EXCRETORY STRUCTURES IN NON-CHORDATES
In protozoans, porifers and coelenterates the specialised excretory structures are absent. The excretion in these animals occurs through the general body surface. The contractile vacuoles present in freshwater protozoans are the osmoregulatory structures and regulate osmotic concentration (osmolarity) of the body. Though some ammonia is also lost through contractile vacuoles, but they can not be considered as excretory structures. In Platyhelminthes (flatworms) the excretory structures are Protonephridia or Solenocytes. These structures are also present in Rotifers, Cephalochordates (Amphioxus). and some annelids. The tubules of protonephridia in flatworms terminate into Flame cells. These cells contain a tuft of cilia which project into the tubule and beat like flickering (candle) flame, hence…
EXCRETORY SYSTEM IN HUMAN
Except for urinary bladder which is endodermal in origin, the whole excretory system is Except urinary bladder which is endodermal in origin, the whole excretory system is Except mesodermal. In human the kidney is retroperitoneal i.e., the kidney is located outside the coelomic cavity and is covered by peritoneum (coelomic epithelium) from the ventral side only. The size of each kidney is ~10 cm and it weighs is ~150 g. The two kidneys are asymmetrical, the Rt. being posterior to the Lt. Each kidney is bean-shaped with a groove (hilus) in the middle. The hilus is absent in frog’s kidney. The white fibrous connective tissue-covering around kidney is called renal…
