Flashcards in TBL12 - Heart, Aorta, Pulmonary Trunk, SVC and IVC Deck (22):
What is the myocardium lined by internally and externally? Where do the coronary vessels and cardiac plexus lie and what function does this serve? What covers epicardial white fat?
1) The thick myocardium is lined internally by endocardium and covered externally by epicardium
2) The coronary vessels and cardiac plexus permeate within white fat that occupies the epicardium and acts as a shock absorber for the heart
3) The epicardial white fat is covered by the visceral layer of serous pericardium
What does the endocardium consist of and what does it line and cover? What does endothelial antithrombogenicity inhibit?
1) Endocardium consists of endothelium that lines the cardiac chambers and covers the subendothelial connective tissue
2) Endocardium also covers the valvular cusps and chordae tendineae
3) Endothelial antithrombogenicity inhibits blood coagulation thereby insuring regular flow through the heart
What do the valvular cusps consist of? What are the atrioventricular, aortic, and pulmonary trunk orifices surrounded by? What facilitates valvular stability?
1) The valvular cusps contain a core of dense connective tissue
2) The atrioventricular, aortic, and pulmonary trunk orifices are surrounded by rings of dense connective tissue
3) Continuity of the connective tissue rings with the connective tissue cores of the valvular cusps facilitates valvular stability
How after invading the endocardium, can streptococcal bacterial infections in children and adolescents be life-threatening?
1) Rheumatic fever is a systemic, immunologically mediated disorder caused by streptococcal bacterial infection of the pharynx or upper respiratory tract in children and adolescents. It affects the joints, dermis, and brain and may also lead to rheumatic heart disease (RHD)
2) RHD may cause inflammation of all three layers of the heart wall, but its most serious complication is an effect on endocardium covering valves of the left side of the heart, which can become ulcerated and scarred and thereby deformed
3) Serious, life-threatening consequences, such as mitral insufficiency and aortic stenosis, may result
Which element of the conducting system is depicted in the image and where is it located?
What do myoblasts of the endocardial tube differentiate into? What enables myocytes to contract rhythmically?
1) Myoblasts of the crescent-shaped endocardial tube differentiate into myocytes that contract spontaneously
2) Gap junctions between the myocytes enable rhythmically contractility of the primitive myocardium
What components make up myocytes? What type of contraction does this lead to?
Like skeletal muscle fibers, myocytes contain myofibrils, myofilaments, and cross striations; thus, myocytes contract via the sliding filament mechanism
What provides energy for myocytic contractility? What insures continuous mitochondrial function?
1) Vast populations of mitochondria provide energy for myocytic contractility
2) The dense capillary network (each myocyte has its own capillary) insures continuous mitochondrial function
How do myocytes position themselves around ventricular lumens? What does this lead to?
During bending of the elongating heart tube, myocytes wrap around the ventricular lumens in a helical fashion making ventricular contraction analogous to “wringing water from a wet towel” and thereby maximizing systolic output
What two components make up intercalated discs? What are their functions?
1) The intercalated disc contains component anchor junctions and gap junctions
2) Gap junctions enable rhythmic myocardial contractility
3) Anchoring junctions prevent disruption of the myocytes during systole
Can myocytes regenerate after myocardial infarction?
Regeneration of cardiac muscle cells after injury does not readily occur, as no satellite cells are associated with the cells
Why are myocytes stretched in patients with dilated cardiomyopathy and why can the disease be fatal?
1) In familial dilated cardiomyopathy (DCM), a heritable form of heart failure, mutations exist in cytoskeletal proteins that disrupt intercalated disc morphology by dissociating junctions between myocytes and disrupting myofibrillar organization and contractile function
2) DCM is the most common type of cardiomyopathy, in which there is stretching of disease-affected myocytes, which leads to enlargement of one or more chambers of the heart and thinning of ventricular walls
3) These changes progressively weaken the heart’s pumping ability
Where do myocytes contract spontaneously at the fastest rate? What significance does this have? Where are Purkinje fibers located and what do they form?
1) Myocytes constituting the SA node contract spontaneously at the fastest rate; thus, the SA node is the cardiac pacemaker i.e., it determines the rate of myocardial contractility
2) Purkinje fibers are myocytes located in the ventricular endocardium. They form the left and right bundle branches of the conducting system
What are the three layers of the aortic wall? What constitutes the thick tunica media? When are the fibers of the tunica media distended? How does vascular blood flow continue during diastole?
1) The aortic wall consists of a tunica intima (endothelium and underlying connective tissue) abutting the lumen, a middle tunica media, and an outer tunica adventitia
2) Concentric laminae (layers) of elastic fibers constitute the thick tunica media. The fibers are distended during systole
3) Passive recoil of the fibers during diastole sustains vascular blood flow during ventricular relaxation
What does the tunica adventitia consist of? What does its wall thickness prohibit? What is a response to this?
1) The tunica adventitia consists of dense connective tissue containing distinct nutritive microvessels designated the vasa vasorum
2) Wall thickness prohibits sufficient O2 and nutrient diffusion from the lumen; thus, vasa vasorum supply the outer media and adventitia
Which tissue abnormality characterizes Marfan syndrome?
1) Marfan syndrome is an inherited connective tissue disorder caused by molecular defects in the FBN1 gene that encodes the glycoprotein fibrillin-1. This extracellular protein is a component of microfibrils,
which serve as scaffolds for elastic fiber deposition. Abnormal elastic tissues in the body mark the disease
2) Cardiovascular lesions, the most life-threatening, include mitral valve prolapse and weakening of the tunica media of the aorta, which may rupture spontaneously
3) Loss of connective tissue support in heart valves creates the so-called floppy valve that may contribute to heart failure
What is an aortic aneurysm and why does Marfan syndrome increase its susceptibility?
1) An aneurysm is an abnormal localized dilation in the weakened wall of an artery. An aortic aneurysm occurs when the diameter of part of the aorta increases by 50% or more. A true aneurysm is a large bulge in the wall that consists of all three tunics. Rupture may lead to fatal bleeding in only a few minutes
2) Infection, inflammation, syphilis, and the genetic connective tissue disorder Marfan syndrome weaken arterial walls, and chronic hypertension induces susceptibility to aneurysms because elevated arterial pressures place undue stress on vessel walls
Why is the abdominal aorta susceptible to dilation and aneurysm formation?
The abdominal aorta lacks vasa vasorum, which may explain its susceptibility to dilation and aneurysm formation
What do the pulmonary trunk and aorta do together?
The wall of pulmonary trunk resembles that of the aorta and together they accommodate the systolic surge and deliver blood to the vast population of pulmonary and systemic arteries
What characterizes the thick tunica adventitia of the SVC? What does tonic contraction of helical smooth muscle layers in the tunica media assist?
1) The thick tunica adventitia of the SVC contains bundles of type I collagen fibers and a dense vasa vasorum
2) Tonic contraction of helical smooth muscle layers in the tunica media assists the adventitial collagen fibers in restricting overdistension
What occupies the tunica adventitia of the IVC? What does their tonic contraction assist?
1) Bundles of longitudinal smooth muscle fibers uniquely occupy the tunica adventitia of the IVC
2) Their tonic contraction assists blood flow against gravity into the right atrium