Excretory System Biology for Majors
Osmoregulation Osmoregulation is the process of maintenance of salt and water balance (osmotic balance) across membranes within the body’s fluids, which are composed of water, plus electrolytes and non-electrolytes
Why is Osmoregulation Important? The blood maintains an isotonic environment so that cells neither shrink nor swell
Excretory System Kidneys filter the blood, producing urine that is stored in the bladder prior to elimination through the urethra
Excretion by Exocytosis Some unicellular organisms, such as the amoeba, ingest food by endocytosis. The food vesicle fuses with a lysosome, which digests the food. Waste is excreted by exocytosis.
Practice Question What is the role of the skin and lungs in excretion?
Quick Review • Why are osmoregulation and osmotic balance important body functions? • What is the structure of the kidneys and how does each part of kidney function? • How do different excretion systems function? • How do hormonal cues help the kidneys synchronize the osmotic needs of the body?