{"id":22016,"date":"2026-04-19T08:11:48","date_gmt":"2026-04-19T11:11:48","guid":{"rendered":"https:\/\/mol-en.icb.usp.br\/?page_id=22016"},"modified":"2026-07-11T19:02:06","modified_gmt":"2026-07-11T22:02:06","slug":"7-3-bone","status":"publish","type":"page","link":"https:\/\/mol-en.icb.usp.br\/index.php\/7-3-bone\/","title":{"rendered":"7-3 Bone"},"content":{"rendered":"
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CELLS OF THE BONE TISSUE \u2013 1<\/strong> <\/div><\/div>\n<\/div>\n
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\nAttention must be paid to the following: besides having cells placed inside the bone tissue all bone surfaces, either outer or inner surfaces, are covered by bone cells.
\nBone cells arise from two lineages: the osteoblastic lineage<\/strong> and the osteoclastic lineage<\/strong>. Their cells have specific distributions and act on different functions.
\nThe cells of the osteoclastic lineage are the osteoclasts<\/strong>. They originate from stem cells produced in the bone marrow. They reach the bone tissue through the blood circulation and in the bone tissue they merge forming the osteoclasts, large multinucleated cells always placed on bone surfaces. They act on the resorption of the bone tissue in several situations, such as during bone growth, bone remodeling or repair.
\nThe osteoblastic lineage<\/strong> originates from mesenchymal cells and is constituted by the osteoprogenitor cells<\/strong> also called osteoprogenitors, osteoblasts<\/strong> and osteocytes<\/strong>.
\nThe osteoprogenitor cells, as their name implies, generate the other bone cells. They rest on the bone surfaces and have the potential to differentiate into osteoblasts, also placed on bone surfaces.
\nThe active osteoblasts are cuboidal and in histological sections resemble a simple cuboidal epithelium. They are bone-forming cells because they synthesize and secrete the peculiar bone extracellular matrix. After being entirely surrounded by the matrix the become incorporated into the already formed bone tissue and are recognised as osteocytes.
\nOsteoblasts that ceased originating osteocytes convert to flat cells and are called inactive osteoblasts. Together with osteoprogenitor cells the osteoblasts form the so-called bone lining cells<\/strong>.
\nOsteocytes<\/strong> are the mature bone cells and constitute the majority of cells of bones. They are placed within the bone tissue inside small cavities of the matrix called lacunae<\/strong> that are surrounded by the mineralized bone matrix.
\nOsteocytes emit delicate cytoplasmic extensions that occupy very narrow tunnels placed within the bone matrix. These extensions connect with extensions of neighbor osteocytes.
\nOsteoblasts and osteocytes are easily recognizable in histological sections, but not so the osteoprogenitor cells.
\nThe bone tissue shown in the figures is still being formed, it is not yet a mature bone.<\/p>\n

Upper figure
\nThe short bluish tissue stretches of tissue that merge with similar stretches are bone trabeculae. They become highlighted in pink after using the mouse cursor or clicking on the image.
\nMost of the nuclei seen as rows placed on the trabecular surfaces belong to osteoblasts whereas the nuclei situated inside the trabeculae belong to osteocytes.
\nThe less stained areas placed between trabeculae, highlighted in light blue, are loose connective tissue.<\/p>\n

Lower figure
\nOsteocytes (highlighted in light green) inside the bone tissue are surrounded by bone extracellular matrix.
\nMost of the nuclei disposed in rows and placed on trabecular surfaces belong to osteoblasts (highlighted in orange).
\nObserve in the lower right corner of the figure a large osteoclast placed on the surface of a trabecula (highlighted in blue and indicated by an arrow). <\/p>\n<\/div><\/div>\n

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Spongy bone. Staining: HE. Small magnification.<\/p>\n

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Spongy bone. Staining: HE. Small magnification.<\/p>\n

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