BIO E105 Lecture Notes - Lecture 21: Malpighian Tubule System, Osmotic Shock, Hemolymph
Document Summary
To maintain homeostasis, insects must carefully regulate the composition of a bloodlike fluid called hemolymph. Through the excretory system, insects can avoid osmotic stress. To maintain water and electrolyte balance, insects have malpighian tubules, an excretory organ, and the hindgut the posterior portion of their digestive tract. Malpighian tubules have a large surface area are in direct contact with the hemolymph empty into the hindgut. Research suggests that epithelial cells in the malpighian tubules are relatively impermeable to sodium ions but contain a pump that actively transports potassium ions into the tubules. The malpighian tubules form a filtrate from the hemolymph. The filtrate is then passed on to the hindgut as a pre-urine . Cells of the malpighian tubules contain a potassium pump. This results in a high concentration of k+ in the cells water then follows by osmosis. Other electrolytes and nitrogenous wastes diffuse into the filtrate.
