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Muscleis asoft tissue,one of the four basic types ofanimal tissue.Muscle tissue givesskeletal musclesthe ability tocontract.Muscle is formed duringembryonic development,in a process known asmyogenesis.Muscle tissue contains specialcontractile proteinscalledactinandmyosinwhich interact to cause movement. Among many other muscle proteins, present are tworegulatory proteins,troponinandtropomyosin.[1]
| Muscle | |
|---|---|
 Three distinct types of muscle (L to R): smooth (non-striated), cardiac, and skeletal muscle | |
| Identifiers | |
| MeSH | D009132 |
| TA2 | 1975,1994 |
| FMA | 5022 30316, 5022 |
| Anatomical terminology | |
Muscle tissue varies with function and location in the body.
Invertebrates,the three types are:
- skeletal,
- cardiac(bothstriated), and
- smooth muscle(non-striated).[2]
Skeletal muscle tissueconsists of elongated, multinucleatemuscle cellscalledmuscle fibers,and is responsible for movements of the body. Other tissues in skeletal muscle includetendonsandperimysium.[3]Smooth and cardiac muscle contract involuntarily, without conscious intervention. These muscle types may be activated both through the interaction of thecentral nervous systemas well as by receiving innervation from peripheralplexusorendocrine(hormonal) activation. Striated or skeletal muscle only contracts voluntarily, upon the influence of the central nervous system.Reflexesare a form of non-conscious activation of skeletal muscles, but nonetheless arise through activation of the central nervous system, albeit not engagingcorticalstructures until after the contraction has occurred.[citation needed]
The different muscle types vary in their response toneurotransmittersandhormonessuch asacetylcholine,noradrenaline,adrenaline,andnitric oxidedepending on muscle type and the exact location of the muscle.[citation needed]
Sub-categorization of muscle tissue is also possible, depending on among other things the content ofmyoglobin,mitochondria,andmyosin ATPaseetc.[citation needed]
Etymology
editThe wordmusclecomes from Latinmusculus,diminutive ofmusmeaningmouse,because the appearance of the flexed biceps resembles the back of a mouse.
The same phenomenon occurred inGreek,in which μῦς,mȳs,means both "mouse" and "muscle".
Structure
editThere are three types of muscle tissue in vertebrates:skeletal,cardiac,andsmooth.Skeletal and cardiac muscle are types ofstriated muscle tissue.[2]Smooth muscle is non-striated.
There are three types of muscle tissue ininvertebratesthat 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.[4]
Vertebrate skeletal muscle tissue is an elongated, striated muscle tissue, with the fibres ranging from 3-8 micrometers in width and from 18 to 200 micrometers in breadth. In the uterine wall, during pregnancy, they enlarge in length from 70 to 500 micrometers.[5]Skeletal striated muscle tissue is arranged in regular, parallel bundles ofmyofibrils,which contain many contractile units known assarcomeres,which give the tissue its striated (striped) appearance. Skeletal muscle is voluntary muscle, anchored bytendonsor sometimes byaponeurosestobones,and is used to effectskeletalmovement such aslocomotionand tomaintain posture.Postural control is generally maintained as an unconscious reflex, but the responsible muscles can also react to conscious control. The body mass of an average adult man is made up of 42% of skeletal muscle, and an average adult woman is made up of 36%.[6]
Cardiac muscle tissue is found only in the walls of theheartasmyocardium,and it is an involuntary muscle controlled by theautonomic nervous system.Cardiac muscle tissue is striated like skeletal muscle, containing sarcomeres in highly regular arrangements of bundles. While skeletal muscles are arranged in regular, parallel bundles, cardiac muscle connects at branching, irregular angles known asintercalated discs.
Smooth muscle tissue is non-striated and involuntary. Smooth muscle is found within the walls of organs and structures such as theesophagus,stomach,intestines,bronchi,uterus,urethra,bladder,blood vessels,and thearrector piliin the skin that control the erection of body hair.
Comparison of types
edit| 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 | 
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|
|
Skeletal muscle
edit
Skeletal muscle is broadly classified into two fiber types:type I(slow-twitch) andtype II(fast-twitch).
- Type I, slow-twitch,slow oxidative, orredmuscle is dense withcapillariesand is rich inmitochondriaandmyoglobin,giving the muscle tissue its characteristic red color. It can carry moreoxygenand sustainaerobicactivity.
- Type II, fast-twitch muscle,has three major kinds that are, in order of increasing contractile speed:[7][8]
- 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,anaerobicbursts of activity before muscle contraction becomes painful (often incorrectly attributed to a build-up oflactic acid). N.B. in some books and articles this muscle in humans was, confusingly, called type IIB.[9]
- 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. In laboratory house mice, an intronic single nucleotide polymorphism in theMyosin heavy polypeptide 4gene[10]causes a great reduction in the amount of Type IIb muscle, yielding the "Mini-Muscle" phenotype, which was discovered based on its greatly reduced (~50%) hind-limb muscle mass.
Thedensityof mammalian skeletal muscle tissue is about 1.06 kg/liter.[11]This can be contrasted with the density ofadipose tissue(fat), which is 0.9196 kg/liter.[12]This makes muscle tissue approximately 15% denser than fat tissue.
Skeletal muscleis a highly oxygen-consuming tissue, andoxidative DNA damagethat is induced byreactive oxygen speciestends to accumulate withage.[13]The oxidative DNA damage8-OHdGaccumulates inheartand skeletal muscle of both mouse and rat with age.[14]Also, DNA double-strand breaks accumulate with age in the skeletal muscle of mice.[15]
Smooth muscle
editSmooth muscleis involuntary and non-striated. It is divided into two subgroups: thesingle-unit(unitary) andmultiunit smooth muscle.Within single-unit cells, the whole bundle or sheet contracts as asyncytium(i.e. amultinucleatemass ofcytoplasmthat is not separated into cells). Multiunit smooth muscle tissuesinnervateindividual cells; as such, they allow for fine control and gradual responses, much likemotor unit recruitmentin skeletal muscle.
Smooth muscle is found within the walls ofblood vessels(such smooth muscle specifically being termedvascular smooth muscle) such as in thetunica medialayer of the large (aorta) and smallarteries,arteriolesandveins.Smooth muscle is also found in lymphatic vessels, theurinary bladder,uterus(termeduterine smooth muscle), male and femalereproductive tracts,thegastrointestinal tract,therespiratory tract,the arrector pili ofskin,theciliary muscle,and theiris of the eye.The structure and function is basically the same in smooth muscle cells in different organs, but the inducing stimuli differ substantially, in order to perform individual actions in the body at individual times. In addition, theglomeruliof the kidneys contain smooth muscle-like cells calledmesangial cells.
Cardiac muscle
editCardiac muscle is involuntary,striated musclethat is found in the walls and thehistologicalfoundation of theheart,specifically the myocardium. Thecardiac muscle cells,(also called cardiomyocytes or myocardiocytes), predominantly contain only one nucleus, although populations with two to four nuclei do exist.[16][17][page needed]Themyocardiumis the muscle tissue of the heart and forms a thick middle layer between the outerepicardiumlayer and the innerendocardiumlayer.
Coordinatedcontractionsof cardiac muscle cells in the heart propelbloodout of theatriaandventriclesto the blood vessels of the left/body/systemic and right/lungs/pulmonarycirculatory systems.This complex mechanism illustratessystoleof the heart.
Cardiac muscle cells, unlike most other tissues in the body, rely on an available blood and electrical supply to deliver oxygen and nutrients and to remove waste products such ascarbon dioxide.Thecoronary arterieshelp fulfill this function.
Development
edit
All muscles are derived fromparaxial mesoderm.The paraxial mesoderm is divided along theembryo's length intosomites,corresponding to thesegmentationof the body (most obviously seen in thevertebral column.[18]Each somite has three divisions,sclerotome(which formsvertebrae),dermatome(which forms skin), andmyotome(which forms muscle). The myotome is divided into two sections, the epimere and hypomere, which formepaxial and hypaxial muscles,respectively. The only epaxial muscles in humans are theerector spinaeand small intervertebral muscles, and are innervated by the dorsal rami of thespinal nerves.All other muscles, including those of the limbs are hypaxial, and innervated by theventral ramiof the spinal nerves.[18]
During development,myoblasts(muscle progenitor cells) either remain in the somite to form muscles associated with the vertebral column or migrate out into the body to form all other muscles. Myoblast migration is preceded by the formation ofconnective tissueframeworks, usually formed from the somaticlateral plate mesoderm.Myoblasts follow chemical signals to the appropriate locations, where they fuse into elongate skeletal muscle cells.[18]
Function
editThe primary function of muscle tissue iscontraction.The three types of muscle tissue (skeletal, cardiac and smooth) have significant differences. However, all three use the movement ofactinagainstmyosinto create contraction.
Skeletal muscle
editIn skeletal muscle, contraction is stimulated byelectrical impulsestransmitted by themotor 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 theneurotransmitteracetylcholine.[19]
Smooth muscle
editSmooth muscle is found in almost allorgan systemssuch ashollow organsincluding thestomach,andbladder;in tubular structures such asbloodandlymph vessels,andbile ducts;in sphincters such as in the uterus, and the eye. In addition, it plays an important role in the ducts of exocrine glands. It fulfills various tasks such as sealing orifices (e.g. pylorus, uterine os) or the transport of the chyme through wavelike contractions of the intestinal tube. Smooth muscle cells contract more slowly than skeletal muscle cells, but they are stronger, more sustained and require less energy. Smooth muscle is also involuntary, unlike skeletal muscle, which requires a stimulus.
Cardiac muscle
editCardiac muscle is the muscle of the heart. It is self-contracting,autonomically regulatedand must continue to contract in a rhythmic fashion for the whole life of the organism. Hence it has special features.[20]
Invertebrate muscle
editThere are three types of muscle tissue ininvertebratesthat are based on their pattern ofstriation: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.[4]
References
edit- ^Ebashi, S.; Endo, M. (1968)."Calcium ion and muscle contraction".Progress in Biophysics and Molecular Biology.18:123–183.doi:10.1016/0079-6107(68)90023-0.ISSN0079-6107.PMID4894870.
- ^abRobson, Lesley G. (2017)."Vertebrate Embryo: Myogenesis and Muscle Development".eLS.Wiley. pp. 1–10.doi:10.1002/9780470015902.a0026598.ISBN9780470015902.
- ^Dave, Heeransh D.; Shook, Micah; Varacallo, Matthew (2024),"Anatomy, Skeletal Muscle",StatPearls,Treasure Island (FL): StatPearls Publishing,PMID30725921,retrieved2024-04-22
- ^abPaniagua, R; Royuela, M; García-Anchuelo, RM; Fraile, B (January 1996). "Ultrastructure of invertebrate muscle cell types".Histology and Histopathology.11(1): 181–201.PMID8720463.
- ^Potter, Hugh."Muscle Tissue".Archived fromthe originalon 2014-10-21.Retrieved2014-09-02.
- ^Marieb, Elaine; Hoehn, Katja (2007).Human Anatomy & Physiology(7th ed.). Pearson Benjamin Cummings. p. 317.ISBN978-0-8053-5387-7.
- ^Larsson, L; Edström, L; Lindegren, B; Gorza, L; Schiaffino, S (July 1991). "MHC composition and enzyme-histochemical and physiological properties of a novel fast-twitch motor unit type".The American Journal of Physiology.261(1 pt 1): C93–101.doi:10.1152/ajpcell.1991.261.1.C93.PMID1858863.
- ^Talbot, J; Maves, L (July 2016)."Skeletal muscle fiber type: using insights from muscle developmental biology to dissect targets for susceptibility and resistance to muscle disease".Wiley Interdisciplinary Reviews. Developmental Biology.5(4): 518–34.doi:10.1002/wdev.230.PMC5180455.PMID27199166.
- ^Smerdu, V; Karsch-Mizrachi, I; Campione, M; Leinwand, L; Schiaffino, S (December 1994). "Type IIx myosin heavy chain transcripts are expressed in type IIb fibers of human skeletal muscle".The American Journal of Physiology.267(6 pt 1): C1723–8.doi:10.1152/ajpcell.1994.267.6.C1723.PMID7545970.Note: Access to full text requires subscription; abstract freely available
- ^Kelly SA, Bell TA, Selitsky SR, Buus RJ, Hua K, Weinstock GM, Garland T, Pardo-Manuel de Villena F, Pomp D (December 2013)."A novel intronic single nucleotide polymorphism in the myosin heavy polypeptide 4 gene is responsible for the mini-muscle phenotype characterized by major reduction in hind-limb muscle mass in mice".Genetics.195(4): 1385–95.doi:10.1534/genetics.113.154476.PMC3832280.PMID24056412.
- ^Urbancheka, M; Picken, E; Kalliainen, L; Kuzon, W (2001)."Specific Force Deficit in Skeletal Muscles of Old Rats Is Partially Explained by the Existence of Denervated Muscle Fibers".The Journals of Gerontology Series A: Biological Sciences and Medical Sciences.56(5): B191–7.doi:10.1093/gerona/56.5.B191.PMID11320099.
- ^Farvid, MS; Ng, TW; Chan, DC; Barrett, PH; Watts, GF (2005). "Association of adiponectin and resistin with adipose tissue compartments, insulin resistance and dyslipidaemia".Diabetes, Obesity & Metabolism.7(4): 406–413.doi:10.1111/j.1463-1326.2004.00410.x.PMID15955127.S2CID46736884.
- ^Bou Saada Y, Zakharova V, Chernyak B, Dib C, Carnac G, Dokudovskaya S, Vassetzky YS (October 2017)."Control of DNA integrity in skeletal muscle under physiological and pathological conditions".Cell Mol Life Sci.74(19): 3439–49.doi:10.1007/s00018-017-2530-0.PMC11107590.PMID28444416.
- ^Hamilton ML, Van Remmen H, Drake JA, Yang H, Guo ZM, Kewitt K, Walter CA, Richardson A (August 2001)."Does oxidative damage to DNA increase with age?".Proc Natl Acad Sci U S A.98(18): 10469–74.Bibcode:2001PNAS...9810469H.doi:10.1073/pnas.171202698.PMC56984.PMID11517304.
- ^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 (May 2017)."DNA-PK Promotes the Mitochondrial, Metabolic, and Physical Decline that Occurs During Aging".Cell Metab.25(5): 1135–46.e7.doi:10.1016/j.cmet.2017.04.008.PMC5485859.PMID28467930.
- ^Olivetti G, Cigola E, Maestri R, et al. (July 1996). "Aging, cardiac hypertrophy and ischemic cardiomyopathy do not affect the proportion of mononucleated and multinucleated myocytes in the human heart".Journal of Molecular and Cellular Cardiology.28(7): 1463–77.doi:10.1006/jmcc.1996.0137.PMID8841934.
- ^Pollard, Thomas D.; Earnshaw, William C.; Lippincott-Schwartz, Jennifer (2008).Cell Biology(2nd ed.). Philadelphia, PA: Saunders/Elsevier.ISBN978-1-4377-0063-3.OCLC489073468.
- ^abcSweeney, Lauren (1997).Basic Concepts in Embryology: A Student's Survival Guide.McGraw-Hill Professional.ISBN978-0-07-063308-7.OCLC606951249.
- ^Frontera, Walter R.; Ochala, Julien (March 2015)."Skeletal muscle: a brief review of structure and function".Calcified Tissue International.96(3): 183–195.doi:10.1007/s00223-014-9915-y.ISSN1432-0827.PMID25294644.
- ^Zile, M. R.; Richardson, K.; Cowles, M. K.; Buckley, J. M.; Koide, M.; Cowles, B. A.; Gharpuray, V.; Cooper, G. (1998-08-11)."Constitutive properties of adult mammalian cardiac muscle cells".Circulation.98(6): 567–579.doi:10.1161/01.cir.98.6.567.ISSN0009-7322.PMID9714115.
