Kidney stones are composed of crystals that usually form in the kidneys or ureters (the tubes that carry urine from the kidneys to the bladder); most are very small but some can be as big as a golf ball. Most small stones cause intense flank and pelvic pain as they irritate the ureters as they pass through them.idney stones are composed of crystals that usually form in the kidneys or ureters (the tubes that carry urine from the kidneys to the bladder); most are very small but some can be as big as a golf ball. Most small stones cause intense flank and pelvic pain as they irritate the ureters as they pass through them.
Osteichthyes /ËÉstiËËÉªkÎ¸i.iËz/ , also called bony fish, are a taxonomic group of fish that have bone, as opposed to cartilaginous, skeletons.The vast majority of fish are osteichthyes, which is an extremely diverse and abundant group consisting of 45 orders, and over 435 families and 28,000 species.It is the largest class of vertebrates in existence today.Osteichthyes are divided into the ray-finned fish (Actinopterygii) and lobe-finned fish (Sarcopterygii).The oldest known fossils of bony fish are about 420 million years ago, which are also transitional fossils, showing a tooth pattern that is in between the tooth rows of sharks and bony fishes.t is the largest class of vertebrates in existence today. Osteichthyes are divided into the ray-finned fish (Actinopterygii) and lobe-finned fish (Sarcopterygii).
The Chondrichthyes are the cartilaginous fishes including the sharks, rays, skates and chimaeras. The Osteichthyes are the bony fish. Both of these groups became established d â¦ uring the Devonian Period about 400 million years ago.The Chondrichthyes differ from the Osteichthyes in many respects, including their skeletons, scales, teeth, buoyancy, swimming, gills and reproduction. Scales:   Cartilaginous fish have large scales called placoid scales. These have a bone like base embedded in the skin and a backward projecting enamel covered dentine spine. The whole thing has a central pulp cavity (rather like the structure of teeth). The epidermis and dermis form placoid scales.