General outline of GIT

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General outline of GIT Powered By Docstoc
					                                        gastric glands
Salivary glands

  gall bladder
   biliary tree

                                                         intestinal glands

                  consists of
                      • digestive tract
                          • muscular tube
                              • lined by mucous membrane
                      • associated glands

  digestive system
Embryological background
  • forms the epithelial lining of the GIT and glands

Splanchnic mesoderm
  • forms the lamina propria, connective tissue,
    muscle and peritoneum of the gut

            ( Differentiation depends on a reciprocal
       interaction between the endoderm of the gut
             and surrounding splanchnic mesoderm )
4 principle layers
  mucosal layer
  • epithelium
  • lamina propria
  • muscularis mucosa
  submucosal layer
  muscular layer
  adventitia / serosal layer
serous membrane that lines the abdomino-pelvic cavity.

  Parietal peritoneum
   › lines the anterior and posterior abdominal wall,
     undersurface of the diaphragm and pelvic cavity.

  Visceral peritoneum
  › forms the partial or complete investment of the
Parietal peritoneum

Visceral peritoneum

   General peritoneal cavity

   Lesser sac
single layer of flattened “ mesothelial cells ”

various folds, or reflexions of the peritoneum
connect viscera to abdominal wall or to one
another and are named
  e.g. greater, lesser omentum
  e.g. mesoappendix, transverse mesocolon,
  sigmoid mesocolon, mesentery of small intestine
ligaments (not related to ligaments of muscels & tendons
peritoneal cavity
   potential space

   contain few ml of tissue
   fluid which lubricate
   adjacent surfaces so that
   organs can glide one over
   the other
  •   Greater sac
  •   Lesser sac (omental bursa)

   in male
  completely closed space
   in female
   fallopian tubes open into it
Body wall and cavity
 • wall is lined by peritoneum             retroperitoneal organ


   peritoneal organ         peritoneal cavity

 muscular tube
 begins at the lower
 boarder of pharynx at
 the level of 6thcervical
 vertebra / lower
 boarder of cricoid
 end at cardiac end of
 the stomach
 25 cm in length ( 10
 inches )
• traverse the superior and posterior
• pierce the diaphragm at the level of
   T10 by passing through oesophageal
• enter the abdomen
• joins the cardiac end of the stomach at
   the level of T 11

  parts of the
    cervical part
    thoracic part
    abdominal part
constrictions of oesophagus
  at its origin
  where it is crossed by left main bronchus
  OG junction
Nerve supply
  Sympathetic nerves
  › thoracic segment
  › vagus nerve through
    oesophageal plexus
Blood supply
  Inferior thyroid artery
  Branches from descending thoracic
  Branches from bronchial artery
  Lt. gastric artery
  Inferior phrenic artery
Venous drainage
 Inferior thyroid vein (cervical portion)
 Azygos vein ( thoracic portion ) *
 Lt. gastric vein ( abdominal portion) *

Lymphatic drainage
 deep cervical group of lymph nodes (cervical)
 posterior mediastinal nodes (thoracic)
 preaortic and coeliac nodes (abdominal)
  constrictions are important
  › in passing instruments
  › FB may hold up in these constriction sites
  › possible sites for strictures following swallowing of
  relationship with left atrium
  › can press and displace oesophagus
  › injury to left atrium ( fishbone )
  common site for portosystemic anastomosis
  ( oesophageal varices ) one of the common
  causes of upper GIT haemorrhage - H&M
Varicose veins
• dilated
• elongated
• tortuous
most dilated part of the
alimentary tract

interposed between the              S
oesophagus and duodenum
in the upper part of the
abdominal cavity lying          S
mainly in the epigastrium,
LHC and umbilical region with
much of it under cover of the
lower ribs
J – shaped, muscular bag
relatively fixed at both ends
› cardio-oesophageal junction
  left of mid line ( T10 ), 40 cm from incisor teeth
› pylorus
  right of the mid line ( L1 )

anterior wall, posterior wall (stomach bed)
fundus, body, incisura angularis, pylorus
greater & lesser curvature
peritoneal organ
› greater & lesser omentum
Mucosal fold rosette
Oesophagogastric angle
Right crus of diaphragm
Intra-abdominal oesophagus *
intra-abdominal pressure
  Posterior surface
    stomach bed ( Lt. crus & dome of diaphragm, Lt.
    adrenal gland, Lt. kidney, pancreas, spleen,
    splenic artery and transverse mesocolon )

    Lesser sac *

Anterior surface                                    S
lies undercover of Lt. costal margin        A
in contact with                                 K
    . diaphragm                                     C
                                       P & SA
    . Lt. lobe of liver
   . anterior abdominal wall
extend in between
liver and lesser
(gastrohepatic omentum)

gastroduodenal part
› right free margin where
  anterior and posterior
  layer of the peritoneum
  become continuous
› this forms the anterior
  boundary of the adidus
  to the lesser sac
diverticulum of the peritoneal cavity
behind the stomach
› it opens into the greater sac through a slit-like aperture
  ( epiploic foramen )

foramen Winslow is related
anteriorly to CBD, HA, PV,
posteriorly to IVC,                                      liver
superiorly to caudate process, stomach
inferiorly to duodenum.

                             Sp                      A

                                           general peritoneal cavity



        K                   K

                      gastrosplenic ligament

lienirenal ligament


                                                   K                         K
Blood supply

from coeliac artery
   › Lt. gastric
       Oesophageal branches
   › Splenic
       Lt. gastroepiploic artery,
       short gastric vessels
   › Hepatic
       Rt. Gastric artery,
       Hepatic artery
       superior pancreatoduodenal,
       Rt. gastroepiploic artery
Venous drainage

  the veins accompany
  the arteries
  empty into portal vein
  or into one of its
  prepyloric vein of
  Mayo is a tributary of
  the Rt. gastric vein
Lymphatic drainage
 Area I
 superior 2/3 rd. drain along Lt. & Rt. gastric vessels
 to aortic nodes
 Area II
 drain along gastroepiploic vessel to subpyloric
 nodes then into aortic nodes
 Area III
 along short gastric, splenic vessels, superior
 pancreatic nodes then into aortic nodes
                 cysterna chylae

   Lt. gastric nodes
  Rt. gastric nodes
                       aortic nodes
                                           I   splenic nodes

superior pancreatic nodes

          Subpyloric nodes
Nerve supply of the stomach
Parasympathetic nerves
 Left ( anterior ) vagus nerve
  › branches to cardia, lesser curvature
  › Hepatic branch
      pyloric branch ( Nerve of Latarjet )
 Right (posterior) vagus nerve
  › branches to both anterior and posterior aspect of the
  › coeliac branch
Sympathetic nerves
NG intubation
  › anterior ulcers perforate
  › posterior ulcer erode ( GIT bleeding )
     gastric ulcer erodes pancreas, splenic artery
     duodenal ulcer erodes gastroduodenal artery
  › Troisier’s sign
small intestine
 occupy most of the abdominal cavity
 most digestion, absorption occurs in the
 small intestine
  › duodenum (first part of small intestine)
  › followed by jejunum and ileum
      first part of SI, 25 cm (10 inches) long
      forms loop ( like a letter - C )
      concavity of the loop moulds around the
      head of pancreas and faces to the left
      fixed to the posterior abdominal wall &
      is covered by the peritoneum

attachment of transverse mesocolon
divided into               portal vein

  First part
  Second part       CBD
                          hepatic artery

  Third part
  Fourth part                   pancreas


                              SM vessels
jejunum and ileum
 occupy most of the abdominal cavity
 6 – 7 meter long
  upper 2/5th. jejunum
  lower 3/5th. Ileum
 entirely surrounded by mesentery consisting
 of two layers of peritoneum, contain blood
 vessels, lymphatic, and nerves
 root of the mesentery – ( left of L 2 –IC junction )

              < 2

        > 2              A

Blood supply
  › superior mesenteric artery
   ( jejunal and ileal branches )

Venous drainage
  › drained by superior mesenteric vein which
   join splenic vein to form portal vein
large intestine
 about 1.5 meter long
 parts of the large intestine
  › caecum, vermiform appendix, ascending colon,
   transverse colon, descending colon, sigmoid
   colon, rectum and anus

                                      DESCENDING COLON


        APPENDIX                      SIGMOID COLON
appendix, transverse colon, and sigmoid
colon are completely surrounded by
peritoneum and are provided with

caecum is surrounded by peritoneum

the rest ( ascending colon, descending
colon ) are retroperitoneal
characteristic features of colon
                                       *   *
  taenia coli
  bands of longitudinal
  sacculations / haustra
  appendices epiploiceae, small pouches
  of peritoneum filled with fat
 sac like blind pouch 5-7 cm long
 first part of the large intestine
 located in RIF, completely
 invested by peritoneum
 continuous with ascending colon
 ileum opens into it ( ileocaecal
 valve )
 about 2.5 cm inferior to ileocaecal
 junction, appendix opens into it
 retrocaecal recess
     (a small cal de sac lying posterior to
 the caecum)
vermiform appendix
    a narrow worm-like blind tube, 7 – 8 cm in length
    suspend by mesentery
     › triangular mesentery ( mesoappendix )
    the position of the appendix is variable, but
    position of the base is fairly constant at McBurney’s
    the three taenia coli converge to the base of the
(if the appendix is not obvious at surgery, follow
    taenia coli)
position of the appendix

    retrocaecal            64 %
    pelvic                 32%
    pre-ileal              1%
    post-ileal             0.5 %
    subcaecal              2%
blood supply
  appendicular artery, a branch of
  ileocolic artery
  runs in the free boarder of
  and enter the appendicular wall

                          TERMINAL ILEUM


                           APPENDICULAR ARTERY

ascending colon

 first part of the colon, about 15 cm in length,
 extend upward from ilelcaecal junction to right
 colic flexure
 lies on fascia iliaca and anterior layer of lumbar
 fascia, related to anterior surface of right kidney
 related to paracolic gutter and right infracolic
transverse colon

  45 cm long
  hanging from hepatic to splenic flexure with
  base of transverse mesocolon crosses the inferior
  pole of right kidney, second part of duodenum,
  pancreas and inferior pole of left kidney
  splenic flexure is higher than hepatic flexure
  attached to gastrocolic ligament and greater
descending colon

 about 30 cm long
 splenic flexure lie on the lateral surface of left
 kidney, and in contact with tail of the pancreas
 and spleen
 a fold of peritoneum “ phrenicocolic ligament ”
 attach the splenic flexure to the diaphragm
 related to left colic gutter
 more appendicies epiploiceae
sigmoid colon

 also known as pelvic colon ( lies in pelvic cavity )
 45 cm long ( variation )
 completely invested by peritoneum “sigmoid
blood supply of the colon

 superior mesenteric artery supply the colon up to
 proximal 2/3rd of transverse colon
  › ileocolic A, right colic A, middle colic A

 inferior mesenteric artery supply colon from the
 distal 3rd of transverse colon till anorectal junction
  › left colic A, sigmoid branches, superior rectal A
marginal artery
 the anastomotic branches near the inner margin of
 the whole colon form the “ arterial arcade ”
 marginal artery

 short vessels run into the gut wall

 the weakest link in the marginal chain of vessels lies
 near the splenic flexure , between the middle and
 left colic branches ( midgut – hindgut junction )
  marginal arteries

middle colic artery     IMA
  right colic artery

                          sigmoid branches
    ileocolic artery

                       superior rectal artery
venous drainage
  veins correspond to the arteries
  drain into portal vein via superior and inferior
  mesenteric veins
  portosystemic anastomosis

lymphatic drainage
  drain into superior and inferior mesenteric nodes
  through epicolic, paracolic, intermediate nodes
mesenteries of large intestine
 transverse mesocolon
   › double fold of peritoneum, suspending the transverse colon
     from the pancreas ( attachment )
   › contain middle colic vessels
  sigmoid mesocolon
   › inverted V shaped
   › left limb is attached to the pelvic brim
   › apex is situated right on the left ureter and division of Lt.
     common iliac artery
   › right limb passes from apex to SV 3
   › contain superior rectal vessels
terminal part of large intestine,
continuous with sigmoid colon above,
ends at anorectal junction below
starts at the level of third piece of
12 cm – 15 cm ( 5 inches ) long
  antero-posterior curvature
  › passes downwards, follow the sacral curve
  › in front of the tip of the coccyx
      ano-rectal junction is slung forward by U loop
      of puborectalis muscle
      posterior wall of the rectum appear to make a
      right angled bend at anorectal junction
lateral curvature                       1          3
› S – shaped in the
  coronal plane
› convexity two to the                  2
  right / one to the left
› sickle-shaped transverse
  folds (rectal valves)
   middle one is the largest –
   level with RV pouch

                                 Houston’s valve
peritoneal covering
  upper third
      anteriorly and laterally
  middle third
  posterior third
      devoid of peritoneum (retroperitoneum)
  already reflected over to bladder / uterus
  (lowest part of peritoneal cavity – 7.5 to 5.5 cm from anal
three taenia
broaden out and
form a complete
longitudinal layer
no haustrations
no appendices
no mesentery

                          TAENIA COLI
  base of bladder,
  seminal vesicles,
  fascia Denovillaries
  coils of small intestine
  vagina, fornix, cervix
  fascia Denovillaries
  coils of small intestine
Posterolateral relation
  lower three piece of sacrum and coccyx
  the pyriformis, levator ani and coccygeus muscles
  anterior rami of lower three sacral and coccygeal
  nerves, sympathetic trunk, pelvic splanchnic nerves
  branches of rectal vessels
  a strong condensation of connective tissue,
  Weldyer’s fascia
blood supply
  derived principally from superior rectal
  artery with contribution from middle and
  inferior rectal artery and median sacral
  correspond to the arteries,
  anastomose freely forming
  internal rectal plexus in the
  submucosa and external rectal
  plexus outside the muscular wall

  superior rectal vein drains into
  inferior mesenteric vein
  ( portal venous system )

  middle and inferior rectal veins
  drain into internal pudendal &
  internal iliac veins ( systemic
  venous system )
lymphatic from mucosa drain into
  › pararectal nodes
  › nodes along vessels supplying the rectum
    and then into
  › para-aortic nodes at the origin of the IMA

drainage is mainly upwards
  › upper half
    along SR vessels to inferior mesenteric nodes
  › lower half
    along middle rectal vessels to internal iliac
Nerve supply
  › from branches of the pelvis plexus, inferior
    mesenteric plexus along inferior mesenteric

  › From S 2, 3, 4 by pelvic splanchnic nerves
anus / anal canal

 last 4 cm of the GI tract

 muscular tube, made up of circular muscles
 consisting of internal and external sphincters

 composed of visceral and skeletal muscles
 inclined downward & backward to open at anal
 orifice in the perineum

 developed from post allantois gut and
• posterior
  mass of fibromuscular tissue “ anococcygeal body ”

• anterior
  perineal body

• lateral
  ischiorectal fossae

  these sphincters, assisted by the configuration of
  the mucous membrane, hold it continuously closed
  except for the temporary passage of faeces and

  anorectal ring is formed at the junction of levator
  ani, internal sphincter, external sphincter (
  continence ) ***
muscles of anal canal is describes as “ tube in a
funnel ”

the sides of the upper part of the funnel are levator
ani, and the stem of the funnel is the external
sphincter which is continuous with levator ani

the tube inside the stem of the funnel is internal
sphincter, thickened continuation of inner circular
layer of rectum

internally lies the submucosa and mucosa
 tube in a funnel    mucous membrane
                      inner circular muscle layer / internal sphincter
                        outer longitudinal muscle layer

  levator ani


external sphincter
                              superficial / middle

external anal sphincter

not to be regarded as separate entities
  deep part of external sphincter blend with
  puborectalis sling, internal sphincter and form
  anorectal ring

  the middle ( superficial ) part is elliptical, attached
  to the tip of the coccyx and perineal body

  subcutaneous part is a circular ring of fibres curve
  inwards to lie below the lower end of internal
internal anal sphincter

  thickened downwards continuation of inner
  circular muscle of rectum

  outer longitudinal layer of muscle fuse with the
  fibrous element of PR sling to form thin fibroelastic
  sheet       “ conjoint longitudinal coat ” which
  runs in between two sphincters

  strands from this sheet penetrate the internal
  sphincter and lower part of the external sphincter,
  fat of ischiorectal fossa, perianal membrane
mucous membrane
 upper half of anal canal is lined by columnar

 6 – 10 longitudinal ridges, anal columns, at the
 lower ends, these columns joined together by small
 horizontal folds, anal valves

 dentate line lies below this level ( pectinate line )

 variable zone of transition in between

 below is anoderm which is lined by keratinized
 stratified squamous epithelium
                    levator ani

                 anorectal ring

             internal sphincter
anal canal
               external sphincter
                                                      ANAL CANAL
 upper part of anal canal ( post allantois gut )

                                                             levator ani

                                                             external sphincter

                                                             internal sphincter

                           lower part of anal canal
ischio-rectal fossa
                            ( developed from proctodaeum )
the lining of

  the upper part of the anal
  canal is embryologically
  derived from cloaca,
  endodermal origin      (
  post allantois gut )

  the dividing line is
  considered to be at
  dentate line ( pectinate
  line )

  lower part is derived from
  proctodeum, ectodermal
blood supply

  branches of superior rectal
  artery terminating in anal

  small part of muscular wall is
  supplied by middle rectal
  and median sacral artery

  lower end is supplied by
  inferior rectal artery
venous drainage

 upper part drains via
 superior rectal and
 inferior mesenteric veins
 into portal system

 lower part drains into
 internal iliac veins
 through inferior and
 middle rectal veins
lymphatic drainage

  upper canal drains
  into internal iliac nodes

  lower end drains into
  superficial inguinal
Nerve supply
upper half of anal canal
   › supplied by sympathetic
     and parasympathetic
     nerves from inferior
     hypogastric plexus
   › sensitive only to stretch

lower half the anal canal
   › inferior rectal nerve,
     branches of internal
     pudendal nerve
   › sensitive for pain,
     temperature, touch and
Clinical application

  Rectum and anal canal
  › PR examination
  › Proctoscopy

  › Sigmoidscopy / colonoscopy
  › Barium studies ( barium enema X – rays )

  › TNM classification

  › Anatomical basis of colostomy
relations of rectum
Clinical conditions
  › Volvulus of sigmoid colon
  › Haemorrhoids
  › Carcinoma of rectum

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