A&P II The Cardiovascular System: The Heart
The study of the normal heart and diseases associated with it.
What is the location and size of the heart?
*The heart is situated between the lungs in the mediastinum.
*About two-thirds of its mass is to the left of the midline.
*The heart is about 12 cm long, 9 cm wide, and 6 cm thick.
The heart is enclosed and held in place by the _____.
What does the pericardium consist of?
*an outer fibrous pericardium
*an inner serous pericardium
What is the serous pericardium composed of?
*a parietal layer
*a visceral layer
What is between the parietal and visceral layers of the serous pericardium?
The pericardial cavity, a potential space filled with pericardial fluid that reduces friction between the two membranes.
An inflammation of the pericardium is known as _____.
Pericarditis- associated bleeding into the pericardial cavity compresses the heart(cardiac tamponade) and is potentially lethal.
What are the three layers of the wall of the heart?
The epicardium consists of what?
mesothelium and connective tissue(thin layer of simple squamous epithelium)
The myocardium is composed of what?
cardiac muscle tissue
The endocardium consists of what?
endothelium and connective tissue(simple squamous epithelium with a thin basal membrane)
What do the chambers of the heart include?
*two upper atria
*two lower ventricles
An _____ _____ separates the atria.
An _____ _____ separates the ventricles.
Blood flows through the heart from the (1)_____ and _____ _____ _____ and the (2)_____ _____ to the (3)_____ _____, through the (4)_____ _____ to the (5)_____ _____,through the (6)_____ _____ and (7)_____ _____ to the lungs, through the (8)_____ _____ into the (9)_____ _____, through the(10)_____ _____ to the (11)_____ _____, and out through the (12)_____.
(1)superior and inferior venae cavae
What are the divisions of the aorta?
*arch of the aorta
What prevents backflow of blood in the heart, and what are they composed of?
Valves, composed of dense connective tissue covered by endothelium.
What is between the atria and their ventricles?
-tricuspid valve:on the right side of the heart
-bicuspid(mitral)valve:on the left
The _____ _____ and their _____ _____ keep the flaps of the valves pointing in the direction of the blood flow and stop blood from backing into the atria.
Chordae tendineae and their papillary muscles
(1)_____ _____ prevent blood from flowing back into the heart as it leaves the heart for the lungs (2)(_____ _____ _____) or for the rest of the body(3)(_____ _____ _____)
(2)pulmonary semilunar valve
(3)aortic semilunar valve
_____ _____ is precipitated by infection with group A, B-hemolytic strains of Streptococcus pyogenes bacteria.What is the ultimate result of this?
The ultimate result is damage to valves of the heart, most commonly the bicuspid and aortic semilunar valves.
The flow of blood through the many vessels that pierce the myocardium of the heart is called the _____(_____)_____. What is the purpose of this?
It delivers oxygenated blood and nutrients to the myocardium and removes carbon dioxide and wastes from it.
The principle arteries, branching from the ascending aorta and carrying oxygenated blood, are the (1)_____ and _____ _____ _____; deoxygenated blood returns to the right atrium primarily via the principle vein, the (2)_____ _____.
(1)right and left coronary arteries
Most heart problems result from faulty coronary circulation due to what?
*fatty atherosclerotic plaques
*spasms of the smooth muscle in coronary artery walls
Complications of the coronary(cardiac)circulation system include ...
*angina pectoris- severe pain that accompanies reduced blood flow, or ischemia, to the myocardium
*myocardial infarction(MI, or heart attack, in which there is death of an area of the myocardium due to an interruption of the blood supply; it may result from a thrombus or embolus
Whenever a disease or injury deprives a tissue of oxygen, reestablishing the blood flow(reperfusion) may damage the tissue further due to the formation of _____ _____ _____;these can destabilize the molecular structure of proteins,neurotransmitters,nucleic acids,and phospholipids of plasma membranes.
Oxygen free radicals
What does the conduction system consist of?
Tissue specialized for generation and conduction of spontaneous action potentials that stimulate the cardiac muscle fibers(cells) to contract.
What are the components of the conduction system?
*Atrioventricular(AV)bundle(bundle of His)
*Right and Left bundle branches
*Conduction myofibers(Purkinje fibers)
What are signals from the autonomic nervous system and hormones ,such as epinephrine, responsible for and not responsible for?
*They DO modify the heartbeat(in terms of rate and strength of contraction)
*They DO NOT establish the fundamental rhythm.
What can an artificial pacemaker used for?
To restore cardiac rhythm due to disruption of some component of the conduction system.
What is an impulse in a ventricular contractile fiber characterized by?
The _____ _____ of a cardiac muscle fiber(the time interval when a second contraction cannot be triggered)is longer than the contraction itself.
Impulse conduction through the heart generates electrical currents that can be detected at the surface of the body. A recording of the electrical changes that accompany each cardiac cycle(heartbeat) is called an _____.
Electrocardiogram(ECG or EKG)-measures rate and rhythm
Does not tell anything about valves or heart murmurs)
What does a normal ECG consist of?
*P wave(atrial depolarization-spread of impulse from SA node over atria)
*QRS complex(ventricular depolarization-spread of impulse through ventricles)
*T wave(ventricular repolarization)
What interval represents the conduction time from the beginning of atrial excitation to the beginning of ventricular excitation?
The P-Q(PR) interval
What segment represents the time when ventricular contractile fibers are fully depolarized during the plateau phase of the impulse.
The S-T segment
A cardiac cycle consists of what?
the systole(contraction) and diastole(relaxation) of both atria, rapidly followed by the systole and diastole of both ventricles
What are the phases of the cardiac cycle?(mechanical)
(1)the relaxation(or quiescent)period(refractory)
(3)ventricular systole(full depolarization or systole)
With an average heart rate of 75 beats/min, what does a complete cardiac cycle require?
What does the sound of a heartbeat primarily come from?
The turbulence in blood flow caused by the CLOSURE of the valves, not from the contraction of the heart muscle.
What is the first heart sound(S1-LUBB) created by?
Blood turbulence associated with the closing of the atrioventricular valves soon after systole begins.
(long,loud,low-closing of the AV valves)
What does the second heart sound(S2-DUPP)represent?
The closing of the semilunar valves close to the end of ventricular systole.
(short,sharp,high pitches-closure of semilunar valves)
A _____ _____ is an abnormal sound that consists of a flow noise that is heard before, between, or after the LUBB-DUPP or that may mask the normal sounds entirely.
What are some murmurs caused by?
turbulent blood flow around valves due to abnormal anatomy or increased volume of flow
Not all murmurs are abnormal or symptomatic, but most indicate what?
a valve disorder
What are 5 valvular disorders that may contribute to murmurs?
1. mitral stenosis
2. mitral insufficiency
3. aortic stenosis
4. aortic insufficiency
5. mitral valve prolapse(MVP)
_____ _____ is the amount of blood ejected by the left ventricle(or right ventricle) into the aorta(or pulmonary trunk) per minute.
What is the formula to find cardiac output?
Cardiac output = stroke volume x beats per minute
CO = SV x BPM
_____ _____ is the amount of blood ejected by a ventricle during each systole.
What does the stroke volume depend on?
How much blood enters a ventricle during diastole,that is, the stretch on the heart before it contracts , and how much blood is left in a ventricle following its systole.
EDV averages 120.130 ml and SV is about 70 ml; ESV, then is approimately 50-60 ml.
Stroke volume is also related to (1)_____ and (2)_____;factors that increase the stroke volume or heart rate tend to increase CO and visa versa.
(1)contractility - forcefulness of contraction at any given time
(2)afterload - pressure that must be exceeded before ventricular ejection can occur
What is the formula to find stroke volume?
SV = EDV - ESV
EDV:end-diastolic volume,also called preload
_____ _____ is the ratio between the maximum cardiac output a person can achieve and the cardiac output at rest.
What does the Frank-Sterling law of the heart state?
A greater preload(stretch)on cardiac muscle fibers just before they contract increases their force of contraction during systole.
_____ _____ _____ results when the heart cannot supply the oxygen demands of the body.
Congestive heart failure(CHF)
What is congestive heart failure characterized by?
Diminished blood flow to the various tissues of the body and by accumulation of excess blood in the various organs because the heart is unable to pump out the blood returned to it by the great veins.
What are two causes of congestive heart failure?
*myocardial infarction(heart attack)
What is the body's principal mechanism of short-term control over cardiac output and blood pressure?
Changing heart rate
Nervous system control of the cardiovascular system stems from the cardiovascular center in the _____.
(1)_____ impulses increase heart rate and force of contraction; (2)_____ impulses decrease heart rate
_____ are nerve cells that respond to changes in blood pressure and relay the information to the cardiovascular center.
Where are important baroreceptors located?
In the arch of the aorta and carotid arteries.
Name 6 things heart rate is affected by.
(1) hormones(epinephrine,norepinephrine,thyroid hormones)
(5) physical fitness
Although a variety of drugs are helpful in the earlier stages of heart disease, at some point they are no longer effective. Why?
Because there is too little functional cardiac muscle left.
Researchers are investigating a wide variety of devices and techniques used to aid a failing heart. Name 3.
*cardiac assist devices
What are 5 risk factors in heart disease that can be modified?
(1)high blood cholesterol level
(2)high blood pressure
(5)lack of regular exercise
What are 5 risk factors in heart disease that cannot be modified?
(4)high blood levels of fibrinogin, renin, and uric acid
(5)left ventricular hypertrophy
A strong risk factor for developing heart disease is high blood cholesterol level. Why?
The reason is that high blood cholesterol promotes growth of fatty plaques that build up in the walls of arteries.
Most lipids are transported in the blood in combination with proteins as _____.
What are the three classes of lipoproteins called?
*high-density lipoproteins (HDLs)
*very low-density liporoteins(VLDLs)
What are the HDLs associated with?
The removal of excess cholesterol from circulation.
What are high levels of LDLs associated with?
The formation of fatty plaques in arteries.
What do VLDLs also contribute to?
Increased fatty plaque formation.
There are two sources of cholesterol in the body, where are they?
(1)some are present in foods we ingest
(2)most are synthesized by the liver
True or False. For adults, desirable levels of blood cholesterol are TC (total cholesterol) under 200mg/dl, LDL under 130 mg/dl, and HDL over 60 mg/dl; Normally, triglycerides are in the range of 10-190mg/dl.
What are three therapies used to reduce blood cholesterol levels?
When does the heart develop from mesoderm?
Before the end of the third week of gestation.
The _____ _____ develop into the four-chambered heart and great vessels of the heart.
_____ _____ _____ or, _____ _____ _____,is a condition in which the heart muscle receives an inadequate amount of blood due to obstruction of its blood supply.
Coronary artery disease(CAD), or Coronary heart disease(CHD)
_____ is a process in which smooth muscle cells proliferate and fatty substances, especially cholesterol and triglycerides(neutral fats), accumulate in the walls of medium-sized and large arteries in response to certain stimuli, such as endothelial damage.
_____ _____ _____ is a condition in which the smooth muscle of a coronary artery undergoes a sudden contraction, resulting in narrowing of a blood vessel.
Coronary artery spasm
A _____ _____ is a defect that exists at birth, and usually before birth.
Name 5 congenital defects of the heart.
*coarctation of the aorta
*patent ductus arteriosus
*septal defects(interatrial or interventricular)
*tetralogy of Fallot
An _____ is an abnormality or irregularity in the heart rhythm resulting from a disturbance in the conduction system of the heart, due either to faulty production of electrical impulses or to poor conduction of impulses as they pass through the system.
What are examples of arrhythmias?
*heart block(most commonly atrioventricular block)
*fibrillation(atrial and ventricular)
*premature ventricular contraction(PVC)