Mouth and esophagus ( anatomy , physiology)

1. The Digestive SystemThe Digestive System
Dr. MohanaD

2. Functions of the Digestive SystemFunctions of the Digestive System
 Ingest foodIngest food
 Break down food into nutrient moleculesBreak down food into nutrient molecules
 Absorb molecules into the bloodstreamAbsorb molecules into the bloodstream
 Rid the body of indigestible remainsRid the body of indigestible remains

4. Main Divisions of the DigestiveMain Divisions of the Digestive
SystemSystem
 Alimentary CanalAlimentary Canal
 Continuous, muscular digestive tube windingContinuous, muscular digestive tube winding
throughout the bodythroughout the body
 Digests and absorbs food particlesDigests and absorbs food particles
 Contains the following organs:Contains the following organs:
 Mouth, Pharynx, Esophagus, Stomach, Small and LargeMouth, Pharynx, Esophagus, Stomach, Small and Large
IntestinesIntestines
 Accessory Digestive OrgansAccessory Digestive Organs
 Contains the following organs:Contains the following organs:
 Teeth, Tongue, Gallbladder, Salivary Glands, Liver, andTeeth, Tongue, Gallbladder, Salivary Glands, Liver, and
PancreasPancreas

5. Digestive System DivisionsDigestive System Divisions

6. Digestive ProcessesDigestive Processes
 IngestionIngestion
 PropulsionPropulsion
 Mechanical digestionMechanical digestion
 Chemical digestionChemical digestion
 AbsorptionAbsorption
 DefecationDefecation

7. Organs of the Alimentary CanalOrgans of the Alimentary Canal
Slide 14.3Slide 14.3
• Mouth
• Pharynx
• Esophagus
• Stomach
• Small intestine
• Large intestine
• Anus

8. The MouthThe Mouth
 Initial point of entry of food into GI tractInitial point of entry of food into GI tract
 Is the first site for beginning the breakdown ofIs the first site for beginning the breakdown of
food into its constituent molecules (lipidsfood into its constituent molecules (lipids →→ fattyfatty
acidsacids, carbohydrates, carbohydrates → simple sugars→ simple sugars &&
protieinsprotieins →→ amino acidsamino acids) for absorption into the) for absorption into the
body.body.
 Consists of: lips, cheeks, tongue, teeth, salivaryConsists of: lips, cheeks, tongue, teeth, salivary
glands, palate.glands, palate.
 Lined with a thick stratified squamousLined with a thick stratified squamous
epitheliumepithelium

9. Anatomy of the MouthAnatomy of the Mouth

10. Mouth (Oral Cavity) AnatomyMouth (Oral Cavity) Anatomy
Slide 14.4Slide 14.4
• Lips (labia) – protect
the anterior opening
• Cheeks – form the
lateral walls
• Hard palate – forms
the anterior roof
• Soft palate – forms
the posterior roof
• Uvula – fleshy
projection of the
soft palate
Figure 14.2a

11. Mouth (Oral Cavity) AnatomyMouth (Oral Cavity) Anatomy
Slide 14.5Slide 14.5
• Vestibule – space
between lips externally
and teeth and gums
internally
• Oral cavity – area
contained by the teeth
• Tongue – attached at
hyoid and styloid
processes of the skull,
and by the lingual
frenulum
Figure 14.2a

12. Mouth (Oral Cavity) AnatomyMouth (Oral Cavity) Anatomy
Slide 14.6Slide 14.6
• Tonsils
•Palatine tonsils
•Lingual tonsil
Figure 14.2a

13. Processes of the MouthProcesses of the Mouth
Slide 14.7Slide 14.7
• Mastication (chewing) of food
• Mixing masticated food with saliva
• Initiation of swallowing by the tongue
• Allowing for the sense of taste

14. TongueTongue
 Muscular organMuscular organ
for manipulatingfor manipulating
and moving foodand moving food
in mouth and aidin mouth and aid
in swallowing ofin swallowing of
foods.foods.
 Contains tasteContains taste
buds -buds -
chemoreceptorschemoreceptors

15. Features and Functions of theFeatures and Functions of the
TongueTongue
 Helps grind food into aHelps grind food into a bolusbolus whichwhich
contains partially digested food and salivacontains partially digested food and saliva
 Helps form words and is a sensory organHelps form words and is a sensory organ
for tastefor taste
 Three surface features:Three surface features:
 Filiform papillae (roughness and grip)Filiform papillae (roughness and grip)
 Fungiform papillae (contains taste buds)Fungiform papillae (contains taste buds)
 Circumvallate papillae (contains taste buds)Circumvallate papillae (contains taste buds)

16. Anatomy of the TongueAnatomy of the Tongue

17. The PalateThe Palate
 Separates the mouth from the nasalSeparates the mouth from the nasal
cavity.cavity.
 Allows you to chew food while breathingAllows you to chew food while breathing
 Anterior portion is hard palate formedAnterior portion is hard palate formed
palatine process of mandible and palatinepalatine process of mandible and palatine
bones.bones.
 Posterior portion is composed of mainlyPosterior portion is composed of mainly
sk. m.sk. m.
 Uvula hangs down from soft palateUvula hangs down from soft palate

18. TeethTeeth
 Adults: 32 totalAdults: 32 total
 ( 8) incisors- blade shaped for clipping and( 8) incisors- blade shaped for clipping and
cutting foodcutting food
 (4) canines- conical with sharp ridgeline(4) canines- conical with sharp ridgeline
and pointed tip for tearing foodand pointed tip for tearing food
 ( 20) molars/premolars- flattened crowns( 20) molars/premolars- flattened crowns
for crushing and grinding foodfor crushing and grinding food
 Each tooth is embedded in a socket =Each tooth is embedded in a socket =
alveolusalveolus

19. TeethTeeth
Adults=32Adults=32
Children =20Children =20

20. Salivary Glands
 There are many minor salivary glands scattered throughout
oral mucosa and three pairs of major salivary glands
 Three pairs of major salivary glands are:
 Submandibular glands
 Sublingual glands
 Parotid glands
 They have lobular organization composed of branched
tubuloalveolar glands with connective tissue capsule and
septa that organize the glands into lobes and lobules
 Each individual acinus is also invested by a thin layer of CT
 Saliva secretion is controlled by autonomic nerves
 Sympathetic stimulation = sparse thick saliva
 Parasympathetic stimulation = copious, watery saliva

21. Salivary Gland Cells
Mucous cells are cuboidal or pyramidal
Mucous cells have a heterochromatic basal flattened
nucleus
Apical cytoplasm is pale or blue/purple
Their structure is acinar or tubular
Myoepithelial cells (Basket cells) have large processes
which form desmosomal contact with acini and ducts
cells.

22. • The Major SalivaryThe Major Salivary
GlandsGlands
– ParotidParotid
– SubmandibularSubmandibular
– SublingualSublingual
• >> 400 minor salivary400 minor salivary
glandsglands

23. Anatomy of the Salivary GlandsAnatomy of the Salivary Glands

27. Parotid GlandParotid Gland

28. Salivary FlowSalivary Flow
• 1-1.5 L/day (1 cc/min)1-1.5 L/day (1 cc/min)
 Parotid: serousParotid: serous
 SubmandibularSubmandibular: mucous & serous: mucous & serous
 Sublingual: mucousSublingual: mucous

30. FunctionsFunctions
Protection .Protection . lubricant (glycoprotein)lubricant (glycoprotein)
Buffering (Buffering (phosphate ions and bicarbonate)phosphate ions and bicarbonate)
DigestionDigestion
Antimicrobial. LAntimicrobial. Lysozyme hydrolyzes cell walls ofysozyme hydrolyzes cell walls of
some bacteriasome bacteria
Maintenance of tooth integrity (Maintenance of tooth integrity (calcium and phosphate ions)calcium and phosphate ions)
Tissue repair. BTissue repair. Bbleeding time of oral tissues shorter thanbleeding time of oral tissues shorter than
other tissuesother tissues
Taste. sTaste. solubilizing of food substances that can be sensedolubilizing of food substances that can be sensed
by receptorsby receptors

31.  Composition of Saliva: 97-99.5% waterComposition of Saliva: 97-99.5% water
 pH 6.75-7.0pH 6.75-7.0
 Sodium, potassium, chloride, phosphate,Sodium, potassium, chloride, phosphate,
and bicarbonateand bicarbonate
 MucinMucin
 Salivary amylaseSalivary amylase

32. 32
Regulation of Salivary secretion
A) Simple or unconditioned: The presence of food in
the mouth results in reflex secretion of saliva.
• Stimulus: presence of food in the mouth.
• Receptors: taste buds.
• Afferent: nerves from taste buds carry impulses
to salivary centre.
• Centre: salivary centre in medulla oblongata
(in brain stem).
• Efferent: autonomic nerves supplying salivary
glands.

33. The PharynxThe Pharynx
Three regions defined by location and function:Three regions defined by location and function:
NasopharynxNasopharynx- air passage way only: composed of- air passage way only: composed of
pseudostratified ciliated columnar epitheliumpseudostratified ciliated columnar epithelium
OropharynxOropharynx- back of oral cavity down to epiglottis:- back of oral cavity down to epiglottis:
-composed of stratified squamous epithelium.-composed of stratified squamous epithelium.
LaryngopharynxLaryngopharynx- air passageway, food is deflected into- air passageway, food is deflected into
esophagus and does not enter this regionesophagus and does not enter this region
-composed of stratified squamous epithelium-composed of stratified squamous epithelium

34. Pharynx AnatomyPharynx Anatomy
Slide 14.8Slide 14.8
• Nasopharynx –
not part of the
digestive system
• Oropharynx –
posterior to oral
cavity
• Laryngopharynx –
below the oropharynx
and connected to
the esophagus Figure 14.2a

35. Pharynx FunctionPharynx Function
Slide 14.9Slide 14.9
• Serves as a passageway for air and
food
• Food is propelled to the esophagus by
two muscle layers
•Longitudinal inner layer
•Circular outer layer
• Food movement is by alternating
contractions of the muscle layers
(peristalsis)

36. Deglutition and the PharynxDeglutition and the Pharynx
 Deglutition = swallowingDeglutition = swallowing
 Oropharynx and Laryngopharynx are commonOropharynx and Laryngopharynx are common
passageways for food and airpassageways for food and air
 Pharynx contains stratified squamous epitheliumPharynx contains stratified squamous epithelium
(friction-resistant)(friction-resistant)

37. EsophagusEsophagus
Slide 14.10Slide 14.10
• Runs from pharynx to stomach through
the diaphragm
• Conducts food by peristalsis
(slow rhythmic squeezing)
• Passageway for food only (respiratory
system branches off after the pharynx)

38. Anatomical StructureAnatomical Structure
 A muscular tube (25cm )A muscular tube (25cm )
connecting pharynx to stomach.connecting pharynx to stomach.
 Guarded at both ends byGuarded at both ends by
sphincters.sphincters.
 Lies anterior to cervical vertebrae inLies anterior to cervical vertebrae in
neck & in posterior mediastinum inneck & in posterior mediastinum in
chest & enters abdomen throughchest & enters abdomen through
oesophageal hiatus in diaphragm.oesophageal hiatus in diaphragm.
 Passes through the diaphragm atPasses through the diaphragm at
the esophageal hiatusthe esophageal hiatus
 The last 2-3 cm are within abdomenThe last 2-3 cm are within abdomen
aboveabove esophagogastric junctionesophagogastric junction
with stomach.with stomach.

40. EsophagusEsophagus
 Secretes mucous, transports food – no enzymes produced, noSecretes mucous, transports food – no enzymes produced, no
absorptionabsorption
 MucosaMucosa:: Stratified squamous epithelium;Stratified squamous epithelium; protection againstprotection against
wear and tearwear and tear
 lamina propria:lamina propria:
 Submucosa:Submucosa: moderately dense CT with blood, nerve, lymphmoderately dense CT with blood, nerve, lymph
vessels & lymphoid follicles; rich in elastic fibersvessels & lymphoid follicles; rich in elastic fibers
 MuscularisMuscularis divided in thirdsdivided in thirds
 Superior 1/3 skeletal muscleSuperior 1/3 skeletal muscle
 Middle 1/3 skeletal and smooth muscleMiddle 1/3 skeletal and smooth muscle
 Inferior 1/3 smooth muscleInferior 1/3 smooth muscle
 2 Sphincters2 Sphincters – upper esophageal sphincter (UES)– upper esophageal sphincter (UES)
regulates movement into esophagus, lower esophagealregulates movement into esophagus, lower esophageal
sphincter (LES) regulates movement into stomachsphincter (LES) regulates movement into stomach
 Adventitia: consist of loose C.TAdventitia: consist of loose C.T no serosa – attaches tono serosa – attaches to
surroundingssurroundings

41. Anatomy of the EsophagusAnatomy of the Esophagus

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43. 03/07/1803/07/18 copyright (your organization) 2003copyright (your organization) 2003 4343

44. Features and Functions of theFeatures and Functions of the
EsophagusEsophagus
 Muscular tube that propels food to stomach;Muscular tube that propels food to stomach;
bolus enters stomach throughbolus enters stomach through esophageal hiatusesophageal hiatus
 Skeletal muscle (upper third for swallowing) andSkeletal muscle (upper third for swallowing) and
smooth muscle (lower third) for peristalsissmooth muscle (lower third) for peristalsis
 Esophageal glands – produce mucus to lubricateEsophageal glands – produce mucus to lubricate
bolusbolus
 Esophageal sphincter – prevents backflow intoEsophageal sphincter – prevents backflow into
oral cavityoral cavity
 Cardiac sphincter- prevents backflow intoCardiac sphincter- prevents backflow into
esophagusesophagus

45. Nerve SupplyNerve Supply
 ParasympatheticParasympathetic
 Vagus – motor to muscular coats & secretomotor to glandsVagus – motor to muscular coats & secretomotor to glands
 SympatheticSympathetic
 From cervical & thoracic sympathetic chainFrom cervical & thoracic sympathetic chain
 Contraction of sphincters, wall relaxation, peristalsisContraction of sphincters, wall relaxation, peristalsis
 IntramuralIntramural
 Combination of all innervation form plexuses & gangliaCombination of all innervation form plexuses & ganglia
 In muscular layers (myenteric or Auerbach’s plexus)In muscular layers (myenteric or Auerbach’s plexus)
 In submucosa (Meissner plexus)In submucosa (Meissner plexus)

46. Digestive Processes in the Mouth,Digestive Processes in the Mouth,
Pharynx, and EsophagusPharynx, and Esophagus
 Mouth processes:Mouth processes:
 IngestionIngestion
 Mechanical digestion (e.g. salivary amylase)Mechanical digestion (e.g. salivary amylase)
 Initiation of PropulsionInitiation of Propulsion
 Mastication: chewingMastication: chewing
 Pharyngeal processes:Pharyngeal processes:
 Deglutition = swallowingDeglutition = swallowing
 Voluntary Buccal phaseVoluntary Buccal phase
 Involuntary Pharyngeal-Esophageal PhaseInvoluntary Pharyngeal-Esophageal Phase
 Esophageal processes:Esophageal processes:
 Peristalsis (rhythmic contractions, involuntary)Peristalsis (rhythmic contractions, involuntary)

47. PeristalsisPeristalsis

48. 4848
SwallowingSwallowing
 Swallowing can be initiated voluntarily butSwallowing can be initiated voluntarily but
then it is under reflex control.then it is under reflex control.
Swallowing reflex:Swallowing reflex:
 ReceptorsReceptors: touch receptors in pharynx.: touch receptors in pharynx.
 AfferentAfferent: sensory impulses from receptors.: sensory impulses from receptors.
 CentreCentre: swallowing centre in brain stem.: swallowing centre in brain stem.
 EfferentEfferent: parasympathetic nerves to muscles: parasympathetic nerves to muscles
of pharynx and esophagus.of pharynx and esophagus.

49. 4949
Mechanism of SwallowingMechanism of Swallowing
 3 stages:3 stages:
 Oral or Voluntary:Oral or Voluntary: bolus of food is passed intobolus of food is passed into
the pharynx by upward and backward movementthe pharynx by upward and backward movement
of tongue against palate. This stimulates the touchof tongue against palate. This stimulates the touch
receptors that initiate the swallowing reflex.receptors that initiate the swallowing reflex.
 Pharyngeal:Pharyngeal: involuntary passage of bolusinvoluntary passage of bolus
through the pharynx into esophagus. Respiratorythrough the pharynx into esophagus. Respiratory
passageways are closed & respiration is inhibitedpassageways are closed & respiration is inhibited
(protective reflexes).(protective reflexes).
 Esophageal:Esophageal: involuntary passage of bolus frominvoluntary passage of bolus from
esophagus to stomach by peristaltic movements ofesophagus to stomach by peristaltic movements of
esophagus.esophagus.