histology and embryology of organs of oral cavity of human`s презентация

histology and embryology of organs of oral cavity of human`s Performed: piluyshkina Anastasia, 101 stomat

In humans, teeth are represented by two generations: In humans, teeth are represented by two generations: 1. milk (temporary or falling out) - 20 (10 on the upper and lower jaws), 2. permanent - 32. Each tooth is anatomically divided into 3 parts: 1. crown (enamel on the outside), 2. neck: anatomical neck-the junction of enamel with cement, the clinical neck is the place where the gum epithelium attaches to the tooth. 3. root (outside covered with cement). The tooth contains hard tissue (enamel, dentin, cement) and soft tissue (pulp), filled with connecting the pulp chamber of the crown and root canals. The periodontium (the ligaments of a tooth or pariament) connects the root of the tooth to the bone alveolus

Crown Dentin is covered by enamel, and in each root in the crown, dentin is covered by cementum. The inner portion of the dentin of both the crown and the root also covers the pulp cavity of the tooth close to the CEJ. The SEA is the external line at the neck or cervix of the tooth where the enamel of the crown and the cementum of the root usually meet. Portions of the crown are usually defined in more specific ways. The anatomical crown is the portion of the tooth that is covered with enamel. The size of the anatomical crown remains the same throughout the life of the tooth, regardless of the position of the gingiva. The clinical crown is the portion of the tooth that is seen in the mouth. The clinical crown varies in length during the life cycle of the tooth depending on the level of the gingiva. The clinical crown is shorter as the tooth erupts into position, and it becomes longer as surrounding tissues recede.

Root The root of the tooth is that portion that is normally embedded in the alveolar process and is covered with cementum. The root may have one, two, or three branches depending on the type of tooth. Bifurcation stands for division into two roots. Trifurcation means division into three roots. The tapered end of each root tip is called the apex. Any structure or object that is situated at the apex is said to be apical. Anything that surrounds the apex is periapical (peri - means around, and apical refers to the apex).

Enamel Enamel, which makes up the anatomic crown of the tooth, is the hardest material in the body. This hardness is important because enamel forms the protective covering for the softer underlying dentin. It also provides a strong surface for crushing, grinding, and chewing food. Although enamel is strong, it is also very brittle, and this brittleness may cause the enamel to fracture or chip. Along with the strength of enamel, however, the cushioning effect of the dentin and the spring like action of the periodontium enable enamel to withstand most of the pressures brought against it. Enamel is translucent (allows some light to pass through it) and ranges in color from yellow to grayish white. These variations in shade are caused by differences in the thickness and translucency of the enamel and in the color of the dentin beneath it. Enamel, which is formed by ameloblasts, consists of 96 to 99 percent inorganic matter and only 1 to 4 percent organic matrix. Hydroxyapatite, which consists primarily of calcium, is the most prevalent mineral component. Hydroxyapatite is the material that is lost in the process of dental decay. Enamel is similar to bone in its hardness and mineral content. Different from bone, however, mature enamel does not contain cells that are capable of remodeling and repair. Nonetheless, some remineralization is possible.

Dentin Dentin consists of calcified intercellular substance, which is permeated by the so-called "dentine tubules" (dentine tubes), which provide trophic and mineralization of dentin. Dentinal tubules are radially in the crown part of the tooth in the direction from the wall of the pulp chamber to the enamel-dentinal border, and the root portion of the tooth from the wall of the root canal to the root surface of the tooth. However, if in the root part of the tooth, as well as in the area of the occlusal surface of the crown of the tooth, the dentine tubules have an almost straight shape, then in the lateral parts of the crown they will already be S – shaped curved.

Cementum Cementum is rigid connective tissue that covers the root of the tooth. It overlies the dentin and joins the enamel at the CEJ. A primary function of cementum is to anchor the tooth to the bony socket with attachment fibers within the periodontium. Cementum is light yellow and is easily distinguishable from enamel by its lack of luster and its darker hue. It is somewhat lighter in color than dentin. Cementum, which is formed by cementoblasts, is not quite as hard as dentin or bone. In contrast to bone, cementum does not resorb and form again. This difference is important because it makes orthodontictreatment possible. Nevertheless, cementum is capable of some repair through the deposition of new layers. As the root develops, primary cementum, also known as cellular cementum, is formed outward from the cementodentinal junction for the full length of the root. After the tooth has reached functional occlusion, secondary cementum, also known as cellular cementum, continues to form on the apical halfofthe root. As a result, the cervical half of the root is covered by a thin layer of primary cementum, and the apical half of the root has a covering of thickened cementum. This continued growth in the apical area helps to maintain the total length of the tooth by compensation for enamel lost by attrition

Tooth tissues develop from 2 embryonic sources: Tooth tissues develop from 2 embryonic sources: 1. multilayer epithelium of the oral cavity, from which enamel develops, 2. mesenchyma (ectomesenchyma-cells migrating from the neural crest), which gives the Talal tissues of the tooth (dentin, cement and pulp), as well as the ligamentous apparatus of the tooth (para-dont). There are 2 stages in the development of teeth: I-Early, including: - laying of dental rudiments (initiation period). - the formation and differentiation of tooth rudiments (stage of "cap" and "Colo-of there"). II-Late-histogenesis of tooth tissues (stages of apposition and maturation).

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