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When the ventricles begin to contract, pressure within the ventricles rises and blood flows toward the area of lowest pressure, which is initially in the atria. This backflow causes the cusps of the tricuspid and mitral (bicuspid) valves to close. These valves are tied down to the papillary muscles by chordae tendineae. During the relaxation phase of the cardiac cycle, the papillary muscles are also relaxed and the tension on the chordae tendineae is slight (see [link] b ). However, as the myocardium of the ventricle contracts, so do the papillary muscles. This creates tension on the chordae tendineae (see [link] b ), helping to hold the cusps of the atrioventricular valves in place and preventing them from being blown back into the atria.

The aortic and pulmonary semilunar valves lack the chordae tendineae and papillary muscles associated with the atrioventricular valves. Instead, they consist of pocket-like folds of endocardium reinforced with additional connective tissue. When the ventricles relax and the change in pressure forces the blood toward the ventricles, the blood presses against these cusps and seals the openings.

Visit this site to observe an echocardiogram of actual heart valves opening and closing. Although much of the heart has been “removed” from this gif loop so the chordae tendineae are not visible, why is their presence more critical for the atrioventricular valves (tricuspid and mitral) than the semilunar (aortic and pulmonary) valves?

Disorders of the…

Heart valves

When heart valves do not function properly, they are often described as incompetent and result in valvular heart disease, which can range from benign to lethal. Some of these conditions are congenital, that is, the individual was born with the defect, whereas others may be attributed to disease processes or trauma. Some malfunctions are treated with medications, others require surgery, and still others may be mild enough that the condition is merely monitored since treatment might trigger more serious consequences.

Valvular disorders are often caused by carditis, or inflammation of the heart. One common trigger for this inflammation is rheumatic fever, or scarlet fever, an autoimmune response to the presence of a bacterium, Streptococcus pyogenes , normally a disease of childhood.

While any of the heart valves may be involved in valve disorders, mitral regurgitation is the most common, detected in approximately 2 percent of the population, and the pulmonary semilunar valve is the least frequently involved. When a valve malfunctions, the flow of blood to a region will often be disrupted. The resulting inadequate flow of blood to this region will be described in general terms as an insufficiency. The specific type of insufficiency is named for the valve involved: aortic insufficiency, mitral insufficiency, tricuspid insufficiency, or pulmonary insufficiency.

If one of the cusps of the valve is forced backward by the force of the blood, the condition is referred to as a prolapsed valve. Prolapse may occur if the chordae tendineae are damaged or broken, causing the closure mechanism to fail. The failure of the valve to close properly disrupts the normal one-way flow of blood and results in regurgitation, when the blood flows backward from its normal path. Using a stethoscope, the disruption to the normal flow of blood produces a heart murmur.

Stenosis is a condition in which the heart valves become rigid and may calcify over time. The loss of flexibility of the valve interferes with normal function and may cause the heart to work harder to propel blood through the valve, which eventually weakens the heart. Aortic stenosis affects approximately 2 percent of the population over 65 years of age, and the percentage increases to approximately 4 percent in individuals over 85 years. Occasionally, one or more of the chordae tendineae will tear or the papillary muscle itself may die as a component of a myocardial infarction (heart attack). In this case, the patient’s condition will deteriorate dramatically and rapidly, and immediate surgical intervention may be required.

Auscultation, or listening to a patient’s heart sounds, is one of the most useful diagnostic tools, since it is proven, safe, and inexpensive. The term auscultation is derived from the Latin for “to listen,” and the technique has been used for diagnostic purposes as far back as the ancient Egyptians. Valve and septal disorders will trigger abnormal heart sounds. If a valvular disorder is detected or suspected, a test called an echocardiogram, or simply an “echo,” may be ordered. Echocardiograms are sonograms of the heart and can help in the diagnosis of valve disorders as well as a wide variety of heart pathologies.

Questions & Answers

information for blood vessels
Sumit Reply
helps pump blood through body
scott
arteries carry blood away from the heart while veins return it to the heart
Reverian
veins have thinner outer walls because blood pressure in them is very low compared to arteries with thicker outer walls to withstand the higher blood pressure.
Oliver
cell, tissue, organ, organism, organ system,
Gheida Reply
please what are the characteristics of a good respiratory system?
Salomon Reply
thin wall ,a moist inner surface ,a huge combined surface area and a rich blood supply.
Nchimunya
Help me am confused what is the cell membrane as a partially permeable membrane
Janelle Reply
it is the ability of a molecules to cross a cell membrane depending on their both size and chemical properties.
Andrews
Based on my previous understanding of biological systems, a cell membrane is a semi-permeable membrane made up of a phospholipids bi-layer. The polar head consisting of phosphate and the hydrophobic end made up of lipids.
Abayomi
Smallest bone of rabbit is
Sahrukh Reply
difference between catebolism and anebolism
Anthvanath Reply
identify the causes of infertility in human beings
Rodrick Reply
Describe how a healthy pregnancy could be maintained
Rodrick
Huaman largest bone
Sahrukh
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Salamin Reply
Samllest bone
Sahrukh
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AlfredOfficial Reply
by DNA tests
lasford
thanks
AlfredOfficial
How to test
Salamin
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R.k Reply
208
Rani
A baby's body has about 300 bones at birth. These eventually fuse (grow together) to form the 206 bones that adults
Manali
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R.k
A baby's body has about 300 bones at birth. These eventually fuse (grow together) to form the 206 bones that adults h
Manali
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R.k
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Manali
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R.k
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Manali
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Rani
it's 300 bones because it a baby
Jasper
babies have 300 bones in which it fuses to become 206 as an adult.
Andrews
it has 300 bones ,nchimunya
Nchimunya
figure of male reproduction
Rani Reply
front view of male reproductive system
Rani
front view of male reproductive system
Rani
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Rhonda Reply
Actin is a family of globular multi-functional proteins that form microfilaments. 
Lauren
difference between throat and lyrnx
Lone
what is the difference between a vaccine and a antiserum
Silver Reply
An antiserum contains antibodies already produced and is used to pass on immune responses. A vaccine contains a substance that stimulates the production of antibodies to create an immune response.
Nana
A vaccine a preparation of antigens for one (or more) diseases that is given to stimulate active immunity and protect against the disease (s). while an antiserum either neutralizes the "infection " or stimulates your immune system to attack an infection.
Oliver
what is deoxyribonucleic acid
Carlene Reply
A negatively charged molecule; polymer of nucleotides found in the nucleus of a cell ... DNA.
Abayomi
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Asali
Hi
Janelle
hi
Oliver
hello
Rani
how are you doing?
Jasper
DNA is genetic material which is present in cell DNA is made up of nitrogen base,phosphate group and pentose sugar.
Manali
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Jasper
give a front view of male reproductive system
Rani
to maintain certain biological activities of cell
jeeni Reply

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Source:  OpenStax, Human biology. OpenStax CNX. Dec 01, 2015 Download for free at http://legacy.cnx.org/content/col11903/1.3
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