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Encyclopedia > Histological
A thin section of lung tissue stained with hematoxylin and eosin. This individual suffers from emphysema.
A thin section of lung tissue stained with hematoxylin and eosin. This individual suffers from emphysema.

Histology is the study of tissue sectioned as a thin slice, using a microscope. It can be described as microscopic anatomy. Histology is an essential tool of biology. Image File history File links Image is of H&E (haematoxylin and eosin) stained lung tissue sample taken from an end-stage emphysema patient. ... Image File history File links Image is of H&E (haematoxylin and eosin) stained lung tissue sample taken from an end-stage emphysema patient. ... The lungs flank the heart and great vessels in the chest cavity. ... Haematoxylin is extracted from the wood of the logwood tree. ... Eosin is an orange-pink dye derived from coal tar. ... Biological tissue is a substance made up of cells that perform a similar function. ... It has been suggested that microscopy be merged into this article or section. ... Anatomical drawing of the human muscles from the Encyclopédie. ... Biology is the study, or science, of life. ...


Histopathology, the microscopic study of diseased tissue, is an important tool of anatomical pathology since accurate diagnosis of cancer and other diseases usually requires histopathological examination of samples. Histopathology is the microscopic study of diseased tissue. ... Anatomical pathology is the branch of pathology that is concerned with the diagnosis of disease based on the gross and microscopic examination of cells and tissues. ... When normal cells are damaged beyond repair, they are eliminated by apoptosis. ...


The trained technicians who perform the preparation of histological sections are Histotechnicians, Histology Technicians (HT) or Histology Technologists (HTL). Their field of study is called histotechnology.

Contents


Source of tissue

Histological examination of tissues starts with surgery, biopsy or autopsy. A typical modern surgery operation Surgery (from the Greek cheirourgia meaning hand work) is the medical specialty that treats diseases or injuries by operative manual and instrumental treatment. ... A biopsy (in Greek: bios = life and opsy = look/appearance) is a medical test involving the removal of cells or tissues for examination. ... An autopsy, also known as a post-mortem examination or an obduction, is a medical procedure that consists of a thorough examination of a corpse to determine the cause and manner of a persons death and to evaluate any disease or injury that may be present. ...


Technical procedure

Fixation

The tissues are fixed in a fixative, a process that stabilizes the tissues to prevent decay. The most common fixative is formalin (10% formaldehyde in water). The chemical compound formaldehyde (also known as methanal), is a gas with a strong pungent smell. ...


Embedding

The most common technique is wax embedding. The samples are immersed in multiple baths of progressively more concentrated ethanol to dehydrate the tissue, followed by a clearing agent such as chloroform, xylene or Histoclear, and finally hot molten paraffin wax (impregnation). During this 12 to 16 hour process, paraffin wax will replace the water: soft, moist tissues are turned into a hard paraffin block, which is then placed in a mould containing more molten wax (embedded) and allowed to cool and harden. This article has been identified as possibly containing errors. ... PEL-TWA (OSHA) 50 ppm (240 mg/m3) IDLH (NIOSH) 500 ppm Flash point non-flammable RTECS number FS9100000 Supplementary data page Structure & properties n, εr, etc. ... The term xylenes refers to a group of 3 benzene derivatives which encompasses ortho-, meta-, and para- isomers of dimethyl benzene. ... Paraffin is a common name for a group of high molecular weight alkane hydrocarbons with the general formula CnH2n+2, where n is greater than about 20. ...


Sectionning

The tissue is then sectionned into very thin (5 - 7 micrometer) sections using a microtome. These slices, thinner than the average cell, are then placed on a glass slide for staining. A microtome is a mechanical instrument used to cut very thin slices for microscopic examination. ... Cells in culture, stained for keratin (red) and DNA (green) The cell is the structural and functional unit of all living organisms, and are sometimes called the building blocks of life. ... ...


Staining

A 5 to 7 micrometer slice of most tissues is almost completely transparent with very little visible detail. To see the tissue under a microscope, the sections are stained with one or more pigments. Hematoxylin and eosin (abbreviated H&E) are among the most commonly used stains in histology and histopathology. Hematoxylin colors nuclei blue, eosin colors the cytoplasm pink. Other compound used to color tissue sections include saffron, silver salts and numerous natural and artificial dyes originally developed to stain cloth fibers. The science of tissue staining is called histochemistry. It has been suggested that microscopy be merged into this article or section. ... ... Haematoxylin is extracted from the wood of the logwood tree. ... Eosin is an orange-pink dye derived from coal tar. ... In cell biology, the nucleus (from Latin nucleus or nuculeus, kernel) is found in all eukaryotic cells that contains most of the cells genetic material. ... Cytoplasm is a homogeneous, generally clear jelly-like material that fills cells. ... Binomial name Crocus sativus L. Saffron (IPA: ) is a spice derived from the flower of the saffron crocus (Crocus sativus), a species of crocus in the family Iridaceae. ... A dye can generally be described as a coloured substance that has an affinity to the substrate to which it is being applied. ...


Recently, antibodies are used to stain specific proteins: this is called immunohistochemistry. This technique has greatly increased the ability to identify categories of cells under a microscope. Other advanced techniques include in situ hybridization to identify specific DNA or RNA molecules, and confocal microscopy. Digital cameras are increasingly used to capture histological and histopathological images. Wikipedia does not yet have an article with this exact name. ... A SiPix digital camera next to a matchbox to show scale. ...


Alternative techniques

Alternative techniques include cryosection. The tissue is frozen and cut using a cryostat. They are stained in simular ways to that of wax sections Plastic embedding is commonly used in the preparation of material for electron microscopy. Tissues are imbedded in epoxy resin. Very thin sections (less than 0.1 micrometers) 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. Cryocoolers are refrigerators used to reach cryogenic temperatures. ... Epoxy or polyepoxide is a thermosetting epoxide polymer that cures when mixed with a catalyzing agent or hardener. Most common epoxy resins are produced from a reaction between epichlorohydrin and bisphenol-A. The first commercial attempts to prepare resins from epichlorohydrin occurred in 1927 in the United States. ... A transmission electron microscope. ...


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 two histologists, Camillo Golgi and Santiago Ramón y Cajal. They had dueling interpretations of the neural structure of the brain based in differing interpretations of the same images. This article does not cite its references or sources. ... Camillo Golgi, 1906. ... Santiago Ramón y Cajal Santiago Ramón y Cajal (May 1, 1852 – October 17, 1934), Nobel laureate, 1906, was a Spanish histologist and is considered to be the father of modern neuroscience. ...


Histological classification of animal tissues

  • epithelium: the lining of glands, bowel, skin and some organs like the liver, lung, kidney,
  • endothelium: the lining of blood and lymphatic vessels,
  • mesothelium: the lining of pleural, peritoneal and pericardial spaces,
  • mesenchyme: the cells filling the spaces between the organs, including fat, muscle, bone, cartilage and tendon cells,
  • blood cells: the red and white blood cells, including those found in lymph nodes and spleen,
  • neurons: cells forming the brain, nerves and some glands like the pituitary and adrenal glands,
  • germ cells: reproductive cells, spermatozoa in men, oocytes in women,
  • placenta: a specialized organ essential for the growth of the fetus in the mother's uterus, and
  • stem cells: cells able to turn into one or several of the above types.

Note that tissues from plant, fungus and microorganisms can also be examined histologically. Their structure is very different from animal tissue. In zootomy, epithelium is a tissue composed of a layer of cells. ... The endothelium is the layer of thin, flat cells that lines the interior surface of blood vessels, forming an interface between circulating blood in the lumen and the rest of the vessel wall. ... The mesothelium is a membrane that forms the lining of several body cavities: the pleura (thoracal cavity), peritoneum (abdominal cavity) and pericardium (heart sac). ... Mesenchyme (also known as embryonic connective tissue) is the mass of tissue that develops mainly from the mesoderm (the middle layer of the trilaminar germ disc) of an embryo. ... Red blood cells (erythrocytes) are present in the blood and help carry oxygen to the rest of the cells in the body Blood is a circulating tissue composed of fluid plasma and cells (red blood cells, white blood cells, platelets). ... Neurons (also called nerve cells) are the primary cells of the nervous system. ... Gametes (in Greek: γαμέτες) —also known as sex cells, germ cells, or spores—are the specialized cells that come together during fertilization (conception) in organisms that reproduce sexually. ... Schematic diagram of a sperm cell, showing the (1) acrosome, (2) cell membrane, (3) nucleus, (4) mitochondria, and (5) flagellum (tail) A sperm cell, or spermatozoon ( spermatozoa) (in Greek: sperm = semen and zoon = alive), is the haploid cell that is the male gamete. ... An oocyte or ovocyte is a female gametocyte that divides twice by mitosis and meiosis into two other oocytes or into two ootids. ... The placenta is an ephemeral (temporary) organ present only in female placental mammals during gestation (pregnancy). ... Mouse embryonic stem cells. ...


Related sciences

Cytology (also known as Cell biology) is the scientific study of cells. ... The pap smear as we know it is an invention of Dr. Georgios Papanikolaou (1883-1962), an American of Greek birth, the father of cytopathology. ... Cell biology (also called cellular biology or cytology, from the Greek kytos, container) is an academic discipline which studies cells. ... Schematic of typical animal cell, showing subcellular components. ... A transmission electron microscope. ... Biochemistry the chemistry of life, a bridge between biology and chemistry that studies how complex chemical reactions give rise to life. ... Anatomical drawing of the human muscles from the Encyclopédie. ... In biology, an organ (Latin: organum, instrument, tool) is a group of tissues, which perform a specific function or group of functions. ... Comparative anatomy is the study of similarities and differences in organisms. ...

Histological artifacts

A histological artifact is a structure or feature that is absent in living tissues, but introduced during preparation or staining. Troubleshooting and minimizing artifacts is a major part of the discipline of histochemistry.


References

1. Merck Source (2002). Dorland's Medical Dictionary. Retrieved 2005-01-26.


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


See also

Pathology (from Greek pathos, feeling, pain, suffering; and logos, study of; see also -ology) is the study of the processes underlying disease and other forms of illness, harmful abnormality, or dysfunction. ... Anatomical pathology is the branch of pathology that is concerned with the diagnosis of disease based on the gross and microscopic examination of cells and tissues. ... Histopathology is the microscopic study of diseased tissue. ... Staining is a biochemical technique of adding a class-specific (DNA, proteins, lipids, carbohydrates) dye to a substrate to qualify or quantify the presence of a specific compound. ... To meet Wikipedias quality standards, this article or section may require cleanup. ...

External links


  Results from FactBites:
 
Article - Histologic features of placentas and abortion specimens from women with antiphospholipid and ... (437 words)
Twenty histologic parameters were systematically assessed by a single investigator who was blinded to the clinical status of the specimens.
There were no histologic differences in tissues from live births and pregnancy losses, or in treated and untreated pregnancies.
Histologic findings in women with APS are non-specific and may not differentiate between women with APS and APS-like syndromes.
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