Microanatomy - Muscle & Atrophy Flashcards
Features of smooth muscle
No striations, centralized nuclei
Features of striated muscle
Peripheral nuclei, cross striations, multi nucleated
Features of cardiac muscle
Cross striations, intercalated disks, centered nuclei
Features of aerobic muscle fibers
Slow twitch, oxidative, fatigue resistant
Features of 2A anaerobic muscle fibers
Fast twitch, oxidative + glycolytic, fatigue resistant
Features of 2B anaerobic muscle fibers
Fast twitch, fatigue sensitive, glycolytic
Congenital muscle abnormalities
Muscular dystrophy
Myotonia
Polysaccharide storage myopathy of horses
Muscular dystrophy
Inherited diseases
Progressive muscle degeneration & necrosis
Myotonia
Inability of skeletal muscle to relax
Inherited defects in Na/Cl ion channel function
Fainting goats
Polysaccharide storage myopathy
PAS +, location of build up pale pocketed on histopath slides = build up of glycogen
Muscle atrophy mechanisms
Decrease in size of cell or muscle.
Due to disuse,
cachexia - neoplastic cachexia, low muscle large fat amounts, systemic disease, symmetrical atrophy
denervation - following nerve damage, muscle atrophy occurs rapidly, loss of type 1&2 fibers
endocrine disease - hyperadrenocortism
Muscle hypertrophy
Physiologic - increased size due to exercise
Compensatory - partially denervated muscle
Primary muscle abnormality - hypertrophic cardiomyopathy
Hypertrophic cardiomyopathy
Common in cats, opening shrinks = thickening on ventricular wall & septum
Thrombin atrium & saddle
Predisposed - Persians, Maine coon, American shorthair
Features of gross muscle necrosis
Pallor, swelling, white streaks (concurrent mineralization)
Microscopic features of muscle necrosis
Fragmented sarcoplasm, hypereosinophilia, regeneration and fibrosis common
Selenium/Vit E muscle necrosis
Low levels increase the chance/occurrence of oxidative injury
Common in ruminants, horses, pigs
Tongue, diaphragm and heart most common for examination
Toxic causes for muscle necrosis
Growth promoting antibiotics
Toxic plants
Adriamycin
Ionophore - growth promoting antibiotics
Monensin, iasalocid
Toxicity results from Ca overload more common in ruminants than horses
Toxic plants
Cassia (coffee senna)
Adriamycin
Chemotherapeutic agent
Cardiac muscle necrosis
Exertional muscle necrosis
Exertional rhabdomyolysis
Common w horses w underlying PSM
Lumbar muscles severely effected myoglobinuria
Capture myopathy
Similar to Exertional necrosis. From capture or restrain of nondom species, weakness/tremors
Se
Trauma muscle necrosis
Crush injury, laceration, diaphragmatic hernia
Ischemic muscle necrosis
Two kinds, compartment syndrome and downer syndrome
Compartment syndrome
Swelling and intramuscular pressure within the facial sheath = pressure induced occlusion of blood supply
Downer syndrome
Pressure induced necrosis in recumbent animals, pressure from weight can lead to ischemia
Myositis - morph features & causes
Inflammation is the primary lesion, necrosis may be concurrent but is secondary to inflammation
Causes: bacterial, viral, parasitic, immune mediated
Bacteria myositis
Black leg - clostridium chauvoei
Spore forming G+ anaerobic
Young ruminants, beef>dairy
Muscle injury - hypoxia - activation of latent spores
Sudden death
Toxoplasma Gondii myositis
Young, small animals
Morphologic ally similar to Neospora caninum
Immune mediated myositis
Polymyositis
Inflammation targeting skeletal muscle
Acute onset/slow progression
Esophageal dysfunction & resp T distress
Immune mediated myositis - masticatory myositis
antibodies against 2M myosin protein
Targets masseter & temporalis muscle, difficulty eating. Acute = swollen chronic = atrophy
Neoplasia - muscle tumors of striated muscle
Rhabdomyoma : occurs in striated muscle, heart of lamb, piglets, larynx of dogs
Rhabdosarcoma : more common, found in bladder of young dogs
Neoplasia - muscle tumors of smooth muscle
Leiomyoma : GI tract, female repro tract, tan, modular, well delineated mass
Leiomyosarcoma : can occur in any organ
