Human digestion

Human digestive system (General plan)

Accessory digestive organs

Organ/s Mechanical

digestionCarbohydrate digestion Protein

digestion

Nucleic Acid

digestion

Lipid

digestion

Oral cavity

Esophagus

Chewing

Peristalsis

Polysaccharides(starch, glycogen)

Disaccharides(sucrose, lactose)

Sites of digestion

Esophagus

Pharynx

Peristalsis

Stomach Churning

Mixing

Peristalsis

Small

intestine

Peristalsis

Mixing

Salivary amylaseSalivary amylaseSalivary amylaseSalivary amylase

Smaller polysaccharides,maltose

Polysaccharides

Proteins

PepsinPepsinPepsinPepsin

Small polypeptides

Pancreatic Pancreatic Pancreatic Pancreatic trypsintrypsintrypsintrypsinand and and and chymotrypsinchymotrypsinchymotrypsinchymotrypsin

DNA, RNA

PancreaticPancreaticPancreaticPancreatic

Fat globules

Bile saltsBile saltsBile saltsBile saltsintestine

Lumen

Mixing

Small

intestine

Epithelium

Polysaccharides

Pancreatic Pancreatic Pancreatic Pancreatic amylaseamylaseamylaseamylase

Maltose and other disaccharides

DisaccharidasesDisaccharidasesDisaccharidasesDisaccharidasesDisaccharidasesDisaccharidasesDisaccharidasesDisaccharidases

MonosaccharidesMonosaccharidesMonosaccharidesMonosaccharides

Smaller polypeptides

Small peptides

DipeptidasesDipeptidasesDipeptidasesDipeptidases, , , , carboxypeptidasecarboxypeptidasecarboxypeptidasecarboxypeptidase, , , , aminopeptidaseaminopeptidaseaminopeptidaseaminopeptidase

Amino acidsAmino acidsAmino acidsAmino acids

PancreaticPancreaticPancreaticPancreaticnucleasesnucleasesnucleasesnucleases

Nucleotides

NucleotidasesNucleotidasesNucleotidasesNucleotidases

Nucleosides

NucleosidasesNucleosidasesNucleosidasesNucleosidases, , , , phosphatasesphosphatasesphosphatasesphosphatases

Nitrogenous bases,Nitrogenous bases,Nitrogenous bases,Nitrogenous bases,sugars, phosphatessugars, phosphatessugars, phosphatessugars, phosphates

Bile saltsBile saltsBile saltsBile salts

Fat droplets

Pancreatic lipasePancreatic lipasePancreatic lipasePancreatic lipase

Glycerol, fattyGlycerol, fattyGlycerol, fattyGlycerol, fattyacids, acids, acids, acids, glyceridesglyceridesglyceridesglycerides

Composition of the adult human body

• Salivary glands

– Produce saliva

Digestion in the Mouth

– Produce saliva

• Mostly water

• Some enzymes

– Salivary amylase

– Lysozyme

• Mucus or mucin

• Teeth• Teeth

Swallowing: from mouth to stomach

� Muscular sac◦ Churns & mixes food

� Gastric glands

Digestion in the Stomach

� Gastric glands◦ Parietal cells � HCl,

intrinsic factor

◦ Goblet cells � mucus

◦ Chief cells �pepsinogen, weak gastric lipase

◦ Gastrin◦ Gastrin� Hormone

� Controls gastric juices

� Comes out as chyme(2-6 hours)

Liver� Secretes bile

(stored in gall bladder)

� Emulsifies fats

Gallbladder� Stores, concentrates,

and releases bile into duodenum

� Stimulated by the � Stimulated by the hormone cholecystokinin (CCK)

• Exocrine function

• Acinar cells secrete pancreatic juice

– Amylase

Pancreas

– Amylase

– Lipase

– Trypsin

– Chymotrypsin

– Carboxypeptidase

– Nuclease

– NaHCO3

• Secretin and • Secretin and cholecystokinin (CCK) frintestinal wall stimulates PJ production

Chemical digestion in the duodenum (con’t.)

Absorption in the small intestine

Reabsorption and elimination in the large intestine

• Areas of the colon

• Cecum• Cecum

• Rectum

• Anus

• Absorption of water

and electrolytes

• Concentration &

elimination of solidselimination of solids

• Home for bacteria

that produce biotin,

folic acid, vitamin K,

several B-vitamins,

gases

Hormones coordinate secretion of digestive juices

Name Source Stimulant Target Organ Function

Stomach GastrinPyloric

mucosa Partially-Gastric glands

Secretion of gastric juicemucosa

digested foodSecretion of gastric juice

Intestinal Gastrin

Intestinal

mucosa

Stomach

SecretinAcidity of

chyme

Pancreas and

liver

Secretion of PJ rich in

HCO3- and bile production

Cholecystokinin

(CCK)

Fats or

combination

of acids and

Pancreas and

gallbladder

(Sphincter of

Secretion of PJ, bile from

gallbladder, opening of SOmucosa

fats Oddi in CBD)

EnterocrininAcidity of

chymeDuodenum

Secretion of intestinal

juice

Enterogastrone or

Gastric Inhibitory

Peptide (GIP)

Fats Stomach

Inhibits secretion of

gastric juice and

decreases gastric motility

Liver

Gall-bladder

Entero-gastrone

bladder

CCK

Gastrin

Stomach

Pancreas

SecretinSecretin

CCK

Duodenum

KeyKeyKeyKey

Stimulation

Inhibition