最新:局部解剖学-结肠下区-文档资料.ppt
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1、Section 6 结肠下区 Infracolic Compartment,Infracolic compartment lies between transverse colon with its mesocolon and superior aperture of lesser pelvis.,It contains jejunum, ileum, cecum, vermiform appendix, colon and other viscera.,I. 空肠及回肠 Jejunum and ileum I)位置 Location Jejunum and ileum are continu
2、ous coiled part of small intestine, extend from duodenojejunal,flexure to cecum and occupy most part of infracolic compartment. They probably average about 56 meters in length.,Jejunum comprises upper 2/5 of whole length, and ileum lower 3/5. Jejunum located upper left abdominal cavity and ileum in
3、lower right. The small part of ileum usually passes also into pelvis., Meckel憩室 (Meckels diverticulum) Persistence of proximal portion of yolk sac (vitelline duct) common malformation of digestive tract (24%) more prevalent in males. About 25cm long and located 30100cm from ileocecal valve. Usually
4、asymptomatic but: May become,inflamed (mimicking appendcitis) or cause intestinal obstruction by compressing adjacent intestinal loops., II)肠系膜 Mesentery It consists of two layers of peritoneum, and contains jejunal and ileal blood vessels, as wall as lymph nodes and some fat. Mesentery is fan-shape
5、d and allows coils of intestine considerable freedom of movement.,Root of mesentery begins from duodenojejunal flexure, which somewhat at left side of second lumber vertebra. Its line of attachment to posterior abdominal wall extends obliquely downwards and ends to ileocolic junction, which is appro
6、ximately at level of right sacroiliac joint. It is about 15 cm in length., III) 血管 Blood vessels Entire jejunoileum is supplied by branches of superior mesenteric a., which arises from,abdominal aorta at level of L1, posterior to neck of pancreas. It descends anterior to horizontal part of duodenum
7、and enters root of mesentery to right iliac fossa. It gives off 1218 intestinal arteries from its left side to jejunoileum.,Jejunal and ileal arteries branch and anastomose with each other to form a series of arterial arcades, from which further branches,form a second, a third and even a fourth tier
8、 of arcades. Last tier of arcades send straight arteries to each side of small intestine.,Jejunum,ileum,Vasa recta,Veins of small intestine unite to form superior mesenteric v. and then join splenic v. to form hepatic portal v. posterior to neck of pancreas.,Jejunum and ileum,II. 盲肠和阑尾 Cecum and ver
9、miform appendix I)盲肠 Cecum is blind sac, first part of large intestine,with largest diameter and thinnest wall, usually lying in right iliac fossa, rarely in lesser pelvis or at a higher level, even to right colic flexure. It is about 68 cm in length and width. Superiorly, it joins ascending colon.,
10、Cecum is an intraperitoneal organ, almost surrounded by peritoneum. It is relatively mobile, and sometimes cecum have a short mesocolon, cecum becomes more mobile, called “mobile cecum”, and easily to herniate or volvulate.,Terminal ileum opens into medial and posterior aspect of cecum, and is partl
11、y invaginated into cecum to form folds above and below opening, called Ileocecal valve (回盲瓣). It takes part in preventing,reflux of cecal contents into ileum, and controlling speed of,elimination of ileal contents into colon., I)阑尾 Vermiform appendix is a narrow, blind worm-like tube, usually 68 cm
12、in length, 0.5cm in diameter, but extremes varying from 220 cm have been recorded. It opens into posteromedial aspect of cecum about 2 cm,below ileoceal valve ( orifice). Base of appendix lies at point of convergence of three colic bands (used as a guide to find appendix during operation).,Surface m
13、arking of base is at the so-called McBurneys point which is at junction of lateral and middle thirds of line joining right anterior superior iliac spine and umbilicus. This point represents,a fixed point on abdominal wall, it is area of greatest tenderness in appendicitis. Special position is rarely
14、 as high position appendix (under liver), extraperitoneal appendix, and left lower abdominal position appendix.,Appendix is entirely covered by peritoneum and has a triangular mesentery (阑尾系膜 Mesoappendix) which extends from terminal part of ileum to appendix. Tip of appendix is very variable in pos
15、ition, according to statistical data of Chinese people, frequently it lies at following position: Preileal position (in 28%), Pelvic,position (in 26%), Retrocecal position (in 24%), Retroileal position (in 8%), Subcecal position (in 6%).,Appendicular artery arises from ileocolic a. Most of appendicu
16、lar arteries are single (in 92%). It runs in free margin of meseoappendix then along wall of appendix.,Appendicular vein drains into hepatic portal vein via superior mesenteric veins. In clinic, when appendix becomes suppurative appendicitis, bacterial emboli may enter liver and hepatic,abscess. Dur
17、ing appendicectomy, do not extrude inflamed appendix to prevent infective emboli from entering into blood flow.,III.结肠 Colon I) Features of colon 1.结肠带 Colic bands There are three band-like longitudinal colic bands on wall of cecum and colon.,They converge at base of vermiform appendix and become co
18、ntinuous with its outer layer of muscle.,2.结肠袋 Haustra of colon Because lengths of colic bands are shorter than that large intestine, large intestine is typically sacculated, forming haustra of colon. 3.肠脂垂 Epiploic appendices They are small projecting,pouches of peritoneum filled with fat, and are
19、numerous on transverse and sigmoid colons, but are absent on cecum, appendix & rectum., II) Subdivisions of colon Colon includes ascending, transverse, descending and sigmoid colons. 1.升结肠 Ascending colon is about 15 cm in length. It is,continuous inferiorly with cecum and extends upwards to undersu
20、rface of right lobe of liver, where it bends sharply forwards and to left to form right colic flexure (结肠右曲), and is continuous with transverse colon.,2.横结肠 Transverse colon is about 50 cm in length, and is the most mobile part of colon. It extends across abdomen from right colic flexure to left col
21、ic flexure where it continues descending colon.,3.降结肠 Descending colon descends almost vertically from left colic flexure to sigmoid colon at left iliac crest. 4.乙状结肠 Sigmoid colon extends from descending colon to rectum at level of S3., III) Blood vessels of colon 1. Arteries Blood supply of colon
22、is in part through branches of superior mesenteric a., and in part through those of inferior mesenteric a,Right half of colon is supplied by branches of sup. mesenteric a Left half of colon is supplied by branches of inf. mesenteric a,Vessels from two sources usually meet at approximately left colic
23、 flexure. From ileocecum to terminal part of,sigmoid colon, an arterial arcade formed by anastomosis of colic branches of superior and inferior mesenteric arteries, is called colic marginal artery (结肠缘动脉) which gives longer and shorter branches to enter intestinal wall vertically.,2. Veins Venous dr
24、ainage of colon corresponds largely to its arterial supply.,Veins of ascending and transverse colons drain largely into superior mesenteric vein, and veins of descending and sigmoid colons into inferior mesenteric vein. The latter empties commonly into splenic vein.,IV. 肝门静脉 Hepatic portal vein I)特点
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