CV System Structure

Question 1

describe 2 primary roles of the CV system

Answer 1

1. distribution of essential substances to the tissues (dissolved gases, molecules for nutrition, growth, repair)
2. removal of by products of metabolism

Question 2

describe 3 secondary roles of the CV system

Answer 2

1. circulation of hormones and neurotransmitters that allow for chemical signaling among cells (humoral communication)
2. heat dissipation: by transfer from core to body surface
3. mediation of defense responses against invading microorganisms (immunity!)

Question 3

what are the 2 pumps of the heart? how are they arranged?

Answer 3

1. right heart: propels oxygen-poor blood through the lungs (pulmonary circulation)
2. left heart: propels oxygen-rich blood to all other tissues (systemic/peripheral circulation)
   these pumps are arranged end to end or in series

Question 4

describe flow of blood through the heart (direction)

Answer 4

unidirectional thanks to the presence of one way valves

Question 5

describe cardiac output generation

Answer 5

pulsatile; with each heartbeat the ventricles generate pressure pulses that drive blood through a system of tubes (vascular system)

Question 6

what is found on each side of the heart?

Answer 6

1. a thin walled atrium (the receiving chamber and primer pump)
2. a thick walled ventricle (main pumping chamber)

Question 7

list and describe the 2 cells of the heart

Answer 7

1. contractile cells: atrial and ventricular myocytes; the work horses and majority of heart cells
2. 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

Question 8

describe arrangement of cardiac muscle (3)

Answer 8

1. arranged in a lattice that behaves LIKE a syncytium
2. cells are short, branches, and interconnected
3. connected by intercalated discs

Question 9

describe intercalated discs (2)

Answer 9

1. connect cardiac cells end to end; specialized junctions that fuse neighboring cells via
2. desmosomes: provide physical connection/mechanical coupling
3. gap junctions: provide electrical connection/coupling

Question 10

what doesn’t work in dilated cardiomyopathy?

Answer 10

desmosomes of intercalated discs

Question 11

why is interconnectedness of myocytes important?

Answer 11

myocytes can be activated almost instantaneously by a wave of electrical stimulation and contract as one to generate a coordinated heartbeat

Question 12

what is syncytium? are cardiac fibers a true anatomical syncytium?

Answer 12

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

Question 13

what are the 2 functional syncytia of the heart?

Answer 13

atrial syncytium: right and left atria
ventricular syncytium: right and left ventricles

Question 14

what physically and electrically separates atrial and ventricular muscle?

Answer 14

a fibrous skeleton

Question 15

describe the fibrous skeleton of the heart (3)

Answer 15

1. a tough CT sheet that encircles the valves
2. lies along the plane of the atrioventricular/coronary groove
3. blocks electrical communication between atria and ventricles except at AV bundle/bindle of His

Question 16

what does the electrical insulation of the fibrous skeleton of the heart allow for?

Answer 16

electrical insulation allows atrial and ventricular syncytia to be activated separately and sequentially with a time delay between

Question 17

what are the 2 one-way valves of the right side of the heart?

Answer 17

1. tricuspid/right AV valve
2. pulmonary/pulmonic/right semilunar valve

Question 18

what are the 2 one-way valves of the left side of the heart?

Answer 18

1. mitral/left AV/bicuspid valve
2. aortic/left semilunar valve

Question 19

what separates the right and left sides of the heart?

Answer 19

two septa:
interventricular septum
interarterial septum

Question 20

at what locations of the heart do NO valves exist?

Answer 20

1. between the cranial and caudal vena cavae and the right atrium
2. between the pulmonary veins (4-6 of them) and the left atrium

Question 21

define the cardiac valves

Answer 21

thin flaps of flexible endothelium-covered fibrous tissue that open and close to maintain unidirectional blood flow

Question 22

is valve motion passive or active? explain

Answer 22

passive: moved by pressure exerted by flowing blood

Question 23

what is closure of heart valves associated with?

Answer 23

events that produce the typical heart sounds heard by stethoscope

Question 24

describe the AV valves

Answer 24

separate each atrium from its corresponding ventricle

Question 25

describe the position of the AV valves during the cardiac cycle

Answer 25

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

Question 26

what are chordae tendinaea?

Answer 26

CT strands that tether edges of the sheet-like AV valves to the ventricular papillary muscles below

Question 27

describe chordae tendinaea during the ejection phase of the cardiac cycle

Answer 27

papillary muscles contract, tensing the chordae tendinaea to prevent valve eversion and backflow of blood

Question 28

describe the semilunar valves (2)

Answer 28

1. separate each ventricle from its corresponding great artery (LV/aorta, RV/pulmonary artery) 2. comprised of 3 cuplike cusps attached to a circumferential fibrous ring (valve annulus)

Question 29

describe the position of the semilunar valves during the cardiac cycle

Answer 29

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

Question 30

describe coronary arteries (4)

Answer 30

1. arise from outpockets (sinuses of Valsalva) in aortic root behind aortic valve cusps 2. branch over the heart's outer surface (epicardium) 3. carry oxygen-rich blood to myocardium 4. epicardial arteries penetrate the heart wall to reach endocardium

Question 31

describe coronary veins (3)

Answer 31

1. blood moves from capillaries into coronary veins 2. coronary veins coalesce to form the coronary sinus 3. coronary sinus delivers oxygen-poor blood back to the right atrium

Question 32

how does the heart feed itself?

Answer 32

coronary circulation

Question 33

describe the path of blood flow through the heart (5)

Answer 33

1. oxygen-poor blood enters the right atrium from cranial and caudal vena cavae and coronary sinus 2. 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 3. in the pulmonary capillaries, gas exchange occurs 4. oxygen-rich blood returns to the left atrium through the pulmonary veins 5. 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

Question 34

what are the 5 components and functions of the cardiovascular tree?

Answer 34

1. arteries: distribute blood from heart under high pressure 2. arterioles/small arteries: smooth down the arterial pulsations and regulate blood flow into capillaries 3. capillaries: exchange gases between blood and systemic tissues 4. venules: collect blood from capillaries 5. 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

Question 35

how is continuous, low pressure flow to capillaries made possible? (2)

Answer 35

1. 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 2. small arteries and arterioles provide resistance to blood flow, causing a pressure-lowering effect

Question 36

what happens to vessel lumen, wall compliance, and elasticity as you move down the vascular tree?

Answer 36

1. vessel lumen gets smaller as smooth muscle increases 2. vessel wall compliance and elasticity decreases as elastic fibers and collagen decrease