MMB (014) Muscle Histology Flashcards
…..is the dense outer coat of collagenous Connective tissue in muscles
Epimysium dense outer coat of collagenous Connective tissue
…..is the CT trabeculae that divide the muscle into fascicles
Perimysium
……is the delicate loose CT extending between muscle fibers.
Endomysium
define the type of muscle fibers and explain the diiferences between the two types
-Green arrows point to Type I muscle fibers : Rich in myoglobin (red) and Aerobic
-Black arrows point to Type II muscle fibers : Rich in glycogen Less myoglobin ,, Anaerobic
Type(I/II) is Related to continuous, weak contractions
While
Type(I/II) is related to intense sporadic contractions
I
II
Postural muscles are rich in type… fibers
Type I
Biceps, triceps and extraocular muscles are rich in Type …. fibers
Type II
….. is An autoimmune disease that is usually associated with autoantibodies directed against acetylcholine “nicotinic” receptors.
Myasthenia gravis
Clinical manifestations of Myasthenia gravis ?
-Ptosis (drooping eyelids)
-Diplopia (double vision)
characteristic features of Myasthenia gravis ?
-Weakness of extraocular muscles
-Dramatic response to cholinesterase inhibitors
.
Mention two types of Muscle dystrophy
Duchenne muscle dystrophy :
- Complete absence of dystrophin
Becker muscle dystrophy :
-Abnormal dystrophin
Mutation in dystrophin gene located on chromosome…..
chromosome X
Function of dystrophin ?
Connects the cytoskeleton of muscle fiber to the basal lamina»_space; Mechanical stability to muscle fibers during contraction
defects in the Dystrophin-glycoprotein complex leads to :
make muscle cells vulnerable to transient membrane tear during contraction»_space; calcium influx»_space; may disrupt intracellular signaling.
End result of dystrophin defects ?
myofiber degeneration»_space; exceeds capacity for repair.
Microscopic features of Duchenne muscle dystrophy ?
-Segmental myofiber degeneration and regeneration with areas of atrophic myofibers
- Muscle tissue is replaced by collagen and fat cells.
-The rest of muscle tissue shows marked variation in size, from small atrophic fibers to large hypertrophied fibers.
Immuno-histochemical examination of dystrophin shows: (in ill patients)
absence of the normal sarcolemmal staining in Duchenne & reduced staining in Becker muscular dystrophy.
Pathogenesis of Becker muscular dystrophy (BMD) ?
—Abnormal but functional dystrophin may be produced, in contrast to the pathology in DMD, in which there is failure to produce dystrophin
— Dystrophin levels in BMD are generally 30-80% of normal
This is the Clinical presentation of ?
Duchenne muscle dystrophy
What exactly are Satellite cells ?
muscle resident myogenic stem cells
Where are Satellite cells located in muscles ?
reside in a niche on the surface of the muscle fiber, beneath the basal lamina
