Three vertebrates kidney structures
1. Fish: Fish have a pair of small, elongated kidneys located in the posterior abdomen. These kidneys consist of numerous small units called nephrons, which filter and remove waste products from the blood. Fish kidneys also play a role in regulating the osmotic balance of the body.
2. Birds: Birds have relatively large kidneys located in the abdominal cavity. Similar to fish, bird kidneys contain nephrons that filter waste products from the blood. However, bird kidneys have an additional structure called the uric acid gland, which is responsible for converting toxic ammonia into less harmful uric acid. This adaptation helps birds conserve water as uric acid requires less water for excretion compared to ammonia.
3. Mammals: Mammals, including humans, have a pair of bean-shaped kidneys located behind the abdominal cavity, against the back muscles. Mammalian kidneys consist of numerous nephrons that filter blood and produce urine. Besides excreting waste products, mammalian kidneys also regulate the pH balance, electrolyte levels, and water balance of the body.