General(common) anatomy of a skeleton of the person



Lecture №1

General Anatomy and Development of the Digastive System.

Clinical Anatomy of the Digestive Organs.

Digestion - 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 is provided by presence of a specific musculation.

3. Absorstion of the treated nutrients.

1. 4 Excretion of undigested remnants of the food.

1. 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 stomack and the small and large intestine. The small intestine consists of duodenum, jejunum and illeum. The large intestine consists of the caecum with vermiform process the ascending, transverse, descending, and sigmoid colon and finally, the rectum. The upper three part located in the head, neck and chest maintain a relatively straight direction. In the pharynx the alimentary canal intersects with the respiratory tract. Organs of the digestive system are located in the thorasic and in the abdominal cavity and the pelvic cavity.

Features of a constitution of walls of the alimentiry canal:

1. Mucous membrane (tunica mucosa) is the internal layer of the digestive tube. The mucosa is named so, because in it is produced and is mucified of complex

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composition - digestive juices. In structure the mucous membrane consists of: 1)epithelium and 2)lamina propria mucosae. The mucos coat is concerned with absorption and secretion

2. The submucosa bridges mucous with muscle. It consists of a quaggy connected tissue and contains plexuses of large veins. Their elastic fibers attach an elastance to an environment as a whole.

3. Muscle layer{tunica muscularis} situated between the external serous and the internal mucous membranes 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.

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 adventitia.

Development of members of an alimentary system

The digestive tube is developed from Primitive digestive tube, which is the interna embryonic part of archenteron or primary yolk sac after the formation of foldings of the embryo. Primitive digestive tube is divided into three parts: 1) anterior (the foregut), from which develop the posterior part of the mouth, pharynx, oesophagus, stomack, duodenum, liver and its excretory apparatus, gall bladder, larynx;

2) middle part (the midgut) communicating with the yolc sac. Derivatives of midgut: duodenum, jejunum, ilium, coecum and appendix, ascending colon,right two third of transversae colon.

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3) the posterior part (hindgut) from which the parts of large intestine develops.

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 respectivelt.

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

PARTS OF THE DIGESTIVE TUBE

1. Cavity of the mouth (cavitas oris) is divided into two parts: vestibulum oris and cavitas oris propria. The vestibulum of the mouth is the space bounded by the lips ans cheeks externally and by the teeth and gingivae internally. Cavitas oris proprium extends from the teeth anterioly and laterally to the entry into the pharynx posterioly through the fauces. The oral cavity is bounded superioly by the hard palate and the anterior part of the soft palate; the floor is formed by the diapfragm of the mouth and is occupied by the tongue.

2. The pharynx is that part of the alimentary canal and respiratory tract, which is a connecting link between the cavity of the nose and mouth and the oesophagus and trachea. The pharynx is divided into three parts: nasal part of the pharynx (pars nasalis),oral part (pars oralis),laryngeal part (pars laryngea).

At the entry into the pharynx some oval-shaped mass of lymphoid tissue are founded: the lingual tonsil, located at the root of the tongue, two palatine tonsil, located in the depression between two arches of the soft palate, two tube tonsil, situated near the auditory tube of the nasopharynx and one pharyngel tonsil, located at the posterior wall of the pharynx. Thus,

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

3. The oesophagus is a narrow and long actively functioning tube inserted between the pharynx and the stomach.

THE ABDOMINAL CAVITY

4. Begining with the stomach, the parts of the digestive tract with its large glands are located in the abdominal cavity.

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 tendinous expansions of 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. The pelvic cavity is bounded posterioly by the piriform muscles, anterioly and laterally by parts of the hip bones with the overlying internal obturator muscles which are lined with fasciae. The floor of the pelvic cavity is formed by the pelvic diaphragm. 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

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covers the walls of the abdominal cavity it is called parietal peritoneum, if it covers the visceral organs it is called peritoneum visceralis. Both layers are in close contact and in an intact abdominal cavity there is only а narrow space between them called the peritoneal cavity (cavum peritonei) that contains а small amount of serous fluid; this fluid moistens the surface of the organs and so makes easier their movement against one another. An organ invested in the peritoneum is said to have an intraperitoneal position (stomack, jejunum, ileum, coecum, colon transversus, colon sygmoideum); 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 by the peritoneum only in front its position is called extraperitoneal (pancreas, duodenum, kidneys).

Between the peritoneum and the abdominal walls is а connective- tissue layer containing а greater or lesser amount of fatty tissue. This space is called spatium retroperitoneale.

5. The small intestine (intestinum tenue) begins at the pylorus, and ends at the beginning of the large intestine. Mechanical and further chemical treatment of food under conditions of an alkaline reaction occurs in the small intestine as well as absorption of the nutriens.

Three parts are distinguished in the small intestine: 1) the duodenum, the part nearest to the stomach; 2) the jejunum wich accounts for two fifth of the small intestine with the exception of the duodenum; 3) the ileum, composing the remaning three fifth. There is no clearly manifest anatomical boundary between the jejunum and ileum and their separation is therefore relative.

6. The large intestine (intestine crassum) exteneds from the end of the small intestine to the anus and is divided into the following parts: 1) caecum with

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the vermiformis process; 2) ascending colon (colon ascendens) 3) transverse colon (colon transversum); 4) descending colon (colon descendens); 5) sigmoid (pelvic) colon (colon sigmoideum) and 6) rectum.

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

The liver is primarily a large digestive gland secreting bile, which flows along the efferent duct into the duodenum. It is weighing about 1500 g. The pancreas is situated behind the stomach. Two components are distinguished in it: the main bulk of the gland is concerned with external secretion and excretes its secretions into the duodenum by way of the ducts; the smaller part of the gland consists of the islets of Langerhans is an endocrine structure secreting insulin into the blood. Insulin regulates the blood sugar content. There are indications that the pancreas contributes to haemopoiesis and regulation of blood pressure.

The Digestive System 471

pancreaticus) receives numerous branches draining into'it almost at а right angle. It joins the ductus choledochus and both open by means of а common orifice on the greater duodenal papilla. This constructive connection of the pancreatic duct with the ductus choledochus is determined by its functional significance (treatment of the duodenal contents with the pancreatic juice) as well as by the development of the pancreas from the part of the primary gut from which the duodenum also arises. In addition Со the main duct, there is usually an accessory pancreatic duct (ductus pancreaticus accessorius), which opens on the smaller duodenal papilla (about 2 cm above the greater duodenal papilla). An accessory pancreas (pancreasaccessorium) is sometimes encountered, mostly in the jejunal wall, less frequently in the wall of the stomach or ileum under the mucous or serous coat; its size varies from several millimetres to 4-5 сш (such is the normal position of the pancreas in some lower vertebrates). An annular pancreas is sometimes found, it causes compression of the duodenum.

Structure. According Со structure, the pancreas is related to the group of acinar ог acinar-tubular glands.

Two components are distinguished in it: the main bulk of the gland is concerned with external secretion and excretes its secretions into the duodenum Ьу way of the ducts; the smaller part of the gland consists of the islets of Langerhans (insulae pancreaticae) and is an endocrine structure secret- ing insulin ( insula island) into the blood; insulin regulates the blood sugar content. There are indications that the pancreas contributes Со haemopoiesis and regulation of blood pressure.

As а gland of mixed secretion, the pancreas receives numerous sources of nutrition, namely the superior and inferior pancreaticoduodenal arteries, the splenic and left gastro- epiploic arteries, etc. The veins of the нате name drain into the portal vein and small veins draining into it. The lymph flows to the nearest nodes: coeliac, pancreaticolienal, and others.

Innervation is accomplished from the solar plexus.

ТНЕ PERITONEUM

The peritoneum is а closed serous sac, which communicates with the external environment only in females by means of а чету small abdominal opening of the uterine tubes. Like any serous sac, it consists of two layers, parietal (peritoneum parietale) and visceral (peritoneum visceral

e). The parie- tal layer lines the abdominal wall, while the visceral layer invests the viscera and forms their serous covering for а shorter or longer distance. Both layers are in close contact and in an intact abdominal cavity there is only а nar- row space between them called the peritoneal cavity (cavum peritonei) that contains а small amount of serous fluid; this fluid moistens the surface of the organs and so makes easier their movement against one another. When air enters the cavity during operation or postmortem examination or when pathological fluids accumulate in it, it acquires the lappearance of а true, more or less large cavity.

The parietal peritoneum forms а continuous lining on the anterior and lateral walls of the abdomen and passes on to the diaphragm and the

posterior abdominal wall. Неге it is reflected on the viscera and is directly continuous with the visceral peritoneum investing them (Fig. 223).

Between the peritoneum and the abdominal walls is а connective- tissue layer containing а greater or lesser amount of fatty tissue. This is the extraperitoneal tissue (tela subserosa), which is developed irregularly. It is absent, for instance, in the region of the diaphragm but is developed best on the posterior abdominal wall where it surrounds the kidneys, ureters, adrenal glands, the abdominal aorta and vena cava inferior and their branches. On а greater area of the anterior abdominal wall the extraperitoneal tissue is poorly developed, but in the pubic region the amount of fat increases in it and the peritoneum is joined here loosely with the abdominal wall. As а result, а distended urinary bladder pushes the peritoneum away from ................
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