Ch.20: THE CARDIOVASCULAR SYSTEM: THE HEART Flashcards
(84 cards)
1
Q
Where is the heart located in the body?
A
-it rests on the diaphragm, near the midline of the thoracic cavity
2
Q
The heart lies in the mediastinum, what is this?
A
an anatomical region that extends from the sternum to the vertebral column, from the first rib to the diaphragm, and between the lungs
3
Q
Picture the shape of the heart, what is the tip of the left ventricle (lower chamber of the heart) called? Where is it directed?
A
apex is directed anteriorly, inferiorly, and to the left
4
Q
What is the base of the heart made of and where is it located?
A
- heart’s posterior surface
- formed by the atria (upper chambers) of the heart, mostly the left atrium
5
Q
The heart has several surfaces and borders, where is the anterior surface located?
A
deep to the sternum and ribs
6
Q
The heart has several surfaces and borders, where is the inferior surface located?
A
part of the heart between the apex and right border and rests mostly on the diaphragm
7
Q
The heart has several surfaces and borders, where is the right border located?
A
faces the right lung and extends from the inferior surface to the base
8
Q
The heart has several surfaces and borders, where is the left border (pulmonary border) located?
A
faces the left lung and extends from the base to the apex
9
Q
What is the pericardium? What are its two parts?
A
membrane that surrounds and protects the heart
1) superficial fibrous pericardium
2) deep serous pericardium
10
Q
In terms of the pericardium, explain the superficial fibrous layer:
A
- composed of tough, inelastic, dense irregular connective tissue
- its open end is fused to connective tissues of blood vessels entering/leaving heart
- prevents overstretching, provides protection, and anchors heart in mediastinum
11
Q
In terms of the pericardium, explain the deep serous layer and the two layer within it:
A
- thinner, more delicate membrane that forms double layer around heart
- outer parietal layer: fused to the fibrous pericardium
- inner visceral layer: (epicardium) one layer of heart wall and adheres to heart
12
Q
What is pericardial fluid, where is it located and what is its function?
A
- thin film of lubricating serous fluid
- between parietal and visceral layers of serous pericardium
- reduces friction between layers of the serous pericardium as the heart moves
13
Q
What does the pericardial cavity contain?
A
pericardial fluid
14
Q
What are the three layers of the heart wall? Explain them.
A
1) epicardium (external layer): has 2 tissue layers
- outermost layer: visceral layer of the serous pericardium
- innermost layer: variable layer of delicate fibroelastic tissue and adipose tissue
2) myocardium (middle layer): pumps heart, made of cardiac muscle tissue
3) endocardium (inner layer): thin layer of endothelium overlying thin layer of connective tissue
- provides smooth lining for heart chambers and covers heart valves
15
Q
What are the 4 chambers of the heart?
A
1) Left atria
2) Right atria
3) Left ventricle
4) Right ventricle
16
Q
What do the atria do and what do the ventricles do?
A
- atria receive blood from blood vessels returning blood to the heart, called veins
- ventricles eject blood from the heart into blood vessels called arteries
17
Q
What is an auricle and where is it located? What does it do?
A
- wrinkled pouchlike structure on anterior surface of each atrium
- slightly increases capacity of atrium to hold more blood
18
Q
What are sulci on the heart?
A
- series of grooves containing coronary blood vessels and fat
- each one marks boundary between heart chambers
19
Q
What is the coronary sulcus, what boundary does it mark?
A
encircles most of the heart and marks the external boundary between the superior atria and inferior ventricles
20
Q
What is the anterior interventricular sulcus, what boundary does it mark?
A
shallow groove on the anterior surface of the heart that marks the external boundary between the right and left ventricles
21
Q
What is the posterior interventricular sulcus, what boundary does it mark?
A
marks the external boundary between the ventricles on the posterior aspect of the heart
22
Q
Where is the right atrium? Where does it receive blood from? Describe the walls of the right atrium.
A
- forms the right border of the heart
- receives blood from 3 veins: the superior vena cava, inferior vena cava, and coronary sinus
- inside of posterior wall is smooth; inside of anterior wall is rough due to presence of pectinate muscles
23
Q
What is the interatrial septum?
A
thin partition between the right atrium and left atrium
24
Q
What is the fossa ovalis?
A
oval depression, remnant of the foramen ovale, an opening in the interatrial septum of the fetal heart that normally closes soon after birth
25
What is the tricuspid valve/right atrioventricular valve?
a valve where blood passes from the right atrium into the right ventricle, consists of 3 leaflets or cusps
26
Where is the right ventricle? What does it contain?
- forms most of the anterior surface of the heart
- contains ridges formed by trabeculae carneae
- cusps of tricuspid valve are connected to chordae tendineae, which are connected to papillary muscles
- blood passes from it through pulmonary valve into pulmonary trunk, which divides into pulmonary arteries and carries blood to lungs
27
What is the interventricular septum?
-separates the right ventricle from the left ventricle
28
Arteries always take blood away from the heart. Veins always return blood to the heart. True or False
True
29
Where is the left atrium? Where does it receive blood from? What does it contain?
- forms most of the base of the heart
- receives blood from lungs through 4 pulmonary veins
- has a smooth posterior wall
30
Blood passes from the ___ atrium into the ___ ventricle through the bicuspid (mitral) valve (left atrioventricular valve), which, has __ cusps. Blood passes from the left ventricle through the ___ valve into the ascending aorta.
Some of the blood in the aorta flows into the ____ arteries, which branch from the ascending aorta and carry blood to the heart wall. The remainder of the blood passes into the arch of the aorta and descending aorta (thoracic aorta & abdominal aorta).
- left, left ventricle, 2
- aortic
- coronary arteries
31
Where is the left ventricle located? What does it contain?
- thickest chamber of the heart, forms the apex of the heart
| - contains trabeculae carneae and chordae tendineae that anchor cusps of bicuspid valve to papillary muscles
32
During fetal life, what temporary vessel shunts blood from the pulmonary trunk into the aorta? (so only a small amount of blood enters the nonfunctioning fetal lungs). When it closes after birth, what does it leave behind?
- ductus arteriosus
| - leaves the ligamentum arteriosum, which connects the arch of the aorta and pulmonary trunk
33
Which chambers are thicker and why?
- the thin-walled atria deliver blood under less pressure into the adjacent ventricles
- because the ventricles pump blood under higher pressure over greater distances, their walls are thicker
34
Which ventricle has a smaller workload and why?
- right ventricle has a much smaller workload than the left ventricle (the right one pumps blood a short distance to the lungs at lower pressure, and the resistance to blood flow is small)
- so the left ventricle works harder to maintain the same rate of blood flow
35
The heart wall contains dense connective tissue that forms the fibrous skeleton of the heart, what does it consist of? What does it prevent? What does it do?
- consists of 4 dense connective tissue rings that surround the valves of the heart, fuse with one another, and merge with the interventricular septum
- prevents overstretching of the valves as blood passes through them
- serves as a point of insertion for bundles of cardiac muscle fibers and acts as an electrical insulator between the atria and ventricles
36
Because they are located between an atrium and a ventricle, the tricuspid and bicuspid valves are termed what?
atrioventricular (AV) valves
37
How do atrioventricular valves work? What does it prevent? What happens when they are damaged?
- when open, rounded ends of cups project into ventricle
- when ventricles are relaxed, papillary muscles are relaxed, chordae tendieae are slack, and blood moves from a HP in atria to a LP in ventricles through open AV valves
- when ventricles contract, blood pressure drives cusps upward until their edges meet and close opening
- papillary muscles contract, which pulls on and tightens chordae tendineae
- prevents valve cusps from opening into atria in response to high ventricular pressure
- if AV valves or chordae tendineae are damaged, blood may regurgitate into atria when ventricles contract
38
What are the semilunar (SL) valves? What are they made of? What do they do? What does it prevent?
- aortic and pulmonary valves, made of 3 crescent moon-shaped cusps
- each cusp attaches to the arterial wall by its convex outer margin
- allow ejection of blood from heart into arteries but prevents backflow of blood into ventricles
- free borders of the cusps project into lumen of artery
- these valves open when pressure in ventricles exceeds pressure in arteries, permitting ejection of blood from ventricles into pulmonary trunk and aorta
- as ventricles relax, blood starts to flow back toward heart
39
In postnatal circulation, the heart pumps blood into two closed circuits with each beat, what are they?
systemic circulation and pulmonary circulation
40
Explain systemic circulation:
- pumps left side of heart
- receives bright red oxygenated blood from the lungs
- left ventricle ejects blood into aorta
- most blood goes into smaller systemic arteries that carry it to all organs, except for lungs
- in systemic tissues, arteries give rise to smaller-diameter arterioles, which lead into systemic capillaries
- exchange of nutrients and gases occurs: blood unloads O2 and picks up CO2
- blood enters a systemic venule
- blood flows back to right atrium
41
Explain pulmonary circulation:
- receives all dark-red deoxygenated blood returning from systemic circulation
- Blood ejected from right ventricle flows into pulmonary trunk, which branches into pulmonary arteries that carry blood to lungs
- In pulmonary capillaries, blood unloads CO2, which is exhaled, and picks up oxygen from inhaled air
- Freshly oxygenated blood then flows into pulmonary veins and returns to left atrium
42
The myocardium has its own network of blood vessels, the coronary/cardiac circulation, explain it.
- coronary arteries: branch from the ascending aorta and encircle the heart
- while the heart is contracting, little blood flows in coronary arteries because they are squeezed shut
- when heart relaxes, high pressure of blood in aorta propels blood through coronary arteries, into capillaries, and then into coronary veins
43
Discuss the left and right coronary arteries:
- branch from ascending aorta and supply oxygenated blood to the myocardium
- left one passes inferior to left auricle and divides into anterior interventricular and circumflex branches
- right one supplies atrial branches to right atrium, it continues inferior to right auricle and divides into posterior interventricular and marginal branches
44
Discuss the 4 branches of the coronary circulation:
- anterior interventricular branch: (left anterior descending artery) is in anterior interventricular sulcus and supplies oxygenated blood to walls of both ventricles
- circumflex branch: lies in coronary sulcus and distributes oxygenated blood to the walls of the left ventricle and left atrium
- posterior interventricular branch: follows posterior interventricular sulcus and supplies walls of ventricles with oxygenated blood
- marginal branch: beyond the coronary sulcus runs along the right margin of the heart and transports oxygenated blood to myocardium of the right ventricle
45
After blood passes through arteries of coronary circulation, it flows into capillaries, where it delivers O2 and nutrients to the heart muscle and collects CO2 and waste, and then moves into coronary veins. What are the 4 veins? Explain them and give their location.
1) Great cardiac vein: in anterior interventricular sulcus, which drains both ventricles and left atrium
2) Middle cardiac vein: in posterior interventricular sulcus, which drains both ventricles
3) Small cardiac vein: in coronary sulcus, which drains right atrium and right ventricle
4) Anterior cardiac veins: which drain right ventricle and open directly into the right atrium
46
What do autorhythmic fibers do? What are their 2 functions?
this network of specialized cardiac muscle fibers cause electrical activity for heartbeats (they are self-excitable)
1) pacemaker: set rhythm of electrical excitation that causes heart contraction
2) form the cardiac conduction system, a network of specialized cardiac muscle fibers that provide a path for each cycle of cardiac excitation to progress through heart
47
Cardiac action potentials propagate through the conduction system in the following sequence:
1) sinoatrial node spontaneously depolarizes, so when it reaches threshold, it triggers an action potential that propagates throughout both atria via gap junctions in intercalated discs of atrial muscle fibers
2) AP reaches the atrioventricular node, AP slows down so atria can empty blood into ventricles
3) AP enters the atrioventricular bundle
4) AP enters right and left bundle branches
5) Purkinje fibers conduct AP from apex to ventricular myocardium. Ventricles contract, pushing blood to semilunar valves.
48
The sinoatrial node sets what?
sets the rhythm for contraction of the heart- it is the natural pacemaker
49
An action potential is initiated by the sinoatrial node and travels along the conduction system and spreads out to excite the “working” atrial and ventricular muscle fibers, called contractile fibers. An AP occurs in a contractile fiber as follows:
1) Depolarization (sodium ion inflow when voltage-gated fast Na+ channels open)
2) Plateau phase (maintained depolarization due to calcium ion inflow and potassium ion outflow)
3) Repolarization (calcium channels close b/c more potassium channels open)
50
In a typical heartbeat, three waves appear with each heartbeat. What are they?
1) P wave: small upward deflection that represents atrial depolarization, which spreads from the SA node through contractile fibers in both atria
2) QRS complex: begins as a downward deflection, continues as a large, upright, triangular wave, and ends as a downward wave (Represents rapid ventricular depolarization, as the AP spreads through ventricular contractile fibers)
3) T wave: dome-shaped upward deflection, Indicates ventricular repolarization and occurs just as the ventricles are starting to relax
51
What does an electrocardiogram measure?
a recording of APs produced by all the heart muscle fibers during each heartbeat
52
Analysis of an electrocardiogram also involves measuring the time spans between waves, which are called intervals or segments. Describe the P-Q interval:
- time from the beginning of the P wave to the beginning of the QRS complex
- It represents the conduction time from the beginning of atrial excitation to the beginning of ventricular excitation (time required for the AP to travel through the atria, atrioventricular node, and the remaining fibers of the conduction system)
53
Analysis of an electrocardiogram also involves measuring the time spans between waves, which are called intervals or segments. Describe the S-T segment:
-begins at end of S wave and ends at beginning of T wave, represents the time when the ventricular contractile fibers are depolarized during the plateau phase of the AP
54
Analysis of an electrocardiogram also involves measuring the time spans between waves, which are called intervals or segments. Describe the Q-T interval:
-extends from start of QRS complex to the end of the T wave, it is the time from the beginning of ventricular depolarization to the end of ventricular repolarization
55
What does systole represent?
phase of contraction
56
What does diastole represent?
phase of relaxation
57
The electrocardiogram waves predict the timing of atrial and ventricular systole and diastole. At a heart rate of 75 beats per minute, the timing is as follows:
1) depolarization of atrial contractile fibers produces P wave
2) atrial systole (contraction)
3) depolarization of ventricular contractile fibers produces QRS complex
4) ventricular systole (contraction)
5) repolarization of ventricular contractile fibers produces T wave
6) ventricular diastole (relaxation)
58
Give a brief definition of the cardiac cycle. What is the order of it?
- all events associated with one heartbeat (consists of systole and diastole of atria and ventricles)
- atrial systole/ventricular diastole, ventricular systole/atrial diastole, relaxation period
59
When heart rate is 75 beats/min, a cardiac cycle lasts how long?
0.8s
60
What happens during atrial systole and ventricles diastole? How long does it last? List the 4 steps
- atria are contracting and the ventricles are relaxed, lasts 0.1s
1) Depolarization of SA node causes atrial depolarization, marked by the P wave
2) Atrial depolarization causes atrial systole. As atria contract, they exert pressure on blood within, which forces blood through open AV valves into ventricles.
3) Atrial systole contributes blood to volume in each ventricle. The end of atrial systole is also end of ventricular diastole. Thus, each ventricle contains about 130mL at end of diastole (end-diastolic volume)
4) QRS complex marks onset of ventricular depolarization
61
What happens during ventricular systole and atrial diastole? How long does it last? List the 4 steps
- ventricles are contracting, lasts about 0.3s
- at the same time, the atria are relaxed in atrial diastole
5) As ventricular systole begins, pressure rises in ventricles forcing AV valves shut. For about 0.05s, both SL and AV valves are closed (isovolumetric contraction).
6) When left ventricular pressure surpasses aortic pressure and right ventricular pressure rises above pressure in pulmonary trunk, both SL valves open. Ejection of blood from heart begins.
7) Left ventricle ejects blood into aorta and right ventricle ejects blood into pulmonary trunk. Volume remaining in each ventricle at end of systole is end-systollic volume
8) T wave marks onset of ventricular repolarization
62
In terms of ventricular systole and diastole, what is the stoke volume? Give the equation.
- the volume ejected per beat from each ventricle
| - equals end-diastolic volume minus end-systolic volume: SV = EDV – ESV
63
Explain the relaxation period of the cardiac cycle. How long does it last? What are the two steps?
- atria and ventricles are relaxed, lasts 0.4s,
9) Ventricular repolarization causes ventricular diastole. Blood flows back to regions of LP in ventricles and closes SL valves. Brief interval when ventricular blood volume doesn't change because all 4 valves are closed (isovolumetric relaxation)
10) Pressure falls fast. When ventricular pressure drops below atrial pressure, the AV valves open, and ventricular filling begins. Blood has been building up in atria during ventricular systole then rushes into ventricles. P wave signals another cardiac cycle.
64
During each cardiac cycle, there are 4 heart sounds, explain them. Which ones can you hear through a stethoscope and which ones can you not? What are they caused by?
- only S1 and S2 sounds can be heard
- S1: lubb sound, its louder and longer than S2 (caused by blood turbulence associated with closure of AV valves after ventricular systole begins)
- S2: dupp sound, its shorter and not as loud (caused by blood turbulence associated with closure of SL valves at beginning of ventricular diastole)
- S3 and S4 cannot be heard (S3 is due to blood turbulence in rapid ventricular filling, S4 is due to blood turbulence during atrial systole)
65
Explain cardiac output. What is the equation?
```
-volume of blood ejected from the left ventricle (or right one) into the aorta (or pulmonary trunk) each minute
Cardiac Output (mL/min) = Stroke Volume(mL/beat) x Heart Rate(beats/min)
```
66
Explain stroke volume.
volume of blood ejected by the ventricle during each contraction
67
In a typical resting adult male, stroke volume is 70mL/beat, heart rate is 75 beats/min, calculate the cardiac output:
CO = 70 mL/beat x 75 beats/min
= 5250 mL/min
= 5.25 L/min
68
What is a cardiac reserve?
difference between a person’s maximum cardiac output and cardiac output at rest
69
What are the 3 factors that regulate stroke volume and ensure that the left and right ventricles pump equal volumes of blood?
1) preload: degree of stretch on the heart before it contracts
2) Contractility: forcefulness of contraction of individual ventricular muscle fibers
3) afterload: pressure that must be exceeded before ejection of blood from the ventricles can occur
70
What is the Frank-Starling law of the heart?
the more the heart fills with blood during diastole, the greater the force of contraction during systole
71
What are positive inotropic agents? Give an example.
- substances that increase contractility
| - often promote Ca2+ inflow during cardiac APs, which strengthens the force of next contraction
72
What are negative iontropic agents? Give an example.
- substances that decrease contractility
- calcium channel blockers are drugs that can have a negative iontropic effect by reducing Ca2+ inflow, thereby decreasing the strength of the heartbeat
73
List 2 conditions that increase afterload of stroke volume:
hypertension (elevated blood pressure), and narrowing of arteries by atherosclerosis
74
What is the cardiovascular centre?
- nervous system regulation of the heart originates here in the medulla oblongata
- directs appropriate output by increasing or decreasing the frequency of nerve impulses in both the sympathetic and parasympathetic branches of the ANS
75
Proprioceptors, chemoreceptors and barorecetors all send signals to the cardiovascular centre for? (3 different things)
- proprioceptors monitor position of limbs/muscles during physical activity
- chemoreceptors monitor chemical changes in blood
- baroreceptors monitor stretching of major arteries and veins caused by pressure of the blood flowing through them
76
In terms of the cardiovascular centre, sympathetic cardiac accelerator nerves extend out to what nodes? What do APs formed here trigger? What are the 2 effects of this interaction?
- SA node, AV node
- impulses trigger release of norepinephrine, which binds to beta-1 receptors on cardiac muscle fibers
1) In SA (and AV) node fibers, norepinephrine speeds the rate of spontaneous depolarization so that these pacemakers fire impulses faster and heart rate increases
2) In contractile fibers of the atria and ventricles, norephineprhine enhances Ca2+ entry through the voltage-gated slow Ca2+ channels, thereby increasing contractility
- as a result, a greater volume of blood is ejected during systole
77
Several hormones and cations have major effects on the heart, explain some effects.
1) Hormones: Epinephrine and norepinephrine affect cardiac muscle fibers by increasing heart rate and contractility.
2) Cations: relative concentrations of K+, Ca2+, and Na+ decrease heart rate and contractility in high levels. A moderate increase in interstitial Ca2+ level speeds heart rate and strengthens the heartbeat
78
What is bradycardia?
a resting heart rate under 50 beats/min
79
Heart begins its development from _____ on day 18/19 following fertilization. In the head end of the embryo, the heart develops from a group of mesodermal cells called the ______ area. In response to signals from the underlying endoderm, the mesoderm in this area forms a pair of elongated strands called ______ cords. These cords develop a hollow centre and then become known as _____ tubes. With lateral folding of the embryo, the paired endocardial tubes approach each other and fuse into a single tube called the _____ heart tube on day 21 following fertilization.
Heart begins its development from mesoderm on day 18/19 following fertilization. In the head end of the embryo, the heart develops from a group of mesodermal cells called the cardiogenic area. In response to signals from the underlying endoderm, the mesoderm in the cardiogenic area forms a pair of elongated strands called cardiogenic cords. These cords develop a hollow centre and then become known as endocardial tubes. With lateral folding of the embryo, the paired endocardial tubes approach each other and fuse into a single tube called the primitive heart tube on day 21 following fertilization.
80
On day 22, the primitive heart tube develops into 5 regions and begins to pump blood. From tail end to head end (blood flow direction), list the 5 regions.
1) sinus venosus
2) primitive atrium
3) primitive ventricle
4) bulbus cordis
5) truncus arteriosus
81
Sinus venosus initially receives blood from all the veins in the embryo; contractions of the heart begin here and follow sequentially in the other regions. At this stage, the heart consists of a series of unpaired regions, what do the 5 regions develop into?
1) the sinus venosus develops into part of the right atrium (posterior wall), coronary sinus, and sinoatrial (SA) node
2) The primitive atrium develops into part of the right atrium (anterior wall), right auricle, part of the left atrium (anterior wall), and the left auricle.
3) The primitive ventricle gives rise to the left ventricle
4) The bulbus cordis develops into the right ventricle
5) The truncus arteriosus gives rise to the ascending aorta and pulmonary trunk
82
On day 23, primitive heart tube elongates. At first the primitive heart tube assumes a _-shape; later it becomes S-shaped. As a result of these movements, which are completed by day 28, the primitive ___ and ventricles of the future heart are reoriented to assume their final adult positions. Remainder of heart development consists of remodeling of the chambers and the formation of ___ and valves to form a __-chambered heart.
On day 23, primitive heart tube elongates. At first the primitive heart tube assumes a U-shape; later it becomes S-shaped. As a result of these movements, which are completed by day 28, the primitive atria and ventricles of the future heart are reoriented to assume their final adult positions. Remainder of heart development consists of remodeling of the chambers and the formation of septa and valves to form a four-chambered heart.
83
On day 28, thickenings of mesoderm of the inner lining of the heart wall, called ____ cushions, appear. They grow toward each other, fuse, and divide the single ______ canal into smaller, separate left and right atrioventricular canals. Also, the ____ septum begins its growth toward the fused endocardial cushions. Eventually, the interatrial septum and endocardial cushions unite and an opening in the septum, the ______ _______, develops.
- on day 28, thickenings of mesoderm of the inner lining of the heart wall, called endocardial cushions, appear
- they grow toward each other, fuse, and divide the single atrioventricular canal (region between atria and ventricles) into smaller, separate left and right atrioventricular canals
- also, the interatrial septum begins its growth toward the fused endocardial cushions
- eventually, the interatrial septum and endocardial cushions unite and an opening in the septum, the foramen ovale, develops
84
The ____ septum divides the atrial region into a right atrium and left atrium. Before birth, the foramen ovale allows most blood entering the right atrium to pass into the left atrium. After birth, it normally closes so that interatrial septum is a complete ____. The remnant of the foramen ovale is the ____ _____. Formation of the interventricular septum partitions the ventricular region into a right ventricle and a left ventricle. Partitioning of the atrioventricular canal, atrial region, and ventricular region is basically complete by the end of the ___ week. ______ valves form between the 5th and 8th weeks. ____ valves form between the 5th and 9th weeks
- the interatrial septum divides the atrial region into a right atrium and left atrium
- before birth, the foramen ovale allows most blood entering the right atrium to pass into the left atrium
- after birth, it normally closes so that interatrial septum is a complete partition
- the remnant of the foramen ovale is the fossa ovalis
- formation of the interventricular septum partitions the ventricular region into a right ventricle and a left ventricle
- partitioning of the atrioventricular canal, atrial region, and ventricular region is basically complete by the end of the 5th week
- atrioventricular valves form between the 5th and 8th weeks
- semilunar valves form between the 5th and 9th weeks
