7. Cardiac Histology Flashcards
smooth m contains:
bundles of fusiform cells
centrally located nuclei
no visible striations
what is the fxn of smooth m
interconnected by gap jxns - rhythmic contractions inherent (but can be changed by ANS)
continous contraction w low force
how can you differentiate btn smooth M & dense regular CT
smooth m = no waves
dense regular CT = wavy
smooth m
cross section (centrally located nuclei w unstained region)
longitudinal (elongated nuclei w rounded ends)
what are the components that help smooth m contraction occur?
contractile apparatus of think & thick filaments
calveolae - allow movement of Ca2+
dense bodies/cytoplasmic densities - anchor filaments
contract as one unit (globular shape)
what are the dense bodies made of
desmin vimentin intermediate filaments
tension transmitted via these densities
what does cardiac M contain
short, branched, y-shaped cells w/ 1-2 nuclei
extensive capillaries
intercalated discs
purkinje cells
what are intercalated discs
transverse jxns at ends of cells that allow passage of electical current
interdigiting jxns btn cardiocytes
coincide w/ z line
= bind cell, transmit force of contract & spread excitation
what is the fxn of purkinje cells
modifies cardiac M cells that act as a pacemaker for the heart
conduct electrical impulses that allow coordinated contraction
-less myofibrils, lack T-tubules & more glycogen
cardiac M
cross-section: cells vary in diameter w/ central nuclei
longitudinal: striations, intercalated discs
also contain lipofuscin granules - lysosomal residues
what is the difference btn fibrous & serous pericardium
fibrous: outer covering of dense CT
serous: produce serous fluid to prevent friction; line the fibrous pericardium (parietal) & outer surface of heart (visceral)
epicardium aka visceral serous pericardium
= outer layer of heart
= dense fibrocollagenous . CT w/ elastic fibers
-lined w/ mesotheium
contain branches of coronary As embedded in fat tissue
what are the cells that make up the myocardium
cardiocytes - contractile
nodal cardiocytes - in SA & AV node
myoendocrine cardiocytes - secrete hormonal peptides
what is the difference btn the cardiac M bundles in the atria vs the ventricles
atria = more circular to help push down blood
ventricles = figure 8 to help push blood up against gravity
what is the myocardium characterized by
striations
intercalated discs
lipofuscin granules
diad T tubule
mitochondria
atrial granules (myoendocrine cardiocytes)
what is the fxn of the part being pointed to
= intercalated discs
bind cells, transmit force of contraction & spread excitation
what are the 3 types of membrane to membrane contacts of the interdigiting jxns
transverse region
- fascia adherens
- desmosomes
longitudinal region
- gap (nexus) jxns
what are the fascia adherens & what is its fxn
actin filaments at the ends of terminal sarcomeres that insert into the interdigiting jxn
= transmit contractile force btn cells
what is the fxn of desmosomes
provide anshorage for the intermediate filaments of cytoskeleton
what are gap jxns
sites of low electical resistance
-allow excitation to pass btn cells
what are diad t-tubles
1 T tuble + 1 SR cisterna
fingerlike invaginations of sarcolemma @ Z line
- allows uniform contraction of myofibrils w/i a single cardiocyte
what are nodal cardiocytes
modified cells w/i SA & AV nodes that initiate & relay singals =inherent pacemakers
parasym & sym dibers terminate in the nodes & ONLY modify rate of intrisic cardiac m contraction
what are these & what are the fxns
atrial granules (myoendocrine cardiocytes)
contain precursor of ANF –> (increase GFR -> kidneys filter more, decrease Na & h2o retention -> pee more)
how is the endocardium different in the atria vs ventricles
atria: no subendocardial layer w purkinje fibers close to endothelium, intermixed with myocardium
ventricle: contain subendocardial layer - thin layer of CT w smooth m; merge w/ myocardium & contain purkinje fiber branches
ventricular endocardium
atrial endocardium
what is the fibrous (cardiac) skeleton made of & what is its fxn
dense irregular CT in endocardium
- = anchor valves & surround AV canals to maintain shape
- = contribupe to intercentricular & interatrial septa
- =insertion of cardiac M
- = electrical insulater btn atria & ventricles
cardiac skeleton
(CT = chordae tendineae & C = CT)
what are heart valves made of
core of fibroelastic CT covered by endothelium
-fibroelastic layer condense to form valve ring (create central portion of the valve)
