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Histologic specimen of human lung tissue stained with hematoxylin and eosin.
Histologic specimen of human lung tissue stained with hematoxylin and eosin. lung is the essential Respiration organ in air-breathing Animals including most Tetrapods a few Fish and a few Snails The most primitive Haematoxylin, hematoxylin, Natural Black 1, or CI 75290 is extracted from the wood of the Logwood tree Eosin is a Fluorescent red Dye resulting from the action of Bromine on Fluorescein.

Histology (from the Greek ἱστός) is the study of the microscopic anatomy of cells and tissues of plants and animals. Greek (el ελληνική γλώσσα or simply el ελληνικά — "Hellenic" is an Indo-European language, spoken today by 15-22 million people mainly Anatomy (from the Greek anatomia, from ana separate apart from and temnein, to cut up cut open is a branch of Biology that is the consideration The cell is the structural and functional unit of all known living Organisms It is the smallest unit of an organism that is classified as living and is often called Tissue is a cellular organizational level intermediate between cells and a complete organism Plants are living Organisms belonging to the kingdom Plantae. It is performed by examining a thin slice of tissue under a light microscope. The optical microscope, often referred to as the "light microscope" is a type of Microscope which uses Visible light and a system of lenses to Histology is an essential tool of biology and medicine. Foundations of modern biology There are five unifying principles Medicine is the art and science of healing It encompasses a range of Health care practices evolved to maintain and restore Human Health by the

Histopathology, the microscopic study of diseased tissue, is an important tool in anatomical pathology, since accurate diagnosis of cancer and other diseases usually requires histopathological examination of samples. Histopathology (from the Greek histos (tissue and pathos (suffering refers to the microscopic examination of tissue in order to study the manifestations Pathology; please do not remove --> ( Cancer (medical term Malignant Neoplasm) is a class of Diseases in which a group of cells display uncontrolled

The trained scientists who perform the preparation of histological sections are histotechnicians, histology technicians (HT), histology technologists (HTL), medical scientists, medical laboratory technicians, or biomedical scientists. Medical Laboratory Assistants (MLAs prepare and in some cases process samples within a Pathology laboratory A biomedical scientist (or biomedical doctor, biomedician, medical scientist) is a scientist educated in the field of Biological science, especially Their field of study is called histotechnology.

Contents

Technical procedure

Fixation

Main article: Fixation (histology)

Fixatives and Preservatives are used to preserve the tissue, the structures of the cell, and the cell organelles found in the individual cells (e. In the fields of Histology, Pathology, and Cell biology, fixation is a chemical process by which Biological tissues are preserved from decay g. , nucleus, rough endoplasmic reticulum,and mitochondria). The tissues are mechanically and biochemically stabilized in a fixative. The most common fixative is neutral buffered formalin (10% formaldehyde in Phosphate buffered saline (PBS)). Formaldehyde is a Chemical compound with the formula H2CO It is the simplest Aldehyde —an organic compound containing a terminal Carbonyl Phosphate buffered saline (abbreviated PBS is a Buffer solution commonly used in biological research. It is important to consider that a fixative should not be too toxic to its handler, and it should not damage the tissue being preserved.

Processing

The most common technique is wax processing. The samples are immersed in multiple baths of progressively more concentrated ethanol to dehydrate the tissue, followed by a clearing agent, such as xylene or Histoclear, and finally hot molten paraffin wax (impregnation). o-Xylene|m-Xylene|p-XyleneThe term xylene or xylol refers to a mixture of three Benzene derivatives which is used as a Solvent in the Printing In chemistry paraffin is the common name for the Alkane Hydrocarbons with the general formula C n H2 n +2 During this 12- to 16-hour process, paraffin wax replaces the xylene.

Embedding

Soft, moist tissues are turned into a hard paraffin block, which is then placed in a mold containing more molten wax (embedded) and allowed to cool and harden.

Embedding can also be accomplished using frozen, non-fixed tissue in a freezing medium. This freezing medium is liquid at room temperature but when cooled will solidify. Non-fixed tissue allows for procedures such as in situ hybridizations for specific mRNAs that would have been destroyed during the fixing process. Messenger ribonucleic acid ( mRNA) is a molecule of RNA encoding a chemical "blueprint" for a Protein product It also allows for very short turnaround where that is needed, as with a patient currently undergoing surgery. Surgery (from the χειρουργική cheirourgikē, via chirurgiae meaning "hand work" is a medical specialty that uses operative manual and instrumental

Sectioning

The tissue is then sectioned into very thin (2–8 micrometer) sections using a microtome. A microtome is a mechanical instrument used to cut biological specimens into transparent thin sections for microscopic examination These slices, usually thinner than the average cell, are then placed on a glass slide for staining. A microscope slide was originally a 'slider' made of ivory or bone containing specimens held between disks of transparent mica Staining is an auxiliary Technique used in Microscopy to enhance contrast in the microscopic image

Frozen tissue embedded in a freezing medium is cut on a microtome in a cooled machine called a cryostat. A Cryostat (cryo=cold and stat=stable is a vessel similar in construction to a Vacuum flask, or Dewar used to maintain cold Cryogenic temperatures

Staining

Routine staining: This is done to give contrast to the tissue being examined, as without staining it is very difficult to see differences in cell morphology. Staining is an auxiliary Technique used in Microscopy to enhance contrast in the microscopic image Hematoxylin and eosin (H&E) are the most commonly used stains in histology and histopathology. Haematoxylin, hematoxylin, Natural Black 1, or CI 75290 is extracted from the wood of the Logwood tree Eosin is a Fluorescent red Dye resulting from the action of Bromine on Fluorescein. Hematoxylin colors nuclei blue; eosin colors the cytoplasm pink. In Cell biology, the nucleus (pl nuclei; from Latin la ''nucleus'' or la ''nuculeus'' "little nut" or kernel is a membrane-enclosed The cytoplasm is the contents of a cell that is enclosed within the Plasma membrane. To see the tissue under a microscope, the sections are stained with one or more pigments. A microscope ( Greek: ( micron) = small + ( skopein) = to look or see is an instrument for viewing objects that are

Special staining: There are hundreds of various other techniques that have been used to selectively stain cells and cellular components. Other compounds used to color tissue sections include safranin, oil red o, Congo red, fast green FCF, silver salts, and numerous natural and artificial dyes that were usually originated from the development dyes for the textile industry. Safranin (also Safranin O or basic red 2) is a biological stain used in Histology and Cytology. A dye can generally be described as a Colored substance that has an affinity to the substrate to which it is being applied

Histochemistry refers to the science of using chemical reactions between laboratory chemicals and components within tissue. Histology (from the Greek = 'tissue' is the study of the microscopic anatomy of cells and tissues of Plants and A commonly performed histochemical technique is the Perls Prussian blue reaction, used to demonstrate iron deposits in diseases like hemochromatosis. Prussian blue is a very dark blue colorfast non-toxic Pigment – one of the first synthetic Dyes – which was discovered accidentally in Berlin in 1704 Haemochromatosis, also spelled hemochromatosis (see spelling differences) also called siderophilia

Histology samples have often been examined by radioactive techniques. In historadiography a slide (sometimes stained histochemically) is X-rayed. Historadiography is a technique formerly utilized in the fields of Histology and Cellular biology to provide semiquantitative information regarding the density of More commonly, autoradiography is used to visualize the locations to which a radioactive substance has been transported within the body, such as cells in S phase (undergoing DNA replication) which incorporate tritiated thymidine, or sites to which radiolabeled nucleic acid probes bind in in situ hybridization. An autoradiograph is an image on an X-ray film or nuclear emulsion produced by the pattern of decay emissions (e The S phase, short for synthesis phase, is a period in the Cell cycle during Interphase, between G1 phase and the G2 phase. DNA replication is the process of copying a double-stranded DNA molecule to form two double-stranded molecules Thymidine (more precisely called deoxythymidine; can also be labelled deoxyribosylthymine, and thymine deoxyriboside) is a Chemical compound A nucleic acid is a Macromolecule composed of chains of monomeric Nucleotides In Biochemistry these Molecules carry Genetic information In situ hybridization (ISH is a type of hybridization that uses a labeled Complementary DNA or RNA strand (i For autoradiography on a microscopic level, the slide is typically dipped into liquid nuclear tract emulsion, which dries to form the exposure film. Individual silver grains in the film are visualized with dark field microscopy. Dark field microscopy (dark ground microscopy describes microscopy methods in both light and electron microscopy which exclude the unscattered beam from the image

Recently, antibodies are used to specifically visualize proteins, carbohydrates, and lipids: this is called immunohistochemistry, or when the stain is a fluorescent molecule, immunofluorescence. Antibodies (also known as immunoglobulins, abbreviated Ig) are Gamma globulin Proteins that are found in Blood or other Bodily Immunohistochemistry or IHC refers to the process of localizing proteins in cells of a tissue section exploiting the principle of antibodies binding specifically Fluorescence is a Luminescence that is mostly found as an Immunofluorescence is the labeling of antibodies or Antigens with fluorescent Dyes This technique is often used to visualize the subcellular This technique has greatly increased the ability to identify categories of cells under a microscope. Other advanced techniques, such as nonradioactive in situ hybridization, can be combined with immunochemistry to identify specific DNA or RNA molecules with fluorescent probes or tags that can be used for immunofluorescence and enzyme-linked fluorescence amplification (especially alkaline phosphatase and tyramide signal amplification). Alkaline phosphatase ( ALP) ( is a Hydrolase Enzyme responsible for removing Phosphate groups from many types of molecules including Fluorescence microscopy and confocal microscopy are used to detect fluorescent signals with good intracellular detail. A fluorescence microscope (colloquially synonymous with epifluorescent microscope) is a light Microscope used to study properties of organic or inorganic substances Confocal microscopy is an optical imaging technique used to increase Micrograph contrast and/or to Reconstruct three-dimensional Images by Digital cameras are increasingly used to capture histological and histopathological image

Common laboratory stains

Fungi—black

Stain Common use Nucleus Cytoplasm Red blood cell (RBC) Collagen fibers Specifically stains
Haematoxylin General staining when paired with eosin Blue N/A N/A N/A Nucleic acids—blue

Blue eER (ergastoplasm)—blue
Eosin General staining when paired with haematoxylin N/A Pink Orange/red Pink Elastic fibers—pink

Reticular fibers—pink
Toluidine blue General staining Blue Blue Blue Blue Mast cells granules—purple
Masson's trichrome stain Connective tissue Black Red/pink Red Blue/green Cartilage—blue/green

Muscle fibers—red
Mallory's trichrome stain Connective tissue Red Pale red Orange Deep blue Keratin—orange

Cartilage—blue Bone matrix—deep blue Muscle fibers—red
Weigert's elastic stain Elastic fibers Blue/black N/A N/A N/A Elastic fibers—blue/black
Heidenhains'azan trichrome stain Distinguishing cells from extracellular components Red/purple Pink Red Blue Muscle fibers—red

Cartilage—blue Bone matrix—blue
Silver stain Reticular fibers, nerve fibers, fungi N/A N/A N/A Reticular fibers—brown/black

Nerve fibers—brown/black
Wright's stain Blood cells Bluish/purple Bluish/gray Red/pink N/A Neutrophil granules—purple/pink

Eosinophil granules—bright red/orange Basophil granules—deep purple/violet Platelet granules—red/purple
Orcein stain Elastic fibres Deep blue [or crazy red] N/A Bright red Pink Elastic fibres—dark brown

Mast cells granules—purple Smooth muscle—light blue
Periodic acid-Schiff stain (PAS) Basement membrane, localizing carbohydrates Blue N/A N/A Pink Glycogen and other carbohydrates—magenta

Table sourced from Michael H. Many compact digital still cameras can record Sound and moving Video as well as still Photograph. Haematoxylin, hematoxylin, Natural Black 1, or CI 75290 is extracted from the wood of the Logwood tree Eosin is a Fluorescent red Dye resulting from the action of Bromine on Fluorescein. Tolonium chloride ( INN, also known as toluidine blue O) is a compound used in Histology. Masson's trichrome is a three-color staining protocol used in Histology. Weigert's elastic stain is a combination of stains used in Histology which is useful in identifying Elastic fibers Often Orcein or a combination of Silver staining is the use of Silver to stain Histologic sections This kind of staining is important especially to show Proteins (for example type III Wright's stain is a Histologic stain that facilitates the differentiation of Blood cell types Orcein, also archil, orchil, lacmus, Litmus, Citrus Red 2, and C Periodic acid-Schiff ( PAS) is a Staining method used in Histology and Pathology. Ross, Wojciech Pawlina, (2006). Histology: A Text and Atlas. Hagerstwon, MD: Lippincott Williams & Wilkins. ISBN 0-7817-5056-3.  

The Nissl method and Golgi's method are useful in identifying neurons. Franz Nissl ( September 9, 1860 &ndash August 11, 1919) was a German Neuropathologist. Golgi's method is a Nervous tissue Staining technique discovered by Italian Physician and Scientist Camillo Golgi (1843-1926 Neurons (ˈnjuːɹɒn also known as neurones and nerve cells) are responsive cells in the Nervous system that process and transmit information

Alternative techniques

Alternative techniques include cryosection. The frozen section procedure is a pathological laboratory procedure to perform rapid microscopic analysis of a specimen The tissue is frozen and cut using a cryostat. A Cryostat (cryo=cold and stat=stable is a vessel similar in construction to a Vacuum flask, or Dewar used to maintain cold Cryogenic temperatures Tissue staining methods are similar to those of wax sections. Plastic embedding is commonly used in the preparation of material for electron microscopy. Tissues are embedded in epoxy resin. In Chemistry, epoxy or polyepoxide is a Thermosetting Epoxide Polymer that cures (polymerizes and crosslinks when mixed with a Very thin sections (less than 0. 1 micrometer) are cut using diamond or glass knives. The sections are stained with electron dense stains (uranium and lead) so that they can be seen with the electron microscope. An electron microscope is a type of Microscope that uses Electrons to illuminate a specimen and create an enlarged image

History

In the 19th century, histology was an academic discipline in its own right. The 1906 Nobel Prize in Physiology or Medicine was awarded to histologists Camillo Golgi and Santiago Ramon y Cajal. The Nobel Prize (Nobelpriset (Nobelprisen is a Swedish prize established in the 1895 will of Swedish chemist Alfred Nobel; it was first awarded in Peace, Literature Camillo Golgi ( July 7, 1843 &ndash January 21, 1926) was an Italian Physician and Scientist. Santiago Ramón y Cajal ( May 1 1852 &ndash October 17 1934) was a Spanish histologist, Physician, and They had dueling interpretations of the neural structure of the brain based in differing interpretations of the same images.

Histological classification of animal tissues

There are four basic types of tissues: muscle tissue, nervous tissue, connective tissue, and epithelial tissue. All tissue types are subtypes of these four basic tissue types (for example, blood cells are classified as connective tissue, since they generally originate inside bone marrow).

Note that tissues from plants, fungi, and microorganisms can also be examined histologically. In biology and medicine epithelium is a tissue composed of cells that line the cavities and surfaces of structures throughout the body The endothelium is the thin layer of cells that line the interior surface of Blood vessels forming an interface between circulating Blood in the The mesothelium is a membrane that forms the lining of several body cavities the Pleura (thoracal cavity Peritoneum (abdominal cavity including the mesentery and Mesenchyme refers to loosely organized connective tissue present in the embryo regardless of origin A blood cell (also called blood corpuscle) is any cell of any type normally found in Blood. Neurons (ˈnjuːɹɒn also known as neurones and nerve cells) are responsive cells in the Nervous system that process and transmit information Germ cells are progenitors of the Gametes. These singled out cells move through the gut to the developing Gonads and undergo mitotic proliferation followed A spermatozoon or spermatozoan ( pl spermatozoa) from the Ancient Greek σπέρμα (seed and ζῷον (living being and more commonly known An oocyte, ovocyte, or rarely ocyte, is a female Gametocyte or Germ cell involved in reproduction. The placenta is an Ephemeral organ present in placental Vertebrates, such as Eutherial Mammals and Sharks during Gestation Stem cells are cells found in most if not all multi-cellular Organisms. Their structure is very different from animal tissues.

Related sciences

Artifacts

Artifacts are structures or features in tissue that interfere with normal histological examination. These are not always present in normal tissue and can come from outside sources. Artifacts interfere with histology by changing the tissues appearance and hiding structures. These can be divided into two categories:

Pre-histology

These are features and structures that have being introduced prior to the collection of the tissues. A common example of these include: ink from tattoos and freckles (melanin) in skin samples.

Post-histology

Artifacts can result from tissue processing. Processing commonly lead to changes like shrinkage, color changes in different tissues types and alterations of the structures in the tissue. Because these are caused in a laboratory the majority of post histology artifacts can be avoided or removed after being discovered. A common example is mercury pigment left behind after using Bouin's fixative to fix a section.

References

1. Merck Source (2002). Dorland's Medical Dictionary. Dorland's is the brand name of a family of medical reference works (including dictionaries, spellers word books and spell-check software) in various media (including Retrieved 2005-01-26.

2. Stedman's Medical Dictionaries (2005). Stedman's Online Medical Dictionary. Retrieved 2005-01-26.

3. 4,000 online histology images (2007). (http://histology-online.com)

See also

External links

Pathology (from Greek grc πάθος pathos, "fate harm" and grc -λογία -logia) is the study and Pathology; please do not remove --> ( Histopathology (from the Greek histos (tissue and pathos (suffering refers to the microscopic examination of tissue in order to study the manifestations Staining is an auxiliary Technique used in Microscopy to enhance contrast in the microscopic image Anatomy Commentary on Anatomy in Avicenna's Canon Geoffrey Howard Bourne ( 17 November 1909 &ndash 19 July 1988) was an Australian U

Dictionary

histology

-noun

  1. (biology) The study of the microscopic structure, chemical composition and function of the tissue or tissue systems of plants and animals
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