11. LARGE INTESTINE.ppt a brief description

Describes the large intestine in brief detail

1. LARGE INTESTINE

2. General Characteristics of the Large
Intestine
–Teniae coli
•Thickening of longitudinal
muscularis
–Haustra
•Puckering created by teniae coli
–Epiploic appendages
•Fat-filled pouches of visceral
peritoneum

3. General Characteristics of the Large
Intestine Cont……
•Villi are absent
•Contains numerous goblet cells
•Intestinal crypts –simple tubular glands
•Lined with simple columnar epithelial tissue
–Epithelium changes at anal canal
•Becomes stratified squamous epithelium

4. Parts of the Large Intestine
1. cecum including the appendix,
2. colon, and
3. rectum with the anal canal.

5. Cecum & vermiform
appendeix
•Cecum-the first part of the
large intestine, forming a
dilated pouch into which
open the ileum, the colon,
and vermiform appendeix
•Vermiform appendix-a
worm-like diverticulum of
the cecum, ranging from 3-
6 inchesin length, it has no
known digestive role.

6. Colon
•Colon is 90 cm to 150 cm long
•Diameter is 4 to 6 cm
•Extends from the ileocecal
valve to the anus and is
divided into five sections
–The ascending
–Transverse
–Descending
–Sigmoid colon
–Rectum

8. Colon Cont…
•Ascending colon-the portion
of the large intestine between
the cecumand the hepatic
flexure
•Transverse colon-the portion
of the colon that runs
transversely across the upper
part of the abdomen, from the
right to left colic flexureor
splenic flexure

10. Colon Cont….
•Descending colon-left side
of abdomen from the
spleen to the iliac crest
•Sigmoid colon-the S-
shaped part of the colon,
lying in the pelvis,
extending from the pelvic
brim to the third segment
of the sacrum, and
continuous above with the
descending colon and
below the rectum

11. RECTUM
•Rectum-the distal
portion of the colon,
beginning anterior to
the third sacral
vertebraas a
continuation of the
sigmoid and ending
at the anal canal

12. ANAL CANAL
•TheanalcanalisthemostterminalpartofthelowerGI
tract/largeintestine,whichliesbetweentheanorectal
junctionandanalverge.
•Thedemarcationbetweentherectumaboveandthe
analcanalbelowistheanorectalringoranorectal
flexure,wherethepuborectalismuscleformsasling
aroundtheposterioraspectoftheanorectaljunction,
kinkingitanteriorly.
•Theanalcanaliscompletelyextraperitoneal.The
lengthoftheanalcanalisabout4cm(range,3-5cm),
withtwothirdsofthisbeingabovethepectinateline
(alsoknownasthedentateline)andonethirdbelow
thepectinateline.
•Theepitheliumoftheanalcanalbetweentheanal
vergebelowandthepectinatelineaboveisdescribed
asanalmucosaoranalskin.Itissensitivelikeskinand
iskeratinized(butdoesnothaveskinappendages).

13. •The anorectal junction or anorectal ring is situated about 5
cm from the anus. At the anorectal flexure or angle, the
anorectal junction is pulled anterosuperiorly by the puborectal
sling to continue below as the anal canal.

14. BLOOD SUPPLY AND LYMPHATICS
•Theanalcanalabovethepectinatelineissupplied
bytheterminalbranchesofthesuperiorrectal
(hemorrhoidal)artery,whichistheterminalbranchof
theinferiormesentericartery.Themiddlerectal
artery(abranchoftheinternaliliacartery)andthe
inferiorrectalartery(abranchoftheinternal
pudendalartery)supplytheloweranalcanal.
•Beneaththeanalcanalskin(belowthepectinate
line)liestheexternalhemorrhoidalplexusof
veins,whichdrainsintosystemicveins.Beneaththe
analcanalmucosa(abovethepectinateline)liesthe
internalhemorrhoidalplexusofveins,which
drainsintotheportalsystemofveins.Theanalcanal
is,therefore,animportantareaofportosystemic
venousconnection(theotherbeingthe
esophagogastricjunction).Lymphaticsfromtheanal
canaldrainintothesuperficialinguinalgroupof
lymphnodes.

15. MOTILITY
Four basic patterns of movement
-Periodic uncoordinated tonic contractions for segmentation of
both the longitudinal and circular muscles bunch up the fold of
the mucosa, forming the haustra
-Phasic-random, nonpropulsive contractions, peristalsis and
retrograde peristalsis, which mix the stool material and help
absorb its liquid contentswith advancing the material toward
the anus.

16. –Spontaneous mass movement occur three or four times a day
when the colon becomes filled and distended
–Valsalva maneuver, the involuntary movement of the bowel wall
and the relaxation of the external sphincter are assisted by
contraction of the diaphragm and the thoracic and abdominal
muscles

17. FUNCTIONS
•The primary function of the large intestine is the
reabsorption of water and inorganic salts. The only
secretion of any importance is mucus, which acts as a
lubricant during the transport of the intestinal contents.

18. •Secretion
–Colonic secretion is scanty and consists primarily of water,
mucus, potassium and bicarbonate
–The alkaline mucus secreted by goblet cells in the crypts
lubricates the intestinal walls, protects the mucosa from
acidic bacterial action and helps lubricate the passage of
stool

19. •Absorption and elimination
–1000 to 2000 ml of liquid chyme enters the colon daily, only 150
to 250 ml of fluid is evacuated in the stool.
–The colon absorbs sodium, chloride, and water, with the most
absorption being accomplished in the ascending colon.

20. HISTOLOGY
•The wall of the large intestine has four layers
–The serosa
–The muscularis
–The submucosa
–The mucosa
–The outer serous layer if formed by visceral peritoneum, the
rectum does not have a serous layer

21. HISTOLOGY OF THE CECUM AND
APPENDIX

22. HISTOLOGY OF THE COLON

23. HISTOLOGY OF THE RECTUM AND ANAL CANAL

24. BLOOD/NERVE SUPPLY
•First half of large intestine
–Arterial supply -superior mesenteric artery
–Innervation
•Sympathetic innervation –superior mesenteric and celiac ganglia
•Parasympathetic innervation –vagus nerve

25. •Distal half of large intestine
–Arterial supply -inferior mesenteric artery
–Innervation
•Sympathetic innervation –inferior mesenteric and hypogastric plexuses
•Parasympathetic innervation –pelvic splanchnic nerves

26. DEFECATION REFLEX

27. Clinical Correlates
•Colorectal cancer
–is the second most common ca in adults
–Occurs in persons 50 to 80
–Approx 95% intestinal ca are adenocarinomas
–Risk Factors
•Diet high in fat
•Increasing age
•Fm hx
•Previous colon cancer
•Personal hx of adenomatous polyps
•Familial polyposis or gardner sydrome
•UC for more than 7 years
•Genital cancer or breast cancer (in women)

28. •Anorectal fistula
–is a hollow, fibrous tract leading from the anal canal or rectum to the
perianal skin and often results from an anorectal abscess
–Anal Fissure
•Is a thin tear of the superficial anal mucosa
•Commonly occurs along the midline of the posterior anal canal

29. -Rectal Prolapse
Occurs when the rectum mucosa bulges through the anus,