5.3.3: Bone Tissue
- Page ID
- 53904
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)Bone Tissue
There are two types of bone: spongy bone has spaces between bony trabeculae (slender needle-like structures) filled with bone marrow, and compact bone which is more solid and composed of functional units called osteons.
Above: A femur (hip to knee) bone with a partial frontal section. Compact bone is located on the outer layers of the bone, particularly along the shaft. The interior of the bone is composed of spongy bone where bone marrow is located in the pockets between the trabeculae of bone.
The bone cells, or osteocytes, are located in lacunae (a space or gap inside the tissue; sing. lacuna). Osteocytes are protected from the extracellular matrix that surrounds them by being housed in lacunae, which are spaces free of mineralized extracellular matrix. Bone has mainly collagen protein fibers in and a ground substance rich in a mineralized calcium phosphate compound known as hydroxyapatite. The hydroxyapatite that surrounds the mostly collagen protein fibers in the ground substance of bone is not soluble in water and forms a mineral solid in which both the bone cells and the collagen fibers are embedded. It is usually difficult to see the collagen fibers in the extracellular matrix of bone due to the density of the ground substance that surrounds them. There are four types of bone cells: osteoprogenitor cells, osteoblasts, osteoclasts, and osteocytes. Osteocytes are the most abundant and the only ones found throughout the bone.
Osteocytes have numerous cytoplasmic extensions that project off of the main cell body. These extension connect up with the extensions from other nearby osteocytes. These projections, like the osteocyte cell body, are in tiny spaces free of the mineralized extracellular matrix. These spaces (but not the cytoplasmic projections themselves) are called canaliculi (singular: canaliculum) because, under the microscope, they look like tiny little canals.
Compact Bone
Osteocytes are inside of lacunae (hollow spaces) located in concentric circles of mineralized extracellular matrix. Each circle is called a lamella (plural: lamellae) and the osteocytes are found along the edges of each lamella. In compact bone, groups of lamellae and osteocytes are arranged into individual osteons, the cylindrical arrangement of material that makes up the fundamental building block of the compact bone. Each osteon has a hollow central canal in its center that blood vessels and nerves can travel through.
Above: Compact bone. Tissue is magnified by 40x.
Above: Compact bone. Tissue magnified by 200x.
Above: Compact bone. Tissue is magnified by 400x.
Spongy Bone
In spongy bone, groups of lamellae are arranged into trabeculae (singular: trabecula), which are the individual projections of spongy bone. Trabeculae do not have central canals. Bone marrow surrounding the trabeculae store fats and produce new blood cells, a process called hematopoiesis.
Above: Spongy bone tissue (trabeculae) with pockets of bone marrow surrounding it. Tissue is magnified by 400x.
Attributions (All Connective Tissues Sections)
- "Anatomy and Physiology" by J. Gordon Betts et al., OpenStax is licensed under CC BY 4.0
- "Anatomy and Physiology I Lab" by Victoria Vidal is licensed under CC BY 4.0
- "Animal Tissues and Organs" by Berkshire Community College Bioscience Image Library is in the Public Domain, CC0
- "BIOL 250 Human Anatomy Lab Manual SU 19" by Yancy Aquino, Skyline College is licensed under CC BY-NC-SA 4.0
- "Digital Histology" by Department of Anatomy and Neurobiology and the Office of Faculty Affairs, Virginia Commonwealth University School of Medicine and the ALT Lab at Virginia Commonwealth University is licensed under CC BY 4.0
- "Human eye iris 3" by Kamil Saitov is licensed under CC BY 4.0
Updated 2025.