BISC 320 Lecture Notes - Lecture 24: Distal Convoluted Tubule, Proximal Tubule, Renal Pelvis
19 Oct 2017
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Ch 29: kidneys: excretory systems, basic excretory sytems, respiratory system. Co2: the breakdown of proteins and nucleic acids yields an additional waste product, ammonia, which is a highly toxic compound. This pathway costs the most to produce, but requires the least water for excretion. Renal organs: protonephridia, found in flatworms, larval annelids, and mollusks, blind end ducts project into body cavity, ultrafiltration driven by cilia moving the fluid into the ducts. The ends of the ducts are special cells with openings, or fenestration, in them. Ions and uric acid are secreted into the tubules. Water from the extracellular fluid follows the ions by osmosis. The water and ions flow into the gut before exiting the body, and the solutes and water are reabsorbed back into the body: insects excrete uric acid along with digestive waste. Remember that insects use a tracheal system for respiration, making them vulnerable to evaporative water loss.
