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
what are the four components of the blood vascular system?
pump- the heart, distribution- arteries, exchange bed- capillaries and sinusoids, and collection system veins
what is the general organization of the lymph system?
capillary-exchange and collection, valves- unidirectional flow, lymph nodes- interposed filters, no pump- slow passive flow, collection ducts- empty into veins.
what is the make up of the tunica intima in arteries?
endothelium-weibel-palade bodies (coagulating factor VIII in blood vessels larger than capillaries), vasoactive functions; basement membrane; subendothelial connective tissue; internal elastic lamina (IEL); changes assoc. with dec in size: IEL becomes prominent in muscular arteries, IEL disappears in small arterioles just before capillaries
What is the make up of the tunica media in arteries?
smooth muscle, elastic fibers/lamina, changes associated with decrease in size: initial decrease in elastic tissue, secondary decrease in smooth muscle cells
What is the make up of the tunica adventitia in arteries?
external elastic lamina (EEL), connective tissue, vasa vasorum & blood supply of BV, sympathetic nerves, changes associated with decrease in size: increases in size relative to tunica media, EEL disappears before IEL
what is the make-up with the arteriosclerosis?
hardening of arteries, thickening and loss of elasticity of wall; presence of atheromata, mokenbergs calcific sclerosis, proliferation of fibromuscular elements and/or endothelial thickening
What is atheromata?
fatty streak deposits of lipids in phagocytic cells and fibrous plaque, roughened lining attracts platelets which initiates formation of thrombus
What are monkebergs medial calcific sclerosis?
fibrosis and calcification of media
How are myointimal cells involved in atherosclerosis?
they are intimal SM cells, proliferate and can cause atherosclerotic plaque; potential of both fibroblasts, macrophages and smooth muscle cells in intima, injury infection/trauma cause adhesion molecules to bind monocytes and differentiate into macrophages, foam cells or lipophages- endocytosis of cholesterol by macrophages and myointimal cells
What are the treatments for arteriosclerosis?
statins to reduce cholesterol biosynthesis; bile acid sequestering drugs to lower liver cholesterol
What is the structural differences with large arteries?
the tunica intima has thicker subendothelial connective tissue and poorly defined IEL, indistinct due to elastic tissue in TM, becomes split with age,; tunica media- thickest and largely elastic; tunica adventitia- vasa vasorum, EEL poorly defined, may be split, sympathetic nerves
How do the structural components of the large arteries affect the function?
high pressure and flow distend during systole, elastic fibers increase compliance the reason for the elastic recoil during diastole, reduce peaks
What can lead to aortic aneurysms?
in abdomen weakening by atherosclerosis; marfans leads to dissecting aneurysm usually in the ascending aorta
How are the structural components in muscular distributing arteries unique?
tunica intima is thin but with prominent IEL, tunica media is largely smooth muscle, tunica adventitia is thick with prominent EEL, vasa vasorum, lymphatics and nerves only penetrate out layer of media
How do the structural components in muscular distributing arteries affect the function?
distribute blood to various vascular beds, help maintain central blood pressure by controlling run-off
How are the structural components in arterioles different?
tunica intima absence of IEL in all but largest arterioles, tunica media 2-5 layers of SM gradual reduction of layers, tunica adventitia- no EEL, function-control perfusion pressure, major regulator of blood flow, autoregulation, autonomic nerves- not all innervated but diffusion of norepinephrine
How do the structural components in precapillary (terminal) arterioles?
metarterioles- no elastic lamina, 1-2 smooth muscle cells, serve as AV shunts, true capillaries are branches; precapillary sphincters- guard openings of true capillaries, involved in heat regulation
What are the important functions of precapillary arterioles?
metabolic control and temperature regulation
What components make up the capillaries?
endothelium-nucleus right on lumen, basement membrane, pericytes- cytoplasm between lumen and nucleus, fixed macrophages, mast cells-secrete heparin, and rare nerve fibers
what are the important structure details of the endothelium in capillaries?
cells elongated along capillary axis, attached by both occluding junctions and communicating gap junctions, oval or elongated nucleus can bulge into lumen or out, contractile- cytoplasmic filaments, and pinocytotic vesicles and vacuoles
What are the important structure details of basement membrane?
continuous in blood vascular system, prominent in brain (together with zonula occludens forms blood-brain barrier), discontinuous in sinusoids and lymphatic system, collagen type IV- major constituent, no periodicity, elastic fibers
Where can pericytes be found and what is their function?
enclosed in own basement membrane, discontinuously and irregularly spaced, particularly numerous in blood brain barrier, nucleus bulges away from lumen; mechanical support of capillary wall, contractile to modulate blood flow, regulate permeability, regulate microvascular angiogenesis, possibly phagocytic, mesenchymal stem cells giving rise to endothelium or vascular smooth muscle cells, recently as contributor to tumor angiogenesis and target of antiangiogenic therapies
What forms the barrier of capillaries?
endothelium, basal lamina and pericytes, and adventitia
what is the function of capillaries?
inhibit clotting (prostacyclin) and trigger blood coagulation (tissue factor), secrete vasoactive factors to maintain vascular tone: nitric oxide-vasodilate and endothelin 1- vasoconstriction, express adhesion molecules (weibel-palade bodies of arterioles)- migration
How is angiogenesis achieved?
formation of new vessels, regulated by VEGF- interact with VEGF-R2 receptor on angioblastto proliferate and with VEGF-R1 on endothelial cells to form capillary tubes, VEGF and angiogenic factor produce capillary sprout from existing vessel
How does angiostatin/endostatin function?
block angiogenesis, important in battling tumor progression
What are the structural details of continuous capillaries?
muscle tissue, no pores or fenestrations, continuous basal lamina, numerous pinoyctotic vesicles and many tight junctions
What are the structural details of fenestrated capillaries?
contain pores 600-800 nm in diameter, with diaphragm (glands, intestinal villi), thin membrane, aid in selective permeability; without diaphragms (kidney glomeruli)- no membrane, free movement of macromolecules
What are the structural details of sinusoids?
false capillaries, discontinuous capillaries; discontinuous irregular channels, no or discontinuous basement membranes, lined by variety of cell types, reticulo-endothelial system (spleen and lymph nodes)
What are the structural details of lymphatic capillaries?
blind-ending bulb-like endothelial cul-de-sacs, irregular lumen (larger than blood capillaries), much less continuity of endothelial cells, basal lamina absent or very discontinuous, no pericytes, anchoring filaments
What are the structural details of venules?
tunica intima- endothelial tube; tunica media- pericytes in smaller vessels, isolated smooth muscle cells only in largest
what is the function of venules?
postcapillary venules drain capillary bed, site of inflammatory response due to histamine and serotonin of fluid (edema) and WBC
What are the structural details of medium veins?
tunica intima- thin, extends into lumen to form valves; tunica media- 1 to 2 layers of circularly arranged smooth muscles, in superficial veins of extremeties, media thicker, smooth muscle more longitudinally arranged in outer layer; tunica adventitia- thick with longitudinal connective tissue fibers; function- capacitance vessels, blood volume 65-70%- storage of blood, can undergo reorganization when used as bypass vessels
What are the structural details of large veins?
tunica intima-slightly thicker layer than medium veins; tunica media- sparse to thin layer of smooth muscle cells; tunica adventitia- thick layer, prominent longitudinal bundles of smooth muscle cells, elastic and collagen fibers; function is to help maintain vessels open
What are the structural details of lymphatics?
2 layers (tunica intima and adventitia) poorly organized, discontinuous basement membrane and more open junctions, very frequent valves in all but capillaries, anchoring filaments in smaller vessels and capillaries, extensive vasa vasorum in all but capillaries, lymphangion- region between valves acts as a mini pump, lymph nodes- interposed filters, drain into veins
