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Histology > Muscle > Flashcards

Muscle Flashcards

(66 cards)

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1
Q

What is found in the muscle tissue…

A
  • muscle cells (myocytes, myofibers)
  • stem cells (satellite cells)
  • nerve supply
  • somatic motor (for voluntary muscles)
  • visceral motor (for involuntary muscles)
  • sensory
  • excitable plasma membranes
  • connective tissue
  • blood vessels, lymphatics
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2
Q

What is found in non-muscle contractile tissue…

A
  • myoepithelial cells
  • glandular tissues
  • myofibroblasts
  • wound healing
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3
Q

Classification of muscles

A

1) Skeletal (striated)

  • voluntary muscles associated with skeletal movement
    • biceps brachii, trapezius, deltoid etc.

1a) Visceral (striated)

  • voluntary visceral muscles
    • upper esophagus, pharynx, tongue, etc.

2) Cardiac (striated)

  • under autonomic (sympathetic/
    • parasympathetic) control

3) Smooth (non-striated)

  • wide distribution
    • gut, bronchioles, blood vessels, ureter, gall bladder, etc.
  • under autonomic (sympathetic/parasympathetic) control
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4
Q

myo…, sarco…, …mysium

A

…mysium (flesh)

Muscle

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5
Q

Sarcolemma

A

plasma membrane + external lamina

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6
Q

Sarcoplasma

A

cytoplasm

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7
Q

Sarcoplamic Reticulum

A

smooth ER

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8
Q

myofiber

A

AKA myocyte = muscle cell

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9
Q

Skeletal Muscle Characteristics

A
  • striated
  • voluntary*
  • long unbranched muscle fibers
  • continuous external lamina
  • no cell-cell gap junctions
  • rich CT investments:
    • surrounding entire muscle
    • surrounding muscle fascicles
    • surrounding muscle fibers
  • multinucleated (true syncytium)

*atypical muscles (usually involuntary, but otherwise is voluntary:

  • lower pharynx
  • diaphragm, etc

The labeled …mysiums are all continuous with tendons

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10
Q

Skeletal muscle fibers - describe the cells

A

multinucleated, giant cells

(range from ~1mm (stapedius) to >1m (sartorius)

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11
Q

ID the tissue

A

skeletal muscle

longitudinal section

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12
Q

ID the tissue

A

skeletal muscle

cross section

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13
Q

myofibrils

A

cytoplasmic collection of sarcomeric units surrounded by the sarcoplasmic reticulum and other organelles; the sarcomere’s A and I bands in adjacent myofibril are in register, thus giving the muscle its characteristic striated appearance

packed with myofilaments; myofilaments consist of repeating sarcomeres

Muscle cells are packed with myofibrils

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14
Q

endomysium

A

between lateral cell boundaries

delicate layer (made from Type III collagen) that surrounds each individual myofiber and contains reticular fibers

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15
Q

Myofilaments

A

myofibrils are composed of myofilaments which consist of actin and myosin

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16
Q

During muscle contraction, what happens to the different bands

A
  • sarcomere shortens (Z-lines
    • move together)
  • neither thin (actin) nor thick
    • (myosin) filaments shorten
  • A band width does not change
  • I band narrows
  • H band narrows

I band - Isotropic

A band - Anisotropic

H band - Ger. Heller (“bright”)

M line - Ger. Mittel (“center”)

Z line- Ger. Zwishen (“between” the I bands)

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17
Q

Excitation-contraction coupling: Skeletal muscle

A

Regulated by Ca2+

  • two sarcomere/t-tubule triads
  • continuous, enlarged SER cisterna
  • propagate depolarization into cell
  • stimulate calcium release from SR
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18
Q

dystrophin complex

A

Contractile proteins are linked to the ECM via the dystrophin complex

Dystrophin connects actin to plasma membrane

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19
Q

Muscular dystrophy

A

dystrophin deficiency:

  • mechanical failure
  • hypercalcemia leading to increased osmosis, mitochondrial rupture
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20
Q

Skeletal muscle fiber types

A

red: (slow-twitch) many mitochondria, myoglobin & oxidative enzymes (aerobic)

(these can contract for long periods without fatigue)

white: (fast-twitch) fewer mitochondria & oxidative enzymes (anaerobic)

(these are quick to fatigue)

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21
Q

motor unit density

A

The ratio of neuro-muscular junctions will change depending on the function of the tissue

coarse control, neuron:muscle fibers = 1:1000’s

fine control, neuron:muscle fiber = ~1:3

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22
Q

Sensory perception

A

provide proprioceptive information and mediate stretch reflex

a. muscle spindle
b. golgi tendon organs

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23
Q

Muscle spindle

A

one type of sensory fiber

provide proprioceptive information and mediates stretch reflex

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24
Q

golgi tendon organ

A

one of the sensory fibers

proprioception and inhibition reflex (protection from overstretching)

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25
Cardiac muscle characteristics
* involuntary * (sympathetic/parasympathetic) * striated * long branched muscle fibers: * formed by end to end cell fusion via specialized cell-cell junctions * discontinuous external lamina * many gap junctions * cells often binucleate * has intrinsic capability to beat
26
ID tissue type
Cardiac muscle, longitudinal view
27
Cartoon diagram of cardiac muscle (no question)
28
ID tissue type
Cardiac muscle, cross section view ## Footnote - note stippling in cytoplasm (myofibrils) - note central location of nucleus (when visible)
29
intercalated discs
Cardiac cell-cell junctions Made up of end-to-end juctions (uses fascia adherens and desmosomes) and lateral cell-cell junctions (uses gap junctions and desmosomes and is discontinuous basal lamina)
30
Excitation-contraction coupling: Cardiac Muscle
Regulated by Ca2+ ## Footnote - one T-tubule/sarcomere: Diad rather than triad - discontinuous, anastomosing cisterna - T-tubules situated at Z-bands - SER does not encircle myofibrils therefore, less efficient than skeletal muscle but cell-autonomous contractility and a functional syncytium (gap junctions) compensate
31
Specialized myocardial cells
Endocrine cells Purkinjee fibers (specialized conducting cells)
32
Endocrine cells
type of specialized myocardial cell ## Footnote - ANF (Atrial Natriuretic Factor) – vasodilator - released in response to high BP, high Na+, angiotensin II - predominantly in atria
33
Purkinjee Fibers
Specialized conducting cells ## Footnote - rich in glycogen - conduct impulses
34
Smooth muscle characteristics
* non-striated * involuntary * unfused, spindle-shaped cells (20-500mM) * central nucleus * discontinuous external lamina * many gap junctions * widely distributed: * hollow organs (GI tract, blood vessels, bladder etc.), skin (arrector pili) * no true sarcomeres
35
ID tissue type
Smooth muscle
36
Excitation-contraction coupling: Smooth Muscle
1) electrical, via gated Ca2+ channels * atypical neuromuscular junction: * neurotransmitters released at 10-200m from muscle = slow excitation 2) mechanical * stretching stimulates mechano-sensitive ion channels ("myogenic" response) 3) hormonal * e.g. oxytocin stimulates uterine contractions Doesn't have t-tubules; caveolae replace T tubule system because deep penetration not needed
37
caveolae
replace T tubule system in smooth muscle
38
Skeletal Muscle Repair
Satellite cell activation * disease (e.g. muscular dystrophies) * damage (e.g. excessive weight training) (although most increased muscle mass during normal training is due to hypertrophy not hyperplasia)
39
Cardiac Muscle Repair
Some satellite cell activation???? * limited mitosis is possible * most repair is fibrotic (scar tissue)
40
Smooth Muscle Repair
Actively proliferates in response to: * damage * physiological needs (e.g. uterine expansion during pregnancy)
41
Skeletal muscle examples
biceps brachii, trapezius, deltoid etc. Visceral muscle: upper esophagus, pharynx, tongue, etc.
42
Cardiac muscle examples
main tissue in the walls of the heart
43
Smooth muscle examples
gut, bronchioles, blood vessels, ureter, gall bladder, etc.
44
Epimysium
outermost CT capsule that contains the bundles of myofibrils arranged into fascicles ## Footnote dense connective tissue sheath (made from type I collagen) on the external surface of the muscle, which is continuous with the tendons that attach the muscle to bones. The epimysium is synonymous with deep fascia in gross anatomy and will frequently be named according to the muscle it covers, such as brachial and crural fascia for the arm and leg muscles, respectively
45
Perimysium
(Made from type I collagen) surrounds groups of fibers and organizes them into fascicles
46
Sarcomere
Sliding filament mechanism for muscle contraction - sarcomere shortens (Z-discs move together) - neither thin (actin) nor thick (myosin) filaments shorten - A band width does not change - I band narrows - H band narrows
47
ID the tissue
Cardiac Muscle
48
ID the tissue
Cardiac muscle cross section ## Footnote - note stippling in cytoplasm (myofibrils) - note central location of nucleus (when visible)
49
ID the tissue
cardiac muscle, longitudinal view Note: intercalated disc
50
ID the tissue
Purkinje fibers - rich in glycogen, which is what gives them the pale appearance - conduct impulses - contractile, but not thought of that way Endocardium is at the top of the picture Cardiac muscle below
51
Dense bodies
Dense bodies are the z-disc (line) equivalent in smooth muscles
52
ID the tissue
Smooth muscle note the dense bodies
53
T-Tubules
perpendicular invaginations of the sarcolemma Once depolarized, impulses travel from the sarcolemma into the musclefiber through T tubules Not found in all muscles; they are found in large cells in order to propegate action potential Not needed in smooth muscle; caveolae replace T tubule system in smooth muscle
54
ID the tissue
Smooth muscle cross-section ## Footnote Note gap junctions (arrows) – in these locations the external lamina is absent
55
ID the tissue
Skeletal and smooth muscle
56
Leiomyomas
Fibroids - smooth muscle tumors almost exclusively found in the uterus
57
ID the tissue
skeletal muscle - longitudinal section
58
ID the tissue
skeletal muscle - cross section
59
ID the tissue
Skeletal
60
ID the tissue
Cardiac
61
ID the tissue
Smooth
62
ID the tissue
Skeletal - cross section
63
ID the tissue
Smooth muscle - cross section
64
ID the tissue
Cardiac - cross section
65
Comparison of muscles (no question)
66
Smooth muscle vs. dense, regular CT of a tendon

Histology (11 decks)

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