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 Beginnings of 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 protein 2. _________________________________________________________________ – 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 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