Cardiac Histology Flashcards
How are smooth muscle cells different in appearance from cardiac muscle cells?
- Smooth muscle cells are not striated
- Smooth muscle cells occur as sheets/bundles of elongated fusiform cells
How are smooth muscle cells interconnected?
Gap junctions
What types of contractions do smooth muscle produce?
- Continuous contractions of low force
- Rhythmic contraction responsive to ANS stimulation
What are some of the key histological features of cardiac muscle?
- Cells short, branched, Y shaped
- Extensive capillaries
- Intercalated discs/transverse junctions
- Purkinje cells (may or may not be able to see depending on magnification)
What is present in cardiac cells that allows the passage of electrical current?
Intercalated discs/transverse junctions
What type of cells are present in cardiac muscle that act as the “pacemaker” cells?
Purkinje Cells
What are the key features of the epicardium/visceral pericardium?
- Outermost layer of the heart wall
- Dense fibrocollagenous CT w/ elastic fibers, lined with mesothelium
- Branches of coronary arteries are embedded in adipose tissue
What are some key features of the myocardium?
- Thickest layer of the heart
- Contains
- Striation
- Intercalated discs
- Dyad T tubule system
- Mitochondria (lots-since the heart is always pumping blood)
- Lipofuscin granules
- Atrial granules (myoendocrine cells)
Where are intercalated discs located?
- At sites where cells meet end to end
- Always coincide with Z lines
What are the three types of membrane-membrane contact in cardiac muscle cells?
- Fascia adherens (Transverse region)
- Desmosomes (Transverse region)
- Gap junctions (Longitudinal region)
What are the features of the fascia adherens?
- Actin filaments @ end of terminal sarcomeres
- Transmit contractile forces between cells
What is the most prominent of the three types of membrane-membrane contacts?
Fascia adherens
What are the features of desmosomes?
- Provide anchorage for intermediate filaments of the cytoskeleton
- Prevent tearing depending on the force of contraction
What are the features of gap junctions?
- Sites of low electrical resistance
- Allow excitation to pass between cells
What makes up a Dyad T tubule?
1 T tubule + 1 SR cisterna
Where are dyad t tubules found? What is there function?
Z lines, Permits uniform contraction of myofibrils within a single cardiomyocyte
Define lipofuscin granules
- small bodies that accumulate with age in stable non-dividing cells
- contain material from residual bodies after lysosomal digestion
- Pretty close to the nucleus on histology slide (if staining permits you to see them)
Define atrial granules
- Atrial cardiomyocytes with membrane bound granules
- Contain ANF
- Increases GFR
- Decrease Na+ and H20 retention in kidneys
What are some key features of the endocardium?
- Endothelium + loose aereolar CT
-
Thickness differs in ventricles v atria
- Ventricles have subendocardial layer which contains Purkinje Fibers
-
In the atria, Purkinje Fibers are closer to endothelium and intermixed with myocardium
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What are nodal cardiomyocytes?
- Modified cells in SA/AV node that initiate and relay electrical signals
- LACK INTERCALATED DISCS
- Only MODIFY rate of intrinsic cardiac muscle contraction
What are Purkinje fibers? What are some of their histological features?
- Conducting fibers that generate and transmit impulse
- Located at periphery of myocardium/ adjacent to to endocardium
- Lack T tubules
- Cells larger and have larger nucleus
- Few intercalated discs
- Nuclei are more round in appearance
What are the histological features of the cardiac skeleton?
- Dense irregular CT located in endocardium
- Anchors valves and surrounds AV valves to maintain shape
What is the overall function of the cardiac skeleton?
Electrical insulator between atria and ventricles
What are the histological features of heart valves?
- Continuous with cardiac skeleton
- Core of fibroelastic CT (lamina fibrosa) covered by endothelium
- Fibroelastic layer condenses to form valve ring (makes central portion of valve)
