1. Hepatocytes’ functions include:
Liver Functions:
Hepatocytes’ functions include:
Production of bile (not an enzyme):
Emulsification of fat
Facilitates fat & cholesterol absorption
Processing bloodborne nutrients :
Glucose to glycogen
Amino acids to plasma proteins
Storage of fat-soluble vitamins
Detoxification:
Convert ammonia to urea

2. Yellow-green, alkaline solution Contains:
Composition of Bile
Yellow-green, alkaline solution
Contains:
Bile salts (emulsification agents)
Bile pigments
Cholesterol
Phospholipids
Other substances

3. Pancreas Location Lies deep to the greater curvature of the stomach
Three regions: Head, body and tail
The head: Encircled by the duodenum
Body: Between head & tail
Tail: Close to the spleen

4. Pancreas Exocrine function Endocrine function
Production of enzyme-rich pancreatic juice:
Contains enzymes for breakdown of all classes of food
Acini (clusters of secretory cells):
Contain zymogen granules with digestive enzymes
Endocrine function
Production of hormones:
Glucagon (Alpha cells)
Insulin (Beta cells)
Other hormones ex. somatostatin, pancreatic Polypeptide “pp”

5. Acinus of the Pancreas
Figure 23.26a

6. Pancreatic Juice Composition & Function
Exocrine product of pancreas & consists mainly of:
Water
Electrolytes (mainly HCO3–):
Released by epithelial cells of smallest pancreatic ducts
Neutralizes acid chyme
Provides optimal environment for pancreatic enzymes
Enzymes:
Produced by the acinar cells in active & inactive forms
Proteases are produced in an inactive form
Activation takes place in the duodenum

7. Composition and Function of Pancreatic Juice
Active pancreatic enzymes:
Produced in the active form
Require ions or bile for optimal activity
Include:
Amylase:
Breakdown of starch (carbohydrates)
Lipases:
Breakdown of fat (lipids)
Nucleases:
Breakdown of nucleic acids

8. Composition and Function of Pancreatic Juice
Inactive enzymes (proteases):
Trypsinogen:
Activated to trypsin by dudenal enteropeptidase
Enteropeptidase is a brush boarder protease
Trypsin activates more trypsinogrn (+feedback)
Chymotrypsinogen:
Activated to chymotrypsin by trypsin
Procarboxypeptidase :
Activated to carboxypeptidase by trypsin

9. Pancreatic Enzyme Activation:
Figure 23.27

10. Digestion in the Small Intestine
As chyme enters the duodenum:
Only carbohydrates & proteins were partially digested
No fat digestion has taken place
Chyme (hypertonic & hi H+) is slowly released into duodenum
Mixing is required for proper digestion
The liver & the pancreas supply required digestive substances (name them?)
Virtually all nutrient absorption occurs in the small intestine

11. Motility in the Small Intestine
Most common motion of the small intestine:
Segmentation:
Initiated by intrinsic pacemaker cells
Forward and backward (mixing) movement of food
Moves contents steadily toward the ileocecal valve
Following nutrient absorption:
Peristalsis dominates (each wave is distal to the previous)
Unidirectional (distal) movement of food
Meal remnants, (bacteria, mucosal cells, and debris) are moved into the large intestine

12. Has three unique features:
Large Intestine
Has three unique features:
Teniae coli:
Three longitudinal smooth muscle bands
Reduced bands of the longitudinal muscle layer of the muscularis
Haustra:
Pocket-like sacs
Caused by the tone of teniae coli
Epiploic appendages:
Fat-filled pouches of visceral peritoneum

13. Large Intestine Subdivided into: The saclike cecum: Cecum Appendix
Colon
Rectum
Anal canal
The saclike cecum:
Lies below the ileocecal valve
Contains a wormlike (vermiform) appendix

14. Large Intestine
Figure 23.29a

15. Colon Has distinct regions: Ascending colon Hepatic flexure
Transverse colon
Splenic flexure
Descending colon
Sigmoid colon

16. Colon The mesocolons: The sigmoid colon: The anal canal:
Mesentery sheets
Anchor transverse & sigmoid colons to the posterior abdominal wall
The sigmoid colon:
S-shaped part of the colon that joins the rectum
The anal canal:
Last segment of the large intestine
Lies in the perineum (external to abdominopelvic cavity)
Opens to the exterior at the anus

17. Valves & Sphincters of the Rectum & Anus
Three valves of the rectum:
Stop feces from being passed with gas
Two anal sphincters:
Internal: Composed of smooth muscle
External: Composed of skeletal muscle
Sphincters are closed except during defecation

18. Large Intestine: Microscopic Anatomy
Colon mucosa:
Simple columnar epithelium
Has numerous deep crypts lined with goblet cells
Anal canal mucosa:
Stratified squamous epithelium
Anal columns:
Hanging long ridges or folds of mucosa

19. Large Intestine: Microscopic Anatomy (cont’d)
Anal sinuses:
Recesses between anal columns
Exude mucus
Compress feces
Two superficial venous plexuses associated with anal canal:
One is associated with anal column
The other is associated with the anus itself
Inflammation of these veins causes hemorrhoids (itchy varicosities)

20. Structure of the Anal Canal
Figure 23.29b

21. Two sources of large intestine bacterial flora:
Surviving flora entering the cecum from the S.I.
Flora entering via the anus
These bacteria:
Colonize the colon
Ferment indigestible carbohydrates
Release irritating acids and gases (flatus)
Synthesize vitamins:
B complex vitamins
Vitamin K

22. Functions of the Large Intestine
Propulsion of fecal material toward the anus (major function)
Reabsorption of Vitamins, water, and electrolytes
Except for enteric bacterial digestion, no further digestion takes place in large intestine
Though essential for comfort, the colon is not essential for life

23. Chemical Digestion: Carbohydrates
Forms of carbohydrates in food:
Monosaccharides :
Glucose
Galactose
Fructose
Disaccharides:
Sucrose (table sugar)
Maltose (grain sugar)
Lactose (milk sugar)
Polysaccharides :
Starch (main), glycogen, & cellulose (indigestible)

24. Chemical Digestion: Carbohydrates
Enzymes used:
Salivary amylase (mouth):
Hydrolyze starch & glycogen to oligosaccharides (2-8 chain)
Pancreatic amylase (small intestine):
Hydrolyze escaped carbs. to oligosaccharides (mostly maltose)
Brush border enzymes:
Dextrinase, glucoamylase:
Hydrolyze oligosaccharides (> 3 sugars) to monosach.
Maltase, sucrase and lactase:
Hydrolyze disaccharides (maltose, sucrose, &lactose) to their respective monosaccharides

25. Chemical Digestion: Carbohydrates
Absorption glucose & galactose:
Into epithelial cell :
By 2ndary active transport (co-transport with Na+), &
Carrier proteins
Out of epithelial cell:
By facilitated diffusion
Into capillary bed via intercellular clefts
To the liver (for metabolic processing):
Via the hepatic portal vein (hepatci portal circulation)
Absorption of fructose:
Entirely by facilitated diffusion

26. Chemical Digestion: Proteins
Enzymes used in Stomach:
Pepsin
Enzymes acting in the small intestine:
Pancreatic enzymes:
Trypsin, chymotrypsin, and carboxypeptidases
Brush border enzymes:
Aminopeptidases, dipeptidases, and carboxypeptidases
Absorption:
Similar to carbohydrates :
Active co-transport with Na+ via carrier proteins
H+ dependant co-transport ( dipeptides & tripeptides)
Resulting amino acids enter capillary blood by diffusion

27. Figure 23.34

28. Chemical Digestion: Fats
Enzymes & chemicals used:
Pancreatic lipases:
Produce H2O-insolubale free fatty acids & monoglycerides
Bile salts:
Combine with lipases end products forming micelles
Absorption:
Micelles come in contact with luminal cell surface
Content crosses cell membrane (simple diffusion)
Inside intestinal cells:
Triglycerides are re-synthesized
Combined with cholesterol & phospholipids
All coated with protein forming the chylomicrons

29. Chemical Digestion: Fats
Absorption (cont’d):
Chylomicrons (soluble lipoprotein):
Enter lacteals
Transported in lymphatic stream
Emptied into the venous blood via the thoracic duct
Glycerol & short chain fatty acids are:
Absorbed into the capillary blood of the villi
Transported via the hepatic portal vein

30. Chemical Digestion: Fats
Figure 23.35

31. Fatty Acid Absorption Figure 23.36 Fatty acids and Lumen of
monoglycerides
associated with
micelles in
lumen of intestine
Lumen of
intestine
Absorptive
epithelial cell
cytoplasm ER
Golgi
apparatus
Lacteal
Figure 23.36

32. Fatty Acid Absorption Figure 23.36 Fatty acids and Lumen of
monoglycerides
associated with
micelles in
lumen of intestine
Lumen of
intestine 1
Fatty acids and
monoglycerides
resulting from fat
digestion leave
micelles and enter
epithelial cell by
diffusion.
Absorptive
epithelial cell
cytoplasm ER
Golgi
apparatus
Lacteal
Figure 23.36

33. Fatty Acid Absorption Figure 23.36 Fatty acids and monoglycerides
associated with
micelles in
lumen of intestine
Lumen of
intestine 1
Fatty acids and
monoglycerides
resulting from fat
digestion leave
micelles and enter
epithelial cell by
diffusion.
Absorptive
epithelial cell
cytoplasm 2
Fatty acids are
used to synthesize
triglycerides in
smooth endo-
plasmic reticulum. ER
Golgi
apparatus
Lacteal
Figure 23.36

34. Fatty Acid Absorption Figure 23.36 Fatty acids and monoglycerides
associated with
micelles in
lumen of intestine
Lumen of
intestine 1
Fatty acids and
monoglycerides
resulting from fat
digestion leave
micelles and enter
epithelial cell by
diffusion.
Absorptive
epithelial cell
cytoplasm 2
Fatty acids are
used to synthesize
triglycerides in
smooth endo-
plasmic reticulum. ER
Golgi
apparatus 3
Fatty globules are
combined with
proteins to form
chylomicrons
(within Golgi
apparatus).
Lacteal
Figure 23.36

35. Fatty Acid Absorption Figure 23.36 Fatty acids and monoglycerides
associated with
micelles in
lumen of intestine
Lumen of
intestine 1
Fatty acids and
monoglycerides
resulting from fat
digestion leave
micelles and enter
epithelial cell by
diffusion.
Absorptive
epithelial cell
cytoplasm 2
Fatty acids are
used to synthesize
triglycerides in
smooth endo-
plasmic reticulum. ER
Golgi
apparatus 3
Fatty globules are
combined with
proteins to form
chylomicrons
(within Golgi
apparatus). 4
Vesicles containing
chylomicrons
migrate to the
basal membrane,
are extruded from
the epithelial cell,
and enter a lacteal
(lymphatic capillary).
Chylomicron
Lacteal
Figure 23.36

36. Fatty Acid Absorption Figure 23.36 Fatty acids and monoglycerides
associated with
micelles in
lumen of intestine
Lumen of
intestine 1
Fatty acids and
monoglycerides
resulting from fat
digestion leave
micelles and enter
epithelial cell by
diffusion.
Absorptive
epithelial cell
cytoplasm 2
Fatty acids are
used to synthesize
triglycerides in
smooth endo-
plasmic reticulum. ER
Golgi
apparatus 3
Fatty globules are
combined with
proteins to form
chylomicrons
(within Golgi
apparatus). 4
Vesicles containing
chylomicrons
migrate to the
basal membrane,
are extruded from
the epithelial cell,
and enter a lacteal
(lymphatic capillary). 5
Lymph in the
lacteal transports
chylomicrons away
from intestine.
Chylomicron
Lacteal
Figure 23.36