Sarcopenia; Age Related Muscle Loss in Humans

2 months ago

At every stage in our life, from when we were fetus till we get old, we experience physiological changes and one of those changes is in our muscle. Muscle change is complex and while it adapts to how we use it, it also changes throughout the period of our life.

Muscles are one of the four types of tissues which includes Nervous tissue, epithelial tissue, and connective tissue and there are three types of muscles with different functions. The types include the Cardiac Muscles, Smooth Muscles, and the Skeletal Muscle with two of the muscles being Cardiac and Smooth muscles controlled involuntarily. The cardiac muscle is found around our heart while the smooth muscles are found in blood vessels and some other organs. I will be explaining the muscle that we have control over which is the skeletal muscle.

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The skeletal muscle is the largest group of tissue in the body which makes up a big chunk of our body weight. Muscle tissues is one of the tissue formed even as embryo. As embryos, the cells divide into endoderm, mesoderm, and ectoderm which are just the inner, middle and outer layer of the cell which later become different body tissues with the mesoderm becoming the tissue of the cardiovascular and reproductive system, the connective tissue and the skeletal muscles.

During development, cells known as myoblasts grow and replicate to become muscle fibres as they link together to form chains of myoblast cells. Skeletal muscle fibers have multiple nuclei in each fiber as a result of myoblast fusing together. The myoblast fuse together to become myotube but there are some that wouldn't become myotubes, rather the remain alone as satellite cells or muscle stem cells.

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Muscle fibers do not divide like other cells divide but satellite cells can divide and grow if the muscles are injured. As infants, you have about 600 muscles and these muscle fibers remain the same but bigger because of the satellite cells in a muscle cell growth known as hypertrophy. This same thing applies to people lifting weight as their muscle experience hypertrophy as a result of the activity. Also studies are looking into muscle cell hyperplasia but we are yet to get substantive results, so for now muscles grow as a result of hypertrophy.

At the age of thirty, we reach the peak of muscle mass growth but from then we lose about 1 to 2 percent of our muscle mass and at the age of 70, we would have had about 30% muscle loss compared to its peak and this muscle loss as a result of aging is referred to as Sarcopenia.

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As we grow old, a lot of things are happening at once, so it is difficult to state what is causing muscle loss. Some are caused by the nervous system as some of the nerves start to reorganize themselves. We start to lose fast twitch (type 2) muscle fibers and rely on slow twitch fiber and with this, we do not use more strength with muscles so it affects the muscle as they become inactive. With the inactivity, we start to lose muscle mitochondria.

As we age, the best way to combat muscle loss is through aging and exercise. Exercise is one of the most beneficial things to do as you grow older with its benefits showing even at old age. With exercise, the satellite cells are improved, continuous loss of muscle cells from nerve connection is prevented, and more mitochondria are made thereby preventing muscle loss related with aging.

https://www.popsci.com/build-muscle-faq-exercise-experts/
https://www.healthline.com/nutrition/sarcopenia
https://medlineplus.gov/ency/article/003188.htm
https://longevity.stanford.edu/lifestyle/2023/04/11
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2804956/
https://www.health.harvard.edu/exercise-and-fitness/age-and-muscle-loss