6.4 - Lab - Muscle Pathologies

Question 1

Describe muscle spindle morphology

Answer 1

• Muscle fascicle composed of skeletal muscle fibers that are much smaller daimeter than normal and contain a nervous innervation
• surrounded by a perimysium

Question 2

what are some morphologies that occur in a myocardial infarction

Answer 2

• waviness
• necrosis
• edema
• hemorrhage
• Pyknosis
• Neutrophilic infiltrate
• Macrophages
• Granulation tissue
• Dense Fibrous Scar tissue

Question 3

Waviness is a common morphology following myocardial infarction, describe what it represents/how it happens, and any applicable morphologies you might see

Answer 3

• most easily seen in longitudinal section
• occurs because when an area of heart becomes non-FXNL - the first myocytes that connect to the non-working cell must work harder and thus pull with a greater-than-usual extent against the neighboring tissues they contact

Question 4

Necrosis is a common morphology following myocardial infarction, describe what it represents/how it happens, and any applicable morphologies you might see

Answer 4

= a localized death of cell

• localized is a key concept - compare damaged and healthy tissues in the same specimen to confirm
• dark nuclei

Question 5

Edema is a common morphology following myocardial infarction, describe what it represents/how it happens, and any applicable morphologies you might see

Answer 5

= cell swelling

• intracellular water retention due to breakdown of the mechanisms that normally control osmotic pressure
• can be very difficult to observe

Question 6

Hemorrhage is a common morphology following myocardial infarction, describe what it represents/how it happens, and any applicable morphologies you might see

Answer 6

= release of blood into tissue - usually due to destruction of part of circulation
- would see normally “blood only” cells present in the CT of the muscle:
Basophils, RBCs, Monocytes

Question 7

Pyknosis is a common morphology following myocardial infarction, describe what it represents/how it happens, and any applicable morphologies you might see

Answer 7

= controlled destruction of the nuclear chromatin
- when a cell senses its dying it attempts to put its chromatin a state that it will no longer be able to FXN
Morphology: tightly packed heterochromatin and hyperlobulation of the nucleus

Question 8

Neutrophilic infiltrate is a common morphology following myocardial infarction, describe what it represents/how it happens, and any applicable morphologies you might see

Answer 8

= the accumulation of tissue neutrophils responding to the injury

Question 9

Macrophages are a common morphology following myocardial infarction, describe what it represents/how it happens, and any applicable morphologies you might see

Answer 9

= they are responsible for cleaning up dead tissue as much as possible
- areas of necrotic tissue that cannot be accessed by tissue macrophages will form cysts (which are rare in cardiac tissue)

Question 10

Granulation tissue is a common morphology following myocardial infarction, describe what it represents/how it happens, and any applicable morphologies you might see

Answer 10

= a CT that is rich in vasculature that normally fills a wound
- this vasculature is important for brining the cells and providing the hydrated environment that will facilitate repair of the damaged area

Question 11

Dense fibrous scar tissue is a common morphology following myocardial infarction, describe what it represents/how it happens, and any applicable morphologies you might see

Answer 11

• represents the final resolution of a wound

- unlike the granular tissue that precedes this type of tissue –> scar tissue is largely avascular

Question 12

What is a key difference between denervated skeletal muscle fiber compared with an innervated one

Answer 12

• more nuclei present with the denervated tissue
• also see a breakdown of the typical organization with less clearly delineated fascicles, and less linear structure formation thats typically seen with skeletal muscle