Muscle PP 1 Flashcards
Sarcomere
Basic contractile unit of a myocyte (muscle fiber)
Sarcoplasm
Cytoplasm of muscle cells
Sarcolemma
Cell membrane of muscle cells
Myofilaments
Made of actin and myosin
Endomysium
Layer of loos CT with fine fibers and capillaries that enclose muscle cells
Fascicles
Bundles where skeletal muscle cells organized
Permysium
Layer of loose CT surrounding each fascicle
To form a muscle, multiple fascicles are enclosed and bound together by a sheath of dense CT known as __________
Epimysium
Type 1 muscle fiber (red)
Slow twitch, fatigue resistant
Rich in myoglobin and mitochondria
Type 2 fibers (white)
Fast twitch, fatigue sensitive
Low myoglobin and mitochondria
CS of muscle disease
Muscle atrophy and hypertrophy
Swelling, weakness, abnormal gait
Muscle spasm
Esophageal dysfunction
What are the 2 main responses to injury?
- Necrosis and regeneration
- Alteration in myofiber size
Hypoplasia
↓ cell number (leading to atrophy)
Loss of motor innervation during development
Degeneration
Only a segment of the myocyte effected
Necrosis
Entire myocyte effected
Lesions associated with muscle disease
Diffuse paleness or streaks in muscle (gross)
Swollen hyalinized, fragmented sarcoplasm, loss of cross striations
+/ - mineralization of sarcoplasm
Histopath lesions associated with muscle disease
Myoglobinemia and myoglobinuria
↑ serum creatine phosphokinase
What causes degeneration and necrosis?
Ischemia
Bacterial toxins and associated hydrolytic enzymes
↑ intra-sarcoplasmic Ca+
Necrosis and regeneration
- Segmental hypercontraction
- Hyaline degradation
- Fragmentation
Cells associated with necrosis and regeneration
Macrophages
Satellite cells activate and undergo mitosis (activated myoblasts)
Proliferating myoblasts for myotubes
Influx of extracellular Ca+
Chalky and white
1. Dystrophic (Ca+ in dead/ dying muscle)
2. Metastatic (metabolic disorders and plants with Vit D)
Cestrum Diurnum (plant)
Affects arteries, tendons and ligaments but not skeletal muscle
Glycoside yields Vit. D3
Solanum Malacoxylon (plants)
Hypervitaminosis D
Tendons arteries and kidney
Atrophy
↓ mass due to fewer and shorter myofilaments
Due to ↓ work load or loss of motor innervation
Physiologic causes of atrophy
Disuse, cachexia, and aging
Endocrine based atrophy
Most common in dogs: hypothyroidism, hyperadrenocorticism
Equine’s cushings (PPID)
Denervation atrophy
Equine laryngeal hemiplegia (left recurrent laryngeal nerve)
Hypertrophy
↑ mass due to sarcomeres (cell size)
Due to ↑ workload
↑ volume and weight
Degenerative diseases of muscle
Trauma → ischemia
Leads to muscle damage and neuropathy
ex: downer cows
Muscular Dystrophy
Inherited progressive myodegeneration and myonecrosis
Defective dystophin gene
Malignant hyperthermia
Inherited defect in Ca-gating regulation → uncontrolled release of Ca from sarcoplasmic reticulum
Acute myodegeneration and myonecrosis
Triggered by stress, halothane anesthesia
Other names for malignant hyperthermia
Porcine stress syndrom or Pale soft exudative pork
CS with malignant hyperthermia
Normal until triggered
Severe muscle rigidity and ↑ body temperature
Muscles pale pink moist, swollen with cooked appearance
Pulmonary edema
Rapid autolysis
Neuromuscular dysregulation
MG
Acquired: destroys ACh receptors on myocyte
Inherited: inadequate # of ACh receptors
Steatosis (lipomastosis)
Replacement of muscle tissue by adipose tissue
Common in fattened pigs
No CS, found @ slaughter
