Unit 1- Skeletal Muscle Flashcards
Muscle Membranes
Endomysium, perimysium around fascicles, and epimysium around entire muscle
Sarcomere
Structural and functional unit of skeletal muscle
Evaluation of muscle fibers
Contraction of muscle fibers can be precented by clamping before formalin fixing
Type I Muscle FIbers
Red, slow twitch, slow fatiguing fibers are rich in mitochondria, get energy from oxidative phosphorylation, and stain for SDH
Type II Muscle FIbers
White, fast twitch fibers get energy from glycolysis and stain darkly with myosin-ATPase reaction, used in short bursts of athletic activity
NADH Stain
Stains mitochondria, coloring type I fibers darker nlue
Pallor
Post mortem change, may be secondary to anemia, common in neonates and especially calves
Red Discoloration
Post mortem change due to rhabdomyolysis or putrefaction
Rigor Mortis
Post mortem contraction of muscles, starts in the jaws and moves caudally, starting after 2 hours and peaking after 24
Disturbances of Growth
Atrophy, hypertrophy, and hyperplasia
Reaction to Injury
Degeneration/necrosis, calcification, and regeneration
Congenital Inherited Defects
Arthrogryposis, muscular dystrophy, PSM, PSS
Nutritional Myopathy
White Muscle disease
Exertional Myopathies
Azoturia, HYPP, canine rhabdomyolysis, capture myopathy, compartment syndrome
Traumatic Myopathies
Downer syndrome, post-anesthetic myopathy, crush syndrome
Bacterial Inflammatory Diseases
Malignant edema, black leg
Parasitic Inflammatory Diseases
Trichinosis, cysticercosis, sarcocystosis, toxoplasmosis
Idiopathic Inflammatory Diseases
Canine masticatory myositis, canine dermatomyositis
Primary Neoplasia
Rhabdomyoma, rhabdomyosarcoma
Denervation Atrophy
Damage to the nerve causes rapid loss of muscle mass, long standing denervation can result in fibrosis and steatosis, polio myelitis
Disuse Atrophy
Innervation is intact but atrophy is related to immobilization of the body part
Atrophy of Cachexia
Depletion of fat stores and reduction of type II fibers in muscle mass occurs slowly over time
Laryngeal Hemiplasia
Roarer horses, left crico-arytenoideus dorsalis muscle atrophies due to recurrent laryngeal neuropathy
Hypertrophy
Increased size in muscle fibers due to increased work load, can be enhanced by steroids
Hyperplasia
Increased number of muscle fibers
Double Muscling
Beef cattle have hyperplasia due to an inherited defect in the myostatin gene, cases dystocia, bully whippet syndrome in whippet dogs
Degeneration
Sequel to myofiber injury that occurs segmentally along the myofiber, can be reversible with preservation of basement membrane and satellite cells
Necrosis
Destruction of basement membrane and satellite cells causes irreversible damage in cases of severe injury
Rhabdomyolysis
Release of myoglobin in the interstitium
Microscopic Myofiber Degeneration
Swollen rounded cells, more eosinophilic, sarcoplasm becomes more homogenous, hypercontraction
Calcification
Sequel to degeneration, mitochondrial calcium overload causes white, chalky, gritti foci
Muscle Repair
Intact basement membrane provides framework for satellite cells to become myoblasts and form multinucleated cellular bands
Scarring
Disruptive trauma causes fibrous connective tissue to replace muscle during repair
Nuclear Rowing
Sign of muscle regeneration, myoblasts line up during repair
Determining Lesion Cause
Assessing distribution and duration of lesions
Monophasic Lesion
Acute injury and regeneration occurs all at once
Polyphasic Lesion
Chronic injury and regeneration occurs in different stages
Focal Monophasic Injury
Occurs due to a single incident; IM injection
Multifocal Monophasic Injury
Single exposure to strenuous exercise or muscle toxin
Polyphasic Muscle Injury
White muscle disease, muscular dystrophy, ongoing injury causes both degeneration and regeneration to be observed
Arthrogryposis
Aborted cattle and sheep with rigid joints and grotesque limbs, associated with damage to CNS and denervation of muscles or in-utero toxins or infections
Muscle Dystrophy
Genetic, progressive degenerative muscle disease, inadequate regeneration
Duchenne’s Muscular Dystrophy
Mouse, dog, cat, and human lack dystrophin that strengthens muscle and protects it
X-Linked Dystrophin Defect
Affected golden retrievers have muscle degeneration and fibrosis, characteristic splaying of forelimbs
Equine Polysaccharide Storage Myopathy
Quarter horses exhibit hind limb lameness, reduced muscle mass, and PAS accumulation in type II fibers
Porcine Stress Syndrome
Mutation in the skeletal muscle ryanodine receptor gene causes heavy-muscle pigs to overheat, not breathe, cardiac collapse, and death when stressed.
PSS Pathogenesis
Defect in the ryanodine receptor causes uncontrolled Ca release and excessive muscle contraction and heat
Extramuscular PSS Lesions
Acute heart failure, pulmonary edema and congestion, hydropericardium, hydrothorax, hepatic congestion
PSS Muscular Lesions
Pale, swollen, wet muscles of the back thighs and shoulders, and retraction caps and myofiber degeneration
White Muscle Disease
Vit E/Selenium deficiency in young ruminants and piglets allows oxidative damage to skeletal muscles and heart, lameness and reluctance to move
White Muscle Disease Affected Muscles
intercostals, diaphragm, thigh and shoulder muscles, tongue and neck in nursing calves
White Muscle in Lambs
Right side of the heart
White muscle in calves
Left side of the heart
Exertional Myopathies
Muscle damage initiated by muscle activity
Hyperkalemic Periodic Paralysis
Linked to Impressive quarter horse descendants, alteration in sodium channel allowed potassium release leading to transient muscle spasms, flaccid paralysis, and death
Equine Exertional Rhabdomyolysis
Monday morning disease, heavy horse breeds worked hard during the week have sweating, heavy breathing, and stiff hind leg muscles after resting on weekends
Exertional Rhabdomyolysis Death
Tearing of muscles releases nephrotoxin myoglobin, leading to death
Capture Myopathy
Acute disease in wildlife that are chased during capture or transport leading to muscle degeneration, necrosis, and hemorrhage, myoglobinuric nephrosis may occur
Compartment Syndrome
Ischemic damage in muscles surrounded by heavy tissue sheaths when subject to vigorous contraction, areas of scarring occur instead of regeneration
Compartment Syndrome Poultry
Occurs in supracoracoideus in poultry after vigorous wing flapping
Downer Syndrome
Ischemic necrosis of ventral and limb muscles after recumbency in cows and heavy animals
Equine Post Anesthetic Myopathy
Ischemic damage in horses after anesthetic is used
Crush Syndrome
Similar to Downer’s, caused by acute trauma
Rupture of Diaphragm
Sudden increase of intra-abdominal pressure in dogs, cats, and horses
Rupture of Gasctrocnemius
Spontaneous rupture in racing greyhounds and horses
Tearing of Adductor
Occurs in cows that do the splits on slippery floors, severe damage to basement membrane results in fibrosis
Malignant Edema
Gas gangrene, wound infection with anaerobic clostridia, inducing extensive muscle necrosis, secondary to deep puncture in domestic ruminants
Black Leg
Activation of latent Clostridium chauvoei spores after being ingested causes rapid death in cattle, air bubbles will be palpable in scapular or thigh area
Black Leg Lesions
Characteristic in thigh and scapular region, also in tongue and heart
Trichinosis
Larvae encyst in tongue, masseter, diaphragm, intercostals, and ocular muscles of pork, bears, and aquatic animals and infect human when poorly cooked
Cysticercosis
Taenia tapeworm larvae encysted in muscle of intermediate hosts, causes cysticercosis in humans when eggs are ingested
Sarcocystosis
Cone shaped protozoal bradyzoites in cysts in striated muscle, may lead to abortion
Toxoplasma
Can cause muscle lesions, important cause of abortion in sheep
Masticatory Myositis
Antibodies formed against type 2M myosin causing swollen painful jaw and atrophy, german shepherds predisposed
2M Myosin
Unique myosin isoform in masticatory muscles
Acute Masticatory Myositis
Eosinophilic myositis
Acute masticatory myositis
Atrophic myositis
Dermatomyositis
Dermatitis and myositis in masticatory muscles in collies and shelties, spontaneous recovery
Rhabdomyoma
Benign congenital tumor originating in the heart, common in cattle, sheep, and pigs
Rhabdomyosarcoma
Metaplastic tumors arise from areas with no striated muscle, occurs in head and neck in young animals