The Human Body: From Food to Fuel
BIOL 103, Chapter 4(Part 1)
Today’s Topics
• Taste and Smell• GI Tract• Digestion and Absorption• Assisting Organs• Circulation of Nutrients
Taste and Smell: The Beginningsof our Food Experience
• Sight, smell, thought, taste, and sound– Can trigger a set of responses that prepare the
digestive tract to receive food
The Gastrointestinal (GI) Tract
• Organization– ____________________
• mouth, esophagus, stomach, small intestine, large intestine, rectum
– ____________________• Salivary glands, liver,
gallbladder, and pancreas
Organization of the GI Tract
• Functions:– __________________(the receipt and softening of
food)– __________________ of ingested food– __________________ of digestive enzymes, acid,
mucus, and bile– __________________ of end products of digestion– __________________ of undigested material– __________________ of waste material
Organization of the GI Tract
• Structural organization of the GI tract– ____________________
(innermost layer)• Glands and absorptive cells
– __________________________________________
• Mix and move the food
– _____________________:valve that controls the movement of food material so that it travels through the GI tract in only one direction.
Overview of Digestion
• Mouth– Chewing _______________________________– Saliva _________________________________
• Down the GI tract:– Physical movement• __________________________: waves of muscular
contraction that helps push food down the GI tract• __________________________: a periodic muscle
contractions in the small intestine that move the content forward and backward,
Overview of Digestion
•Chemical breakdown: – __________________________ (a mass of partially
digested food + digestive juices moving from stomach into small intestine)• _______________________: are proteins that catalyze
(speed up) reactions but are not altered in the process.– Examples: amylase, lipase, etc.
• Other secretions:
Overview of Digestion
Overview of Absorption
• 3 Main processes allow nutrients to be absorbed from GI tract blood/circulation– _____________________: movement of molecules
through cell membrane from ________________________________________________________________– _____________________: movement of molecules
through cell membrane from ________________________________________________________________– _____________________: movement of molecules
through cell membrane ______________________________________________________________________
Overview of Absorption
Assisting Organs• Salivary glands
– ______________________________– Supply enzymes
• Liver– _______________________________________– “Detox center:” _________________________– “Chemical factory”: ______________________
• Produce blood proteins, cholesterol, sugar
– ____________________: stores hormones, cholesterol, minerals, sugar, etc.• Gallbladder
– ____________________________________– Bile’s Enterohepatic circulation:
• ________________________________________________________________________________
• Pancreas– ____________________________________– Secretes hormones _________________________
Putting It All Together: Digestion and Absorption
• Mouth– Enzymes
• ____________________________________• ____________________________________
– Saliva• Moistens food for swallowing forms into bolus
• Esophagus– Transports food to stomach– ___________________________________________
• “Heartburn”
Putting It All Together:Digestion and Absorption
• Stomach Enzymes:– Hydrochloric acid/gastric acid
1. ________________________2. ________________________
1. breaks down 3D structure of protein2. _________________________________________________________________
– Pepsin: _____________________________________– Gastric lipase: some fat digestion– Gastrin (hormone) stimulates gastric secretion and
movement– Intrinsic factor _______________________________
Putting It All Together:Digestion and Absorption
• Small intestine (~10ft)– _____________________– Sections of small intestine:
• _____________________• _____________________• _____________________
– Nutrient digestion• Bicarbonate __________________________________• Pancreatic and intestinal
enzymes– ___________________– ___________________– ___________________
• Vitamins, minerals, cholesterol are not digested and generally absorbed unchanged.
Putting It All Together:Digestion and Absorption
• Small intestine– Completes absorption:
• ____________________________________________________________________
– 600x fold increase/tennis court!• Most nutrients absorbed here• Fat-soluble nutrients _________________________________________________• Water-soluble nutrients ___________
Putting It All Together:Digestion and Absorption
• Large Intestine– Ileocecal valve– Sections
• _____________________• _____________________• _____________________• _____________________
– Digestion• Peristaltic movement is
slow, taking 18-24 hours for material to travel
• Some bacterial activity Example: _____________________
Beans, Beans, Beans!
• Beans are made up of oligosaccharides (e.g. raffinose and stachyose), a component of fiber.
• They are ignored until they are met by 700+ species of bacteria in your large intestine.– _________________________
_____________________ _________________
Putting It All Together:Digestion and Absorption
• Large Intestine:– Absorption
• ___________________• ___________________• ___________________
– _____________ at anal sphincter• Feces: 60% solid (bacteria,
dietary fiber, digestive secretions), 40% water
Circulation of Nutrients
• Vascular system: veins and arteries– ____________________________________________________________________________________________________________– Removes wastes
• ____________________• ____________________
Circulation of Nutrients
• Lymphatic system: vessels that drain lymph (clear fluid formed in the spaces between cells) 1. Fat soluble-vitamins are absorbed into lymph
vessels in the intestine.2. _________________________________________________________________________________– Clean-up: proteins and large particulate matter in
tissue spaces lymphatic system removed
Circulation of Nutrients
• Excretion and Elimination– Lungs• Excrete __________________________________
– _________________________________________• Excrete digestive wastes
– Urine: urea + salts + water
• Maintain water and ion balance
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