Lab: Joint Disease 3 & Muscle Flashcards
(36 cards)
Label parts 1-6 to review muscle structure
- Artery
- Perimysium
- Epimysium
- Myofibril
- Muscle fiber
- Endomysium
What is the name of the structure between the two Z bands?
Sarcomere
functional myofibril unit
What is the primary function of the structure labeled SR (sarcoplasmic reticulum) in the image?
Regulates calcium distribution and storage in muscle
With depolarization, the sarcoplasmic reticulum ___ calcium ions into ___
passively releases calcium ions into the cell
With cessation of neural activity, the sarcoplasmic reticulum ___ calcium ions into ___
actively transports calcium ions into the cisternae
What are the two receptors associated with the sarcoplasmic reticulum?
- DHP
- RyR
In this image, mitochondria are labeled “Mi”.
Which muscle fiber type will have more
numerous mitochondria?
Type I
slow twitch/postural
Type I fibers appear pale in
this histological tissue section and Type II fibers are dark.
What fact is most important in determining fiber type?
Type I is dark meat; Type II is white meat
Lower motor neuron conduction velocity
Which of the following is true?
- Endurance muscles will consist of only Type II (fast twitch) fibers.
- All muscles consists of a mix of Type I and Type II fibers.
All muscles consist of a mix of Type I and Type II fibers.
Which functions are best performed by each muscle fiber type?
How do these fiber types respond to training?
Type I:
Type II:
Type I: slow twitch, postural; increase mitochondria with endurance training
Type II: fast twitch, major movers; hypertrophy with strength training
Creatine kinase levels are considered an important diagnostic tool for Duchenne Muscular Dystrophy (DMD).
What are normal levels of creatine kinase?
What would you expect to see in a DMD patient?
Normal CK levels:
- 0-3yo: 60-305
- 4-6yo: 75-230
DMD patients are usually 50-200-fold above normal levels.
Errors in genes responsible for producing ___ are implicated in many cases of DMD.
What does this protein do in muscle?
Dystrophin: connects actin and myosin to sarcolemma
Xp21 gene mutations on X chromosome
dystrophin dysfunction is also the problem with Becker
Duchenne muscular dystrophy
One newer strategy used to treat Duchenne muscular dystrophy is something called Exon-Skipping.
What is this? What does it allow the patient to do?
Small pieces of DNA (molecular patches) are used to mask the exon that you want to skip, so that it’s ignored during protein production.
Allows patient to make dystrophin
gene therapy using plasmids
dystrophin connects cell fibers to cell membranes
Becker Muscular Dystrophy is less severe than DMD because more of the ___ protein is present, which is absent or nearly absent in DMD.
dystrophin
Is Duchenne or Becker muscular dystrophy an inflammatory disease?
No
Examine the image showing extrafusal and intrafusal fibers.
What is the function of each of these fibers?
Extrafusal: movement; have motor neurons
Intrafusal: have stretch receptors (muscle spindle organs); have motor and sensory neurons
Do you think extrafusal or intrafusal fibers will be most affected in cases of Duchenne or Becker muscular dystrophy?
Degeneration of extrafusal fibers
intrafusal fibers remain intact
Note the presence of normal and regenerating fibers. Some regenerating fibers are filled with macrophages. These images depict cellular degeneration associated with DMD in the early stages of the disease process.
Later in the disease process what do you think will happen as
degeneration outpaces regeneration?
Extensive muscle fibrosis
70-year-old female presents with pain in her right hand.
How would you describe the finding at the blue arrow?
How would you describe that of the purple arrow?
Blue arrow: calcification of triangular fibrocartilage complex (TFCC)
Purple arrow: calcification of posterior/dorsal wrist ligament(s)
70-year-old female presents with pain in her right hand.
What would you include on your differential diagnosis as a possible cause of the condition?
What could help you narrow your diagnosis?
DDx:
- CPPD
- Gout
- RA
- DJD
- NA
Radiographs visualize cartilage, then joint aspiration reveals calcium crystal deposition
How would you describe the projection of bone tissue seen at the yellow arrows?
What disease process do you think is responsible for this change?
Yellow arrows: calcification of tendon/ligament
Due to crystal deposition (CPPD)
What tissue types may be involved in this pathology?
- Synovial membranes (pseudogout)
- Articular cartilage (chondrocalcinosis)
- Tendons and ligaments
CPPD
A 30-year-old female presents with joint pain and weakness bilaterally in the upper extremity. She has been very fatigued for several months and is losing her appetite, which has led to about 7lbs of unwanted weight loss. She notes she may be losing hair and her palms have some redness. She notes a similar redness on her cheeks when she jogs outside. You don’t have radiographs yet.
What pathologies would you include in an initial differential diagnosis list for this patient?
Inflammatory:
- Lupus
- Systemic sclerosis
- Rheumatoid arthritis
A 30-year-old female presents with joint pain and weakness bilaterally in the upper extremity. She has been very fatigued for several months and is losing her appetite, which has led to about 7lbs of unwanted weight loss. She notes she may be losing hair and her palms have some redness. She notes a similar redness on her cheeks when she jogs outside. You don’t have radiographs yet.
What lab results would rule out rheumatoid arthritis?
- HLA-B27 negative
- RF negative
