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[2] [3] Gap junctions connect the cytoplasms of neighboring cells electrically allowing cardiac action potentials to spread between cardiac cells by permitting the passage of ions between cells, producing depolarization of the heart muscle. [3] [2] All of these junctions work together as a single unit called the area composita. [2]
At around 18 to 19 days after fertilisation, the heart begins to form. The heart begins to develop near the head of the embryo in the cardiogenic area. [1] Following cell signalling, two strands or cords begin to form in the cardiogenic region [1] As these form, a lumen develops within them, at which point, they are referred to as endocardial ...
The average cardiac output, using an average stroke volume of about 70mL, is 5.25 L/min, with a normal range of 4.0–8.0 L/min. [8] The stroke volume is normally measured using an echocardiogram and can be influenced by the size of the heart, physical and mental condition of the individual, sex, contractility, duration of contraction, preload ...
A syncytium (/ s ɪ n ˈ s ɪ ʃ i ə m /; pl.: syncytia; from Greek: σύν syn "together" and κύτος kytos "box, i.e. cell") or symplasm is a multinucleate cell that can result from multiple cell fusions of uninuclear cells (i.e., cells with a single nucleus), in contrast to a coenocyte, which can result from multiple nuclear divisions without accompanying cytokinesis. [1]
A heart valve is a biological one-way valve that allows blood to flow in one direction through the chambers of the heart.A mammalian heart usually has four valves. Together, the valves determine the direction of blood flow through the heart.
Coronary artery disease (CAD), also called coronary heart disease (CHD), or ischemic heart disease (IHD), [13] is a type of heart disease involving the reduction of blood flow to the cardiac muscle due to a build-up of atheromatous plaque in the arteries of the heart.
Other terms used include "cycle length variability", "R–R variability" (where R is a point corresponding to the peak of the QRS complex of the ECG wave; and R–R is the interval between successive Rs), and "heart period variability". [1] Measurement of the RR interval is used to derive heart rate variability. [1]
Serratus anterior normally originates by nine or ten muscle slips – arising from either the 1st to 8th ribs, or the 1st to 9th ribs; because two slips usually arise from the 2nd rib, the number of slips is greater than the number of ribs from which they originate.