Microanatomy - Muscle & Atrophy

Question 1

Features of smooth muscle

Answer 1

No striations, centralized nuclei

Question 2

Features of striated muscle

Answer 2

Peripheral nuclei, cross striations, multi nucleated

Question 3

Features of cardiac muscle

Answer 3

Cross striations, intercalated disks, centered nuclei

Question 4

Features of aerobic muscle fibers

Answer 4

Slow twitch, oxidative, fatigue resistant

Question 5

Features of 2A anaerobic muscle fibers

Answer 5

Fast twitch, oxidative + glycolytic, fatigue resistant

Question 6

Features of 2B anaerobic muscle fibers

Answer 6

Fast twitch, fatigue sensitive, glycolytic

Question 7

Congenital muscle abnormalities

Answer 7

Muscular dystrophy
Myotonia
Polysaccharide storage myopathy of horses

Question 8

Muscular dystrophy

Answer 8

Inherited diseases
Progressive muscle degeneration & necrosis

Question 9

Myotonia

Answer 9

Inability of skeletal muscle to relax
Inherited defects in Na/Cl ion channel function
Fainting goats

Question 10

Polysaccharide storage myopathy

Answer 10

PAS +, location of build up pale pocketed on histopath slides = build up of glycogen

Question 11

Muscle atrophy mechanisms

Answer 11

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

Question 12

Muscle hypertrophy

Answer 12

Physiologic - increased size due to exercise
Compensatory - partially denervated muscle
Primary muscle abnormality - hypertrophic cardiomyopathy

Question 13

Hypertrophic cardiomyopathy

Answer 13

Common in cats, opening shrinks = thickening on ventricular wall & septum
Thrombin atrium & saddle
Predisposed - Persians, Maine coon, American shorthair

Question 14

Features of gross muscle necrosis

Answer 14

Pallor, swelling, white streaks (concurrent mineralization)

Question 15

Microscopic features of muscle necrosis

Answer 15

Fragmented sarcoplasm, hypereosinophilia, regeneration and fibrosis common

Question 16

Selenium/Vit E muscle necrosis

Answer 16

Low levels increase the chance/occurrence of oxidative injury
Common in ruminants, horses, pigs
Tongue, diaphragm and heart most common for examination

Question 17

Toxic causes for muscle necrosis

Answer 17

Growth promoting antibiotics
Toxic plants
Adriamycin

Question 18

Ionophore - growth promoting antibiotics

Answer 18

Monensin, iasalocid
Toxicity results from Ca overload more common in ruminants than horses

Question 19

Toxic plants

Answer 19

Cassia (coffee senna)

Question 20

Adriamycin

Answer 20

Chemotherapeutic agent
Cardiac muscle necrosis

Question 21

Exertional muscle necrosis

Answer 21

Exertional rhabdomyolysis
Common w horses w underlying PSM
Lumbar muscles severely effected myoglobinuria

Question 22

Capture myopathy

Answer 22

Similar to Exertional necrosis. From capture or restrain of nondom species, weakness/tremors
Se

Question 23

Trauma muscle necrosis

Answer 23

Crush injury, laceration, diaphragmatic hernia

Question 24

Ischemic muscle necrosis

Answer 24

Two kinds, compartment syndrome and downer syndrome

Question 25

Compartment syndrome

Answer 25

Swelling and intramuscular pressure within the facial sheath = pressure induced occlusion of blood supply

Question 26

Downer syndrome

Answer 26

Pressure induced necrosis in recumbent animals, pressure from weight can lead to ischemia

Question 27

Myositis - morph features & causes

Answer 27

Inflammation is the primary lesion, necrosis may be concurrent but is secondary to inflammation Causes: bacterial, viral, parasitic, immune mediated

Question 28

Bacteria myositis

Answer 28

Black leg - clostridium chauvoei Spore forming G+ anaerobic Young ruminants, beef>dairy Muscle injury - hypoxia - activation of latent spores Sudden death

Question 29

Toxoplasma Gondii myositis

Answer 29

Young, small animals Morphologic ally similar to Neospora caninum

Question 30

Immune mediated myositis

Answer 30

Polymyositis Inflammation targeting skeletal muscle Acute onset/slow progression Esophageal dysfunction & resp T distress

Question 31

Immune mediated myositis - masticatory myositis

Answer 31

antibodies against 2M myosin protein Targets masseter & temporalis muscle, difficulty eating. Acute = swollen chronic = atrophy

Question 32

Neoplasia - muscle tumors of striated muscle

Answer 32

Rhabdomyoma : occurs in striated muscle, heart of lamb, piglets, larynx of dogs Rhabdosarcoma : more common, found in bladder of young dogs

Question 33

Neoplasia - muscle tumors of smooth muscle

Answer 33

Leiomyoma : GI tract, female repro tract, tan, modular, well delineated mass Leiomyosarcoma : can occur in any organ