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The premolars, also called premolar teeth, or bicuspids, are transitional teeth located between the canine and molar teeth. In humans, there are two premolars per quadrant in the permanent set of teeth, making eight premolars total in the mouth. [1] [2] [3] They have at least two cusps.
This tissue contains blood vessels and nerves that enter the tooth from a hole at the apex of the root. [23] Along the border between the dentin and the pulp are odontoblasts, which initiate the formation of dentin. [16] Other cells in the pulp include fibroblasts, preodontoblasts, macrophages and T lymphocytes. [24]
The tooth bud (sometimes called the tooth germ) is an aggregation of cells that eventually forms a tooth and is organized into three parts: the enamel organ, the dental papilla and the dental follicle. [3] The enamel organ is composed of the outer enamel epithelium, inner enamel epithelium, stellate reticulum and stratum intermedium. [3]
Blood vessels transport blood cells, nutrients, and oxygen to most of the tissues of a body. They also take waste and carbon dioxide away from the tissues. [2] Some tissues such as cartilage, epithelium, and the lens and cornea of the eye are not supplied with blood vessels and are termed avascular.
The bell stage is known for the histodifferentiation and morphodifferentiation that takes place. The dental organ is bell-shaped during this stage, and the majority of its cells are called stellate reticulum because of their star-shaped appearance. The bell stage is divided into the early bell stage and the late bell stage. [1]
Gross anatomy (also called topographical anatomy, regional anatomy, or anthropotomy) is the study of anatomical structures that can be seen by the naked eye. [1] Microscopic anatomy is the study of minute anatomical structures assisted with microscopes , which includes histology (the study of the organization of tissues), [ 1 ] and cytology ...
The tonsils also are lymphatic tissue and help mediate the ingestion of pathogens. Tonsils in humans include, from superior to inferior: nasopharyngeal tonsils (also known as adenoids), palatine tonsils, and lingual tonsils. Together this set of lymphatic tissue is called the tonsillar ring or Waldeyer's ring.
The reason is uncertain. They are more common in molar teeth, especially first molars compared to second molars and premolars. [32] A review suggested this was because the first molars are the first teeth to be located in the mandible (lower jaw) and have longer exposure to degenerative changes. They also have a larger blood supply. [32]