Answer:
B) The "lub-dub" sound originates from blood turbulence through the heart.
Explanation:
The systole and diastole in the heart produce the lub and dub sound in the heart.
The systole represents the contraction of both left and right ventricles and pumps the blood to the body and the right ventricle to the lungs. This involves the opening and closing of the valves. The closing of the atrioventricular valves produces lub sound.
At the end of the systole or ventricular contraction or when the blood has been pumped to the aorta and the pulmonary valves then the semilunar valves present in the aorta and pulmonary closes. This produces a sound dub.
Therefore,lub dub is associated with the physical contraction of the heart but not the turbulence of the blood.
Thus, the selected option is the correct answer.
When every dilution of your sample results in a plate that is too few to count we should filter the original sample and use most probable number method .
Probable number method count and determine the number of bacteria in a culture, plate aliquots of the dilutions onto agar with sterile pipettes, spread with glass sticks, incubate at 37°C and count the number of colonies. It is imperative that you utilize your best culture technique.
Not all bacterial cells produce colonies, as some bacteria tend to clump or aggregate, and some are nonviable. For this reason results are reported as colony forming units (CFU)/ml of bacterial culture. Ideally only plates with 25-250 colonies are used.
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The United States flag will always go on top. Typically you leave approximately one foot of space between the United States flag and the flag underneath.
Farming meant that people did not need to travel to find food.( nomadic lifestyles became scarce) Instead, they began to live in settled communities,or villages and grew crops or raised animals on nearby land. They built stronger, more permanent homes and surrounded their settlements with walls to protect themselves.
