Cardiac Histo Flashcards
What are the characteristics of smooth muscle?
- bundles of elongated fusiform cells
- centrally located nuclei
- GAP JUNCTIONS
- NO STRIATIONS
- continuous low force contraction (respond to ANS)
- NOT WAVY UPON STAINING
How do smooth muscle contract?
- thick & thin filaments anchored to cytoplasmic densities
- dense bodies contain design and vitmentin
- tension transmitted via densities to membrane
What is special about smooth muscle contraction?
Lacks T-tubules (unlike cardiac and skeletal)
What are characteristic of cardiac muscle?
- Y - shaped
- branched ; extensive capillaries
- intercalated discs
- purkinje cells
- lipofuscin granules (lysosomal residue)
What are intercalated discs?
transverse junctions at ends of cardiac cells the allow passage of electrical current
What are Purkinje cells?
modified cardiac m. cells that act as the pacemaker for the heart
What is the epicardium made of?
dense fibrocollagenous CT w/ elastic fibers, lined with mesothelium
What is the Pericardium made of
serous membrane = mesothelial lined tissue (simple squamous)
What 3 cell types make up the myocardium?
1) cardiocytes
2) nodal cardiocytes (SA & AV nodes)
3) myoendocrine cardiocytes (hormone)
What are characteristics of the myocardium?
striations ; IC discs ; DIAD t-tubule ; lipofuscin granules ; mito ; serial granules (myoendo)
What are the characteristics of IC discs?
-interdigitated junctions b/w cariocytes ; always line up with Z lines
What are the functions of IC discs?
1) bind cells
2) help transmit the force of contraction
3) transmission of electrical pulse
What are the 3 membrane to membrane contact the IC discs makes and their function?
Transverse (perpendicular)
1) fascia adherent -> actin filaments at end of sarcomere = transmit force of contraction **
2) desmosomes = anchor for intermediate filaments of the cytoskeleton
Longitudinal (parallel)
3) gap junctions - transmit electrical impulse (low resistance)
What is special about the t - tubule system of the myocardium?
its DIAD = 1 T-TUBULE & 1 CISTERNA
-permits uniform contraction of a myofibril w/in a single cardiocyte
What are nodal cardiocytes?
modified cardiocytes w/in SA & AV nodes that initiates and relay electrical signals
-parasympathetic sna sympathetic fibers end here
What is the ONLY change nodal cardiocytes can make?
on the intrinsic HR
What are Purkinje fibers?
specialized cells that conduct electrical impulses for coordinated contraction
- ^ ^ ^ glycogen
- lack t-tubules (mostly)
appear “puffy and round”
What are myoendocrine cardiocytes?
atrial cells that contain membrane bound granules
ie = precursor for atrial natriuretic factos (ANF) = decrease Na and H20 retention
What is the endocardium made of?
endoderm + thin layer of loose CT
How are the ventricular and atrial endocardium different?
the ventricle = sub endothelial cells (Purkinje)
What makes up the Fibrous/Cardiac Skeleton and where is it located?
-dense irregular CT located in endocardium
What are the roles of the fibrous skeleton?
1) anchors valves & sure. AV canals to maintain shape
2) contribute to IV & IA septa
3) extends into valve cusps & chordae tendonae (insertion of cardiac m. and electrical insulator)
What are the heart valves composed of?
core of fibroelastic CT (lamina fibrosa) covered by endothelium
- continuous with cardiac skeleton
- fibroelastic layer= condense to form valve ring to form central portion of valve
