Modeling specification of Sigmoid colon

Modeling instructions =追加モデリング仕様(conservative)=
 * 1) Segmentation of colon
 * 2) * Cecum を区切る　（現在ileumとのjunctionの上縁まで　２つ目のハウストラの上縁で切断)
 * 3) *Splenic flexure はもっとも鋭角的に曲がるところなのでλ型に折り曲げ　厚みが減ったところで後ろ上の脾臓の近くまで引き上げる（transverse を左上がりにする）
 * 4) *transverseはこれでやや長くなる　　( anterior superior iliac crest の1.5倍程度　少なくとももっとも長い結腸文節）
 * 5) * Descending colon と　Sigmoid colon を区切る　場所はexternal iliac arteryのすぐ外側で高さは小骨盤の入口（小骨盤縁）
 * 変形
 * 1) *lesser pelvisの入口からsigmoid mesocolon の付着部を作り　external internal iliac 分岐点を頂点にしてS3正中まで伸ばす　（sigmoid arteryはこのmesocolonの中を通す）
 * 2) *Sigmoid colonは　可能なら　少しでも右まで伸ばして長さをかせぐ　25cm程度目安

Ileocecul valve はmacburney point の下なので　もう少し外下にずらせるこの位置はsigma の開始よりやや上です.

http://lifesciencedb.jp/bp3d/API/image.cgi?shorten=DKfSHbS1TzyeSb4juiKLPr8r&.gif　orange:umbillicus
 * With anatomography BP3Dver4.0

colon length
A peroperative comparison of Western and Oriental colonic anatomy and mesenteric attachments B. P. Saunders a, T. Masaki 2, T. Sawada 2, S. Halligan l, R. K. S. Phillips 1, T. Muto 2, C. B. Williams 1
 * The average colon is about 1.5 m long.
 * Lengths of the various parts are:


 * Sigmoid colon+rectum : 17-78cm, median 34cm  (if rectum is 12 cm sigmoid alone is 22cm)
 * Transverse colon: (25-87cm), median=45 cm where rt-lt spina iliaca ranges 19-42cm
 * Pubic symphysis(lower edge)-sigmoid/descending junction: 3-30cm, median=13cm

Wiki answer
 * Anal canal: 5 cm
 * Rectum: 12 cm (with covering peritoneum 8cm, without peritoneum (below peritoneal cavity)4 cm
 * Ascending colon: 15 cm
 * Descending colon: 25 cm
 * The splenic flexure is thus at around 72 cm from the anal verge
 * the hepatic flexure at around 117 cm.

Iliac colon (old name)

 * The iliac colon is the old name for distal half of descending colon in iliac fossa of pelvis.
 * The Iliac Colon (Fig. 1076) is situated in the left iliac fossa, and is about  12 to 15 cm. long.
 * The Iliac Colon begins at the level of the iliac crest, where it is continuous with the descending colon,
 * The Iliac Colon ends in the sigmoid colon at the superior aperture of the lesser pelvis.
 * The Iliac Colon curves downward and medialward in front of the Iliacus and Psoas muscles.
 * The Iliac Colon, as a rule, is covered by peritoneum on its sides and anterior surface only.

Sigmoid colon

 * The Sigmoid Colon (a.k.a. pelvic colon) forms a loop which averages about 40 cm. in length, (this is longer than other works av. 30cm = sigmoid)
 * The Sigmoid Colon begins at the superior aperture of the lesser pelvis,
 * The Sigmoid Colon passes transversely across the front of the sacrum to the right side of the pelvis;
 * The Sigmoid Colon then curves on itself and turns toward the left to reach the middle line at the level of the third piece of the sacrum
 * The Sigmoid Colon bends downward at S3 and ends in the rectum.
 * The Sigmoid Colon is completely surrounded by peritoneum, which forms a mesentery (sigmoid mesocolon),
 * sigmoid mesocolon diminishes in length from the center toward the ends of the loop, where it disappears, so that the loop is fixed at its junctions with the iliac colon and rectum
 * Behind the sigmoid colon are the external iliac vessels, the left Piriformis, and left sacral plexus of nerves;
 * in front, the sigmoid colon is separated from the bladder in the male, and the uterus in the female, by some coils of the small intestine.

Rect sigmoid junction

 * S3 level
 * sigmoid mesocolon ends
 * teniae coli ends
 * app. 15 cm from anus (rectum 12cm anal canal 3cm)

Rectum

 * The Rectum is continuous above with the sigmoid colon,
 * The Rectum ends in the anal canal.
 * From Rectum's origin at the level of the third sacral vertebra it passes downward, lying in the sacrococcygeal curve,
 * Rectum extends for about 2.5 cm. in front of the tip of the coccyx.
 * Rectum extends for a little below the tip of the coccyx.
 * Rectum extends as far as the apex of the prostate.
 * Rectum extends then bends sharply backward into the anal canal.
 * Rectum therefore presents two antero-posterior curves: an upper, with its convexity backward, and a lower, with its convexity forward. (逆S字）
 * Two lateral curves are also described, one to the right opposite the junction of the third and fourth sacral vertebræ, and the other to the left, opposite the left sacrococcygeal articulation; they are, however, of little importance.
 * The rectum is about 12 cm. long, and
 * at its commencement its caliber is similar to that of the sigmoid colon,
 * at The rectum's termination, caliber is dilated to form the rectal ampulla.

Inner wall of the rectum

 * The rectum has no sacculations comparable to those of the colon, but when the lower part of the rectum is contracted, its mucous membrane is thrown into a number of folds, which are longitudinal in direction and are effaced by the distension of the gut.
 * Besides these there are certain permanent transverse folds, of a semilunar shape, known as Houston’s valves.
 * Houston’s valves are usually three in number; sometimes a fourth is found, and occasionally only two are present.
 * One is situated near the commencement of the rectum, on the right side;
 * a second extends inward from the left side of the tube, opposite the middle of the sacrum;
 * a third, the largest and most constant, projects backward from the forepart of the rectum, opposite the fundus of the urinary bladder.
 * These Houston’s valves are about 12 mm. in width, and contain some of the circular fibers of the gut.
 * In the empty state of the intestine they overlap each other, as Houston remarks, so effectually as to require considerable maneuvering to conduct a bougie or the finger along the canal.
 * Their use seems to be, “to support the weight of fecal matter, and prevent its urging toward the anus, where its presence always excites a sensation demanding its discharge.
 * The peritoneum is related to the upper two-thirds of the rectum, covering at first its front and sides, but lower down its front only;
 * from the latter it is reflected on to the seminal vesicles in the male and the posterior vaginal wall in the female. http://lifesciencedb.jp/bp3d/API/image.cgi?shorten=8HHzmu41vCS1m4TLL5a8b4Pz&.gif
 * http://lifesciencedb.jp/bp3d/?shorten=HXDa8fSviuqyuOzyO9SHf4zG

ANAL CANAL
From wikipedia a rich article Prostate http://l.yimg.com/a/i/edu/ref/ga/l/1080.gif http://upload.wikimedia.org/wikipedia/commons/a/a1/Prostatelead.jpg
 * The Anal Canal begins at the level of the apex of the prostate,
 * The Anal Canal is directed downward and backward, and ends at the anus.
 * The Anal Canal forms' an angle with the lower part of the rectum, and
 * The Anal Canal measures from 2.5 to 4 cm. in length.
 * The Anal Canal has no peritoneal covering, but
 * The Anal Canal is invested by the Sphincter ani internus,
 * The Anal Canal is supported by the Levatores ani, and
 * The Anal Canal is surrounded at its termination by the Sphincter ani externus.
 * In the empty condition The Anal Canal presents the appearance of an antero-posterior longitudinal slit.
 * Behind The Anal Canal is a mass of muscular and fibrous tissue, the anococcygeal body (Symington);
 * in front of The Anal Canal, in the male, but separated by connective tissue from The Anal Canal, are the membranous portion and bulb of the urethra,
 * and the fascia of the urogenital diaphragm;
 * and in the female The Anal Canal is separated from the lower end of the vagina by a mass of muscular and fibrous tissue, named the perineal body.

REFERENCE
http://www.bmj.com/content/309/6951/382 http://www.bmj.com/highwire/filestream/424385/field_highwire_fragment_image_l/0/F1.medium.gif http://www.bartleby.com/107/Images/large/image1076.gif http://www.bartleby.com/107/Images/large/image1077.gif http://www.bartleby.com/107/Images/large/image1078.gif http://www.bartleby.com/107/Images/large/image539.gif http://www.bartleby.com/107/Images/large/image1040.gif http://www.netterimages.com/images/vpv/000/000/002/2210-0550x0475.jpg