Odontoblast Totally Explained

Everything about Odontoblast totally explained

An odontoblast is a biological cell of neural crest origin that's part of the outer surface of the dental pulp, and whose biological function is dentinogenesis, which is the creation of primary dentin, the substance under the tooth enamel. Odontoblasts first appear at sites of tooth development at 17-18 weeks in utero and remain present until death unless killed by bacterial or chemical attack or pulpal necrosis. The odontoblasts secrete dentin throughout life (secondary dentin, once root formation is complete), which may be an attempt to compensate for natural wearing down of the enamel. Odontoblasts also secrete tertiary dentin when irritated. In the case of an infection breaching the tooth to the pulp and killing odontoblasts, Periodontal Ligament Stem Cells can differentiate into odontoblast-like cells which would then secrete reparative dentin underneath the site of attack. This isn't only to slow the progress of the attack, but also to prevent the diffusion of bacterial products into the pulp, reducing the probability of pulp necrosis. Odontoblasts are large columnar cells arranged in an epithelioid sheet along the junction between dentine and pulp, all the way down to the root apex. It is rich in endoplasmic reticulum and golgi apparatus, especially during primary dentine formation, to give it a high secretory capacity (firstly collagenous matrix to form predentine, then mineral to form the complete dentine). Its nucleus is aligned away from the dentine, with its golgi and ER above it (towards the dentine) reflecting its unidirectional secretion. On initial dentine formation it moves pulpally, away from the primitive amelodentinal junction (then Inner Enamel Epithelium/dental papillary junction) leaving behind a tubular structure known as the odontoblast process. This keeps its tapered structure with cytoskeletal fibres, mainly actin. A pulpal A-delta (noxious, short sharp pain) nerve fibre is wrapped around the base of this process. This process lies in a tubule, known simply as a dentinal tubule. In a complete tooth, this process rarely extends beyond 1/3 the depth of the dentine. The functions of the odontoblast process are as follows:
1. To aid in the secretion of tubular dentin (dentin surrounding tubule) which further organises and strengthens the dentine as a whole tissue 2. General maintainance of the dentinal tubule and dentinal fluid (ion/protein content etc.) 3. To secrete sclerotic dentin upon carious attack to block off dentinal tubules, slowing the progress of the attack (air space above blockage is known as a dead space) 4. To channel signals of attack to the odontoblast cell body, initiating reactionary dentin secretion 5. To channel hydrokinetic forces of water movement to the A delta fibre wrapped around its base, maintaining dentine sensitivity The biological tissue formed by odontoblasts is a type of hard tissue.

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