Myotendinous Junction: Difference between revisions
(Created page with "{{Stub}} The myotendinous junction (MTJ) is the connection between muscle and tendon tissue. == Structure == The MTJ has finger-like processes with invaginations and evagin...") |
No edit summary |
||
| Line 1: | Line 1: | ||
{{Stub}} | {{Stub}} | ||
The myotendinous junction (MTJ) is the connection between muscle and tendon tissue. | The myotendinous junction (MTJ) is the connection between muscle and tendon tissue. The MTJ allows force that is generated by the muscle to be transmitted from the muscle filaments to the collagen fibres of the adjoining tendon. | ||
== Structure == | == Structure and Function == | ||
The MTJ has finger-like processes with invaginations and evaginations of the sarcolemma. | The MTJ has finger-like processes with invaginations and evaginations of the sarcolemma. The finger-like processes might have various functions. | ||
# It increases the surface area by 10-20 times compared to a planar surface, and in doing so decreases stress. | # It increases the surface area by 10-20 times compared to a planar surface, and in doing so decreases stress. | ||
# It also positions the membranes at very low angles relative to the applied stress, and in doing so it causes the membranes to be primarily subjected to shear stress. The adhesion strength is theoretically much higher during shear loading compared to tension loading. | # It also positions the membranes at very low angles relative to the applied stress, and in doing so it causes the membranes to be primarily subjected to shear stress. The adhesion strength is theoretically much higher during shear loading compared to tension loading. | ||
''Tendon'': The tendinous portion is made up of multidirectional collagen fibres. In the tendon the force is longitudinal hence orientation is also longitudinal here. However close to the muscle the force can be in many directions. This allows force transmission laterally via the endomysium to adjacent myofibres. | |||
''Muscle'': As the sarcomere extend towards the MTJ, they appear to change direction, with the longitudinal axis of the sarcomere becoming parallel with the major axis of the finger-like processes, allowing force transmission via shear as above. There is a final Z-line from the muscle fibre at the MTJ. The myofilaments extend from the final Z-line to merge with the tendon tissue. The myofilaments of the terminal sarcomeres insert into the plasma membrane through thin filaments only (likely actin). | |||
''Finger-like Processes'': The fingers are not seen in 3D reconstruction, as the fingers are a reflection of the way the tissue is cut. In 3D the structures may be more suitably named ridge-like protrusions and furrow-like indentations. The tendon tissue forms the ridge-like protrusions, and the myofibrils connect to the tendon tissue through these protrusions. The sarcomere run parallel to the ridge-like protrusions of the tendon.<ref>Knudsen AB, Larsen M, Mackey AL, Hjort M, Hansen KK, Qvortrup K, Kjaer M, Krogsgaard MR. The human myotendinous junction: an ultrastructural and 3D analysis study. Scand J Med Sci Sports. 2015 Feb;25(1):e116-23. doi: 10.1111/sms.12221. Epub 2014 Apr 10. PMID: 24716465.</ref> | |||
== Adaptation and Ageing == | |||
The MTJ is a dynamic structure that can adapt to mechanical stimuli. In rats that exercise regularly there are more branches from the finger-like processes compared to non-exercising rats. The angulation of the processes relative to the longitudinal direction also increased.<ref>Kojima H, Sakuma E, Mabuchi Y, Mizutani J, Horiuchi O, Wada I, Horiba M, Yamashita Y, Herbert DC, Soji T, Otsuka T. Ultrastructural changes at the myotendinous junction induced by exercise. J Orthop Sci 2008: 13 (3): 233–239</ref> | |||
In older rates, the finger-like processes are more irregular.<ref>Ciena AP, Yokomizo De Almeida SR, De Sousa Bolina C, De Sousa Bolina-Matos R, Grassi Rici RE, Pereira Da Silva MC, Miglino MA, Watanabe IS. Ultrastructural features of the myotendinous junction of the sternomastoid muscle in Wistar rats: from newborn to aging. Microsc Res Tech 2012: 75 (9): 1292–1296.</ref> | |||
== Injury == | == Injury == | ||
| Line 16: | Line 23: | ||
In atrophied muscle the contact area between muscle and tendon is reduced.<ref>de Palma L, Marinelli M, Bertoni-Freddari C. Involvement of the muscle-tendon junction in skeletal muscle atrophy: an ultrastructural study. Rom J Morphol Embryol 2011: 52 (1): 105–109.</ref> | In atrophied muscle the contact area between muscle and tendon is reduced.<ref>de Palma L, Marinelli M, Bertoni-Freddari C. Involvement of the muscle-tendon junction in skeletal muscle atrophy: an ultrastructural study. Rom J Morphol Embryol 2011: 52 (1): 105–109.</ref> | ||
== References == | |||
[[Category:Anatomy]] | [[Category:Anatomy]] | ||
Revision as of 16:48, 9 August 2021
The myotendinous junction (MTJ) is the connection between muscle and tendon tissue. The MTJ allows force that is generated by the muscle to be transmitted from the muscle filaments to the collagen fibres of the adjoining tendon.
Structure and Function
The MTJ has finger-like processes with invaginations and evaginations of the sarcolemma. The finger-like processes might have various functions.
- It increases the surface area by 10-20 times compared to a planar surface, and in doing so decreases stress.
- It also positions the membranes at very low angles relative to the applied stress, and in doing so it causes the membranes to be primarily subjected to shear stress. The adhesion strength is theoretically much higher during shear loading compared to tension loading.
Tendon: The tendinous portion is made up of multidirectional collagen fibres. In the tendon the force is longitudinal hence orientation is also longitudinal here. However close to the muscle the force can be in many directions. This allows force transmission laterally via the endomysium to adjacent myofibres.
Muscle: As the sarcomere extend towards the MTJ, they appear to change direction, with the longitudinal axis of the sarcomere becoming parallel with the major axis of the finger-like processes, allowing force transmission via shear as above. There is a final Z-line from the muscle fibre at the MTJ. The myofilaments extend from the final Z-line to merge with the tendon tissue. The myofilaments of the terminal sarcomeres insert into the plasma membrane through thin filaments only (likely actin).
Finger-like Processes: The fingers are not seen in 3D reconstruction, as the fingers are a reflection of the way the tissue is cut. In 3D the structures may be more suitably named ridge-like protrusions and furrow-like indentations. The tendon tissue forms the ridge-like protrusions, and the myofibrils connect to the tendon tissue through these protrusions. The sarcomere run parallel to the ridge-like protrusions of the tendon.[1]
Adaptation and Ageing
The MTJ is a dynamic structure that can adapt to mechanical stimuli. In rats that exercise regularly there are more branches from the finger-like processes compared to non-exercising rats. The angulation of the processes relative to the longitudinal direction also increased.[2]
In older rates, the finger-like processes are more irregular.[3]
Injury
Injuries to the MTJ are common. Failure occurs either at the muscle-tendon junction or in the muscle belly itself.
In atrophied muscle the contact area between muscle and tendon is reduced.[4]
References
- ↑ Knudsen AB, Larsen M, Mackey AL, Hjort M, Hansen KK, Qvortrup K, Kjaer M, Krogsgaard MR. The human myotendinous junction: an ultrastructural and 3D analysis study. Scand J Med Sci Sports. 2015 Feb;25(1):e116-23. doi: 10.1111/sms.12221. Epub 2014 Apr 10. PMID: 24716465.
- ↑ Kojima H, Sakuma E, Mabuchi Y, Mizutani J, Horiuchi O, Wada I, Horiba M, Yamashita Y, Herbert DC, Soji T, Otsuka T. Ultrastructural changes at the myotendinous junction induced by exercise. J Orthop Sci 2008: 13 (3): 233–239
- ↑ Ciena AP, Yokomizo De Almeida SR, De Sousa Bolina C, De Sousa Bolina-Matos R, Grassi Rici RE, Pereira Da Silva MC, Miglino MA, Watanabe IS. Ultrastructural features of the myotendinous junction of the sternomastoid muscle in Wistar rats: from newborn to aging. Microsc Res Tech 2012: 75 (9): 1292–1296.
- ↑ de Palma L, Marinelli M, Bertoni-Freddari C. Involvement of the muscle-tendon junction in skeletal muscle atrophy: an ultrastructural study. Rom J Morphol Embryol 2011: 52 (1): 105–109.
