Musculoskeletal system

What are the 2 portal of entry of the musculoskeletal system?

1. Direct

2. Hematogenous

What are the 6 defense mechanisms & barrier systems of the musculoskeletal system?

1. Skin, subcutis & fascia

2. Vasculature

3. Immunologic responses

4. Adequate tissue antioxidant concentrations

5. Physiologic adaptations

6. Regenerative capacity of myofibers

This musculoskeletal defense mechanism forms structural barriers to protect against external injury

Skin, Subcutis, Fascia

What are the 3 other causes of muscle dysfunction?

1. Physiologic

2. Genetic

3. Nutritional / Toxicosis

Deficiency in these vitamins are muscle dysfunction under nutritional cause

Selenium & Vitamin E

Success of muscle regeneration depends on these 2:

1. Presence of an intact basal lamina

2. Availability of viable satellite cells

T or F: Myofiber necrosis often undergo segmental necrosis.

True

This widespread tissue or cell death of the entire myofibers only happens under severe stress, like:

1. Extreme pressure to the entire muscle causing crush injury

2. Widespread ischemia caused by pressure

3. Thromboembolism of a large artery

Global necrosis

This is a common trigger of necrosis in all cells.

Increased intracellular Calcium

This condition must be considered non-specific response, indicative only of myofiber necrosis.

Myofiber mineralization

These are the stem cells responsible for skeletal muscle regeneration.

Satellite cells

This part of the muscle fiber is essential for a successful muscle regeneration; otherwise, healing occurs by fibrosis (scar formation).

Intact basal lamina

These cells are also known as the muscle stem cells.

Satellite cells

When muscle tissue is injured, the specific type of cell death that occurs is called _________ necrosis.

Coagulative necrosis

Repair of an injured muscle begins when satellite cells move into the damaged area & become _________.

Myoblasts (immature muscle cells)

Myoblasts join together to form a ________ w/c is a new immature muscle fiber.

Myotube

This is the cytoplasm of a muscle fiber

Sarcoplasm

What are the 3 causes of muscle atrophy?

P A D

1. Physiologic muscle atrophy

2. Atrophy by Endocrine disease

3. Denervation atrophy

This is an alteration in myofiber size wherein it’s either a reduction in the volume of the muscle as a whole, or a reduction in the diameter of a myofiber.

Atrophy

A cause of muscle atrophy wherein it is a response to the lack of use, cachexia, or aging is known as __________.

Physiologic muscle atrophy

What type of muscle atrophy occurs as a result of pituitary dysfunction or tumors in aging horses, and is most commonly associated with hypothyroidism and hypercortisolism in domestic animals?

Atrophy by Endocrine Disease

A type of muscle atrophy common in veterinary medicine, exemplified by equine laryngeal hemiplegia (roaring) where affected muscle fibers become progressively smaller in diameter due to loss of nerve supply, is known as __________ atrophy.

Denervation atrophy

An alteration in myofiber size wherein myofibers increase in size by adding myofilaments.

Hypertrophy

What are the 2 causes of muscle hypertrophy?

P C

1. Physiologic hypertrophy

2. Compensatory hypertrophy

This type of muscle hypertrophy occurs naturally with exercise.

Physiologic hypertrophy

This type of muscle hypertrophy results from pathologic conditions that either reduce functional myofibers, increasing the load on remaining fibers, or disrupt normal cellular processes.

Compensatory hypertrophy

This term refers to the necrosis of skeletal muscles.

Rhabdomyolysis

This is the invariable feature of rhabdomyolysis, & clinically, myoglobin could be demonstrated in the urine.

Myoglobinuria

The elevated result of this serum level is one of the most important diagnostic criteria of rhabdomyolysis.

Creatine phosphokinase

What are the 3 types of muscle diseases?

D I N

1. Degenerative

2. Inflammatory myopathies

3. Neoplasms

What are the 5 muscle diseases under degenerative type of muscle disease?

1. Disturbance of Circulation

2. Nutritional deficiency

3. Toxic myopathy

4. Exertional myopathy

5. Trauma

A medical condition where a restriction or blockage in blood vessels reduces blood and oxygen supply to a part of the body.

Ischemia

A severe, life-threatening medical emergency where tissues or organs are completely deprived of oxygen.

Anoxia

What is the primary factor in assessing the impact of ischemia on muscles?

The varying sensitivity of the different cell types that make up the muscle tissue.

What is myofiber’s sensitivity to anoxia?

Most sensitive

What is Satellite cell’s sensitivity to anoxia?

Less sensitive

What is Fibroblast’s sensitivity to anoxia?

Least sensitive

What occurs first when blood supply to a muscle area is obstructed?

Myofiber necrosis

These cells die as a result of myofiber necrosis.

Satellite cells

What are the 2 factors that influence the extent of skeletal muscle infarcts?

1. Size of the obstructed vessel

2. Duration of the blockage

This occurs in downer cows due to increased intramuscular pressure during prolonged recumbency. This leads to localized muscle pallor from myofiber necrosis, resulting from reduced blood flow due to artery compression.

Ischemic necrosis

What are the 4 causes of muscle ischemia?

V E S O

1. Vasculitis / Vasculopathy

2. External pressure on a muscle

3. Swelling of a muscle in a non-expandable compartment

4. Occlusion of a major blood vessel

A type of degenerative muscle disease that is most common in livestock, including cattle, horses, sheep, & goats. Commonly called selenium / vit E deficiency, but selenium deficiency is the primary cause.

Nutritional myopathy

An essential antioxidant required for glutathione peroxidase, an antioxidant enzyme that protects myofibers from oxidative injury.

Selenium

What muscle types are highly susceptible to nutritional myopathy due to their high oxygen demand & continuous activity?

1. Skeletal muscle

2. Cardiac muscle

Which life stage in production animals is most commonly affected by selenium-deficiency disorders (such as White Muscle Disease) due to their strict reliance on trace mineral stores acquired during late gestation?

Neonates

In nutritional myopathy, the affected muscle is pale as a result of necrosis, thus, the common name is __________.

WMD - White Muscle Disease

A type of degenerative muscle disease that is common in livestock due to the ingestion of myotoxins from toxic plants, hay, or contaminated feed.

Toxic myopathy

What are the 3 clinical signs of toxic myopathy?

M R M

1. Muscle weakness

2. Recumbency

3. Markedly increased serum muscle enzymes

What is the primary histopathological hallmark of necrotizing toxic myopathy?

Multifocal skeletal muscle necrosis

What primary criteria or evidence are used to confirm a diagnosis of toxic myopathy in livestock?

identifying toxin in:

1. Feed

2. Pasture

3. Stomach contents

These drugs can cause calcium overload, leading to skeletal & cardiac muscle necrosis.

ionophore antibiotics

These animals are extremely sensitive to ionophore toxicity.

Horses

These animals are more tolerant to ionophore toxicity, but can be poisoned by excessive doses.

Ruminants

What are the 4 examples of ionophore antibiotics?

L M M N

1. Lasalocid

2. Maduramicin

3. Monensin

4. Narasin

A type of degenerative muscle disease that is caused by intense or excessive muscle activity, resulting in myofiber necrosis (rhabdomyolysis).

Exertional myopathies

Another widely used and accurate term for exertional myopathy in wild animals is _________.

Capture myopathy

This type of degenerative muscle disease is more common in animals with underlying disorders such as:

1. Selenium deficiency

2. Muscular dystrophy

3. Electrolyte depletion

4. Glycogen storage disease

Exertional myopathy

Exertional myopathy in horses is also known as ___________ or _____________.

1. Exertional rhabdomyolysis

2. Tying-up syndrome

2 examples of working dogs where exercise-associated myopathy is reported.

1. Greyhound

2. Sled dogs

In this type of myopathy, affected muscles may appear pale pink, or diffusely red-tinged, potentially resembling autolysis. Multifocal pale zones can also occur.

Capture myopathy

This type of degenerative muscle disease is caused by physical injury.

Trauma

Trauma, as a degenerative type of muscle disease, can result in ____________ which is common in dogs, cats, & horses.

muscle rupture in the diaphragm

Healing occurs mainly by ________ , leading to scar tissue & reduced muscle function.

Fibrosis

Aside from muscle rupture, trauma may also lead to 2 other conditions:

1. Myositis ossificans

2. Musculoaponeurotic fibromatosis

What particular muscle in horses is being damaged to its origin during exercise or while struggling to rise?

Gastrocnemius muscle

Which specific muscle group in cattle is most commonly prone to fiber tearing (split) when an animal slips and falls on a slick surface?

Adductor muscle of the hindlimb

What specific post-traumatic condition is characterized by the development of fibrosis and osseous metaplasia within affected skeletal muscle?

Myositis ossificans

A specific post-traumatic condition, seen primarily in horses, characterized by progressive fibrous tissue proliferation that leads to muscle atrophy is known as __________.

Musculoaponeurotic fibromatosis

This refers to the inflammation of the muscle, may or may not be evident, depending on the presence or absence of fluid exudates.

Myositis

The four patterns of myositis are classified based on the distinct anatomical locations where inflammatory cells infiltrate muscle tissue. Identify these four distinct histological patterns of inflammatory cell infiltration:

1. Perivascular infiltration

2. Perimysial infiltration

3. Endomysial infiltration

4. Granulomatous infiltration

What pattern of myositis is characterized by the accumulation of inflammatory cells specifically around the blood vessels within muscle tissue?

Perivascular infiltration