w5 pt.2 - alimentary canal

dig + absorp

our role w/ dig sys?

• our knowledge on GI process is asset when work w patients whose nutr status & oral health affected by GI tract disturbances

physiology of GI

alimentary canal - tubular struct (~30ft for avg man)

• include esophagus, stomach, intestine

• accessories = salivary glands, liver, gall, pancreas (secretions essential for dig & absorb)

• path where food enter body & move out thru anus after dig (mouth-anus)

• also called digestive tract

• prim role in digestion

alimentary organs

• mouth/oral cav

• esophagus

• stomach

• small int (duodenum, jejunum, ileum) DJI

• large int (cecum, colon, rectum) CCR

dig sys

mouth

• first part of dig sys (food ingested here)

teeth

• break up food particles for swallow/dig

salivary gland

• prod saliva to moisten food & prod dig enzymes

pharynx

• help prevent food go in lungs

esophagus

• transport food to stomach

liver

• filter harmful subs

• reg biochem rxns

• store fat sol vitamins & min

• help metabolize macronutrs

• synth of protein

• prod bile (dig fat & remove waste)

stomach

• mix food w hydrochloric acid & enzymes

• ^ aid in dig & kill harmful micros

pancreas

• prod bicarbonates to neutralize stomach acid

• help reg blood gluc

small int

• completes dig & absorb most nutr (in jejunum)

large int

• absorb water, some ion

• form & store feces

rectum

• store & expel poop

anus

• exit for poop

dig actions of food

1. chemical action

• food reduced to absorbable molecs

• enzymatic rxns occur to improve dig of carbs, prots, & lipids

• (enzymes = complex prots that speed metabolic rxns w/o exhausting themselves)

2. mechanical (phys) action

• chewing create this to help w dig

• wall of GI tract has musc allowing tube to expand/contract

• churning action = how food particles sep

• breaking & mixing of food = allow better blend w chems

• outer fibs of muscular coat run lengthwise (for peristalsis = invol contractions moving food)

• bile breaking down larg fat droplets to smaller (emuls)

• tongue mixing food w saliva > bolus

nutr process in oral cav

mech

• biting chewing

• smaller food = more SA for dig enzymes to fxn

• saliva has mucus = food stick into bolus, lubricates it for swallow (mech)

chem

• salivary amylase = allow large molecs (carbs) that not fermentable by plaque acids, to be hydrolyzed > shorter fermentable chains

5 steps of healthy dig sys

1. Mouth

• food go in

• mech dig to break/crush/mash food (ex: chew)

• also use enzymes for break down large molecs to small (starch of carb)

2. Esophagus

• move food from mouth > stomach

• peristalsis used (waves of musc contract bring food to stomach using mech dig)

3. Stomach

• crushes & use acid to break proteins

• chem + mech dig to break food & turn large molec to small (so can go into blood)

• to get food to small int, uses chyme (partly dig food + stomach acids)

4. Small Intestine

• most nutr absorb here

• use chem dig to break large molec > small so can go into blood

• liver make bile that’s stored in gall bladder

• pancreatic amylase = digest carb

• pancreatic lipase = digest fat + bile salt from liver emuls

• panc proteases like trypsin = digest protein

• panc bicarbonate = neutralize chyme entering small int

5. Large Intestine

• water & nutr absorb here

• rest of solid mat remaining is waste

Oral cav

(buds, teeth mech, tongue mix, salivary amylase for starch)

• port of entry

• has receptors for taste (buds)

• taste papillae cells replace themselves continuously (affected by disease, drug, nutr status, radiation, age)

• teeth mech breakdown food

• tongue mix food w saliva

• saliva has amylase (break starch)

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• nerve cells carry message to the brain on flavor interpretation

• food stims buds, aromas stim olfactory nerves

Anosmia = loss of smell (can’t taste or tell if food gone bad)

Dysgeusia = persistent taste distortion (taste bitter salty metallic sour)

• caused by prior viral infext

• h&n trauma

• neuro disorder

• systemic cond

• xerostomia

• nerve damage from dent procedure

• bact/fungal infect

Hypogeusia = taste loss

Hypergeusia = heightened/sharpened taste

Saliva

• clear liquid made by glands

• mostly H2O, but also important subs for dig & teeth health

• need enough saliva flow (maint of soft tissues in oral cav + buds)

fxns

• lubricate oral tissues for chew/swallow/dig

• remove debris/microorgs

• antibacterial action

• neutralize dilute buffer bact acids

• remineralize (Ca Phos for enamel)

• prevent plaque accum

• facilitate taste

• ease of speech

demin occur when Ca, Phos, other mins lost from enamel so it dissolve

• minerals of tooth dissolved by org acids (prod by fermentable carbs by acidogenic bact)

• strept mutans, sobrinus, lactobacilli

1st stage caries = Ca & Phos mins dissolved from tooth surf bt plaque biofilm acids

remin

• deposition of mins into prev damaged tooth area

• proc of replenish Ca/phos/F ions

• facil by fluoride therapy

Saliva + fluoride

1) Teeth - crush/grind food (mastication) > bolus

• only small amt of enamel & dentin repaired thru enamel remin

• mineral reposition & resorp affect the bone that support dentin

• deposition (blast) resorp (clast)

• neg Ca balance inc suscept to resorp & bone loss in alveolar proc

• mastic reduces food particle size

• more SA = better dig

• max + mand depend on teeth & occlusal forces from chewing to prevent Ca resorp (mech stim)

• firm foods = maint balance betw alv bone resorp + new bone formation

• teeth + surrounding bone affected by inadequate nutr, dig fxn, & horm balance

hypersensitive, poorly restored, decayed, abscessed, periodontally involved teeth affect food choices & limit variety of foods chosen

2) Esophagus

• tube ~10 inches connect pharynx + stomach

• transport food to stomach

• no digestion

• swallowing reflex move bolus > esophagus (invol, but tongue to pharynx vol)

• then transfer to stomach by peristalsis + grav

peristalsis starts here

swallow = voluntary (oral phase tongue move it)

pharynx = invol (swallow reflex)

esophagus = invol (peristalsis)

3) Stomach

• J-shape muscular bag storing food

• break down into tinier pieces

• mix w/ dig juices w/ enzymes to break proteins + lipids

• acid kill bact

• hydrochloric + others

• bolus enter & mix w stomach’s gastric secretions (make chyme)

low pH (acidic) good for

• kill/inhib food bact growth

• denature proteins & facil hydrolysis to aminos (protein)

• activate gastric enzyme

• hydrolyze some carbs (mostly mouth & small int tho)

• inc solubility & absorp Ca + Iron

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Gastric juice 2 main enzymes = Pepsin + Lipase

• pepsin = hydrolyze (h2o break chem bond) large Protein molec > smaller

• gastric lipase = dig of short/med chain triglycerides (fat)

fast to slow passage thru stomach:

• carb, fat, protein

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• adult stomach hold meal for 3-4 hr

• little absorp here bc few food is fully hydrolyzed to nutr we can actually use atp

4) Small Intestine

• 15 ft long, can retain food for 3-10 hr

• longest part of alimentary

• (DJI) - duodenum, jejunum, ileum

• duodenum = c-shape, dissolve fat & 1st phase of dig (liver prod bile, gall stores, common bile duct into duodenum

• bile salts PHYSICALLY break down large fat globules (emulsify)

• pancreas > pancreatic duct > duodenum for pancreatic lipase to break triglycerides to free fatty acids and monoglycerides

• neutralize chyme (panc bicarbonate)

• pancreatic amylase = digest carb

• pancreatic lipase = digest fat

• panc proteases like trypsin = digest protein

• panc bicarbonate = neutralize chyme entering small int

• bile salt phys emulsify fat

• jejunum = middle, majority of nutrient absorption — sugars, amino acids, fatty acids, vitamins, minerals, water

• ileum = highly coiled & opens to large int

• finish absorption - primarily b12 & bile salts

• most E-providing nutr completely hydrolyzed & absorb here ( + vits & mins)

luminal wall

• villi (finger-like proj that inc SA)

• microvilli (cover villi & inc SA, have brush border enzymes aka digestive proteins that hydrolyze carb, fat, prot

• lactase: splits lactose > glucose & galactose.

• sucrase: splits sucrose > glucose & fructose.

• maltase: breaks down maltose > indiv glucose molecs

L.S.M.

• bile (secr by liver, store in gall, bile salts for mech break of fat)

• panc enzymes (hydrolyze proteins - these are prod & stored in panc as inactive form)

factors affecting dig/absorp is just as important to nutr status as adequate intake is

• amt nutr consumed

• physiologic need

• cond of dig tract (amt secretions & SA)

• lvl of circulating horms

• presence of other nutr or drug (enhance/interfere w absorp)

• presence of adeq amts of dig enzymes

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• nutr absorb occur by passive diff or active transport mechs

passive diff = passage of a permeable sub from more conc soln to area of lower conc

active transp = when absorp is from region of lower conc to higher conc

osmosis = passage of liquid thru semi-perm mem to equalize pressure exerted by ions in sol’ns

• (80-90% of fluid in small int osmosis)

most nutr absorbed thru mucosa of small int into portal circulation

nutr pass into blood thru small int walls

• 80% ingested water

• vits, mins, carb, prot, lipid

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absorp proc for long-chain fatty acid complex

• bc molec large & insoluble

absorp of 4 fat-sol vits (ADEK) not as complex bc bile salt & lipase inc their water solubility (enabling their absorp)

• + other fats in lymph sys

5) Large Intestine

• accepts what small doesn’t absorb

• fiber, water, dead cells go to large int

• (CCR) = cecum, colon, rectum

• only 5% of ingested food & dig secretions advance here

• ex: fibrous stuff (high h2o retention, not digestible, laxative)

• 16-24 hr for food travel whole length

cecum = small sac like, connect small to large int

• appendix connect here = reservoir for beneficial gut bacteria & support the immune sys

• small amt of chyme remaining in ileum released thru ileocecal valce to cecum

colon = 4 parts (ascend, transverse, descend, sigmoid)

• removes h2o, some nutr & electrolytes from partially digested food

rectum = hold feces before expel, open to anus

• large into little/no dig fxn

• reabsorb h2o + electrolyte (Na K)

• form & store feces until defecation

• concentrate waste

• residue in tract is total amt of fecal solids (include undig/unabsorb food, bile pigments & bact products

• fiber = increased residue bc h2o retention = bulkier poo

• dietary fib not dig = work as laxative

• residue benefit = stim peristalsis = improved muscle tone

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Microflora = trillions of harmless microorgs thrive in intestines & essential for health

• body host 10x more microbial cells than human cells

• commonly from grps lactobacillus & bifidobacterium

• composition affect by food patterns (diet w high fiber like veg & whole grain beneficial to health promoting microbes

• imbalance affect health, mood, mem, anxiety

role

• break down fibs & complex carb we can’t dig

• synth vits (K, B12, Biotin, Thiamin, Riboflavin)

• boost immune sys against infect

• inhib pathogenic bact

probiotics = living orgs confering health benefits when present in adeq amts (essential but not considered a nutr)

• each strain unique

• bacterium name = genus, species, strain

• ex: Lactobacillus Adidophilus - 5 (LA-5)

• sources = yogurt w/ live cultures, tempeh, miso, kefir, sauerkraut

how to inc

• plant rich high fiber diet (fruit veg legume)

• ferm foods (yogurt, kefir, tempeh)

• supps (genestra)

• less proc food (sugar trans fat)

• probiotic during/after antibiotic (antibiotic kill good and bad bacteria so)

• residue in larg int need discard

• peristalsis force it into rectum (2-3x/day)

• constipation = fewer than 3x/week

reputable sources of probiotics

• HMF powder = 22b colony forming units (CFU) from 2 strains of lactobacillus

• ex: lactobacillus acidophilus, bifidobacterium bifium, bifidobacterium animalis subsp. lactalis

• HMF intensive = support GI health, abd comfort, healthy microflora

• 50b cfu/dose