Cardiac Histology Flashcards
Hallmarks of smooth muscle
no visible striations
elongated nuclei w/ rounded edges
diffuse staining
typically not wavy
Smooth muscle cells & # of nuclei
elongated fusiform cells with 1 nucleus
What connects smooth muscle cells?
gap junctions
Innervation of smooth muscle
inherent rhythmic contraction that is also responsive to ANS to increase or decrease contractile force
How is dense regular CT different from smooth muscle?
more wavy bundles of collagen that align in direction of stress (cells follow waves of collagen bundles)
Describe smooth muscle contraction
thin & thick filaments that anchor to dense bodies which connect to cell membrane
caveolae receive tension from dense bodies & allow for Ca2+ in to initiate contraction
**cells contract as 1 unit & assume globular shape
What are dense bodies composed of?
desmin & vimentin intermediate filaments
Hallmarks of cardiac muscle
striations, intercalated discs
cells w/ varying diameter & centrally located nuclei
lipofuscin granules
LOTS of capillaries
Cardiac muscle cells & # of nuclei
short, branched, Y-shaped w/ 1-2 nuclei
Intercalated discs
transverse junctions @ ends of cardiocytes that allow passage of electrical current (parallel to length of cell)
Purkinje cells
modified cardiac muscle cells that act as “pacemaker” for heart
What composes the pericardium?
Fibrous pericardium (dense CT)
Serous pericardium (parietal & visceral layers)
What is the visceral layer of the pericardium also called?
epicardium (outer layer of heart wall)
Anatomy of the heart wall
epicardium (mesothelium + CT)
myocardium (cardiac muscle)
endocardium (CT + mesothelium)
Epicardium histo features
dense fibrocollagenous CT w/ elastic fibers (lined by mesothelium)
branches of coronary arteries in fat/adipose tissue
Myocardium histo features
striations/intercalated discs/lipofuscin granules
diad T tubule system
Atrial granules
LOTS of mitochondria
Cells of myocardium
cardiocytes (contractile) nodal cardiocytes (SA & AV node) myoendocrine cardiocytes (hormonal peptide)
What are the roles of intercalated discs & where do you find them?
bind cells, transmit forces of contraction & allow spread of excitation
found where cells meet end to end (align w/ Z lines)
3 types of IC discs (memb to memb contact)
Fascia Adherens (actin @ end of sarcomeres) Desmosomes (anchor for intermed filaments) Gap jxns
What is purpose of gap junctions?
parallel membrane connections that allow excitation to pass b/w cells
sites of LOW electrical resistance
What is purpose of fascia adherens?
transverse membrane connections that transmit contractile forces b/w cells
Role of diad T-tubules
permits uniform contraction of myofibrils w/ in 1 cardiocyte (found @ Z lines)
1 tutubule & 1 SR cisterna
Describe the conducting system of the heart
SA node –> AV node –> AV bundle –> R/L bundle branches (down intervent septum) –> Purinje fibers
Role of parasympathetic & sympathetic fibers in nodes
MODIFY rate of intrinsic cardiac muscle contraciton
Nodal cardiocytes
modified cells in SA/AV nodes that start & relay electrical signals
Purkinje fibers
specialized cardiac muscle cells that conduct electrical impulse for coordinated contraction
@ periphery of myocardium w/ fewer myofibrils and striations
Major features of myocardium
Cardiocytes
Intercalated discs
Diad (T-tubule system)
Granules
Myoendocrine cardiocytes (atrial cells)
have membrane-bound granules that secrete atrial natriuertic factor (ANF targets kidneys to decrease H20 retention)
Endocardium in ventricles
has subendocardial layer (CT w/ smooth muscle)
branches of Purkinje fibers
merges w/ myocardium
Endocardium in atria
NO subendocardial layer
Purkinje fibers closer to endothelium
intermixed w/ myocardium
Describe the cardiac skeleton
dense irregular CT in endocardium
Roles of cardiac skeleton
anchors valves & surrounds AV canals for shape
contributes to interventricular & interatrial septa
insertion point for cardiac muscle
electrical insulator between atria & ventricles (to maintain proper pattern of contraction)
What are the heart valves made of?
core of fibroelastic CT covered by endothelium (continuous w/ cardiac skeleton)
What creates the valve ring?
central portion of valve from condensed fibroelastic layer of endocardium
