Skeletal muscles make up approximately 40% of a human’s total body weight. Skeletal muscles are attached to the skeleton by tendons which are made of collagen. Muscles function together as a unit. A skeletal muscle is a collection of muscle cells or muscle fibres. [4]
Hundreds if not thousands of muscle fibres bundled together and then wrapped in a connective tissue covering make up an individual skeletal muscle. Each muscle is then surrounded by the epimysium which is a connective tissue sheath. Outside the epimysium, a connective tissue called Fascia surrounds and separates the muscles. Sections of the epimysium project inwards which divide the muscle into compartments. Contained within each compartment is a bundle of muscle fibres. A bundle
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This disease is a usually a result of a missense mutation in the carboxy-terminal part of the Desmin rod domain within the 2B subdomain of the Desmin gene.
The mutation in the gene causes the protein to become ineffective therefore the protein can no longer carry out its function. These proteins then clump together to form aggregates however the aggregates are not removed from the cells this suggests a problem with the ubiquitin-proteosome system. Proteosomes are affected by aggregates as they inactivate and deplete the actual breakdown of proteins. [5]
The mutated proteins clump together and form aggregates, the aggregates eventually cause mitochondrial dysfunction. Mitochondria are cell compartments, which provide a constant supply of energy to the cell. As the power supply, the positioning of mitochondria is essential for the smooth running of functions within the muscle cell. As the mitochondria are essential for the high yield of ATP required for muscle contraction by synthesising it at the inter-mitochondrial membrane as part of the oxidation phosphorylation mechanism as part of cellular energy transfer.[6] During Oxidation phosphorylation, the hydrogen atoms which derived from glycolysis and the Krebs cycle and the breakdown of fatty acids are believed to the electron transport chain. This regenerates coenzymes NAD+ and FAD by transferring the hydrogen to molecular oxygen
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This causes the Z-disks to come closer together. Therefore if the Z-disks between the sarcomeres broke down then the sarcomeres are no longer in line with one another. Also with the breakdown of the Z-disks the thin filaments of actin would not be held together for the myosin head to bind and drag the actin filament. This results in the disorganisation of the muscle fibres therefore that section of the filament would not be able to contract or there would be very little contraction. This would lead to muscle fatigue as the other filaments within the muscle would then take the strain and stress. It would also lead to muscle weakness eventually due to the Desmin not being repaired or replaced and more cells being replaced with the mutated gene for Desmin due to mitosis as with cell replication the mutation become permanent.
...st the sacrolemma will depolarized, thus activation potentials along the T-tubules. This signal will transmit from along the T-tubules to sarcroplasmic reticulum's terminal sacs. Next, sarcoplasmic reticulum will release the calcium into the sarcroplasm leading to the next second event called contraction. The released calcium ions will now bind to troponin. This will cause the inhibition of actin and mysoin interaction to be released. The crossbridge of myosin filaments that are attached to the actin filaments, thus causing tension to be exerted and the muscles will shorten by sliding filament mechanism. The last event is called Relaxation. After the sliding of the filament mechanism, the calcium will be slowly pumped back into the scaroplasmic reticulum. The crossbridges will detach from the filaments. The inhibition of the actin and myosin will go back to normal.
Within skeletal muscle there are extremely small structures that form the muscle and allow contractions and movement to occur (epimysium, perimysium, endomysium, fascicles, fiber, sarcomere, sarcoplasmic reticulum and t tubules). These structures all play a role in protecting, connecting and transporting substances throughout the muscle fibers. They are also the main contributors to movement.
Physiological Basis of disease: DMD is the commonest and most serious form of the dystrophies. The gene responsible for dystrophin which, when absent, causes DMD. Amount of dystrophin correlates with the severity of the disease (i.e., the less dystrophin present, the more severe the phenotype). Since the gene is on the X chromosome, it primarily affects males, and females who are carriers have milder symptoms ( www.nlm.nih.gov/medlineplus/ency/article/000705.htm).
Emery-Dreifuss muscular dystrophy is a rare form of muscular dystrophy characterized by early onset contractures of the elbows, achilles tendons and post-cervical muscles with progressive muscle wasting and weakness It is also associated with heart complications like cardiomyopathy and arrhythmia which in both cases can lead to death. Cardiomyopathy is a heart disease which affects the muscles of the heart. In cardiomyopathy is muscles get rigid, enlarged or thick. They also sometimes changed by scar tissues. On the other hand arrhythmia is a disorder with the rhythm or rate of heartbeat. The heart can beat fast, which is called tachycardia or it could be beating too slow, which is called bradycardia. Emery-Dreifuss muscular dystrophy is characterized by early onset of contractures and humeroperoneal distribution. Humeroperoneal refers to effects on the humerus and fibula. The genes known to be responsible for EDMD encode proteins associated with the nuclear envelope: the emerin and the lamins A and C.
Spinal Muscular Atrophy, also known as “SMA” is a genetic and also a motor neuron disease that affects the area of the nervous system that controls your voluntary muscle movements such as walking, crawling, and swallowing. When someone acquires this condition their muscles start to shrink as a cause to the muscles not receiving signals from the nerve cells in the spine that control function. Spinal Muscular Atrophy is a rare but serious condition.
James’s biopsy of his right gastrocnemius muscle would have shown a degeneration of the muscle or skeletal fibers due to the lack of dystrophyn. Another microscopic change that would be noticed is the accumulation of white blood cells. White blood cells have a very specific function which is to clear the damaged muscle fibers from the debris. Clearly, due to some of the muscle fibers being damaged other healthy fibers that have not been damaged appear denser. By having damaged muscle fibers, all the work rest upon the healthy fibers making them contract to the fullest due to the fact that the myosin and acting would have to overlap even more to make the muscle work.
The skeletal system assists the muscular system to provide movement for the body. Certain muscles that are attached to bones contract and pull on the bones resulting in movement.
Muscular Dystrophy is a genetic disorder in which your muscles drastically weaken over time. Muscles are replaced with “connective tissue,” which is more of a fatty tissue than a muscular one. The connective tissue is the tissue that is commonly found in scars, and that same tissue is incapable of movement. Although Muscular Dystrophy affects muscles in general, other types affect certain groups of muscles, and happen at different periods throughout a lifetime. For example one of the most common types, Duchenne Muscular Dystrophy, targets muscles in the upper thigh and pelvis. The disease is displayed throughout early childhood, usually between ages four and seven. This genetic disorder occurs only in boys. People have difficulty sitting up or standing and lose their ability to walk in their early teens. Sadly most people die by the age of twenty. A second common type, Becker’s Muscular Dystrophy affects the same muscles as Duchenne, but first appears in teenage years. Most people with Becker’s only live into their forties (Fallon 1824-1825).
SMA is a genetic disease. It is caused by a missing or mutated gene, the survival motor neuron gene 1 (SMN1). Without the mutation, the gene produces protein, survival motor neuron (SMN) protein. People with this mutated gene have significantly lower amounts of this protein, which in turn causes severe motor neuron problems. “Motor neurons are nerve cells in the spinal cord which send out never fibers to muscles throughout the body.” SMN is a critical protein to motor neuron survival and health. Without this protein nerve cells may shrink and eventually die, resulting in muscle weakness. As children with SMA grow it becomes difficult for their already weak muscles to perform daily activities. As a result their muscles continue to get weak, their bones and spine may continue to change resulting in breathing problems and further loss of function. SMA affects the motor neurons so the brain is never affected (Understanding Spinal Muscular Atrophy). This disease is not as rare as one would think about one in 40 people unknowingly carry this disease (Spinal Muscular Atrophy).
When observing both cell types under a microscope several differences are obvious. Firstly, skeletal muscles are larger than smooth muscle cells (one muscle cell can be up to 100µm in length). They are also multinucleated whilst smooth muscle cells are uninucleate (Alberts et al, 2002: 961). Additionally, skeletal muscle cells appear to be striated, whereas smooth muscle cells do not show this banding pattern; but are instead smooth and tapered. The absence of this patterning in smooth muscle cells suggests that they consist of a less organised collection of contractile fibres (Silverthorn, 2007: 397). This banding pattern in skeletal muscles is known as the sarcomere.
The three functions of the skeletal system are to support, to allow movement, and to protect. The skeleton is the framework of the body and also cradles its soft organs, with it the body would be just a jelly mass it wouldn’t have no definite shape and would just collapse. It supports the softer tissues and provides points of attachment for more skeletal muscles to hold all of the parts of the body upright. For example, the bones of the legs as pillars to support the body trunk we stand up. It also supports the body against the pull of gravity. The skeletal allows movement. The skeletal muscle attached to the bones by tendons and uses the bones as a simple mechanical lever system to move the body and its parts. All together with the muscles
Duchenne's muscular dystrophy, also known as psuedohypertrophic muscular dystrophy, is a typical sex-linked disorder in which the muscles degenerate throughout a person's life. It literally means "faulty nutrition of the muscles. " Muscular Dystrophy has no cure, and this particular type of muscular dystrophy affects only males. One in 3,500 baby boys are born with this disorder and while survival is rare beyond the early 30s, death is usually caused by a respiratory disease.
The mitochondria is an organelle which is generally an oval shape and is found inside the cytoplasm and is again apart of the eukaryotic cells. The main function of the mitochondria is to complete cellular respiration; in simple terms it acts like a digestive system to break down essential nutrients and to convert it into energy. This energy is usually found to in ATP which is a rich molecule taken from the energy stored in food. Furthermore, mitochondria stores calcium for signalling activities; such as heat, growth and death. They have two unique membranes and mitochondria isn’t found in human cells like the red blood cells yet liver and muscle cells are filled entirely with mitochondria.
... urea cycle. So if mitochondria do not function properly, not only energy production but also cell-specific products needed for normal cell functioning will also be affected [Hardin et al. 2012]. There are three more important aspects of mitochondrial which are: (i) energy production, (ii) generation of reactive oxygen species (ROS), and (iii) regulation of programmed cell death, or apoptosis [Wallace, D. C. 1999].
Support is a very important fuction as without the skeleton the body would have no means of staying upright as almost all of the body tissues are soft this helps gives the body structure. The Skeleton plays an important role in the protection of the organs for example the skull protects the brain and the ribcage protect the lungs.The skeleton assists in the movement of the body as the ligaments in the body attach bone to bone and the tendons attach muscle to bone. To create movement the muscular system and the skeletal system work together creating the musculoskeletal. The skeleton can begin to move once the muscles contract. The fifth function of the skeleton is the formation of joints, these are essential to create movement within the body. Muscle attachment allows the bones to move. This is done by the muscles attaching to the bones by tendons. Minerals such as calcium salts and phosphorus are stored in the bones. The final function of the skeletal system is the formation of blood cells; most of the blood cells for the body are produced by red bone