The digestive system is a series of tubes that transports food from the mouth to the anus. It includes organs like the mouth, esophagus, stomach, and intestines. Accessory organs like the liver, gallbladder and pancreas also play important roles in digestion. As food moves through the tubes, it is broken down mechanically and chemically. Enzymes and hormones help regulate digestion. The nervous and endocrine systems control movement and secretions to efficiently break down food into nutrients that can be absorbed and used by the body.

1. Digestiee
System

2. Objectiee: Digeetie Syetem
• Understand the digestive system is a series of
tubes with diferent epithelia and cells =
mouth to the anus
• Describe the 4 layers in the tubes (mucosa,
submucosa, muscularis externa, adventitia or
serosa
• Describe the structure and functions of each
organ: mouth, esophagus, stomach,
duodenum, small intestine, and large
intestine.
• Describe the structure and function of the
accessory organs (salivary, pancreas, liver,
and gallbladder)

3. • Underetand and deecribe the control mechanieme:
– nerioue eyetem (intrineic and extrineic) and
– hormonal – paracrine and endocrine mechanieme
• Deecribe the eecretory celle in the tubee and
acceeeory glande
• Underetand why motlity (iia muecle contracton) of
the tubee ie important
• Explain where and how the proceeeee of digeeton,
abeorpton, and excreton occur
Objectiee: Digeetie Syetem

4. The Digeetie Syetem
• The ENTERIC (GI) eyetem
– Mouth to anue
– Long tube with diferent
etructuree and functone
– Acceeeory glande
• ealiiary glande
• pancreae
• liier
• gallbladder

5. The Plan
• Introducton –
– 1. General concepte
• Follow food ae it moiee thru the digeetie tract
and diecuee the anatomy and phyeiology or each
area
– 2. Mouth thru eeophague
– 3. Stomach
– 4. Duodenum and acceeeory glande – liier, gall
bladder and pancreae
– 5. Small inteetne and large inteetne

6. Digeeton
• Phaeee Include
1. Ingeeton
2. Moiement
3. Mechanical and Chemical Digeeton
4. Abeorpton
5. Eliminaton

7. Digeetie Syetem Organizaton
• Gastrointestnale (Gl)e tract
– Tubee withine ae tube
– Directe link/pathe betweene organs
– Structures
• Mouth
• Pharynx
• Esophagus
• Stomach
• Smalle intestne
• Largee Intestne
• Rectum
7

8. Digeeton
• Typee
– Mechanical (phyeical)
• Chew
• Tear
• Grind
• Maeh
• Mix
– Chemical
• Enzymatc reactone to improie digeeton of
– Carbohydratee
– Proteine
– Lipide

9. Thee Gastrointestnale Tract
Fore betere ore fore worse,re thee gute aree exquisitelye designede toe acquiree
eierye caloriee oute ofe eierye meale

16. Phyeiological Proceeeee of the
Digeetie Tract - eimplifed
1.
2.
3.
4.

18. What doee the digeetie eyetem do?
• First 2 functions you think of
• What happens when you frst
smell fresh apple pie?
• What does your stomach do?
• How long is the intestine?
• Does your GI tract move;
make noise?
• Does your nervous system
control the GI tract?
• Why do you eat food?

19. What happene when you fret smell freeh bread?
• The body gets ready for digestion:
• Salivary glands release
– Serous and mucous fuid
– Amylase – breaks down carbohydrates
– Lipase – lipid digestion
• Stomach begins to churn (muscles) and
acid & enzymes are released
• Pancreas and gall bladder activate
• These are controlled by the CNS – the
extrinsic nervous system.

20. What happene when you fret taste freeh bread?
(food in your mouth)
• Saliiary glande releaee
– Seroue and mucoue fuid
– Digeeton begine
– Amylaee – breake down
carbohydratee
– Lipaee for lipid digeeton
• Chewing (maetcaton) and
mixing of food with tongue
• Stomach mueclee contract, acid
and enzymee releaeed
• Pancreae and gall bladder
eecrete

21. Mouth
• Teeth mechanically
break down food into
emall piecee. Tongue
mixee food with ealiia
(containe amylaee,
which helpe break down
etarch).
• Epiglote ie a fap-like
etructure at the back of
the throat that cloeee
oier the trachea
preientng food from
entering it. It ie located
in the Pharynx.

22. Saliiary functone and ite regulaton
• Saliia ie the mixed glandular eecreton which
conetantly bathee the teeth and the oral mucoea
• Firet eecreton encounter the food
• It ie iital for oral health
• It ie conettuted by the eecretone of the three paired
major ealiiary glande;
• Parotd, eub mandibular and eublingual
• It aleo containe the eecretone of the minor ealiiary
glande

23. Structure of ealiiary Glande

24. Parotd gland
• Parotd Ie large accounte for 50% eec. of
ealiia (when etmulated)
• Situated in front of ear behind the ramue
of mandible
• Gland drain in to oral caiity oppoeite to
eecond molar tooth
• Secretone are baeically eeroue

25. Structure of eub mandibular and eub lingual gland

26. Submandibular and eub lingual gland
• Thee submandibulare gland ie iariable in eize being
about half the eize of the parotd
• liee aboie the mylohyoid in the foor of the mouth.
• It opene into the foor of the mouth underneath the
anterior part of the tongue
• Thee sublinguale ie the emalleet of the paired major
ealiiary glande,
• It ie eituated in the foor of the mouth beneath the
eublingual folde of mucoue membrane.

27. Structure of ealiiary gland

28. Compoeiton of ealiia
• Water 99.55% eolid 0.45%
• pH 7.04
• Na, K, Ca, Mg, Cl, HCO3- and phoephate
• Organic eubetancee includee
• IgA, Lyeozymee, albumin, glucoee, lactate, urea
and ammonia etc.
• Normal ealiiary fow ratee are 0.3-0.4 ml/min
when unetmulated and 1-1.5 litre/day when
etmulated
• Approximately 0.5 – 0.6 litree of ealiia ie
eecreted perday

29. Functone of ealiia
• Initate the digeeton of etarch
• Protecte oral caiity (IgA and lyeozymee)
• Proiide lubricaton for food to make bolue
• Facilitate the taete
• When ealiiary fow ie reduced, dryneee of the
mouth occure and informaton from
oemoreceptore are tranelated to increaee the
water intake
• Helpe in epeaking, ewallowing, chewing
• Bufer the gaetric eecretone refux in to the
oeeophague

31. Control of ealiiary eecreton
Baeically controlled by paraeympathetc, eympathetc etmulaton caueee
proteinaceoue eecreton without afectng the iolume

32. Xeroetomia (ealiiary foww 0.2 ml/min)
• The preeence of ealiia ie iital to the maintenance of healthy
hard (teeth) and eof (mucoea) oral teeuee.
• Seiere reducton of ealiiary output reeulte in a rapid
deterioraton in oral health
• Patente eufering from dry mouth can experience difculty
with eatng, ewallowing, epeech, the wearing of denturee,
trauma to and ulceraton of the oral mucoea, taete alteraton,
poor oral hygiene, a burning eeneaton of the mucoea,
• oral infectone including Candida and rapidly progreeeing
dental cariee
• Afer radio therapy, old age and multdrug therapy

33. Eeophague
• Approximately 20 cm long.
• Functone include:
1. Secrete mucue
2. Moiee food from the throat to the
etomach ueing muecle moiement
called perietaleie
• If acid from the etomach gete in
here that’e heartburn.

34. Stomach
• J-ehaped muecular bag that etoree the food you
eat, breake it down into tny piecee.
• Mixee food with Digeetie Juicee that contain
enzymee to break down Proteinse ande Lipids.
• Acid (HCl) in the etomach Kille Bacteria.
• Food found in the etomach ie called Chyme.

35. What happene to the bread in the etomach?
• Stomach functone:
– Storage of food
– Mixing iia muecle contractone
– Releaee of H+
& Cl-
and pH lowere
• kills bacteria
• Degradee foode = chyme
– Celle releaee pepeinogen – a zymogen
– Pepeinogen conierted to pepein in low
pH – cleaiee proteine
– Digeeton contnuee iia
• Acid and pepein
• Amylaee, lipaee
etomach

36. Small Inteetne
• Small inteetnee are roughly 7 metere long
• Lining of inteetne walle hae fnger-like
projectone called iilli, to increaee eurface
area.
• The iilli are coiered in microiilli which
further increaeee eurface area for
abeorpton.
Crash Course Review

37. Small Inteetne
• Nutriente from the food paee into the
bloodetream through the emall
inteetne walle.
• Abeorbe:
– 80% ingeeted water
– Vitamine
– Minerale
– Carbohydratee
– Proteine
– Lipide
• Secretee digeetie enzymee

38. What happene to bread (chyme) in the emall
inteetne
• Acidic Fluide fow into the emall
inteetne:
– digeetie enzymee and bicarbonate
(HCO3
-
) added from Pancreae
– Liier makee bile for lipid abeorpton
– Water added and reabeorbed
• Digeeton acceleratee and pH
neutralized to pH ~ 7
• Abeorpton of building blocke
through enterocytee to the liier
iia the portal blood eyetem
• Undigeeted material remaine
emall
inteetne

40. Large Inteetne
• About 1.5 metere long
• Accepte what emall inteetnee don’t
abeorb
• Rectum (ehort term etorage which
holde fecee before it ie expelled).

41. Large Inteetne
• Functone
– Bacterial digeeton
• Ferment carbohydratee
– Absorbs more water
– Concentrate wastes

42. What happene to chyme in the large
inteetne?
• Dehydraton of indigeetble
material
• Compacton of indigeetble
material
• Eliminaton of undigeeted
material
large
inteetne

43. Acceeeory Organe The Glande
• Not part of the path
of food, but play a
critcal role.
• Include: Liier, gall
bladder, and
pancreae

44. Liier
• Directly afecte digeeton by producing
bile
– Bile helpe digeet fat
• fltere out toxine and waete including
druge and alcohol and poieone.

46. Gall Bladder
• Storee bile from the liier, releaeee it
into the emall inteetne.
• Faty diete can cauee galletonee

47. Pancreae
• Producee digeetie
enzymee to digeet fate,
carbohydratee and
proteine
• Regulatee blood eugar
by producing ineulin
Web Page Reinforcement Video

48. • Retroperitoneal
– Poeterior to the parietal
peritoneum
– Embedded in connectie
teeue
• duodenum
• pancreae
• parte of the lg inteetne
• Intraperitoneal (withe in)
– Bordered by a eingle cell -
meeothelium
Peritoneal caiity
Omentume (from ‘epipleein’ Gk.) meaning to foat on; Meeentery ie a double layer of peritoneum
Fig 24.2
Concepts and
characteristics

49. Meeentery
- Supporte 20’ of emall inteetne – hold in place yet allowe moiement
- Allowe blood ieeeele and nerioue eyetem to enter and leaie

50. Deeign of the tube: Structure
Control mechanieme: Neural
- intrineic = Enterice NSe
- extrineic = CNS
Control mechanieme: Hormonal
- eignaling moleculee
- eecretone
- motlity of mueclee
Digeeton and Abeorpton
General concepte for the
Digeetie Syetem
food
H2O, ione
H2O,
ione
‘Inside tube is outside

51. Copyright © The McGraw-Hill Companiee, Inc. Permieeion required for reproducton or dieplay.
#1e Mucosa
Epithelium
Laminae propria
Muscularis
mucosae
#2e Submucosa
Submucosal
neriee plexus
#3e Muscularis
Innere circulare layer
Myenteric
neriee plexus
Outere longitudinal
layer
#4e Serosae ore Adientta
Vein,re artery,r
lymphe iessel
(withine mesentery)
(a)e Tunics
Lumen
Deeign of the Four Layere in the GI Syetem fg 26.2
change
s

52. #3 Muecularie
externa
meeothelium
Lamina propria
#2 Submucoea
Muecularie mucoea
Diferent
eurfacee
#4 Seroea
4 layere – diferent diagram
Submucoeal gland
From ealiiary glande,
pancreae or liier
meeentery
#1 Mucoea – epithelium, lamina propria, muecularie mucoea

53. Perietaleie, eegmentaton, and…
• Peristalsis – proceee that moiee
chyme forward – in 1 directon
• Segmentation – irregular
contractone forcing chyme in both
directone NO NET PROGRESS
– Paeeee nutriente back and forth to
optmize abeorpton
• Interstitial cells of Cajal – motor
neurone in the myenteric plexue
– Intrineic control
– Slow, conetant contractone
Fig 24.4
LUMEN
Ganglia!

54. Control Mechanieme
• Neuronal (neurocrine)
– A. Short or Intrinsic Reflex– neurone within the GI
eyetem (ENS = enteric nerioue eyetem)
• Signal from the lumen to the ENS and back
• The only organ eyetem capable of ueing a refex reeponee
without the CNS
– B. Long or Extrinsic Reflex– neurone in the CNS –
(outeide the ENS)
• Signal from the lumen to the CNS and back to the GI tract
• Hormonal – enteroendocrine celle in the GI
epithelium and endocrine glande
– Paracrine
– Endocrine

55. Neural controle of the GI Syetem
Extrinsice = CNS Intrinsice = ENS
More neurone in the gut than in the epinal cord

56. Control mechanieme : #1a. Neurale –e Intrinsic
Enterice NSe =e shorte reflex
• Seneory neurone receiie eignale from the lumen. They contain:
• Mechanoreceptors - for etretch
• Chemoreceptors - pH, oemolarity, food breakdown producte
• Signale go to intrineic Paraeympathetc neurone – ’rest and digest’
• Cauee cell/gland eecretone and muecle contractone
• Sympathetc fbere – ehut enteric eyetem down
• Moetly inhibit paraeympathetc neurone
• Control blood fow
• Interneurone important for local refexee
• Motor neurone driie emooth muecle
PNS: neurone intrineic to the digeetie eyetem (GI) =
Enterice neriouse system - ‘thee litlee brain’e

57. Control mechanieme : #1b. Neurale –e Extrinsice
CNSe e =e e longe reflex
• Input from 5 eeneee in CNS eignal GI eyetem
• Starte gland and cell eecretone in mouth and etomach
• Starte muecle contractone in etomach
• OR Signale in GI are eent to the CNS
– Seneory informaton(from GI) =aferent to CNS and reeponee =
eferent back to GI eyetem =e REFLEX
– CNS eende eignale to enteric neurone
• controle GI gland and cell eecretone
• controle GI muecle contractone– indirectly through
– CNS infuencee can be modifed by autonomic NS
• Paraeympathetc and eympathetc
• Emotone (CNS) efect enteric eyetem
• Buterfiee when fying 1et
tme
• Talking in front of a claee – mouth ie dry
• Really ecared – urinaton or diarrhea

58. The Enteric Nerioue Syetem
•e Myenterice
plexus
(Auerbach’s)
Intrinsice iersuse Extrinsice Controls
•e Submucosale
plexus
(Meissner’s)
Intrinsice Neriouse system
E
x
t
r
i
n
s
i
c
e
N
S
signals

59. Signaling mechanieme
• 1.e Autocrine – eignal
goee back to cell of origin
• 2.e Paracrine – eignal goee
ehort dietance to nearby
celle
3.e Endocrinee mechanisms
lumen
Blood ieeeel
REVIEW
Enteroendocrinee cell

60. Control mechanieme: #2. Hormonal
• Hormonal mechanieme
– Enteroendocrine celle ‘ taete’ chemicale in the lumen
– Enteroendocrine releaee peptde hormonee
• Releaeed into CT and then blood ieeeele
– Functon iia paracrine & endocrine mechanieme
• Controle eecreton of gland celle (etomach, pancreae, etc.)
• Controle - enhance or inhibit muecle contracton
• Infuence intrineic and extrineic nerioue eyetem inpute
– Endocrine hormonee, eg. ineulin, glucagon, etc

61. Glande -
• Exocrine glande – releaee
of producte through duct
eyeteme
• Endocrine glande – releaee
of producte into the
circulaton (blood ieeeele) to
circulate to target celle
– enteroendocrine celle
eecrete peptdee
– GI ie the largeet endocrine
gland –
Review

62. Secretions: cells & glands
• e Enteroendocrinee cells (etomach, duodenum …)
– Reepond to eiente in the lumen (mechanical or chemical) =
‘taste buds’ of the gut
– Secrete peptdee – paracrine & endocrine (into the
circulaton)
• Example: G celle releaee gaetrin – a peptde
• Gaetrin – to near celle and entere into blood ieeeele and controle
– Cell eecreton
– Muecle motlity
– Some aleo reepond to CNS neural inpute
• Exocrinee Glands (gland celle eecrete into ducte)
– Saliiary glande make H20 and enzymee
– Liier makee bile
– Pancreae makee digeetie enzymee and bicarbonate (HCO3
-
)
– Duodenal glande make bicarbonate (HCO3
-
) to neutralize HCl

63. Motility = muecle moiement
• Skeletal muecle = ioluntary control from CNS
– Tongue and pharynx
– Upper 2/3 eeophague
– Anal region ephincter
• Smoothe musclee = inioluntary control
– Intrinsice control from enteric paraeympathetc neurone on:
• Muecularie mucoea: emooth muecle
• Muecularie externa: inner circular and outer longitudinal bande
– Extrinsice control from the CNS neurone
• CNS neurone etmulate ENS paraeympathetc neurone
• Control mueclee in the enteric nerioue eyetem
• Modifed by eympathetc neurone

64. Smooth Muecle Motlity
• Neceeeary functone:
– Mixing of food, acid and enzymee in the etomach
– Slow releaee of chyme into the emall inteetne
– Controle moiement through emall inteetne and thue rate of digeeton
– Moiement and remoial of indigeetble material
• Structure – emooth muecle celle
– Cloeely poeitoned elongated celle w/o direct eynapeee
– Gap junctone allow eynchronoue contractone of many celle
• Actone
– Depolarizaton allowe Ca++
infux or releaee of intracellular Ca ++
– Contracton of emooth muecle celle
• Caueatie agente
– Releaee of neurotranemiter from ENS neurone
– Signal moleculee (hietamine, eerotonin, etc.)

65. Seneory
receptore
Stmulue (eight,
emell, etc)
1.e Musclee
contractone ore
relaxaton
2.e Exocrinee glande
secreton:e
enzymes,re
mucous,re acid,re
bicarbonate
3.e e Endocrinee
secreton:e
peptdes,re
insulin
Digestiee
systeme
Responses
Enteric nerioue eyetem
Sensorye
receptorse ofe
neuronse
Enteric neurone
(ganglia/ plexue)
(Paraeympathetc)
increaee in actiity
Stmulue:
(etretch, pH,
oemolarity,
producte of
digeeton)
Smooth
mueclee
or
eecretory
celle
Green arrowe = ehort (intrineic) refex Blue arrowe = long (extrineic) refex
(Sympathetc) decreaee
in actiity

66. Digestion, Absorption &
Elimination
• Digeston – break down of foodetufe to baeic
building blocke (aa, eugare, fate, nucleotdee)
• Absorpton – paeeage of building blocke from
inteetne iia portal eyetem to the liier
• Eliminaton – releaee of waete producte and
recoiery of fuide

68. Now it's...
QUIZ TIME!

69. On a eheet of paper, write the name of each
colored organ:
• Green:
• Red:
• Pink:
• Brown:
• Purple:
• Green:
• Yellow:

70. How’d you do?
• Green: Eeophague
• Red: Stomach
• Pink: Small Inteetne
• Brown: Large Inteetne
• Purple: Liier
• Green: Gall Bladder
• Yellow: Pancreae
Great Job!

71. Referencee and Linke
• Your Digeetie Syetem and How It Worke
– Digeetie eyetem diagram comee from thie eite
• The Real Deal on the Digeetie Syetem
• Pancreae: Introducton and Index
• Your Groee and Cool Body - Digeetie Syetem
• Laurentan Regional High School Data Baee
- youe muste knowe thee Usernamee ande Password