Introduction
The studied muscles on which this report is based make part of the skeletal muscles group; they are connected to the bones by “tough cords of tissue” (NIH 2012) which are called the tendons and, as they contract, they pull these same tendons and the bones attached, causing movement. These movements are of voluntary nature, one being capable of controlling them as one wish to. The action of these muscles can be described as being initiated on the body’s standard or anatomical position and used for specific movements that one requires for a given activity. Some of these actions are applied to “several regions of the body” (Bruenger 1994), or to one region or single joint. The movements these muscles cause can be of flexion, extension, abduction, adduction, lateral or medial rotation, circumduction; more specifically acting on the scapula area, of elevation, depression, protraction, retraction, rotation; if applied on the hand, like some of the studied muscles on this report, can cause movements of abduction, adduction, opposition, pronation and supination.
These muscles, when in action, make it possible for one to move himself around in every single daily activity: standing up straight, walking, running, picking up objects, bending, sitting, playing an instrument, a sport, perform one’s basic necessities like chewing, swallowing, inhaling, exhaling, excreting urine and faeces,etc. Knowing their anatomical features, such as origin, insertion and action produced by their contraction or relaxation, one can easily acquire valuable information about the human body’s anatomical and physiological functions and assess the importance that these muscles have for a person to conduct a normal life, with quality and health.
Associated with these muscles are a large number or pathologies; some are inherited, while others are caused by straining, tearing, dislocation etc., being called injuries. An example of each, inherited and injury, are mitochondrial myophaties and rotator cuff injuries, respectively.
Mitochondrial myopathies make part of a “group of neuromuscular diseases” (NINDS 2011), in which there is an actual damage in the mitochondria; being a cell structure responsible for energy production that will then be used by the cells for their every function and having brain and muscle cells high requirements on this same energy, these are the most damaged ones when these kind of dysfunctions on the mitochondria occur. These pathologies include Kearns-Sayre Syndrome, “mitochondrial encephalomyopathy with lactic acidosis” (NINDS 2011), “myoclonus epilepsy with ragged-red fibers” (NINDS 2011) and episodes that resemble strokes.
Patients with this type of disease find themselves impaired in their everyday life, because mitochondrial myopathies cause a very marked weakness sensation; on the eyes and eyelids, for example, they cause difficulties in the movements of the eyes and the opening of the eyelids, which impair sight. A common consequence is “the gradual paralysis of eye movements” (Kelly 2011, p 5) – designated as Progressive External Ophthalmoplegia (PEO). There can be also great difficulty in swallowing, which will impair the patient’s eating ability and his diet. Weakness on neck and mouth can impair the speech. When talking about moving oneself around, weakness on the limbs may cause the necessity to use braces or even a wheelchair, which will further limit the patient. Physical activities, also, are very tiring for these patients, who often feel exertional fatigue – exhaustion by having physical activity. This impairment can be as simple as not being able to play a sport, or as impairing and complex as not being able to lift a light object. There are usually associated strong cramps and/or “injury induced pain” (Kelly 2011, p 5); this last one is caused by “acute muscle breakdown” (Kelly 2011, p 5) – rhabdomyolisis – which leads to having a leak of myoglobin into the urine from the muscles – myoglobinuria. Thus, as one can clearly see, patients with these type of pathologies related to mitochondria can be severely impaired in almost every function of their life routine.
Addressing now the rotator cuff injury, this is located in the shoulder area. It can include tendinitis, bursitis and even tearing of the muscles and tendons. This is a type of injury that, if severe, can cause serious pain on the shoulder are. This pain can be from the injury itself and/or associate with the pain caused by inflammation of the site of injury. The pain by itself is enough to limit the arm function, because patients tend to not be able to use the arm with injured shoulder because of it; but it is not just the pain.
Muscles and tendons being compromised, their function as mobilizing muscles is also impaired and the patient is not able to move that arm normally, nor have enough strength on it to lift it, with or without picking up objects. Thus, an individual that has this kind of injury can have an impaired motion and use of a limb, which limits actions like driving, picking up objects, taking care of hygiene, etc. This is, indeed, an impairing condition that limits everyday life.
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Figures 1-9 – Labeled muscles: 1. Trapezius; 2. Deltoid; 3. Triceps brachii; 4. Latissimus dorsi; 5. Pectoralis major; 6. Pectoralis minor; 7. Rectus abdominis; 8. Serratus ventralis; 9. Brachiocephalic; 10. Brachioradialis; 11. Masseter; 12. Extensor carpi radialis; 13. Extensor digitorum communis; 14. Extensor digitorum lateralis; 15. Extensor carpi ulnaris.
Discussion
Pigs and humans share many similarities in their anatomical muscular structure. That is why the fetal pigs are often used as models for study and comprehension of the human muscles’ anatomy. Even so, however, they also have differences, which relate to the fact that humans are bipeds and pigs are quadrupeds. Two similar muscles that humans and pigs have are the pectoralis major and the rectus abdominis, because pigs and humans have the same pulmonary structure and trunk bone structure; thus, these muscles, in both beings have the same insertions, origins and functions of assisting the respiratory movements. Both humans and pigs are omnivorous, which means they also have similar teeth and their consequent organization for their similar diet; thus, their masseter muscles are also similar, having the same origins, insertions and function in mastication, which, having both an omnivorous diet, means they both have similar structure also.
About the differences pigs and humans present in their muscular structure, this is related, as stated above, with the fact that the locomotion systems are different: pigs are quadrupeds and humans are bipeds. This way, their limbs’ muscular structure is different and adapted to this fact: the chest muscles “that attach to the shoulder girdle” (Miller 1998) have slight differences in the pigs, to be better adapted to a quadruped locomotion. Also, being bipeds, the humans need extra strength on their lower limbs’ muscles to be able to support the body’s weight; this causes for “some differences in the gluteal muscles” (Miller 1998), compared to the ones in pigs, to be able to provide more support and balance in a biped locomotion.
Returning to the muscular health conditions chosen as examples for inherited ones and ones resulting from injury, the mitochondrial myopathies and the rotator cuff injuries, these have more features to be discussed.
Mitochondrial myopathies are caused by mutations in the genetic information that is kept within the genes and, consequently, in the synthesized proteins. So, all the etiologies relate exactly to this same fact: that there was a mutation in genes that coded for proteins that are responsible for the mitochondrial structure and function to be normal.
With such structures and functions of the mitochondria being impaired, there a consequential impairment on the energy (ATP) production, which means that cells that require greater energy levels are the most affected ones – muscle and neural cells. Thus, in mitochondrial myopathies, there are great damages to the whole functioning of the muscle cells and, consequently, great impairments to the muscles’ function itself.
Someone that has a mitochondrial myopathy feels muscle weakness, which can impair strength in only some types of movements, or be more severe and impair the simplest tasks; the patient also has exercise intolerance, easily developing a sensation of exhaustion. Furthermore, other symptoms and conditions are associated with this abnormal mitochondrial function that impairs the correct energy supply for the cells: “heart failure or rhythm disturbances, dementia, movement disorders, stroke-like episodes, deafness, blindness” (NINDS 2011), ptosis, eye movement limitation, vomiting, seizures, cramping, nausea, headache and difficulties in breathing.
As for treatment options for this condition, these are still limited, even with the most recent research and advance in the molecular understanding field. The patients seem to have benefits from exercise training, due to the help with “improving exercise tolerance and enhancing oxidative capacity” (NINDS 2011). Also, there seems to be a coenzyme Q10 deficiency associated with these mitochondrial myopathies; therefore, taking a good supplement of coenzyme Q10 also is an option for treatment plans’ incorporation. There is also recent research done on the “activation of the peroxisome proliferator-activated receptor/peroxisome proliferator-activated receptor-gamma coactivator-1alpha pathway” (NINDS 2011), in which mitochondrial biogenesis induction has been observed, delaying the myopathic onset of these conditions. It is also suggested for the patients to undergo a ketogenic diet, for having also been observed mitochondrial biogenesis with it. The prognosis of someone with this kind of condition is not, however, as bad as the condition itself seems to be, because the treatment of the symptoms and possible complications can be done, improving the patients’ quality of life. Fortunately, “these treatable symptoms are often the most life-threatening complications of mitochondrial disease.” (Kelly 2011, p 7)
Now addressing the rotator cuff injuries, their etiology is related to a “prolonged period of repetitive injury” (Hospital for Special Surgery) and it is commonly associated with sports like baseball or tennis that require many repeated overhead movements. They can also occur because of aging and the muscle being weaker and more prone to tear, or of a sudden force applied on the shoulder area, like in a fall with the body weight over the arm.
When this kind of injury occurs, there is a very big inflammation reaction that sets on the shoulder area, which by itself can be very painful; sometimes, it is associated with the tear of the muscle, which is even a worse diagnose. Either way, these injuries cause great damage to the shoulder muscles, limiting movement and ability to use that arm, even in little movements and daily situations. It may also cause “clicking, cracking, or popping sounds when you move your shoulder” (Matsen III 2013)
If the injury is acute and resulted in the tearing of the muscle, surgical repair should be performed within six weeks, so that it won’t suffer atrophy (both muscle and tendon); this surgery can be done with arthroscopy, or, in more severe cases, with large incisions. Exercises for rehabilitation are also used in rotator cuff injuries, when they are not so severe. Treatment also associates anti-inflammatory medication, or even steroids (these being in injected form), followed by physical therapy.
It is expected to have a “durable rotator cuff repair” (Matsen III 2013) if “there is a sufficient amount of good quality tendon for the repair” (Matsen III 2013). But it is expected, with time, that these rotator cuff injuries result in tissue weakness and retraction, exposing the humerus head. These injuries also leave a sensation that the shoulder “remains stiff and painful” (Matsen III 2013), which can be relieved with surgical approach.
In conclusion, for the conditions described, some care measures can be taken. In what the mitochondrial myopathies are related, being an inherited condition, previous genetic screening of the parents can be done before having a child, if there is family history of this condition, to know what are the chances of the child having the gene mutation that triggers it. Also, when the condition is installed, the earliest it is diagnosed the better, to soon start with medication and supplementation that may stabilize its course. In what is concerned with rotator cuff injuries, the athletes of repetitive upper movements’ sports should have a close follow-up with an experienced physician and physical therapist in order to, with the slightest symptoms, this can be prematurely treated to avoid the tearing situations. These types of movements and the probability of falling should be avoided by the elder, who are more prone, by more weakness of their muscles, to having tearing of the shoulder structures and a worse prognosis after treating it.
References
- NIH: National Institute on Arthritis and Musculoskeletal and Skin Disease (2013). Rotator Cuff Injuries. Retrieved from http://www.nlm.nih.gov/medlineplus/rotatorcuffinjuries.html
- Bruenger, John, Fischer, Ted, Chapman, Chris, Tucker, Jane, VerHelst, Amy, Wysor, Wanda J. (1994). Hypermuscle: Muscles in Action. Retrieved from http://www.med.umich.edu/lrc/hypermuscle/hyper.html
- NINDS: National Institute of Neurological Disorders and Stroke (2011). NINDS Mitochondrial Myopathies Information Page. Retrieved from http://www.ninds.nih.gov/disorders/mitochondrial_myopathy/mitochondrial_myopathy.htm
- Kelly, Richard (2011). Facts About Mitochondrial Myopathies. Retrieved from http://mda.org/sites/default/files/publications/Facts_MITO_P-216.pdf
- Miller, James S. (1998). Fetal Pig Dissection Guide: Human/Pig Comparisons. Retrieved from http://www.goshen.edu/bio/pigbook/humanpigcomparison.html
- Hospital for Special Surgery (n.d). Rotator Cuff Injuries & Conditions. Retrieved from http://www.hss.edu/condition-list_rotator-cuff-injuries.asp
- Matsen III,Frederick A., Warme, Winston J. (2013). Rotator Cuff Tear: When to Repair and When to Smooth and Move the Shoulder. Retrieved from http://www.orthop.washington.edu/?q=patient-care/articles/shoulder/rotator-cuff-tear-when-to-repair-and-when-to-smooth-and-move-the-shou
