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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 in side 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, 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: 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, 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.