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Human teeth function to mechanically break down items of food by cutting and crushing them in preparation for swallowing and digesting. As such, they are considered part of the human digestive system. [1] Humans have four types of teeth: incisors, canines, premolars, and molars, which each have a specific function. The incisors cut the food ...
Craniata also includes all lampreys and armoured jawless fishes, armoured jawed fish, sharks, skates, and rays, and teleostomians: spiny sharks, bony fish, lissamphibians, temnospondyls and protoreptiles, sauropsids and mammals. The craniate head consists of a three-part brain, neural crest which gives rise to many cell lineages, and a cranium ...
The anatomy of fish is often shaped by the physical characteristics of water, the medium in which fish live. Water is much denser than fish, holds a relatively small amount of dissolved oxygen, and absorbs more light than air does. The body of a fish is divided into a head, trunk and tail, although the divisions between the three are not always ...
A) Overall view of common mudpuppy mouth. B) Ventral view of vomerine and premaxillary teeth, located on the upper part of the mudpuppy mouth. C) Lower jaw, or dentary from a common mudpuppy showing the homodont dentary teeth. Specimen from the Pacific Lutheran University Natural History collection. Mudpuppies use rows of teeth to eat their ...
Diagram of tooth anatomy. Dental anatomy is a field of anatomy dedicated to the study of human tooth structures. The development, appearance, and classification of teeth fall within its purview. (The function of teeth as they contact one another falls elsewhere, under dental occlusion.)
Some fish like carp and zebrafish have pharyngeal teeth only. [30] [31] Sea horses, pipefish, and adult sturgeon have no teeth of any type. In fish, Hox gene expression regulates mechanisms for tooth initiation. [32] [33] While both sharks and bony fish continuously produce new teeth throughout their lives, they do so via different mechanism.
The teeth are in several series; the upper jaw is not fused to the cranium, and the lower jaw is articulated with the upper. The eyes have a tapetum lucidum. The inner margin of each pelvic fin in the male fish is grooved to constitute a clasper for the transmission of sperm. These fish are widely distributed in tropical and temperate waters. [15]
A bathtub faucet with built-up calcification from hard water in Southern Arizona. Hard water is water that has a high mineral content (in contrast with "soft water"). Hard water is formed when water percolates through deposits of limestone, chalk or gypsum, [1] which are largely made up of calcium and magnesium carbonates, bicarbonates and sulfates.