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