Cardiac and Vascular Hitsology Flashcards
What structural details make cardiac tissue different from skeletal muscle?
individual cells not syncytium, branched fibers no long parallel cylinders, single centrally located nucleus, myofibrils only 50% of sarcoplasm instead of 90%, intercalated discs connect cells end to end as opposed to single fiber stretching the length of the muscle, spontaneous and rhythmical contraction, T tubules larger and fewer in number and lined with glycoprotein, T tubules located at Z lines, SR less abundant and elaborate, terminal cisternae less organized form dyads, larger more numerous mitochondria, rich in glycogen granules
What are the components of intercalated discs?
macula adherens (desmosomes physically connect cells), fascia adherens which anchor cell membrane to contractile proteins, nexus or gap junction thin and pass electrical current, and occasional intercellular gaps of various size and unspecialized
What are the components of the A band?
length remains constant, M line = dark line in center of A band, L line = 2 lighter lines on either side of M line, and the H zone at longer sarcomere lengths, lighter band beyond L lines
What are the components of the I band?
length changes with contraction, Z line = dark line in center of I band
What is a sarcomere?
functional unit that extends from z line to z line
What is a contraction band?
abnormally shortened sarcomeres
What is the make up of the tunica intima?
simple squamous epithelium that is continuous with vessels, subendothelium = the connective tissue between endothelium and myocardium, the thickest in atria, thinner in ventricles, inner layer thin with fibroblasts and collagen, outer layer thick with elastic tissue and smooth muscle cells in atria, purkinje fibers in the subendothelial layer contain more glycogen
What is the make up of the tunica media in atrial cells?
smaller in diameter than ventricular fibers, contain neuroendocrine granules (atrial natriuretic peptide)- secreted when stretched and cause diuresis and natriuresis
What is the make up of the tunica media in ventricular cells?
fibers arranged in complex spiraling bundles from interior to outside, 180 degree rotation in fiber direction from endocardium to epicardium, decrease circumference and shorten from apex to base
How does myocardium change after ischemia?
loss of contraction, development of wavy fibers
How does myocardium change after infarction?
necrosis, loss of striations, infiltration of leukocytes and scarring, lose nucleus
What are the components of the epicardium?
mesothelium- visceral pericardium, outer layer of epicardium; subepicardium- connective tissue between myocardium and visceral pericardium; it is thicker in ventricles than atria, adipose tissue particularly along sulci, epicardial coronary vessels and lymphatics, and cardiac ganglion cells and autonomic nerves
What is the connective tissue organization in the endomysium?
investment of reticular and collagen fibers
What is the connective tissue organization in the perimysium?
investment of groups of muscle cells, determines structure
What are the components of cardiac skeleton?
annuli fibrosis- ring around openings for attachment of valves; fibrous trigones and conus lig.- interconnect annuli; membranous septum- upper end of interventricular septum; fibrous septum- fibrous tissue in muscular part of interventricular septum
What are the structural components of the valve leaflets?
connective tissue core, normally avascular, collagen concentrated on high pressure side continues into chordae tendineae in AV valves, elastic tissue on low pressure side; AV valves tricuspid and mitral with chordae tendinae and papillary muscles; SL valves aortic and pulmonary, sinuses of valsalva
What problems can occur in valve leaflets?
fibrosis, calcification, vegitations- rheumatic fever, rupture
What is the cellular make up of the SA node?
delicate small fibers with few myofibrils, no intercalated discs, located in beginning of crista terminalis, nodal artery embedded along node
What is the cellular make up of the AV node?
structure similar to SA node, highly branched, no discs, located in floor of interatrial septum between coronary sinus and annulus
What is the cellular make up of the AV bundle of His?
structure similar to AV node except larger, extend from AV node to top of muscular part of interventricular septum
What is the cellular make up of bundle branches?
gradual increases of myofibrils, descends on either side of the interventricular septum
What is the cellular make up of purkinje fibers?
largest fibers with myofibrils packed around periphery, usually contain more glycogen than typical cardiac muscle, prominent intercalated discs, extend from subendocardium into myocardium, continuous with ordinary cardiac muscle
What are the different types of coronary vasculature?
epicardial arteries- muscular distributing arteries embedded in epicardial fat (subject to development of atherosclerosis); intramural arteries- enter wall at right angles to epicardial vessels, most are small and run straight along muscle fibers, don’t develop atherosclerosis; veins- epicardial open to coronary sinus, anterior- open directly into right atrium, thebesian- sinusoids that open in all four chambers