Cardiac Histology Flashcards
What structures can be seen near the nuclei of cardiac muscle cells?
lipofuscin granules
- “gold splotches”
- lysosomal residue
What are some hallmark characteristics of cardiac muscle tissue?
- striated
- intercalated discs
- lipofuscin granules
What is the characteristic shape of smooth muscle nuclei in a longitudinal cut?
-elongated
What types of cells are the endocardium epithelium?
-simple squamous epithelium
What makes up the endocardium?
-endothelium + thin layer of loose connective tissue
What is the main layering difference between the endocardium of the ventricles vs. the atria?
ventricular endocardium has a subendocardial layer
What is the subendocardial layer?
- layer in the endocardium of the ventricles
- thin layer of connective tissue + smooth muscle
What is the thickest middle layer of the heart?
myocardium
How are the cardiac myocytes bundled in the atria?
-bundled in a way that narrows the heart upon ctx
How are the cardiac myocytes bundled in the ventricles?
-bundled in a way to shorten the heart upon ctx
Where are nodal cardiocytes?
- sinuatrial node
- atrioventricular node
What is the function of myoendocrine cardiocytes?
-secrete hormonal peptides
What types of cardiocytes are found in the myocardium?
- contractile cardiocytes
- nodal cardiocytes
- myoendocrine cardiocytes
Why do intercalated discs hold cardiocytes together so well?
-interdigitating junctions make stronger connections b/w cells than smooth surfaces
What are the three membrane-to-membrane connections of intercalated discs?
- fascia adherens (perpendicular)
- desmosomes (perpendicular)
- gap junctions (parallel)
What is fascia adherens?
- actin filaments at the ends of sarcomeres that insert into the junction
- most predominant membrane-membrane connection
What is the role of fascia adherens?
-transmit contractile force
What is the role of desmosomes?
-provide anchorage for the intermediate filaments of the cytoskeleton
What are gap junctions?
-sites of low electrical resistance
What is the role of gap junctions?
-allows excitation to pass b/w cells
What is a T-tubule?
-fingerlike invaginations of the sarcolemma
What is a diad T-tubule that are found in the myocardium?
one T-tubule plus one cisterna of the sarcoplasmic reticulum
Where, along the cardiocytes, are diad T-tubules found?
-at the Z lines
What is the function of the diad T-tubules?
permit uniform contraction of myofibrils within a single cardiocyte
Where are myoendocrine cardiocytes mostly found?
right atrium
What structures are contained within myoendocrine cardiocytes?
atrial granules
What is contained within the atrial granules of myoendocrine cardiocytes?
precursor to atrial natriuretic factor (ANF)
What is the function of atrial natriuretic factor (ANF)?
- target the kidneys to decrease sodium and water retention
- increase glomerular filtration rate (GFR)
Delineate the electrical conduction system of the heart.
sinuatrial node … atrioventricular node … atrioventricular bundle, right/left bundle branches, subendocardial branches
What tissue makes up the fibrous skeleton of the heart?
-dense irregular connective tissue
In what layer of the heart is the fibrous skeleton?
endocardium
What is the role of the fibrous skeleton?
- anchors valves (insertion of muscle)
- electrical insulator b/w atria and ventricles
- maintains shape of atrioventricular canals
- contributes to the septa
What tissue lines the heart valves and why is it beneficial?
- endothelium (simple squamous)
- provides a smooth surface for blood to flow
With what framework structure are the heart valves continuous?
continuous with the fibrous skeleton
What tissue forms the core of the heart valves?
fibroelastic connective tissue
What is a valve ring?
-component of the fibrous skeleton comprised of condensed layer of fibroelastic endocardium
