anatomy of large intestine Flashcards
what is the extension of large intestine ?
Extends from the ileocecal junction to muco-cutaneous junction of the ANAL CANAL
what are the parts of large intestine ?
1.5 meters long
Cecum + appendix
ascending colon
Transverse colon
Descending colon
Sigmoid colon
Rectum
Anal canal
which parts of the colons are retroperitoneal and FIXED?
ascending and descending colon
IMMOVABLE cuz retroperitoneal
which parts of the colon are intra- peritoneal?
Transverse colon
sigmoid colon ( S shape )
THEY ARE MOVABLE inside the peritoneum
what suspends transverse colon?
transverse mesoclon
what are the characteristics of large intestine ?
Taeniae coli
Hustrations / sacculations
Appendics epiploicae
describe taeniae coli?
aggregations of the outer longitudinal muscle coat INTO 3 bands which are shorter than the rest of the wall
all the taeniae converge at the base of the appendix and distally extend up to sigmoid colon ( appendix doesnt have taeniae coli )
describe haustrations / sacculations ?
small pouches that are caused by the sacculations which five the colon a segmental appearance
these pouches from the longitudinal tenaie coli cuz they are shorter than the colon causing the colon to shrink
describe appendices epiploicae ?
fatty pouches projecting from the wall
where are appendices epiploicae absent?
cecum
Appendix
Rectum
what is the location of the appendix ?
Retrocecal ( BEHIND THE CECUM ) but has variations
so we follow the taenaie coli to until it terminates at the the appendix
what is the cecum?
Blind sac – Commencement of large intestine
what is the situation of the cecum?
Right iliac fossa
what envelopes the cecum ?
cecum is completely enveloped by the peritoneum
BUT NO MESENTERY ( FOLDS )
so its intra peritoneal
is the cecum movable ?
no
Even though its intra peritoneal and covered by the peritoneum it is not movable because the covering is not long enough to allow significant movement + NO MESENTERY ATTACHING IT TO THE POSTERIOR ABDOMINAL WALL TO FACILITATE MOVEMENT
what is medially to the cecum?
Ileum
what is above the cecum?
ascending colon – ( continuation )
where does vermiform appendix / diverticulum arise from ?
Posteromedial wall
what attaches the cecum to the later abdominal wall ?
cecal folds ( reflections of the peritoneum )
what are 3 bands of teniae coli ?
Mesocolic —> posterior with the transver mesocolon
omental —-> anterior with the greater omentum
Free ( no attachment ) —> Inferior
what attaches to the Mesocolic band of teniae coli?
Transverse and sigmoid mesocolon ( posteriorly )
what attaches to the Omental band of teniae coli?
omental appendices ( anteriorly with the greater omentum )
describe the course of greater omentum ?
The greater omentum initially has 2 layers as it descends from the stomach ( 1st and 2nd layers )
reflects back upward —-> 3rd and 4th layers
The 3rd and 4th layers encloses the transverse colon —> here its closely associated with tenia omentalis
After that the greater omentum splits again and FORM THE MESOCOLON —-> at this point its closely related to teniae mesocolica
what is the locations of teniaes on the ascending and descending colons?
omentalis —> postero - LATERAL
mesocolic —–> postero- MEDIAL
free / liberaa ———–> Anterior
what happens if mesentery is present in the cecum ?
its a congenital anomaly —> leads to twisting and volvulus
what we will find if we cut the transverse colon?
transverse mesocolon
what we will find if we cut the transverse mesocolon ?
lesser sac
describe the ileocecal junction ?
it is interiorly
the ileocecal orifice opens on the medial side of the cecum
what surrounds the ileocecal orifice ?
thickening of circular muscles —> ileocecal sphincter —> it is an anatomical sphincter
that prevents reflux from the cecum into the ileum
what guards the ileocecal orifice?
ileocaecal valve
what are the shapes of the valve ?
Labial form —> upper and lower lips due to loss of muscle tone —> in dead people
Papillary form —> papillae cuz of the muscle tone —> Seen in living people
how can we determine the place of obstructions in intestine using the cecum?
if cecum is bloated —> obstruction is in the large intestine
If cecum is empty —-> obstruction is in the small intestine
what is paracolic gutters?
peritoneum reflections on the lateral wall between the ascending/descending colon and the LATERAL ABDOMINAL WALL
may potentially accumulate fluid
what is a congenital anomaly that could happen to the ascending and descending colon?
Normally ascending and descending colon are retroperitoneal ( behind the peritoneum ) and it is fixed + NO MESENTERY
in some people with anomaly the ascending colon has mesentery
describe the vermiform appendix ?
Worm like blind narrow diverticulum
variable in length
from where does the vermiform appendix arise from ?
arise from the POSTEROMEDIAL aspect of the cecum
Inferior to the ileocecal orifice
is the appendix movable and why?
it is freely movable
because it has its own peritoneal covering called the mesoappendix
what is the mesoappendix ?
Triangular peritoneal fold
suspends the appendix
where does the mesoappendix come from ?
from the mesentery of the terminal ileum ( remember the ileum and jejunum are suspended by mesentery )
what does the mesoappendix contain ?
contain appendicular artery
what is the appendix lacking ?
No teniae coli
No sacculations
No appendices epiploicae
what are the peritoneal folds at the terminal ileum ?
1- Mesoappendix ( covering the appendix )
2- Superior ileocecal fold
3- Inferior ileocecal fold
what is the locations of superior ileocecal fold ?
in front of the terminal ileum
between the base of the mesentery and the anterior wall of the cecum
what is the space behind the superior ileocecal fold ?
Superior ileocecal recess
what does the superior ileocecal fold contain ?
Anterior cecal artery
what is the other name of inferior ileocecal fold ?
bloodless fold of treves because it has no blood vessels
what is the location of inferior ileocecal fold ?
small fold
extend from the terminal ileum to the front of the mesoappendix
what is the inferior ileocecal recess ?
space between the inferior ileocecal recess and the mesoappendix
what can happen to these recesses ?
hernia —> coils of small intestine may herniate
why does ischemia happen in cases of hernia in the superior ileocecal recess?
because the anterior cecal artery is there and it will get compressed by the hernia
Superior ileocecal hernia : 6-13% of all internal hernias
what are the branches of the left superior mesentery artery?
jejunal and ileal branches
what are the branches of the right superior mesenteric artery ?
Middle colic
right colic
ileocolic
what are the branches of ileocolic ?
colic branches ( ascending )
cecal branches ( descending )
what are the branches of the descending / cecal artery ?
Appendicular —> to the appendix ( through the mesoappendix )
Anterior cecal artery —> through superior ileocecal fold
Posterior cecal artery
Ileal branch / cecum branch
what does the ileal/cecum branch anastomosis with ?
the superior mesentery artery
what vessel was closely associated with the paraduodenal recess?
inferior mesenteric vein
what are positions of the appendix?
variable :
retrocecal — 65%
Pelvic —–> 30%
what is mcburney points?
location of the root of the appendix where its fixed in position
what is the location of mcburney points?
at the junction of the lateral 1/3 and medial 2/3 lines of the right spino - umbilical line
find the ASIS and the umbilicus and connect them together and at the point where the lateral 1/3 meets the medial 2/3 u will find it
what happens to mcburneys point in appendicitis?
digital pressure over the point causes maximum abdominal tenderness
what happens in appendicitis ?
inflammation
occlusion of narrow appendicular lumen
Secretions cannot escape
distensions of the wall
Pain fibers pass through sympathetic fibers —> Enter T10 segment of spinal cord –> Referred pain around the umbilicus
stretching of the visceral peritoneum
pain felt at the right iliac fossa - Right lower quadrant
what is the extension of ascending colon?
Ileocecal orifice
to
Right colic hepatic flexure
what are the characteristics of ascending colon?
Retroperitoneal – covered by peritoneum anteriorly on its side
may have MESENETERY ( in congenital anomalies ) in the inferior parts leading to volvulus
Paracolic gutter lies on the right side and connects SUPERIORLY to the right subphrenic space
what is the extension of transverse colon ?
Right colic hepatic flexure
to
Left colic splenic flexure
what suspends the transverse colon ?
transverse mesocolon
Suspends to the posterior abdominal wall
what is the phrenico colic ligament ?
fold of peritoneum attaches the splenic flexure to the diaphragm
what does the phrenic colic ligament prevent?
prevents fluid and infection from flowing from the LEFT PARACOLIC GUTTER to the LEFT SUBPHRENIC SPACE
where is the root of transverse mesocolon located?
anterior border of pancreas and extends to the duodenum ( 2nd part / descending part )
is the transverse colon movable ?
it is movable cuz it is inside the intraperitoneal
what is the extension of the root of mesentery?
duodenojejunal flexure
To
ileocecal junction
crosses :
3rd part of the duodenum
the aorta
inferior vena cava
right ureter
what is the extension of descending colon?
left colic splenic flexure
To
pelvic brim
continuous with sigmoid colon
what covers the descending colon?
peritoneum covers it anteriorly and on both sides forming paracolic gutter on the left side
what limits the spread of stuff from the left paracolic gutter to the left subphrenic area?
Phrenico colic ligament
what is the extension of sigmoid colon ?
pelvic brim
to
front of the 3rd sacral segment
what is the location of sigmoid colon?
S- shaped loop is variable length
situated in the LEFT ILIAC REGION
what suspends the sigmoid colon?
Sigmoid mesocolon
Peritoneal fold that suspends it from the posterior pelvic wall
variable in position
likely affected by volvulus
what is the root of sigmoid mesocolon ?
Inverted V shaped attachment
attaches the sigmoid colon to the posterior pelvic wall
is sigmoid colon intraperitoneal or retro?
intraperitoneal as it is entirely covered by peritoneum –> sigmoid mesocolon
like the the small intestine
what are the structures anterior the apex of sigmoid colon?
Left ureter
Bifurcation of the left common iliac artery
Left sacro-iliac joint
what is diverticulosis ?
mucosal herniation of the large intestine through muscle wall
usually in the sigmoid colon
what is the common location of diverticulosis ?
where nutrient arteries perforate the muscle coat to reach submucosa
what is the blood supply of colon?
branches from the right superior mesenteric artery:
Middle colic artery
Right colic artery
Ileocolic artery
what are the branches of ileocolic artery?
ascending branch / colic branch
descending / cecal branch
what are the branches of descending / cecal artery ?
Anterior cecal
Posterior cecal
Appendicular
Ileal
what does the ascending branch anastomosis with ?
right colic artery
what does ileal branch anastomosis with ?
Superior mesenteric artery
what does right colic artery divide into?
ascending —> middle colic
descending —–> ileocolic
anastomosis with the ileocolic and middle colic arteries
what happens to the middle colic artery?
enter transverse mesocolon
Supplies the right 2/3 of transverse colon
what is avascular window ?
the middle colic artery - leaves a large window to its left on the mesocolon
it is a site for election for surgical access to the lesser sac and posterior wall of the stomach
what is the first branch of superior mesenteric artery?
inferior pancreaticoduodenal artery
the appendicular artery is a branch of what?
two possible :
Descending / colic branch of the ileocolic artery
Posterior cecal artery
It is an end artery - vascular thrombosis may cause gangrene of the tip
what is the origin of inferior mesenteric artery?
Anterior aspect of the abdominal aorta
inferior to the duodenum and descends to the left
AT L3
what are the branches of inferior mesenteric artery?
Left colic artery
Sigmoid artery
Superior rectal artery
what does the left colic artery supply?
Supplies the transverse and descending colons
anastomosis with the middle colic and sigmoid arteries
Ascending branch of the left colic will anastomosis with middle colic
Descending branch of the left colic will anastomosis with the sigmoid
what does the superior rectal artery supply ?
rectum
upper 2/3 of anal canal
it is a continuation of inferior mesenteric artery BEYOND THE PELVIC BRIM
what is marginal artery ( OF DRUMMOND ) ?
continuous anastomotic arcade along the mesenteric border of the large intestine
provide a collateral circulation between branches of the superior and inferior mesenteric arteries that supply large intestine
what is arc of riolan?
Variant anastomosis between the middle colic and left colic arteries
Present in typical avascular window of the transverse mesocolon
if surgery assumes it empty he could damage this arc of riolan
what is the venous drainage of midgut?
Superior mesenteric vein
what is the venous drainage of hindgut?
Inferior mesenteric vein
what is the relation between splenic vein and inferior mesenteric vein?
Inferior mesenteric vein is a tributary of splenic vein
splenic vein join the superior mesenteric vein to form portal vein
describe the venous metastasis of colorectal cancer?
inferior mesenteric vein drain into splenic vein and superior mesenteric vein come together to form portal vein
this is how the cancer goes to the liver and etc
what are 3 structures we see in the right free margin of lesser omentum?
Hepatic artery
Common bile duct
portal vein
what is the sequal lymph flow of the colon?
1- Epicolic nodes –> found on the gut
2- Paracolic nodes —> along the mesenteric border
3- Intermediate / mesocolic nodes —> nodes along the colic arteries ( ileo,right,middle, left )
4- superior or inferior mesenteric nodes
5- drain into intestinal lymph trunk then to CRYSTERNA CHYLI
what is the relation of pre aortic lymph node group ?
related to the Three ventral branches of the aorta
what is the relation of para aortic / lumbar lymph nodes?
related to the lateral branches of the aorta
what are pre- aortic lymph nodes?
located anterior the aorta
include :
Celiac
superior mesenteric
inferior mesenteric
which lymph nodes are assigned to the foregut?
Celiac ganglion
Celiac lymph nodes
Which lymph nodes are assigned to the midgut?
superior mesenteric ganglion
superior mesenteric lymph nodes
what is the lymph nodes associated with hindgut ?
inferior mesenteric ganglion nodes
Inferior mesenteric lymph nodes
what are the para -aortic lymph nodes?
located laterally to the aorta
include nodes draining the kidneys, gonads , suprarenal — they are bilateral lymph-nodes/paired
what is the innervation of the colon derived from?
midgut and hindgut
what is the parasympathetic supply?
ascending colon + right 2/3rd of transverse colon —–> vagus nerve
left 1/3 of transverse + descending colon + rectum—-> pelvic splanchnic nerves
what is sympathetic supply of the colon ?
Spinal cord segment T10-L2
lesser lumbar splanchnic nerves
where do the lesser splanchnic nerves go?
Superior mesenteric ganglion —> for midgut derivates
Inferior mesenteric ganglion —-> for hindgut derivates
which are for the intestines and colon ( intestines are from hindgut and midgut )
lesser splanchnic nerve also send fibers to celiac and aortic renal ganglion for foregut
what the derivates of foregut ?
stomach
liver
Spleen
pancreas
All drain to celiac —> pre aortic
what are the derivates of midgut and hindgut ?
Intestines —> superior mesenteric and inferior mesenteric —-> pre aortic
