Histology - Muscle Flashcards
Intermediate filaments of muscle
Desmin replaces keratin in muscle cells
Satellite cells (muscle)
Undifferentiated myoblasts - able to regenerate muscle tissue by “satellite cell hyperplasia)
Transcription factor only active in satellite cells
PAX 7
Myocyte
Cardiac muscle cell
Epimysium
Dense irregular CT - surrounds entire muscle
Perimysium
Derived from epimysium (less dense CT) surrounds fascicle
Endomysium
- loose CT (reticular fibers) and basal lámina surround each muscle fiber (cell)
Duchenne muscular dystrophy
Deletion mutation in dystrophin (links actin in sarcomere to the plasma membrane of striated cells
(-) end of actin
Tropomodulin - prevents depolymerization
(+) of actin
Bound to z-line by alpha-actinin (prevents polymerization)
Thick filaments
Myosin II
Thin filaments
F actin - tropomysoin + troponin
Tropomyosjn regulates binding of actin and myosin
Proprioception
Cellular mechanism
Muscle spindles and golgi tendon organs allow for this
Spindle - monitor strain/stretch
Golgi (in tendon) - monitor intensity of muscle contraction
Both can inhibit contraction if limits exceeded
Muscle spindles
Intrafusal fibers -
Myocytes vs. skeletal muscle
T-tubules are 3x diameter compared to skeletal muscle with dyads near the z-line
Secrete ANP - excrete NaCl
And BNP - longer lasting compared to ANP but 10x less concentrated
Myocytes vs. skeletal muscle
T-tubules are 3x diameter compared to skeletal muscle with dyads near the z-line
Secrete ANP - excrete NaCl
And BNP - longer lasting compared to ANP but 10x less concentrated
Plasma serum levels of BNP >400 pg/mL
Indicative of heart failure
What holds myocytes together at intercalated disk?
The fascia adherents
What holds myocytes together at intercalated disk?
The fascia adherents
Prevents myocytes from pulling apart during contraction
Desmosomes - at transverse and lateral regions
Modified z-line in myocyte
Intercalated disk
ID tissue in blue box
Skeletal muscle
Nuclei are predominantly located at the periphery of the cells (whereas nuclei would be centralized in cardiac muscle). Furthermore, the superior tissue is tendon.
Skeletal muscle cells are also larger in diameter than cardiac myocytes (smooth muscle cdells are the smallest in diameter)
Pax-7 is a transcription factor known to play a role in the regulation of satellite cells in mammals. Pax-7 knockout mice might be expected to have deficits in regeneration of which tissue under experimental conditions of induced injury?
Skeletal muscle
An injury that results in death of skeletal muscle cells can heal because skeletal muscle contains a population of stem cells known as:
Satellite cells
Duchenne muscular dystrophy is an X-linked recessive disease caused by a mutation in the gene that codes for dystrophin. The disease gets progressively worse; it results in damage to mature muscles and is often fatal. What is the normal function of dystrophin in healthy muscle?
Helps to link actin to membrane proteins of the sarcolemma
ID
Skeletal muscle
ID
Cardiac muscle
Lipofuscin - a byproduct of the breakdown and absorption of damaged blood cells “the pigment of aging”
Muscle growth in weight lifting
Muscle fibers do not divide, but undergo hypertropy (increasing the myofilaments)
When muscles are injured satellite cells divide to form myotubes - then myotubes fuse to become mature muscle cells
Motor end-plates (darker stain)
