1. Digestive System- Continued

2. Absorption in Small Intestine
All food,80% electrolytes and most water absorbed in small intestine
Absorption of glucose:Secondary active transport- absorbed into capillaries
Absorption of Amino acids:Secondary active transport- absorbed into capillaries
Absorption of fatty acids:Movement from lumen to intestinal wall by bile salts.
Once they cross the intestinal wall they are absorbed into lymphatic ducts.

3. Large Intestine Regions: Caecum Appendix Ascending Colon
Transverse Colon
Descending Colon
Rectum
Anal Canal

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Figure 23.29a Gross anatomy of the large intestine.
Left colic
(splenic) flexure
Transverse
mesocolon
Right colic
(hepatic) flexure
Epiploic
appendages
Transverse colon
Superior
mesenteric artery
Descending colon
Haustrum
Ascending colon
IIeum
Cut edge of
mesentery
IIeocecal valve
Tenia coli
Sigmoid colon
Cecum
Appendix
Rectum
Anal canal
External anal sphincter
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Colon
Retroperitoneal except for transverse and sigmoid regions
Ascending colon (right side – to level of right kidney)  right colic (hepatic) flexure 
Transverse colon  left colic (splenic) flexure 
Descending colon (left side) 
Sigmoid colon in pelvis  rectum
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Bacterial Flora
Enter from small intestine or anus
Colonize colon
Synthesize B complex vitamins and vitamin K
Ferment indigestible carbohydrates
Release irritating acids and gases (~500 ml/day)
Bacteria are prevented from breaching the mucosal barrier by antibodies present on the gut wall.
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7. Digestive Processes in the Large Intestine
Residue remains in large intestine 12–24 hours
No food breakdown except by enteric bacteria
Vitamins (made by bacterial flora), water, and electrolytes (especially Na+ and Cl–) reclaimed
Major functions - propulsion of feces to anus; defecation
Colon not essential for life
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8. Motility of the Large Intestine
Most contractions of colon
Haustral contractions
Slow segmenting movements
Haustra sequentially contract in response to distension
Gastrocolic reflex-Initiated by presence of food in stomach
Irritable Bowel Disorder:Recurring abdominal pain, stool changes,flatulence,nausea, depression. Functional bowel disorder.
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Rectum and Anus
Rectum
Three rectal valves stop feces from being passed with gas (flatus)
Anal canal
Last segment of large intestine
Opens to body exterior at anus
Sphincters
Internal anal sphincter—smooth muscle
External anal sphincter—skeletal muscle
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Defecation
Mass movements force feces toward rectum
Distension initiates spinal defecation reflex
Parasympathetic signals
Stimulate contraction of sigmoid colon and rectum
Relax internal anal sphincter
Conscious control allows relaxation of external anal sphincter
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11. Thank you