Overview of Smooth Muscles

Smooth muscle cells & skeletal muscles are distinct types of muscle tissues in the human body, each with specific functions and characteristics.

• Smooth muscle cells are responsible for involuntary movements and are found in various organ systems;
• Skeletal muscles are associated with voluntary movements and are attached to bones.

Smooth muscle cell dysfunction, an impairment in the standard functioning of smooth muscle cells, can lead to wide-ranging effects across various bodily systems.

These dysfunctions can be triggered by an array of factors including aging, genetic mutations, toxins, or pathology.

The ramifications of such dysfunctions are diverse and can lead to diseases or disorders throughout the body like the cardiovascular, gastrointestinal, respiratory, and urinary systems, among others.

How does smooth muscle cell dysfunction manifest across different bodily systems & what are the potential consequences?

• Cardiovascular System:
  • Vascular disorders: Conditions like atherosclerosis and hypertension stem from smooth muscle cell dysfunction affecting the elasticity and contractility of blood vessels, which in turn impacts blood flow & pressure regulation.
  • Vascular smooth muscle cell proliferation: Abnormal proliferation of vascular smooth muscle cells is a key feature of many vascular diseases, contributing to the narrowing of blood vessels.
• Urinary System:
  • Urinary Retention and Incontinence: Impaired smooth muscle function in the bladder and urethra can result in urinary retention or incontinence, affecting an individual’s ability to control urine release.
  • Bladder Dysfunction: Conditions like overactive bladder or underactive bladder can arise.
• Reproductive System:
  • Uterine and Oviduct Function: Smooth muscle dysfunction can affect uterine contractions and oviduct transport, which may impact fertility, childbirth, and menstrual cycles.
  • Erectile Dysfunction: Impaired smooth muscle function in reproductive organs can also lead to conditions like erectile dysfunction.

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• Gastrointestinal System:
  • Motility Disorders: Conditions like irritable bowel syndrome (IBS) and gastroparesis may arise due to impaired smooth muscle contraction and relaxation affecting gastrointestinal motility.
  • Nutrient Absorption: Impaired smooth muscle function can lead to inadequate mixing of food with digestive enzymes, impacting nutrient absorption.
• Endocrine Implications:
  • Hormones such as oxytocin and estrogen play a role in modulating the activity of smooth muscle cells across various tissues.
  • For instance, oxytocin stimulates the contraction of uterine smooth muscle cells during labor, while estrogen affects the tone and contractility of smooth muscle in various tissues, including the uterus and the gastrointestinal tract.

• Respiratory System:
  • Airway Hyper-responsiveness: Dysfunctional smooth muscle cells in the respiratory system can lead to conditions like asthma and chronic obstructive pulmonary disease (COPD) by affecting the diameter of airways and thereby hindering airflow and oxygen exchange.
  • Chronic Bronchitis: The chronic inflammation and constriction of airways can also lead to chronic bronchitis.

Smooth muscle cells are amazing cells that demonstrate significant adaptability and plasticity, responding to diverse physiological conditions and requirements.

From a functional perspective, the physiology of smooth muscle is fundamental in sustaining and regulating each vital sign.

It is imperative to acknowledge that the ramifications of smooth muscle dysfunction are systemic, emphasizing that the term muscle encompasses both skeletal and smooth muscle, each with distinct & critical functionalities

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​In a previous episode of the ongoing Protein series, I talked about navigating protein intake beyond RDA. ​

​If you have missed it, you can read about it here:​

​Protein & Longevity Synergy: ​ ...The Recommended Dietary Allowance (RDA) for protein intake is a subject that has sparked considerable research and debate... ​ Read article

Disclaimer

This information is not medical advice or lifestyle advice. This content and other content on this website is for informational and educational purposes only and is not intended to be a substitute for lifestyle advice, medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition.

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References

• Eddinger TJ. "Smooth muscle-protein translocation and tissue function." Anat Rec (Hoboken), 2014 Sep; 297(9):1734-46.
• Li, X., Zhou, L., Zhang, X. et al. "Proteins secreted by brain arteriolar smooth muscle cells are instructive for neural development." Mol Brain, 15, 97 (2022).
• Zhang, DD., Song, Y., Kong, P. et al. "Smooth muscle 22 alpha protein inhibits VSMC foam cell formation by supporting normal LXRα signaling, ameliorating atherosclerosis." Cell Death Dis, 12, 982 (2021).
• Wang CC, Gurevich I, Draznin B. "Insulin affects vascular smooth muscle cell phenotype and migration via distinct signaling pathways." Diabetes, 2003 Oct; 52(10):2562-9.
• Hafen BB, Shook M, Burns B. "Anatomy, Smooth Muscle." [Updated 2023 Jul 17]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-.
• Hafen BB, Burns B. "Physiology, Smooth Muscle." [Updated 2023 Aug 14]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-.
• Turner WH, Brading AF. "Smooth muscle of the bladder in the normal and the diseased state: pathophysiology, diagnosis and treatment." Pharmacol Ther, 1997 Aug; 75(2):77-110.
• Arrowsmith S, Keov P, Muttenthaler M, Gruber CW. "Contractility Measurements of Human Uterine Smooth Muscle to Aid Drug Development." J Vis Exp, 2018 Jan 26;(131):56639.
• Ferreira JJ, Butler A, Stewart R, Gonzalez-Cota AL, Lybaert P, Amazu C, Reinl EL, Wakle-Prabagaran M, Salkoff L, England SK, Santi CM. "Oxytocin can regulate myometrial smooth muscle excitability by inhibiting the Na+ -activated K+ channel, Slo2.1." J Physiol, 2019 Jan; 597(1):137-149.
• Basatemur, G.L., Jørgensen, H.F., Clarke, M.C.H. et al. "Vascular smooth muscle cells in atherosclerosis." Nat Rev Cardiol, 16, 727–744 (2019).
• Zhuge Y, Zhang J, Qian F, Wen Z, Niu C, Xu K, Ji H, Rong X, Chu M, Jia C. "Role of smooth muscle cells in Cardiovascular Disease." Int J Biol Sci, 2020 Aug 21; 16(14):2741-2751.

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