Skeletal Muscle : Types, 5 Symptoms and Treatment

• Skeletal muscle is a muscle tissue that is attached to the bones, and, also called voluntary muscles because they come under the control of the nervous system in the body

Skeletal Muscle is one of three types of muscle in the human body—the others being the visceral and cardiac muscles. The description, structure, characteristics, functions, and types of skeletal muscles are simply and thoroughly discussed in this lesson.

Skeletal muscle is a muscle tissue that is attached to the bones and is involved in the functioning of various parts of the body. These muscles are also called voluntary muscles because they come under the control of the nervous system in the body.

Understanding Skeletal Muscular Dystrophy

The structure of skeletal muscles is shown below:

This muscle is attached to the bones by an elastic tissue or collagen fiber called a tendon. These tendons are made of connective tissues. Muscle fibre bundles termed bundles make up skeletal muscles.

These vesicles are cylindrical in shape as shown in the figure. These muscle fibers are surrounded by blood vessels and several layers of other tissues surrounding it.

Each muscle fiber is lined by a plasma membrane called the sarcolemma reticulum. It surrounds a cytoplasm called sarcoplasm which contains endoplasmic reticulum.

Muscle fibers consist of myofibrils, which consist of two important proteins, namely actin and myosin. The fascia is surrounded by the perimysium and the endomysium is the connective tissue that surrounds the muscle fibers.

What are the Properties of Skeletal Muscle?, Identifying Types, Treatment Options

Skeletal muscles have the following properties:

• Extensibility: It is the ability of the muscles to stretch when stretched.
• Elasticity: It is the ability of a muscle to return to its original structure when released.
• Excitability: It is the ability of muscles to respond to stimuli.
• Contractility: It is the ability of a muscle to contract in response to a stimulus.

Types of Skeletal Muscle

There are two types of skeletal muscles called red and white muscles.

1. Red Muscles

Red muscles are due to a red pigment called myoglobin, which is present in high amounts in the human body. These muscles are small in diameter and contain large number of mitochondria. Myoglobin stores oxygen, which is used by the mitochondria for the synthesis of ATP. Red muscles contain a large number of blood capillaries.

2. White Muscles

Unlike red muscles, white muscles are larger in diameter and contain smaller amounts of myoglobin. Additionally, they have fewer mitochondria.

3. Smooth Muscles

Smooth muscle is a type of muscle tissue that is used by various systems to exert pressure on organs and vessels. It is an involuntary muscle, which does not show any transverse stripes even when examined under a microscope.
A smooth muscle is made up of cells that are narrow and spindle-shaped, with a single nucleus that is centrally located.

Smooth muscle cells are composed of filaments of myosin and actin that run through the cell and are supported by a framework of various proteins, with the filaments arranged in a stacked pattern across the cell.

It displays a ‘Ladder’ arrangement of fibrils-actin and myosin, which is different from the structure typically seen in cardiac and skeletal muscles.

Unlike striated muscles, smooth muscle tissue contracts slowly on its own. Most of the muscles in the digestive tract and internal organs are made up of smooth muscles.
Smooth muscles contract under the influence of stimuli, releasing ATP that can be used by myosin. This ATP released depends on the magnitude of the stimuli which enables smooth muscle to have a graded contraction in contrast to the ‘on-off’ contraction seen in skeletal muscle. Actin filaments run from one side of the cell to the other and are attached to the cell membrane and compact bodies.

4. Cardiac Muscle

Cardiac muscle, one of three types of muscle, is a muscle tissue found in the heart, in that it is performing and bringing about coordinated contractions that enable the heart to pump blood throughout the body through the circulatory system.

The heart muscle tissue performs the continuous pumping of the heart through involuntary movements. This is one of the distinguishing features of the heart muscle that differentiates it from the muscle tissue that is under one’s control. It is able to do this through specialized cells known as pacemaker cells that control the contraction of the heart.

The nervous system sends signals to specific cells, telling them to increase or decrease the heart rate. Pacemaker cells are attached to the cells of the heart muscle, which enables them to transmit signals that cause a wave of contraction in the heart muscle which in turn generates the heartbeat.

Cardiac muscles are made up of the following:

• Nucleus
• Gap Junctions
• Intercalated Disc
• Desmosomes

Functions of Skeletal Muscles

Following are the important functions of skeletal muscles:

1. Skeletal muscles are responsible for body movements such as typing, breathing, spreading arms, writing etc. Muscles contract which pull tendons on bones and cause movement.
2. The posture of the body is maintained by the skeletal muscles. The body’s upright posture is a result of the gluteal muscle. The sartorius muscles in the thighs are in charge of movement in the body.
3. Skeletal muscles protect the internal organs and tissues from any injury and also provide support to these delicate organs and tissues.
4. They also support the entry and exit points of the body. Sphincter muscles are present around the anus, mouth and urinary tract. These muscles contract which reduces the size of the opening and facilitates swallowing of food, defecation and urination.
5. Skeletal muscles also regulate body temperature. The body feels hot after heavy exercise. This is due to the contraction of skeletal muscles which convert energy into heat.

What is Muscle Dystrophy?

A category of disorders known as muscular dystrophy lead to gradual muscle loss and weakening. The faulty genes (mutations) that cause muscular dystrophy prevent the body from producing the proteins required to develop healthy muscles.

Muscular dystrophy comes in various forms. Most often in boys, the most prevalent type’s symptoms start in early childhood. Other types don’t show up until later in life. The disease muscular dystrophy has no known cure. However, medications and treatments can aid in the management of symptoms and stop the spread of the illness.

What are the Symptoms of Muscular Dystrophy?

Progression of muscle weakening is the main sign of muscular dystrophy. Depending on the kind of muscular dystrophy, particular signs and symptoms appear at various ages and in various muscle groups. Here below are all the possible symptoms depending on the type of muscular dystrophy:-

1. Duchenne Type Muscular Dystrophy

This is the most common form. Although girls can be carriers and mildly affected, it is more common in boys. The following signs and symptoms, which typically start in childhood:

1. Frequent falls
2. Difficulty rising from a sitting or lying down position
3. Trouble running and jumping
4. Wobbler
5. Walking on toes
6. Large muscles of the feet and calves
7. Muscle pain and stiffness
8. Learning Problems
9. Delayed Growth
10. Height Growth Problems

2. Becker Muscular Dystrophy

Though milder and progressing more slowly, it exhibits symptoms and signs that are comparable to those of Duchenne muscular dystrophy. Symptoms usually begin in adolescence but may not occur until the mid-20s or later.

3. Oculopharyngeal Muscular Dystrophy (OPMD).

Oculopharyngeal muscular dystrophy (OPMD) causes weakness in the muscles of your face, neck, and shoulders. Other symptoms include:

1. Fluttering Eyelids
2. Eyesight problem
3. Trouble swallowing
4. Voice Change
5. Heart problems
6. Difficulty in walking
   OPMD is one of the rarer types of muscular dystrophy, affecting less than 1 in 100,000 people in the United States. In their 40s or 50s, people typically start to exhibit symptoms.

4. Distal Muscular Dystrophy

Distal muscular dystrophy is also called distal myopathy. It is a group of more than six diseases that affect the muscles distal to the shoulders and hips, specifically:

Forearms, Hands, Calves, Feet.

5. Other Types of Muscular Dystrophy

Some forms of muscular dystrophy are distinguished by a particular trait or by the location of the onset of the symptoms in the body. Examples include the following:-

5.1) Myotonic

It is characterized by the inability of the muscles to relax after contraction. Myotonia, which is the inability of your muscles to relax after contracting, is brought on by this type of muscular dystrophy. Steinert’s illness and dystrophia myotonica are other names for myotonic dystrophy. People with other types of muscular dystrophy do not experience myotonia, but it is a symptom of other muscle diseases. Symptoms include:

1. Facial muscles
2. Central Nervous System (CNS)
3. Adrenal gland
4. Heart
5. Thyroid
6. eyes
7. Gastrointestinal tract

Symptoms first appear in the face and neck, they include:

1. Dropping of muscles in the face, creating a thin, drawn-out look
2. Difficulty lifting the neck due to weak neck muscles
3. Difficulty swallowing
4. Drooping eyelids, or ptosis
5. Early baldness in the frontal area of the scalp
6. Poor vision including cataracts
7. Weight Loss
8. Increased sweating

Additionally, this type of dystrophy may result in testicular atrophy and impotence. In others, it can cause irregular periods and infertility.

Myotonic dystrophy is most likely to be diagnosed in adults in their 20s. The severity of symptoms can vary greatly. While some people only have minor symptoms, others may have heart- and lung-related symptoms that could be fatal. With the condition, many people live long lives.

5.2) Facioscapulohumeral (FSHD)

Muscle weakness usually begins in the face, hips, and shoulders. When the arms are raised, the shoulder blades can stick out like wings. Onset is usually in adolescence but can begin in childhood or as early as age 50.

5.3) Congenital

This type affects boys and girls and is evident at birth or before age 2. While some forms progress gradually and only slightly impair people, others advance quickly and seriously harm people.

Congenital muscular dystrophy is most often apparent between birth and 2 years of age. This is when parents begin to notice that their child’s motor function and muscle control are not developing as they should. Its symptoms vary and may include:-

1. Muscle weakness
2. Poor Motor Control
3. Inability to sit or stand without support
4. Scoliosis
5. Foot deformities
6. Trouble swallowing
7. Respiratory problems
8. Eyesight problem
9. Speech Problems
10. Learning Gaps

Symptoms range from mild to severe. The lifespan of a person with this type of muscular dystrophy also varies depending on their symptoms. Congenital muscular dystrophy can cause infant death syndrome or adult life.

5.4) Limb-girdle

The muscles of the hip and shoulder are usually the first to be affected. People with this type of muscular dystrophy may have difficulty lifting the front part of the leg and may therefore trip frequently. Onset usually begins in childhood or adolescence.

What is the Cause of Muscular Dystrophy?

Differences in genes cause muscular dystrophy. Thousands of genes are responsible for the proteins that determine the integrity of muscles. People carry genes on 23 pairs of chromosomes, with half of each pair inherited from the biological parent. One of these pairs of chromosomes is linked to sex.

This means that depending on your sex or the sex of your parents, the features or conditions you inherit as a result of those genes may vary. The other 22 pairs are not sex-linked and are also known as autosomal chromosomes.

Changes in a single gene can result in a lack of dystrophin, an important protein. The body may not make enough dystrophin, may not make it correctly, or may not make it at all. There are four ways that people can get muscular dystrophy. Muscular dystrophy is typically caused by inherited gene variations, however they can also result from a spontaneous mutation.

Also read: Crohn’s Disease: Unmasking Symptoms, Causes, Diagnosis, & 7 Potent Treatments

What are the Risk Factors for Muscular Dystrophy?

Muscular dystrophy is a genetic condition. Being a carrier or getting muscular dystrophy is more likely if your family has a history of the disease. Since DMD and BMD are linked to the X chromosome, children who are assigned male are more likely to experience them.

However, even though children assigned to children receive one X chromosome from each parent and should have sufficient dystrophin production, they may still experience symptoms of DMD or BMD, such as muscle spasms, weakness. and heart problems.

What are the Complications of Muscular Dystrophy?

Progressive Muscular weakening has the following side effects:

1. Difficulty Walking

Some muscular dystrophies patients eventually use a wheelchair.

2. Problems Utilising your Arms

When the hands and shoulders’ muscles are weakened, daily activities may become more challenging.

3. Shortening of the muscles or tendons around the joints (Contractures):

Contractures can further limit mobility.

4. Shortness of Breath

Progressive weakness may affect the muscles involved in breathing. People with muscular dystrophy may eventually need to use a breathing assistance device (ventilator), initially at night but possibly during the day as well.

5. Curved Pine (Pcoliosis)

Weak muscles may be unable to keep the spine straight.

6. Heart Problems

Muscular dystrophy can reduce the functionality of the heart muscles.

7. Swallowing Problems

If the muscles associated with swallowing are affected, nutritional problems and aspiration pneumonia may develop. Feeding tubes may be an option.

Does Pregnancy cause Problems with Muscular Dystrophy?

Given the difficulties and probable complications associated with pregnancy, people with muscular dystrophy may need to rethink their conception of the topic. Muscle weakness in the muscles of the legs, hips, and abdomen can make it difficult to push during labor, increasing the likelihood of cesarean delivery or other interventions.

Pregnancy loss can result from the generalised muscle weakness that might be caused by myotonic dystrophy. Pregnancy can also cause people with myotonic dystrophy to experience a rapid onset and worsening of their symptoms.

How is Muscular Dystrophy Diagnosed?

A medical history and physical examination will probably be the first steps taken by your doctor. After that, your doctor may recommend some of the following tests:

1. Enzyme Tests

Damaged muscles release enzymes such as creatine kinase (CK) into your blood. In a person who has not suffered a traumatic injury, a high blood level of CK suggests muscle disease.

2. Genetic Testing

Blood samples can be tested for mutations in certain genes that cause the type of muscular dystrophy.

3. Muscle Biopsy

A small piece of muscle can be removed by making an incision or with a hollow needle. Analysis of tissue samples can differentiate muscular dystrophy from other muscle diseases.

4. Heart-Monitoring Tests (Electrocardiography and Echocardiogram)

These tests are used to check heart function, especially in people with myotonic muscular dystrophy.

5. Lung-Monitoring Tests

These tests are used to check the function of the lungs.

6. Electromyography

An electrode needle is inserted into the muscle for the test. As you unwind and gradually contract your muscles, the electrical activity is measured. Changes in the pattern of electrical activity can confirm muscle disease.

What is the Treatment for Muscular Dystrophy?

Muscular dystrophy does not presently have a cure, however medicines can help you manage your symptoms and halt the disease’s progression. Treatments depend on your symptoms and the type of muscular dystrophy you have.

A. MEDICATIONS

For some DMD patients, new medicines have been approved by the Food and Drug Administration (FDA). Many of these treatments use a new process called “exon skipping,” where the faulty section (exon) of the dystrophin gene is patched so that the body can produce the protein.

These new drugs include:

1.Eteplirsen (Exondys 51) This weekly injection is for people with a specific mutation of the dystrophin gene that is responsible for skipping 51.

2.Golodirsen (Vyondys 53) This weekly injection is for people who have dystrophin gene difference, who can get away with skipping 53.

3.Viltolarsen (Viltepso) Viltolarsen (Viltepso) It is also a weekly injection for people with dystrophin gene difference which is skippable by 53 skipping.

4. Deflazacort (Emflaza) Deflazacort (Emflaza) It is a corticosteroid which is available in tablet and oral suspension form. It is approved for people ages 5 and older with DMD.

B. Muscle Therapy

Forms of muscle therapy have proven effective. Working with a professional is one of these methods for enhancing physical performance. Types of therapy include the following:-

1. Physical Therapy, including physical activity and stretching, to keep muscles strong and flexible
2. Respiratory Therapy, to prevent or delay breathing problems
3. Speech Therapy, using specific techniques such as slow speech, pauses between breaths, and special equipment to preserve muscle strength.

Disclaimer : The article’s sole purpose is to wake you up for your health and to provide you the best collective and verified information. We do not recommend for any kind of medicine or treatment. You should only seek to your Doctor or Medical Counselor Because there is no one better than him.