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Chapter 20 The Cardiovascular System: The Heart
Terms in this set (37)
Where is the majority of the heart's mass located?
It lies to the left of the midline
What is the covering that surrounds the heart?
What are the layers of the pericardium?
1) the fibrous pericardium: composed of tough, inelastic, dense irregular connective tissue.
2) the serous pericardium: (deep) forms a double layer around the heart
What are 2 layers of the Serous Pericardium?
1) Parietal layer: (outer) is fused to the fibrous pericardium
2) Visceral layer: (inner, also called the epicardium) is one of the layers of the heart wall and adheres tightly to the surface of the heart
What is the paracardial cavity?
It is located between the parietal and visceral layers of the serous paricardium. It contains a thin film of lubricating fluid
What is the purpose of paracardial fluid?
It reduces friction between the layers of the serous pericardium as the heart moves
What are the 3 heart wall layers?
Epicardium (or visceral layer), Myocardium, and Endocardium
What is the structure of the Epicardium?
It is composed of 2 tissue layers. The outermost is the visceral layer of the serous pericardium which is composed of mesothelium. The inner layer is a variable layer composed of fibroelastic tissue and adipose tissue
What is the structure of the Myocardium?
Is the thickest layer of the 3 and is composed of muscle tissue
What is the structure of the Endocardium?
Is composed of a thin layer of endothelium overlying a thin layer of connective tissue.
Name the 4 valves in the heart?
Atrioventricular (tricuspid, bicuspid), Semilunar (pulmonary, aortic)
What are the differences between atrioventricular valves and semilunar valves?
Atrioventricular valves are thin structures composed of endocardium and connective tissue. Semilunar valves are flaps of endocardium and connective tissue reinforced by fibers to prevent turning inside out.
What are chordae tendinae?
Tendon like cords that connect the cusps of the tricuspid valve
What are papillary muscles?
Cone shaped raised bundles of cardiac fibers (trabeculae carneae) that the chordae tendinae connect to
What structure separates the left and right chambers of the heart?
The interatrial septum and the interventricular septum
Identify and describe the auricle
It is located on the anterior surface of each atrium. It is a wrinkled pouchlike structure
Identify and describe the pectinate muscles
They are located on the inside of the anterior wall. Rough muscular ridges.
Identify and describe the trabeculae carneae
They are located on the inside of the right ventricle. A series of ridges formed by raised bundles of cardiac muscle fibers.
Which chamber of the heart has the thickest wall? Why?
The left ventricle. Because it needs to pump blood to most of the body while the right ventricle only pumps to the lungs.
How is the heart supplied with O2 and nutrients?
Blood leaves the aorta to the right and left coronary arteries which circle the heart like a crown. The coronaries branch off to supply all areas of the heart with O2 and nutrients. Deoxygenated blood returns from the outside of the heart thru the coronary sinus
Describe the characteristics of cardiac muscle
Usually 1 nucleus. The ends of cardiac muscle fibers are connected by irregular thickenings of the sarcolemma called intercalated discs. Which contain desosomes which hold the fibers together. Gap junctions allow muscle action potentials to conduct from 1 muscle fiber to another.
What are the 2 types of cells located within the heart?
1) Autorhythmic fibers: do not do work, generate electricity
2) Contractile fibers: the working atrial and ventricular muscle fibers
Describe the specialized properties of the autoryhythmic fibers
1) act as a pacemaker, set the rhythm of electrical excitation that causes heart contractions
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 thru heart
Describe how electrical current is conducted across the heart to initiate atrial and ventricular conctraction
Sinoatrial node (SA) --> Atrioventricular node (AV) --> Atrioventricular bundle --> to RT & LT bundle branches --> Purkinje fibers
Where is the SA node located and what is its function?
Located in the RT atrial wall, inferior and lateral to the opening of the superior vena cava. It repeatedly depolarizes threshold creating a pacemaker potential.
Where is the AV node located and what is its function?
Located in the interatrial septum anterior to the opening of the coronary sinus. Action potential slows allowing atria to empty blood into ventricles
What is the function of the AV bundles?
The only place that action potentials can conduct from the atria to the ventricles
What is the function of the Purkinje fibers?
They rapidly conduct the action potential beginning at the apex of the heart upward to the remainder of the ventricular myocardium
Why is the absolute refractory period in the heart longer than skeletal muscle
effective refractory period acts as a protective mechanism and keeps the heart rate in check and prevents arrhythmias and coordinates muscle contraction. Anti-arrhytmic agents used for arrhythmias usually prolong the ERP.
What is electrocardiography?
recording of electrical events of the heart
What are the 3 deflection waves of ECG
Pwave: depolarization wave passing over the atria
QRS Complex: depolarization wave passing over ventricles. atria repolarization
Twave: repolarization of ventricles
What is cardiac output?
the amount of blood ejected thru each ventricle per minute
What events in the heart correspond to 2 audible heart beats?
Lubb- atriolventricular valves shut
Dubb- semilumar valves shut
What is stroke volume?
end diastolic volume - end systolic volume
How do you calculate cardiac output?
CO = Heart rate x Stroke volume
What is end diastolic volume?
is the volume of blood in the right and/or left ventricle at end load or filling in
What is end systolic volume?
is the volume of blood in a ventricle at the end of contraction, or systole, and the beginning of filling
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