Organs of the GI tract
Accessory
digestive organs
Oral cavity,
pharynx,
esophagus
Chewing,
peristalsis
Stomach
Protein digestion
Carbohydrate digestion
Nucleic acid digestion
Polysaccharides Disaccharides
(starch, glycogen) (sucrose, lactose)
Salivary amylase
Smaller polysaccharides,
maltose
Proteins
Pepsin
Churning,
mixing
Small polypeptides
Lumen of
small intestine
Polysaccharides
Peristalsis,
mixing
Maltose and other
disaccharides
Pancreatic amylases
Polypeptides
Pancreatic trypsin and
chymotrypsin
(These proteases cleave bonds adjacent to
certain amino acids.)
Smaller
polypeptides
DNA, RNA
Pancreatic
nucleases
Nucleotides
Disaccharidases
(These proteases split off one amino acid at a time,
working from opposite ends of a polypeptide.)
Monosaccharides
Large
intestine
Dipeptidases, carboxypeptidase,
and aminopeptidase
Amino acids
(Insoluble in
water, fats aggregate as
globules.)
Bile salts
(A coating of
bile salts prevents small droplets from coalescing into
larger globules, increasing
exposure to lipase.)
Pancreatic lipase
Amino acids
Small peptides
Fat globules
Fat droplets
Pancreatic carboxypeptidase
Epithelium
of small
intestine
(brush
border)
Fat digestion
Glycerol, fatty
acids, glycerides
Nucleotidases
Nucleosides
Nucleosidases
and
phosphatases
Nitrogenous bases,
sugars, phosphates
Resident bacteria in the colon digest material in chyme.
Vitamin-K and some B-complex vitamins are released by these bacteria.
Composition of the adult human body
Oral cavity,
pharynx,
esophagus
Chewing,
peristalsis
Stomach
Protein digestion
Carbohydrate digestion
Nucleic acid digestion
Polysaccharides Disaccharides
(starch, glycogen) (sucrose, lactose)
Salivary amylase
Smaller polysaccharides,
maltose
Proteins
Pepsin
Churning,
mixing
Small polypeptides
Lumen of
small intestine
Polysaccharides
Peristalsis,
mixing
Maltose and other
disaccharides
Pancreatic amylases
Polypeptides
Pancreatic trypsin and
chymotrypsin
(These proteases cleave bonds adjacent to
certain amino acids.)
Smaller
polypeptides
DNA, RNA
Pancreatic
nucleases
Nucleotides
Disaccharidases
(These proteases split off one amino acid at a time,
working from opposite ends of a polypeptide.)
Monosaccharides
Large
intestine
Dipeptidases, carboxypeptidase,
and aminopeptidase
Amino acids
(Insoluble in
water, fats aggregate as
globules.)
Bile salts
(A coating of
bile salts prevents small droplets from coalescing into
larger globules, increasing
exposure to lipase.)
Pancreatic lipase
Amino acids
Small peptides
Fat globules
Fat droplets
Pancreatic carboxypeptidase
Epithelium
of small
intestine
(brush
border)
Fat digestion
Glycerol, fatty
acids, glycerides
Nucleotidases
Nucleosides
Nucleosidases
and
phosphatases
Nitrogenous bases,
sugars, phosphates
Resident bacteria in the colon digest material in chyme.
Vitamin-K and some B-complex vitamins are released by these bacteria.
Salivary glands
◦ Produce saliva
 Mostly water
 Some enzymes
 Salivary amylase
 Lysozyme
 Mucus or mucin

Teeth
◦ Mechanical digestion
◦ Different teeth
 Different functions
 Fit omnivore diet

Tongue
Swallowing:
from mouth to stomach
Oral cavity,
pharynx,
esophagus
Chewing,
peristalsis
Stomach
Protein digestion
Carbohydrate digestion
Nucleic acid digestion
Polysaccharides Disaccharides
(starch, glycogen) (sucrose, lactose)
Salivary amylase
Smaller polysaccharides,
maltose
Proteins
Pepsin
Churning,
mixing
Small polypeptides
Lumen of
small intestine
Polysaccharides
Peristalsis,
mixing
Maltose and other
disaccharides
Pancreatic amylases
Polypeptides
Pancreatic trypsin and
chymotrypsin
(These proteases cleave bonds adjacent to
certain amino acids.)
Smaller
polypeptides
DNA, RNA
Pancreatic
nucleases
Nucleotides
Disaccharidases
(These proteases split off one amino acid at a time,
working from opposite ends of a polypeptide.)
Monosaccharides
Large
intestine
Dipeptidases, carboxypeptidase,
and aminopeptidase
Amino acids
(Insoluble in
water, fats aggregate as
globules.)
Bile salts
(A coating of
bile salts prevents small droplets from coalescing into
larger globules, increasing
exposure to lipase.)
Pancreatic lipase
Amino acids
Small peptides
Fat globules
Fat droplets
Pancreatic carboxypeptidase
Epithelium
of small
intestine
(brush
border)
Fat digestion
Glycerol, fatty
acids, glycerides
Nucleotidases
Nucleosides
Nucleosidases
and
phosphatases
Nitrogenous bases,
sugars, phosphates
Resident bacteria in the colon digest material in chyme.
Vitamin-K and some B-complex vitamins are released by these bacteria.

Muscular sac

Gastric glands
◦ Churns & mixes food
◦ Parietal cells  HCl,
intrinsic factor
◦ Goblet cells  mucus
◦ Chief cells 
pepsinogen, weak
gastric lipase
◦ Gastrin
 Hormone
 Controls gastric juices

Comes out as chyme
(2-6 hours)
Esophagus
Cardiac orifice
5 µm
Pyloric
sphincter
Interior surface of
stomach.
- Highly folded
- Dotted with pits
Gastric gland.
-Secrete gastric juice
-Three types of cells
Stomach
Small
intestine
Folds of
epithelial
tissue
Epithelium
3
Pepsinogen
2
HCl
1
Pepsinogen and
HCI secreted
into lumen
2
HCl converts
pepsinogen to
pepsin
Pepsin (active enzyme)
1
Mucus cells
3
Chief cells
- Pepsinogen
Parietal cells
- Secrete HCl
Chief cell
Parietal cell
Pepsin activates
more pepsinogen
Liver
 Secretes bile
(stored in gall bladder)
 Components: Bile
salts & bile pigments
 Emulsifies fats
Gallbladder
 Stores, concentrates,
and releases bile into
duodenum
 Cystic duct + hepatic
duct = common bile
duct
 Stimulated by the
hormone
cholecystokinin (CCK)


Exocrine function
Acinar cells secrete
pancreatic juice
◦
◦
◦
◦
◦
◦
◦

Amylase
Lipase
Trypsin
Chymotrypsin
Carboxypeptidase
Nuclease
NaHCO3-
Secretin and
cholecystokinin (CCK)
fr intestinal wall
stimulates PJ
production
Oral cavity,
pharynx,
esophagus
Chewing,
peristalsis
Stomach
Protein digestion
Carbohydrate digestion
Nucleic acid digestion
Polysaccharides Disaccharides
(starch, glycogen) (sucrose, lactose)
Salivary amylase
Smaller polysaccharides,
maltose
Proteins
Pepsin
Churning,
mixing
Small polypeptides
Lumen of
small intestine
Polysaccharides
Peristalsis,
mixing
Maltose and other
disaccharides
Pancreatic amylases
Polypeptides
Pancreatic trypsin and
chymotrypsin
(These proteases cleave bonds adjacent to
certain amino acids.)
Smaller
polypeptides
DNA, RNA
Pancreatic
nucleases
Nucleotides
Large
intestine
Dipeptidases, carboxypeptidase,
and aminopeptidase
(These proteases split off one amino acid at a time,
working from opposite ends of a polypeptide.)
Amino acids
Bile salts
(A coating of
bile salts prevents small droplets from coalescing into
larger globules, increasing
exposure to lipase.)
Glycerol, fatty
acids, glycerides
Small peptides
Monosaccharides
(Insoluble in
water, fats aggregate as
globules.)
Pancreatic lipase
Amino acids
Disaccharidases
Fat globules
Fat droplets
Pancreatic carboxypeptidase
Epithelium
of small
intestine
(brush
border)
Fat digestion
Enteropeptidase
Nucleotidases
Nucleosides
Nucleosidases
and
phosphatases
Nitrogenous bases,
sugars, phosphates
Resident bacteria in the colon digest material in chyme.
Vitamin-K and some B-complex vitamins are released by these bacteria.





Completes digestion
of nutrients in chyme
Absorbs products of
digestion
Receives enzymes
from pancreas and
gall bladder
Lumen, villi, lacteal,
microvilli, intestinal
glands
Watery fluid,
digestive enzymes
on microvilli:
disaccharidase,
dipeptidase,
nucleotidases
25 cm
1-2 m
2m
Bile
Gallbladder
Liver
Stomach
Acid chyme
Intestinal
juice
Pancreatic juice
Pancreas
Duodenum of
small intestine
Oral cavity,
pharynx,
esophagus
Chewing,
peristalsis
Stomach
Protein digestion
Carbohydrate digestion
Nucleic acid digestion
Polysaccharides Disaccharides
(starch, glycogen) (sucrose, lactose)
Salivary amylase
Smaller polysaccharides,
maltose
Proteins
Pepsin
Churning,
mixing
Small polypeptides
Lumen of
small intestine
Polysaccharides
Peristalsis,
mixing
Maltose and other
disaccharides
Pancreatic amylases
Polypeptides
Pancreatic trypsin and
chymotrypsin
(These proteases cleave bonds adjacent to
certain amino acids.)
Smaller
polypeptides
DNA, RNA
Pancreatic
nucleases
Nucleotides
Disaccharidases
(These proteases split off one amino acid at a time,
working from opposite ends of a polypeptide.)
Monosaccharides
Large
intestine
Dipeptidases, carboxypeptidase,
and aminopeptidase
Amino acids
(Insoluble in
water, fats aggregate as
globules.)
Bile salts
(A coating of
bile salts prevents small droplets from coalescing into
larger globules, increasing
exposure to lipase.)
Pancreatic lipase
Amino acids
Small peptides
Fat globules
Fat droplets
Pancreatic carboxypeptidase
Epithelium
of small
intestine
(brush
border)
Fat digestion
Glycerol, fatty
acids, glycerides
Nucleotidases
Nucleosides
Nucleosidases
and
phosphatases
Nitrogenous bases,
sugars, phosphates
Resident bacteria in the colon digest material in chyme.
Vitamin-K and some B-complex vitamins are released by these bacteria.

Areas of Colon

◦ Cecum
◦ Rectum
◦ Terminates at anus


Absorption of
water and
electrolytes
Concentration &
elimination of
solids
Home for
bacteria that
produce biotin,
folic acid, vitamin
K, several Bvitamins, gases
Name
Stomach Gastrin
Source
Pyloric
mucosa
Intestinal Gastrin
Stimulant
Partiallydigested food
Target Organ
Function
Gastric glands
Secretion of gastric juice
Stomach
Secretin
Acidity of
chyme
Pancreas and
Secretion of PJ rich in
liver
HCO3- and bile production
Cholecystokinin
(CCK)
Fats or
combination
of acids and
fats
Pancreas and
gallbladder
Secretion of PJ, bile from
(Sphincter of gallbladder, opening of SO
Oddi in CBD)
Enterocrinin
Enterogastrone or
Gastric Inhibitory
Peptide (GIP)
Intestinal
mucosa
Acidity of
chyme
Fats
Duodenum
Secretion of intestinal
juice
Stomach
Inhibits secretion of
gastric juice and
decreases gastric motility
Liver
Enterogastrone
Gallbladder
Gastrin
CCK
Stomach
Pancreas
Secretin
Duodenum
CCK
Key
Stimulation
Inhibition