CV System Structure Flashcards
describe 2 primary roles of the CV system
- distribution of essential substances to the tissues (dissolved gases, molecules for nutrition, growth, repair)
- removal of by products of metabolism
describe 3 secondary roles of the CV system
- circulation of hormones and neurotransmitters that allow for chemical signaling among cells (humoral communication)
- heat dissipation: by transfer from core to body surface
- mediation of defense responses against invading microorganisms (immunity!)
what are the 2 pumps of the heart? how are they arranged?
- right heart: propels oxygen-poor blood through the lungs (pulmonary circulation)
- left heart: propels oxygen-rich blood to all other tissues (systemic/peripheral circulation)
these pumps are arranged end to end or in series
describe flow of blood through the heart (direction)
unidirectional thanks to the presence of one way valves
describe cardiac output generation
pulsatile; with each heartbeat the ventricles generate pressure pulses that drive blood through a system of tubes (vascular system)
what is found on each side of the heart?
- a thin walled atrium (the receiving chamber and primer pump)
- a thick walled ventricle (main pumping chamber)
list and describe the 2 cells of the heart
- contractile cells: atrial and ventricular myocytes; the work horses and majority of heart cells
- myoconductive cells: in nodal and purkinji fibers; specialized excitatory/conductive cells that spontaneously generate or conduct electrical signals through the heart so that it beats rhythmically; contain only a few contractile elements so contract weakly
describe arrangement of cardiac muscle (3)
- arranged in a lattice that behaves LIKE a syncytium
- cells are short, branches, and interconnected
- connected by intercalated discs
describe intercalated discs (2)
- connect cardiac cells end to end; specialized junctions that fuse neighboring cells via
- desmosomes: provide physical connection/mechanical coupling
- gap junctions: provide electrical connection/coupling
what doesn’t work in dilated cardiomyopathy?
desmosomes of intercalated discs
why is interconnectedness of myocytes important?
myocytes can be activated almost instantaneously by a wave of electrical stimulation and contract as one to generate a coordinated heartbeat
what is syncytium? are cardiac fibers a true anatomical syncytium?
a syncytium is a single, large, multinucleated cell formed from many fused cells; cardiac muscle is not a true syncytium because the cells are separated by sarcolemma; so considered a functional syncytium instead
what are the 2 functional syncytia of the heart?
atrial syncytium: right and left atria
ventricular syncytium: right and left ventricles
what physically and electrically separates atrial and ventricular muscle?
a fibrous skeleton
describe the fibrous skeleton of the heart (3)
- a tough CT sheet that encircles the valves
- lies along the plane of the atrioventricular/coronary groove
- blocks electrical communication between atria and ventricles except at AV bundle/bindle of His
what does the electrical insulation of the fibrous skeleton of the heart allow for?
electrical insulation allows atrial and ventricular syncytia to be activated separately and sequentially with a time delay between
what are the 2 one-way valves of the right side of the heart?
- tricuspid/right AV valve
- pulmonary/pulmonic/right semilunar valve
what are the 2 one-way valves of the left side of the heart?
- mitral/left AV/bicuspid valve
- aortic/left semilunar valve
what separates the right and left sides of the heart?
two septa:
interventricular septum
interarterial septum
at what locations of the heart do NO valves exist?
- between the cranial and caudal vena cavae and the right atrium
- between the pulmonary veins (4-6 of them) and the left atrium
define the cardiac valves
thin flaps of flexible endothelium-covered fibrous tissue that open and close to maintain unidirectional blood flow
is valve motion passive or active? explain
passive: moved by pressure exerted by flowing blood
what is closure of heart valves associated with?
events that produce the typical heart sounds heard by stethoscope
describe the AV valves
separate each atrium from its corresponding ventricle
describe the position of the AV valves during the cardiac cycle
open when ventricles relax (filling phase) to allow blood to drop from atria into ventricle
close when ventricles contract (ejection phase) to prevent backflow/regurgitation of blood into atria
what are chordae tendinaea?
CT strands that tether edges of the sheet-like AV valves to the ventricular papillary muscles below
describe chordae tendinaea during the ejection phase of the cardiac cycle
papillary muscles contract, tensing the chordae tendinaea to prevent valve eversion and backflow of blood
describe the semilunar valves (2)
- separate each ventricle from its corresponding great artery (LV/aorta, RV/pulmonary artery)
- comprised of 3 cuplike cusps attached to a circumferential fibrous ring (valve annulus)
describe the position of the semilunar valves during the cardiac cycle
open when ventricles contract (ejection phase) to allow blood to exit ventricle
close when ventricles relax (filling phase) to prevent backflow (regurgitation) of blood into ventricle
describe coronary arteries (4)
- arise from outpockets (sinuses of Valsalva) in aortic root behind aortic valve cusps
- branch over the heart’s outer surface (epicardium)
- carry oxygen-rich blood to myocardium
- epicardial arteries penetrate the heart wall to reach endocardium
describe coronary veins (3)
- blood moves from capillaries into coronary veins
- coronary veins coalesce to form the coronary sinus
- coronary sinus delivers oxygen-poor blood back to the right atrium
how does the heart feed itself?
coronary circulation
describe the path of blood flow through the heart (5)
- oxygen-poor blood enters the right atrium from cranial and caudal vena cavae and coronary sinus
- blood crosses the tricuspid valves to enter the right ventricle, which pumps it across the pulmonary valve and into pulmonary circulation through the pulmonary artery
- in the pulmonary capillaries, gas exchange occurs
- oxygen-rich blood returns to the left atrium through the pulmonary veins
- blood crosses the mitral valve to enter the left ventricle, which pumps it across the aortic valve and into systemic and coronary circulations via the aorta
what are the 5 components and functions of the cardiovascular tree?
- arteries: distribute blood from heart under high pressure
- arterioles/small arteries: smooth down the arterial pulsations and regulate blood flow into capillaries
- capillaries: exchange gases between blood and systemic tissues
- venules: collect blood from capillaries
- veins: deliver blood back to heart and serve as major reservoir for blood (have a blood pool, will squeeze back to heart when blood pressure drops to push back to circulation
how is continuous, low pressure flow to capillaries made possible? (2)
- aorta and large arteries are compliant and elastic, allow for distension to absorb energy when ventricle contracts and recoil to maintain propulsion when ventricle is not contracting
- small arteries and arterioles provide resistance to blood flow, causing a pressure-lowering effect
what happens to vessel lumen, wall compliance, and elasticity as you move down the vascular tree?
- vessel lumen gets smaller as smooth muscle increases
- vessel wall compliance and elasticity decreases as elastic fibers and collagen decrease
