Cardiac Histology Flashcards
Smooth muscle characteristics
occurs as bundle or sheets of elongated fusiform cells with finely tapered ends
centrally located nucleus
no visible striations
interconnected by gap junctions
continuous contractions of low force
Rhythmic contraction that is inherent but responsive to ANS
During smooth muscle contraction what does the muscle anchor too
cytoplasmic densities/dense bodies
these are comprised of desmin and vimentin intermediate filaments
Characteristics of Cardiac muscle
Cells are short branched and Y shaped with 1-2 nuclei
extensive capillaries
Intercalated discs: transverse junctionsat the ends of cells that allow passage of electrical curent
Purkinje cells: modified cardiac muscle cells that act as the pacemaker for the heart
contain Lipofusion granules near nucleus of some cells, lysosomal residue
types of Pericardium
Fibrous pericardium: outer covering of dense connective tissue
Serous Pericardium:
- Parietal layer on the inner surface of the fibrous pericardium
- Visceral layer that covers the outer surface of the heart
pericardial cavity is the space between the parietal and visceral pericardium
Three layers of the heart wall
Endocardium
Myocardium (cardiac muscle)
Epicardium (visceral layer of serous pericardium)
Characteristics of Epicardium
Outermost layer of the heart wall
synonymous with visceral pericardium
Dense fibrocollagenous CT with elastic fibers lined with mesothelium
Branches of coronary arteries are embedded in the adipose tissue
Characteristics of Myocardium
thickest layer of the heart
Cardiocytes
Nodial cardiocytes (SA and AV node)
Myoendocrine cardiocytes
striations
intercalated disks
lipofuscin granules
Intercalated Discs characteristics
Specialized, interdigitating junctions between cardiocytes
at sites where cells meet end to end, always concide with Z lines
Bind cells, transmit forces of contraction and allow the spread of excitation
What are the three types of membrane to membrane contacts and what region are they found in
Transverse region (perpendicular): Fascia adherens -actin filaments at the ends of terminal sacromeres insert into junction
Demosomes: Provide anchorage for the intermediate filaments of the cytoskeleton
Longitudinal region (parallel) Gap junctions: sites of low electrical fresistance
Diad T-Tubles characteristics
Diad= 1 T-tubule and 1 SR cistern
Fingerlike invaginations of sarcolemma
found at Z-lines
Permits uniform contraction of myofibrils within a single cardiocyte
How does parasympathetic and sympathetic fibers alter the nodes
Only modify the rate of intrinsic cardiac muscle contractiomn
order of Conducting system
Sinoatrial Node AV node AV bundle R/L bundle branches Purkinje fibers
Characteristics of the Purkinje Fibers
Specialized cardiac muscle cells that conduct electrical impulses that allow coordinated contraction
fewer myofibrils but an increase in glucogen
larger and typically seen at periphery of myocardium
they lack T tubules
What are Atrial granules
contain precursor of atrial natriuretic factor (ANF)
-ANF targets kidneys to decrease Na+ and H2O retention
these are found in Myoendocrine cardiocytes
these cells are found mainly in the right atrium less in the left atrium and the ventricles
How does the Endocardium differ in the ventricles and the atria
Ventricles: has a subendocardial layer
- thin layer of CT with smooth muscle
- merges with myocardium
- contains branches of purkinje fibers
In atria: the subendocardial layer is lacking
- purkinje fibers are typically closer to endothelium
- and the layer is mixed in with the myocardium
