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Flashcards in The Heart Deck (137):
0

Mass of heart

250 (female) to 300 (male) grams.

1

Mediastinum

Mass of connective tissue that cushions and protects the heart.

Extends from sternum --> vertebral column, diaphragm to first rib, and between the lungs.

2

Apex of heart

Tip of left ventricle. Rests on diaphragm.

Anterior, inferior and lateral to left

2/3 of mass of heart lies left of midline

3

Base of the heart

Formed by atria (mostly left).
Posterior, superior and to the right.
Where big vessels connect.

4

Sides of heart

Anterior -- deep to sternum and ribs

Inferior -- between apex and right border. Mostly on diaphragm

Right border -- faces right lung

Left border -- Pulmonary border. Faces left lung.

5

Pericardium.

Membrane that surrounds and protects heart.

Maintains position of heart but also allows movement.

6

2 parts of pericardium

Fibrous

Serous

7

Fibrous pericardium

Superficial of the two layers. Strong, dense, inelastic, irregular connective tissue.

Anchors heart in mediastinum
Prevents over stretching of heart.
Protection.

8

Serous pericardium

Deep layer of pericardium.
Thin. Contains two layers:

1. Parietal
2. Visceral

9

Parietal layer of pericardium

Outer layer
Fused to fibrous pericardium.

10

Visceral layer of pericardium

Inner layer
AKA epicardium

Considered the outermost layer of the heart. Adheres to surface of heart.

11

Pericardial Cavity

The space between parietal and visceral layers of the serous pericardium. Houses pericardial fluid.

12

Pericardial fluid.

In pericardial cavity

Viscous fluid that helps reduce friction between between layers during heart contractions.

13

What are the layers of the heart?

Epicardium
Myocardium
Endocardium

14

Epicardium

External layer of the heart
AKA visceral layer of serous pericardium
Makes heart smooth and slippery

15

Myocardium

Middle layer of heart
Cardiac muscle layer
Makes up 95% of heart
Responsible for pumping

16

Endocardium

Innermost layer of heart
Thin layer of endothelium overlying thin layer of connective tissue

Provides smooth lining for chambers of heart and covers the heart valve.

Continuous with endothelial lining of blood vessels attached to heart.

Minimizes friction of blood

17

What are the chambers of the heart?

Right and left atrium
Right and left ventricles

18

Atria

Two superior chambers of the heart

Receive blood.

Have auricles located on anterior surface

19

Auricles (cardiac)

On anterior surface of each atrium
Help increase capacity/volume of blood.

20

Ventricles

Inferior surfaces of heart
Pumping chambers

21

Sulci (cardiac)

Small grooves that hold coronary blood vessels and fat.

Mark the external boundaries between chambers of the heart.

22

Coronary sulcus

"the belt of the heart"

Encircles the heart and separates atrium from ventricles

23

Anterior interventricular sulcus

Separates the two ventricles on the anterior side.

24

Posterior inter ventricular sulcus

Separated the two ventricles on the posterior side

25

Septum

Internal
Fibrous connective tissue that separates chambers

Inter ventricular and inter atrial.

26

Right Atrium

Forms right border of the heart
Receives deoxygenated blood.

Smooth posterior wall
Anterior wall rough due to pectin ate muscle

Blood passes from right atrium to right ventricle through tricuspid valve

27

Blood vessels to right atrium

Superior vena cava -- from upper body
Inferior vena cava -- from abdomen, lower body
Coronary Sinus -- from heart

28

Pectinate muscles

Muscular ridges that extend into the auricle

Contributes to forceful arterial contraction.

29

Left atrium

Forms most of the base of the heart

Receives oxygenated blood from lungs from 4 pulmonary veins

Smooth posterior and anterior walls.
Auricle rough due to Pectinate muscles.

Blood passes to left ventricle through bicuspid/mitral valve.

30

Interatrial septum

Separated right and left atria.
Contains oval depression called fossa ovalis

31

Foramen ovale

Opening in interatrial septum of fetal heart. In adults closes and becomes fossa ovalis.

32

Right ventricle

Forms most of anterior surface if heart

Received deoxygenated blood from RA through tricuspid valve

Contain trabeculae carneae and chordae tendinae

Blood Passes through pulmonary valve (aka pulmonary semilunar valve)

33

Trabeculae carneae

Inside ventricles

Series of ridges formed
By raised bundles of cardiac muscle fibres
Some help with cardiac conduction

34

Chordae tendinae

In ventricles

Tendon-like cords that attach the cusps of the tricuspid and mitral valves to trabecular carneae called papillary muscles.

Help stabilize and strengthen the cusps and prevent them from everting during ventricular contraction.

35

Papillary muscles

Cone shaped trabecular carneae that the chordae tendinae attach to.

36

What does the pulmonary trunk split
Into?

Right and left pulmonary arteries

37

Left ventricle

Largest and strongest chamber
Has thickest myocardium and generates the most force during contraction
Forms apex of heart.

Also contains trabecular carneae and chordae tendinae

Blood passes through to ascending aorta through aortic valve.

38

Interventricular septum

Separate right and left ventricles

39

Ligamentum arteriosum

Connects aortic arch and pulmonary trunk.

Remnant of ductus arteriosus (temporary blood vessel that shunts blood from aortic arch and pulmonary trunk during fetal development)

40

Fibrous skeleton of the heart

Four connective tissue rings that surround the valves of the heart.

Prevent over stretching of valves

Point of insertion for bundle of cardiac muscle fibres.

Electrical insulator between atria and ventricles.

41

Myocarditis

Inflammation of the muscles of the heart

Usually due to viral infections, rheumatic fever, or chemical or pharmacological agents.

42

Endocarditis

Inflammation of the endocardium, usually due to bacterial infections.

Usually involve heart valves

43

Pericarditis

Inflammation of the pericardium

Wet or dry.

Most common is acute (dry). Symptoms can mimic heart attack. May involve pericardial friction rub.

Chronic (wet) -- gradual build up of pericardial fluid (effusion). May leave to cardiac tamponade.

44

Cardiac tamponade

Build up of fluid causes compression of heart.

45

Valve prolapse

Eversion of heart valves

46

What causes heart valves to open and close?

Pressure changes and chambers contract and relax.

47

Atrial-Ventricular Valves: open

When open, rounded ends of cusps project into ventricle. Papillary muscles relaxed. Chordae tendinae slack. Blood moves down pressure gradient from atrium to ventricle.

48

AV Valves: closed

Cusps up. Ventricles contracted.
Pressure if blood in ventricles drives cusps upward.
Papillary muscles contract, chordae tendinae tighten to prevent valve prolapse.

49

Semilunar valves

Separate ventricles from pulmonary artery (right) and aorta (left)

Composed of three crescent moon shaped cusps; free border of each cusp opens into lumen of artery.

Valves open when pressure in ventricle exceeds pressure in arteries.

50

What is the pressure required to open SL valves,

Diastolic. LV 80 mmHg.
RV 25-30 mmHg

51

Stenosis

Narrowing of heart valve that restricts blood flow. Can increase BP

52

Valve insufficiency or incompetence

Failure of valve to close completely.

53

Mitral Valve Prolapse

Failure of the mitral valve to close completely.

Allows backflow of blood from LV to LA.

Affects 30% of population

54

Rheumatic fever

Infectious disease that damages heart valves, most often left side.

Usually occurs after strep throat.

55

Cardio-Pulmonary Pathway

Aorta
Systemic arteries
Systemic arterioles
Systemic capillaries

Systemic venues
Systemic veins

Superior/inferior vena cava

Right atrium
(Tricuspid/right AV valve)
Right ventricle
(Pulmonary semilunar valve)

Pulmonary arteries
Pulmonary arterioles
Pulmonary capillaries

Pulmonary venules
Pulmonary veins

Left atrium
(Left AV/bicuspid/mitral) valve
Left ventricle
(Left/aortic semilunar valve)

56

What does the aorta feed?

Ascending -- coronary arteries
Aortic arch -- upper body
Descending aorta -- divides into thoracic and abdominal (which itself divides into common iliac arteries)

57

Cardiac circulation

Ascending aorta feeds right and left coronary arteries

Left coronary artery divides into: anterior intraventricular and circumflex branches

Right coronary artery supplies right atrium and then divides into posterior intraventricular branch and marginal branch.

Great cardiac vein, middle cardiac vein, small cardiac vein -- all empty into coronary sinus.

Anterior cardiac vein drains into RA.

58

Left coronary artery

Branches off ascending aorta

Passes inferior to left auricle and divides into anterior intraventricular branch (or Left Anterior Decending -- LAD) and circumflex branch.

59

Anterior intraventricular branch or LCA

AKA Left Anterior Descending

Supplies blood to both ventricles

60

Circumflex branch of LCA

Lies in coronary sulcus
Feed left atrium and left ventricle

61

Right coronary artery

Supplies right atrium

Continues inferior to right auricle and divides into posterior intraventricular branch and marginal branch.

62

Posterior intraventricular branch of RCA

Follows posterior intraventricular sulcus.

Feeds both ventricles

63

Marginal branch of RCA

Lies in coronary sulcus

Supplies right ventricle

64

Coronary sinus

Located in coronary sulcus

Received deoxygenated blood from myocardium (all veins except anterior cardiac) and empties into RA.

65

Great Cardiac Vein

Lies in anterior interventricular sulcus

Drains areas of heart supplied by LCA (RV, LV, LA)

Empties into coronary sinus


66

Middle Cardiac Vein

Lies in posterior interventricular sulcus

Drains areas of heart supplied by posterior interventricular branch of RCA (LV, RV)

67

Small cardiac vein

Lies in coronary sinus
Next to RCA
Drains RA and RV

Empties into coronary sinus

68

Anterior cardiac vein

Drains RV and opens directly into RA.

Next to marginal branch of RCA

69

Myocardial ischemIa

Lack of blood supply due to partial obstruction of vessel. Causes hypoxia

70

Angina pectoralis

Chest pain associated with myocardial ischemia

Neck, chin, left arm to elbow

71

Cardiac vs skeletal muscle tissue

Shorter
Less circular
Branching
One centrally located nucleus (usually)
Larger and more numerous mitochondria
Transverse tubules wider and less abundant.
Smaller sarcoplasmic reticulum
Involuntary
Intercalated discs (thickening of sarcolemma)

Same arrangements of actin and myosin, bands, zones, z discs

72

Intercalated discs

Irregular transverse thickening of sarcolemma

Connect neighbouring cardiac muscle fibres

Contain desmosome and Gap junctions

73

Role of desmosomes in cardiac tissue

Tight cell-to-cell junctions create stability.

Hold fibres together

74

Role of gap junctions in cardiac tissue

Tubular cell-to-cell junction that allow for transmission of substances and signals.

Allow muscle action potentials to conduct from one muscle fibre to its neighbour --> allows atria/ventricles to contract as a single coordinated unit.

75

What percentage of muscle fibres are autorhythmic?

1%

76

Two main characteristics of the cardiac conduction system

1 pacemaker
2 conduction system

77

Steps of cardiac conduction.

1. Firing of SA node (natural pacemaker)
2. AP conducts along atrial fibres, and reaches AV node in interatrial septum.
3. Signal propagates to AV bundle (Bundle of His)
3. Signal splits into left and right bundle branches that travel down interventricular septum
4. At apex of heart, conducted through Purkinjw fibres, which stimulate ventricular contraction.

78

Sinoatrial (SA) node

Natural pacemaker. Creates approx 100 AP/minute

Posterior wall of right atrium.

Signal propagates to LA via gap junctions. Both atria contract simultaneously.

79

What is the only site where APs can conduct from atria to ventricles?

Bundles of His (the AV bundle)

80

What happens at AV node?

Signal slows before relating to Bundle of His. This allows time for Atria to empty blood into ventricles.

81

What modifies the timing and strength of the heartbeat?

ANS impulses, blood borne hormones (epinephrine)

Do not affect rhythm!

82

Resting potential (cardiac)

Membrane potential of a resting, non contracting muscle cell

(-90mV)

83

Plateau phase

Period of sustained contraction due to simultaneous/concurrent release of calcium.

84

Stages of cardiac action potential

Resting potential
Depolarization
Plateau phase
Re polarization
Refractory period

85

Depolarization (cardiac)

Action potential increases to threshold

Voltage gated channels open
Na+ moves into cytosol. Rapid depolarization.

Signal to contract -- not actual contraction

86

Plateau.

Period of maintained depolarization.

Ca+ channels open and calcium comes in from SR.

Contraction triggered

87

Repolarization

K+ channels open and restore negative membrane potential

88

Refractory period (cardiac)

All stages except rest

89

Cardiac ATP production

Mostly aerobic

In heart attacks, cardiomyopathy causes Creatine kinase to spill into blood. Tested for after heart attack.

90

Electrocardiogram is used to determine:

If conduction pathway is abnormal

If heart is enlarged

If certain regions of the heart are damaged

Cause of chest pain.

91

Normal ECG

P Wave -- atrial depolarization
QRS Complex -- rapid ventricular depolarization (and thus contraction)
T Wave: ventricular repolarization.

92

P-Q interval

Atrial depolarization and contraction; AP travelling to Purkinje fibres.

Time can lengthen due to scar tissue

93

S-T interval

End of QRS to START of T wave
Plateau phase of depolarization of ventricles.

Elevated in acute MI, depressed with low O2

94

QT interval

Beginning of QRS to END of T Wave

Start of ventricular depolarization to end of ventricular repolarization.

Lengthened by myocardial damage, ischemia, conduction abnormalities.

95

Range for aortic pressure

80-120 mmHg

96

Range for LV pressure

0-120 mmHg

97

Atrial pressure is ________ than the ventricles, and the right side is always _______ than the left side.

Much less

Less

98

Atrial systole

Marked by P wave

SA node fires; both atria contract.
Atrial pressure increases; ventricular pressure low.

Blood ejected through AV valves (tricuspid and mitral) into ventricles.

AP propagates down through bundle of His into Purkinje fibres.

Atria relax and atrial pressure drops.

99

End diastolic volume

The amount of blood in the ventricles at the end of atrial systole/ventricular diastole.

105ml + 25ml (from atria) = 130ml

Determined by: 1. Duration of ventricular diastole. 2. Venous return.

100

Ventricular systole

Begins part way through QRS (just after R)

As pressure in ventricles rise, AV valves shut.

Semilunar valves open. Ejection lasts about .25 second. About 70ml ejected.

T wave marks onset of ventricular repolarization.

101

Isovolumetric Contraction

In ventricles, the 0.05 seconds when both AV and semilunar valves are shut.

Muscles exerting force and contracting but not shortening.

Also occurs during relaxation phase.

102

Pressure required to open semilunar valves

LV 80 mmHg (continues to rise to 120 mmHg)

RV 20 mmHg (rises to 25-30 mmHg)

103

End systolic volume

The volume of blood remaining in each ventricle at the end of systole. About 60 ml.

104

Stroke volume

The amount of blood ejected per beat

SV = EDV - ESV

At rest: SV = 130 - 60 = 70 ml.

105

Dicrotic wave

The sound blood makes when it bounces off closed valves.

lub (AV) dub (semilunar)

(Aortic valve closes around 100 mmHg)

106

When do AV valves open?

When ventricular pressure drops below atrial pressure. Passive ventricular filling before atrial contractions = 105 ml

107

What are the two heart sounds inaudible by stethoscope?

S3 & S4 --blood turbulence during ventricular filling and atrial contraction (Systole).

108

Heart Murmur

Any abnormal sound heard during, before or after normal heart sounds.

Common in kids; in adults may indicate a valve stenosis or other disorder.

109

Cardiac output

Blood ejected/minute

Stroke volume x BPM.

Average SV = 70ml
Average BPM = 75
Average CO = 5250 ml/min

110

Cardiac reserve

The difference between max CO and resting CO

Average 4-5x
Greater in athletes; almost none in severe asthmatics and people with heart disease.

111

Three main factors that regulate stroke volume

Preload
Contractibility
Afterload

112

Preload

The degree of stretch on the heart before contraction

More blood enters ventricles, greater the stretch, more powerful the contraction.

113

Frank-Starling Law

Preload volume is proportional to the EDV.
--> equal pumping of blood between ventricles.

114

Contractability

Strength of contraction of muscle fibres.

115

Inotropic agents

Positive -- increase contraction (sympathetic NS, digitalis, anything that increases Ca)

Negative -- decreases contraction (parasympathetics, anoxia, Ca blockers)

116

Congestive heart failure

Loss of pumping efficiency

Increased EDV (preload) --> contracts less forcefully --> increases EDc

LV. Pulmonary Edema
RV peripheral edema.

117

Most important regulators of HR

ANS (medulla oblongata) and hormones released by adrenal medulla.

118

Medulla oblongata and HR

Receives sensory input from baro, chemo and proprioceptors.

Sympathetic signals sent through cardiac accelerator nerves in T-spine region

Parasympathetic signals sent through vagus nerve (CN X)

119

Chemical factors affecting HR

Reduction: hypoxia, acidosis, alkalosis, K+ (block AP), Na+

Increase: calcium, (nor)epinephrine, thyroid hormones

120

Arrythmias (dysrhythmias)

Abnormal heart rhythm due to defect in conduction system.

Asynchronous contraction --> abnormal blood pumping.

121

Coronary Artery Disease

Results from accumulation of artherosclerotic plaque in coronary arteries.

122

Artherosclerosis

One form of arteriosclerosis (thickening of arterial walls and loss of elasticity) Formation of lesions (artherosclerotic plaques, made of cholesterol/fat) in arteries.

123

CAD surgical treatment

Coronary artery bypass grafting (CABG)

Percutaneous Transluminal Coronary Angioplasty. (PTCA) 30-40% failure within 6 months without stent.

124

Coarctation of aorta

Congenital narrowing of aorta

125

Patent ductus arteriosus

Ductus arteriosus doesn't close at birth. Aortic blood flows into pulmonary trunk, increasing load on ventricles.

126

Septal defect

Atrial -- foramen ovale fails to close

Ventricle -- incomplete development of septum. Oxygenated and deoxygenated blood mix.

127

Tetralogy of Fallot

Combination of:
Intraventricular septal defect
Dextrapositioned aorta
Stenosed pulmonary valve
Hypertrophied right ventricle

128

Cardiac arrest

Cessation of effective heartbeat

129

Cardiomegaly

Enlarged heart

130

Cor Pulmonale (CP)

RV hypertrophy secondary to lung condition.

131

Paroxysmal tachycardia

Tachycardia with sudden onset and end.

132

When does the heart begin to develop?

From mesoderm on day 18/19

Most development occurs between W5-9

133

Afterload

The pressure required to open SL valves

Left (aortic) 80mmHg
Right (pulmonary) 20 mmHg

134

Depolarization

Voltage gates Na+ gates open

Na+ rushes in --> rapid depolarization

135

Plateau

Period of maintained depolarization

Opening of voltage gated Ca+ channels in sarcolemma

Triggers contraction

Slow outbound leak of K+

136

Repolarization

Recovery of resting membrane potential (-90 mV).

More K+ channels open. Outflow of K+ restores resting potential.