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The small intestine, its parts, structure of the wall. Duodenum: topography, structure, blood and nerve supply, lymphatic drainage

The small intestine begins at the pylorus, makes series of looped curves. Three parts are: 1) duodenum; 2) the jejunum; 3) the ileum. The duodenum runs around the head of pancreas. Four main parts are: 1) pars superior; 2) pars descendens; 3) pars horizontalis; 4) pars ascendens.

Structure: Duodenal wall consists of four layers: the mucosa, submucosa, muscular and serous. Mucosa is divided into three layers: epithelial, lamina propria and muscle plate. Lamina propria has - intestinal villi and duodenal glands. Muscular coat is composed of inner circular and outer - longitudinal smooth muscle layers. In mucous membrane longitudinal fold present, this fold terminates in papilla. Present 2 types of papilla: the greater duodenal papilla smaller duodenal papilla. Near this papilla located – hepatopancreatic ampulla.

Blood supply: aa. pancreaticoduodenalis and aa. pancreaticoduodenalis inferiores. The venous blood flows along veins of the same name into portal vein.

Lymphatic drainage: a nterior lymphatic vessels drain into pancreatoduodenal lymph nodes and pyloric lymph nodes. The posterior lymphatic vessels pass posterior to the head of the pancreas and drain into superior mesenteric lymph nodes. Efferent lymphatic vessels from duodenal lymph nodes pass into celiac lymph nodes. Nerve supply: plexus subserosus, plexus myentericus and plexus submucous.

The large intestine: topography, structure, departments and their relation with the peritoneum. Blood and nerve supply, lymphatic drainage of the large intestine. Variety of position of appendix.

The large intestine – extends from end of small intestine to anus; is divided into: 1) caecum; 2) ascending colon; 3) transverse colon; 4) descending colon; 5) sigmoid colon; 6) rectum. Large intestine is distinguished from small intestine by: 1) teniae coli; 2) haustra coli; 3) appendices epiploicae.

Teniae coli – begin at the vermiform process and extend to beginning of rectum, is divided into 3 bands: 1) tenia libera; 2) tenia mesocolica; 3) tenia omentalis.

Caecum – lies in right iliac fossa. The vermiform process – arises from medioposterior surface. Caecum and vermiform process completely enclosed by peritoneum. There are 4 variants of appendix position: 1) Descending position – the end of long process descends to true pelvis; 2) Lateral position; 3) Medial position; 4) Ascending position – behind caecum.

Colon ascendens: is continuation of caecum, boundary between them where small intestine empties into colon. From this junction it passes upward, then bend to left and continuous to colon transversus. Colon transversum: extends from right flexure to left flexure of colon. Colon transversum – in front is covered by greater omentum; above – liver, gall bladder, stomach, tail of pancreas. Colon descendens: passes downward in the left side and then it continuous with sigmoid colon. In front, covered by small intestine. Colon sigmoideum: continuation of descending colon. Rectum: se rves for accumulation, evacuation of faeces. Relation with the peritoneum: ascending and descending colon: are covered by peritoneum, except posterior surface. Transverse colon – completely covered by peritoneum. Sigmoid colon – is covered by peritoneum in all sides.

Blood supply: branches of superior and inferior mesenteric arteries. Nerve supply: superior and inferior mesenteric, superior, middle and inferior rectal plexuses, vagus nerve, pelvic splanchnic nerves. Lymphatic drainage: nodi lymphatici ileocolici, nodi lymphatici colici dextri, medii, sinistri, nodi lymphatici mesenterici inferiores.

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