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108 Cards in this Set
- Front
- Back
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Mesoderm in the myotome regions of the somites |
The myoblast that form the skeletal muscles of the trunk are derived from? |
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Myogenic precursor cells of the limb buds |
Limb muscles develop from? |
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2 separate populations |
In mammals, how many populations of muscle precursor cells are there in the limb buds? |
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The somites |
These muscle precursor cells originate from? |
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Elongation of the NUCLEI & CELL BODIES of the mesenchymal cells as they differentiate into MYOBLASTS |
What is the first indication og myogenesis |
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Elongated, multinucleated, cylindrical structures called MYOTUBES |
Then these primordial muscle cells fuse to form? |
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The activation of genes and expression of the MyoD family of basicloophelixl oop transcription factors/MRF in the precursor cells |
At a molecular level, these events are preceded by? |
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The ongoing fusion of myoblasts & myotubes |
Muscle growth during development results from? |
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External laminae, w/c segregate them from the surrounding CT |
As myotubes differentiate, they become invested w/ ? |
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Perimysium and Epimysium layers |
Fibroblasts produces what, which serves as the fibrous sheath |
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Most Before birth, the remaining ones are formed by the end of the first year. |
When are muscles formed |
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An increase in the DIAMETER of the fibers due to the formation of new MYOFILAMENTS |
The increase in size of a muscle after the first year results from? |
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Amt of exercise |
Muscles' ultimate size depends on? |
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1. Contractility -most highly developed 2. Irritability/conductivity - developed but not as much as in nervous |
Vital properties of a Muscle tissue |
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Myocytes, muscle fibers |
Muscle cells aka? |
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Some single, some multiple. Elongated along the long axis of cell |
Nucleus of a muscle cell/fiber/myocyte |
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Sarcoplasm; strongly acidophilic Contains myoglobin which is O2 binding |
Cytoplasm of the muscle cell |
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Sarcolemma |
Cell membranr |
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Myofibrils |
Contractile element of the muscles |
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Sarcoplasmic reticulum |
A continuous system of membrane bound sarcotubules that extend throughout the sarcoplasm and form a close-meshed canalicular network around each myofibril |
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Dystrophy |
Various hereditary disorders causing progressive weakening of the muscles (defective nutrition) |
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Atrophy |
Wasting away or failure to grow of a bodily person |
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Hypertrophy |
Abnormal enlargement of an organ/part |
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Myositis |
Inflammation of a muscle |
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Myopathy |
Any abnormal condition or dss of the muscular tissues, commonly designates a disorder involving skeletal muscled |
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Duchenne muscular dystrophy |
Aka as pseudohypertrophic muscular dystrophy/ muscular dystrophy-duchenne type |
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Dmd |
Rapidly progressive muscles weakness w/c starts in the legs and pelvis & later affects the whole body. |
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Dmd |
Most common type of muscular dystrophy |
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X linked recessive |
Pattern of inheritance for dmd |
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3-5 years |
Age of onset for DMD |
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2/3, remainder represents new mutations |
In dmd, approx how much cases are familial |
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Carriers; they are asymptomatic but often have elevated serum creatine kinase and have minimal histologic abn on biopsy |
In the affected families, females are usually? |
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Dilated cardiomyopathy |
Female carriers are at risk of developing? |
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Xp21 (short arm of chromosome X) |
What gene is affected in dmd |
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Encodes/regulates the production of dystrophin, a 427-kDa protein that is found in skeletal/cardiac muscles |
What is the role of this gene? (Xp21) |
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Plays an important role in maintaining the structure muscle cells |
Role of dystrophin |
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Cytoplasm, adjacent to the sarcolemmal membrane in myocytes |
In the muscle cell, where is dystrophin located? |
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The plasma membrane over the Z-bands where it forms a strong mechanical link to cytoplasmic actin |
Dystrophin molecule concentrates at? |
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Dystrophin |
Forms an interface between the intracellular contractile apparatus & extracellular connective tissue matrix |
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Role of complex protein in transferring the force of attraction of (t=contraction) to CT |
What is the basis for the myocyte degeneration that occurs in the absence of dystrophin |
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In staining and Western blot analysis |
Muscle biopsy specimens from px with DND show minimal evidence of dystrophin in what tests? |
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-Glucocorticoids (.35mg/kgday), signifixcantly slows down the progrrss |
Pharmacologic tx for DMR |
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Physical therapy |
May be useful to maintain in muscle strength amd fxn |
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-Heart develops fibrosis: mainly in the posterobasal part of the left ventricular wall -chf and cardiac arrythmias occur later -chf who jave may develop in some parts whi have adequate respi muscle fxn |
Cardiac complication of DMD |
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Smooth muscle of gi tract and CNS |
Other complications of dmd? |
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Smooth muscle of GI tract complication |
-Can cause episodic vomiting, abdominal pain and gastric distention -May be mistaken for intestinal obstruction |
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Verbal iq is affected more than performance |
Which iq is more affected in DMD |
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T |
T/F: intellectual impairment is NOT progressive |
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T |
T/f: Average iq of dmd px is one standsrd deviation below the mean |
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T |
T/F: Intellectual impairment is not progressive in DMD |
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Xp21 same as dmd |
Gene responsible for Beckers muscular dystrophy |
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T |
T/F: beckers muscular dystrophy is approx 10 times less frequent than Duchenne |
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3/100,000 live born males |
Incidence if Beckers |
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Proximal leg muscles |
Muscle Most severely affected by weakness and wasting in beckers |
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Proximal arm muscles |
2nd most severely affected muscle in beckers |
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Cranial nerve supplied muscles |
In bmd, what muscles are relatively spared from wasting/atrophy |
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3-6 yrs of age |
At what age does the child's function may improve due to growth and the normal increase kn strength |
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10-12 |
In becker's muscular dystrophy, what age are px unable to walk |
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20 |
Death by __ due to absence of ventilator |
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15 |
Becker px walk past the age of? |
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Life expectancy is decreased |
Difference between dmd and beckers md |
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Ck in dmd 15,000-20,000 iu/L |
Ck in bmd 5-7k iu/L |
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Corticosteroids has not been studied adequately in bmd |
1 difference in tx for dmd and bmd |
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-wheelchairs -scoliosis surg (>35 degrees) -long leg braces -night splints -stretchimg of heel cords, iliotibial bands, and hip flexors |
Supportive care for bmd |
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Autosomal dominant - LGMD1 Autosomal recessive - LGMD 2 |
Pattern of inheritance of limb girdle muscular dystrophy |
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LGMD1 A-C |
Genetic linkage has identified 3 dominantly inherited disorders |
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T |
T/F: in LGMD, it affects both male and females equally, ranging from late in the first decade to the 4th |
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Intellectual fxn remains normal |
Difference of lgmd from dmd and bmd |
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Progressive; pelvic and shoulder girdle |
Lgmd are _____ and affect primarily the? |
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Western blot analysis for dystrophin allows it to be distinguished from bmd and dmd unequivocally |
What differentiates lgmd from dmd and bmd |
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Tx: supportive care -long leg braces, wheelchairs, cardiac and respi problems may require individualized tx |
Tx for lgmd |
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X-linked recessive Autosomal dominant |
Inheritance pattern of EDMD |
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Xlinked; Autosomal |
EDMD1 EDMD2. |
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Mutations of the genes coding for proteins of the Nuclear Envelope |
Pathophysio for edmd |
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Emerin |
EDMD1 caused by mutations in the EDMD gene on the X chromosome that codes for what protein? |
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Emerin |
Ubiquitous inner nuclear membrane protein, present in nearly all cell types. Thought highest expression is in skeletal and cardia muscle |
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Nesprins, f actin and lamins |
Emerin bind to many nuclear proteins such as |
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Lamins A and C |
EMD2 is due to a mutation in the LMNA gene that codes for? |
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Lamins |
Intermediate filaments found in the inner nuclear membranes & nucleoplasm of almost all cells |
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Lamin |
Impt for DNA replication & mRNA transcription |
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1-2 cases per 100,000 people |
Epidem of EMD2 |
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70 different mutations |
In EMD1, how many different mutations have been reported? |
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18 families and 39 sporadic cases |
In LMNA mutations, how many families/cases |
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1. Slowly progressive muscle weakness and wasting in a scapulohumeroperoneal 2. Early contractures of the elbow, ankle, and posterior neck 3. Cardiac conduction defects, cardiomyopathy |
Triad of EDMD |
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Onset usually on teemage years (but the condition can present with neonatal hypotonia) |
Difference of EDMD from DMD and BMD |
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-Muscle weakness before contractures -more common scapular winging -loss of ambulation -isolated or more severe cardiomyopathy |
Few minor differences noted to be more common in EMD2: |
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Cardiac diseasee |
Major cause mortality and morbidity in EDMD |
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Atrial conduction defects (Bradycardia, atrial arrythmias, AV block, atrial paralysis |
Most common disturbances are a result of? |
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EMD2 |
Severe cardiomyopathy with mild myopathy is common in? |
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Emd2 |
Weakness before contractures |
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EDMD1 |
Contractures before weakness are common in? |
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3-5 |
Dmd disorder becomes apparent at what age |
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Yes, but they may appear normal at birth w/ early milestones met on time |
Is dmd present at birth? |
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1sd below the mean |
Average iq of dmd px are? |
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Clumsiness and inability to keep up w/ peers |
First indications of dmd muscle weakness |
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Pelvic girdle muscles, extending to shoulder girdle |
In dmd, weakness begins at? And extends to? |
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Subtle expansion of a modest polyamine repeat tract in a PABP2 in muscle: maps to chromosome 14q |
What is the main defect in Oculopharyngeal dystrophy? |
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deletions of telomeric heterochromatin at chromosome 4q35 |
Main cause of FASCIOSCAPULOHUMERAL DYSTROPHY |
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FASCIOSCAPULOHUMERAL DYSTROPHY |
3rd most common form of muscular dystrophy |
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Fascioscapulohumeral dystrophy |
Genetic heterogeneity has been documented on this dss, occasionally, the dss is linked to chromosome 10 |
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Myotonic dystrophy |
Mc adult muscular dystrophy |
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Myotonic dystrophy |
This disorder is transmitted by in intronic mutation caused by unstable expansion of a CTG trinucleotide repeat sequence at 19q13.3 |
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Fukuyama congenital muscular dystrophy |
Primary defect is in the gene encoding fukutin - a protein whose fxn is still ill-defined |
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Laminin alpha 2 |
Aside sa fukutin, what other deficiency ang related sa congenital musuclar dystrophy |
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Emery-Dreifuss musculsr dystropy |
Results from mutations of genes coding for proteins of the nuclear envelope |
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EMD1 |
Caused by mutations in the EMD gene on the X chromosome that codes for the nuclear envelope protein Emerin |
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EMD2 - autosomal dominant |
Mutation in the LMNA gene that codes for lamins A AND C |
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Provides mechanical strength to the nucleus, helping to determine nuclear shape, and anchoring and spacing nuclear pore complexes |
Fxn of lamins |
