Alternative techniques include cryosection. The tissue is frozen and cut using a cryostat. 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. 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.

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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. They had dueling interpretations of the neural structure of the brain based in differing interpretations of the same images.

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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).

• 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 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: any of the conducting cells of the nervous system
• Germ cells: reproductive cells (spermatozoa in men, oocytes in women)
• Placenta: an organ characteristic of true mammals during pregnancy, joining mother and offspring, providing endocrine secretion and selective exchange of soluble, but not particulate, blood-borne substances through an apposition of uterine and trophoblastic vascularised parts
• Stem cells: cells able to turn into one or several of the above types

Note that tissues from plants, fungi, and microorganisms can also be examined histologically. Their structure is very different from animal tissues.

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Related sciences

• Cell biology is the study of living cells, their DNA and RNA and the proteins they express.
• Anatomy is the study of organs visible by the naked eye.
• Morphology studies entire organisms.

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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:

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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.

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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.

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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.

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

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See also

• Pathology
• Anatomical pathology
• Histopathology
• Biological staining
• Important publications in histology
• Geoffrey Bourne

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External links

• Histology Protocols
• Immunohistochemistry - In Situ Hybridization
• Histoweb
• SIU SOM Histology
• Visual Histology Atlas
• Histology Glossary
• Histology Group of Victoria Incorporated
• Histology Photomicrographs
• Virtual Slidebox
• Blue Histology
• Histology for Dummies

v • d • e Histology: epithelial tissue Types Columnar (simple, stratified) - Cuboidal (simple, stratified) - Pseudostratified - Respiratory - Squamous (simple, stratified) - Transitional - Olfactory Features Lateral/cell-cell: Tight junction - Adherens junction - Desmosome - Gap junction Basal/cell-matrix: Basal lamina - Hemidesmosome - Focal adhesion Apical: Cilia - Microvilli - Stereocilia

v • d • e Histology: connective tissue Classification proper (loose/areolar, dense, adipose brown and white, reticular) embryonic (mucous, mesenchymal) specialized (cartilage, bone, blood) Extracellular matrix ground substance (tissue fluid) fibers (collagen, reticular fiber, elastic fibers) Cells resident (fibroblast, adipocyte, chondroblast, osteoblast), wandering cell

v • d • e Histology: muscle tissue skeletal muscle/general epimysium, fascicle, perimysium, endomysium, muscle fiber (intrafusal, extrafusal), myofibril sarcomere (a, i, and h bands; z and m lines), myofilaments (thin filament/actin, thick filament/myosin, elastic filament/titin, nebulin), tropomyosin, troponin (T, C, I) costamere (dystrophin, α,β-dystrobrevin, syncoilin, synemin/desmuslin, dysbindin, sarcoglycan, dystroglycan, sarcospan), desmin neuromuscular junction, motor unit, muscle spindle, excitation-contraction coupling, sliding filament mechanism myoblast, satellite cell, sarcoplasm, sarcolemma, sarcoplasmic reticulum, T-tubule cardiac muscle myocardium, intercalated disc, nebulette smooth muscle calmodulin, vascular smooth muscle

v • d • e Histology: nervous tissue Neurons (gray matter) soma - axon (axon hillock, axoplasm, axolemma, neurofibril/neurofilament) dendrite (Nissl body, dendritic spine, apical dendrite, basal dendrite) types: bipolar - pseudounipolar - multipolar - pyramidal - Purkinje - granule Afferent nerve/Sensory nerve/Sensory neuron GSA - GVA - SSA - SVA - fibers (Ia, Ib or Golgi, II or Aβ, III or Aδ or fast pain, IV or C or slow pain) Efferent nerve/Motor nerve/Motor neuron GSE - GVE - SVE - Upper motor neuron - Lower motor neuron (α motorneuron, γ motorneuron) Synapses neuropil - synaptic vesicle - neuromuscular junction - electrical synapse - Interneuron (Renshaw) Sensory receptors Meissner's corpuscle - Merkel nerve ending - Pacinian corpuscle - Ruffini ending - Muscle spindle Free nerve ending Olfactory receptor neuron - Photoreceptor cell - Hair cell - Taste bud Glial cells Astrocyte (Radial glia) - Oligodendrocyte - Ependymal cells (Tanycytes) - Microglia Myelination (white matter) CNS: Oligodendrocyte PNS: Schwann cell - Neurolemma - Nodes of Ranvier/Internode - Schmidt-Lanterman incisures Related connective tissues epineurium - perineurium - endoneurium - nerve fascicle - meninges

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