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U5 Microscopic Anatomy > Muscle > Flashcards

Muscle Flashcards

1
Q

General characteristics of smooth muscle

A
  1. Not striated
  2. Innervated by autonomic nervous system (involuntary)
  3. Relatively slow contracting
  4. Located in walls of tubular organs
  5. Capable of regeneration
  6. Smallest fiber diameter of muscle
  7. One nuclei, centrally located
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2
Q

Identify

A

Smooth muscle

AP: Auerbach’s Plexus L: Longitudinal C: Cross section

Cell boundaries are hard to distinguish in H&E

Single, spindle-shaped, euchromatic nucleus in middle of cell

Cytoplasm: homogenous, eosinophilic

Surrounded by cell membrane

Arranged in bundles/sheets

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3
Q

General characteristics of skeletal muscle

A
  1. Usually associated with skeleton
  2. Innervated by cerebrospinal nerves (voluntary mvmt)
  3. Rapidly contracting
  4. Has cross striations
  5. Capable of regeneration after injury
  6. Largest fiber diameter of muscle types
  7. Multinucleated, peripherally located
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4
Q

CT coverings of muscle

A

Epimysium (dense irregular CT): surrounds entire muscle

Perimysium (loose CT): divides muscles into fascicles

Endomysium (reticular fibers): surrounds individual muscle fibers

Integrates action of contractile units

Supports blood vessels and nerves

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5
Q

Identify

A
  1. Skeletal muscle
  2. Tendon

Sarcomeres –> Myofibrils –> Muscle cells (fibers) –> fascicles

Muscles have many muscle fascicles, which have many muscle fibers (cells), which are composed of myofibrils

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6
Q

Red muscle fibers

A

Type I, Type S (slow twitch)

  1. Small diameter
  2. Numerous mitochondria
  3. High myoglobin content
  4. Derive energy from oxidative phosphorylation
  5. Fatigue resistant: adapted for slow contractions over a prolonged period of time
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7
Q

White muscle fibers

A

Type IIB, Type FF (fast, fatigue)

  1. Large diameter
  2. Fewer mitochondria
  3. Low myoglobin content (oxygen carrier in muscle)
  4. Readily fatigued
  5. Derive energy from anaerobic glycolysis
  6. Adapted for rapid contraction
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8
Q

Intermediate muscle fibers

A

Type IIA, Type FR (fast, fatigue-resistant)

  1. Intermediate diameter
  2. Intermediate mitochondria
  3. Intermediate blood supply

Most of the body’s muscles are composed of these fibers

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9
Q

Time frame of skeletal muscle regeneration

A
  1. Satellite cells are activated within 2 hours of injury
  2. They begin to proliferate within 2-3 days
  3. Cellular architecture is restored in about 2 weeks

Other cells involved in regeneration: muscle derived stem cells, bone marrow stem cells with myogenic potential, blood vessel-assoicated progenitors

Activation: 2h

Proliferation: 2d

Restoration: 2w

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10
Q

General characteristics of cardiac muscle

A
  1. Has cross striations
  2. Innervatesd by autonomic nervous system
  3. Rapidly contracting
  4. Makes up wall of the heart
  5. May be capable of regeneration??
  6. Intermediate fiber diameter (in between smooth and skeletal)
  7. Branching of fibers
  8. One nuclei, centrally placed
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11
Q

Satellite cell characteristics

A
  1. Mononucleted without prominent nucleoli
  2. Spindle shaped
  3. Clumped chromatin
  4. Little cytoplasm with few organelles
  5. No myofilaments

Lie between basal lamina and sarcolemma of skeletal muscle

Present in low frequency in adult muscle

Population not static: Increase in number during injury or after exercise, decrease with age

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12
Q

Identify the type of muscle

A

Skeletal muscle

  1. Long cylindrical cells that lie close together in bundles
  2. Each cell is enclosed by a sarcolemma
  3. Each cell contains numerous nuclei, located on periphery of cell
  4. Cells are cross striated

Myofibrils are subunits of skeletal muscle cells

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13
Q

Banding pattern in myofibrils

A

A bands (dark): thick filaments

I bands (light): thin filaments

Z line (disc): cross linking of thin myofilaments. Sarcomere is Z line to Z line

H zone: portion of A band where thin and thick do not overlap

M line: runs through center of sarcomere (center of H band). Titin extends from M line to Z disc, provides elasticity

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14
Q

Organization of muscle

A

Muscles (epimysium) –> muscle fascicles (perimysium) –> muscle fibers (cells) (endomysium) –> myofibrils (sarcoplasmic reticulum) –> sarcomeres

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15
Q

Titin

A

Giant muscle protein

Acts as a passive elastic elements in the I band

Extends from M line to Z lines

Maintains the organization of the myofilaments in the sarcomere

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16
Q

Differences between cardiac and skeletal muscle

A

Cardiac muscle has:

  1. Branching morphology
  2. Single nucleus per fiber
  3. Centrally placed nucleus
  4. Intermediate in size (b/n skeletal and smooth)
  5. Less distinct cross striations
  6. Presence of intercalated discs
17
Q

Intercalated discs

A

Connect individual heart muscle cells (cardiomyocytes), support synchronized contractions. (mechanical attachment, electrical transmission)

Occur at Z lines, can be viewed on longitudinal sections

Presence of gap and adhering junctions

18
Q

(Potential) Regenerative capacity of cardiac muscle

A
  1. Cardiac muscle stem cells
  2. Bone marrow stem cells
  3. Umbilical cord, embryonic, and IPS cells
19
Q

Identify

A

Cardiac muscle in longitudinal section

  1. Nucleus: spindle shaped, central, diffuse chromatin
  2. Intercalated discs

Cross striations not as distinct as in skeletal muscle

20
Q

Atrial Natriuetic Factor (ANF)

A

Hormone, powerful vasodilator

Produced in atria

Granules in cardiac muscle cells that are released in repsonse to muscle wall stretch

Important for homestasis:

  1. Control of water and electrolyte balance
  2. Control of blood pressure
21
Q

Identify

A

Cardiac muscle in cross section

Notice centrally located nuclei

Visible intercellular boundaries

22
Q

Similarities between cardiac and Purkinje muscle fibers

A
  1. Centrally placed nuclei
  2. Branching and anastomosing fibers (connected)
  3. Presence of cross striations
23
Q

Differences between cardiac and Purkinje muscle fibers

A
  1. Purkinje fibers are larger
  2. Myofibrils are displaed toward periphery of myofibers
  3. Purkinje cells are righer in glycogen
  4. Intercalated discs are seldom observed in Purkinje fibers
  5. Purkinje fibers have variable and unusual shapes
24
Q

Identify

A

Purkinje fibers (right ventricle) with endocardium and lumen

Modified for conduction - distribute electrical stimulus to myocardium

Found in interventricular septum of heart

25
Q

DIsease processes that affect the heart

A
  1. Ischemic heart disease (myocardial infarction)
  2. Inflammatory lesions of the heart (rheumatic fever)
  3. Lesions involving heart valves (bacterial endocarditis)
  4. Lesions of impulse-generating and conducting-system
26
Q

Injury to the impulse conducting system of the heart

A
  1. Myocarditis
  2. Chronic myocardial ischemia
  3. Myocardial infarction
  4. Trauma during cardiac surgery
  5. Invasion by metastatic tumors
  6. Most common cardiac arrythmia is a-fib(atrial fibrillation)
27
Q

Disease process that affect skeletal muscle

A
  1. Focal lesions due to trauma
  2. Muscular dystrophies (progressive muscular weakness and wasting)
  3. Polymyositis (progressive)
  4. Neurogenic atrophy (neuro, ALS)
28
Q

Identify

A

Muscularis externa of duodenum

Inner layer of smooth muscle

Outer longitudinal layer above

Cells in between make up Auerbach’s plexus (provides motor innervation to muscular layers)

29
Q

Which skeletal muscle type is most resistant to fatigue?

A

Type I (red fibers)

Type IIA (intermediate fibers)

U5 Microscopic Anatomy (6 decks)

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