Cardiovascular Anatomy Flashcards
What are the three main components of the cardiovascular system?
The heart, blood, and blood vessels.
What are the three layers of the heart wall?
Epicardium, myocardium, and endocardium.
What percentage of the heart’s mass is made up of myocardium?
75%.
What is the function of the pericardium?
It surrounds the heart and contains pericardial fluid to reduce friction during contractions.
What are the names of the four chambers of the heart?
Right atrium, left atrium, right ventricle, and left ventricle.
What is the role of the atrioventricular valves?
They ensure a one-way flow of blood from the atria to the ventricles.
What are the names of the atrioventricular valves?
Tricuspid valve (right) and mitral valve (left).
What are the semilunar valves?
The pulmonary valve and aortic valve.
What is the function of the semilunar valves?
They permit blood flow into the arteries during ventricular contraction and prevent backflow during relaxation.
Why is the myocardium thicker in the left ventricle than in the right ventricle?
The left ventricle has to exert considerable force to eject blood into the high-pressure arterial system.
What is the approximate pressure in the left ventricle during rest?
120 mmHg.
What is the approximate pressure in the right ventricle during rest?
25 mmHg.
What cells make up the bulk of the myocardium?
Contractile cells (myocytes).
What structural feature do myocardial muscle cells have in common with skeletal muscle?
They are made up of striated fibres.
What is unique about the contractile cells in the myocardium compared to skeletal muscle fibres?
They are short, branched, and interconnected.
What is the function of the heart’s electrical system?
It generates and conducts electrical impulses that coordinate heart contractions.
True or False: The electrical resistance between contractile cells in the myocardium is high.
False.
Fill in the blank: The heart’s apex points downward towards the _______.
diaphragm.
What separates the left and right sides of the heart?
The septum.
What are the two upper collecting chambers of the heart called?
Right atrium and left atrium.
What are the two lower dispatching chambers of the heart called?
Right ventricle and left ventricle.
What are the three main components of the cardiovascular system?
The heart, blood, and blood vessels.
What are the three layers of the heart wall?
Epicardium, myocardium, and endocardium.
What percentage of the heart’s mass is made up of myocardium?
75%.
What is the function of the pericardium?
It surrounds the heart and contains pericardial fluid to reduce friction during contractions.
What are the names of the four chambers of the heart?
Right atrium, left atrium, right ventricle, and left ventricle.
What is the role of the atrioventricular valves?
They ensure a one-way flow of blood from the atria to the ventricles.
What are the names of the atrioventricular valves?
Tricuspid valve (right) and mitral valve (left).
What are the semilunar valves?
The pulmonary valve and aortic valve.
What is the function of the semilunar valves?
They permit blood flow into the arteries during ventricular contraction and prevent backflow during relaxation.
Why is the myocardium thicker in the left ventricle than in the right ventricle?
The left ventricle has to exert considerable force to eject blood into the high-pressure arterial system.
What is the approximate pressure in the left ventricle during rest?
120 mmHg.
What is the approximate pressure in the right ventricle during rest?
25 mmHg.
What cells make up the bulk of the myocardium?
Contractile cells (myocytes).
What structural feature do myocardial muscle cells have in common with skeletal muscle?
They are made up of striated fibres.
What is unique about the contractile cells in the myocardium compared to skeletal muscle fibres?
They are short, branched, and interconnected.
What is the function of the heart’s electrical system?
It generates and conducts electrical impulses that coordinate heart contractions.
True or False: The electrical resistance between contractile cells in the myocardium is high.
False.
Fill in the blank: The heart’s apex points downward towards the _______.
diaphragm.
What separates the left and right sides of the heart?
The septum.
What are the two upper collecting chambers of the heart called?
Right atrium and left atrium.
What are the two lower dispatching chambers of the heart called?
Right ventricle and left ventricle.
What principle applies to a single motor unit in skeletal muscle?
The all-or-none principle
How does the force of contraction in skeletal muscle depend on muscle fibers?
It depends upon the number of muscle fibres recruited
What allows for synchronized contraction of the myocardium?
The interconnectedness of the myocardial cells acting as a single motor unit
Where is the impulse for heart contraction generated?
In the sinoatrial node
What is the location of the sinoatrial node?
In the posterior wall of the right atrium
What is the function of the atrioventricular node?
Conducts the impulse from the atria into the ventricles
Where is the atrioventricular node located?
In the right atrial wall near the centre of the heart
What is the coronary circulation often referred to as?
The plumbing system
Which layer of the heart is directly nourished by the blood flowing through the heart’s chambers?
The endocardium
How do myocardial cells receive their blood supply?
Via arteries that branch off the aorta
From where do the right and left coronary arteries arise?
From the base of the aorta, immediately above the cusps of the aortic valve
Fill in the blank: The main coronary arteries are listed in Box ______.
3.1
What are the two main types of pulmonary arteries mentioned?
Right and left pulmonary arteries
What valve is located between the right atrium and right ventricle?
Tricuspid valve
What structure prevents backflow into the ventricles during contraction?
Papillary muscles
What is the name of the valve located between the left atrium and left ventricle?
Bicuspid (mitral) valve
What is the function of the chordae tendinae?
To anchor the valves and prevent backflow
What separates the left and right ventricles?
Interventricular septum
What are the main branches of the left main artery?
The left anterior descending artery and the circumflex artery
These branches supply blood to the main part of the left ventricle.
Which artery supplies blood to the right ventricle?
The right coronary artery
It also supplies part of the posterior left ventricle.
What is the role of coronary arteries?
To deliver oxygen and nutrients to the myocardium and remove metabolic waste products
They form a dense network of capillaries on the surface of the heart.
How does deoxygenated blood leave the left ventricle?
Via a number of veins collected in the coronary sinus, which drains into the right atrium
The right ventricle’s deoxygenated blood leaves through the anterior cardiac vein.
What are the components of the vascular system?
Arteries, arterioles, capillaries, venules, and veins
Arteries and arterioles are high-pressure distribution vessels, capillaries are exchange vessels, and venules and veins are low-pressure collection and return vessels.
What are the three layers of blood vessel walls?
Tunica adventitia, tunica media, and tunica intima
The tunica adventitia is mainly tough connective tissue, the tunica media is mainly smooth muscle, and the tunica intima consists of endothelial cells.
What is the function of endothelial cells?
They provide a lining to the heart and blood vessels, secrete agents for vasodilation and vasoconstriction, release anti-clotting molecules, and inhibit smooth muscle cell proliferation and migration
Endothelial cells line all structures in the cardiovascular system.
What happens when the endothelial lining of coronary arteries is damaged?
It inhibits the functions of endothelial cells and results in the development of atherosclerotic plaque
The implications of this process are discussed in Chapter 4.
What characterizes arteries in systemic circulation?
They are high-pressure vessels that carry oxygen-rich blood to the tissues
The aorta and large arteries contain elastin fibers between smooth muscle cells.
What occurs during ventricular contraction in relation to arterial walls?
The arterial walls expand to accommodate blood and then recoil to drive blood through smaller arteries and arterioles
This process creates a pulse felt throughout the arterial system.
Which arteries are less elastic and provide the greatest resistance to flow?
Smaller arteries and arterioles
Their narrow lumina are less affected by pressure changes during systole and diastole.
What is vasodilation?
The relaxation of smooth muscle, increasing the vessel lumen and flow
This occurs in smaller arteries and arterioles.
What is vasoconstriction?
The contraction of smooth muscle, reducing the vessel lumen and flow
This process is crucial for regulating blood distribution in the body.
True or False: The distribution of blood around the body is determined by arteriolar smooth muscle activity.
True
The extent of smooth muscle activity in organs and tissues influences blood flow.
What are capillaries not capable of?
Vasoconstriction or vasodilation
Capillaries depend on arteriolar activity for blood flow regulation.
What do arteriolar vasodilation and vasoconstriction affect?
Capillary flow
Vasodilation increases flow, while vasoconstriction decreases flow.
What is the composition of capillary walls?
A single layer of endothelial cells
This structure allows for rapid transport of oxygen and nutrients.
What type of blood do capillaries feed into venules?
Deoxygenated blood
Blood is deoxygenated because oxygen has been taken up by active tissues.
How do veins and venules compare to arteries and arterioles?
They are relatively flaccid and more compliant
Most of the blood in the body is contained within the veins.
What role do smooth muscles play in the venous system?
They alter the volume and pressure within veins
Smooth muscle lining allows for vasoconstriction.
What function do valves in peripheral veins serve?
They allow blood to flow towards the heart and prevent backflow
Valves ensure unidirectional blood flow.
Fill in the blank: Capillaries end in a network of tiny vessels called _______.
Capillaries
Capillaries connect to venules.
What are metarterioles?
Less muscular vessels that branch from arterioles
They lead to capillary networks.
True or False: Capillaries have smooth muscle and connective tissue in their walls.
False
The absence of these tissues allows for rapid transport.
What percentage of blood volume is plasma?
55%
Plasma consists of approximately 90% water, 7% plasma proteins, and 3% other substances.
What are the main components of formed elements in blood?
> 99% red blood cells, <1% white blood cells and platelets
Formed elements comprise the cellular components of blood.
What is the primary fluid contained within cells?
Intracellular fluid
Approximately two-thirds of total body water is intracellular fluid.
Where is extracellular fluid distributed?
Between tissues (interstitial fluid) and blood plasma
Extracellular fluid constitutes one-third of total body water.
What drives the exchange of fluid between blood plasma and interstitial fluid?
Differences in pressure and concentration
Fluid moves out of or into the capillary based on these differences.
What is edema?
Excessive accumulation of interstitial fluid
Edema is often evident as swelling, such as swollen ankles.
What are the primary functions of the cardiovascular system?
- Deliver oxygen to all cells
- Return blood to the lungs for reoxygenation
- Remove waste products of cellular metabolism
- Transport nutrients, electrolytes, and hormones
- Maintain body temperature, fluid balance, and acid-base balance
- Prevent infection by invading organisms
These functions ensure adequate blood flow to all tissues.
What is the function of the heart?
To propel blood around the closed circulatory system
The heart ensures continuous circulation of blood throughout the body.
What is the pathway of blood from the left ventricle?
Left ventricle -> aortic valve -> aorta -> all parts of the body
This pathway is essential for delivering oxygen and nutrients.
How does venous blood return to the right atrium?
- Superior vena cava (from upper body and head)
- Inferior vena cava (from lower body)
- Coronary sinus (from coronary circulation)
These veins are crucial for returning deoxygenated blood to the heart.
What is the role of the pulmonary artery?
To carry blood from the right ventricle to the lungs
The pulmonary artery is essential for gas exchange.
What happens to blood in the lungs?
Gas exchange occurs
Oxygen is absorbed, and carbon dioxide is released in the capillaries of the lungs.
What is systemic circulation?
Flow of blood from the left ventricle to all parts of the body and back to the right atrium
Systemic circulation is vital for delivering oxygen and nutrients.
What is pulmonary circulation?
Flow of blood from the right ventricle to the lungs and back to the left atrium
This circulation is essential for reoxygenating blood.
What happens to the diaphragm during inhalation?
The diaphragm contracts and flattens out
What effect does inhalation have on abdominal and thoracic pressure?
Increases abdominal pressure and decreases thoracic pressure
How does inhalation affect blood flow to the heart?
It ‘sucks’ blood from the abdominal to the thoracic veins
What is the repeating pattern of contraction and relaxation of the heart called?
The cardiac cycle
What occurs after the contraction of the ventricles?
Blood is ejected into the systemic and pulmonary circulations
What happens to the aortic and pulmonary valves after ventricular contraction?
They close
What occurs during the relaxation phase of the cardiac cycle?
Both the atria and ventricles are relaxed, and the atria fill with blood
What percentage of the blood volume in the ventricles at the end of the filling phase is due to passive filling?
80%
What role do the atrioventricular valves play during the relaxation phase?
They open to allow blood to flow passively into the ventricles
How does ventricular contraction begin?
It starts from the apex of the heart and moves upward towards the base
What happens to the tricuspid and mitral valves during ventricular contraction?
They shut
What causes the pulmonary and aortic valves to open during ventricular contraction?
When ventricular pressures exceed the pressure in the pulmonary artery and aorta
What is the average heart rate in beats per minute (bpm)?
75 bpm
How long does each cardiac cycle last at an average heart rate of 75 bpm?
0.8 seconds
What is the duration of diastole at an average heart rate of 75 bpm?
0.5 seconds
What is the duration of systole at an average heart rate of 75 bpm?
0.3 seconds
At what heart rate does each cardiac cycle last 0.33 seconds?
180 bpm
What happens to the relaxation phase of the heart at a heart rate of 180 bpm?
It lasts for about 0.1 seconds
What is required for the cardiac cycle to take place?
Electrical stimulation of contractile cells in the myocardium
What is a nerve impulse?
An electrical charge that passes from one neuron to the next
True or False: Systole involves a mechanical event.
True
Fill in the blank: A nerve impulse travels through neurons in much the same way as _______ travels through domestic electric wires.
electricity
What is the first stage in electrical activity that culminates in muscle contraction?
Depolarisation
Where does electrical activity for each cardiac cycle start?
Sinoatrial node
What is the sinoatrial node referred to as?
The heart’s pacemaker
What is the rate established by the sinoatrial node called?
Sinus rhythm
What is the healthy resting heart rate range for an individual?
60 to 80 bpm
What property allows cardiac muscle to contract spontaneously?
Automaticity
What occurs after the impulse spreads throughout the atrial muscle fibres?
A delay of about 0.1 of a second
What is stimulated after the atrioventricular node?
The bundle of His and the Purkinje fibres
What is the result of the electrical activity being conducted through the bundle of His and Purkinje fibres?
Simultaneous contraction of both ventricles
Where does contraction of the ventricles start?
At the apex of the heart
What is the term for the period after ventricular contraction where the heart muscle cannot be stimulated again?
Refractory period
What does ‘P’ represent in an electrocardiogram?
Atrial Depolarisation
What does ‘QRS’ represent in an electrocardiogram?
Ventricular Depolarisation
What does ‘T’ represent in an electrocardiogram?
Ventricular Repolarization
What is the primary function of the cardiovascular system during changing demands?
To maintain adequate blood flow to all tissues.
What two main factors determine blood pressure within the cardiovascular system?
- Cardiac output (CO)
- Total peripheral resistance (TPR)
How is cardiac output (CO) calculated?
CO = HR x SV
What does HR stand for in the context of cardiac output?
Heart rate
What does SV stand for in the context of cardiac output?
Stroke volume
Which part of the nervous system decreases heart rate?
Parasympathetic system
What is the main neurotransmitter released by the parasympathetic system?
Acetylcholine
What is the typical resting heart rate range for adults?
60-80 bpm
What effect does the sympathetic system have on heart rate?
Increases heart rate and force of contraction
Which neurotransmitter is primarily involved in sympathetic stimulation of the heart?
Noradrenaline
What are catecholamines?
Adrenaline and noradrenaline
What receptors do adrenaline and noradrenaline act upon in the heart?
Beta-1 receptors (ß-1 receptors)
What is stroke volume?
The volume of blood ejected from each ventricle with each beat of the heart.
What is the ejection fraction?
The ratio of stroke volume to end diastolic volume.
What is the typical ejection fraction in healthy adults at rest?
About 66%
Fill in the blank: Blood pressure (BP) is calculated using the formula BP = _______.
CO x TPR
What happens to stroke volume when there is a more forceful contraction of the ventricles?
It can produce an increase in the amount of blood ejected.
What is stroke volume?
The amount of blood ejected by the heart with each contraction.
What are the two main mechanisms responsible for increasing stroke volume?
- Increase in end diastolic volume
- Increased sympathetic activity
What does the term ‘preload’ refer to?
The tension exerted on the ventricle walls due to the volume of blood they contain.
How does an increase in end diastolic volume affect stroke volume?
It causes greater distension of the ventricle walls, resulting in a more forceful contraction.
What role does sympathetic activity play in stroke volume?
It results in a more forceful contraction of the ventricles.
What is the effect of noradrenaline on the heart?
It increases contractility at a given preload.
What does total peripheral resistance represent?
The sum of all vascular resistance within the systemic circulation.
Why is it important to maintain normal limits of total peripheral resistance?
To ensure adequate blood flow to all tissues, particularly the brain.
Fill in the blank: Increased sympathetic activity results in more forceful contraction of the _______.
[ventricles]
What happens if all blood vessels in the body are vasodilated?
All impetus to blood flow would be lost and tissues would not be adequately perfused.
What is the relationship between cardiac output and blood pressure?
Cardiac output is one determinant of blood pressure.
How much blood does the brain receive as a percentage of total blood volume?
Approximately 149%.
What is the consequence of having a cross-sectional area of capillaries that is more than 800 times greater than the aorta?
If all blood vessels were vasodilated, blood flow would cease.
What percentage of blood is directed to the liver at rest?
27%.
How much blood do the kidneys receive as a percentage of total blood volume?
22%.
True or False: Blood-borne adrenaline acts on the same receptors as noradrenaline to increase contractility.
True.
What is the total volume of blood in the human body approximately?
5-6 litres.
What is the analogy used to explain total peripheral resistance?
The garden hose analogy.
What is the effect of increased total peripheral resistance on blood flow?
It helps maintain adequate blood flow to tissues.
What happens to blood flow if pressure is too low in the vascular system?
Blood would cease to flow through smaller vessels.
What happens to blood distribution during intense exercise?
Blood is redirected from less active tissues to active tissues, with skeletal muscle receiving up to 80% of circulating blood and kidneys reducing to about 3%
This redistribution is crucial for meeting the increased oxygen demand in active tissues.
How is blood redistributed to active tissues?
Mainly through local vasodilation in arterioles
This process is stimulated by metabolic waste products such as carbon dioxide and lactic acid.
What role does sympathetic nerve activity play in blood flow regulation?
It releases noradrenaline, causing vasoconstriction in less active tissues and vasodilation in active tissues
Noradrenaline acts on alpha-adrenergic receptors for vasoconstriction and beta-adrenergic receptors (B-2) for vasodilation.
What is the effect of noradrenaline and circulating adrenaline on the heart?
They increase heart rate and contractility, leading to increased cardiac output
This is primarily through action on B-1 adrenergic receptors.
What is the function of angiotensin I in the cardiovascular system?
It acts as a potent vasoconstrictor and helps retain fluid and salt
Angiotensin I is produced from the action of renin released by kidneys when blood pressure falls.
How is blood pressure regulated?
By changes in cardiac output and total peripheral resistance
These factors help maintain adequate blood flow to all body tissues.
Where are baroreceptors located?
In the aortic arch and carotid sinuses
They detect changes in blood pressure and initiate reflex responses.
What occurs when blood pressure increases?
The walls of arteries stretch, activating a reflex that reduces heart rate and causes vasodilation
This helps lower blood pressure back to normal levels.
What is orthostatic hypotension?
A transient drop in blood pressure when moving from lying or sitting to standing
It can cause dizziness and is more pronounced with rapid changes or in hot environments.
How is arterial blood pressure expressed?
As systolic pressure over diastolic pressure, e.g., 120 mmHg / 70 mmHg
Systolic pressure is the maximum pressure during ventricular contraction, while diastolic pressure is the minimum during relaxation.
What happens during systole in relation to coronary blood flow?
The openings of the coronary arteries are partially covered by the open cusps of the aortic valve, leading to very little blood entering the coronary circulation during ventricular contraction.
During which phase does the majority of coronary blood flow occur?
Diastole; roughly 80% of coronary blood flow occurs during this phase.
What percentage of cardiac output is diverted into the coronary circulation?
Between 4 and 5%.
What do myocardial fibres rely on for energy?
Energy released in oxidative (oxygen-using) reactions.
Which nutrients are used by myocardial cells to resynthesise ATP?
- Glucose
- Fatty acids
- Lactate
What is the myocardial oxygen extraction rate at resting heart rate?
70% of oxygen is extracted.
What are the factors that cause coronary arteries to dilate?
- Increased metabolic activity
- Release of nitric oxide from the endothelium
- Increased sympathetic activity
What is preload in relation to myocardial work?
The amount of tension exerted on the heart wall at the end of the diastolic phase due to the volume of blood in the ventricles.
Define afterload.
The resistance from the systemic circulation that must be overcome to eject the content of the left ventricle.
What is the rate pressure product (RPP)?
An index calculated by multiplying heart rate (HR) by systolic blood pressure (SBP) and dividing by 100.
How do you calculate RPP?
RPP = HR x SBP.
What does a higher RPP indicate?
The myocardium is working harder and will require more oxygen.
What influences the amount of oxygen used by the heart muscle?
The size of the heart muscle and how hard it has to work.
What is the primary metabolic process the myocardium relies on?
Aerobic metabolism.
True or False: The heart has a significant ability to resynthesise ATP anaerobically.
False; it has an extremely limited ability to resynthesise ATP anaerobically.
