Urgench state university Faculty of natural science Department of biology Student of group 198 Khosinova Gulasal

Urgench state university Faculty of natural science Department of biology Student of group 198 Khosinova Gulasal.

The Theme:

• The structure of the teeth, esophagus.

The Plan:

• The structure of the teeth.
• The structure of the esophagus.
• Passage of Food through the Esophagus.
• Interdependence of teeth and esophagus.

Course Objectives:

• To gain knowledge about the internal organs. Students study the structure of the teeth and esophagus with the help of educational equipment.

Equipments:

• anatomical atlas, literature, models, posters, album.

Theoretical part:

• The teeth are secured in the alveolar processes (sockets) of the maxilla and the mandible. Gingivae (commonly called the gums) are soft tissues that line the alveolar processes and surround the necks of the teeth. Teeth are also held in their sockets by a connective tissue called the periodontal ligament.

The two main parts of a tooth are the crown, which is the portion projecting above the gum line, and the root, which is embedded within the maxilla and mandible. Both parts contain an inner pulp cavity, containing loose connective tissue through which run nerves and blood vessels. The region of the pulp cavity that runs through the root of the tooth is called the root canal. Surrounding the pulp cavity is dentin, a bone-like tissue. In the root of each tooth, the dentin is covered by an even harder bone-like layer called cementum. In the crown of each tooth, the dentin is covered by an outer layer of enamel, the hardest substance in the body.

Although enamel protects the underlying dentin and pulp cavity, it is still nonetheless susceptible to mechanical and chemical erosion, or what is known as tooth decay. The most common form, dental caries (cavities) develops when colonies of bacteria feeding on sugars in the mouth release acids that cause soft tissue inflammation and degradation of the calcium crystals of the enamel.

The order (formula) of permanent teeth is as follows:

3.2.1.2- 2.1.2.3

3.2.1.2- 2.1.2.3

The neck of the tooth (collum dentis) is the narrowed part between the crown and the root. It is surrounded by the mucous membrane of the gums. The root of the tooth (radix dentis) is one to three and is located in the tooth cells. It ends at the apex radicis. The cavity inside the crown (cavitas dentis) continues as a canal to the root (canalis radicis dentis). This canal opens into the root tip hole (foramina apicis dentis) at the root tip. The blood vessels and nerves that enter through it form the tooth pulp (pulpa dentis). Depending on the location of the tooth pulp, it is divided into intracranial (pulp coronalis) and intra-root (pulp radicialis). The substance of the tooth consists of dentin (dentinum), the crown of the tooth is covered with enamel on the outside, and the root is covered with cement (cementum). In humans, the tooth comes out twice. Deciduous teeth (dentes decidui) begin to appear when a child is 5-7 months old, and by the age of 2-2.5 years their number reaches 20.

The esophagus is a slightly flattened tube from the front to the back that passes food from the esophagus to the stomach. Its length is 25-30 cm. The esophagus begins at the VI-VII cervical vertebrae and passes to the left side of the X-XI thoracic vertebrae at the entrance to the medulla. It is divided into three parts: the neck, chest and abdomen. The cervical part of the esophagus (partes cervicalis) corresponds to the area of the VII cervical spine. It is anterior to the larynx, posterior to the spinal cord, and lateral to the posterior sciatic nerve and common carotid artery. The thoracic part of the esophagus (partes thoracica) is the longest part, located in the posterior thoracic cavity in front of the spine. It moves slightly to the left and forward in the area of the IX thoracic spine, away from the spine.

There are also two physiological contractions in the esophagus:

1. Aortic narrowing at the intersection of the esophagus with the aorta.

2. Cardiac contraction at the junction of the esophagus with the stomach.

The esophageal wall consists of the following layers. The tunica mucosa is relatively thick and has a well-known muscular layer. It is covered on the inside with a multilayered squamous epithelium. The mucous membrane contains longitudinal folds, esophageal mucosal glands (glandulae esophageae) that open into the organ cavity, and individual lymphoid nodes. Because the submucosa is well developed, it forms longitudinal folds in the mucous membrane, and in the cross section of the esophagus, its cavity appears as a star. Longitudinal folds flatten as the bite passes, widening the esophageal cavity.