Tendon Anatomy: Difference between revisions
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= Basic Anatomy and Physiology of a Tendon = | = Basic Anatomy and Physiology of a Tendon = | ||
Tendons are situated between bone and muscles and are bright white in colour, their fibro-elastic composition gives them the strength require to transmit large mechanical forces. Each muscle has two tendons, one proximally and one distally. The point at which the tendon forms attachment to the muscle is also known as the musculotendinous junction (MTJ) and the point at which it attaches to the bone is known as the osteotendinous junction (OTJ). The purpose of the tendon is to transmit forces generated from the muscle to the bone to elicit movement. The proximal attachment of the tendon is also known as the origin and the distal tendon is called the insertion.<ref name="Kannus 2000">Kannus P. Structure of the tendon connective tissue. Scandinavian Journal of Medicine &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp; Science in Sports. 2000; 10: 312-320.</ref> | Tendons are situated between bone and muscles and are bright white in colour, their fibro-elastic composition gives them the strength require to transmit large mechanical forces. Each muscle has two tendons, one proximally and one distally. The point at which the tendon forms attachment to the muscle is also known as the musculotendinous junction (MTJ) and the point at which it attaches to the bone is known as the osteotendinous junction (OTJ). The purpose of the tendon is to transmit forces generated from the muscle to the bone to elicit movement. The proximal attachment of the tendon is also known as the origin and the distal tendon is called the insertion.<ref name="Kannus 2000">Kannus P. Structure of the tendon connective tissue. Scandinavian Journal of Medicine &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp; Science in Sports. 2000; 10: 312-320.</ref> | ||
Tendons have different shapes and sizes depending on the role of the muscle. Muscles that generate a lot of power and force tend to have shorter and wider tendons than those that perform more fine delicate movements. These tend to be long and thin. <ref name="Benjamin et al 2008">Benjamin M, kaiser E, Milz. Structure-function relationships in tendons: a review. Journal of Anatomy 2008; 212: 211-228</ref> | Tendons have different shapes and sizes depending on the role of the muscle. Muscles that generate a lot of power and force tend to have shorter and wider tendons than those that perform more fine delicate movements. These tend to be long and thin. <ref name="Benjamin et al 2008">Benjamin M, kaiser E, Milz. Structure-function relationships in tendons: a review. Journal of Anatomy 2008; 212: 211-228</ref> | ||
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= Cellular Component of a Tendon = | = Cellular Component of a Tendon = | ||
The tendon cells are known as tenoblasts and tenocytes. They make up approximately 90-95% of the cells within the tendon. The other 5-10% include the chondrocyctes, synovial cells and the vascular cells.<ref name="Kannus 2000">Kannus P. Structure of the tendon connective tissue. Scandinavian Journal of Medicine &amp;amp;amp;amp;amp;amp;amp;amp; Science in Sports 2000; 312-320.</ref> | The tendon cells are known as tenoblasts and tenocytes. They make up approximately 90-95% of the cells within the tendon. The other 5-10% include the chondrocyctes, synovial cells and the vascular cells.<ref name="Kannus 2000">Kannus P. Structure of the tendon connective tissue. Scandinavian Journal of Medicine &amp;amp;amp;amp;amp;amp;amp;amp;amp; Science in Sports 2000; 312-320.</ref> | ||
Tenoblasts are immature tendon cells. Initially they are different in size and shape but as they age they become elongated and spindle shaped and transform into tenocytes. The tenocyctes are responsible for the turnover of maintenance of the extracellular matrix (described below). The tenocyctes respond to mechanical load of the tendon and thus make adaptations. They are arranged in longitudinal rows and have extensive communication with adjacent cells usually through gap junctions.<ref name="Kannus 2000">Kannus p. Structure of the tendon connective tissue. Scandinavian Journal of Medicine &amp;amp;amp;amp;amp;amp;amp;amp; Science in Sports 2000; 10:312-320</ref><ref name="Sharma & Maffulli 2006">Sharma P, Maffulli N. Biology of tendon injury: healing, modeling and remodeling. Journal of Musculoskeletal Neuronal Interact. 2006; 6 (2): 181-190.</ref> | Tenoblasts are immature tendon cells. Initially they are different in size and shape but as they age they become elongated and spindle shaped and transform into tenocytes. The tenocyctes are responsible for the turnover of maintenance of the extracellular matrix (described below). The tenocyctes respond to mechanical load of the tendon and thus make adaptations. They are arranged in longitudinal rows and have extensive communication with adjacent cells usually through gap junctions.<ref name="Kannus 2000">Kannus p. Structure of the tendon connective tissue. Scandinavian Journal of Medicine &amp;amp;amp;amp;amp;amp;amp;amp;amp; Science in Sports 2000; 10:312-320</ref><ref name="Sharma & Maffulli 2006">Sharma P, Maffulli N. Biology of tendon injury: healing, modeling and remodeling. Journal of Musculoskeletal Neuronal Interact. 2006; 6 (2): 181-190.</ref> | ||
Gap junctions are very complex and complicated structures. They have two hemi-channels. These are also called connexons (a collection of six connexin protein subunits). These have a central pore. The connexons in an open state allow metabolites and ions to pass freely between the gap junctions. The connexins are numbered, the ones which we are interested in for cell communication and tendon regeneration are connexins 26, 32 and 43.<ref name="Maeda et al 2012">Maeda E, Shangjun Y, Wang W, Bader DL, Knight MM, Lee DA. Gap junction permability between tenocytes within tendon fasciles is supported by tensile loading. Journal of Biomechinical Model Mechanobiol 2012; 11:439-447</ref><ref name="Goldberg et al 1999">Goldberg GS, Lampe PD, Nicholson BJ. Selective transfer of endogenous metabolites through gap junctions composed of different connexins. Nature Cell Biology 1999; 1:457–459.</ref><ref name="Wagett et al 2006">Wagett AD, Benjamin M, Ralphs JR. Connexin 32 and 43 gap junctions differentially modulate tenocyte response to cyclic mechanical load. European Journal of Cell Biology 2006 85:1145–1154</ref> | Gap junctions are very complex and complicated structures. They have two hemi-channels. These are also called connexons (a collection of six connexin protein subunits). These have a central pore. The connexons in an open state allow metabolites and ions to pass freely between the gap junctions. The connexins are numbered, the ones which we are interested in for cell communication and tendon regeneration are connexins 26, 32 and 43.<ref name="Maeda et al 2012">Maeda E, Shangjun Y, Wang W, Bader DL, Knight MM, Lee DA. Gap junction permability between tenocytes within tendon fasciles is supported by tensile loading. Journal of Biomechinical Model Mechanobiol 2012; 11:439-447</ref><ref name="Goldberg et al 1999">Goldberg GS, Lampe PD, Nicholson BJ. Selective transfer of endogenous metabolites through gap junctions composed of different connexins. Nature Cell Biology 1999; 1:457–459.</ref><ref name="Wagett et al 2006">Wagett AD, Benjamin M, Ralphs JR. Connexin 32 and 43 gap junctions differentially modulate tenocyte response to cyclic mechanical load. European Journal of Cell Biology 2006 85:1145–1154</ref> | ||
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The orientation of the collagen fibres in tendons have been found to run; parallel, simply crossing, crossing of two fibres with one straight, a plait formation of three fibres and an up typing of two parallel running fibres. The orientation and organisation of collagen fibres differs from tendon to tendon and vary in location of the tendon. This is dependent on the requirement of each tendon. For example tendons that need to resist rotational tensile forces will have a collagen fibre orientation to enable this. <br>The collagen molecules consist of polypeptide chains, three of these chains combined together form a densely packed helical tropocollagen molecule. Five of these combined together form a microfibril. The microfibrils then aggregate together to form fibrils. These are then grouped into fibres and fibres into fibre bundles and then into fascicles. | The orientation of the collagen fibres in tendons have been found to run; parallel, simply crossing, crossing of two fibres with one straight, a plait formation of three fibres and an up typing of two parallel running fibres. The orientation and organisation of collagen fibres differs from tendon to tendon and vary in location of the tendon. This is dependent on the requirement of each tendon. For example tendons that need to resist rotational tensile forces will have a collagen fibre orientation to enable this. <br>The collagen molecules consist of polypeptide chains, three of these chains combined together form a densely packed helical tropocollagen molecule. Five of these combined together form a microfibril. The microfibrils then aggregate together to form fibrils. These are then grouped into fibres and fibres into fibre bundles and then into fascicles. | ||
The fascicles are small in diameter in the young but as they mature into you adulthood they grow in size, peaking in size between the ages of 20-29 years old. As the tendon progressively ages the diameter becomes smaller, this has been linked to a possibility in the decreased strength of the muscle. It has also been noted that the diameter can shrink in size if the tendon becomes injured. <ref name="Benjamin et al 2008">Benjamin M, kaiser E, Milz. Structure-function relationships in tendons: a review. Journal of Anatomy 2008; 212: 211-228</ref><br> | The fascicles are small in diameter in the young but as they mature into you adulthood they grow in size, peaking in size between the ages of 20-29 years old. As the tendon progressively ages the diameter becomes smaller, this has been linked to a possibility in the decreased strength of the muscle. It has also been noted that the diameter can shrink in size if the tendon becomes injured. <ref name="Benjamin et al 2008">Benjamin M, kaiser E, Milz. Structure-function relationships in tendons: a review. Journal of Anatomy 2008; 212: 211-228</ref><ref name="Sharma & Maffulli, 2006">Sharma P, Maffulli N. Biology of tendon injury: healing, modeling and remodeling. Journal of Musculoskeletal Neuronal Interact. 2006; 6 (2): 181-190.</ref><br> | ||
= Blood Supply = | = Blood Supply = | ||
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#The synovial sheaths | #The synovial sheaths | ||
#The peritendinous sheet (paratenon) | #The peritendinous sheet (paratenon) | ||
#The tendon bursae<ref name="Kannus 2000">Kannus P. Structure of the tendon connective tissue. Scandinavian Journal of Medicine &amp; Science in Sports. 2000; 10: 312-320.</ref><br> | #The tendon bursae<ref name="Kannus 2000">Kannus P. Structure of the tendon connective tissue. Scandinavian Journal of Medicine &amp;amp; Science in Sports. 2000; 10: 312-320.</ref><br> | ||
= References = | = References = | ||
<references /> | <references /> | ||
Revision as of 14:48, 16 November 2015
Basic Anatomy and Physiology of a Tendon [edit | edit source]
Tendons are situated between bone and muscles and are bright white in colour, their fibro-elastic composition gives them the strength require to transmit large mechanical forces. Each muscle has two tendons, one proximally and one distally. The point at which the tendon forms attachment to the muscle is also known as the musculotendinous junction (MTJ) and the point at which it attaches to the bone is known as the osteotendinous junction (OTJ). The purpose of the tendon is to transmit forces generated from the muscle to the bone to elicit movement. The proximal attachment of the tendon is also known as the origin and the distal tendon is called the insertion.[1]
Tendons have different shapes and sizes depending on the role of the muscle. Muscles that generate a lot of power and force tend to have shorter and wider tendons than those that perform more fine delicate movements. These tend to be long and thin. [2]
Cellular Component of a Tendon [edit | edit source]
The tendon cells are known as tenoblasts and tenocytes. They make up approximately 90-95% of the cells within the tendon. The other 5-10% include the chondrocyctes, synovial cells and the vascular cells.[1]
Tenoblasts are immature tendon cells. Initially they are different in size and shape but as they age they become elongated and spindle shaped and transform into tenocytes. The tenocyctes are responsible for the turnover of maintenance of the extracellular matrix (described below). The tenocyctes respond to mechanical load of the tendon and thus make adaptations. They are arranged in longitudinal rows and have extensive communication with adjacent cells usually through gap junctions.[1][3]
Gap junctions are very complex and complicated structures. They have two hemi-channels. These are also called connexons (a collection of six connexin protein subunits). These have a central pore. The connexons in an open state allow metabolites and ions to pass freely between the gap junctions. The connexins are numbered, the ones which we are interested in for cell communication and tendon regeneration are connexins 26, 32 and 43.[4][5][6]
Connexin 43 is situated in gap junctions between cells in rows along the collagen fibres. Connexins 26 and 32 have a more diffuse pattern. Connexin 43 is responsible for the inhibition of the collagen syntheses within the tenocyctes as a response to mechanical loading. Connexin 32 may have a stimulatory role, but all we need to know is that they aid communication between cells within the tendon to help with regeneration and adaptation. [7]
Extracellular Matrix Structure[edit | edit source]
Tendons consist of mainly type 1 collagen fibres (but there are others present) and proteoglycan. The type 1 collagen fibres are responsible for the tensile strength of the tendon whereas the proteoglycan are responsible for the viscoelastic nature of the tendon.
The orientation of the collagen fibres in tendons have been found to run; parallel, simply crossing, crossing of two fibres with one straight, a plait formation of three fibres and an up typing of two parallel running fibres. The orientation and organisation of collagen fibres differs from tendon to tendon and vary in location of the tendon. This is dependent on the requirement of each tendon. For example tendons that need to resist rotational tensile forces will have a collagen fibre orientation to enable this.
The collagen molecules consist of polypeptide chains, three of these chains combined together form a densely packed helical tropocollagen molecule. Five of these combined together form a microfibril. The microfibrils then aggregate together to form fibrils. These are then grouped into fibres and fibres into fibre bundles and then into fascicles.
The fascicles are small in diameter in the young but as they mature into you adulthood they grow in size, peaking in size between the ages of 20-29 years old. As the tendon progressively ages the diameter becomes smaller, this has been linked to a possibility in the decreased strength of the muscle. It has also been noted that the diameter can shrink in size if the tendon becomes injured. [2][8]
Blood Supply[edit | edit source]
Innervation[edit | edit source]
The surrounding Structure[edit | edit source]
The structures surrounding the tendon can be split into 5 subcategories. The main aim of these structures is to reduce friction and enable the tendon to glide smoothly. This is an important factor for ensuring the transitions of the force is at its most efficient. These structures are:
- The retinaculum / fibrous sheaths
- The reflection pulleys
- The synovial sheaths
- The peritendinous sheet (paratenon)
- The tendon bursae[1]
References[edit | edit source]
- ↑ 1.0 1.1 1.2 1.3 Kannus P. Structure of the tendon connective tissue. Scandinavian Journal of Medicine &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp; Science in Sports. 2000; 10: 312-320. Cite error: Invalid
<ref>tag; name "Kannus 2000" defined multiple times with different content Cite error: Invalid<ref>tag; name "Kannus 2000" defined multiple times with different content Cite error: Invalid<ref>tag; name "Kannus 2000" defined multiple times with different content - ↑ 2.0 2.1 Benjamin M, kaiser E, Milz. Structure-function relationships in tendons: a review. Journal of Anatomy 2008; 212: 211-228
- ↑ Sharma P, Maffulli N. Biology of tendon injury: healing, modeling and remodeling. Journal of Musculoskeletal Neuronal Interact. 2006; 6 (2): 181-190.
- ↑ Maeda E, Shangjun Y, Wang W, Bader DL, Knight MM, Lee DA. Gap junction permability between tenocytes within tendon fasciles is supported by tensile loading. Journal of Biomechinical Model Mechanobiol 2012; 11:439-447
- ↑ Goldberg GS, Lampe PD, Nicholson BJ. Selective transfer of endogenous metabolites through gap junctions composed of different connexins. Nature Cell Biology 1999; 1:457–459.
- ↑ Wagett AD, Benjamin M, Ralphs JR. Connexin 32 and 43 gap junctions differentially modulate tenocyte response to cyclic mechanical load. European Journal of Cell Biology 2006 85:1145–1154
- ↑ Banes AJ, Weinhold P, Yang X, Tsuzaki M, Bynum D, Bottlang M, Brown T. Gap junctions regulate responses of tendon cells ex vivo to mechanical loading. Clinical Orthopaedics and Related Research 1999; 367:356–370
- ↑ Sharma P, Maffulli N. Biology of tendon injury: healing, modeling and remodeling. Journal of Musculoskeletal Neuronal Interact. 2006; 6 (2): 181-190.
