Histo Muscle Flashcards
What are the 3 major types of muscle?
Skeletal, Cardiac, Smooth
What germ layer does all muscle come from? What is the one exception to this rule?
mesoderm
iris comes from the ectoderm
Describe the fibers of skeletal muscle.
have peripherally located nuclei…are multinucleated; elongated, striated
Describe the contraction of skeletal muscle.
strong, quick, discontinuous, involuntary
Describe the fibers of cardiac muscle.
They are striated, mono nucleated or sometimes binucleated, & there are intercalated discs that allow it to act like a synctium…the fibers are branched
Describe the contraction of cardiac muscle.
strong, quick, continuous, voluntary
Describe smooth muscle fibers.
an agglomeration of cells whose density depends on the amt of surrounding CT…no striations…centrally located cells.
Describe the contraction of smooth muscle. What is it like in a relaxed state? In a contracted state?
weak, slow, involuntary
Relaxed State: elongated
Contracted State: all crunched up
What do all types of muscle contain? What are these an example of?
Actin & myosin. Microfilaments.
What is the structural organization of skeletal muscle?
Sacomeres–>Myofibrils–>muscle fiber=muscle cell–>fascicle–>muscle
How does skeletal muscle develop?
primitive mesenchymal cells of the mesoderm–>myoblasts–>myotubes–>muscle fiber=muscle cell
What are the 3 layers that cover muscle cells/muscle fibers?
Sarcolemma
Basal Lamina
Endomysium (CT)
What covers fascicles?
perimysium
What covers the entire muscle?
epimysium
What are the 3 layers of the CT sheath around skeletal muscle? What are its functions? What produces it?
Endomysium, Perimysium, Epimysium
connects muscle cells that don’t reach the entire length
necessary to transmit forces from one end to the other
allows for blood vessels & nerves to travel w/ the muscle
fibroblasts make it.
What are satellite cells? Where are they found?
stem cells capable of regeneration
found b/w the sarcolemma & the basal lamina
What makes the Z disc? M line?
Z disc: cross-linking actin; M-line: myosin tails
Explain the structure of a sarcomere.
Z disc, I band, A band, H zone, M line, H zone, rest of A band, I band, Z disc
What are the I band, A band, & H band composed of?
I band: only actin; H band: only myosin; A band: myosin & actin & just myosin…essentially the entire length of myosin filaments
What is the relationship of the I band & A band to polarized light?
I band has actin thin filaments & is isotropic to polarized light–light pass thru–light in color
A band has thick myosin filaments & is anisotropic to polarized light–light doesn’t pass thru as much–dark in color.
What is the AI junction?
It is located b/w the A band & I band…it is an invagination of sarcolemma into muscle cells. Allows proper amt. of Ca++ to get into muscle for uniform contraction.
What happens to the sarcomere during contraction according to the sliding filament theory?
Z discs move closer together
I band & H band get smaller b/c they are pure actin & myosin & w/ contraction there is more overlap.
A band stays the same.
What are 2 important elements to keep in mind concerning skeletal muscle contraction?
Triggered by calcium.
All or none.
At what age does the number of muscle fibers stop increasing? Keep in mind w/ pitching baseball!
14 years of age…about puberty
How can you get stronger skeletal muscles?
Increasing thickness–hypertrophy thru repeated exercise
Increasing CT
Increasing Number of Cells–hyperplasia thru excessive exercise; suppression of myostatin; stimulation of satellite cells
NOT the length of muscle cells
What is myostatin?
cytokine produced by skeletal muscle; suppresses skeletal muscle growth
What else is the epicardium called?
Visceral layer of the serous pericardium
What are the layers of the heart (outside–inside) starting with the epicardium on the outside?
Epicardium
Myocardium
Subendocardial Space
Endocardium
What are cardiomyocytes derived from?
Mesoderm
Where are Purkinje fibers found? What are they? What do they do?
Subendocardial space
modified cardiomyocytes
propagate contraction down to the apex of the ventricle–blood squeezes out of the pulmonary trunk & aorta
What are the 3 types of cardiocytes in the myocardium?
Contractile Cardiocytes–contract & pump blood into circulation
Myoendocrine cardiocytes–produces ANP
nodal cardiocytes–responsible for rhythmic contraction–in SA & AV nodes.
Where are purkinje fibers found?
after the AV node, under the endocardium, lining the interventricular septum
How can Purkinje fibers be distinguished from cardiocytes?
Location
Purkinje are larger
Purkinje stain lighter b/c of the high glycogen content
What is found in the subendocardial CT layer?
collagen & elastic fibers made from fibroblasts
blood vessels, nerves, Purkinje fibers
What are the 2 main parts of the intercalated discs & what is found their?
Transverse (vertical): fascia adherens & desmosomes
Longitudinal (horizontal): gap jcns
How can you differentiate smooth muscle from CT?
There are a ton of nuclei in smooth muscle.
What is the exact location of the SA node?
SVC RA jcn
What is the exact location of the AV node?
under the endocardium that covers the intertribal & inter ventricular septa.
What is located inside of a dense body?
plaque
plasma membrane thickening
some microfilaments
Which types of muscle require calcium?
skeletal, cardiac, & smooth muscle!!
What takes up the calcium? What binds it?
Caveolae assist in taking up calcium.
Calmodulin bind the calcium
What do smooth muscle cells look like in the relaxed state & the contracted state?
Relaxed: cigar, longitudinal
Contracted: all crunched up
What is the outside of smooth muscle like?
external basal lamina w/ gap jcns
What is the contraction of smooth muscle like?
weak, slow, involuntary
What is the nucleus situation of smooth muscle?
mononucleated. Centrally located nuclei.
Which types of muscle have T-tubules?
T tubules are found in skeletal & cardiac muscle.
Which types of muscle have gap jcns?
Cardiac & Smooth
What binds calcium in each type of muscle?
Smooth muscle uses calmodulin.
Skeletal & cardiac muscle uses troponin C.
Which types of muscle can undergo mitosis?
Only smooth muscle cells.
Cardiac & smooth muscle don’t have epimysium…what is their CT sheath situation?
They just have CT sheaths & endomysium.
