© UWCM/SONMS/nutrition/MJohn
Key Functions: Absorption-• Passage 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
© UWCM/SONMS/nutrition/MJohn
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 acidsb. CHO has been broken down to monosaccharidesc. 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 acidsChurning turns beans
on toast into chyme
© 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 Intestinal Lipase works on lipidslipids
– Sucrase act on sucroseSucrase act on sucrose
– Lactase works on Lactose Lactase works on Lactose from the from butterfrom the from butter
– Maltase work on maltose Maltase work on maltose from breadfrom bread
The Brush Border
Think about Think about the role of the role of
fibrefibre
© UWCM/SONMS/nutrition/MJohn
The fate of foodsProteinsProteins
Polypeptides
Tri-peptides
Di-peptides
Amino acids
FatFat
Glycerol and fatty acids
• Small and Small and long chain long chain fatty acidsfatty acids
CarbohydratesCarbohydrates
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 Think about the role of the role of
fibrefibre
© UWCM/SONMS/nutrition/MJohn
Active transport
mechanism with NA + or H+
Vegetable protein
BeansChyme
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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
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Sympathetic Control
• Norepinephrine
• Functions– Decrease peristalsis– Inhibits secretions– Contracts sphincters– Decreases gut motility
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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, H2O Absorption & Defaecation
Figure 21-27: Anatomy of the large intestine
© UWCM/SONMS/nutrition/MJohn
(Small intestine reabsorbs 7.5 L/day of H20)
• Large Intestine reabsorbs 1.4 L/day
Large Intestine, H2O 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
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