Week 1: Digestive system
Mass flow of nutrients
Nutritional input Physiological output Metabolism
Total daily intake (kJ) Physiological status Δ Metabolic pathways
Meal size, pattern Health status Δ Energetic efficiencies
Nutrient composition Environment ➢ Δ Body composition
- Waste products
Nutritional physiology = metabolism balances
nutritional input and physiological output
➢ macronutrients
○ movement through body
○ regulation of movement
○ physiology benefits
○ leaves the body
➢ fate of food after eating
○ digestion/absorption
○ storage
○ utilisation
Digestion
Why no self-digestion?
➢ Activity restricted to presence of food
➢ Regulation (local, distal, proximal)
➢ Enzymes stored as inactive proenzymes (zymogens)
➢ Non-digestible mucus coats the walls
➢ High replacement rate (turnover) of mucosal cells
Intermediary metabolism
➢ Interconversion of monomers
(e.g. glucose to AA)
➢ anabolic reactions
➢ catabolic reaction
, PP = post prandial = after eating PA = post absorption
- digestion - utilisation
- absorption
- Storage (Protein > Fats or CHO)
ME = metabolisable energy
5-20% of ME is directly released as heat
Diet‐induced Thermogenesis (DIT)
Effects depend on ingested nutrients:
proteins > carbohydrates > fat
INPUT > NEEDS → ANABOLIC or
INPUT < NEEDS → MOBILIZATION
CATABOLIC DISPOSAL
(Turnover, interconversion, oxidation)
(Storage, interconversion, oxidation)
Homeostasis
= ability of an organism to counteract (within limits of the metabolic scope) factor that disturb
vital functions
- glucose concentration in blood
- pH in the blood (acid/base balance)
- oxygen supply (cardiac output, respiration)
- body temperature (thermoregulation)
Mass flow of nutrients
Nutritional input Physiological output Metabolism
Total daily intake (kJ) Physiological status Δ Metabolic pathways
Meal size, pattern Health status Δ Energetic efficiencies
Nutrient composition Environment ➢ Δ Body composition
- Waste products
Nutritional physiology = metabolism balances
nutritional input and physiological output
➢ macronutrients
○ movement through body
○ regulation of movement
○ physiology benefits
○ leaves the body
➢ fate of food after eating
○ digestion/absorption
○ storage
○ utilisation
Digestion
Why no self-digestion?
➢ Activity restricted to presence of food
➢ Regulation (local, distal, proximal)
➢ Enzymes stored as inactive proenzymes (zymogens)
➢ Non-digestible mucus coats the walls
➢ High replacement rate (turnover) of mucosal cells
Intermediary metabolism
➢ Interconversion of monomers
(e.g. glucose to AA)
➢ anabolic reactions
➢ catabolic reaction
, PP = post prandial = after eating PA = post absorption
- digestion - utilisation
- absorption
- Storage (Protein > Fats or CHO)
ME = metabolisable energy
5-20% of ME is directly released as heat
Diet‐induced Thermogenesis (DIT)
Effects depend on ingested nutrients:
proteins > carbohydrates > fat
INPUT > NEEDS → ANABOLIC or
INPUT < NEEDS → MOBILIZATION
CATABOLIC DISPOSAL
(Turnover, interconversion, oxidation)
(Storage, interconversion, oxidation)
Homeostasis
= ability of an organism to counteract (within limits of the metabolic scope) factor that disturb
vital functions
- glucose concentration in blood
- pH in the blood (acid/base balance)
- oxygen supply (cardiac output, respiration)
- body temperature (thermoregulation)
