Pathology of Muscles and Tendons Flashcards
What cells is muscle made up of?
mycocytes and satellite cells
What are satellite cells important in?
healing muscle cells and adjacent bone fracture
What type of cells are myocytes (I am not asking where they belong)?
multinucleated cells
What does development of a myocyte require?
motor innervation
What are the 3 types of myocytes based on innervation?
red (type 1), white (type 2A), intermediate (type 2b)
Where are satellite cells located?
adjacent to myocytes inside the basal lamina
What is the sarcolemma?
the myocyte plasma membrane
What is the role of the T-tubules and where are they located?
they are an invagination of the sarcolemma and are specialized for depolarization
What is the sarcoplasm?
the myocyte cytoplasm
What are myofilaments?
filaments that attach to each other during muscle contraction
What are the types of myofilaments?
myosin II filaments and actin filaments
Myosin II filaments are known as ________ filaments.
thick
Actin filaments are known as ______ filaments.
thin
Where are myosin filaments anchored?
at the M line
Where are actin filaments anchored?
at Z disk
What makes actin filaments Ca regulated?
troponin and tropomysin
What is a sarcomere?
the basic contractile unit of the monocyte
What is the sarcomere composed of?
myofilaments
What does the sarcomere extend from?
z disk to z disk
What is a myofibril?
a linear string of sarcomeres that runs the length of the myocyte
Explain the excitation -contraction coupling reaction.
- nerve impulse 2. wave of depolarization on plasma membrane 3. T-tubule/SR release Ca into the sarcoplasm 4. Ca binds to Tr-Trpm-actin 5. confoormation change 6.actin ratchets up on myosin filaments 7. contraction (ATP dependant) 8. Ca pumbed back into SR (ATP) 9. Relaxation
Describe skeletal muscle hypoplasia.
there are small poorly-differentiated myocytes due to loss of motor innervation during development
Describe skeletal muscle hypertrophy.
increase in muscle mass due to increase in sarcomeres
What usually is the cause for skeletal muscle hypertrophy?
increased work load
Describe skeletal muscle atrophy.
decrease mass due to fewer and shorter myofilaments
What is the cause of skeletal muscle atrophy?
decrease in work load or loss of motor innervation
What exudate types are associated with inflammation of skeletal muscles?
serous, fubrinous, purulent, granulomatous
What is inflammation in skeletal muscles frequently due to?
infectious agents such as bacteria, protozoa, nematode and cestode larvae
What is degeneration of skeletal muscles?
only a segment of the myocyte is effected
What is necrosis of skeletal muscle?
the entire myocyte is effected
What lesions are associated with skeletal muscle degeneration and necrosis?
diffuse paleness or pale streaks, swollen, hyalinized, fragmented sarcoplasm, mineralization of the sarcoplasm, and myoglobinemia and myoglobinuria
What can cause skeletal muscle degeneration/necrosis?
ischemia, bacterial toxins, and associated hydrolytic enzymes, and increased intra-sarcoplasmic [Ca]
What can cause an increase in intra-sarcoplasmic [Ca]?
membrane damage, dysregulation of Ca gating, coagulation of the sarcoplasm
What is muscular dystrophy?
inherited progressive myodegeneration and myonecrosis
What causes muscular dystrophy?
a defective dystrophin gene
What is malignant hyperthermia?
an inherited defect in Ca-gating regulation leading to an uncontrolled release of Ca from the sarcoplasmic reticulum
What lesions does malignant hyperthermia cause?
acute myodegeneration and myonecrosis
What triggers episodes of malignant hyperthermia?
stress and halothane
What is an example of neuromuscular dysregulation?
myasthenia gravis
What is acquired myasthenia gravis?
an autoimmune disease that destroys the acetylcholine receptors on the myocyte and myoneural jjunction
What is inherited myasthenia gravis?
an patient is born with an inadequate number of acetylcholine receptors on the myocyte
What is skeletal muscle segmental regeneration?
degenerated segments of skeletal muscle are removed by macrophaes and replaced by satellite cells
What is skeletal muscle fibrosis due to?
significant inflammation, necrosis, and hemorrhage
What is osseous metaplasia of skeletal muscle?
woven bone production
What is osseous metaplasia secondary to?
hemorrhage
What neoplasias occur in skeletal muscles?
rhabdomyoma, rhabdomyosarcoma, fibrossarcoma, and infiltrating lipomas
What is the function of tendons?
they are the origins and insertions of muscles
What are tendons composed of?
type I collagen
What lesions are associated with tendons?
contracted tendons, traumatic tear/rupture, tendinopathy, and tenosynovitis
What are contracted tendons?
a congenital defect frequently associated with in utero neuromuscular maldevelopment
What results as traumatic tear/rupture to the tendons?
hemorrhage
How does traumatic tear/rupture heal?
via fibrosis - it is replaced with type III collagen
What is tendinopathy?
abnormality in extracellular glycosaminoglycan
What exudate is associated with tenosynovitis?
serous to fibrinopurulent exudate
What can cause tenosynovitis?
trauma and bacterial infections
If chronic, what can cause as a result of tenosynovitis?
adhesions
