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BIOL 121 > week 10 > Flashcards

week 10 Flashcards

Digestive system

1
Q

Steps in digestion

A
  1. Ingestion 2.Mechanicalprocessing 3.Digestion
  2. Secretion
  3. Absorption
  4. Excretion
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2
Q

Mechanical digestion

A
  • Segmentation

* Constantstirringandmixing •NBforwardmovementviaperistalsis(weakerandslowerhere

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3
Q

Chemical digestion

A
  • ENZYMES!!!
  • Catabolicprocess–itisnecessarytobreakthe fooddowninto‘bits’smallenoughtobe absorbedacrosstheintestinalepithelium
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4
Q

Enzyme

A

“Aproteinthatcatalysesaspecificbiochemicalreaction”

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5
Q

Large interstine

A
  • Reabsorptionofwater
  • Reabsorptionofbilesalts •Absorptionofvitaminsproducedbybacteria •Absorptionoforganicwastes(generatedbybacteria)
  • Peristalticwaves
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6
Q

Thedefecationreflex

A

Two positivefeedback loops

1.Short reflex (local)
•Triggers peristaltic contractions in rectum

2.Long reflex (PSNS –reflex through spinal cord) •Coordinated by sacral parasympathetic system •Stimulates mass movement

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7
Q

Digestive tract

A
  • Digestivetractakagastrointestinal(GI) tractoralimentarycanal
  • Musculartube
  • Extendsfromoralcavitytoanus •Passesthroughpharynx,esophagus,stomach,andsmallandlargeintestines
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8
Q

Role of the GIT

A
  • Largeorganic masses
  • smallerparticles
  • fuel
  • Digestsand absorbsfood
  • ACATABOLICprocess
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9
Q

Functions of the GIT

A
  • Ingestion–foodintomouth
  • Digestion–breakingfoodintoeversmallerbits •Mechanical(chewing,mixing,churning,segmentation) •Chemical(enzymes…catabolism)
  • Secretion–intotheGIT
  • Absorption–endproductintobloodorlymph
  • Defecation–elimination/excretion
  • Motility/Propulsion‐movingthingsalong
  • Defence–againstGITcontents,mechanicalstress,potential pathogens
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10
Q

Movement of digestive materials

A
  • By muscular layers of digestive tract
  • Along digestive tract –Rhythmic cycles of activity –Controlled by pacesetter cells
  • Cells undergo spontaneous depolarization –Triggering wave of contraction through entire muscular sheet
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11
Q

Peristalsis

A

– Consists of waves of muscular contractions

– Moves a bolus along the length of the digestive tract

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12
Q

Segmentation

A

– Cycles of contraction
•Churn and fragment the bolus
•Mix contents with intestinal secretions

–Does not follow a set pattern
•Does not push materials in any one direction

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13
Q

Functions of oral cavity

A

•Sensoryanalysis
–Ofmaterialbeforeswallowing
•Mechanicalprocessing
–Throughactionsofteeth,tongue,andpalatalsurfaces •Lubrication
–Mixingwithmucusandsalivaryglandsecretions •Limiteddigestion
–Ofcarbohydratesandlipids

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14
Q

Saliva

A

Composition

  • 99.4%water
  • 0.6%includeselectrolytes(Na+,Cl‐,andHCO3‐),buffers,glycoproteins (mucins),antibodies,enzymes,wasteproducts

Functions
–Cleaning‐continuouslyflushesoralsurfaces
–Protection
–buffers,antibodies,lysozyme
–Lubricatingthemouth
–Moisteningandlubricatingmaterialsinthemouth
–Dissolvingchemicalsthatstimulatetastebudsandprovidesensory information
–Initiatingdigestion‐salivaryamylase,linguallipase(?)

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15
Q

Oesophagus

A

•Fromlaryngopharynxtostomach •Piercesdiaphragm“oesophagealhiatus” •Joinsstomachatthecardiacorifice •Glandsinsubmucosasecretemucus
•Muscularis
–skeletal‐superiorly
–smooth‐inferiorly

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16
Q

Three phases of swallowing

A

Buccal
Pharyngealphase
Oesophagealphase

17
Q

Major functions of the stomach

A
  • Storageofingestedfood •Mechanicalbreakdownofingestedfood •Disruptionofchemicalbondsinfoodmaterialbyacidandenzyes
  • Productionofintrinsicfactor,aglycoproteinrequiredforabsorptionofvitaminB12 insmall intestine
  • Althoughdigestionoccursinthestomach,nutrientsarenotabsorbed
18
Q

Stomach layers

A

Mucosa
Submucosa
Muscularis externa
Serosa

19
Q

Structure Alimentary canal

A

Mouth
Oesophagus
Stomach
Small intestine

20
Q

Structure AccessoryOrgans

A 
Teeth
Tongue
Salivary glands
Gall bladder
Liver
Pancreas
21
Q

Small intestine

A

•Playskeyroleindigestionandabsorptionofnutrients •90percentofnutrientabsorptionoccursinthesmallintestine •3parts:duodenum,jejunum,ileum

22
Q

Intestine

A

Duodenum
•Receives chyme from stomach and digestive secretions from pancreas and liver
•Acid neutralisation

Jejunum
•Location of most chemical digestion and nutrient absorption

Ileum
•Little nutrient absorption
•Ends at the ileocecal valve
•Lymphoid tissue (Peyer’s patches)

23
Q

Liver

A 
•Largestvisceralorgan(1.5kg) 
•4lobes
•200+functions! 
•Relatedtodigestion 
     –Processblood‐bornenutrientsabsorbedfromSI 
     –Producebile= 900mL/day 
          •Importantforfatdigestion 
     –Storesfat‐solublevitamins 
     –Detoxifies 
          •Toxins 
          •Includingmanydrugs

BIOL 121 (12 decks)

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