Heart Structure and Function review
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What are the 3 layers of the heart?
*The heart is enclosed in a fibroserous sac called the pericardium
Which layer of the heart is the membrane lining the heart chambers and covers the heart valves?
*It is continuous with the endothelial lining of blood vessels entering and leaving the heart
Which layer of the heart is the strong muscular layer responsible for contraction?
Which layer of the heart is the outer, serous layer?
The heart is enclosed in a fibroserous sac called?
Each beat of the heart pumps how much blood a min?
60mL/min or 5L/min
The heart has four chambers: two atria and two ventricles. The atria are?
The atria are receiving chambers
The right atrium receives deoxygenated blood (venous return) from the upper part of the body by way of the_______, and from the lower part of the body by way of the_____?
The right atrium receives deoxygenated blood from the upper part of the body by way of the superior vena cava, and from the lower part of the body by way of the inferior vena cava
*The right atrium also receives blood from the heart muscle through the coronary sinus
The heart has four chambers: two atria and two ventricles. The ventricles are?
The ventricles are distributing chambers
The left atrium receives oxygenated blood from the lungs through the______?
After blood is reoxygenated in the lungs, it flows freely from the four pulmonary veins into the left atrium.
Blood then flows through an opened mitral valve into the left ventricle during ventricular diastole
With systolic contraction, the left ventricle generates enough pressure to close the mitral valve and open the aortic valve. Blood is then propelled into the aorta and into the systemic arterial circulation.
The right ventricle sends deoxygenated blood through the______?
*The right ventricle is small and thin walled because it contracts against minimal pressure
The left ventricle pumps oxygenated blood through_____?
the systemic circuit
*The left ventricle is more muscular and thick walled because it contracts against relatively high pressure
There are four cardiac valves responsible for maintaining the forward flow of blood through the chambers of the heart. The cardiac valves are classified into what two types?
- *Atrioventricular (AV) Valves
- -tricuspid valve
- -mitral (bicuspid) valve
- *Semilunar Valves
- -pulmonic valve
- -aortic valve
Describe the blood flow through the heart and valves (easy version)?
- The superior and inferior vena cava, and veins and sinuses within the heart itself dump deoxygenated blood into the right atrium.
It goes from the right atrium to the right ventricle to the lungs.
Oxygenated blood returns to the left atrium to the left ventricle then out to the body
- *How does it get from atrium to venticle on both sides? Toliet Paper My Ass
- Tricuspid, Pulmonic, Mitral (bicuspid), Aortic
Describe in detail how blood flows through the heart and valves?
The Pathway of Blood to and from the Heart
- 1. Blood that has circulated through the body, which has lost its oxygen
- and collected carbon dioxide, enters through the vena cava into the
- right atrium of the heart.
2. The right atrium contracts (atrial systole) and pumps the blood through the tricuspid valve and into the right ventricle.
- 3. The right ventricle then pumps blood through the pulmonary artery
- into the lungs.
- 4. In the lungs, tiny blood vessels called capillaries absorb carbon dioxide
- from the blood and replace it with oxygen.
- 5. Oxygenated blood then flows through the pulmonary vein and into
- the left atrium.
- 6. Oxygenated blood then pumps through the mitral valve and into the
- left ventricle.
- 7. The left side of the heart contracts the strongest to send blood out the
- left ventricle and through the aortic arch on its way to all parts of the
- body. At this point, there are a few options for the blood flow...blood
- can be pumped
- • through the carotid artery and into the brain.
- • through the auxiliary arteries and into the arms.
- • through the aorta and into the torso and legs.
- 8. Blood will then move through the arteries, then through capillaries,
- and then return through the veins.
9. Deoxygenated blood will then return to the heart, and the cycle repeats.
Which valve separates the left atrium and left ventricle?
- The Mitral (bicuspid) Valve separates the LA and LV
Which valve separates the right atrium and right ventricle?
The Tricuspid valve separates the the RA and RV (Tri Right)
Which valve separates the right ventricle and pulmonary artery?
The pulmonic valve separates the right ventricle and pulmonary artery
There are three types of blood vessels: arteries, veins, and capillaries. Arteries and veins are similar in that they have what three layers?
- Intima: the inner lining composed of a layer of endothelial cells next to the blood and an elastic layer that joins the media
- Media: the middle layer of muscle and elastic tissue
- Adventitia: the outer layer of connective tissue
Blood vessel walls are composed of two types of cells: smooth muscle cells and endothelial cells. What are the functions of these cells?
- Smooth muscle cells: maintain blood pressure and blood flow. It contracts and relaxes in response to numerous stimuli, including local and circulating mediators.
- *Overall, regulation of tone in vascular smooth muscle depends on the intracellular concentration of calcium ions. Increased intracellular calcium leads to increased vascular tone.
- Endothelial cells: one function is structural, in which the cells act as a permeability barrier and regulate passage of molecules and cells acoss the blood vessel wall
- The second function is metabolic, in which the cells secrete opposing mediators that maintain a balance between bleeding and clotting of blood, constriction and dilation of blood vessels, and promotion and inhibition of vascular cell growth and inflammation
What is a major determinant of blood pressure?
Peripheral vascular resistance
Arteries contain a layer of smooth muscle (the media) and are sometimes called resistance vessels. Their efficiency depends on their patency and ability to constrict or dilate in response to various stimuli.
The degree of constriction or dilation (vasomotor tone) determines peripheral vascular resistance, which is a major determinant of blood pressure.
Which valve separates the left ventricle and aorta?
The aortic valve separates the left ventricle and aorta
Hint: to help remember arteries and veins
- A (arteries) – Away Blood is moving away from the heart.
- V (veins) – Toward Blood is moving toward the heart.
- Capillaries are small blood vessels that connect the arteries and veins.
The left main coronary artery divides into what two branches?
- The left anterior descending (LAD)
- The left circumflex (LCX)
How does the heart receive blood to meet its metabolic needs?
Through the coronary arterial system
*The coronary arteries originate at the base of the aorta in the aortic cusps just beyond the aortic valve
*The left main coronary artery divides into two branches: the left anterior descending (LAD) and the left circumflex coronary artery (LCX)
Coronary artery blood flow to the myocardium occurs primarily during?
Diastole, when coronary vascular resistance is minimized
*To maintain adequate blood flow through the coronary arteries, mean arterial pressure (MAP) must be at least 60-70mm Hg to maintain perfusion of major body organs
The electrophysiologic properties of heart muscle are responsible for regulating heart rate and rhythm. Cardiac muscle cells possess the characteristics of?
Describe the sequence of events during the cardiac cycle?
The phases of the cardiac cycle are related to changes in pressure and volume in the left ventricle during filling (diastole) and ventricular contraction (systole).
Myocardial contraction results from the release of large numbers of calcium ions from the sarcoplasmic reticulum and from the blood. These calcium ions then diffuse into the myofibril sarcomere (the contractile unit of the myocardial cell) which produces myocardial contraction
Cardiac muscle relaxes when calcium ions are pumped back into the sarcoplasmic reticulum, causing a decrease in the number of calcium ions around the myofibrils.
Which phase of the cardiac cycle consists of relaxation and filling of the atria and ventricles?
Which phase of the cardiac cycle consists of the contraction and emptying of the atria and ventricles?
Blood flow from the heart into the systemic arterial circulation is measured clinically as what?
- cardiac output (CO)
- This is the amount of blood pumped from the left ventricle each minute
- *Cardiac output depends on the relationship between heart rate and stroke volume CO=HR x SV
HR X SV=?
Cardiac Output (CO)
- Cardiac output is the amount of blood pumped from the left ventricle each minute
- It depends on the relationship between the heart rate and stroke volume
Heart rate refers to the number of times the ventricles contract each minute. What is the normal resting HR for an adult?
Between 60 and 100 beats/min
The heart rate is extrinsically controlled by ?
Autonomic nervous system (ANS)
The ANS adjusts rapidly when necessary to regulate cardiac output
Which system slows the heart rate?
The parasympathetic (vagus nerve)
The____?____system slows the heart rate, whereas ___?___stimulation increases the heart rate
The parasympathetic (vagus nerve) system slows the HR, whereas sympathetic stimulation increases the HR
An increase in circulating catecholamines (ex: epinephrine and norepinephrine) usually causes an increase in HR and contractility. Many cardiovascular drugs, particularly ? block this sympathetic (fight or flight) pattern by decreasing the HR
The amount of blood ejected by the left ventricle during each contraction is called?
HR, preload, afterload, and contractility influence stroke volume and, ultimately, affecting cardiac output
Refers to the degree of myocardial fiber stretch at the end of diastole and just before contraction?
The stretch imposed on the muscle fibers results from the volume contained within the ventricle at the end of diastole.
Preload is determined by the amount of blood returning to the heart from both the venous system (right heart) and the pulmonary system (left heart) (known as the left ventricular end-diastolic volume)
Preload is the stretch imposed on the muscle fibers caused by the volume contained within the ventricle at the end of diastole.
An increase in ventricular volume increases muscle-fiber length and tension, thereby enhancing contraction and improving stroke volume. Where is this statement derived from?
Starling's law of the heart: The more the heart is filled during diastole, the more forcefully it contracts.
What is the pressure or resistance that the ventricles must overcome to eject blood through the semilunar valves and into the peripheral blood vessels?
The amount of resistance is directly related to arterial blood pressure and the diameter of the blood vessels
What affects stroke volume and cardiac output and is the force of cardiac contraction independent of preload?
- Contractility is increased by factors such as sympathetic stimulation, calcium release, and positive inotropic drugs.
- It is decreased by factors such as hypoxia and acidemia
The vascular system serves several purposes such as?
- Provides a route for blood to travel from the heart to nourish various body tissues
- Carries cellular wastes to the excretory organs
- Allows lymphatic flow to drain tissue fluid back into circulation
- Returns blood to the heart for recirculation
*The vascular system is divided into the: arterial system and the venous system
Which system delivers blood to various tissues for oxygen and nourishment, and transport cellular wastes to the excretory organs to be reprocessed or removed?
The arterial system
- At the tissue level, nutrients, chemicals, and body defense substances are distributed and exchanged for cellular waste products
- The arteries then transport the waste to excretory organs like the kidneys and lungs
These vessels also contribute to temperature regulation in the tissues because blood can be either directed toward the skin to promote heat loss or diverted away from the skin to conserve heat.
What is the force of blood exerted against the vessel walls?
- Blood Pressure
- Volume, adequate contracting ventricles, and vascular tone are necessary to maintain blood pressure
- BP is determined primarily by the cardiac output and by the resistance in the arterioles
- Blood pressure=Cardiac output X Peripheral vascular resistance
Any factor that increases cardiac output or total peripheral vascular resistance increases the blood pressure
What three mechanisms mediate and regulate blood pressure?
The autonomic nervous system (ANS), which excites or inhibits sympathetic nervous system activity in response to impulses from chemoreceptors and baroreceptors
The kidneys, which sense a change in blood flow and activate the renin-angiotensin-aldosterone mechanism
The endocrine system, which releases various hormones (e.g., catecholamine, kinins, serotonin, histamine) to stimulate the sympathetic nervous system at the tissue level
The amount of pressure/force generated by the left ventricle to distribute blood into the aorta with each contraction of the heart is called?
Systolic Blood Pressure
It is a measure of how effectively the heart pumps and is an indicator of vascular tone
What is the amount of pressure/force against the aterial walls during the relaxation phase of the heart?
Diastolic Blood Pressure
Blood pressure is regulated by balancing the sympathetic and parasympathetic nervous sysetms of the ANS. Changes in autonomic nervous system activity are responses to messages sent by the sensory receptors in the various tissues of the body.
These receptors, including the baroreceptors, chemoreceptors, and stretch receptors, respond differently to the biochemical and physiologic changes of the body.
Explain Baroreceptors and chemoreceptors
- Baroreceptors: located in the arch of the aorta and internal carotid arteries. Baroreceptors are stimulated when the arterial walls are stretched by an increased blood pressure. Impulses from these baroreceptors inhibit the vasomotor center located in the pons and medulla.
- Inhibition of the vasomotor center drops blood pressure
- Peripheral chemoreceptors: are located in the carotid arteries and along the aortic arch
- These receptors are sensitive to hypoxemia (decreased O2). When stimulated, these chemoreceptors send impulses along the vagus nerves to activate a vasoconstrictor response and raise blood pressure
The central chemoreceptors in the respiratory center of the brain are stimulated by hypercapnia (increased CO2) and acidosis *CO2 has a stronger effect on the CNS than hypoxia
- Stretch receptors: located in the vena cava and right atrium are sensitive to pressure or volume changes.
- When a patient is hypovolemic, stretch receptors in the blood vessels sense a reduced volume or pressure and send fewer impulses to the CNS.
- This reaction stimulates the sympathetic nervous system to increase the heart rate and constrict the peripheral blood vessels which increases blood pressure
How do the kidneys help regulate cardiovascular activity?
- When renal blood flow or pressure decreases, the kidneys retain sodium and water.
- Blood pressure rises because of fluid retention and activation of the renin-angiotensin-aldosterone mechanism which results in vasoconstriction and sodium retention (thus fluid retention).
Vascular volume is also regulated by the release of antidiuretic hormone (vasopressin) from the posterior pituitary gland
What is the primary function of the venous system?
To complete the circulation of blood by returning blood from the capillaries to the right side of the heart
- Veins have the ability to accommodate large shifts in volume with minimal changes in venous pressure.
- This is what allows the administration of IV fluids and blood transfusions, as well as to maintain pressure during blood loss and dehydration.
All veins in the superficial and deep venous systems in the legs (except the smallest and the largest veins) have valves that direct blood flow back to the heart; this prevents retrograde flow (backflow). What is the force that pushes the blood forward in the veins?
Skeletal muscles in the extremities.
The superior and inferior vena cava do not have valves, which allows unimpeded blood flow return to the heart
Describe the changes to cardiac valves related to aging
Calcification and mucoid degeneration occur, especially in mitral and aortic valves
- Nursing Interventions:
- -Assess heart rate and rhythm and heart sounds for murmurs (murmurs may be detected before other symptoms. Valvular abnormalities may result in rhythm changes)
- -Ask patient about dyspnea
Describe changes in the conduction system related to aging
- Pacemaker cells decrease in number. Fibrous tissue and fat in the SA node increase
- Few muscle fibers remain in the atrial myocardium and bundle of His.
- Conduction time increases
- Nursing Interventions:
- Assess the ECG and heart rhythm for dysrhythmias or a heart rate less than 60 beats/min (The SA node may lose its inherent rhythm)
- (Atrial dysrhythmias occur in many older adults; 80% of older adults experience premature ventricular contractions or PVCs)
Describe changes in the left ventricle related to aging
- The size of the left ventricle increases
- The left ventricle becomes stiff and less distensible
- Fibrotic changes in the left ventricle decrease the speed of early diastolic filling by about 50%
- Nursing Interventions
- -Assess the ECG for a widening QRS complex and a longer QT interval. (Ventricular changes result in decreased stroke volume, ejection fraction, and cardiac output during exercise; the heart is less able to meet increased oxygen demands)
- -Assess the heart rate at rest and with activity (Maximum heart rate with exercise is decreased)
- -Assess for activity intolerance (The heart is less able to meet increased oxygen demands)
Describe changes in the aorta and other large arteries related to aging
The aorta and other large arteries thicken and become stiffer and less distensible. Systolic blood pressure increases to compensate for the stiff arteries
Systemic vascular resistance increases as a result of less distensible arteries; therefore the left ventricle pumps against greater resistance, contributing to left ventricular hypertrophy
- Nursing Interventions:
- -Assess blood pressure (Hypertension may occur and must be treated to avoid target organ damage)
- -Assess for activity intolerance and shortness of breath
- -Assess the peripheral pulses
Describe changes to baroreceptors related to aging
Baroreceptors become less sensitive
- Nursing Interventions:
- -Assess blood pressure lying and then sitting or standing (Orthostatic postural and postprandial changes occur because of ineffective baroreceptors)
- -Assess for dizziness when patient changes from a lying to a sitting or standing position (Changes may include blood pressure decreases of 10mm Hg or more, dizziness, and fainting)
- -Teach patient to change positions slowly
Heart valves: closure sequence
- "Many Things Are Possible"
- Mitral, Tricuspid, Aortic, Pulmonic
Heart valve auscultation sites
- "All Prostitutes Take Money"
- Aortic (RUSB)
- Pulmonary (LUSB)
- Tricuspid (LLSB)
- Mitral (Apex)
Lung lobe numbers: right vs. left
Tricuspid heart valve and tri-lobed lung both on the right side
Bicuspid and bi-lobed lung both on the left side
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