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T-tubules (transverse tubules) are extensions of the cell membrane that penetrate into the center of skeletal and cardiac muscle cells.With membranes that contain large concentrations of ion channels, transporters, and pumps, T-tubules permit rapid transmission of the action potential into the cell, and also play an important role in regulating cellular calcium concentration.
Early seed plants like ferns have spores and motile sperm that swim in a water medium, called zooidogamy. [18] The angiosperm pollen tube is simple, unbranched, and fast growing, however this is not the case for ancestral plants. In gymnosperms like Ginkgo biloba and cycadophyta, a haustorial pollen tube forms. The tube simply soaks up ...
T tubule: transverse intracellular tubules invaginating from the cell membrane and surrounding the myofibrils of the T system of skeletal and cardiac muscle, serving as a pathway for the spread of electrical excitation within a muscle cell; Trachea: tubules forming the respiratory system of most insects and many arachnids
A desmotubule is an endomembrane derived structure of the plasmodesmata that connects the endoplasmic reticulum of two adjacent plant cells. [1] [2] The desmotubule is not actually a tubule but a compact, cylindrical segment of the ER that is found within the larger tubule structure of the plasmodesmata pore. [3]
The sodium-hydrogen antiporter's function is upregulated by Angiotensin II in the proximal convoluted tubule when the body needs to reabsorb sodium and excrete hydrogen. [34] Plants are sensitive to high amounts of salt, which can halt certain necessary functions of the eukaryotic organism, including photosynthesis. [31]
Within the t-tubules, distinct ion channels and cellular proteins are present within the t- tubule bilayer that allow movement of calcium influx from the extracellular space into the myocyte to initiate depolarization and contraction. Once traveling through the t- tubules, the calcium arrives at the sarcoplasmic reticulum.
A T-tubule surrounded by two terminal cisternae is called a triad. The terminal cisternae, along with the transverse tubules, are the mechanisms of transduction from a nervous impulse to an actual muscle contraction .
In plant anatomy, there are two main types of sieve elements. Companion cells and sieve cells originate from meristems, which are tissues that actively divide throughout a plant's lifetime. They are similar to the development of xylem, a water conducting tissue in plants whose main function is also transportation in the plant vascular system. [1]