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A&P - Study Sets > Chapter 18 > Flashcards

Chapter 18 Flashcards

1
Q

The Systemic and Pulmonary Circuits

A

Pulmonary circulation moves blood between the heart and the lungs

Systemic circulation moves blood between the heart and the rest of the body

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2
Q

Heart valves

A

Ensure unidirectional blood flow through heart

Open and close in response to pressure changes

Two major types of valves:

  • Atrioventricular valves located between atria and ventricles
  • Semilunar valves located between ventricles and major arteries
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3
Q

Atrioventricular (AV) Valves

A

Two atrioventricular (AV) valves prevent backflow into atria when ventricles contract

Tricuspid valve (right AV valve): made up of three cusps and lies between right atria and ventricle

Mitral valve (left AV valve, bicuspid valve): made up of two cusps and lies between left atria and ventricle

Chordae tendineae: anchor cusps of AV valves to papillary muscles that function to:

  • Hold valve flaps in closed position
  • Prevent flaps from everting back into atria
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4
Q

The Function of the Atrioventricular (AV) Valves (opened)

A

AV valves open, atrial pressure greater than ventricular pressure

  1. ) blood returning to the heart fills atria, pressing against the AV valves. the increased pressure forces AV valves open
  2. ) as ventricles fill, AV valve flaps hang limply into ventricles
  3. ) atria contract, forcing additional blood into ventricles
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5
Q

The Function of the Atrioventricular (AV) Valves (closed)

A

AV valves closed, atrial pressure less than ventricular pressure

  1. ) ventricles contract, forcing blood against AV valve cusps
  2. ) AV valves close
  3. ) papillary muscles contract and chordae tendineae tighten, preventing valve flaps from everting into atria
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6
Q

Semilunar (SL) Valves

A

Two semilunar (SL) valves prevent backflow from major arteries back into ventricles

  • Open and close in response to pressure changes
  • Each valve consists of three cusps that roughly resemble a half moon

Pulmonary semilunar valve: located between right ventricle and pulmonary trunk

Aortic semilunar valve: located between left ventricle and aorta

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7
Q

The Function of the Semilunar (SL) Valves (opened)

A

as ventricles contract and intraventricular pressure rises, blood is pushed up against semilunar valves, forcing them to open

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8
Q

The Function of the Semilunar (SL) Valves (closed)

A

as ventricles contract and intraventricular pressure falls, blood flows back from arteries, filling the cusps of semilunar valves and forcing them to close

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9
Q

Heart Sounds

A

Two sounds (lub-dup) associated with closing of heart valves

  • First sound is closing of AV valves at beginning of ventricular systole
  • Second sound is closing of SL valves at beginning of ventricular diastole
  • Pause between lub-dups indicates heart relaxation
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10
Q

Areas of the thoracic surface where the sounds of individual valves are heard most clearly…

A

Aortic valve sounds
heard in 2nd intercostal
space at right sternal
margin

Pulmonary valve
sounds heard in 2nd
intercostal space at left
sternal margin

Mitral valve sounds
heard over heart apex
(in 5th intercostal space)
in line with middle of
clavicle

Tricuspid valve sounds
typically heard in right
sternal margin of 5th
intercostal space

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11
Q

Heart murmurs

A

abnormal heart sounds heard when blood hits obstructions

Incompetent valve

  • Blood backflows so heart repumps same blood over and over
  • Causes swishing sound as blood regurgitates backward

Valvular stenosis

  • Stiff flaps that constrict opening, restricting blood flow
  • Heart needs to exert more force to pump blood
  • Causes high-pitched sound or clicking as blood is forced through narrow valve

Defective valve can be replaced with mechanical, animal, or cadaver valve

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12
Q

Pathway of Blood Through Heart: Right side of the heart

A 
Superior vena cava (SVC), inferior vena cava (IVC), and coronary sinus →
Right atrium →
Tricuspid valve → 
Right ventricle →
Pulmonary semilunar valve →
Pulmonary trunk →
Pulmonary arteries →
Lungs
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13
Q

Pathway of Blood Through Heart: Left side of the heart

A 
Four pulmonary veins →
Left atrium →
Mitral valve → 
Left ventricle →
Aortic semilunar valve →
Aorta →
Systemic circulation
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14
Q

The Pulmonary and Systemic Circuits: Heart is a transport system consisting of two side-by-side pumps…

A

Right side receives oxygen-poor blood from tissues
- Pumps blood to lungs to get rid of CO2, pick up O2, via pulmonary circuit

Left side receives oxygenated blood from lungs
- Pumps blood to body tissues via systemic circuit

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15
Q

Receiving chambers of heart

A

Right atrium: Receives blood returning from systemic circuit

Left atrium: Receives blood returning from pulmonary circuit

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16
Q

Pumping chambers of heart

A

Right ventricle: Pumps blood through pulmonary circuit

Left ventricle: Pumps blood through systemic circuit

17
Q

The Heart is a Double Pump, Each Side Supplying…

A

its Own Circuit

18
Q

Pathway of Blood Through Heart…

A
  • Equal volumes of blood are pumped to pulmonary and systemic circuits
  • Pulmonary circuit is short, low-pressure circulation
  • Systemic circuit is long, high-friction circulation

Anatomy of ventricles reflects differences

  • Left ventricle walls are 3× thicker than right
  • Pumps with greater pressure
19
Q

Anatomical Differences Between the Right and Left Ventricles

A

Right ventricle: thinner wall than left ventricle, crescent shape, wraps around left ventricle

Left ventricle: thicker wall than right ventricle, round shape

20
Q

Coronary circulation

A
  • Functional blood supply to heart muscle itself
  • Shortest circulation in body
  • Delivered when heart is relaxed
  • Left ventricle receives most of coronary blood supply
21
Q

Coronary arteries

A
  • Both left and right coronary arteries arise from base of aorta and supply arterial blood to heart
  • Branching of coronary arteries varies among individuals
  • Arteries contain many anastomoses (junctions)
  • Provide additional routes for blood delivery
  • Cannot compensate for coronary artery occlusion
  • Heart receives 1/20th of body’s blood supply
22
Q

Angina pectoris (chest/thoracic pain)

A

Thoracic pain caused by fleeting deficiency in blood delivery to myocardium

Myocardium is weakened

23
Q

Myocardial infarction (heart attack)

A

Prolonged coronary blockage

Areas of cell death are repaired with noncontractile scar tissue (fibrosis)

Damage to left ventricle most dangerous.

24
Q

Microscopic Anatomy: Cardiac Muscle Fibers

A

Cardiac muscle cells: striated, short, branched, fat, interconnected

  • One central nucleus (at most, 2 nuclei)
  • Contain numerous large mitochondria (25–35% of cell volume) that afford resistance to fatigue
25
Q

Intercalated discs are connecting junctions between…

A

cardiac cells that contain:

Desmosomes: hold cells together; prevent cells from separating during contraction

Gap junctions: allow ions to pass from cell to cell; electrically couple adjacent cells

  • Allows heart to be a functional syncytium, a single coordinated unit
26
Q

Intercellular space between cells has …

A

connective tissue matrix (endomysium)

Contains numerous capillaries

Connects cardiac muscle to cardiac skeleton, giving cells something to pull against

27
Q

Similarities with skeletal muscle

A

Muscle contraction is preceded by depolarizing action potential

Depolarization wave travels down T tubules; causes sarcoplasmic reticulum (SR) to release Ca2+

Excitation-contraction coupling occurs
- Ca2+ binds troponin causing filaments to slide

28
Q

Differences between cardiac and skeletal muscle

A

Some cardiac muscle cells are self-excitable

Two kinds of myocytes

  • Contractile cells: responsible for contraction
  • Pacemaker cells: noncontractile cells that spontaneously depolarize

Initiate depolarization of entire heart

Do not need nervous system stimulation, in contrast to skeletal muscle fibers

29
Q

Heart contracts as a unit…

A

All cardiomyocytes contract as unit (functional syncytium), or none contract

Contraction of all cardiac myocytes ensures effective pumping action

Skeletal muscles contract independently

30
Q

Influx of Ca2+ from extracellular fluid triggers Ca2+ release from SR (calcium-induced calcium release) …

A

Depolarization allows influx of extracellular Ca2+ which then causes SR to release its intracellular Ca2+

Skeletal muscles do not use extracellular Ca2+

31
Q

Tetanic contractions cannot occur in cardiac muscles…

A

Cardiac muscle fibers have longer absolute refractory period than skeletal muscle fibers

Absolute refractory period is almost as long as contraction itself

Prevents tetanic contractions

Allows heart to relax and fill as needed to be an efficient pump

32
Q

The heart relies almost exclusively on aerobic respiration…

A

Cardiac muscle has more mitochondria than skeletal muscle so has greater dependence on oxygen

Cannot function without oxygen

A&P - Study Sets (3 decks)

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