Unit C1-2: Human Unit C1-2: Human Biology (Digestive Biology (Digestive

System)System) Students who have fully met the prescribed learning Students who have fully met the prescribed learning outcomes (PLO’s) are able to:outcomes (PLO’s) are able to:

C1. Analyze the functional inter-relationships of the C1. Analyze the functional inter-relationships of the structures of the digestive system.structures of the digestive system.

Identify and give a function for each of the following:Identify and give a function for each of the following: -mouth-mouth -duodenum-duodenum

-tongue-tongue -liver-liver -teeth-teeth -gall bladder-gall bladder -salivary glands-salivary glands -pancreas-pancreas -pharynx-pharynx -small intestine-small intestine -epiglottis-epiglottis -large intestine (colon)-large intestine (colon) -esophagus-esophagus -appendix-appendix -cardiac sphincter-cardiac sphincter -rectum-rectum -stomach-stomach -anus-anus -pyloric sphincter-pyloric sphincter

Digestion PLO’sDigestion PLO’s Describe swallowing and peristalsis.Describe swallowing and peristalsis. Identify the pancreas as the source gland for Identify the pancreas as the source gland for

insulin, and describe the function of insulin in insulin, and describe the function of insulin in maintaining blood sugar levels.maintaining blood sugar levels.

List at least six major functions of the liver.List at least six major functions of the liver.

Explain the role of bile in the emulsification of Explain the role of bile in the emulsification of fats. fats.

Digestion PLO’sDigestion PLO’s Describe how the small intestine is specialized Describe how the small intestine is specialized

for chemical and physical digestion and for chemical and physical digestion and absorption.absorption.

Describe the structure of the villus, including Describe the structure of the villus, including microvilli, and explain the functions of the microvilli, and explain the functions of the capillaries and lacteals within it.capillaries and lacteals within it.

Describe the functions of anaerobic bacteria in Describe the functions of anaerobic bacteria in the colon.the colon.

Demonstrate the correct use of the dissection Demonstrate the correct use of the dissection microscope to examine the various structures of microscope to examine the various structures of the digestive systemthe digestive system..

Digestion PLO’s (Last set!)Digestion PLO’s (Last set!) Describe the role of sodium bicarbonate in Describe the role of sodium bicarbonate in

pancreatic juice.pancreatic juice.

Describe the role of hydrochloric acid Describe the role of hydrochloric acid (HCl) in gastric juice.(HCl) in gastric juice.

Describe the role of mucus in gastric juice.Describe the role of mucus in gastric juice.

Describe the importance of the pH level in Describe the importance of the pH level in various regions of the digestive tract.various regions of the digestive tract.

C1 – Organs and Their C1 – Organs and Their FunctionsFunctions::

First off…..the MOUTH!!First off…..the MOUTH!!

Mouth…where it all beginsMouth…where it all begins Receives food to be broken down Receives food to be broken down

physicallyphysically (teeth)and (teeth)and chemicallychemically.. Location of starch digestion/first place Location of starch digestion/first place

of chemical digestion of starch. of chemical digestion of starch.

Saliva in mouth provides Saliva in mouth provides optimaloptimal pH pH

77 for salivary amylase. for salivary amylase.

TongueTongue Forms chewed food Forms chewed food

into ainto a bolusbolus (ball (ball of food) before of food) before swallowing.swallowing.

Initiates Initiates swallowing. swallowing.

Teeth! Chomp chomp….Teeth! Chomp chomp….

Mechanical/Mechanical/physical physical breakdown of food breakdown of food (mastication). (mastication).

Salivary GlandsSalivary Glands Three pairs of glands that secrete Three pairs of glands that secrete

saliva into the mouth via ducts.saliva into the mouth via ducts.

Produces Produces salivasaliva containing containing water, water, mucusmucus, , salivary amylasesalivary amylase and and buffersbuffers which, lubricate food, and which, lubricate food, and breakdown starch into maltose. (It breakdown starch into maltose. (It also contains the enzyme, lysozyme also contains the enzyme, lysozyme that lyses oral bacteria).that lyses oral bacteria).

Salivary GlandsSalivary Glands

Pharynx Pharynx A region between A region between

the mouth, the mouth, esophagus, and esophagus, and trachea.trachea.

Passageway for Passageway for food, water, air, and food, water, air, and for the reflex action for the reflex action of swallowing as it of swallowing as it enters the enters the esophagus. esophagus.

Epiglottis…so you don’t Epiglottis…so you don’t choke!choke!

A flap of tissue that A flap of tissue that covers the covers the glottisglottis (opening of the (opening of the trachea).trachea).

Prevents food from Prevents food from entering the entering the trachea when trachea when swallowing. swallowing.

EsophagusEsophagus Transfers the bolus Transfers the bolus

from the mouth to from the mouth to the stomach by the stomach by peristalsisperistalsis (rhythmic smooth (rhythmic smooth muscle muscle contractions).contractions).

Secretes Secretes mucusmucus for lubrication for lubrication

Cardiac SphincterCardiac Sphincter Circular muscle at the junction of the Circular muscle at the junction of the

esophagus and stomach.esophagus and stomach.

Relaxation of sphincter allows bolus Relaxation of sphincter allows bolus to enter stomach and contraction to enter stomach and contraction prevents stomach chyme from re-prevents stomach chyme from re-entering the esophagus. entering the esophagus.

StomachStomach J-shaped muscular and J-shaped muscular and

glandular organ on the glandular organ on the left side of body below left side of body below the diaphragm.the diaphragm.

Stomach wall contains Stomach wall contains deep folds (deep folds (rugaerugae) ) which provide a which provide a greater surface area greater surface area for food and fluids.for food and fluids.

Storage of food Storage of food

Stomach continuedStomach continued Mechanical churning of food into Mechanical churning of food into chymechyme by by

smooth muscle fibres.smooth muscle fibres.

Secrete Secrete mucusmucus for protection and lubrication by for protection and lubrication by goblet cells.goblet cells.

Secretes Secretes HClHCl and and pepsinogenpepsinogen (inactive form of (inactive form of pepsinpepsin) by gastric glands.) by gastric glands.

Secretes Secretes gastric juicegastric juice produced by gastric produced by gastric glands containing Hglands containing H22O, HCl, pepsinogen (pepsin), O, HCl, pepsinogen (pepsin), and mucus. HCl provides and mucus. HCl provides optimaloptimal pH 2-3pH 2-3 for for pepsin.pepsin.

StomachStomach First place of First place of

chemical chemical digestion of digestion of proteinsproteins..

Secretes gastrin Secretes gastrin (hormone), which (hormone), which releases more releases more gastric juice from gastric juice from gastric glands. gastric glands.

Pyloric SphincterPyloric Sphincter A circular ring of A circular ring of

muscle at the junction muscle at the junction of the stomach and of the stomach and duodenum.duodenum.

Relaxation of the Relaxation of the sphincter allows acid sphincter allows acid chyme to enter the chyme to enter the duodenum, duodenum,

i.e. controls the amount i.e. controls the amount of chyme entering the of chyme entering the duodenum and duodenum and contraction keeps chyme contraction keeps chyme within the stomach. within the stomach.

DuodenumDuodenum First 30cm of the small intestine.First 30cm of the small intestine. Receives acid chyme from stomach, Receives acid chyme from stomach,

pancreatic juice from pancreas, and pancreatic juice from pancreas, and bile from gall bladder; peristalsis bile from gall bladder; peristalsis occurs here.occurs here.

Bile begins its first emulsification of Bile begins its first emulsification of lipids here, i.e. lipids physically lipids here, i.e. lipids physically broken down into lipid droplets.broken down into lipid droplets.

DuodenumDuodenum

Duodenum ContinuedDuodenum Continued Majority of chemical digestion (see Majority of chemical digestion (see

below) and the first neutralization below) and the first neutralization (via NaHCO(via NaHCO33) of acidic chyme occur ) of acidic chyme occur here. NaHCOhere. NaHCO33 provides provides optimaloptimal pH pH 8-98-9 for pancreatic amylase, lipase, for pancreatic amylase, lipase, trypsin, intestinal & pancreatic trypsin, intestinal & pancreatic nuclease, peptidase and maltase. nuclease, peptidase and maltase.

Enzymes at workEnzymes at workHH22OO

starch maltosestarch maltosepancreatic amylasespancreatic amylases

HH22OO

maltose glucosemaltose glucose maltasemaltase

HH22OO

proteins peptidesproteins peptides trypsintrypsin

More enzymesMore enzymesH2OH2O

peptides amino acidspeptides amino acids peptidasepeptidase H2OH2Onucleic acids nucleotidesnucleic acids nucleotides pancreatic & intestinal pancreatic & intestinal

nucleasesnucleases H2OH2Olipid droplets glycerol & lipid droplets glycerol & lipaselipase fatty acids fatty acids

LiverLiver Refer to major liver functions for specificsRefer to major liver functions for specifics.. Accessory organ for digestion consisting of four Accessory organ for digestion consisting of four

lobes, located under the diaphragm.lobes, located under the diaphragm. Approximately 1.5kg in weight.Approximately 1.5kg in weight. Highly vascularized.Highly vascularized. Produces Produces bilebile (bile salts) necessary for (bile salts) necessary for

emulsifying lipids (thus increasing surface area emulsifying lipids (thus increasing surface area for chemical digestion by lipfor chemical digestion by lipasease). ).

Gall BladderGall Bladder Accessory organ for Accessory organ for

digestion.digestion. Pear-shaped sac Pear-shaped sac

located in a located in a depression on the depression on the underside of the liver.underside of the liver.

Stores and Stores and concentrates bile from concentrates bile from the liver and carries it the liver and carries it to the duodenum via to the duodenum via the bile duct. the bile duct.

PancreasPancreas Refer to function of Refer to function of

insulin for specificsinsulin for specifics.. Accessory organ for Accessory organ for

digestion.digestion. Oblong gland, Oblong gland,

approximately approximately 12.5cm, which lies 12.5cm, which lies behind the stomach behind the stomach and made up of and made up of clusters of glandular clusters of glandular cells.cells.

PancreasPancreas Secretes Secretes pancreatic juicepancreatic juice containing H containing H22O, O,

NaHCONaHCO33,, pancreatic amylasepancreatic amylase, , lipaselipase, , trypsintrypsin and and pancreatic nucleasepancreatic nuclease..

Secretes Secretes pancreatic juicepancreatic juice for further digestion for further digestion of starch, lipid droplets, proteins and nucleic of starch, lipid droplets, proteins and nucleic acids, which is delivered to the duodenum via the acids, which is delivered to the duodenum via the pancreatic duct.pancreatic duct.

NeutralizesNeutralizes acid chyme by producing acid chyme by producing NaHCONaHCO33..

Secretes enzymes for chemical digestion of all Secretes enzymes for chemical digestion of all biological molecules. biological molecules.

Small IntestineSmall Intestine Up to seven meters in length and 2.5cm in Up to seven meters in length and 2.5cm in

diameter.diameter. Divided into three sections; the first 30 cm Divided into three sections; the first 30 cm

is the is the duodenumduodenum.. Walls of the small intestine are covered in Walls of the small intestine are covered in

villivilli (small finger-like projections), smooth (small finger-like projections), smooth muscle fibers, pits containing muscle fibers, pits containing intestinal intestinal glandsglands secreting enzymes, secreting enzymes, goblet cellsgoblet cells secreting mucus, epithelial cells contain secreting mucus, epithelial cells contain microvillimicrovilli, and many , and many foldsfolds which which increase the surface area for chemical increase the surface area for chemical digestion and absorption.digestion and absorption.

Small IntestineSmall Intestine

Small IntestineSmall Intestine Produces Produces intestinal juiceintestinal juice containing containing

HH22O, mucus, O, mucus, maltasemaltase, , peptidasepeptidase andand intestinal nucleaseintestinal nuclease..

Provides Provides optimaloptimal pH 8-9pH 8-9 for for intestinal nuclease, peptidase and intestinal nuclease, peptidase and maltase, pancreatic amylase and maltase, pancreatic amylase and nuclease, lipase, trypsin. nuclease, lipase, trypsin.

Complete digestion of carbs, Complete digestion of carbs, proteins, nucleic acids, and lipids.proteins, nucleic acids, and lipids.

Enzymes at workEnzymes at workHH22OO

starch maltosestarch maltosepancreatic amylasespancreatic amylases

HH22OO

maltose glucosemaltose glucose maltasemaltase

HH22OO

proteins peptidesproteins peptides trypsintrypsin

More enzymesMore enzymesH2OH2O

peptides amino acidspeptides amino acids peptidasepeptidase H2OH2Onucleic acids nucleotidesnucleic acids nucleotides pancreatic & intestinal pancreatic & intestinal

nucleasesnucleases H2OH2Olipid droplets glycerol & lipid droplets glycerol & lipaselipase fatty acids fatty acids

Small Intestine Cont.Small Intestine Cont. Absorption of all nutrients/monomers into Absorption of all nutrients/monomers into

the villi.the villi. Receives acid chyme from stomach, Receives acid chyme from stomach,

secretions from the gall bladder, and secretions from the gall bladder, and pancreas.pancreas.

Undigested material is transported to the Undigested material is transported to the large intestine by large intestine by peristalsisperistalsis..

Long length allows time for enzymatic Long length allows time for enzymatic reactions to occur and increases reactions to occur and increases absorptive area for monomers/nutrients.absorptive area for monomers/nutrients.

Increased surface area of intestinal cells Increased surface area of intestinal cells by by microvillimicrovilli further increases absorption further increases absorption of monomers/nutrients. of monomers/nutrients.

AppendixAppendix Worm-like projection Worm-like projection

arising from the arising from the junction of the small junction of the small and large intestine.and large intestine.

Vestigial Vestigial (underdeveloped) (underdeveloped) organ with no known organ with no known functions in humans, functions in humans, however, it may have a however, it may have a role in the lymphatic role in the lymphatic system. system.

Large Intestine (colon)Large Intestine (colon) Up to 1.5 meters long and 7.5 centimeters Up to 1.5 meters long and 7.5 centimeters

wide.wide. Contains a series of pouches that have a Contains a series of pouches that have a

puckered appearance and also contains puckered appearance and also contains smooth muscle fibers for smooth muscle fibers for peristalsisperistalsis..

Houses anaerobic bacteria called Houses anaerobic bacteria called E. coliE. coli, , which synthesizes vitamins Bwhich synthesizes vitamins B,, and K, and K, growth factors, amino acids, and further growth factors, amino acids, and further breaks down undigested materials by breaks down undigested materials by fermentation.fermentation.

Large IntestineLarge Intestine

Large Intestine (colon)Large Intestine (colon) Absorption of HAbsorption of H22O from feces and O from feces and

salts, e.g. high [solute] of the feces salts, e.g. high [solute] of the feces will cause watery feces/diarrhea will cause watery feces/diarrhea (recall B10, hypertonic).(recall B10, hypertonic).

Secretes mucus for lubrication. Secretes mucus for lubrication.

RectumRectum Last 20 cm of large Last 20 cm of large

intestine (colon),intestine (colon),controlled by a controlled by a sphincter muscle.sphincter muscle.

Compacts/stores Compacts/stores feces and opens feces and opens into anus. into anus.

AnusAnus Opening of rectum, surrounded by Opening of rectum, surrounded by

sphincter muscles.sphincter muscles.

Controls opening of rectum.Controls opening of rectum.

Elimination of feces (defecation) by Elimination of feces (defecation) by relaxing sphincter muscles. relaxing sphincter muscles.

Swallowing and PeristalsisSwallowing and Peristalsis

SwallowingSwallowing is a is a reflex actionreflex action (automatic(automatic)) triggered when the triggered when the bolusbolus is pushed upwards by the is pushed upwards by the tongue against the soft palate and tongue against the soft palate and back towards the back towards the pharynxpharynx..

The The larynxlarynx elevates, bends the elevates, bends the epiglottisepiglottis, which covers the , which covers the glottisglottis in the trachea, to prevent food from in the trachea, to prevent food from entering the lungs.entering the lungs.

PeristalsisPeristalsis PeristalsisPeristalsis is the alternating is the alternating

contractingcontracting and and relaxing relaxing of of smooth smooth musclesmuscles. It occurs in the . It occurs in the esophagusesophagus moving the bolus to the stomach and moving the bolus to the stomach and provides movement of chyme in the provides movement of chyme in the small intestinesmall intestine and undigested and undigested material in the material in the large intestinelarge intestine..

Pancreas and InsulinPancreas and Insulin An accessory organ of digestion An accessory organ of digestion

(exocrine gland), which produces (exocrine gland), which produces pancreatic juicepancreatic juice (H2O, NaHCO(H2O, NaHCO33, , pancreatic amylase, lipase, pancreatic amylase, lipase, trypsin, and pancreatic nuclease)trypsin, and pancreatic nuclease) and empties into the duodenum via and empties into the duodenum via pancreatic duct.pancreatic duct.

InsulinInsulin Also produces a Also produces a hormonehormone called called insulininsulin (from the (from the

islets of Langerhans) (endocrine gland) which is islets of Langerhans) (endocrine gland) which is secreted into the bloodstream and has the secreted into the bloodstream and has the following effects when the concentration of following effects when the concentration of glucose in the blood/blood glucose is highglucose in the blood/blood glucose is high::

i)i) StimulatesStimulates cells permeability to Ccells permeability to C66HH1212OO66 ; ;stimulates liver, fat, and muscle cells to stimulates liver, fat, and muscle cells to metabolize Cmetabolize C66HH1212OO66..

ii) ii) StimulatesStimulates liver and muscle cells to store excess liver and muscle cells to store excess CC66HH1212OO66 as as glycogenglycogen..

iii) iii) PromotesPromotes the buildup of fats and proteins,the buildup of fats and proteins,and inhibits their use as an energy source.and inhibits their use as an energy source.

Six Major Functions of the Six Major Functions of the LiverLiver

Digestive SystemDigestive System ProducesProduces bilebile (which is stored in the gall bladder) to (which is stored in the gall bladder) to

emulsify lipids.emulsify lipids. StoresStores excess glucose as excess glucose as glycogenglycogen to maintain to maintain

glucose levels.glucose levels.Circulatory SystemCirculatory System ProducesProduces blood proteins/plasma proteinsblood proteins/plasma proteins from the from the

amino acids (e.g. albumin, gamma-globulin, amino acids (e.g. albumin, gamma-globulin, fibrinogen).fibrinogen).

DetoxifiesDetoxifies blood by removing alcohol, drugs, and blood by removing alcohol, drugs, and other poisonous materials.other poisonous materials.

ConvertsConverts Hb from worn out RBCs for the production Hb from worn out RBCs for the production of bile.of bile.

Functions of Liver (5 and 6)Functions of Liver (5 and 6)Excretory SystemExcretory System ProducesProduces ureaurea from the breakdown from the breakdown

of amino acids and excretes it as a N-of amino acids and excretes it as a N-waste.waste.

MetabolizesMetabolizes ammonia (N-waste) to ammonia (N-waste) to urea and excretes it in the urine.urea and excretes it in the urine.

C2 – Enzymes and Digestive C2 – Enzymes and Digestive Reactions They PromoteReactions They Promote

IntroductionIntroduction Enzymes are Enzymes are hydrolytichydrolytic, that is, adding , that is, adding

HH22OO breaks bonds. breaks bonds.1.) Carbohydrates1.) Carbohydrates (a) (a) Salivary amylaseSalivary amylase, produced in the , produced in the

salivary glands; salivary glands; optimaloptimal pH 7pH 7.. (b)(b) Pancreatic amylasePancreatic amylase,, produced in the produced in the

pancreas; pancreas; optimaloptimal pH 8-9pH 8-9.. (c) (c) MaltaseMaltase, produced in the small intestine , produced in the small intestine

(intestinal glands); (intestinal glands); optimaloptimal pH 8-9pH 8-9. .

Enzymes cont.Enzymes cont.2.) Proteins2.) Proteins (a) (a) PepsinPepsin, produced in the stomach , produced in the stomach

(gastric glands); (gastric glands); optimaloptimal pH 2-3pH 2-3.. (b) (b) TrypsinTrypsin, produced in the pancreas; , produced in the pancreas;

optimaloptimal pH 8-9pH 8-9.. (c) (c) PeptidasePeptidase, produced in the small , produced in the small

intestine (intestinal glands); intestine (intestinal glands); optimaloptimal pH 8-pH 8-99..

NOTENOTE: : pepsin, inactive pepsinogen and pepsin, inactive pepsinogen and trypsin are examples of enzymes called trypsin are examples of enzymes called proteasesproteases..

Enzymes cont.Enzymes cont.3.) Lipids3.) Lipids LipaseLipase, produced in the pancreas; , produced in the pancreas; optimaloptimal

pH 8-9pH 8-9..4.) Nucleic acids/nucleotides4.) Nucleic acids/nucleotides (a) (a) PancreaticPancreatic nucleasenuclease, produced in the , produced in the

pancreas; pancreas; optimaloptimal pH 8-9pH 8-9.. (b) (b) Intestinal nucleaseIntestinal nuclease, produced in the , produced in the

small intestine (intestinal glands); small intestine (intestinal glands); optimal optimal pH 8-9pH 8-9..

C2 – Components of C2 – Components of Digestive SecretionsDigestive Secretions

NOTE: * = Enzyme.NOTE: * = Enzyme.SalivaSaliva Produced by cells of three pairs of salivary Produced by cells of three pairs of salivary

glands located in the head, secreted into glands located in the head, secreted into ducts which then enters the mouth.ducts which then enters the mouth.

Composed of:Composed of: H2OH2O MucusMucus BuffersBuffers Salivary amylase*Salivary amylase*

Gastric JuiceGastric Juice

Produced by gastric glands and Produced by gastric glands and mucus cells in the stomach.mucus cells in the stomach.

Composed of:Composed of: HH22OO MucusMucus HClHCl Pepsin*Pepsin*

Pancreatic JuicePancreatic Juice

Produced by cells of the pancreas, travels Produced by cells of the pancreas, travels to the pancreatic duct and then to the to the pancreatic duct and then to the duodenum.duodenum.

Composed of:Composed of: HH22OO NaHCONaHCO33 Pancreatic amylase*Pancreatic amylase* Lipase*Lipase* Trypsin*Trypsin* Pancreatic nuclease*Pancreatic nuclease*

Intestinal JuiceIntestinal Juice

Produced by intestinal glands and Produced by intestinal glands and mucus cells in the small intestine.mucus cells in the small intestine.

Composed of:Composed of: HH22OO MucusMucus Peptidase*Peptidase* Maltase*Maltase* Intestinal nuclease*Intestinal nuclease*

Summary of Enzymes and Summary of Enzymes and Chemicals/MoleculesChemicals/Molecules

1.)1.) Salivary amylaseSalivary amylase (mouth); breaks (mouth); breaks down starch + Hdown starch + H22O O maltose. maltose.

2.) 2.) Pancreatic amylasePancreatic amylase (pancreas to (pancreas to the duodenum); breaks down starch the duodenum); breaks down starch + H+ H22O O maltose. maltose.

3.) 3.) MaltasMaltasee (small intestine); breaks (small intestine); breaks down maltose + Hdown maltose + H22O O glucose. glucose.

Carbohydrates

ProteinsProteins 1.) 1.) PepsinPepsin (stomach); breaks down (stomach); breaks down

proteins + Hproteins + H22O O peptides. peptides.

2.) 2.) TrypsinTrypsin (pancreas to the duodenum); (pancreas to the duodenum); breaks down protein + Hbreaks down protein + H22O O peptides. peptides.

3.) 3.) PeptidasePeptidase (small intestine); breaks (small intestine); breaks down peptides + Hdown peptides + H22O O amino acids. amino acids.

Nucleic AcidsNucleic Acids 1.) 1.) Pancreatic nucleasePancreatic nuclease (pancreas); (pancreas);

breaks down nucleic acids + Hbreaks down nucleic acids + H22O O nucleotides.nucleotides.

2.) 2.) Intestinal nucleaseIntestinal nuclease (small (small intestine); breaks down nucleic acids intestine); breaks down nucleic acids + H+ H22O O nucleotides. nucleotides.

LipidsLipids 1.) 1.) LipaseLipase (pancreas to the (pancreas to the

duodenum); breaks down duodenum); breaks down lipidlipid dropletsdroplets + H + H22O O glycerol + fatty glycerol + fatty acids.acids.

BileBile (Produced in the liver, stored in the gall (Produced in the liver, stored in the gall

bladder, empties into the duodenum via ducts.)bladder, empties into the duodenum via ducts.) NOTNOT an enzyme; (a complex fluid containing an enzyme; (a complex fluid containing

HH22O, electrolytes, bile acids, cholesterol, O, electrolytes, bile acids, cholesterol, phospholipids and bilirubin.)phospholipids and bilirubin.)

EmulsifiesEmulsifies fats ( fats (physical breakdownphysical breakdown) into ) into fat/lipid droplets, which increases the surface fat/lipid droplets, which increases the surface area for chemical digestion by lipase.area for chemical digestion by lipase.

NaHCONaHCO33 ( Sodium ( Sodium Bicarbonate)Bicarbonate)

Produced in the pancreas, empties Produced in the pancreas, empties into duodenum via ducts.into duodenum via ducts.

NeutralizesNeutralizes acid chyme from the acid chyme from the stomach.stomach.

HCl (Hydrochloric Acid)HCl (Hydrochloric Acid) Produced in the stomach.Produced in the stomach.

Converts Converts pepsinogen pepsinogen (inactive)(inactive) to to pepsinpepsin (active).(active).

Kills bacteria and micro-organisms.Kills bacteria and micro-organisms.

HH22O (water….in case you O (water….in case you forgot)forgot)

Acts as a solvent.Acts as a solvent.

Hydrolyzes enzymes.Hydrolyzes enzymes.

Lubricates (aids in movement).Lubricates (aids in movement).

MucusMucus Produced in goblets cells of the Produced in goblets cells of the

stomach and cells of small and large stomach and cells of small and large intestine.intestine.

Lubricates the digestive tract.Lubricates the digestive tract.

Protection from acid chyme in stomach Protection from acid chyme in stomach and small and large intestine.and small and large intestine.

Cross-section of a Villus:Cross-section of a Villus: (See following diagram)(See following diagram)

Villus:Villus: ‘‘Finger-like’ projections found on the Finger-like’ projections found on the

inner wall of the inner wall of the small intestinesmall intestine and extend into the intestinal lumen. and extend into the intestinal lumen.

Villi (plural) increase the surface area Villi (plural) increase the surface area for enzymatic reactions and for enzymatic reactions and absorption of monomers/nutrients in absorption of monomers/nutrients in the small intestine. the small intestine.

NOTE:NOTE: The following are examples of how The following are examples of how structuresstructures of the of the small intestinesmall intestine are are relatedrelated to its function.to its function.

The The numerous villinumerous villi increase the surface increase the surface area for absorption of all nutrients.area for absorption of all nutrients.

The inside of each villus contains a The inside of each villus contains a capillary bedcapillary bed to absorb nutrients. to absorb nutrients.

The inside of each villus contains a The inside of each villus contains a lacteallacteal to absorb glycerol and fatty acids.to absorb glycerol and fatty acids.

More examplesMore examples The small intestine also contains The small intestine also contains microvillimicrovilli

(“brush border”). They are located on (“brush border”). They are located on epithelial cellsepithelial cells. This also increases the . This also increases the surface area for absorption of surface area for absorption of monomers/nutrients.monomers/nutrients.

Epithelial cellsEpithelial cells are thin, moist and warm are thin, moist and warm which speeds up diffusion/absorption. which speeds up diffusion/absorption.

Numerous Numerous mitochondriamitochondria in epithelial cells in epithelial cells provide ATP for active transport of nutrients.provide ATP for active transport of nutrients.

And more….And more…. The walls of the small intestine contain The walls of the small intestine contain

smooth muscle cellssmooth muscle cells that provide that provide movement of chyme throughout the entire movement of chyme throughout the entire length. length.

This movement is known as This movement is known as peristalsisperistalsis. . PeristalsisPeristalsis also increases the surface area also increases the surface area of the food. of the food.

The walls of the small intestine contain The walls of the small intestine contain goblet cellsgoblet cells that produce that produce mucusmucus, which , which aids in lubrication and movement. aids in lubrication and movement.

A few more examplesA few more examples The walls of the small intestine also The walls of the small intestine also

contain many contain many foldsfolds, which increase , which increase the surfaces area for absorption of the surfaces area for absorption of monomers/nutrients.monomers/nutrients.

The The lengthlength of the small intestine of the small intestine increases the surface are for increases the surface are for absorption and chemical digestion of absorption and chemical digestion of food.food.

Much of absorption includes Much of absorption includes active active transporttransport, but , but passive transportpassive transport also also occurs.occurs.

Each villus (and therefore microvillus) Each villus (and therefore microvillus) contains:contains: Epithelial cellEpithelial cellss.. Mucus (goblet cells).Mucus (goblet cells). Lacteal (lymphatic vessel).Lacteal (lymphatic vessel). Capillary bed/network.Capillary bed/network.

They allow for absorption of HThey allow for absorption of H22O, ions, O, ions, minerals, and minerals, and monomersmonomers..

Processes of monomers and Processes of monomers and water entering intestinal water entering intestinal

epithelial cellsepithelial cellsLipidsLipids:: GlycerolGlycerol and and fatty acidfatty acid monomers monomers

diffusediffuse across the epithelial cells and across the epithelial cells and then then diffusediffuse into the into the lacteal vessellacteal vessel. .

These monomers will form These monomers will form triglycerides as they enter the triglycerides as they enter the lymphatic systemlymphatic system enters heart enters heart and general circulation.and general circulation.

Carbs and ProteinsCarbs and Proteins GlucoseGlucose and and amino acidamino acid monomers move by monomers move by

active transportactive transport into into epithelial cellsepithelial cells, and , and then then diffusediffuse into into capillary bedcapillary bed//networknetwork. .

Glucose and amino acid monomers then enter Glucose and amino acid monomers then enter the bloodstream to the liver via the bloodstream to the liver via hepatic hepatic portal veinportal vein, , exits liver viaexits liver via hepatic veinhepatic vein to to the heart, which then pumps Cthe heart, which then pumps C66HH1212OO66 and and amino acids throughout the body.amino acids throughout the body.

Now the liver can store excess CNow the liver can store excess C66HH1212OO66 as as glycogenglycogen and use the amino acids to make and use the amino acids to make proteins.proteins.

Nucleic Acids:Nucleic Acids:

NucleotidesNucleotides diffusediffuse into into epithelial epithelial cellscells, and then , and then diffusediffuse into into capillarycapillary bed/networkbed/network enter the enter the bloodstream bloodstream liver via liver via hepatic hepatic portal veinportal vein hepatic veinhepatic vein heart heart body cells. body cells.

HH22O:O:

Enters Enters epithelial cellsepithelial cells by by osmosisosmosis and into the and into the capillary bed/networkcapillary bed/network enters bloodstream. enters bloodstream.