MSCI M131 Lecture 8(Unit 2)Outline of Past Lecture I. Joints and Cartilage a. Rheumatoid ArthritisII. Musculoskeletal Anatomy and PhysiologyOutline of Current lectureI. Muscle Disordersa. Muscular DystrophyCurrent LectureI. Muscular Dystrophya. Case study-i. Progression of muscle weakness that continued unabated; delayed muscle development – not enough strengthb. Pathophysiologyi. As muscle contracts, it rips itself apartii. Structure of the muscle is weakenediii. Progressive damage, further weakness1. Can’t make more muscle cells2. Where muscle is lost, there are fat deposits – change in composition of muscle, even more weakness and possibility of more damagec. Etiologyi. Loss of or dysfunctional dystrophin1. Protein that anchors actin strands to the wall of the myofibril, helps pull rest of muscular/ actin fibers 2. Without it, muscle wall doesn’t move, and when contracted, the fibers tear apartd. Signs and symptomsi. Muscle related1. Weaknessa. Proximal (close to core)These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.2. Contracturesa. Scar tissue in muscles, makes muscles freeze in shortenedpositionii. Skeletal1. Compensationsa. Knees bend back – use bones themselves to support weightb. See curvature because of stress2. Deformationsa. Spine adjusts to maintain upright postureiii. Other1. Lack of coordination, poor balance2. Postural changes (see chart provided)3. Composition changes (fat and scar tissue)e. Clinical importancei. The most common form (Duchenne’s MD) usually causes death by 25ii. Progressive muscle weakness can make simple tasks impossibleiii. Long term full-time care often necessary – cost and time draining, parents leave job to care for childiv. No cognitive problems – trapped in bodyf. Risk factorsi. Genetic inheritance1. dystrophin gene on X chromosome 2. Primary factor - accounts for 2/3 of casesii. Genetic damage1. Accounts for 1/3 of cases2. Can happen anytimeg. Diagnosisi. Genetic testing1. DNA blood testsii. Blood profile1. The presence of muscle enzymes shoes large-scale muscle damage (not conclusive – could be from strenuous exercise)2. Indicates breakdown of muscle iii. Muscle biopsy 1. Take part of muscle and view cross-section- look for shearing anddamageh. Treatmentsi. There is no cure right now, can only keep patients comfortable and functional as long as possible1. Most therapeutic attempts to maintain functiona. Stretching to avoid contracturesb. Bracing – shares load, prevents bones from taking all weightc. Speech therapy2. Gene therapy is starting to be attempted in humans i. Prognosisi. Varies significantly with type of MD and rate of progressionii. Duchenne’s MD – rarely live to see 30iii. Most with MD have shorter lifespans; however, those with mild cases (late onset) can live full lives with few