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Related Concept Videos

Skeletal Muscle Anatomy00:55

Skeletal Muscle Anatomy

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Skeletal muscle is the most abundant type of muscle in the body. Tendons are the connective tissue that attaches skeletal muscle to bones. Skeletal muscles pull on tendons, which in turn pull on bones to carry out voluntary movements.
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Gross Anatomy of Skeletal Muscles01:12

Gross Anatomy of Skeletal Muscles

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The connective tissues play a significant role in arranging the muscle fibers into a hierarchical structure that forms a complete muscle. Consider a muscle like the bicep brachii, commonly called the bicep. This muscle comprises thousands of muscle fibers enclosed by a protective layer of connective tissue called the endomysium. The endomysium is primarily composed of reticular fibers, a type of thin collagen fiber. It allows the exchange of nutrients and waste products at the fiber level,...
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Overview of Skeletal Muscle01:15

Overview of Skeletal Muscle

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Skeletal muscles are composed of a bundle of muscle fibers and are attached to bones through tendons. Each skeletal muscle fiber is a single muscle cell. The sarcolemma, the plasma membrane of a skeletal muscle cell, consists of a lipid bilayer and glycocalyx that supports muscle fibers. The sarcolemma extends into the muscle cells to form tubular structures called transverse or T-tubules. Each side of the T-tubules consists of a membrane-bound structure called the sarcoplasmic reticulum,...
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Axial and Appendicular Muscles01:18

Axial and Appendicular Muscles

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Skeletal muscles, the key players in our body's movement, can be classified into two groups based on their location and function: axial muscles and appendicular muscles. These classifications reflect the primary roles the muscles play in the body's structure and movement.
Axial Muscles
Axial muscles, situated along the body's midline, are intricately connected to the axial skeleton, which includes the skull, spine, ribs, and sternum. These muscles facilitate facial expressions and...
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Microscopic Anatomy of Skeletal Muscles01:13

Microscopic Anatomy of Skeletal Muscles

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Skeletal muscle cells, also called muscle fibers, are distinctly elongated, multi-nucleated, slender biological units. They are packed with specialized structures designed to facilitate their primary function, which is contraction.
The muscle sarcolemma is a plasma membrane enclosing each muscle cell that conducts electrical signals called action potentials. The sarcolemma extends into the cell to form T-tubules, ensuring the neural impulses are uniformly distributed across the entire muscle...
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Relaxation of Skeletal Muscles01:29

Relaxation of Skeletal Muscles

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The period of muscle contraction primarily influences the duration of stimulation at the neuromuscular junction (NMJ), the presence of free calcium ions in the sarcoplasm, and the availability of energy or ATP to support contractions.
When an action potential reaches the axon terminal, it depolarizes the membrane and opens voltage-gated sodium channels. Sodium ions enter the cell, further depolarizing the presynaptic membrane. This depolarization causes voltage-gated calcium channels to open....
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Updated: Nov 16, 2025

Assessment of Global Ocular Structure Following Spaceflight Using a Micro-Computed Tomography Micro-CT Imaging Method
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Trunk Skeletal Muscle Changes on CT with Long-Duration Spaceflight.

Katelyn A Greene1, Shanna S Withers1, Leon Lenchik2

  • 1Department of Biomedical Engineering, Center for Injury Biomechanics, Wake Forest School of Medicine, Winston-Salem, NC, 27101, USA.

Annals of Biomedical Engineering
|February 19, 2021
PubMed
Summary

Astronauts experience trunk muscle loss in microgravity, but it recovers within 1-4 years post-flight. Advanced imaging like CT is crucial for detecting these changes, which DXA may miss.

Keywords:
AstronautComputed tomographyCross-sectional areaMicrogravityMuscle atrophyMuscle attenuation

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Area of Science:

  • Space medicine
  • Human physiology
  • Musculoskeletal research

Background:

  • Extended microgravity exposure can lead to astronaut trunk muscle atrophy.
  • This muscle loss may impair astronaut strength and function during space missions and upon return.
  • Understanding these changes is vital for astronaut health and mission success.

Purpose of the Study:

  • To investigate the effects of long-duration spaceflight on trunk skeletal muscle size and composition.
  • To compare the efficacy of computed tomography (CT) and dual-energy X-ray absorptiometry (DXA) in assessing microgravity-induced muscle changes.
  • To determine the recovery timeline of trunk muscle mass after spaceflight.

Main Methods:

  • 16 astronauts (4-6 month missions) underwent CT and DXA scans pre-flight, post-flight, and 1-4 years later.
  • Trunk muscle cross-sectional area and attenuation were measured via CT.
  • Height-normalized skeletal muscle indices were calculated and analyzed for changes.

Main Results:

  • Trunk muscle area significantly decreased by 4.7% post-flight, recovering within 1-4 years.
  • CT-derived skeletal muscle index showed a significant decrease, unlike DXA-derived appendicular skeletal muscle index.
  • Muscle attenuation changes were not statistically significant.

Conclusions:

  • Long-duration microgravity causes trunk muscle atrophy in astronauts.
  • Trunk muscle mass recovers to pre-flight levels within 1-4 years after spaceflight.
  • CT imaging is more sensitive than DXA for detecting microgravity-induced trunk muscle size reduction.