The Heart Flashcards
(176 cards)
1
Q
Function of cardiovascular system
A
To distribute oxygen and nutrients to the cells of the body, and to take away carbon dioxide and other wastes
2
Q
Pulmonary circuit
A
Carries blood to and from the gas exchange surfaces of the lungs
3
Q
Systemic circuit
A
Transports blood to and from the rest of the body
4
Q
Flow of the pulmonary circuit
A
Carries oxygen-poor blood from the right ventricle, through the pulmonary arteries, to the lungs
Carries oxygen-rich blood back through the pulmonary veins to the left atrium
5
Q
Flow of the systemic circuit
A
Carries oxygen-rich blood from the left ventricle, through the systemic arteries
Carries oxygen-poor blood through systemic veins back to the right atrium
6
Q
Arteries
A
Carry blood away from the heart
7
Q
Veins
A
Return blood to the heart
8
Q
Great vessels
A
Largest veins and arteries in the body
9
Q
Capillaries
A
Interconnect smallest arteries and smallest veins
10
Q
Why do capillaries have thin walls?
A
To allow gas exchange and exchange of wastes between blood and surrounding tissues
11
Q
Right atrium
A
Receives blood from systemic circuit and passes it to the right ventricle
12
Q
Right ventricle
A
Receives blood from right atrium and passes it to pulmonary circuit
13
Q
Left atrium
A
Receives blood from pulmonary circuit and passes it into the left ventricle
14
Q
Left ventricle
A
Receives blood from left atrium and passes it into systemic circuit
15
Q
Which chambers contract first?
A
Atria
16
Q
Where is the heart located?
A
In the thoracic cavity near the anterior chest wall, directly posterior to the sternum
17
Q
Where are the great vessels connected to?
A
The superior end of the heart at its base
18
Q
In a midsagittal section, where does the base lie?
A
Slightly to the left of the midline
19
Q
Does the heart sit in the anterior or posterior portion of the mediastinum?
A
Anterior
20
Q
What does the mediastinum contain?
A
Great vessels, thymus, oesophagus, and trachea
21
Q
Apex
A
Pointed tip of the heart
22
Q
Endocardium
A
- Covers inner surface of heart (inc. heart valves)
- Simple squamous epithelium continuous with endothelial lining of blood vessels
- Underlying areolar tissue
23
Q
Myocardium
A
- Middle layer
- Spiral bundles of cardiac muscle cells
24
Q
Pericardium
A
Fibrous pericardium (dense network of collagen fibres that stabilise the position of the heart and vessels within the mediastinum) and serous pericardium
25
Serous pericardium
- Parietal layer
| - Visceral layer (epicardium) - covers surface of heart
26
What separates the parietal and visceral layer of the serous pericardium?
Potential, fluid-filled pericardial cavity
27
Functions of the cardiac skeleton
- Anchors muscle fibres
- Supports the great vessels and heart valves
- Limits the spread of action potentials
28
How much pericardial fluid does the pericardial cavity normally contain?
15-50mL
29
What secretes pericardial fluid?
Pericardial membranes
30
Function of pericardial fluid
Acts as lubricant, reducing fiction between the opposing visceral and parietal surface as the heart beats
31
Pericarditis
Condition produced by pathogens that causes inflamed pericardial surfaces to rub against one another
32
Cardiac tamponade
Fluid collection in the pericardial cavity caused by increased production of pericardial fluid as a result of inflammation or traumatic injuries e.g. stab wounds
33
Auricle
The atriums ability to deflate and become a lumpy, wrinkled flap when not filled with blood
34
Coronary sulcus
A deep groove that marks the border between the atria and the ventricles
35
Inteventricular sulcus
- Shallow depressions that mark the boundary between the left and right ventricles
- Posterior and anterior
36
Name a characteristic of the coronary and inteventricular sulci
Substantial amounts of fat and arteries and veins that carry blood to and from the cardiac muscle
37
Visceral layer of serous pericardium (epicardium)
Consists of an:
- Exposed mesothelium
- Underlying layer of areolar connective tissue
38
Parietal layer of serous pericardium
Consists of an:
- Outer dense, fibrous layer
- Areolar layer
- Inner mesothelium
39
What are the arteries and ventricles made of?
Myocardium
40
Atrial myocardium
Contains muscle bundles that wrap around the atria and form figure eights that encircle the great vessels
41
What wraps around the ventricles?
Superficial ventricular muscles and deeper muscle layers spiral around and between the ventricles toward the apex in a figure eight pattern
42
What is each cardiac muscle cell wrapped in?
A strong but elastic sheath
43
What connects adjacent cardiac muscle cells?
Fibrous cross-links called struts
44
What separates the superficial and deep muscle layers?
Interwoven sheets of struts
45
Functions of the connective tissue fibres
1. Provide physical support for the cardiac muscle fibres, blood vessels, and nerves of the myocardium
2. Help distribute forces of contraction
3. Add strength and prevent overexpansion of the heart
4. Provide elasticity that helps return heart to its original size and shape after a contraction
46
Cardiac skeleton
Four dense bands of tough elastic tissue that encircle the heart valves and bases of the pulmonary trunk and aorta
47
Interatrial septum
Separates atria
48
Interventricular septum
Separates ventricles
49
Is the interatrial or interventricular septum thicker?
Interventricular septum
50
Atrioventricular (AV) valves
- Tricuspid and mitral
- Folds of fibrous tissue that extend into the openings between the atria and ventricles
- Permit blood flow only in one direction: atria to ventricles
51
Semilunar valves
- Pulmonary and aortic
- Between ventricles and their great vessels
- Ensures blood flow through the vessels
52
Superior vena cava
- Opens into the posterior and superior portions of the right atrium
- Delivers blood to right atrium from head, neck, upper limbs and chest
53
Inferior vena cava
- Opens into the posterior and inferior portion of the right atrium
- Carries blood to the right atrium from the rest of the trunk, the viscera, and the lower limbs
54
Are there valves between the venae cavae and the right atrium?
No
55
Foramen ovale
- From 5th week of embryonic development to birth
- Penetrates the interatrial septum and connects the two atria of the fetal heart
- Permits blood flow from right atrium to left atrium while lungs are developing
56
Fossa ovalis
A small, shallow depression that remains after the foramen ovale closes up
57
What is the surface of the posterior walls of the right atrium and the interatrial septum like?
Smooth
58
What is on the the surface of the anterior atrial wall and the inner surface of the auricle?
Prominent muscular ridges called pectinate muscles
59
Tricuspid valve
Contain three fibrous flaps called cusps
60
Chordae tendineae
Connective tissue fibres that attach to the free edge of each cusp in the tricuspid valve
61
Papillary muscles
- Conical muscular projections that arise from the inner surface of the right ventricle
- Chordae tednineae originate at the papillary muscles
62
What is on the surface of the ventricles?
Muscular ridges called trabeculae carnae
63
Moderator band
Muscular ridge that extends horizontally from the inferior portion of the interventricular septum and connects to the anterior papillary muscle
64
Conus arteriosus
Cone-shaped pouch that ends at the pulmonary valve
65
Pulmonary valve
Contains three semilunar cups of thick connective tissue
66
Pulmonary trunk
Receives blood from right ventricle and passes it on to left pulmonary arteries and the right pulmonary arteries
67
What forms the four pulmonary veins?
Small veins that unite
68
Where does the posterior wall of the left atrium receive blood from?
Two left and two right pulmonary veins
69
Is there a valve between the pulmonary veins and the left atrium?
No, but there's an auricle
70
What guards the entrance to the left ventricle?
Mitral valve
71
How many cusps does the mitral valve have?
Two
72
Where does the mitral valve permit blood flow to?
From the left atrium into the left ventricle
73
What does the right ventricle have that the left ventricle doesn't?
Moderator band
74
Aortic valve
Receives blood from the left ventricle and passes it to the ascending aorta
75
Aortic sinuses
Saclike expansions of the base of the ascending aorta that prevent individual cusps of the aortic valve from sticking to the wall of the aorta
76
Ascending aorta
Receives blood from the aortic valve and passes it to the aortic arch
77
Aortic arch
Receives blood from the ascending aorta and passes it to the descending aorta
78
Ligamentum arteriosum
A fibrous band that attaches the pulmonary trunk to the aortic arch
79
Which ventricle is larger?
The left ventricle
80
Why is the left ventricle larger?
It has thicker walls that allow it to push blood through the systemic circuit
81
Descending aorta
Receives blood from aortic arch
82
Function of the atria
To collect blood that is returning to the heart and convey it to the ventricles
83
What happens when the left ventricle contracts?
It shortens and narrows and bulges into the right ventricular cavity
84
Interaction between AV valves, chordae tendinae and papillary muscles
Ventricles = relaxed: chordae tendineae are loose, AV valves offer no resistance as blood flows from A to V
Ventricles = contracted: blood moving back towards atria swings the cusps together, papillary muscles tense chordae tendineae which stops cusps swinging into the atria
85
Regurgitation
Backflow of blood into the atria caused by cut chordae tendineae or damaged papillary muscles
86
3 types of valve faults
1. Stenotic valve (doesn't open)
2. Regurgitant valve (doesn't close)
3. Prolapsed valve (flops backwards)
87
Heart murmurs
Fault valves heard through stethoscope
88
Why do semilunar valves not need muscular braces?
Because the arterial walls do not contract and so the cusps are stable
89
What prevents the individual cusps of the aortic valve from sticking to the walls of the aorta?
Aortic sinuses
90
Valvular heart disease (VHD)
When valve function deteriorates to the point at which the heart cannot maintain adequate circulatory flow
91
Carditis
Inflammation of the heart
92
Rheumatic fever
Inflammatory autoimmune response to an infection by streptococcal bacteria, occurring most often in children and causing carditis
93
Coronary circulation
Supplies blood to muscle tissue of the heart
94
Where do the left and right coronary arteries originate?
At the base of the ascending aorta, at the aortic sinuses
95
Elastic rebound
Recoil of the aortic walls when the left ventricle relaxes, blood no longer flows into the aorta and pressure declines
96
Marginal arteries
Arteries that arise from right coronary artery and that extend across the surface of the right ventricle
97
Posterior interventricular artery
Supplies blood to the interventricular septum and adjacent portions of the ventricles
98
Right coronary artery
Supplies blood to:
1. Right atrium
2. Portions of ventricles
3. Portions of electrical conducting system of heart
99
Left coronary artery
Supplies blood to:
1. Left atrium
2. Left ventricle
3. Interventricular septum
100
Circumflex artery
Arises from left coronary artery and curves to the left around the coronary sulcus
101
Anterior interventricular artery
Arises from left coronary artery and swings around the pulmonary trunk, and rungs along the surface within the anterior interventricular sulcus
102
Arterial anastomes
Interconnections between arteries
103
Coronary artery disease (CAD)
Areas of partial or complete blockage of coronary circulation
104
Coronary ischemia
Reduced circulatory supply usually as a result from CAD
105
Cause of CAD
Formation of fatty deposit (atherosclerotic plaque) in the wall of a coronary vessel which narrows the passageway and reduces blood flow
106
Angina pectoris
First symptom of CAD - chest pain spasm
107
Myocardial infarction
Heart attack, when part of the coronary circulation becomes blocked, and cardiac muscle cells die from lack of oxygen
108
Infarct
Nonfunctional area created from death of affected tissues during myocardial infarction
109
Coronary thrombosis
When a vessel already narrowed by plaque formation becomes blocked by a sudden spasm in the smooth muscles of the vascular wall
110
Enzymes released during heart attack
Cardiac toponin T, cardiac troponin I, and CK-MB (form of creatine phosphate)
111
Great cardiac vein
Drains blood from region supplied by anterior interventricular artery
112
Where do cardiac veins return blood to?
Coronary sinus which opens into the right atrium
113
Posterior vein of left ventricle
Drains area served by circumflex artery
114
Middle cardiac vein
Drains area supplied by posterior interventricular artery
115
Small cardiac vein
Receives blood from posterior surfaces of right atrium and ventricle
116
Anterior cardiac veins
Drain the anterior surface of the right ventricle and empty directly into the right atrium
117
Audtorhythmicity
The hearts property of contracting on its own
118
Conducting system
The cells that initiate and distribute stimulus to contract
119
Two types of specialised cardiac muscle cells of conducting system
1. Pacemaker cells - essential to heart rate
| 2. Conducting cells - interconnect SA and AV nodes and distribute contractile stimulus throughout myocardium
120
Where are pacemaker cells found?
Sinoatrial (SA) node in atrium and atrioventricular (AV) node
121
Where are conducting cells found?
Internodal pathways in atrial walls
Atrioventricular (AV) bundle
Bundle branches - run between ventricles
Purkinje fibres
122
Special characteristic of pacemaker cells of SA and AV nodes
No stable membrane resting potential (instead, pacemaker potential)
123
What causes pacemaker potential?
Slow inflow of Na+ without a compensating outflow of K+
124
Where is spontaneous depolarisation fastest?
In cells in the SA node
125
Pacemaker potential
Gradual depolarisation of pacemaker cells
126
Sinus rhythm
Heart rhythm
127
What establishes the sinus rhythm
The SA nodes reaching threshold first
128
Why is the maximum normal heart rate 230 bpm?
Because even if the SA node generates impulses at a faster rate, the ventricles will still only contract at 230 bpm
129
Impulse conduction - 0
SA node activity and trial activation begin
130
Impulse conduction - 50msec
Stimulus spreads across the atrial surfaces and reaches AV node
P wave
131
Impulse conduction - 150msec
Three is a 100msec delay at the AV node. Atrial contraction begins
P-R interval
132
Impulse conduction - 175msec
The impulse travels along the interventricular septum within the AV bundle and the bundle branches to the Purkinje fibres, and, by the moderator band, to the papillary muscles of the right ventricle
Q wave
133
Impulse conduction - 225msec
The impulse is distributed by Purkinje fibres and relayed throughout ventricular myocardium. Atrial contraction is completed and ventricular contraction begins
QRS complex
134
Why does the pacemaker cell stimulus affect only the atria?
Because the cardiac skeleton isolates the atrial myocardium from the ventricular myocardium
135
Why does the pacemaker impulse slow as it leaves internodal pathway and enters the AV node?
Because the nodal cells are smaller in diameter than the conducting cells and the interconnections between pacemaker cells are less efficient than those between conducting cells
136
What would happen if the atria and ventricles contracted at the same time?
The contraction of the powerful ventricles would close the AV valves and prevent blood flow from the atria to ventricles
137
Where is the only normal electrical connection between the atria and the ventricles?
The connection between the AV node and the AV bundle
138
Which bundle branch is bigger?
The left bundle branch, as it supplies the massive left ventricle
139
Bradychardia
Heart rate is slower than normal
140
Tachycardia
Heart rate is father than normal
141
Ectopic pacemaker
Their activity partially or completely bypasses the conducting system, disrupting the timing of the ventricular contraction
142
Electrocardiogram
Monitors the electrical events of the conducting system
143
Which components are important for in making a diagnosis with ECG?
P wave and QRS complex
144
Q-T inerval
The time required for the ventricles to undergo a single cycle of depolarisation and repolarisation (measured from the end of the P-R interval)
145
Arrhythmia
Irregularity in the normal rhythm or force of the heartbeat
146
Cardiac contractile cells
Form the bulk of the atrial and ventricular walls
147
Where do the Purkinje fibres pass the stimulus on to?
Cardiac contractile cells
148
What connects cardiac contractile cells to each other?
Intercalated discs
149
Key differences between cardiac contractile cells and skeletal muscle fibres
1. Cardiac - smaller
2. Cardiac - 1 nucleus
3. Cardiac - branching interconnections between cells
4. Cardiac - intercalated discs
150
How are the interlocking membranes of adjacent cells held together at intercalated discs?
By desmosomes and linked by gap junctions
151
Action potentital in cardiac contractile cells
1. Rapid depolarisation: causes NA+ entry, ends with closure of voltage-gated fast sodium channels
2. The Plateau: causes Ca2+ entry, ends with closure of slow calcium channels
3. Repolaraisation: causes K+ loss, ends with closure of slow potassium channels
152
Refractory period
Period of time after an action potential when a cardiac contractile cell won't respond to a second stimulus
153
Absolute refractory period
- The membrane cannot respons at all because the sodium ion channels are either already open or closed and inactivated
- Includes plateau and initial period of repolarisation
154
Relative refractory period
Voltage gated sodium ion channels are closed but can open so the membrane will respond to a stronger than normal stimulus
155
Cardiac cycle
Period between the start of one heart beat and the beginning of the next
156
Systole
The chamber contracts and pushes blood into an adjacent chamber of into an arterial trunk
157
Diastole
The chamber fills with blood and prepares for the next cardiac cycle
158
Phases of the cardiac cycle
1. Atrial systole
2. Atrial diastole
3. Ventricular systole
4. Ventricular diastole
159
Atrial systole
1. Atrial contraction begins - already 70% filled
| 2. Atria ejects blood into the ventricles through open right and left AV valves - remaining 30%
160
Why can't blood flow into the atria from the veins during atrial systole?
Because atrial pressure exceeds venous pressure
161
Ventricular systole
1. AV valves close
2. Ventricles contracting but no blood flow occurs as the pressure isn't high enough to force open semilunar valves
3. Ventricular ejection: semilunar valves are pushed open and blood flows into pulmonary or aortic trunk
4. Semilunar valve closes and blood flows into relaxed atria
5. AV valves open and passive ventricular filling occurs
162
Isovolumetric contraction
All the heart valves are closed, the volumes of the ventricles do not change and the ventricular pressure is rising
163
Heart failure
When damage to one or both ventricles can leave the heart unable to pump enough blood through peripheral tissues and organs
164
Cardiac output (CO)
Amount of blood pumped by the left ventricle in 1 minute
165
Heart rate (HR)
Number of heart beats per minute
166
Stroke volume (SV)
Amount of blood pumped our of a ventricle during each contraction
EDV - ESV
167
CO calculation
HR X SV
168
Cardioacceleratory center
In the medulla oblongata activates sympathetic neurons which speeds up heart rate and reduces ESV
169
Cardioinhibitory centre
Controls parasympathetic neurons that slow the heart rate and increases ESV
170
Bainbridge reflex
Accelerates heart rate when the walls of the right atrium are stretched
171
Venous return
Amount of blood retuning to heart through veins
172
Filling time
Duration of ventricular diastole
173
Preload
Degree of stretching in ventricular muscle cells during ventricular diastole
174
Afterload
Amount of tensions that the contracting ventricle must produce to force open the semilunar valve and eject blood
175
Frank-Straling principle
The greater the EDV, the more powerful the succeeding contraction
176
Cardiac reserve
Difference between resting and maximal cardiac outputs
