© UWCM/SONMS/nutrition/MJohn Absorption of every day foods

© UWCM/SONMS/nutrition/MJohn Key Functions: Absorption- P assage of digested nutrients/fluid across the GI wall - to blood/lymph-

© UWCM/SONMS/nutrition/MJohn What does saliva do to food Most sublingual substances are absorbed by simple diffusion Particles have to very small

Absorption Requirements Small particles of food (resulting from mechanical, enzymatic and chemical breakdown in water) Foods broken down into their smallest units (digestion) a. Proteins have been broken down to amino acids b. CHO has been broken down to monosaccharides c. Fats have been broken down to fatty acids and glycerol

© UWCM/SONMS/nutrition/MJohn Digestion of Beans & Toast Carbohydrates = no action Proteins - to peptides Fat – party broken into triglycerides & fatty acids Churning turns beans on toast into chyme

© UWCM/SONMS/nutrition/MJohn Layers of the Small Bowel

© UWCM/SONMS/nutrition/MJohn Cells of the mucosal epithelium Absorption cells: These form the brush border which also contains several enzymes. –Intestinal Lipase works on lipids –Sucrase act on sucrose –Lactase works on Lactose from the from butter –Maltase work on maltose from bread The Brush Border Think about the role of fibre

© UWCM/SONMS/nutrition/MJohn Enlarged Villus of Small Bowel Brush Border cell

© UWCM/SONMS/nutrition/MJohn The fate of foods Proteins Polypeptides Tri-peptides Di-peptides Amino acidsFat Glycerol and fatty acids Small and long chain fatty acidsSmall and long chain fatty acids Carbohydrates Polysaccharides Disaccharides Sucrose  Maltose  Lactose Monosaccharides  Glucose  Fructose  Galactose

© UWCM/SONMS/nutrition/MJohn “Brush Border" & fat absorption 1,000 microvilli per cell Micelle = aggregations of free fatty acids, mono-glycerides in the middle bile salts at polar ends enables solution in water. Micelles 'shuttle’ fatty acids & glycerol to the brush border where they can be absorbed into the enterocyte

© UWCM/SONMS/nutrition/MJohn Diffusion Process (Micelle) Butter fat? Vegetable fat? in chyme Now Chyme Think about the role of fibre

© UWCM/SONMS/nutrition/MJohn Absorption of Nutrients via Small bowel

© UWCM/SONMS/nutrition/MJohn Active transport mechanism with NA + or H + Vegetable protein Beans Chyme

© UWCM/SONMS/nutrition/MJohn Energy production from food With Oxygen Carbohydrate to Glucose molecule 2 Pyruvate molecules 4 Acetyl CoA Molecules Without Oxygen Carbohydrate to Glucose molecule 2 Pyruvate molecules Lactate 16 times MORE energy 16 times LESS energy

© UWCM/SONMS/nutrition/MJohn Absorbing food Insulin = promotes anabolism Plasma insulin increases. –Glucose goes into cells. –Stimulates glycogen storage (liver and muscle). –Stimulates fat storage in adipose cells. –Promotes cellular uptake of amino acids and synthesis of proteins.

© UWCM/SONMS/nutrition/MJohn After Absorption Maintaining plasma glucose concentration. Plasma Glucagon increases: –Stimulates glycogenolysis in the liver –Stimulates gluconeogenesis (glucose from fat & protein). –Skeletal muscle, heart, liver and kidneys use fatty acids as major source of fuel.

© UWCM/SONMS/nutrition/MJohn Glucocorticoids Support the effect of increased Glucagon. Promote lipolysis and ketogenesis. Promote protein breakdown in muscles. Promote liver gluconeogenesis.

© UWCM/SONMS/nutrition/MJohn protein, carbohydrate, fat, calorie requirements General Calculation: BMR = your body weight in lbs x 10 kcal/lb E.g. You weigh 150 lbs BMR = 150 x 10 kcal/lb = 1,500 kcals Then you add exercise requirement

© UWCM/SONMS/nutrition/MJohn A person's specific needs vary depending on the duration and intensity of one's activity fitness level. Leptin signal to Hypothalamus Regulates fat deposits ‘yo yo’ dieting

© UWCM/SONMS/nutrition/MJohn Key Functions: Elimination Expulsion of undigested and unabsorbed residues from the gut

© UWCM/SONMS/nutrition/MJohn Colon Function Functions –Absorb electrolytes and water –Store fecal material until evacuation Normal colonic transit –12-30 hours Types of movement –Haustrations Circular contractions Do not propel contents –Mass movements Propels contents

© UWCM/SONMS/nutrition/MJohn Bowel - Autonomic Nervous System Parasympathetics –Increases colonic motility Sympathetics –Promote storage Enhance anal tone Inhibit colonic contractions Bilateral sympathectomy has little clinical effect

© UWCM/SONMS/nutrition/MJohn Bowel – Autonomic Nervous System Parasympathetic nervous system –PNS functions Increase peristalsis Stimulates secretions Relaxes sphincters Increases gut motility

© UWCM/SONMS/nutrition/MJohn Sympathetic Control Norepinephrine Functions –Decrease peristalsis –Inhibits secretions –Contracts sphincters –Decreases gut motility

Large Intestines Mass movement Increased Bacterial colonisation (help synthesis of Vit K and Folic Acid) Absorption of fluid occurs here Bacteria ferment contents of bowel - Flatus Mineral Salts, vitamins, some drugs all absorbed here Gets ready to push waste out (FAECES)

© UWCM/SONMS/nutrition/MJohn Large Intestine Digestion & Absorption Bacterial fermentation: Vit. K, lactate Water and electrolyte secretion &/or absorption

© UWCM/SONMS/nutrition/MJohn Large Intestine Digestion & Absorption

© UWCM/SONMS/nutrition/MJohn Large Intestine, H 2 O Absorption & Defaecation Figure 21-27: Anatomy of the large intestine

© UWCM/SONMS/nutrition/MJohn (Small intestine reabsorbs  7.5 L/day of H 2 0) Large Intestine reabsorbs  1.4 L/day Large Intestine, H 2 O Absorption & Defaecation

© UWCM/SONMS/nutrition/MJohn Normal Defaecation Volitional control of levator ani –Opens proximal anal canal –Relaxes external sphincter and puborectalis –Allows straighter anorectal passage May increase with –Valsalva –Increasing intraabdominal pressure (squat)

© UWCM/SONMS/nutrition/MJohn Normal Defaecation Defecation deferred by volitionally contracting –Puborectalis –External anal sphincter –Then, internal anal sphincter relaxation reflex will fade (within approx 15 sec) and urge will resolve until triggered again

© UWCM/SONMS/nutrition/MJohn Defaecation Reflex mass movement  rectal distension  internal sphincter (invol)  external sphincter (vol)