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

© UWCM/SONMS/nutrition/MJohn

Absorption

of every day foods


Key Functions: Absorption-• Passage of digested nutrients/fluid across

the GI wall - to blood/lymph-


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 acidsb. CHO has been broken down to monosaccharidesc. Fats have been broken down to fatty acids and

glycerol


Digestion of Beans & Toast

Carbohydrates = no action

Proteins - to peptides

Fat – party broken into triglycerides & fatty acidsChurning turns beans

on toast into chyme


Layers of the Small Bowel


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


Enlarged Villus of Small BowelBrush Border cell


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


“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


Diffusion Process(Micelle)

Butter fat?

Vegetable fat? in chyme

Now Chyme

Think about Think about the role of the role of

fibrefibre


Absorption of Nutrients via Small bowel


Active transport

mechanism with NA + or H+

Vegetable protein

BeansChyme


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


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.


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.


Glucocorticoids

Support the effect of increased Glucagon.

• Promote lipolysis and ketogenesis.

• Promote protein breakdown in muscles.

• Promote liver gluconeogenesis.


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


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


Key Functions: Elimination• Expulsion of undigested and unabsorbed

residues from the gut


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


Bowel - Autonomic Nervous System

• Parasympathetics– Increases colonic motility

• Sympathetics– Promote storage

• Enhance anal tone• Inhibit colonic contractions• Bilateral sympathectomy has little clinical effect


Bowel – Autonomic Nervous System

• Parasympathetic nervous system– PNS functions

• Increase peristalsis• Stimulates secretions• Relaxes sphincters• Increases gut motility


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)


Large Intestine Digestion & Absorption

• Bacterial fermentation: Vit. K , lactate

• Water and electrolyte secretion &/or absorption


Large Intestine Digestion & Absorption


Large Intestine, H2O Absorption & Defaecation

Figure 21-27: Anatomy of the large intestine


(Small intestine reabsorbs 7.5 L/day of H20)

• Large Intestine reabsorbs 1.4 L/day

Large Intestine, H2O Absorption & Defaecation


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)


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


Defaecation Reflex

• mass movement rectal distension internal sphincter (invol)

external sphincter (vol)

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

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