Muscle

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Muscle
The body contains three types of muscle tissue: (a) skeletal muscle, (b) smooth muscle, and (c) cardiac muscle. (Same magnification)
A schematic diagram of the different types of muscle cells (same order as above)
Identifiers
MeSHD009132
TA98A04.0.00.000
TA21975
FMA5022 30316, 5022
Anatomical terminology

Muscle is a

regulatory proteins, troponin and tropomyosin
.

Muscle tissue varies with function and location in the body. In

muscle fibers, and is responsible for movements of the body. Other tissues in skeletal muscle include tendons and perimysium.[citation needed] Smooth and cardiac muscle contract involuntarily, without conscious intervention. These muscle types may be activated both through the interaction of the central nervous system as well as by receiving innervation from peripheral plexus or endocrine (hormonal) activation. Striated or skeletal muscle only contracts voluntarily, upon the influence of the central nervous system. Reflexes are a form of non-conscious activation of skeletal muscles, but nonetheless arise through activation of the central nervous system, albeit not engaging cortical structures until after the contraction has occurred.[citation needed
]

The different muscle types vary in their response to

noradrenaline, adrenaline, and nitric oxide depending 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 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

Three distinct types of muscle (L to R): Smooth (non-striated) muscle in internal organs, cardiac or heart muscle, and skeletal muscle.

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

myocardium, and is an involuntary muscle controlled by the autonomic nervous system. Cardiac muscle tissue is striated like skeletal muscle, containing contractile units called sarcomeres in highly regular arrangements of bundles. While skeletal muscles are arranged in regular, parallel bundles, cardiac muscle connects at branching, irregular angles known as intercalated discs
.

Smooth muscle tissue is non-striated and involuntary. Smooth muscle is found within the walls of organs and structures such as the

arrector pili
in the skin which controls the erection of body hair.

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

Striated skeletal muscle cells in microscopic view. The myofibers are the straight vertical bands; the horizontal striations (lighter and darker bands) that are a visible result from differences in composition and density along the fibrils within the cells. The cigar-like dark patches beside the myofibers are muscle-cell nuclei.

Skeletal muscle is broadly classified into two fiber types:

Type II fast-twitch muscle
.

  • Type I, slow-twitch, slow oxidative, or red muscle is dense with
    aerobic
    activity.
  • 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

multiunit smooth muscle. Within single-unit cells, the whole bundle or sheet contracts as a syncytium (i.e. a multinucleate
mass of cytoplasm that is not separated into cells). Multiunit smooth muscle tissues innervate individual cells; as such, they allow for fine control and gradual responses, much like motor unit recruitment in skeletal muscle.

Smooth muscle is found within the walls of

reproductive tracts, gastrointestinal tract, respiratory tract, arrector pili of skin, the ciliary muscle, and iris 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 effects in the body at individual times. In addition, the glomeruli of the kidneys contain smooth muscle-like cells called mesangial cells
.

Cardiac muscle

Cardiac muscle is involuntary,

epicardium layer and the inner endocardium
layer.

Coordinated

systole
of 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 remove waste products such as carbon dioxide. The coronary arteries help fulfill this function.

Development

A chicken embryo, showing the paraxial mesoderm on both sides of the neural fold. The anterior (forward) portion has begun to form somites (labeled "primitive segments").

All muscles are derived from

ventral rami of the spinal nerves.[15]

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 of connective tissue frameworks, usually formed from the somatic lateral plate mesoderm. Myoblasts follow chemical signals to the appropriate locations, where they fuse into elongate skeletal muscle cells.[15]

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

lymph vessels, and bile 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

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

  1. ^
    doi:10.1002/9780470015902.a0026598. Retrieved 24 April 2023. {{cite journal}}: Cite journal requires |journal= (help
    )
  2. ^ .
  3. ^ Hugh Potter, Summary of muscle tissue "Muscle Tissue". Archived from the original on 2014-10-21. Retrieved 2014-09-02.{{cite web}}: CS1 maint: bot: original URL status unknown (link)
  4. .
  5. .
  6. .
  7. . Note: Access to full text requires subscription; abstract freely available
  8. .
  9. .
  10. ^ 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
  11. ^ 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
  12. ^ 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
  13. PMID 8841934
    .
  14. OCLC 489073468.{{cite book}}: CS1 maint: location missing publisher (link
    )
  15. ^ .