The general anatomy of the teethComparative anatomy of the teeth.

At the first time the teeth appeared from the squama of the ancient fishes.

There are three types of attachment to the low jaw:

1. The tooth attaches to the external surface of the jaw – acrodontal type.

2. The tooth attaches to the internal surface of the jaw –pleurodontal

3. The tooth grows from own cellular – tekodontal type.

The simplest shapes of the teeth are conical. There is no difference in the shape of

teeth in the lowest vertebrates. Such system is called homodontal. Higher vertebrates

have the heterodontal system of the teeth.

The teeth of the ancient lowest vertebrates were temporary. After their

distraction they were replaced by new teeth. Polyfiodontal type. Higher vertebrates

have only one сhange of teeth- Difiodal type.

The living person has:

1. Type of attachment - tekodontal

2. Type of the shape – heterodontal

3. Type of change –difiodontal.

Development of the teeth.

There are 3 stages of the development of the teeth:

1.Foundations of the teeth

2. Differentiation of the buds of the teeth

3.Formation of the root of the tooth and their eruption.

At the 5-th week of embryonic development lamina enamelare is formed from

ectoderm of the upper and low surfaces of oral cavity. Then epithelium grows and

cavity forms in ectoderm, this cavity is called organon enamelare. At the 10-th

week mesenchyma grows inside of organon enamelare. It is the buds of papillae

dentales. At the end of the 3-d months enamel organ separates from enamel plate.

Only collum of enamel organ communicates these two formations. This organ is

surrounded with dental sac (sacculus dentalis), which fused with papillae

dentales.

At the second stage all cells of enamel organ are divided into different layers. At

the center of enamel organ pulpa is formed, but in periphery ameloblasts in

enamel organ is appeared. Papillae dentales increase at this period and grow in

enamel organ. At the surface of the papillae from the mesenchyma odontoblasts

are formed.

At the 3-d stage, which begins at the end of 4-th embryonic development the

tissues of the teeth appear, they are: dentinum, enamelium and pulp. Ameloblasts

produce enamelium and crown of the tooth forms. Odontoblasts produce

dentinum. Development of the root begins in postembrionic period. From

sacculus dentalis cementoblasts are appered. They produce cementum, which is

covered the root of the tooth. Also they produce fibers, which attach tooth to the

gum. The milk and permanent teeth are developed in one cellulae.

Chewing- communicative system consist of the following parts: 1) the hard

base is the facial skeleton; hard palate and temporomandibular joint; 2) masticator

muscles; 3) tongue, lips and cheeks; 4) teeth; 5) salivary glands.

The part of the jaw with the tooth is called segment. The segment of upper jaw

is called segmenta dentomaxillares. The segment of lower jaw is called

segmenta dentomandibulares. The segments include the following parts: 1) the

tooth; 2)alveoli; 3)ligaments, which attach tooth to the alveoli; 4) vessels and

nerves.

Each tooth consists of:

The cavity of the tooth is filled with the tooth pulp rich in vessels and nerves.

The tooth roots fuse tightly with the surface of the tooth alveoli by means of the

alveolar periosteum (periodontium). The tooth, the periodontium, the alveolar

wall, and the gingiva compose the tooth organ. The hard material of the tooth

consists of Dentine (dentinum); enamel (enamelum) and cement (cementum).

Enamel is the hardest tissue of the human body.

The teeth form the dental rows. Each rows consists of 16 teeth arranched in the

form of dental arch.

Five surfaces are distinguished in each tooth:

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1) Facies vestibularis; 2) f. Lingualis, facing the oral cavity; 3) f.occlusalis looks

to the teeth of opposite side, molar has …; 4) f.contactus is a paired looks at

neibouring tooth. During investigation and describing the tooth some terms are

used: vestibular norm, mastication norm and so on. Crown and root are

divided into three parts: In crown: occlusal third; middle third and cervical

third, but in the root: cervical; middle and apecis third.

Formular of the teeth: the large formular is ;

formular of milk teeth: The other formula

The following three signs are used in determining to which side, right or left, a

tooth belongs: 1) the root sign; 2) the crown angle sign and 3) the crown

curvature sign.

1) The longitudinal root axis is inclined distally and forms an angle with the

line passing through the middle of the crown.

2) The medial angle is sharp and the lateral angle is blunt

3) In occlusal norm the medial part more sharp then the lateral.

Whether a tooth belons to the upper or lower jaw is established from the

shape of the crown and the shape and number of the roots.

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Lecture №1General Anatomy and Development of the Digastive System.

Clinical Anatomy of the Digestive Organs.

Digestion is a physiological process, as a result of which the nutrition in a

digestive tube is exposed to physical and chemical processing, and the nutrient

materials, keeping in it, are soaked up in a blood and lymph.

Functions of a digestive tube:

1. Mechanical and chemical treatment of food.

2. Motor - the mastication, swallowing, agitating both moving on a digestive

tube and evacuation of unnecessary oddments.

3. Absorption of the treated nutrients.

4. Excretion of undigested remnants of the food.

5. Protective - lymphoid device.

The human alimentary canal is about 8-10m long and is subdivided into the

following parts: the cavity of the mouth, the pharynx, the oesophagus, the stomach

and the small and large intestine. The small intestine consists of duodenum, jejunum

and ileum. The large intestine consists of the caecum with vermiform process the

ascending, transverse, descending, and sigmoid colon and finally, the rectum. There

are two large glands in the digestive tube : liver and pancreas.

In the pharynx the alimentary canal crosses with the respiratory tract. Organs

of the digestive system are located in the thoracic and in the abdominal cavity and

the pelvic cavity.

Features of a constitution of walls of the alimentary canal:

Each part of digestive tube has the common features of the wall

1. Mucous membrane (tunica mucosa) is the internal layer of the digestive tube. It

is named so, because the glands which are situated inside this membrane is produced

digestive juices. In structure the mucous membrane consists of: 1)epithelium and

2)lamina propria mucosae. The mucous coat is concerned with absorption and

secretion.

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2.The submucosa layer. It bridges mucous with muscle. It consists of a quaggy

connected tissue and contains plexuses of large veins.

3.Muscle layer (tunica muscularis) situated between the external serous and the

internal mucous membranes. It is formed of smooth muscular tissue. The superior

and inferior parts of the alimentary canal also contain striated fibres. The muscular

coat accomplishes the motor function. In some parts of the digestive canal striate

fibers are developed very well, thus parts are called sphincters. There are two

sphincters in digestive tube: 1) in pyloric part of the stomach; 2) and in iliocecal

valve.

4. Connective tissue covers the alimentary tube from the outside. In the thoracic and

abdominal cavity it is called tunica serosa but in the head and neck it is called tunica

adventitia.

Development of members of an alimentary system

The formation of Digestive organs creates at the 2-d week from Primitive digestive

tube. It is developed from germinal ectoderma. At the 4-th week Primitive digestive

tube is subdivided into three parts: 1) anterior (the foregut), 2) middle part (the

midgut). 3) the posterior part (hindgut)

During this time the tube is closed. The anterior part of the tube is closed with

pharyngeal membrane, but the posterior part of the tube is closed with anal

membrane. Only middle part communicates with yolk sac. At the 7-th week of

embryonic development pharyngeal and anal membranes are destroyed. And

digestive tube open into the external environment from both sides. Later from

foregut develop the posterior part of the mouth, pharynx, oesophagus, stomach,

duodenum, liver and its excretory apparatus, gall bladder, larynx. Derivatives of

midgut: duodenum, jejunum, ileum, coecum and appendix, ascending colon, right

two third of transverse colon. The parts of large intestine are developed from

hindgut.

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Mucous membrane of gastro-intestinal tract is endodermal but the membrane of the

mouth and lower part of anal canal is ectodermal and form stomodeum and

proctodeum respectively.

The musculature and rest of the wall is mesodermal and from splanchnic

mesoderm.

The important function of digestive system is protective function. There is an

accumulation of lymphoid tissue along the whole digestive tube.

At the beginning of the digestive tube some oval-shaped mass of lymphoid

tissue are founded: the lingual tonsil, is located at the root of the tongue, two

palatine tonsil, are located in the depression between two arches of the soft palate,

two tube tonsil, are situated near the auditory tube of the nasopharynx and one

pharyngel tonsil, is located at the posterior wall of the pharynx. Thus, almost a

complete ring of lymphoid structures is called Pirogov,s lymphoepithelial ring.

The next accumulation of lymphoid tissue is vermiform process (appendix

vermiformis). Some scientists call vermiform process is intestinal tonsil. It arises of

the medioposterior surface of the caecum, 2.5-3.5 cm below the iliocaecal junction. It

varies greatly in length and position. Its length may be 3-8 cm. The position of

appendix is first of all associated with the position of the caecum. Usually, it lies in

the right iliac fossa, but may also be located at a higher level or lower level. The

physician must know two points of pain during appendicitis which projected on the

surface of abdomen. McBurney’s point is located at the junction of the lateral and

middle third of a line connecting the umbilical ring with the right anterior superior

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iliac spine. Lanz’s point is located at the junction of the right and middle third of a

line connecting both anterior superior spines.

Small intestine and large intestine have lymphoid nodes. They are aggregated

in small intestine but they are more scattered and rather solitary in large one.

The upper three part (oral cavity, pharynx and part of esophagus) of digestive

tube are located in the head, neck and chest. The other digestive organs lie in

abdominal cavity.

Studding the organs, which are situated in abdominal cavity you must know

the following terms:

Skeletotopy is relation of the organ to the vertebral column and ribs.

Syntopy is relation of the organ to neibouring organs.

Holotopy is projection of the organ to anterior thoracic or abdominal walls.

The abdomen is divided by to horizontal lines, one drawn between the ends of

the X-th ribs and the other between both the anterior superior iliac spines, into three

parts, one located above another: the upper part of the abdomen (epigastrium), the

middle part (mesogastrium) and the lower part (hypogastrium). Each of these three

parts of the abdomen is subdivide by two vertical lines into three secondary regions:

the epigastrium is divided into a middle epigastric region (regio epigastrica) and

two lateral regions, the right and left hypochondrium (regiones hypochondriacae

dextra and sinistra). The middle abdomen is divided into a medial umbilical region

(regio umbilicalis) and two lateral right and left lumbar regions (regiones

abdominalis lateralies dextra and sinistra). Hypogastrium is divided into the pubic

region (regio pubica) and two lateral, right and left inguinal regions (regiones

inguinales dextra et sinistra).

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The abdominal cavity is the space in the trunk below the diaphragm; it is

completely filled with the abdominal organs. The anterior wall of the abdominal

cavity is formed by the three broad abdominal muscles and the straight abdominal

muscles. The components of the lateral walls are the muscular portions of the three

broad muscles of the abdomen. The posterior wall is formed by the lumbar segment

of the spine and the psoas major and quadratus lumborum muscles.

The abdominal cavity is subdivided into the abdominal cavity proper and the

pelvic cavity. Internally of the muscular layers, the abdominal cavity is lined with

the subperitoneal fascia, which is divided into the following parts according to the

regions: the transverse fascia lines the inner surface of the transverse abdominal

muscle and is then continuous with the pelvic fascia on the walls of the pelvis. The

abdominal cavity is lined with a serous membrane called the peritoneum, which also

covers to a lesser or greater extent the abdominal viscera. When the peritoneum

covers the walls of the abdominal cavity it is called parietal peritoneum, if it covers

the visceral organs it is called peritoneum visceralis. The potential space between

the parietal and visceral peritoneum is present. This space is called the peritoneal

cavity (cavum peritonei). It contains а small amount of serous fluid; this fluid

moistens the surface of the organs and so makes easier their movement against one

another. In male this is a close cavity, but in female it communicates with the

external environment by means of a very small abdominal opening of the uterine

tubes, the uterus, and the vagina. Between the parietal peritoneum posteriorly and the

posterior abdominal wall the space is present. This space is called spatium

retroperitoneale. It contains fatty tissue and some organs: kidneys, suprarenal

glands, abdominal aorta, vena cava inferior and pancreas.

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The terms intraperitoneal, mesoperitoneal and extraperitoneal are used to

describe the relationship of various organs to their peritoneal covering. If organ is

covered with the peritoneum from all sides is said to have an intraperitoneal position

(stomack, jejunum, ileum, coecum with vermiform process, colon transversus, colon

sygmoideum, upper part of the rectum); a mesoperitoneal position is that when an

organ is covered by the peritoneum on three sides (colon ascendens, colon

descendens, liver). If an organ is covered with the peritoneum only in one side it is

called extraperitoneal (pancreas, duodenum, kidneys).

There are many small salivary glands in the mucous membrane of the mouth.

They are called labial, buccal, palatine and ligual glands, according the places where

they are located. There are three pairs of large salivary glands, the ducts of which

opens into oral cavity.

The parotid gland is the largest of salivary glands. It is located on the lateral

side of the face on the mandibular ramus. It is a serous gland. It consists of two parts

superficial and deep. Facial nerve and external carotid artery pass through the gland.

This gland has an excretory duct. It passes around the anterior margin of the

masseter, penetrates buccinator and opens near the second upper molar tooth in

vestibule of the mouth.

The sublingual gland is mucous gland. It is situated over the mylohyoid muscle on

the floor of the oral cavity. The ducts of some lobules (18-20 in number) open into

the oral cavity along the sublingual fold.

The submandibular (glandula submandibularis) is of a mixed character,

compound alveolar – tubular in structure. The fascia invests the gland and forms a

thin-walled capsule. The submandibular duct opens on the caruncula sublingualis in

the oral diaphragm.

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