tissue is a group of cells with the same origin that serve a similar
function.
 Tissues are found in animals and plants.
 The four main types of animal tissues are connective, nervous, muscle,
and epithelial tissues.
 The three main tissue systems in plants are the epidermis, ground tissue,
and vascular tissue.
Animal Tissues
There are four basic tissues in humans and other animals: epithelial tissue,
connective tissue, muscle tissue, and nervous tissue. The embryonic tissue
(ectoderm, mesoderm, endoderm) from which they derive sometimes varies,
according to species.
Epithelial Tissue
Cells of epithelial tissue form sheets that cover the body and organ surfaces. In
all animals, most epithelium derives from the ectoderm and endoderm, except
the epithelium, which derives from the mesoderm. Examples of epithelial
tissue include the skin surface and the linings of the airways, reproductive
tract, and gastrointestinal tract. There are several kinds of epithelium,
including simple squamous epithelium, simple cuboidal epithelium, and
columnar epithelium. Functions include protecting organs, eliminating waste,
absorbing water and nutrients, and secreting hormones and enzymes.
Connective Tissue
Connective tissue consists of cells and non-living material, called the
extracellular matrix. The extracellular matrix may be either fluid or solid.
Examples of connective tissue include blood, bone, adipose, tendons, and
ligaments. In humans, cranial bones derive from the ectoderm, but the other
connective tissues come from the mesoderm. Functions of connective tissue
include shaping and supporting organs and the body, allowing body
movement, and providing oxygen diffusion.
Muscle Tissue
The three types of muscle tissue are skeletal muscle, cardiac muscle, and
smooth (visceral) muscle. In humans, muscles develop from the mesoderm.
Muscles contract and relax to allow body parts to move and blood to pump.
Nervous Tissue
Nervous tissue is divided into the central nervous system and peripheral
nervous system. It includes the brain, spinal cord, and nerves. The nervous
system derives from the ectoderm. The nervous system controls the body and
communicates between its parts.
Plant Tissues
VectorMine / Getty Images
There are three tissue systems in plants: epidermis, ground tissue, and
vascular tissue. Alternatively, plant tissues may be categorized as either
meristematic or permanent.
Epidermis
The epidermis consist of cells that coat the outer surface of leaves and the
bodies of young plants. Its functions include protection, waste removal, and
nutrient absorption.
Vascular Tissue
Vascular tissue is akin to blood vessels in animals. It includes the xylem and
phloem. Vascular tissue transports water and nutrients within a plant.
Ground Tissue
Ground tissue in plants is like connective tissue in animals. It supports the
plant, manufactures glucose via photosynthesis, and stores nutrients.
Meristematic Tissue
Actively dividing cells are meristematic tissue. This is the tissue that allows a
plant to grow. The three types of meristematic tissue are apical meristem,
lateral meristem, and intercalary meristem. Apical meristem is the tissue at
stem and root tips that increases stem and root length. Lateral meristem
includes tissues that divide to increase the diameter of a plant part. Intercalary
meristem is responsible for the formation and growth of branches.
Permanent Tissue
Permanent tissue encompasses all cells, living or dead, that have stopped
dividing and maintain a permanent position within a plant. The three types of
permanent tissue are simple permanent tissue, complex permanent tissue, and
secretory (glandular) tissue. Simple tissue is further divided into the
parenchyma, collenchyma, and sclerenchyma. Permanent tissue provides
support and structure for a plant, helps manufacture glucose, and stores water
and nutrients (and sometimes air).
Sources
 Bock, Ortwin (2015). "A history of the development of histology up to
the end of the nineteenth century." Research. 2:1283.
doi:10.13070/rs.en.2.1283
 Raven, Peter H.; Evert, Ray F.; Eichhorn, Susan E. (1986). Biology of
Plants (4th ed.). New York: Worth Publishers. ISBN 0-87901-315-X.
 Ross, Michael H.; Pawlina, Wojciech (2016). Histology : A Text and Atlas : With
Correlated Cell and Molecular Biology (7th ed.). Wolters Kluwer. ISBN 978-
1451187427.
What Histology Is and How It's Used
A Definition and Introduction
By
Anne Marie Helmenstine, Ph.D.
Anne Marie Helmenstine, Ph.D.


Chemistry Expert
 Ph.D., Biomedical Sciences, University of Tennessee at Knoxville
 B.A., Physics and Mathematics, Hastings College
Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and
consultant. She has taught science courses at the high school, college, and graduate levels.
LEARN ABOUT OUR EDITORIAL PROCESS
Updated on March 24, 2019
Histology is defined as the scientific study of the microscopic structure
(microanatomy) of cells and tissues. The term "histology" comes from the
Greek words "histos," meaning tissue or columns, and "logia," which means
study. The word "histology" first appeared in a 1819 book written by German
anatomist and physiologist Karl Meyer, tracing its roots back to 17th-century
microscopic studies of biological structures performed by Italian physician
Marcello Malpighi.
How Histology Works
Courses in histology focus on the preparation of histology slides, relying on
previous mastery of anatomy and physiology. Light and electron
microscopy techniques are usually taught separately.
The five steps of preparing slides for histology are:

1. Fixing


2. Processing


3. Embedding


4. Sectioning


5. Staining
   Cells and tissues must be fixed to prevent decay and degradation. Processing is
   required to prevent excessive alteration of tissues when they are embedded.
   Embedding involves placing a sample within a supporting material (e.g.,
   paraffin or plastic) so small samples can be cut into thin sections, suitable for
   microscopy. Sectioning is performed using special blades called microtomes or
   ultramicrotomes. Sections are placed on microscope slides and stained. A
   variety of staining protocols are available, chosen to enhance the visibility of
   specific types of structures.
   The most common stain is a combination of hematoxylin and eosin (H&E
   stain). Hematoxylin stains cellular nuclei blue, while eosin stains cytoplasm
   pink. Images of H&E slides tend to be in shades of pink and blue. Toluidine
   blue stains the nucleus and cytoplasm blue, but mast cells purple. Wright's
   stain colors red blood cells blue/purple, while turning white blood cells and
   platelets other colors.
   Hematoxylin and eosin produce a permanent stain, so slides made using
   this combination may be kept for later examination. Some other histology
   stains are temporary, so photomicrography is necessary in order to preserve
   data. Most of the trichrome stains are differential stains, where a single
   mixture produces multiple colors. For example, Malloy's trichrome stain colors
   cytoplasm pale red, the nucleus and muscle red, red blood cells and keratin
   orange, cartilage blue, and bone deep blue.
   Types of Tissues
   The two broad categories of tissues are plant tissue and animal tissue.
   Plant histology usually is called "plant anatomy" to avoid confusion. The main
   types of plant tissues are:
    Vascular tissue
    Dermal tissue
    Meristematic tissue
    Ground tissue
   In humans and other animals, all tissue may be classified as belonging to one
   of four groups:
    Nervous tissue
    Muscle tissue
    Epithelial tissue
    Connective tissue
   Subcategories of these main types include epithelium, endothelium,
   mesothelium, mesenchyme, germ cells, and stem cells.
   Histology may also be used to study structures in microorganisms, fungi, and
   algae.
   Careers in Histology
   A person who prepares tissues for sectioning, cuts them, stains them, and
   images them is called a histologist. Histologists work in labs and have highly
   refined skills, used to determine the best way to cut a sample, how to stain
   sections to make important structures visible, and how to image slides using
   microscopy. Laboratory personnel in a histology lab include biomedical
   scientists, medical technicians, histology technicians (HT), and histology
   technologists (HTL).
   The slides and images produced by histologists are examined by medical
   doctors called pathologists. Pathologists specialize in identifying abnormal
   cells and tissues. A pathologist can identify many conditions and diseases,
   including cancer and parasitic infection, so other doctors, veterinarians, and
   botanists can devise treatment plans or determine whether an abnormality led
   to death.
   Histopathologists are specialists who study diseased tissue. A career in
   histopathology typically requires a medical degree or doctorate. Many
   scientists in this discipline have dual degrees.
   Uses of Histology
   Histology is important in science education, applied science, and medicine.
    Histology is taught to biologists, medical students, and veterinary
   students because it helps them understand and recognize different types
   of tissues. In turn, histology bridges the gap between anatomy and
   physiology by showing what happens to tissues at the cellular level.
    Archaeologists use histology to study biological material recovered from
   archaeological sites. Bones and teeth are most likely to provide data.
   Paleontologists may recover useful material from organisms preserved
   in amber or frozen in permafrost.
    Histology is used to diagnose diseases in humans, animals, and plants
   and to analyze the effects of treatment.
    Histology is used during autopsies and forensic investigations to help
   understand unexplained deaths. In some cases, a cause of death may be
   evident from microscopic tissue examination. In other cases, the
   microanatomy may reveal clues about the environment after death.