Cardiac Histology Flashcards by Natalie Tupper

Hallmarks of smooth muscle

no visible striations
elongated nuclei w/ rounded edges
diffuse staining
typically not wavy

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Smooth muscle cells & # of nuclei

elongated fusiform cells with 1 nucleus

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What connects smooth muscle cells?

gap junctions

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Innervation of smooth muscle

inherent rhythmic contraction that is also responsive to ANS to increase or decrease contractile force

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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)

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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

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What are dense bodies composed of?

desmin & vimentin intermediate filaments

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Hallmarks of cardiac muscle

striations, intercalated discs
cells w/ varying diameter & centrally located nuclei
lipofuscin granules
LOTS of capillaries

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Cardiac muscle cells & # of nuclei

short, branched, Y-shaped w/ 1-2 nuclei

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Intercalated discs

transverse junctions @ ends of cardiocytes that allow passage of electrical current (parallel to length of cell)

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Purkinje cells

modified cardiac muscle cells that act as “pacemaker” for heart

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What composes the pericardium?

Fibrous pericardium (dense CT)

Serous pericardium (parietal & visceral layers)

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What is the visceral layer of the pericardium also called?

epicardium (outer layer of heart wall)

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Anatomy of the heart wall

epicardium (mesothelium + CT)
myocardium (cardiac muscle)
endocardium (CT + mesothelium)

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Epicardium histo features

dense fibrocollagenous CT w/ elastic fibers (lined by mesothelium)
branches of coronary arteries in fat/adipose tissue

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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 &amp; 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