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Related Concept Videos

Heart Valves01:16

Heart Valves

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The human heart is a complex organ with an intricate system of valves that regulate blood flow. There are two main types of valves: atrioventricular (AV) valves and semilunar valves.
The AV valves prevent the backflow of blood from the ventricles to the atria during ventricular contraction. These valves function with the assistance of the chordae tendineae and papillary muscles. When the ventricles are relaxed, the chordae tendineae are slack, allowing blood to flow from the atria into the...
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What is Variation?01:14

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Apart from the measures of central tendency, distribution, outliers, and the changing characteristics of data with time, an important characteristic of any data set is its variation or spread. In some data sets, the data values are concentrated closely near the mean; in others, the data values are more widely spread out from the mean.
The range, standard deviation, standard error, and variance are the different measures of variation.
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Anatomy of the Heart01:27

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The human heart is made up of three layers of tissue that are surrounded by the pericardium, a membrane that protects and confines the heart. The outermost layer, closest to the pericardium, is the epicardium. The pericardial cavity separates the pericardium from the epicardium. Beneath the epicardium is the myocardium, the middle layer, and the endocardium, the innermost layer. There are four chambers of the heart: the right atrium, the right ventricle, the left atrium, and the left ventricle.
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Variation01:19

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An important characteristic of any set of data is the variation in the data. In some data sets, the data values are concentrated closely near the mean; in other data sets, the data values are more widely spread out from the mean. The most common measure of variation, or spread, is the standard deviation, which is the square root of variance.
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Because the DNA segments are cut and reorganized in a direction-specific manner, site-specific recombination has emerged as an efficient genetic engineering technique. Flippase and Cyclization recombinases or Flp and Cre, respectively, are two members of the tyrosine recombinase family derived from bacteriophages, that are used to mediate site-specific DNA insertions, deletions, and targeted expression of proteins in mammalian cell lines.
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Change in atmospheric pressure with height is particularly interesting. The decrease in atmospheric pressure with increasing altitude is due to the decreasing gravitational force per unit area as we move away from the surface of the earth.
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Related Experiment Video

Updated: Jan 25, 2026

A Simplified Model for Heterotopic Heart Valve Transplantation in Rodents
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Significant variation in heart valve banking practice.

Sharon Zahra1, George Galea2, Ramadan Jashari3

  • 1Scottish National Blood Transfusion Service, The Jack Copland Centre, 52 Research Avenue North, Heriot-Watt Research Park, Edinburgh, EH14 4BE, UK. szahra@nhs.net.

European Journal of Clinical Microbiology & Infectious Diseases : Official Publication of the European Society of Clinical Microbiology
|May 14, 2019
PubMed
Summary
This summary is machine-generated.

High heart valve (HV) discard rates persist globally, with microbiology and anatomical factors being key causes. Standardizing HV banking practices is crucial to reduce waste and improve tissue availability.

Keywords:
DiscardHeart valvesMicrobiologyTransplantation

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Area of Science:

  • Cardiovascular Surgery
  • Tissue Banking
  • Transplantation Medicine

Background:

  • The European Blood Alliance (EBA) identified significant heart valve (HV) discard rates (19-65%) in 2014.
  • Variations in tissue establishment (TE) processing methodologies contribute to high discard rates.

Purpose of the Study:

  • To conduct a worldwide data-gathering exercise on HV processing.
  • To assess current HV processing methodologies and identify causes for discard.
  • To provide data supporting the standardization of HV banking.

Main Methods:

  • A global questionnaire on HV processing was distributed to TEs.
  • Nineteen questionnaires were collected from 15 European and 4 non-European TEs.
  • Data on discard rates, causes, and processing variations were analyzed.

Main Results:

  • In 2015, discard rates were 43-50% for aortic valves and 20-32% for pulmonary valves.
  • Primary discard reasons included microbiological contamination, anatomical issues, and medical factors.
  • Significant practice variations were observed in donor assessment, timings, rinsing, decontamination, and microbiological testing.

Conclusions:

  • Substantial variations in HV banking practices exist worldwide.
  • Standardization of HV banking procedures is necessary to reduce discard rates.
  • This study represents a foundational step towards global standardization in HV banking.