The Small & Large Intestine.pptx

The small intestine is the part of the alimentary canal that is continuous with the stomach at the pyloric orifice and leads into the large intestine through the iliocaecal valve. It is the part where the chemical digestion of food is completed and most of the absorption of nutrients take place.
It extends from the ileum to the anus.
It reabsorbs water converting liquid chyme into semi solid stools.
It consists of the following parts: 1)Caecum and vermiformis appendix. 2)Ascending colon and hepatic flexure. 3) Transverse colon and splenic flexure 4)Descending colon 5)Sigmoid colon 6) Rectum and 7) Anal canal.
The proximal half as far as the splenic flexure – reabsorbs water and electrolytes from fluid chyme .
The distal colon beyond the splenic flexure-stores formed faeces until they are excreted.

1. The SMALL & LARGE INTESTINE Dr. NDAYISABA CORNEILLE CEO of CHG MBChB,DCM,BCSIT,CCNA Supported BY

2. SMALL INTESTINE The small intestine is the part of the alimentary canal that is continuous with the stomach at the pyloric orifice and leads into the large intestine through the iliocaecal valve. It is the part where the chemical digestion of food is completed and most of the absorption of nutrients take place. Dr Ndayisaba Corneille 2

3. LOCATION It is found lying mainly at the central and lower part of the abdomen cavity mostly within the colonic loop where it lies post to the greater omentum and anterior abdominal wall. It also extends into the pelvic region where it lies anterior to the rectum. Dr Ndayisaba Corneille 3

4. Length The length of the small intestine varies between 6-7m but on the average it is about 5m in a living adult. Dr Ndayisaba Corneille 4

5. Histology of the Small Intestine Unlike the stomach the small intestine has four (4) basic coats: Serosa Muscularis External Submucosa Mucosa Dr Ndayisaba Corneille 5

6. SUBDIVISION The small intestine is divided in to three parts: The duodenum The Jejunum The Ileum Dr Ndayisaba Corneille 6

7. THE DUODENUM Historically the duodenum is a Latin word that is derived from a Greek word that signifies 12 because it was believed that the length of the duodenum is about 12 fingers breadth. The duodenum is actually 25cm in length The duodenum is the shortest, most fixed and dilated proximal part of Small intestine. And lies above the umbilicus opposite to 1, 2 & 3rd Lumbar Vertebrae Dr Ndayisaba Corneille 7

8. It is devoid of mesentery and it is fixed to posterior abdominal Wall. It curved around head of pancreas in a C – shaped curvature It receives Bile duct and pancreatic duct. Dr Ndayisaba Corneille 8

9. Duodenum has 3 flexures which include: 1 2 3 Superior duodenal flexure 2. Inferior duodenal flexure Duodeno -jejunal flexure. The presence of these flexures lead to the division of the duodenum into four parts Dr Ndayisaba Corneille 9

10. The subdivided parts does not have any anatomical demarcating landmarks, they are named base on position. The parts include: First / upper part – 5 cm Second / vertical part – 7.5 cm Third / horizontal part – 10 cm Fourth / ascending part – 2.5 cm 1st 2nd 3rd 4th Duodenum - parts Dr Ndayisaba Corneille 10

11. DUODENUM – PERITONEAL RELATIONS Duodenum is mostly retroperitoneal and Fixed except at its two ends where it is suspended by folds of peritoneum. Anteriorly the duodenum is partly Covered with peritoneum. Posteriorly it is devoid of peritoneum Dr Ndayisaba Corneille 11

12. DUODENUM – PECULIARITIES OF FIRST PART (5cm) The first part is the most movable part It is devoid of circular mucous fold which is present in other parts of the small intestine. Seen as duodenal cap / Bulb in Radiographs. d) In the submucosa are present numerous Brunner’s gland which secrets mucus that protect its wall from the acidic content of the chyme discharged from the stomach Supplied by end arteries May be affected by peptic ulcer Dr Ndayisaba Corneille 12

13. Begins at superior duodenal flexure opposite the L1 vertebra passes vertically downwards and ends at inferior duodenal flexure where it continues with the 3 rd part opposite the Lower border of L3 - it lies in front of hilum of Right Kidney - along right Side of vertebral column in paravertebral gutter DUODENUM – SECOND PART (7.5 CM) Rt. Lat. Plane Dr Ndayisaba Corneille 13

14. Here marks the commencement of a unique Circular folds in the small intestine known as the Plica Circularis – Permanent, circular & thick. Major duodenal papilla is present (on posteromedial wall of 2 nd part 10 cm distal to pylorus) It is the opening of the combine ducts of the Bile duct & pancreatic ducts (Ampulla of vater ) Minor duodenal papilla 2 cms above major papilla is also present another smaller papilla for the opening of the Accessory pancreatic duct opens Duodenum – Interior of second part Dr Ndayisaba Corneille 14

15. Extends from inferior Duodenal flexure in front of aorta at L3 level Relations - Anteriorly : it is Covered by peritoneum except at the point of attachment of root of mesentery of the Small intestine Anterior Surface is crossed by Superior Mesenteric vessels and root of mesentery Duodenum – 3 rd part (10 cm) Dr Ndayisaba Corneille 15

16. Extends from front of aorta to Duodeno -jejunal flexure, which is situated on the left side of L2 about 1.25 cm below transpyloric plan and 2.5 cms to left of median plane Kept in position by suspensory muscle of Duodenum (Ligament of Trezt ) Relations Anteriorly : Covered with peritoneum. Related to transverse colon and its mesocolon PosteroInferiorly it is separated from the Surface of stomach by the lesser sac Duodenum – 4 th part (2.5 cm) Dr Ndayisaba Corneille 16

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18. Most of the duodenum except 1 st part is supplied by Ventral and dorsal anastomoses of Superior & Inferior Pancreaticoduodenal arteries. Vasa Recta arises and supply adjacent areas of duodenum and head of pancreas Duodenum – Arterial supply Dr Ndayisaba Corneille 18

19. Veins corresponding in name to the arteries, The veins drain into superior mesenteric vein and portal vein Duodenum – Venous drainage Dr Ndayisaba Corneille 19

20. Lymph vessels drain into pancreatico -duodenal lymph nodes. Efferent vessels of these nodes drain into Coeliac and superior Mesenteric group of pre-aortic lymph nodes. Some vessels drain into the Hepatic nodes directly. All lymph reaching hepatic nodes will still drain into the coeliac nodes Duodenum - Lymphatic drainage Dr Ndayisaba Corneille 20

21. APPLIED ANATOMY of the duodenum Cancer of the duodenum could be very severe and sometimes could not be easily controlled as a result of the numerous venous and lymphatic channels that exist between the duodenum and post abdominal wall. Duodenal ulcer: The duodenum especially the superior part (duodenal cap) is most prone to peptic ulceration and its frequency is about four times higher than gastric ulceration. Superior mesenteric syndrome: Based on the relation of the superior mesenteric artery to the anterior and superior part of the horizontal part of the duodenum. It could sometimes leads to compression of the duodenum which will lead to obstruction. Dr Ndayisaba Corneille 21

22. THE JEJUNUM AND THE ILEUA This remaining part of the small intestine is mainly involved in the absorption of digested nutrients and fluid from the chyme as a result it is involved in the conservation of fluid it is made up of series of coils that are attached to the posterior abdominal wall by a double layer of peritoneum which is referred to as Mesentery proper. Dr Ndayisaba Corneille 22

23. This mesentery arises by means of a root which is attached diagonally across the posterior abdominal wall extending from the left upper end to the right lower end of inter-colonic space. The root is about 15-20cm in length and it presents the route via which blood vessels, nerve fibres and lymphatic vessels reach the small intestine. Dr Ndayisaba Corneille 23

24. From the root of the mesentery to the point where it attaches to the small intestine is about 10cm and the mesentery entirely encloses the small intestine except at the region where it diverges to enclose the small intestine. The part where the mesentery attaches to the small intestine is known as the mesenteric border , while the anterior free part in relation to the anterior abdominal wall is referred to as the anti mesenteric border . Dr Ndayisaba Corneille 24

25. DIVISIONS OF THE PERITONEAL PART OF THE SMALL INTESTINE The jejunum forms the proximal 2/5 th of the peritoneal part of the small intestine and it lies mainly at the umbilical region though it does extend sometimes to the surrounding areas, The ileum forms the distal 3/5 th of the peritoneal part of the small intestine it then ends at the medial part of the junction between the cecum and the ascending colon. Dr Ndayisaba Corneille 25

26. It should be noted that since the duodenum and ileum share similar blood supply, common nerve supply, common mesenteric fold and similar function and based on the fact that there is no distinct demarcation between both of them, they are studied as a unit. Dr Ndayisaba Corneille 26

27. INTERNAL STRUCTURE OF JEJUNUM AND ILEUM The function of the small intestine is absorption. This is accompanied by some structural modifications that increase the surface area for absorption. They include: . Intestinal villi: They are highly vascular processes just visible to the naked eye and project from the entire intestinal mucosa giving a velvety texture, large and numerous in the jejunum and fewer in the ileum. Microvilli: cytologic modification of the luminal surface of the epithelial cells, it increases the surface area for absorption. Intestinal villi Dr Ndayisaba Corneille 27

28. Plicae circularis or valve of Kerkring : these are circular folds sometimes spiral fold of mucosa which projects into the intestinal lumen transverse to the long axis. They begin from the 2 nd part of duodenum and diminish midway along the ileum disappearing almost entirely at the distal ileum. The plicae circularis helps to slow down the passage of content thereby increasing the digestive and absorption time Dr Ndayisaba Corneille 28

29. BLOOD SUPPLY Arterial supply to the jejunum and the ileum is from the jejunal and ileum arteries. They are about 20 in number and as they pass into the mesentery proper they form anastomotic arcades with each other which ensures adequate collateral blood supply in case of constriction of arteries of certain region during peristaltic movement The arcades in the jejunum are larger but fewer that those of the ileum which are smaller and numerous. From the arcades arises straight branched arteries (arteriae rectal or vasa recta) which runs directly into the wall of the jejunum and ileum where they give of anterior and posterior branches in the sides of the viscus Dr Ndayisaba Corneille 29

30. The vasa recta usually anastomose on the mesenteric border but in the antimesenteric border they are more or less end arteries and when occluded they could lead to local infraction. It should be noted that the vasa recta of the ileum are shorter and more numerous than those of the jejunum. Also the ileum receives addition blood supply from the ileal branches of the ileocolic artery which is one of the terminal branches of the superior mesenteric artery. They supply the terminal part of the ileum. Dr Ndayisaba Corneille 30

31. VENOUS DRAINAGE The veins follow the arteries and they drain into the superior mesenteric vein which drains into the portal system. Dr Ndayisaba Corneille 31

32. LYMPHATIC DRAINAGE Lymphatics from the jejunum and ileum drain trough the lymphatic follicles of the mucous membrane through the muscle wall into the mesentery at the lymph nodes lying along the arterial arcades from these mesenteric nodes the lymph drain to the superior mesenteric group of pre-aortic lymph nodes which surrounds the Superior mesenteric artery behind the neck of the pancreas. They send efferent lymph vessels to the coeliac group of lymph nodes. Dr Ndayisaba Corneille 32

33. Sympathetic nerves are derived from coeliac and superior Mesenteric Plexuses. Parasympathetic are derived from the vagus nerves . The myenteric (Auerbach’s plexus) & Meisner’s plexuses Myenteric plexus of nerves and ganglia lies between the circular and longitudinal layers of the Muscularis externa. Then from this plexus fibers pass to form a second submucosa plexus ( Meisner’s plexuses ) Duodenum - Nerve supply Dr Ndayisaba Corneille 33

34. NERVE SUPPLY………………………………… In general the sympathetic system inhibits peristalsis but stimulates the sphincters and muscularis mucosae. The parasympathetic helps in peristalsis and inhibits the sphincters, it also argument intestinal secretions. It should be note that segmental and pendular movements of the small intestine is mainly controlled by enteric reflexes which are intrinsic and they give rise to the Bayliss-Starling law of the gut which states that a bolus of chyme exerting transverse pressure on the intestinal wall, results in muscular tone contraction immediately oral to the bolus and relaxation in the adjacent aboral region. This reflex mechanism ensures unidirectional oral to aboral flow of intestinal contents. Dr Ndayisaba Corneille 34

35. DISTINGUISHING FEATURES BETWEEN JEJUNUM AND ILEUM 1. Diameter Lager 2-4cm 2.5-3cm 2. Wall thicker & heavy thin & light 3. Vascularity Greater Less 4. Color Deeper red pale pink 5. Arterial vasa recta Long Short 6. Arcades Large loops (few) Small loop(many) 7. Fat in mesentery window Less More 8 Plicae Circularis well dev (numerous) Rudimentary (few) 9. Payer patches Few Many CHARACTERISTICS JEJUNUM ILEUM Dr Ndayisaba Corneille 35

36. APPLIED ANATOMY: Frequency of Borborygmi Frequency of Borborygmi: This is the sounds heard with a stethoscope applied to the abdominal wall. These sounds are brought about by segmental contraction of the intestine and movement of columns of chyme within the small intestine. These contractions are as a result of reflexes initiated by intestinal wall distention. The rate is about an average of10 constrictions per minute. It is of clinical significance. In surgery involving the abdominal organs such as kidney, appendectomy etc., there occur a condition known as Paralytic Ileus whereby all form of intestine movements are shut down, the emergence of frequency of borborygmi is an indication that bowel function has commence and so the patient can commence feeding through the mouth. Dr Ndayisaba Corneille 36

37. Meckel's Diverticulum This is a persistent remnant of the vitello intestinal duct of the embryo. It projects from the Antimesenteric border of the distal ileum in about 2% of subjects. It is about 2m above the ileoceacal junction and it’s average length is about 2 inches (5cm) with diameter similar to that of the ileum it’s terminal end is either free or connected with the abdominal wall by a fibrous band.   IMPLICATIONS It may become inflamed and presents symptoms which are similar to the symptoms of inflamed appendix and this might require surgical intervention. It is always sort for during appendectomy and it is always removed as a preventive measure. Dr Ndayisaba Corneille 37

38. THE LARGE INTESTINE It extends from the ileum to the anus. It reabsorbs water converting liquid chyme into semi solid stools. It consists of the following parts: 1)Caecum and vermiformis appendix. 2)Ascending colon and hepatic flexure. 3) Transverse colon and splenic flexure 4)Descending colon 5)Sigmoid colon 6) Rectum and 7) Anal canal. The proximal half as far as the splenic flexure – reabsorbs water and electrolytes from fluid chyme . The distal colon beyond the splenic flexure-stores formed faeces until they are excreted. Dr Ndayisaba Corneille 38

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40. CONTINUATION….. As the name implies ,the large intestine is wider than the small intestine. -Other features : I ) taenie coli . 3 whitish longitudinal muscle bands which start at the base of the appendix . These muscle bands pucker the large intestine and with the activity of the circular layer of muscles forms haustra or sacculations. 2) Appeandicess epiploicae- are fat filled pouches of serosa that are scattered over the surface of the large intestine. Dr Ndayisaba Corneille 40

41. Caecum . A wide cul-de-sac of gut below the caecal sphincter. It lies in the right Iliac fossa . Commonly it is completely invested with peritoneum and hangs free. Sometimes 2 vertical folds connect it to the posterior abdominal wall. It is the 1 st . Part of the large intestine and continues with ascending colon. Dr Ndayisaba Corneille 41

42. The appendix vermiformis. Dr Ndayisaba Corneille 42

43. The appendix is attached to the caecum to the point of convergence of the 3 tenia . On the surface of the abdomen, this point lies at Mc Burnys point, a point 1/3 way, the oblique line from anterior superior iliac spine and the umbilicus. This point is constant ,and it signifies the base of the appendix. The mesoappendix encloses the appendicular artery which is a branch of the ileal caecal artery. Both the length and position of the appendix are variable. The average length is 5cm, and the most common positions are retrocaecal and pelvic. Dr Ndayisaba Corneille 43

44. The Ascending Colon Continuous with the upper end of the caecum and it extends up to the hepatic flexure. It is retroperitoneal A peritoneal fold ,the Rt. Phrenico colic ligament connects the hepatic flexure to the diaphragm. The Rt. Lateral paracolic gutter separates the colon from the abdominal wall and the medial paracolic gutter is occupied by coils of jejunum and ileum. Dr Ndayisaba Corneille 44

45. Transverse Colon It is approximately 15” . It begins at the hepatic flexure and arches across the abdomen to the splenic flexure. It has a transverse meso colon. The splenic flexure is suspended from the diaphragm by the phrenico colic ligament. Relations : Anteriorly coils of the small intestine and greater omentum. Posteriorly –lateral border of the Left Kidney, the origin transversus abdominis muscle and the Quadratus lumborum, iliac crest and the left psoas muscle .The ILIO INGUINAL and Iliohypogastric nerves , the lateral cutaneous nerve of thigh and the femoral nerve also lie posteriorly. Dr Ndayisaba Corneille 45

46. Descending Colon It extends from the splenic flexure to the pelvic brim. It is about 12 inches long. It is reteperitoneal. Its 3 tineae are in continuity with those of the transvers colon The appendicae are very numerous. Dr Ndayisaba Corneille 46

47. Sigmoid colon. It is mobile and convoluted and has a mesentery. The root of the mesocoln forms an inverted V attached along the pelvic brim and then on the front of the sacrum. It is approximately 40 CM in length, but this is very variable, as it is a storage organ for faeces. In the tropics ,people eat a lot of high residue diet, a “REDUNDANT SIGMOID COLON “. This predisposes sigmoid volvulus. Dr Ndayisaba Corneille 47

48. Blood Supply . The colon gets its blood supply the superior and inferior mesenteric arteries. The superior mesenteric artery is the artery to the mid gut. It supplies colon up to the splenic flexure . THE inferior mesenteric artery is the smallest of the 3 trunks. I t is the artery to the hind gut and supplies the colon from the splenic flexure to the rectum. The branches of both superior and inferior mesenteric arteries supplying the colon anastomose freely with each other and form the Marginal artery of Drummond. Dr Ndayisaba Corneille 48

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50. Branches of superior mesenteric artery to the colon. 1)The ileocolic artery-It from the R. side of the of the superior mesenteric trunk low down in the base of the mesentery. It supplies the terminal ileum ,the appendix vermiformis and the caecum. It anastomoses freely with the R. Colic branch. 2)The Right Colic branch.-Arises in the root of the mesentery from the right side of Superior Mesenteric artery. It divides near the left side of the ascending colon into 2 branches :I )The descending branch runs down to anastomose with the colic branch of the Ileocolic artery. Ii) The ascending branch runs up across the inferior pole of the R. Kidney to the hepatic flexure where it anastomoses with a branch of the middle colic artery. From these 2 branches, multiple versa recta sink into the wall of the ascending colon to supply it. 3) The middle colic artery is the highest branch from right side of the S. mesenteric artery. It divides into right and left branches. THE LEFT BRANCH supplies the transverse colon to the splenic flexure ,where it anastomoses with L. colic artery. T he R. branch anastomoses with the R. colic artery ,and it supplies the transverse colon to the splenic flexure. Dr Ndayisaba Corneille 50

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52. The inferior mesenteric artery It is the smallest of the 3 trunks. It gives 3 branches. 1)the left colic artery –supplies the descending colon from the splenic flexure to the sigmoid colon The sigmoid branch –supplies the sigmoid colon. The superior rectal artery – supplies the rectum Dr Ndayisaba Corneille 52

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54. Venous drainage All the GIT is drained by the portal venous system to the liver. The names of the veins correspond with the named arteries. The ascending colon and transverse colon is drained by the superior mesenteric vein. The sigmoid colon and descending colon ,drains into the inferior mesenteric vein ,which in turn drains into the splenic vein. Dr Ndayisaba Corneille 54

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56. Lymphatic drainage Caecum ,ascending and transverse colon drain to the para colic nodes to the Superior mesenteric group of lymph nodes to the pre aortic lymph nodes. Descending colon and sigmoid colon drain into the inferior mesenteric group of lymph nodes to the para aortic lymph nodes Dr Ndayisaba Corneille 56

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60. END Dr Ndayisaba Corneille THANKS FOR LISTENING By DR NDAYISABA CORNEILLE MBChB,DCM,BCSIT,CCNA Contact us: [email protected]/ [email protected] whatsaps :[phone] / [phone]