Muscle
This article is missing information about type 1 versus type 2 fibres.(December 2023) |
This article needs more primary sources. (May 2023) |
Muscle | |
---|---|
Identifiers | |
MeSH | D009132 |
TA98 | A04.0.00.000 |
TA2 | 1975 |
FMA | 5022 30316, 5022 |
Anatomical terminology |
Muscle is a
Muscle tissue varies with function and location in the body. In
The different muscle types vary in their response to
Sub-categorization of muscle tissue is also possible, depending on among other things the content of
Etymology
The word muscle comes from Latin musculus, diminutive of mus meaning mouse, because the appearance of the flexed biceps resembles the back of a mouse.
The same phenomenon occurred in Greek, in which μῦς, mȳs, means both "mouse" and "muscle".
Structure
There are three types of muscle tissue in vertebrates: skeletal, cardiac, and smooth. Skeletal and cardiac muscle are types of striated muscle tissue.[1] Smooth muscle is non-striated.
There are three types of muscle tissue in invertebrates that are based on their pattern of striation: transversely striated, obliquely striated, and smooth muscle. In arthropods there is no smooth muscle. The transversely striated type is the most similar to the skeletal muscle in vertebrates.[2]
Vertebrate skeletal muscle tissue is an elongated striated muscle tissue with the fibres ranging in width from three to eight micrometers and in length from 18 to 200 micrometers. In the uterine wall during pregnancy they enlarge in length from 70 to 500 micrometers.[3] Skeletal striated muscle tissue is arranged in regular, parallel bundles of myofibrils containing the many contractile units known as sarcomeres, which give the tissue its striated (striped) appearance. Skeletal muscle, is voluntary muscle anchored by tendons or sometimes by aponeuroses to bones, and is used to effect skeletal movement such as locomotion and to maintain posture. Postural control is generally maintained as an unconscious reflex, but the muscles responsible can also react to conscious control. An average adult man is made up of 42% of skeletal muscle as a percentage of body mass, and an average adult woman is made up of 36%.[4]
Cardiac muscle tissue, is found only in the walls of the
Smooth muscle tissue is non-striated and involuntary. Smooth muscle is found within the walls of organs and structures such as the
Comparison of types
smooth muscle | cardiac muscle | skeletal muscle | |
Anatomy | |||
Neuromuscular junction | none | present | |
Fibers | fusiform, short (<0.4 mm) | branching | cylindrical, long (<15 cm) |
Mitochondria | numerous | many to few (by type) | |
Nuclei | 1 | 1 | >1 |
Sarcomeres | none | present, max. length 2.6 µm | present, max. length 3.7 µm |
Syncytium | none (independent cells) | none (but functional as such) | present |
Sarcoplasmic reticulum
|
little elaborated | moderately elaborated | highly elaborated |
ATPase | little | moderate | abundant |
Physiology | |||
Self-regulation | spontaneous action (slow) | yes (rapid) | none (requires nerve stimulus) |
Response to stimulus | unresponsive | "all-or-nothing" | "all-or-nothing" |
Action potential | yes | yes | yes |
Workspace | Force/length curve is variable | the increase in the force/length curve | at the peak of the force/length curve |
Response to stimulus |
Skeletal muscle
Skeletal muscle is broadly classified into two fiber types:
- Type I, slow-twitch, slow oxidative, or red muscle is dense with aerobicactivity.
- Type II, fast-twitch muscle, has three major kinds that are, in order of increasing contractile speed:[5][6]
- Type IIa, which, like a slow muscle, is aerobic, rich in mitochondria and capillaries and appears red when deoxygenated.
- Type IIx (also known as type IId), which is less dense in mitochondria and myoglobin. This is the fastest muscle type in humans. It can contract more quickly and with a greater amount of force than oxidative muscle but can sustain only short, anaerobic bursts of activity before muscle contraction becomes painful (often incorrectly attributed to a build-up of lactic acid). N.B. in some books and articles this muscle in humans was, confusingly, called type IIB.[7]
- Type IIb, which is anaerobic, glycolytic, "white" muscle that is even less dense in mitochondria and myoglobin. In small animals like rodents, this is the major fast muscle type, explaining the pale color of their flesh.
The density of mammalian skeletal muscle tissue is about 1.06 kg/liter.[8] This can be contrasted with the density of adipose tissue (fat), which is 0.9196 kg/liter.[9] This makes muscle tissue approximately 15% denser than fat tissue.
Skeletal muscle is a highly oxygen consuming tissue, and oxidative DNA damage that is induced by reactive oxygen species tends to accumulate with age.[10] The oxidative DNA damage 8-OHdG accumulates in heart and skeletal muscle of both mouse and rat with age.[11] Also, DNA double-strand breaks accumulate with age in the skeletal muscle of mice.[12]
Smooth muscle
Smooth muscle is found within the walls of
Cardiac muscle
Cardiac muscle is involuntary,
Coordinated
Cardiac muscle cells, unlike most other tissues in the body, rely on an available blood and electrical supply to deliver oxygen and nutrients and remove waste products such as carbon dioxide. The coronary arteries help fulfill this function.
Development
All muscles are derived from
During development,
Function
The primary function of muscle tissue is contraction. The three types of muscle tissue (skeletal, cardiac and smooth) have significant differences. However, all three use the movement of actin against myosin to create contraction.
Skeletal muscle
In skeletal muscle, contraction is stimulated by electrical impulses transmitted by the motor nerves. Cardiac and smooth muscle contractions are stimulated by internal pacemaker cells which regularly contract, and propagate contractions to other muscle cells they are in contact with. All skeletal muscle and many smooth muscle contractions are facilitated by the neurotransmitter acetylcholine.
Smooth muscle
Smooth muscle is found in almost all
Cardiac muscle
Cardiac muscle is the muscle of the heart. It is self-contracting, autonomically regulated and must continue to contract in a rhythmic fashion for the whole life of the organism. Hence it has special features.
Invertebrate muscle
There are three types of muscle tissue in invertebrates that are based on their pattern of striation: transversely striated, obliquely striated, and smooth muscle. In arthropods there is no smooth muscle. The transversely striated type is the most similar to the skeletal muscle in vertebrates.[2]
References
- ^ doi:10.1002/9780470015902.a0026598. Retrieved 24 April 2023.)
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(help - ^ PMID 8720463.
- ^ Hugh Potter, Summary of muscle tissue "Muscle Tissue". Archived from the original on 2014-10-21. Retrieved 2014-09-02.
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: CS1 maint: bot: original URL status unknown (link) - ISBN 978-0-8053-5387-7.
- PMID 1858863.
- PMID 27199166.
- PMID 7545970. Note: Access to full text requires subscription; abstract freely available
- PMID 11320099.
- S2CID 46736884.
- ^ Bou Saada Y, Zakharova V, Chernyak B, Dib C, Carnac G, Dokudovskaya S, Vassetzky YS. Control of DNA integrity in skeletal muscle under physiological and pathological conditions. Cell Mol Life Sci. 2017 Oct;74(19):3439-3449. doi: 10.1007/s00018-017-2530-0. Epub 2017 Apr 25. PMID: 28444416
- ^ Hamilton, M. L.; Van Remmen, H.; Drake, J. A.; Yang, H.; Guo, Z. M.; Kewitt, K.; Walter, C. A.; Richardson, A. (August 2001). "Does oxidative damage to DNA increase with age?". Proceedings of the National Academy of Sciences of the United States of America. 98 (18): 10469–10474. Bibcode:2001PNAS...9810469H. doi:10.1073/pnas.171202698. PMC 56984. PMID 11517304
- ^ Park SJ, Gavrilova O, Brown AL, Soto JE, Bremner S, Kim J, Xu X, Yang S, Um JH, Koch LG, Britton SL, Lieber RL, Philp A, Baar K, Kohama SG, Abel ED, Kim MK, Chung JH. DNA-PK Promotes the Mitochondrial, Metabolic, and Physical Decline that Occurs During Aging. Cell Metab. 2017 May 2;25(5):1135-1146.e7. doi: 10.1016/j.cmet.2017.04.008. Erratum in: Cell Metab. 2017 Aug 1;26(2):447. PMID: 28467930; PMCID: PMC5485859
- PMID 8841934.
- )
- ^ ISBN 9780070633087.