Muscle comes from “Musculus”, a Latin word for little mouse. The shape and contraction of specific muscles resemble a moving mouse, which justifies the name of this body tissue. Though muscle’s primary function is to facilitate the movement of bones, it also plays a crucial role in heart functioning and is present in the lining of hollow organs like the intestine. 

Muscle movement can be both voluntary and involuntary, depending on the organs where they are present. Keep reading to learn about muscle structure, function, and disorders to get a detailed insight into your body’s muscular system.

A Brief Overview of the Muscular System 

Following is an overview of the role of muscles in the human body:

• The human muscular system is made of 600+ muscles, constituting 40% to 50% of the body weight. 
• This soft tissue, consisting of myosin and actin protein filaments, is present in both humans and animals. 
• Myosin and actin slide each other in the muscle cell, producing contractions to change the shape and size of the muscles. 
• Every organ in the body, from the heart to blood vessels, functions due to the contraction of muscles. 
• In the human body, muscles produce force and motion to circulate blood, change and maintain body postures, locomotion, etc. 
• Muscles are found attached to a body’s blood vessels, bones, and other internal organs. 
• In the human body, muscles are composed of elastic tissue, which helps in the contraction and expansion of muscles. 
• Their functioning involves the transfer of substances throughout the body. 
• The energy for muscle functioning is released from the oxidation of carbohydrates and fats and from ATP (Adenosine Triphosphate).

Different Types of Muscles in the Human Body

Based on the function and structure of muscles, they are divided into the following three types:

1. Cardiac Muscles

Cardiac muscles are only present in the middle layer of your heart. Also known as myocardium, these muscles enable blood to pump through the cardiovascular system by squeezing and relaxing. These are involuntary muscles and do not require any action from the individual for movement.

2. Skeletal Muscles

As the name suggests, these muscles are associated with bones, ligaments, and tendons, forming a part of the musculoskeletal system. Skeletal muscles are attached to all the bones of your body through tendons, supporting the body’s weight and movement. 

These voluntary muscles move when a person thinks about moving a specific part of their body. Some fast-twitch skeletal muscles contract quickly, using short bursts of energy. However, other muscles, like those in the back of your body, move slowly, helping with body posture.

3. Smooth Muscles

These muscles are found inside the lining of organs like the liver, pancreas, and intestine. They are involuntary muscles helping in activities like lung expansion while breathing, removal of waste through the intestine, etc. Smooth muscles play crucial roles in your respiratory, digestive, urinary, and reproductive systems.

Understanding the Functions of the Muscular System

Body muscles primarily perform two types of functioning: voluntary and involuntary. When muscle movement is controlled by you, it is voluntary, and when it moves automatically without your intervention, it is involuntary. However, muscles of the body also perform the following functions:

• Posture

Skeletal muscles maintain your body posture. Strong and flexible muscles enable good body posture, while tight, stiff, or weak muscles lead to poor body posture. This can lead to body misalignment and joint and muscle pains in your neck, back, shoulders, etc.

• Mobility

The primary function of the muscular system is to facilitate body movement. Contraction of muscles allows fine and gross movements like writing, speaking, and changes in facial expression, as well as walking, swimming, running, etc. 

Fine movements are mainly performed by smaller skeletal muscles. The voluntary muscle movements in your body are primarily performed consciously, apart from the reflexive ones.

• Stability

Muscle tendons are present in the shoulder and knee joints to enhance the joint stability. Additionally, core muscles in the pelvis, back, and abdomen also stabilise your body and help in activities like weightlifting. 

• Circulation

Your heart is also a muscle that enables blood circulation throughout the body without your conscious control. The heart muscles or cardiac muscles automatically contract due to electrical signal stimulation. Other than cardiac muscles, smooth muscles are present in the arteries and veins to facilitate blood circulation across your body. 

When the body gets dehydrated or loses blood, these muscles help maintain the blood pressure. Meanwhile, when your body needs more oxygen during intense exercise or similar activity, these smooth muscles increase blood flow by expanding themselves.

• Vision

Eye movement is controlled by six skeletal muscles located around your eye. Your eye can scan the surrounding area, view a stable image, and track the objects in motion due to the quick and precise functioning of these muscles. Any damage in the eye muscles can lead to vision imparity.

• Respiration

Muscles in the human body also help in respiration. Breathing involves the diaphragm, a dome-shaped muscle below the lungs. It contracts to expand the chest cavity, filling the lungs with air, and relaxes to expel air. Deeper breathing requires additional muscles from the abdomen, back, and neck.

• Digestion

The muscular system facilitates movement within the body, including digestion and urination. Smooth muscles in the gastrointestinal tract control digestion through peristalsis, a wave-like motion. 

This process moves food from the mouth through the oesophagus, stomach, and intestines. Muscles in the stomach mix food with acids and enzymes, while intestinal muscles help pass digested food out as stool.

• Childbirth

The muscle system also plays a role in the process of childbirth. The uterus is made of smooth muscles that contract and expand to push your child through the vagina. Smooth muscles are also present in the pelvic floor, guiding the baby to keep its head down through the birth canal.

• Urination

The urinary system relies on smooth and skeletal muscles in the bladder, kidneys, ureters, urethra, prostate, and reproductive organs. These muscles and nerves coordinate to store and release urine. Damage to nerve signals can lead to urinary issues like poor bladder control or retention.

• Regulates Body Temperature

The muscular system plays a crucial role in maintaining body temperature. About 85% of body heat comes from muscle contractions. When the temperature drops, skeletal muscles increase activity, causing shivering, and blood vessel muscles contract to retain heat. 

Conversely, relaxing smooth muscles in blood vessels increases blood flow, releasing excess heat through the skin to normalise body temperature.

• Protection of Organs

The internal organs in the front and back of your body are protected by the muscles in the torso. These organs are further protected by the ribs and bones of your spine. Body muscles absorb shock and reduce the friction in your bone joints, protecting bones and organs.

Exploring the Common Disorders of the Muscular System

Muscle disorders can be categorised as primary (direct muscle abnormalities) or secondary (caused by other conditions like endocrine issues). They may also be genetic or acquired and classified as neuromuscular or myopathies. Common disorders include:

• Myopathies: Conditions like polymyositis, dermatomyositis, and Duchenne muscular dystrophy cause muscle weakness or inflammation.
• Cramps: Painful, involuntary muscle contractions.
• Fibrositis: Inflammation of fibrous tissue in muscles, often affecting the back.
• Myasthenia Gravis: A neuromuscular disorder causing muscle weakness.
• Rhabdomyolysis: Muscle breakdown, releasing harmful substances.
• Cardiac Myopathy: Weakening of heart muscles.
• Sarcopenia: Age-related loss of muscle mass and strength.
• Amyotrophic Lateral Sclerosis (ALS): Progressive motor neuron disease leading to muscle atrophy.

FAQs About Muscle Anatomy

1. What is muscle anatomy?

Muscles consist of thousands of fibres that stretch and contract together, forming a network that moves organs and the body. The anatomy of your body muscles is much like a quilt covering and supporting the body.

2. What are the symptoms of muscle disorders?

Common symptoms of muscle injuries or disorders include pain, weakness, stiffness, spasms (cramps), swelling, bruising, and skin discolouration. These signs indicate damage or strain to the muscle fibres or surrounding tissues.

3. How do we diagnose muscle disorders?

Muscle disorders are diagnosed using tests like electromyography (EMG) to measure muscle electrical activity, blood tests for enzymes and antibodies, and muscle biopsies for microscopic analysis. Genetic testing is done for DNA mutations, MRI is done to detect abnormalities, and ultrasound is done for specific conditions like congenital muscular dystrophy. These methods help identify muscle damage, diseases, or genetic causes.

4. How are muscle diseases treated?

Muscular system diseases are incurable but manageable through treatments aimed at symptom relief, slowing progression, and improving the quality of life. Therapies include immunosuppressants for nerve-muscle conditions, corticosteroids for inflammation, and medications for spasms. Physical and occupational therapy help manage symptoms, while surgery may address muscle damage. 

5. What do muscle groups refer to?

Muscles are often grouped by location (e.g., chest, leg) or function (e.g., flexors, extensors). Healthcare providers classify them by tissue type, while fitness professionals focus on functional groups.

Conclusion

Muscles play a crucial role in the movement of your body organs and functions like blood circulation, heartbeat, excretion, urination, etc. A general knowledge of muscle structure and functioning is essential for everyone, but if you are a medical student, you must delve deeper. 

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