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The endocardial endothelium may also act as a kind of blood–heart barrier (analogous to the blood–brain barrier), thus controlling the ionic composition of the extracellular fluid in which the cardiomyocytes bathe.
Endocardial cushions, or atrioventricular cushions, refer to a subset of cells in the development of the heart that play a vital role in the proper formation of the heart septa. They develop on the atrioventricular canal [2] and conotruncal region of the bulbus cordis. [3] During heart development, the heart starts out as a tube. As heart ...
The endocardial tubes have an intimate proximity to the foregut or pharyngeal endoderm. [ 1 ] As folding of the embryo in the horizontal plane initiates in the 4th week of gestation, the endocardial tubes meet in the midline to form the primitive heart tube , which will eventually develop into the histologically definitive endocardium .
They conduct cardiac action potentials more quickly and efficiently than any of the other cells in the heart's electrical conduction system. [4] Purkinje fibers allow the heart's conduction system to create synchronized contractions of its ventricles, and are essential for maintaining healthy and consistent heart rhythm. [5]
This begins with the formation of two endocardial tubes which merge to form the tubular heart, also called the primitive heart tube. The heart is the first functional organ in vertebrate embryos . The tubular heart quickly differentiates into the truncus arteriosus , bulbus cordis , primitive ventricle , primitive atrium , and the sinus venosus .
Also in 2016, Quizlet launched "Quizlet Live", a real-time online matching game where teams compete to answer all 12 questions correctly without an incorrect answer along the way. [15] In 2017, Quizlet created a premium offering called "Quizlet Go" (later renamed "Quizlet Plus"), with additional features available for paid subscribers.
Multiple choice items consist of a stem and several alternative answers. The stem is the opening—a problem to be solved, a question asked, or an incomplete statement to be completed. The options are the possible answers that the examinee can choose from, with the correct answer called the key and the incorrect answers called distractors. [4]
On the organ and tissue scale in mammals and other animals, examples include the circulatory system, the respiratory system, and the nervous system. On the micro to the nanoscopic scale, examples of biological systems are cells , organelles , macromolecular complexes and regulatory pathways.