Muscle Flashcards
1
Q
fiber
A
- very elongated cell
- components of ECM
- processes of neurons
2
Q
types of muscles
A
smooth, cardiac, skeletal
3
Q
smooth muscle
A
- lacks cross striations
- innervated by autonomic nervous system-SNS and PNS
- relatively slow contracting
- located in walls of tubular organs (regulates lumen size)
- capable of regeneration after injury (smooth and skeletal muscle cells, pericytes, bm stem cells)
4
Q
histological appearance of smooth muscle cells
A
- fibers-elongated and tapered
- 200 um length, 5 um diameter
- single nucleus-spindle shaped, located in middle of cell, diffuse chromatin
- eosiniphilic cytoplasm
- arranged in bundles or sheets-held together by CT, staggered arrangement of fibers
- cell boundaries difficult to observe with light microscope
- cell membrane is sarcolemma
5
Q
smooth muscle around blood vessel
A
-smooth muscle and collagen are both eosinophilic, but collagen is brighter pink while sarcoplasm has a blue cast (due to excess RNA)
6
Q
Skeletal muscle
A
- associated with skeleton (except larynx and few other places)
- innervated by cerebrospinal nerves (voluntary)
- rapidly contracting
- has cross striations
- capable of regeneration after injury
7
Q
Epimysium
A
- surrounds entire muscle
- dense irregular CT
7
Q
Perimysium
A
- divides muscle into fascicles
- loose CT
8
Q
endomysium
A
- surrounds individual muscle cells (fibers)
- reticular fibers
8
Q
sarcomere
A
- portion of a myofibril between 2 adjacent Z lines
- functional unit of contraction
- regularity of structure is maintained by titin
8
Q
histological appearance of skeletal muscle
A
- fibers-long and cylindrical, l=20 mm, thick=50 um
- multinucleated-elongated nuclei, peropheral, diffuse chromatin
- cross striated due to myofibrils
9
Q
histological appearance of skeletal muscle
A
- fibers-long and cylindrical, L=20 mm, thick=50 um
- multinucleated-elongated nuclei, peropheral, diffuse chromatin
-cross striated due to myofibrils-
A (dark) band (anistropic in polarized light),
I band (light, does not alter polarized light, isotropic),
Z line,
H band (lacks thin filaments),
M line (site of lateral connections b/n thick filaments)
-sarcomeres
10
Q
histological appearance of skeletal muscle
A
- fibers-long and cylindrical, L=20 mm, thick=50 um
- multinucleated-elongated nuclei, peropheral, diffuse chromatin
-cross striated due to myofibrils-
A (dark) band (anistropic or birefringent in polarized light),
I band (light, does not alter polarized light, isotropic),
Z line,
H band (lacks thin filaments),
M line (site of lateral connections b/n thick filaments)
-sarcomeres
11
Q
Z line
A
- cross linking of thin myofilaments
- transmission of force
- signal transduction
- interface between contractile apparatus and cytoskeleton
15
Q
sarcomere
A
- portion of a myofibril between 2 adjacent Z lines
- functional unit of contraction
- regularity of structure is maintained by titin
16
Q
Titin
A
- giant muscle protein
- extends from M line to Z line
- maintains organization of myofilaments in sarcomere
- acts as passive elastic element in I band
- attaches thick filaments to Z disc
17
Q
Satellite cells
A
- low freq in adult muscle
- mononucleated
- b/n basal lamina and sarcolemma
- spindle shaped
- clumped chromatin
- inconspicuous nuceloli
- scanty cytoplasm containing few organelles
- no myofilaments
- responsible for skeletal muscle regeneration
18
Q
time frame of skeletal muscle regeneration
A
- satellites activated within 2 hrs
- proliferation in 2-3 days
- architecture restored in 2 weeks
19
Q
other cells involved in skeletal muscle regeneration
A
- muscle derived stem cells
- bone marrow stem cells
- blood vessel associated progenitors-mesangioblasts and pericytes
- satellite cells major player-increase with injury and decrease with age
20
Q
pericytes
A
contractile cells that wrap around the endothelial cells of capillaries and venules throughout the body
21
Q
Skeletal muscle fibers
A
red, white, intermediate
22
Q
Red fibers
A
- small diameter
- numerous mito
- high myoglobin
- oxidative phosphorylation
- fatigue resistant
- adapted for slow contractions over a prolonged period of time
- slow twitch
23
Q
White fibers
A
- larger diameter
- fewer mitochondria
- low myoglobin content
- readily fatigued
- derive energy from anaerobic glycolysis
- adapted for rapid contraction
- fast, fatigue
24
Q
Intermediate fibers
A
- intermediate size, myoglobin and mitochondria
- fatigue resistant
- fast
25
Cardiac muscle
- has cross striations
- innervated by autonomic nervous system-involuntary
- rapidly contracting
- makes up wall of heart
- capable of regeneration??
26
Histological characteristics of cardiac muscle
- fibers-branching
- L=100um, D=10 um
- single nucleus-spindle shaped, centrally placed, diffuse chromatin
- cross striations not as distinct as skeletal muscle
- intercalated discs
- presence of secretory granules
- regenerative?
27
intercalated discs
- interface between adjacent cardiomyocytes
- occur at level of Z lines
- presence of gap and adhering junctions (desmosomes and intermediate junctions)
- mechanical attachment b/n cells
- transmission of electrical and chemical stimuli
28
secretory granules
- observed in atrial musculature
| - contain atrial natriuretic factor
29
atrial natriuretic factor
- ANF
- released in response to wall stretch
- plays a role in regulation of cardiovascular homeostasis by controlling water and electrolyte balance and blood pressure
- 28 aa peptide
30
regenerative capacity of cardiac muscle
?
- cardiac muscle stem cells
- bone marrow stem cells
- umbilical cord, embryonic, and induced pluripotent stem cells (IPSC)
31
Purkinje Fibers
- modified for conduction
- responsible for the final distribution of the electrical stimulus to myocardium
- in interventricular septum
32
histological differences b/n purkinje fibers and cardiac muscle
- larger fibers
- myofibrils displaced toward periphery of fibers
- richer in glycogen
- intercalated discs rare
- variable and unusual shapes
similarities-central nuclei, branching fibers, cross striations
33
disease processes that affect the heart
- ischemic heart disease
- inflammatory lesions (rheumatic fever)
- lesions on heart valves- bacterial endocarditis
- lesions of impulse generating and conducting system
34
impulse-conducting system of the heart
- SA node, AV node and AV bundle
| - AV most vulnerable
35
Injury to impulse-conducting system
- myocarditis
- chronic ischemia
- MI
- trauma during surgery
- invasion by metastatic tumors
36
Atrial Fibrillation
- lose synchrony of atria
- fibrillation-flutter-->reduces blood in ventricle, cardiac output decreases, rapid HR
- cardiomyocytes have a midlife crisis- decide to send signals instead of contracting
- leads to clots and stroke-blood thinner
37
muscular dystrophy
- progressive muscular weakness and wasting
- intrinsic defect in muscle itself
- Duchenne-sex linked recessive, males, age 5, dies in adolescence
38
polymyositis
- acute progressive disease begins in adult
- muscular weakness and tenderness
- may be rapidly fatal
39
neurogenic atrophy
- secondary to neuro prob
| - motor neuron disease-anterior poliomyelitis, amyotrophic lateral sclerosis (ALS)
40
histological criteria for diagnoses
- size and shape of muscle fibers
- distribution of fiber abnormalities
- inflammation
- qualitative and quantitative changes in CT
- fiber degeneration or regeneration
- special architectural features
41
atherosclerosis
- lg and med sized arteries
- serious clinical consequences
- focal thickening of inner portion of arterial wall-->
- accumulation of smooth muscle cells in tunica intima-form ECM components of lesions, accumulate lipid, promote lipid deposition in ECM
