DigestionDigestion: breakdown of food molecules for : breakdown of food molecules for use by the celluse by the cell

Food is broken down by the digestive Food is broken down by the digestive system into a form that can diffuse directly system into a form that can diffuse directly through the wall of the digestive tract and through the wall of the digestive tract and into the bloodinto the blood

Made of Made of digestive tractdigestive tract (muscular tube) (muscular tube) and and accessory organsaccessory organs (salivary glands, (salivary glands, gallbladder, liver, & pancreas)gallbladder, liver, & pancreas)

Functions:Functions:

1) 1) IngestionIngestion: taking food into the mouth: taking food into the mouth

2) 2) Mechanical mixingMechanical mixing: physical : physical manipulation of solid foods by tongue, manipulation of solid foods by tongue, teeth, & muscles of tractteeth, & muscles of tract

3) 3) DigestionDigestion: chemical breakdown of food : chemical breakdown of food into smaller moleculesinto smaller molecules

4) 4) SecretionSecretion: release of water, acids, : release of water, acids, enzymes, and buffersenzymes, and buffers

5) 5) AbsorptionAbsorption: movement of small organic : movement of small organic molecules, electrolytes, vitamins, & water molecules, electrolytes, vitamins, & water across the digestive epithelium & into the across the digestive epithelium & into the interstitial fluidinterstitial fluid

6) 6) ExcretionExcretion: waste products (indigestible : waste products (indigestible substances & worn out cells) are substances & worn out cells) are compacted and discharged by defecationcompacted and discharged by defecation

HistologyHistology

-lining is made of 4 major layers that -lining is made of 4 major layers that secrete, contract, contain blood vessels, & secrete, contract, contain blood vessels, & protect the rest of the body against protect the rest of the body against enzymes, acids, & bacteriaenzymes, acids, & bacteria

1) 1) MucosaMucosa: inner lining: inner lining-epithelium covering a layer of loose -epithelium covering a layer of loose connective tissue (connective tissue (lamina proprialamina propria))-folded to increase surface area, form -folded to increase surface area, form villivilli (fingerlike projections) in small (fingerlike projections) in small

intestineintestine-areas of mechanical stress (mouth -areas of mechanical stress (mouth

esophagus, & anus) have stratified esophagus, & anus) have stratified epithelium, rest has simple epithelium, rest has simple

columnar epitheliumcolumnar epithelium-lamina propria contains secretory cells-lamina propria contains secretory cells-outer layer contains thin muscle that -outer layer contains thin muscle that

contracts to move villi and foldscontracts to move villi and folds

2) 2) SubmucosaSubmucosa: second layer of loose : second layer of loose connective tissueconnective tissue

-large blood vessels, lymph vessels, -large blood vessels, lymph vessels, & & nervesnerves

3) 3) Muscularis externaMuscularis externa: smooth muscle : smooth muscle arranged in circular & longitudinal layersarranged in circular & longitudinal layers

--peristalsisperistalsis: contractions that move : contractions that move contents thru tractcontents thru tract

--segmentationsegmentation: regions of small : regions of small intestine that churn materials to intestine that churn materials to continue mechanical breakdown continue mechanical breakdown

& & mix secretionsmix secretions

4) 4) SerosaSerosa: outer layer, serous membrane: outer layer, serous membrane

-none in mouth, esophagus, & rectum -none in mouth, esophagus, & rectum (covered by dense collagen (covered by dense collagen

fibers fibers ((adventitiaadventitia) that attach these ) that attach these to to surrounding structures)surrounding structures)

--peritoneumperitoneum: lines cavities: lines cavities

--mesentarymesentary: parietal & visceral : parietal & visceral peritoneum that suspends tract peritoneum that suspends tract

to to stabilize organs & prevent stabilize organs & prevent tangling/injurytangling/injury

Oral CavityOral Cavity: part that receives food: part that receives food1) analyzes material1) analyzes material2) mechanically processes material2) mechanically processes material3) lubricates material3) lubricates material4) begins digestion of lipids & 4) begins digestion of lipids & carbohydrates with salivary enzymescarbohydrates with salivary enzymes-anterior boundaries = cheeks & labia -anterior boundaries = cheeks & labia (lips)(lips)

--vestibulevestibule: space between : space between cheeks/lips cheeks/lips & teeth& teeth

--gingivaegingivae: gums that surround teeth : gums that surround teeth basebase

-superior boundary = hard & soft palates-superior boundary = hard & soft palates

-inferior = tongue-inferior = tongue

--lingual frenulumlingual frenulum: fold that connects : fold that connects anterior tongue to underlying anterior tongue to underlying tissuestissues

-posterior = -posterior =

base of tongue base of tongue

& uvula& uvula

The TongueThe Tongue

TongueTongue: manipulate food inside the mouth: manipulate food inside the mouth

-Functions-Functions

1) mechanical processing by 1) mechanical processing by compression, abrasion, & distortioncompression, abrasion, & distortion

2) manipulate to help chewing & 2) manipulate to help chewing & swallowingswallowing

3) sensory analysis by touch, taste, & 3) sensory analysis by touch, taste, & temperature receptorstemperature receptors

Salivary GlandsSalivary Glands

-3 pairs-3 pairs

1) 1) Parotid salivary glandsParotid salivary glands

2) 2) sublingual salivary glandssublingual salivary glands

3) 3) Submandibular salivary glandsSubmandibular salivary glands

-produce 1 – 1.5 liters of saliva daily-produce 1 – 1.5 liters of saliva daily

-made of 99.4% water with ions, buffers, -made of 99.4% water with ions, buffers, waste products, metabolites, & waste products, metabolites, &

enzymesenzymes

-lubricates & dissolves chemicals to -lubricates & dissolves chemicals to stimulate taste buds when eatingstimulate taste buds when eating

-mucus reduces friction when swallowing-mucus reduces friction when swallowing

-continuous production flushes oral cavity -continuous production flushes oral cavity & produces immunoglobulins & & produces immunoglobulins &

lysozymes to kill bacteria lysozymes to kill bacteria

-production failure would cause -production failure would cause infection & erosion of teeth & infection & erosion of teeth &

gumsgums

SecretionsSecretions--salivary amylasesalivary amylase: produced by parotid, : produced by parotid,

breaks down starchbreaks down starch

-other gland products contain less enzymes -other gland products contain less enzymes but more buffers & mucusbut more buffers & mucus

-max. production is 7ml/minute-max. production is 7ml/minute-submandibular produces 70% of volume-submandibular produces 70% of volume-normal pH = 6.7, shifts to 7.5 during -normal pH = 6.7, shifts to 7.5 during eatingeating

TeethTeeth

MasticationMastication: chewing: chewing

-breaks down tough connective tissue & -breaks down tough connective tissue & plant fibersplant fibers

-helps disperse saliva (mucus & enzymes)-helps disperse saliva (mucus & enzymes)

PARTSPARTS

1. 1. NeckNeck: boundary between root & crown: boundary between root & crown

2. 2. RootRoot: part surrounded by bone: part surrounded by bone

3. 3. CrownCrown: exposed section: exposed section

-covered by -covered by enamelenamel: crystalline form of : crystalline form of calcium phosphate (hardest biologically calcium phosphate (hardest biologically made substance)made substance)

-requires adequate calcium, phosphates, -requires adequate calcium, phosphates, & Vitamin D in diet for complete & Vitamin D in diet for complete

coating coating & decay resistance& decay resistance

4. 4. DentinDentin: mineralized matrix that makes up : mineralized matrix that makes up most of toothmost of tooth

-does not contain living cells-does not contain living cells

5. 5. Pulp cavityPulp cavity: central area: central area

-cells extend into dentin-cells extend into dentin

-receives blood vessels & nerves through -receives blood vessels & nerves through root canalroot canal

6. 6. AlveolusAlveolus: socket in bone where root : socket in bone where root extendsextends

7. 7. Periodontal ligamentPeriodontal ligament: collagen fibers : collagen fibers that connect root dentin to bonethat connect root dentin to bone

8. 8. CementumCementum: layer covering root dentin: layer covering root dentin

-gives protection & anchors root to -gives protection & anchors root to periodontal ligamentperiodontal ligament

-softer, can be easily eroded -softer, can be easily eroded if gum disease allows if gum disease allows

bacterial infectionbacterial infection

Types of TeethTypes of Teeth

1. 1. IncisorsIncisors: used for clipping/cutting: used for clipping/cutting

-most anterior-most anterior

2. 2. CuspidsCuspids: Canines, used for tearing & : Canines, used for tearing & slashingslashing

-conical w/ ridgeline & pointed tip-conical w/ ridgeline & pointed tip

2. 2. BicuspidsBicuspids (premolars) & (premolars) & MolarsMolars::

-flattened crowns w/ large ridges-flattened crowns w/ large ridges

-used for crushing, mashing, & grinding-used for crushing, mashing, & grinding

Tooth DevelopmentTooth DevelopmentDeciduous teethDeciduous teeth: first teeth to appear: first teeth to appear

-20 total-20 total-periodontal ligaments & roots erode & -periodontal ligaments & roots erode & teeth fall outteeth fall out

Secondary teethSecondary teeth: permanent dentition: permanent dentition-permit processing of a wider variety of -permit processing of a wider variety of foodfood-32 total-32 total--impactedimpacted: develop in locations that don’t : develop in locations that don’t

allow proper eruptionallow proper eruption

comPharynxPharynx--common passageway for food, air, & liquidcommon passageway for food, air, & liquid

-food passes thru oropharynx & -food passes thru oropharynx & laryngopharynxlaryngopharynx

-muscles help initiate swallowing-muscles help initiate swallowing

EsophagusEsophagus

-muscular tube connecting pharynx & -muscular tube connecting pharynx & stomachstomach

-lies posterior to trachea, passes thru -lies posterior to trachea, passes thru mediastinum &mediastinum & esophageal hiatusesophageal hiatus: : opening in diaphragmopening in diaphragm

-25 cm long, 2cm diameter-25 cm long, 2cm diameter

-lined w/ stratified squamous epithelium -lined w/ stratified squamous epithelium for protection & mucous glands to for protection & mucous glands to lubricatelubricate

DeglutitionDeglutition: Swallowing: Swallowing

-food must have proper texture & -food must have proper texture & consistencyconsistency

-tongue creates -tongue creates

bolusbolus: small mass: small mass

-takes 9 seconds to -takes 9 seconds to

complete processcomplete process

-Phases-Phases

1) 1) Oral phaseOral phase: voluntary: voluntary

-bolus compressed against hard -bolus compressed against hard palate palate & is forced into oropharynx & is forced into oropharynx while while elevating the soft palateelevating the soft palate

2) 2) Pharyngeal phasePharyngeal phase: involuntary : involuntary swallowing reflexswallowing reflex

-larynx elevates & epiglottis folds to -larynx elevates & epiglottis folds to close tracheaclose trachea

-pushes bolus thru -pushes bolus thru upper esophageal upper esophageal sphinctersphincter into esophagus into esophagus

3) 3) Esophageal phaseEsophageal phase: involuntary: involuntary

-bolus pushed thru esophagus to -bolus pushed thru esophagus to lower lower esophageal sphincteresophageal sphincter & into & into

stomach by peristalsisstomach by peristalsis

EsophagitisEsophagitis: inflammation of the esophagus : inflammation of the esophagus due to weak/relaxed esophageal sphincter due to weak/relaxed esophageal sphincter that allows acid reflexthat allows acid reflexHeartburnHeartburn: occasional occurrence : occasional occurrence

Hiatal (Diaphragmatic) HerniaHiatal (Diaphragmatic) Hernia: abdominal : abdominal organs slide into thoracic cavity thru organs slide into thoracic cavity thru esophageal hiatusesophageal hiatus-severity depends on location, size, & -severity depends on location, size, & number of herniated organs number of herniated organs -mild condition is common & mostly -mild condition is common & mostly unnoticed unnoticed

StomachStomach

-muscular, J-shaped organ that -muscular, J-shaped organ that receives food from esophagusreceives food from esophagus

-4 functions-4 functions

1) temporary storage of ingested food1) temporary storage of ingested food

2) mechanical breakdown of resistant 2) mechanical breakdown of resistant materialsmaterials

3) chemical breakdown by acids & 3) chemical breakdown by acids & enzymesenzymes

4) production of 4) production of intrinsic factorintrinsic factor needed for needed for vitamin Bvitamin B1212 absorption absorption

--chymechyme: viscous, acidic mixture of partially : viscous, acidic mixture of partially digested food created in stomachdigested food created in stomach

-4 regions-4 regions

1) 1) cardiacardia: surrounding esophagus : surrounding esophagus opening, smallestopening, smallest

2) 2) fundusfundus: bulge superior to cardia: bulge superior to cardia

3) 3) bodybody: large central area: large central area

4) 4) pyloruspylorus: narrow inferior area, where : narrow inferior area, where stomach connects to small intestine at stomach connects to small intestine at pyloric sphincterpyloric sphincter: regulates flow of : regulates flow of chyme into small intestinechyme into small intestine

-can expand to hold ~1.5 L-can expand to hold ~1.5 L-muscularis externa is thick & contains -muscularis externa is thick & contains

longitudinal, circular, & inner oblique longitudinal, circular, & inner oblique layers to add strength & mix/churn layers to add strength & mix/churn contentscontents

--rugaerugae: large ridges & folds in mucosa that : large ridges & folds in mucosa that allow for distension allow for distension

-visceral peritoneum-visceral peritoneum

a) a) greater omentumgreater omentum: extends inferior & : extends inferior & creates pouch that hangs over & creates pouch that hangs over & protects abdominal organsprotects abdominal organs

b) b) lesser omentumlesser omentum: extends from lesser : extends from lesser curvature to livercurvature to liver

-lined by mucous epithelium that creates a -lined by mucous epithelium that creates a protective alkaline mucousprotective alkaline mucous

--gastric pitsgastric pits: shallow depressions that open : shallow depressions that open onto gastric surfaceonto gastric surface

-end with gastric glands-end with gastric glands

-secrete 1500 ml daily-secrete 1500 ml daily

-2 gland types-2 gland types

1) 1) Parietal cellsParietal cells

-secrete -secrete intrinsic factorintrinsic factor: facilitate : facilitate vitamin Bvitamin B1212 absorption across absorption across

intestinal liningintestinal lining

-secretes hydrochloric acid to -secretes hydrochloric acid to lower pH to 1.5 – 2lower pH to 1.5 – 2

-kills microorganisms, breaks -kills microorganisms, breaks cell walls/connective cell walls/connective tissue, & activates tissue, & activates enzymatic secretionsenzymatic secretions

2)2) Chief CellsChief Cells: :

-secrete -secrete pepsinogenpepsinogen: inactive : inactive enzyme, converted into enzyme, converted into

pepsinpepsin (proteolytic enzyme) by (proteolytic enzyme) by hydrochloric acidhydrochloric acid

GastritisGastritis: inflammation of the gastric : inflammation of the gastric mucosamucosa-causes: drugs, alcohol, aspirin, severe -causes: drugs, alcohol, aspirin, severe emotional/physical stress, bacterial emotional/physical stress, bacterial infection, or ingesting highly infection, or ingesting highly acidic/alkaline chemicalsacidic/alkaline chemicals

Peptic ulcerPeptic ulcer: acids & enzymes erode thru : acids & enzymes erode thru mucous & stomach lining, or beginning of mucous & stomach lining, or beginning of small intestinesmall intestine-caused by excessive acid production or -caused by excessive acid production or

inadequate alkaline mucous inadequate alkaline mucous productionproduction-bacteria infection causes 80%-bacteria infection causes 80%

Phases of gastric regulationPhases of gastric regulation

1) 1) Cephalic phaseCephalic phase::

-begins with sight, smell, taste, or thought -begins with sight, smell, taste, or thought of foodof food

-prepares stomach-prepares stomach

-gastric juice production reaches 500 -gastric juice production reaches 500 ml/hrml/hr

2) 2) Gastric phaseGastric phase::-begins as food reaches stomach-begins as food reaches stomach-stretch receptors & chemoreceptors -stretch receptors & chemoreceptors cause release of hormone gastrin into cause release of hormone gastrin into bloodblood-causes parietal & chief cells to increase -causes parietal & chief cells to increase

productionproduction-may continue for several hours-may continue for several hours-stomach contracts to churn/mix contents, -stomach contracts to churn/mix contents,

pylorus contractions squirt small pylorus contractions squirt small amounts of chyme thru phyloric amounts of chyme thru phyloric sphinctersphincter

3) 3) Intestinal phaseIntestinal phase::

-controls gastric emptying rate-controls gastric emptying rate

-inhibitory to reduce gastric juices so small -inhibitory to reduce gastric juices so small intestine has time to deal with & intestine has time to deal with &

neutralize acidic chymeneutralize acidic chyme

Digestion in StomachDigestion in Stomach-preliminary protein digestion-preliminary protein digestion-carbohydrates broken down by salivary -carbohydrates broken down by salivary

amylase until pH reaches 4.5 (1-2 hrs)amylase until pH reaches 4.5 (1-2 hrs)-no absorption occurs-no absorption occurs

-thick mucous layer-thick mucous layer-epithelial cells not specialized for -epithelial cells not specialized for transporttransport-gastric lining impermeable to water-gastric lining impermeable to water-digestion not complete (protein & -digestion not complete (protein & carbohydrates only partially digested)carbohydrates only partially digested)

Small IntestineSmall Intestine

-90% of nutrient absorption-90% of nutrient absorption

-6m (20ft) long, diameter 2.5 – 4 cm-6m (20ft) long, diameter 2.5 – 4 cm

-3 subdivision-3 subdivision

1) 1) DuodenumDuodenum: 25cm (1ft) long: 25cm (1ft) long

-receives chyme from stomach & -receives chyme from stomach & secretions from pancreas & liversecretions from pancreas & liver

2) 2) JejunumJejunum: starts at 1: starts at 1stst bend, 2.5m (8ft) bend, 2.5m (8ft)

-most of chemical digestion & nutrient -most of chemical digestion & nutrient absorption occursabsorption occurs

3) 3) IleumIleum: 3.5m (12ft) long: 3.5m (12ft) long

-ends at -ends at ileocecal valveileocecal valve, sphincter , sphincter that that leads to leads to cecumcecum of large intestine of large intestine

-fits into relatively small space because it’s -fits into relatively small space because it’s well-packed & stabilized by mesentarieswell-packed & stabilized by mesentaries

Intestinal wallIntestinal wall

--plicaeplicae: series of transverse folds: series of transverse folds

--villivilli: fingerlike projections: fingerlike projections

-covered with simple columnar -covered with simple columnar epithelium & microvilliepithelium & microvilli

-folds increase surface area for absorption -folds increase surface area for absorption 611x611x

-capillaries carry respiratory gases & -capillaries carry respiratory gases & absorbed nutrients to liverabsorbed nutrients to liver

--lacteallacteal: lymph vessel in each villus: lymph vessel in each villus

-transport materials that can’t cross -transport materials that can’t cross into into capillaries (e.g. fatty acids)capillaries (e.g. fatty acids)

-intestinal glands lie at villi base-intestinal glands lie at villi base

-secrete watery intestinal juice-secrete watery intestinal juice

Intestinal MovementsIntestinal Movements

-segmentation mixes chyme w/ secretions & -segmentation mixes chyme w/ secretions & enzymes to prepare for absorptionenzymes to prepare for absorption

-weak peristaltic contractions move material from -weak peristaltic contractions move material from duodenum thru ileum in about 5 hoursduodenum thru ileum in about 5 hours

Intestinal juiceIntestinal juice: 1.8 L secreted into lumen : 1.8 L secreted into lumen each dayeach day

-moistens contents, buffers acids, & -moistens contents, buffers acids, & dissolves enzymes & products of dissolves enzymes & products of digestiondigestion

ProductsProducts

-food is broken into simple sugars, fatty -food is broken into simple sugars, fatty acids, & amino acids which are absorbed acids, & amino acids which are absorbed with most of waterwith most of water

PancreasPancreas--elongated, pink/gray organelongated, pink/gray organ

-15 cm (6 in.) & 80 g (3 oz.)-15 cm (6 in.) & 80 g (3 oz.)

-lumpy texture w/ soft tissue that is easily -lumpy texture w/ soft tissue that is easily torntorn

Pancreatic juicePancreatic juice: secretion of digestive enzymes : secretion of digestive enzymes & buffers & carried thru ducts that converge at & buffers & carried thru ducts that converge at pancreatic ductpancreatic duct which funnels juice to which funnels juice to duodenumduodenum-1000 ml secreted daily-1000 ml secreted daily-make-up-make-up

-buffer (sodium bicarbonate) with pH of -buffer (sodium bicarbonate) with pH of 7.5 to 8.8 to neutralize chyme7.5 to 8.8 to neutralize chyme-pancreatic amylase: carbohydrates-pancreatic amylase: carbohydrates-pancreatic lipase: lipids-pancreatic lipase: lipids-nucleases: nucleic acids-nucleases: nucleic acids-proteases: proteins, 70% of total volume-proteases: proteins, 70% of total volume

-enzymes are secreted as -enzymes are secreted as proenzymesproenzymes, , inactive form that are activated by inactive form that are activated by enzymes in the small intestine to protect enzymes in the small intestine to protect lining of pancreatic ductslining of pancreatic ducts

LiverLiver-largest organ, 3.3 lbs, 2.5% of total body -largest organ, 3.3 lbs, 2.5% of total body

weightweight

-essential metabolic & synthetic functions-essential metabolic & synthetic functions

-tough fibrous capsule -tough fibrous capsule

-4 lobes-4 lobes

-large right & left lobes separated by -large right & left lobes separated by faliciform ligamentfaliciform ligament

-smaller caudate & quadrate lobes-smaller caudate & quadrate lobes

-Histology-Histology

--liver lobulesliver lobules: basic functional unit : basic functional unit

-~100,000-~100,000

-lined with -lined with Kupffer cellsKupffer cells: phagocytic : phagocytic macrophages that engulf pathogens, macrophages that engulf pathogens, cell debris, & damaged blood cellscell debris, & damaged blood cells

-as blood flows past, hepatocytes adjust -as blood flows past, hepatocytes adjust levels by selective absorption levels by selective absorption

(glucose) (glucose) & secretion& secretion-secrete -secrete bilebile (digestive fluid) into (digestive fluid) into common hepatic ductcommon hepatic duct as it leaves as it leaves

-can flow into-can flow intoa. a. common bile ductcommon bile duct: empties : empties into duodenuminto duodenumb. b. common cystic ductcommon cystic duct: leads to : leads to

gallbladdergallbladder

Liver FunctionsLiver Functions

-more than 200 identified-more than 200 identified

1) Metabolic regulation1) Metabolic regulation

-regulated composition of circulatory blood-regulated composition of circulatory blood

-after absorption in intestines blood travels -after absorption in intestines blood travels to liverto liver

a. extracts toxins & metabolic wastes a. extracts toxins & metabolic wastes that will be inactivated/excretedthat will be inactivated/excreted

b. monitor & adjust organic nutrient b. monitor & adjust organic nutrient levelslevels-remove & store excess, -remove & store excess,

synthesize or release synthesize or release deficienciesdeficienciese.g. e.g. blood sugar-breaks blood sugar-breaks

down glycogendown glycogen blood sugar-absorbs blood sugar-absorbs

glucose & builds glucose & builds glycogenglycogen

-fat-soluble vitamins (A, D, K, & -fat-soluble vitamins (A, D, K, & E) E) absorbed & storedabsorbed & stored

2) Hematological regulation2) Hematological regulation

-largest blood reservoir (25% of cardiac -largest blood reservoir (25% of cardiac output)output)

-Kupffer cells “clean” blood-Kupffer cells “clean” blood

-synthesize plasma proteins for osmotic -synthesize plasma proteins for osmotic control, nutrient transport, & clotting control, nutrient transport, & clotting systemssystems

3) Bile Production3) Bile Production

-water, ions, -water, ions, bilirubinbilirubin (pigment derived (pigment derived from hemoglobin breakdown), from hemoglobin breakdown), cholesterol, & cholesterol, & bile saltsbile salts (lipids) (lipids)

-water & ions dilute & buffer acids-water & ions dilute & buffer acids

-bile salts -bile salts emulsifyemulsify (create tiny drops) (create tiny drops) lipids that aren’t water-soluble & lipids that aren’t water-soluble & normally form large blobs that are normally form large blobs that are difficult to breakdowndifficult to breakdown

-increase surface area to allow -increase surface area to allow lipases lipases to digest fatsto digest fats

GallbladderGallbladder-pear-shaped muscular organ that stores & -pear-shaped muscular organ that stores &

modified bilemodified bile

-nestled under right lobe of liver-nestled under right lobe of liver

-liver produces 1L of bile daily, sphincter to -liver produces 1L of bile daily, sphincter to common bile duct remains closed until common bile duct remains closed until chyme reaches duodenumchyme reaches duodenum

-most bile travels to gallbladder via cystic -most bile travels to gallbladder via cystic ductduct

-can hold 40-70 ml-can hold 40-70 ml

-during storage bile loses water & becomes -during storage bile loses water & becomes more concentrated (if too much water is more concentrated (if too much water is lost, bile salts precipitate out forming lost, bile salts precipitate out forming gallstones)gallstones)

-wall contractions push bile into duodenum-wall contractions push bile into duodenum

-- fat content in chyme fat content in chyme bile secretions bile secretions

Large IntestineLarge Intestine-runs from end of ileum to anus-runs from end of ileum to anus

-main functions-main functions

1) water reabsorption & feces compaction1) water reabsorption & feces compaction

2) absorption of vitamins released by 2) absorption of vitamins released by bacterial actionbacterial action

3) storage of fecal material for defecation3) storage of fecal material for defecation

-1.5m (5 ft) long & 3 in diameter-1.5m (5 ft) long & 3 in diameter

-3 parts-3 parts

1) 1) CecumCecum: expanded chamber where : expanded chamber where contents enter from ileum thru contents enter from ileum thru ileocecal ileocecal valvevalve--veriform appendixveriform appendix: small thin pouch : small thin pouch attached to inferior areaattached to inferior area

-contains lymph tissue-contains lymph tissue-can become -can become

infected if infected if bacteria bacteria become become trapped & trapped & divide rapidlydivide rapidly

2) 2) ColonColon: 4 regions, dominated by : 4 regions, dominated by haustrahaustra: : pouches that permit distension & pouches that permit distension & elongationelongation-3 longitudinal muscle -3 longitudinal muscle (taeniae coli(taeniae coli) help ) help

bunch to create haustra bunch to create haustra -regions-regions

a) a) ascending colonascending colon: from ileocecal : from ileocecal valve to bendvalve to bend

b) b) transverse colontransverse colon: horizontal region: horizontal regionc) c) descending colondescending colon: inferior to bend: inferior to bendd) d) sigmoid colonsigmoid colon: S-shaped, empties : S-shaped, empties

into rectuminto rectum

3) 3) RectumRectum: end of digestive tract: end of digestive tract

-ends with anal canal-ends with anal canal

-boundary between simple columnar & -boundary between simple columnar & stratified squamous tissuesstratified squamous tissues

--anusanus: anal canal opening of keratinized : anal canal opening of keratinized skinskin

--internal anal sphincterinternal anal sphincter: : involuntary, involuntary,

--external anal sphincterexternal anal sphincter: : voluntaryvoluntary

Large Intestine FunctionsLarge Intestine Functions1) Absorption1) Absorption

-1500ml of material passes thru ileocecal -1500ml of material passes thru ileocecal sphincter dailysphincter daily

-1300ml of water is recovered, 200ml of -1300ml of water is recovered, 200ml of feces are defecatedfeces are defecated-fecal content-fecal content

-75% water-75% water-5% bacteria-5% bacteria-20% indigestible material, inorganic -20% indigestible material, inorganic

matter, & dead cellsmatter, & dead cells

a) bile salts-reabsorbed & transported to a) bile salts-reabsorbed & transported to liver for re-useliver for re-useb) vitamins-organic molecules needed to b) vitamins-organic molecules needed to metabolic reactions (many assist metabolic reactions (many assist enzymes)enzymes)

-generated by bacteria-generated by bacteria1. Vitamin K-needed by liver to 1. Vitamin K-needed by liver to

create clotting factors, create clotting factors, bacteria produce 50% of daily bacteria produce 50% of daily requirementrequirement

2. Biotin-glucose metabolism2. Biotin-glucose metabolism

3. Vitamin B3. Vitamin B55-pantothenic acid, help -pantothenic acid, help produce steroid hormones & produce steroid hormones &

some some neurotransmittersneurotransmitters

c) Bilirubin products-bacteria convert into c) Bilirubin products-bacteria convert into products that can be excreted in urine products that can be excreted in urine (create yellow color), or others stay & (create yellow color), or others stay & turn brown when exposed to oxygenturn brown when exposed to oxygen

d) Toxins-peptide breakdown creates d) Toxins-peptide breakdown creates ammonia, nitrogen-containing ammonia, nitrogen-containing compounds (most odor), hydrogen compounds (most odor), hydrogen sulfide, many are removed by liver & sulfide, many are removed by liver & excreted by kidneysexcreted by kidneys

-Indigestible carbohydrates provide food -Indigestible carbohydrates provide food source for bacteriasource for bacteria

2) 2) DefecationDefecation: forcing feces out the sigmoid : forcing feces out the sigmoid coloncolon--defecation reflexdefecation reflex::

-stretch receptors trigger peristalsis in -stretch receptors trigger peristalsis in colon & rectum to move feces colon & rectum to move feces toward anustoward anus

-increases peristalsis throughout -increases peristalsis throughout large large intestineintestine-removal requires internal sphincter to -removal requires internal sphincter to relax, which immediately causes the relax, which immediately causes the external sphincter to shut until external sphincter to shut until conscious conscious control opens itcontrol opens it