BIOL 224 Lecture Notes - Lecture 13: Proximal Tubule, Nephridium, Hemolymph
Document Summary
Excretory tubules are open at only 1 end. Body uids do not enter directly, an ultra ltrate enters the tubule through narrow extracellular spaces (only small molecules) Flame cells = ciliated cells at the blind end of the tubules (beating of the cilia resembles the ickering of a ame) some molecules/ions are reabsorbed & others are secreted into the tubules. Tubular secretion is released through pores that connect protonephridia to body surface. Principle nitrogenous excretory product is ammonia, some passes out in the urine but most passes through the body wall: metanephridia (annelids/molluscs): Fluid is an ultra- ltrate of uids in the closed circulatory system, enters proximal end of excretory tubule. Ions/other solutes are reabsorbed/secreted as the uid moves along tubule. Urine from the distal end of the tubule collects in a saclike storage organ (the bladder) then released through a pore in the surface of the segment: malpighian. Excretory tubules have a closed proximal end immersed in the hemolymph.
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