FORTIETH EDITION
`
`nat om
`
`The Anatomical Basis of Clinical Practice
`
`EDITOR-IN-CHIEF
`Susan Stand ring PhD, osc, FKC
`Emeritus Professor of Anatomy
`King's College London
`London, UK
`
`SECTION EDITORS
`
`Neil R Borley FRCS, FRCS(Ed), MS
`Consultant Colorectal Surgeon
`Department of Gastrointestinal Surgery
`Cheltenham General Hospital
`Gloucestershire Hospitals NHS Trust
`Cheltenham, UK
`
`Patricia Collins PhD
`Associate Professor of Anatomy
`Anglo-European College of Chiropractic
`Bournemouth, UK
`
`Alan R Crossman PhD, DSc
`Professor of Anatomy
`Faculty of Life Sciences
`The University of Manchester
`Manchester, UK
`
`Michael A Gatzoulis MD, PhD, FESC,
`FACC
`Professor of Cardiology, Congenital Heart
`Disease;
`Consultant Cardiologist, Adult Congenital Heart
`Centre and Centre for Pulmonary Hypertension
`Royal Brompton Hospital, and the National Heart
`and Lung Institute, Imperial College
`London, UK
`
`Jeremiah C Healy MA, MB BChir, MRCP, FRCR
`Consultant Radiologist
`Chelsea and Westminster Hospital;
`Honorary Senior Lecturer Imperial College
`London, UK
`David Johnson MA, BM BCh, DM, FRCS(Eng)
`Consultant in Plastic, Reconstructive and
`Craniofacial Surgery
`Department of Plilstic ilnd Reconstructive Surgery
`Radcliffe Infirmary
`Oxtord, UK
`Vishy Mahadevan PhD, FRCS(Ed), FRCS(Eng)
`Professor of Surgical Anatomy and
`Barbers' Company Reader in Anatomy
`Raven Department of Education
`The Royal College of Surgeons of England
`London, UK
`Richard LM Newell BSc, MB BS, FRCS
`Honorary Consultant Orthopaedic Surgeon
`Royal Devon and Exeter Healthcare NHS Trust
`Exeter, UK
`Caroline 8 Wigley BSc, PhD
`Senior Honorary University Teaching Fellow
`College of Medicine and Dentistry Peninsula
`Exeter, UK
`
`CHURCHILL
`LIVINGSTONE
`
`ELSEVIER
`
`

`

`CHURCHILL
`LIVINGSTONE
`ELSEVIER
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`is an imprint of Elsevier.
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`COVER IMAGE
`'Tractography reconstruction of the perisylvian language pathways' from Catani
`M, Jones OK & ffytche DH, Ann Neural 2005; 57(1):8-16 with permission of John
`Wiley & Sons. After almost 120 years this tractography reconstruction of the
`language pathways has updated the anatomy of the language networks. Image
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`

`

`mall intestine
`
`CHAPTER 66
`
`~e sm<tll intestine consists of the duode num, jejunum and ileum. 'll
`xtends from the distal end of the pyloric canal to the ileoca.ecal valve,
`an overall length of 5 metres (3-7 metres) in the living adult. The
`duodenum extends up to the duodenojejunal junction, and the rema.in·
`ing small inLestine is often referred to as the 'small bowel', of which the
`proximal two-fifths is referred to as the jejunum and the distal three(cid:173)
`·finhs as the ileum. There is no clear distinction between the two parts,
`but there is a gradual change in morphology from the proximal to distal
`ends of the small bowel. The distal 30 ern or so of the ileum is often
`referred to as the terminal ileum, which has some specialized physio(cid:173)
`logical functions.
`The duodenum lies mostly in the upper retroperitoneurn. The
`jejunum and ileum occupy the central and lower parts of the abdominal
`cavity and usually lie within the boundary formed by the abdominal
`colon; they are attached to the posterior abdominal wall by a mesentery
`which allows considerable mobility of the loops of small bowel. In the
`supine position, loops of jejunum may be found anterior to the trans(cid:173)
`verse colon, stomach and even lesser omentum, whereas in the upright
`position, loops of ileum may descend into the pelvis anterior to the
`rectum and, in women, may occupy the rectouterine pouch. The upper
`jejunum and some ileum are often covered anteriorly by the greater
`omentum. The jejunum and ileum are covered by peritoneum on all
`but their mesenteric borders, here the adipose connective tissue of the
`mesentery abuts the muscular wall. The serosal peritoneum is continu(cid:173)
`ous with the peritoneum enclosing the tissues of the mesentery.
`Mesenteric fat covers 20% of the circumference wall of the ileum and
`somewhat less of the jejunum.
`
`The adult duodenum is 20-25 ern long and is the shortest, widest and
`most predictably placed part of the small intestine. It is only partially
`covered by peritoneum, although the extent of the peritoneal covering
`Varies along its length: the proximal 2.5 em is intraperitoneal, and the
`ll!mainder is retroperitoneal. The duodenum forms an elongated 'C'
`that lies between the level of the first and third lumbar venebrae in the
`SUpine position. The lower 'limb' of the C extends further to the left of
`the midline than the upper limb. The head and uncinate process of the
`Pancreas lie within the concavity of the duodenum which is 'draped'
`'Over the prominence formed from the lumbar spine, the duodenum
`~er~ore bends in an antero-posterior direction as well as following the
`Orm of a 'C'. The duodenum lies entirely above the level of the urnbili(cid:173)
`C:Us and is described as having four parts (Figs 66.1, 66.2).
`
`~T (SUPERIOR) PART
`~e first, and most mobile, part of the duodenum is about 5 ern long.
`a Stans as a continuation of the duodenal end of the pylorus and ends
`s~ th~ superior duodenal flexure. Peritoneum covers the anterior and
`d Per1or pan of its posterior aspect close to the pylorus, where the
`~odenum forms part of the anterior wall of the epiploic foramen. Here
`0~ lesser omentum is attached to its upper border and the greater
`'iii entum to its lower border. The first 2 or 3 ern have a bland internal
`~ llcosal .appearance and readily dlstend on insufflation during endos(cid:173)
`\fiPy. Thts pan is frequently referred to as the duodenal 'cap'. It has a
`~angular, homogeneous appearance during contrast radiology, shows
`one same pattern of internal rugae as the pylorus, and is often visible
`natain radiographs of the abdomen as an isolated triangular gas
`nu Ow to the right of the first or second lumbar vertebra. The duode-
`ll\ next passes superiorly, posteriorly and laterally for 5 ern before
`
`A
`
`8
`
`c
`
`"'r --"--t;"----- -- - Neck of
`gall bladder
`
`7""- -- Superior
`mesenteric artery
`.._~~~~~~=------Superior
`mesenteric vein
`
`.--- - - - Gastroduodenal
`artery
`
`Left renal
`vessels
`
`Right gonadal artery
`
`'Rik-- --
`
`-
`
`Left gonadal
`artery
`
`Fig. 66.1 A, The four parts of the duodenum. B&C, The relations of the
`duodenum: B, anterior surface; C, posterior surface.
`
`1125
`
`

`

`rge intestine
`
`CHAPTER 67
`
`!)1Jelarge intestine extends from the ileocaecal valve to the anus. Broadly
`aki ng. it lies in a curve which tends to form a border around the
`~:ps of small intestine that are located centrally within the abdomen
`(Figs 67.1, 67.2). The large intestine begins in the right iliac fossa as
`the caecum, from which the vermiform appendix arises. The caecum
`becomes the ascendi ng colon whidl passes upwards in the right lumbar
`region and h ypochondrium to the inferior aspect of 1:he liver where it
`bends to the left forming t\le hepatic fl exure (right colic flexure) and
`becomes the transverse colon. This loops acros the abdomen with an
`anteroinferior convexity until it reaches !:he left hypochondrium, where
`it curves inferiorly to form the splenic fle:Aure (left colic flexure) and
`becomes the descending colon, which proceeds through the left lumbar
`and iliac regions to become the sigmoid colon in the left iliac fossa.
`The sigmoid colon descends deep into the pelvis and becomes the
`rectum which ends in the anal canal at the level of the pelvic floor. The
`large intestine is approximately 1.5 m long in adults, although there is
`considerable variation in its length. Its calibre is greatest near the
`caecum and gradually diminishes to the level of the sigmoid colon. The
`rectum is largest in calibre in its lower third and forms the rectal
`ampulla above the anal canal.
`The large intestine differs from the small intestine in several ways:
`it has a greater calibre; for most of its course it is more fixed in position;
`its longitudinal muscle, though a complete layer, is concentrated into
`three longitudinal bands, taeniae coli, in all but the distal sigmoid
`colon and rectum; small adipose projections, appendices epiploicae,
`are scattered over the free surface of the whole colon (they tend to be
`
`absent from the caecum, vermiform appendix and rectum); the colonic
`wall is puckered into sacculations (haustrations ), which may partly be
`due to the presence of the taeniae coli, and which may be demonstrated
`on plain radiographs as incomplete septations arising from the bowel
`wall.
`The large intestine develops as a fully mesenteric organ. However,
`after the rotation of the gut tube in utero, large portions of it come to
`lie adherent to the retroperitoneum, which means that some parts of
`the colon are fixed within the retroperitoneum, and other parts are
`suspended by a mesentery within the peritoneal cavity. Those portions
`of the colon within the retroperitoneum are separated from other ret(cid:173)
`roperitoneal structures by a thin layer of connective tissue which forms
`an avascular field during surgical dissection, but which offers little or
`no barrier to the spread of disease within the retroperitoneum.
`The caecum may be within the retroperitoneum, but more frequently
`is suspended by a short mesentery. The ascending colon is usually a
`retroperitoneal structure although the hepatic flexure may be suspended
`by a mesentery. The transverse colon emerges from the retroperitoneum
`on a rapidly elongating mesentery and lies, often freely mobile, in the
`upper abdomen. The transverse mesocolon shortens to the left of the
`upper abdomen and may become retroperitoneal at the splenic flexure.
`Occasionally the splenic flexure is suspended by a short mesentery. The
`descending colon is retroperitoneal usually to the level of the left iliac
`crest. As the colon enters the pelvis it becomes increasingly more mes(cid:173)
`enteric again at the origin of the sigmoid colon, although the overall
`length of the sigmoid mesentery is highly variable. The distal sigmoid
`colon lies on a rapidly shortening mesentery as it approaches the pelvis;
`by the level of the rectosigmoid junction the mesentery has all but
`disappeared, so that the rectum enters the pelvis as a retroperitoneal
`
`Le~ iliac crest
`
`l'ig. 67.1 Overview of the abdominal colon and its relations.
`
`1137
`
`' - - -- - -- - - --
`
`-
`
`--Rectum
`
`

`

`LAHlil= IN I l=::i liNt=
`
`superior mesenteric plexus), which means that early inflammation in
`the caecum (typhlitis) results in similar visceral pain symptoms to those
`experienced in appendicitis.
`
`ASCENDING COLON
`
`The ascending colon is approximately 15 em long and narrower than
`the caecum. It ascends to the inferior surface of the right lobe of the
`liver, on which it makes a shallow depression, and then turns abruptly
`forwards and to tile left, at the hepatic flexure. It is a retroperitoneal
`structure covered anteriorly and on both sides by peritoneum . Its
`posterior surface is separated by loose connective tissue from tlle iliac
`fascia, the iliolumbar ligament, quadratus lumborum, the aponeurosis
`of transversus abdominis, and the anterior peri-renal fascia inferolateral
`to the right kidney. The lateral femoral cutaneous nerve, usually the
`fourth lumbar artery, and sometimes the ilioinguinal and iliohypogas(cid:173)
`tric nerves, lie posteriorly as they cross quadratus lumborum . Laterally
`the peritoneum forms the lateral paracolic gutter and medially the
`medial paracolic gutter (Fig. 67.21). The ascending colon possesses a
`narrow mesocolon for pan of its course in up to one-third of cases.
`Anteriorly it is in contact with loops of ileum, the greater omentum and
`the anterior abdominal wall.
`
`Hepatic flexure
`
`The hepatic flexure forms the junction of the ascending and transverse
`colon as the latter turns down, forwards and to the left. It is variable in
`position and usually has a less acute angle than the splenic flexure. The
`anterior surface of tile lower pole of the right kidney is posterior,
`the right lobe of the liver is superior and anterolateral (Fig. 67.22), the
`descending (second) pan of the duodenum is medial and the fundus
`of the gallbladder is anteromedial. The posterior aspect of the hepatic
`flexure is not covered by peritoneum and the gut wall is in direct contact
`with pararenal fascia . The hepatic flexure is often covered in the greater
`omentum which may be attached to the anterior surface both of the
`upper ascending colon and the proximal (right) end of the transverse
`colon.
`
`VASCULAR SUPPLY AND LYMPHATIC DRAINAGE
`Arteries
`Superior mesenteric artery
`The arteries to the caecum, appendix and ascending colon are so
`what variable, but all are derived from the superior mesenteric a::e(cid:173)
`via the ileocolic and right colic (when present) arteries (see Figs 67 ~ry
`67.13).
`. 1,
`
`Ileocolic artery
`l11e ileocolic artery arises fro m the right side of the s uperior mese,nte .
`artery in its upper half in the root of th e mesentery. It descends to ~c
`right beneath the parietal peritoneum towards the caecum and cross ~
`anterio r to the right ureter, gonadal vessels and psoas major to ent~
`the right iliac fossa. Although th e term inal distribution varies, the an er
`usually divides into a superior divisio n which runs superolat~(
`towards the ascending colo n where it a nasto moses with the right col/
`artery (o r right branch of the middle colic artery), and an inferior div·~
`1
`si an wh ich anastomoses with t.be final ileaJ branch of the distal sup
`_
`rior mesenteric anery. The inferior divisio n ap proaches the supen~
`border of the ileoco lic junction . It usually gives .rise to the followin;
`branches: ascend ing colic (which passes up on the ascending colon tO
`anastomose with the superior division), anterior caecal, posterior
`caecal (which usually gives rise to the appendicular artery) and ileal
`(which ascends to the left on the lower ileum, supplies it and anasto(cid:173)
`m?ses with the last ilea! bran~ of the supe.rior mesenteric artery
`(Ftg. 67.23 ). The caecum IS supplied almost entirely from the ileocolic
`artery.
`The ileocolic artery is the most prominent vessel in the lower right
`colic mesentery and traction on the caecum in the direction of the
`
`Third part of
`
`Inferior vena
`
`Transversus
`abdominis -
`
`-
`
`- - -
`
`Iliohypogastric
`nerve>- - - ----=--- 'f ,
`
`Ilioinguinal
`nerve• ---_;:--~-::--7-/
`
`Lateral femoral
`cutaneous nerve----...:.,..,£.(
`
`-:F---¥...:,_-
`
`Second part
`of duodenum
`
`Liver
`
`kidney
`
`HepaUc
`nexure
`
`1144
`
`Fig. 67.21 Posterior relations of the ascending colon.
`
`Duodenum, lhltd
`part
`
`e
`
`111
`d ~) al
`Fig. 67.22 Axlal CT Images of the ascending colon obtains e atic
`level of the mid ascending colon and (B) at the level of I he ~ :epatlc
`flexure, showing the relationship of t he ascending col~n an 5 tile
`flexure to the right lobe of the liver, the right and left ktdneY L~ulse
`part of the duodenum. and the gallbladder (supplied by Dr
`Chelsea and Westminster Hospital, London).
`
`

`

`Caecum, vermiform appendix and ascending colon
`
`parietal peritoneum and anterior to the right gonadal vessels, right
`ureter and psoas major. Sometimes it arises more superiorly and crosses
`the second part of the duodenum and inferior pole of the right kidney.
`Near the colon it divides into a descending branch, which anastomoses
`with the ileocolic artery, and an ascending branch which anastomoses
`with the right branch of the middle colic artery. These form the
`marginal artery in the area of the hepatic flexure from which vessels
`are distributed to the upper third of the ascending colon, and the right
`side of the transverse colon.
`Veins
`Venous blood from the wall of the caecum, appendix and ascending
`colon drains into mesenteric arcades and subsequently into segmental
`veins, which accompany their respective arteries and tend to follow
`variations in arterial drainage. The segmental veins drain into the supe(cid:173)
`rior mesenteric vein, which lies to the right of the mesenteric artery.
`
`Superior mesenteric vein
`The superior mesenteric vein receives one or more middle colic veins,
`the right colic vein and the ileocolic vein and drains into the ponal vein
`(see Figs 67.31, 66.12) .
`
`Ileocolic vein
`The tributaries of the ileocolic vein follow a broadly similar pattern to
`the branches of the ileocolic artery, and are formed from superior and
`inferior tributaries. The vein ascends alongside the ileocolic artery
`beneath the peritoneum of the ileocaecal mesentery and drains into the
`superior mesenteric vein. The inferior tributary receives appendicular
`veins (via the posterior caecal or ileocolic veins) and anterior and
`posterior caecal and ileal veins, and the superior tributary drains the
`ascending colic veins.
`Ascending tributaries of the ileocolic and right colic veins accom(cid:173)
`pany their respective arteries into the root of the mesentery and drain
`via the ileocolic vein into the superior mesenteric vein.
`
`Right colic vein
`The right colic vein is highly variable and may drain into the superior
`mesenteric vein directly, or the right gastroepiploic or inferior
`pancreaticoduodenal vein to form a 'gastrocolic trunk' which drains
`into the superior mesenteric vein, or it may be absent entirely.
`Lymphatics
`Lymphatic vessels originate from both anterior and posterior aspects
`of the colon and drain into nodes located along the branches of the
`ileocolic and the right colic arteries. Lymphatic drainage from the
`distal ascending colon and hepatic flexure may be predominantly to
`the nodes of the right colic artery. The lymphatic anastomoses are
`rich and the preterminal nodes for both routes of drainage are the
`ileocolic nodes, located close to the superior mesenteric artery (Fig.
`67. 15).
`Lymphatic vessels in the appendix are numerous and there is abun(cid:173)
`dant lymphoid tissue in its walls. From the body and apex of the
`appendix, 8-15 vessels ascend in the mesoappendix, occasionally inter(cid:173)
`rupted by one or more nodes. They unite to form three or four larger
`vessels which run into the lymphatic vessels that drain the ascending
`colon, and end in the inferior and superior nodes of the ileocolic
`chain.
`
`Fig. 67.24 Anatomical variants of the
`right colic artery.
`
`j
`h J Absent right colic artel)':
`
`r1or superior iliac crest will readily cause the vessel to 'tent' the
`~tile te!Y due to its direct course towards the caecum. This allows easy
`Jtli.'Se~fication of the vessel during laparoscopic surgery.
`tdeil~e appendicular artery descends behind Lhe terminal ileum to e nter
`1 esoa ppendix a short distance from the appe ndicular base (Fig.
`tJJt;). Here it gives off a recurrent branch, which anastomoses at the
`61· of the appendix w ith a b ra nch o f the posterio r caecal a rtery: the
`~~se omosis is sometimes extensive. The ma in append icular a rtery
`~~~a~aches the tip of the organ, at first near to, and then in the edge
`~pP ne mesoappendix. The terminal part of the artery lies on the wall
`O~~~e append ix and may be t~rombosed in app~ndicitis, which results
`O d'stal gangrene or necrosis. Accessory artenes are common, and
`Ill ~ individuals possess two or more arteries of supply to the
`nl~il ndix.
`JP~e arcades of the terminal ileal artery provide a collateral supply
`to the caecum via anastomoses with the ileal branch of the ileocolic
`
`~rtCIY·
`Rldht colic artery
`lt e right colic artery is a small vessel that is highly variable in its
`10my (Fig. 67 .24). Most commonly it arises as a common trunk with
`~e middle colic artery. Altern atively it may arise as a separate branch
`(rom the righ t side o f the superio r mesenteric arte ry, or from the ileo(cid:173)
`colic artery (when it is referred to as an accessory right colic artery), and
`O(t'!ISionaUy it may be absent. From its origin in common with the
`middle colic artery it passes towards the ascending colon, deep to the
`
`1 3
`
`- - - - Inferior division of
`ileocolic artel)'
`
`'------,T-- Mesenteric-terminal
`ileal anastomosis
`
`Terminal ileal artel)'
`
`'--__::__ ___ Periserosal-terminal
`ileal anastomosis
`
`Ileal branch
`Recurrent branch
`Appendicular artel)'
`The arteries of the caecum, vermiform appendix and
`colon.
`
`Accessol)' right colic artel)': 10%
`
`1145
`
`

`

`LARGE INTESTINE
`
`INNERVATION
`
`The sympathetic supply to the caecum, appendix and ascending colon
`originates in the intermed iolateral grey matter of the fifth to the 12th
`thoracic spinal segments. Preganglionic a'\o ns travel via the greater and
`Jesser splanchnic nerves to the coeliac and superior mesenteric plexuses
`where they synapse on neuron es in the coeliac and superior mesenteric
`ganglia; postganglionic axons form periarterial plexuses along the
`branches of the superior mesenteric artery, whence they are distributed
`to the walls of the colon .
`The parasympathetic supply to the caecum, appendix and ascending
`colon is derived from the vagus nerve via the coeliac and superior
`mesenteric plexuses.
`Referred pain
`The appendix and overlying visceral peritoneum are innervated by
`sympathetic and parasympathetic nerves from the superior mesenteric
`plexus. Visceral afferent fibres carrying sensations of distension and
`pressure mediate the symptoms of 'pain' felt during the initial stages
`of appendicular inflammation. In keeping with other structures
`derived from the midgut, these sensations are poorly localized ini(cid:173)
`tially, and referred to the central (periumbilical) region of the
`abdomen. It is not until parietal tissues adjacent to the appendix
`become involved in any inflammatory process that somatic nocicep(cid:173)
`tors are stimulated, and there is an associated change in the nature
`and localization of pain. The caecum and proximal ascending colon
`share a common innervation to the appendix (sympathetic and ·para(cid:173)
`sympathetic nerves via the superior mesenteric plexus); early inflam(cid:173)
`mation in the caecum (typhlitis) results in similar visceral pain
`symptoms to appendicitis.
`
`TRANSVERSE COLON
`
`The transverse colon is approximately 50 em long, and extends from
`the hepatic flexure in the right lumbar region across into the left hypo(cid:173)
`chondriac region, where it curves posteroinferiorly below the spleen as
`the splenic flexure. It is highly variable in length and position, as may
`be confirmed by radiological assessment, but it often describes an
`inverted arch, with its concavity directed posteriorly and superiorly.
`Near the splenic flexure an abrupt U-shaped curve may descend lower
`than the main arch. The posterior surface at the hepatic flexure is devoid
`of peritoneum and is attached by loose connective tissue to the front
`of the descending pan of the duodenum and the head of the pancreas.
`The transverse colon from here to the splenic flexure is almost com(cid:173)
`pletely invested by peritoneum . It is suspended from the anterior border
`of the body of the pancreas by the transverse mesocolon which is
`attached from the inferior pan of the right kidney, across the second
`pan of the duodenum and pancreas, to the inferior pole of the left
`kidney. The transverse colon hangs down between the flexures to a
`variable extent, and sometimes reaches the pelvis. Above it are the liver
`and gallbladder, the greater curvature of the stomach and the body of
`the spleen. The transverse colon is usually attached to the greater cur(cid:173)
`vature of the stomach by the gastrocolic ligament, which is in continuity
`with the greater omentum, lying anteriorly and extending inferiorly.
`Behind and below the transverse colon lie the descending pan of the
`duodenum, the head of the pancreas, the upper end of the small bowel
`mesentery, the duodenojejunal flexure and loops of the jejunum and
`ileum.
`The transverse mesocolon permits considerable mobility of the
`transverse colon: occasionally the colon may be interposed between the
`liver and the diaphragm (Chilaiditi syndrome), and may be mistaken
`for free intraperitoneal gas.
`
`SPLENIC FLEXURE
`
`The splenic flexure forms the junction of the transverse and descending
`colon and lies in the left hypochondrium, inferomedial to the lower
`pole of the spleen (Fig. 67 .25). It is anterior to the pancreatic tail, and
`also to the left kidney, from which it is separated by the anterior peri(cid:173)
`renal fascia. The splenic flexure often adopts a very acute angle such
`that the end of the transverse colon overlaps the beginning of the
`descending colon; there may be peritoneal and omental adhesions
`between the two structures. It lies more superiorly and posteriorly than
`the right hepatic flexure; the visceral peritoneum covering its lateral
`aspect is often attached to the diaphragm at the level of the 1Oth and
`11th ribs by the phrenicocolic ligament, which lies below the antero-
`
`146
`
`Hilum of spiiE >en -------~
`
`Tail of pancreas ----~
`
`Fig. 67.25 Relations of the splenic flexure.
`
`lateral pole of the spleen. Its position with respect to the spleen In
`variable: it usually lies directly inferomedial to the lower pole, 'fo rm ins
`the colic impression, but it may lie anterior to the splenic hilum, an4
`even a little above. In these cases, the visceral peritoneum is ofta\
`adherent to the splenic capsule or hilar connective tissue; inad'lert
`downwards traction on the splenic flexure during surgery may fli~r thl
`capsule or hilar vessels. It may lie 'low' in the splenorenal rec~s 1\'ldi;
`no direct attachment to the splenic capsule.
`
`VASCULAR SUPPLY AND LYMPHATIC DRAINAGE
`Arteries
`The proximal two-thirds of the transverse colon is supplied ~
`superior mesenteric artery via the middle colic artery (Fig. 67.11~·
`distal third is usually supplied by the ascending branch ?f .the le
`artery via the marginal artery of the colon, although tl11S IS sornei\IDIIII[I I
`variable.
`
`Middle colic artery
`The middle colic artery usu·a!Jy arises fTO m the anterolateral
`the superior mesenteric artery, either separately or as a
`with the right colic arteJY. just inferior to the uncinate
`pancreas and anterior to the third pan of the duode•~um.
`passes inferiorly, then tums to run anteriorly and supenorly
`root of the transverse mesocolon, just to the right of the m dl
`usua ll y divides into a right and left brand1. The right bran ose
`moses with the right coli.c artery, and the left branch ~nast.on~~ (;m·
`the left colic artery. 1l1e arterial a.rches thus forn:ed he 3 °~idd)f?
`the transverse colon, which they supply. Some_umcs the ~verse
`artery divides into three or more branches withm Ule trail terinl
`colo n, in which case the most lateral branches form _ tl:~:r 11111,y
`tomoses. An accessory or rarely a replaced middle col•c ' . ~ left
`from the dorsal pancreatk, hepatic, inferior mesentcnc If or
`·
`a rteries (Fig. 67.26). In the larter two instances the le~t ha the
`the transverse colon will derive its arterial supply rom
`mesenteric artery.
`Veins
`Superior mesenteric vein
`"ddle colic
`The superior mesenteric vein receives one or more 0:1
`t coliC
`and the ileocolic vein (see Figs. 67.31, 66 .12) . The ng 1
`1
`
`

`

`B
`
`c
`
`Dorsal pancreatic artery
`
`Hepatic artery
`
`Superior mesenteric
`artery
`
`Sigmoid colon
`
`Fig. 67.26 Variants in the origin of
`the middle colic artery: only
`replaced arteries have been
`illustrated for simplicity.
`Accessory arteries are more
`common in each case than
`complete replacement of the
`origin. A, Left colic artery or
`inferior mesenteric artery (<5%).
`B, The dorsal pancreatic artery
`(<5%). C, Hepatic artery (<5%).
`
`absent or drains as a tributary to the right branch of the middle
`
`colic veins
`tributaries drain into one or more middle colic veins which are
`variable in extent and position. The middle colic veins drain
`the superior mesenteric vein, just before its junction with
`vein, or directly into the hepatic portal vein.
`
`drain into nodes along the middle colic arteries and then
`superior mesenteric nodes. The predominant lymphatic drain(cid:173)
`the splenic flexure is usually via nodes along the left colic artery
`drain into the inferior mesenteric nodes: this arrangement is
`on the arterial supply to the distal third of the transverse
`
`ON
`lilt Jiro~:im:a l two-thirds of the transverse colon is innervated by sym(cid:173)
`parasympathetic nerves via the superior mesenteric plexus.
`third usually receives a sympathetic supply from the inferior
`plexus and a parasympathetic supply that is derived partly
`the inferior mesenteric plexus and partly from retroperitoneal
`which travel in the pelvic splanchnic nerves that arise from
`in the second, third and fourth sacral spinal segments. The
`nerves are inhibitory to mural muscle in the transverse
`fibres are vasoconstrictor to the colic vasculature. Parasym(cid:173)
`are secretomotor to colic glands and motor to the
`nlt•mtJscul<tture.
`
`~·escE~ndino colon is a pproximately 25 an lo ng. It descends thro ugh
`hypocho ndrium and Lu mbar region, initi ally following the
`border of the lower po l of th e left ki dney, and then d escending
`between psoa s majo r and quad ratus lumborum to the iliac
`curves infero medi ally, lying a nterior to iliacus a nd psoas
`iliac crest
`become the sigmoid colo n below the lev