Anatomy of Digestive Sys Large Intestine

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ANATOMY OF DIGESTIVE SYSTEM – LARGE INTESTINE

Dr. Hermizi Hapidin

School of Health Sciences

Universiti Sains Malaysia

erm z c .usm.my 1st March 2012



At the end of this lecture the students should understand:

a) Embryology of digestive system

b) Subdivisions of large intestine

c) Anatomy of cecum & appendix

sigmoid)

e) Anatomy of rectum

na omy o ana canag) Histology of large intestine

h) Blood supply of large intestine



Three Embryonic Germ Layershree Embryonic Germ LayersEmbryonic Germ Layers = the three primary layers of cells of t e em ryo ecto erm, meso erm en o erm , rom w cthe tissues and organs develop.



GUT



DEVELOPMENT OF DIGESTIVE SYSTEM During 4th week of development, cells of

endoderm form cavity called primitive gut

Primitive gut elongates & differentiates into :

a) Foregut (anterior)

b) Midgut (intermediate)

c) Hindgut (posterior)

Foregut develops into pharynx, esophagus,stomach & part of duodenum (1st & 2nd parts)

Midgut - remainder of duodenum, jejunum,ileum & portions of large intestine (cecum,appendix, ascending colon & right 2/3 of

transverse colon)

Hindgut - reminder of large intestine (left 1/3 of transverse colon descendin colon si moidcolon & rectum), except for portion of anal

canal (derived from proctodeum)



Primitive Gastrointestinal System

Celiac trunk

MIDGUT

HINDGUT

Superior Mesenteric artery

Inferior Mesenteric artery

The boundaries of the foregut, midgut and hindgut are determinedby their respective blood supply



Primitive Gastrointestinal System

DIVISION ARTERY VEIN LYMPHATICS SYMPATHETIC PARASYMPATHETIC

FOREGUT

CELIAC ARETERY

PORTAL VEIN

Spleenic vein

Gastric vein

CELIAC NODES CELIAC GANGLIA VAGUS

MIDGUT SUPERIOR

MESENTERIC ARTERY

SUPERIOR

MESENTERIC VEIN

SUPERIORMESENTERIC

NODES

SUPERIORMESENTERIC

GANGLIA

VAGUS

HINDGUT

INFERIOR

MESENTERIC ARTERY

INFERIOR

MESENTERIC VEIN

INFERIOR

MESENTERIC

NODES

HYPOGASTRIC

PLEXUS

PELVIC SPLANCHNIC

NERVES



DIGESTIVE SYSTEM - LARGE INTESTINE

Mouth oral cavitParotid gland

Tongue

Submandibulargland

Salivary

glands

Esophagus Pharynx

StomachPancreas

Liver

Gallbladder

(Spleen)

DuodenumJejunumIleum

Smallintestine

Descending colonAscending colonCecum Large

Anus

Rectum

Vermiform appendixAnal canal



Functions of Large Intestine

1. Haustral churning, peristalsis and mass peristalsis drivethe contents of the colon into the rectum

2. Bacteria in the large intestine convert protein to aminoacids, break down amino acids & produce some Bv am ns v am n

3. Absorbing some water, ions & vitamins

.

5. Defecation (emptying the rectum)

LI - receives ~ 500 mL of in estible food residue er da

reduces to 150 mL of feces – by absorbing water & salts& eliminates feces by defecation



LARGE INTESTINE

General descri tion

Terminal portion Extends from ileum to the anus

Length: It is about 1.5 meters long

Diameter: 6.5 cm

Can be distinguished from small intestine by :Teniae coli (3 thickened bands of muscles – cecum & colon)

austra saccu at ons o co on etween ten aeOmental appendices (small fatty projections of omentum)

Caliber (internal diameter is much larger)



LARGE INTESTINE

Omental

appendices

Haustrum

Teniae coli



LARGE INTESTINE

Teniae col i

Teniae coliHaustra

by longitudinal fibers of smoothmuscle in muscular coat of large

extending from vermiform

appendix to rectum ey are v s e an can e seen

on outside surface of ascending,transverse, descending & sigmoid

co ons teniae coli contracts length wise to

produce haustra (bulges in colon)



SUBDIVISION OF LARGE INTESTINE

It consists of :

Colon Rectum

na cana

Transverse colon

Ascending colon

Descending colon

CecumSigmoid colon

Rectum

Anal canal

Vermiform appendix




Transverse colon

Ascending colonDescending colon

Cecum

Vermiform appendix

Sigmoid colon

Rectum

Anal canal




Left colic(splenic) flexure

Transverse

Right colic(hepatic)flexure

mesocolon

Epiploicappendages

Transverse

colon

Superior

Descendingcolon

arteryHaustrum

Teniae coli

Cut edge ofmesentery

colon

IIeum

IIeocecal

Sigmoidcolon

valve

Vermiform a endix

Cecum

External anal sphincterAnal canal



LARGE INTESTINE - CECUM

The beginning of large intestine that is continuous with ascendingcolon

Blind-ended pouch that is situated in right iliac fossa & rest iniliacus muscle

Attached to its posteromedial surface is the appendix



LARGE INTESTINE - APPENDIX

Vermiform appendix (vermi = wormlike, form = shaped)

Narrow & muscular tube containing a large amount of lymphoid tissue

Varies in length from 8 – 13 cm

Mesentery of appendix = mesoappendix (attaches appendix to inferior

Mesoappendix contains appendicular vessels & nerves

Mesentery = A fold

of peritoneum thatconnects intestines

to posteriorabdominal wall



LARGE INTESTINE - APPENDIX

Ileum

Appendix removed after appendectomy

Appendiculararter

Mesoappendix

Cecum Appendix



CECUM & APPENDIX

ileocecal valve, ileocecal orifice & opening of vermiform appendix



LARGE INTESTINE - COLON

The open end of cecum merges with long tube calledcolon = food assa e

Is divided into 4 parts :a) Ascending Transverse

b) Transverse

c) Descending

d Si moidAscending Descending

Sigmoid



a) Ascending Colon

It is about 13 cm long

Situated in right lower quadrant(right lumbar region)Liver

Ascending

ex en s rom cecum o un ersurface of liver, where it turn to

left & form right colic flexure or

colon

Transverse

colon

hepatic flexure and continuouswith transverse colon

Right colic flexure / hepatic flexure

Left colic flexure / splenic flexure

Lies retroperitoneally along rightside of osterior abdominal wall



b) Transverse Colon


Is the largest & most mobile part of Spleen

large intestine

Extends across abdomen & Transverse colon

It begins at right colic flexure

It hangs downward & suspended

Descendingcolon

by transverse mesocolon

Then, ascends to left colic flexureor s lenic flexure below s leen

(where it bends inferiorly tobecome descending colon

mobile than right colic flexure



b) Transverse Colon

(fold of peritoneum,which connects the

Transversemesocolon

transverse colon to

the posterior wall ofthe abdomen)



c) Descending Colon


Lies in left u er & lowerLeft colic flexure / s lenic flexure

quadrants (left lumbar region)

It extends downward from left


it becomes continuous with

sigmoid colon

Descending

colon

Peritoneum covers anterior & lateral sides and binds it toposterior abdominal wall

Sigmoid

colon

Red line: Pelvic inlet/pelvic

1. Sacrum

2. Ilium3. Ischium4. Pubic bone

r m e upper m o epelvic cavity)

. u c symp ys s

6. Acetabulum7. Foramen obturator

8. Coccyx



d) Sigmoid Colon

It is about 25 - 38 cm lon

It begins as a continuation of descending colon in front of pelvic

Below, it becomes continuous with

rectum in front of third sacralver e ra ver e ra

It is mobile & hang down intopelvic cavity in form of a loop


Left colic flexure / splenic flexureTransverse

colon

Is attached to posterior wall by fan-shaped sigmoid mesocolon



d) Sigmoid Colon

Greater om entum

Transverse colon

Descending colon

mesoco lon

e unumMesentery

Sigmoidmesoco lon

Sigmoid colon



LARGE INTESTINE - RECTUM

It begins in front S3 vertebraas a continuation of sigmoidco on

It passes downward, following

curve of sacrum & coccyx It ends in front of tip of coccyx

by piercing pelvic diaphragm & becomes continuous with anal

canal

Sagittal view



LARGE INTESTINE – RECTUM

Lower part of rectum is dilatedo orm rec a ampu a w ere

feces are stored until they areeliminated via the anal canal)

Has three lateral curvatures :

• Upper curve

-

• Middle curve

- convex to left

• Lower curve- convex to right




Ampulla of rectum




Upper curve

Middle curve

Lower curve




Peritoneum covers anterior & lateral

anterior surface of middle third Lower third of rectum devoid of

Muscular coat is arranged in outer

longitudinal & inner circular layers of Transverse

smoo musc e

Taenia coli (sigmoid colon) come together,so that longitudinal fibers form a broad

rec a o

band on ant & post surfaces of rectum Mucous membrane together with circular

muscle layers forms transverse folds of rectum (semicircular permanent folds)



LARGE INTESTINE – ANAL CANAL

Terminal part of large intestine

It is about 2.5 to 3.5 cm long Rectal valve

Anal canal

Rectum

backward from rectal ampulla

to anus

Hemorrhoidalveins

Levator animuscle

It surrounded by internal andexternal anal sphincters

Its lateral walls are ke t in

sphincter

External analsphincter

apposition by levator animuscles & anal sphincters Anal columns

Analsinuses

Anus

Frontal section of anal canal




Interior of anal canal

characterized by series of longitudinal ridges - anal columns Rectal valve

Anal canal

Rectum

anal columns

Inferior ends of anal columns are

Hemorrhoidalveins

Levator animuscle

o ne y ana va ves

Superior to valves are smallrecesses – anal sinuses

sphincter

External analsphincter

Inferior comb-shaped limit of analvalves forms an irregular line –pectinate line (indicates unction of

Anal columns Anal

sinuses

Anus

upper & lower parts of anal canal) Frontal section of anal canal



Interior of Anal Canal

Anal columnsor Columns of

Morgagni

Upper part of anal canal(mucous membrane linedby columnar epithelium)

ec na e or

dentate line Lower part of anal canal(mucous membrane lined by

stratified squamous epithelium)Superficial

Deep

Subcutaneous




Anal canal has 2 sphincters :a) Internal anal sphincter

b) External anal sphincter

Internal sphincter

•

• formed by thickening of circularmuscle coat

-

of anal canal

• innervated by parasympathetic




External sphincter

an arge vo un ary sp nc er

forms broad band on each side of inferior two-thirds of anal canal

can be divided into 3 parts ;

• subcutaneous

canal & has no bony attachment

• superficialExternal

as ony a ac men

• deep

encircles upper half of anal

sp nc er

Subcutaneous

Superficial

Deep

canal & has no bony attachment

ANAL SPHINCTERS



Rectal valve

ANAL SPHINCTERS

Rectum

Hemorrhoidal

Anal canal

Levator ani

muscle

External anal

sphincter

Anal columns

nterna anasphincter

Anal sinusesPectinate line

Internal anal sphincter—smooth muscle

External anal sphincter—skeletal muscle



Anterior view of Sigmoid Colon, Rectum & Anal Canal

Rectosigmoidunc on

Sigmoid colon

Teniae coli (free taenia)

Fibers of taenia spread to form longitudinal muscle of rectum

Fibers from longitudinal muscle join circular muscle layer

Rectum

Levator ani muscle

Parts of external analDeep

Superficial

Analcanal

Subcutaneous

Fibrous septum

Perineal skin



HISTOLOGY OF LARGE INTESTINE

Wall of large intestine contains typical 4 layers found in GI tract ;

a) Mucosa

b) Submucosa

c) Muscularis

Mucosa consists of epithelium, lamina propria with intestinal

glands (crypts of Lieberkuhn) & muscularis mucosae Submucosa consists of areolar CT

Muscularis consists of external layer of longitudinal smooth

longitudinal muscles are thickened & forming teniae coli) Serosa layer of large intestine is part of visceral peritoneum

to teniae coli = epiploid appendages)




Crypts of Lieberkuhn (intestinal glands) are simple, tubular glands which arise as

evaginations into the mucosa of the intestine (small and large intestine)




Villi are absent and the crypts appear deeper than the ones you observed in small

intestine. Goblet cells are numerous



Differences between Small & Large Intestine




Small Intestine Large Intestine

Mobile (except duodenum) Fixed (ascending &

descending colon)

No fatty tags Has appendices epiploicae

Wall of SI is smooth Wall of LI is sacculated

Has licae circulares No licae circulares

Mucous membrane has villi Absent of villi

Has Peyer’s patches No Peyer’s patches




Jejunum

I eum

Colon



BLOOD SUPPLY OF LARGE INTESTINE

Cecum

Arteries

• Anterior and posterior cecalarteries from ileocolic artery

Ileocolic artery

(branch of superiormesenteric artery)

VeinsPosterior cecal

artery

• Veins correspond to arteriesand drain into superior

Anterior cecal arteryCecum




Vermiform appendix

Arteries

• Appendicular artery (branchof posterior cecal artery) – itpasses to tip of appendix inmesoappendix

VeinsPosterior cecal

artery

• Appendicular vein drainsinto posterior cecal vein Appendicular artery




Ascending colon

Arteries

• Ileocolic & right colic

mesenteric artery

Veins Ascending

colon

• Veins correspon to arteries& drain into superiormesenteric vein




Transverse colon Transverse colon

Arteries

• Proximal two-thirds issu l b middle colic arter

Middlecolic artery

(branch of superiormesenteric artery)

• -left colic artery (branch of inferior mesenteric artery)

Left colicartery

e ns

• Veins correspond to arteries& drain into superior andinferior mesenteric veins




Descending colon

Arteries

• Left colic & sigmoidbranches of inferiormesenteric artery

VeinsLeft colic

escen ngcolon

•

& drain into inferiormesenteric vein

ar ery

Sigmoidarteries




Sigmoid colon

Arteries

• Sigmoid branches of inferiormesenteric arter

Veins

• Tributaries of inferior,

portal venous system Sigmoidarteries

Sigmoid colon




Rectum

Arteries

• Superior rectal artery (branch

of inferior mesenteric artery)

of internal iliac artery)

• Inferior rectal artery (branch

Veins

• Superior rectal vein drains Superiorrectal artery

into inferior mesenteric vein)• Middle rectal & inferior rectal

veins drains into internal iliac

Middle &inferiorrectal

arteries

Rectum

& internal pudendal veins,respectively





Anal Canal

Arteries

• Upper half is supply by

superior rectal artery (branch

• Lower half is supply byinferior rectal artery (branch

Veins

• Upper half is drained by Superiorrectal artery

super or recta ve n ntoinferior mesenteric vein

• Lower half is drained by

Middlerectal artery

Inferiorrectal artery

inferior rectal vein intointernal pudendal vein

Anal canal

BLOOD VESSELS OF LARGE INTESTINE




Arteries





Veins

Superior mesenteric artery and its branches



Superior mesenteric artery and its branches

(supply the midgutderivatives)

uper or mesen er c ar ery

Inferior mesenteric artery and its branches



Inferior mesenteric artery and its branches

Inferior mesenteric artery

(supply the hindgut

Anatomy of Digestive Sys Large Intestine

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