Histology - Histological Classification of Animal Tissues

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, and 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 with the ability to develop into different cell types

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