The document summarizes key aspects of the digestive system, beginning with definitions of splanchnology and the digestive system. It describes the main organs and parts of the digestive system, including the oral cavity, esophagus, stomach, small and large intestines. It discusses the functions of digestion, including ingestion, mechanical and chemical breakdown of food, propulsion through the system, secretion of enzymes and hormones, and absorption of nutrients. It provides more detailed descriptions of the oral cavity, teeth, salivary glands, pharynx, esophagus, stomach, and stomach functions. The summary concludes with key points about the storage, mixing, and controlled release functions of the stomach.

1. The Department of Human anatomyThe Department of Human anatomy
Splanchnology.
Digestive system
Part –1

2.  Splanchnology-branch of anatomy, which
studies the structure of the internal
organs.
 The internal organs (viscera) are
responsible for important functions of the
organism: homeostasis, metabolism,
water and gases turnover, excretion of
metabolic products and reproduction.

3.  Digestive systemDigestive system is theis the
food processing system offood processing system of
human body. The wholehuman body. The whole
digestive system is in thedigestive system is in the
form of a long, hollow,form of a long, hollow,
twisted and turned tube,twisted and turned tube,
called the alimentarycalled the alimentary
canal, which starts fromcanal, which starts from
the oral cavity and ends atthe oral cavity and ends at
the anus. The overallthe anus. The overall
process of digestion andprocess of digestion and
absorption of food occursabsorption of food occurs
in this tube. The tube isin this tube. The tube is
divided into different partsdivided into different parts
on the basis of structureon the basis of structure
and function of each part.and function of each part.

4.  ISCOMS – 2009ISCOMS – 2009
 ISCOMS – International StudentISCOMS – International Student
Congress of Medical Sciences –Congress of Medical Sciences –
is one of the world’s leadingis one of the world’s leading
student conferences in thestudent conferences in the
medical sciences.medical sciences.
 the University Medical Center ofthe University Medical Center of
Groningen (theGroningen (the NetherlandsNetherlands ) )
With Prof. Robin WarrenWith Prof. Robin Warren
MD PhD, Nobel PrizeMD PhD, Nobel Prize
laureate in 2005laureate in 2005
he is credited with the 1979 re-discoveryhe is credited with the 1979 re-discovery
of the bacteriumof the bacteriumHelicobacter pyloriHelicobacter pylori,,
together with Barry Marshall.together with Barry Marshall.

5. SponsoredSponsored
Medical Lecture Notes – All SubjectsMedical Lecture Notes – All Subjects
USMLE Exam (America) – PracticeUSMLE Exam (America) – Practice

6. Necessary Organs Of the digestive system:Necessary Organs Of the digestive system:
 ORAL CAVITYORAL CAVITY
 ESOPHAGUSESOPHAGUS
 STOMACHSTOMACH
 SMALL INTESTINESMALL INTESTINE
 LARGE INTESTINELARGE INTESTINE
 ANUSANUS
Accessory Organs of the digestive system:Accessory Organs of the digestive system:
 LIVER AND GALL BLADDERLIVER AND GALL BLADDER
 PANCREASPANCREAS
 SALIVARY GLANDSSALIVARY GLANDS
 TEETHTEETH
 TONGUETONGUE

7. Functions of digestive system:Functions of digestive system:
 IngestionIngestion
 Digestion: break down of large particles of foodDigestion: break down of large particles of food

mechanical digestionmechanical digestion

chemical digestionchemical digestion
 PropulsionPropulsion
 peristalsisperistalsis
 segmentationsegmentation
 Secretion:Secretion:
 digestive enzymesdigestive enzymes
 hormoneshormones
 Absorption:Absorption:
 from external environment into internal environmentfrom external environment into internal environment
 across mucosaacross mucosa
 Elimination of wastes (defecation)Elimination of wastes (defecation)

8. Oral Cavity (mouth)Oral Cavity (mouth)
Entrance to the GI tract.Entrance to the GI tract.
 Initial site of digestion:Initial site of digestion:
 mechanical digestion (via mastication)mechanical digestion (via mastication)
 chemical digestion (via enzymes in saliva).chemical digestion (via enzymes in saliva).
 Bounded anteriorly by the teeth and lipsBounded anteriorly by the teeth and lips
 Bounded posteriorly by the oropharynx.Bounded posteriorly by the oropharynx.
 Superior boundary is formed by the hardSuperior boundary is formed by the hard
and soft palates.and soft palates.
 Floor, or inferior surface, of the oral cavityFloor, or inferior surface, of the oral cavity
 the tonguethe tongue

10.  FaucesFauces represent the openingrepresent the opening
between the oral cavity and thebetween the oral cavity and the
oropharynx.oropharynx.
 Fauces are bounded by pairedFauces are bounded by paired
muscular folds:muscular folds:
 glossopalatine arch (anterior fold)glossopalatine arch (anterior fold)
 pharyngopalatine arch (posteriorpharyngopalatine arch (posterior
fold)fold)
 Palatine tonsils are housedPalatine tonsils are housed
between the arches.between the arches.

12. TeethTeeth
 Collectively known as theCollectively known as the dentitiondentition..
 Responsible forResponsible for masticationmastication
 first part of the mechanical digestion.first part of the mechanical digestion.
 A tooth has:A tooth has:
 crowncrown
 neckneck
 one or moreone or more rootsroots
 Collectively, the roots, the dental alveoli,Collectively, the roots, the dental alveoli,
and the periodontal ligament that bindsand the periodontal ligament that binds
the roots to the alveolar processes form athe roots to the alveolar processes form a

13. TOOTH TYPES ARE :TOOTH TYPES ARE :
INCISORSINCISORS
CANINECANINE
PREMOLARSPREMOLARS
MOLARSMOLARS
COMPONENTS OF THE TOOTHCOMPONENTS OF THE TOOTH
INCLUDE:INCLUDE:
ENAMEL
DENTIN
PULP
CEMENTUM

14.  20 deciduous teeth, also called “milk teeth,”
erupt between 6 months and 30 months after
birth.
 These teeth are eventually lost and replaced by
32 permanent teeth.

15. THE LARGETHE LARGE SALIVARY GLANDSSALIVARY GLANDS ARE :ARE :
 PAROTIDPAROTID
 SUBMANDIBULARSUBMANDIBULAR
 SUBLINGUALSUBLINGUAL
GLANDS PRODUCE SEROUS AND MUCOSALGLANDS PRODUCE SEROUS AND MUCOSAL
SECRETIONSSECRETIONS
Components of salivaComponents of saliva
 Water:Water: makes up 99%makes up 99%
 AmylaseAmylase: first step of chemical digestion: first step of chemical digestion
 LysozymeLysozyme: antimicrobial: antimicrobial
FunctionsFunctions
 Moisten foodMoisten food
 Food molecules into solution: tasteFood molecules into solution: taste
 Form bolus: for swallowingForm bolus: for swallowing
 Cleanse oral cavity.Cleanse oral cavity.

17. TONSILS INCLUDETONSILS INCLUDE ::
PHARYNGEAL, PALATINE,PHARYNGEAL, PALATINE,
LINGUALLINGUAL
THETHE PHARYNXPHARYNX INCLUDES :INCLUDES :
 NASOPHARYNXNASOPHARYNX
 OROPHARYNXOROPHARYNX
 LARYNGOPHARYNXLARYNGOPHARYNX

18. SwallowingSwallowing
Swallowing involves coordinatedSwallowing involves coordinated
activity of tongue, soft palateactivity of tongue, soft palate
pharynx and oesophagus.pharynx and oesophagus.
The first (buccal) phase isThe first (buccal) phase is
voluntary, food being forcedvoluntary, food being forced
into the pharynx by the tongue.into the pharynx by the tongue.
After this the process is reflex.After this the process is reflex.
The tongue blocks the mouth,The tongue blocks the mouth,
soft palate closes off the nosesoft palate closes off the nose
and the larynx rises so that theand the larynx rises so that the
epiglottis closes off theepiglottis closes off the
trachea. Food thus moves intotrachea. Food thus moves into
the pharynx and onwards bythe pharynx and onwards by
peristalsis aided by gravity.peristalsis aided by gravity.
If we try to talk whilst swallowingIf we try to talk whilst swallowing
food may enter the respiratoryfood may enter the respiratory
passages and a cough reflexpassages and a cough reflex
expels the bolus.expels the bolus.

19. EsophagusEsophagus
 A straight muscular tube about 25-30A straight muscular tube about 25-30
cm longcm long
 It begins at the level of the cricoidIt begins at the level of the cricoid
cartilage, inferior to the larnyx behindcartilage, inferior to the larnyx behind
the trachea and extends through thethe trachea and extends through the
chest cavity, pierces the diaphragm atchest cavity, pierces the diaphragm at
the esophageal hiatus , and meets withthe esophageal hiatus , and meets with
the stomach at an opening called thethe stomach at an opening called the
cardiac orifice.cardiac orifice.
 It transports food to the stomach andIt transports food to the stomach and
secretes mucus, which aids transport.secretes mucus, which aids transport.
 The inferior segment is constrictedThe inferior segment is constricted
forming the lower esophageal sphincterforming the lower esophageal sphincter
which, along with the diaphragm,which, along with the diaphragm,
closes to prevent back flow ofcloses to prevent back flow of
stomach contentsstomach contents

20. StomachStomach
 An enlarged segment of theAn enlarged segment of the
tract that functions mainly intract that functions mainly in
storing food and mixing it withstoring food and mixing it with
gastric juice (creating a pastegastric juice (creating a paste
called chyme).called chyme).
Other functions of stomachOther functions of stomach
include:include:
 Chemical digestion of proteinsChemical digestion of proteins
 Secretion of intrinsic factor –Secretion of intrinsic factor –
a chemical that is necessarya chemical that is necessary
for vitamin B12 absorption.for vitamin B12 absorption.
 Destruction of ingestedDestruction of ingested
bacteria via secretedbacteria via secreted
hydrochloric acid.hydrochloric acid.

21. Gross anatomyGross anatomy
 CardiaCardia
 Cardiac orificeCardiac orifice
 FundusFundus
 BodyBody
 PylorusPylorus
 Pyloric sphincterPyloric sphincter
 Pyloric orificePyloric orifice
 Greater curvatureGreater curvature
 Greater omentumGreater omentum
 Lesser curvatureLesser curvature
 Lesser omemtumLesser omemtum

22.  THE WALL OF THE STOMACHTHE WALL OF THE STOMACH
INCLUDESINCLUDES ::
 EXTERNAL SEROSAEXTERNAL SEROSA
 MUSCLE LAYERMUSCLE LAYER
( CIRCULAR,( CIRCULAR,
LONGITUDINAL, OBLIQUE )LONGITUDINAL, OBLIQUE )
 SUBMUCOSASUBMUCOSA
 INTERIOR MUCOSALINTERIOR MUCOSAL
 The mucous membraneThe mucous membrane
lining the stomach islining the stomach is
thick and vascular. It isthick and vascular. It is
thrown into numerousthrown into numerous
folds, known as rugae,folds, known as rugae,
which are predominantlywhich are predominantly
longitudinal in direction.longitudinal in direction.
On distention of theOn distention of the
stomach, these foldsstomach, these folds
flatten out. It containsflatten out. It contains
the glands and thethe glands and the
gastric pits.gastric pits.

25. GASTRIC PITS ARE THEGASTRIC PITS ARE THE
OPENINGS INTO THE GASTRICOPENINGS INTO THE GASTRIC
GLANDSGLANDS
 Mucous neck cellsMucous neck cells – found in the– found in the
upper portion of the gland. Secreteupper portion of the gland. Secrete
acidic mucus and function as stemacidic mucus and function as stem
cells for surface mucous cells.cells for surface mucous cells.
 Chief cellsChief cells – primary function is– primary function is
the secretion of pepsinogen, anthe secretion of pepsinogen, an
inactive form of the protease,inactive form of the protease,
pepsin. Pepsinogen is activated bypepsin. Pepsinogen is activated by
HCl and by pepsin itself.HCl and by pepsin itself.
 Parietal cellsParietal cells – found in the– found in the
midportion of the glands. Secretemidportion of the glands. Secrete
hydrochloric acid (which gives thehydrochloric acid (which gives the
stomach its low pH – usually 1-3)stomach its low pH – usually 1-3)
as well as intrinsic factor.as well as intrinsic factor.
 Enteroendocrine cellsEnteroendocrine cells – secrete– secrete
multiple hormones into the plasma.multiple hormones into the plasma.
An example is gastrin, a hormoneAn example is gastrin, a hormone
that regulates the stomach’sthat regulates the stomach’s
motility and secretory activity.motility and secretory activity.

26. Stomach has three main functions;Stomach has three main functions;
 Storage of food:Storage of food: It stores food for a variable amount It stores food for a variable amount
of time (depending on the nature of food) in order toof time (depending on the nature of food) in order to
make it appropriate for digestion and absorption in themake it appropriate for digestion and absorption in the
small intestine. The storing capacity of stomach in ansmall intestine. The storing capacity of stomach in an
average adult is about 1500 ml.average adult is about 1500 ml.
 Mixing of food:Mixing of food: It mixes the food with its own It mixes the food with its own
secretions (gastric secretions) to form a semifluidsecretions (gastric secretions) to form a semifluid
chyme.chyme.
 Controlling the rate of delivery of chyme:Controlling the rate of delivery of chyme: TheThe
stomach also controls the rate of delivery of chyme tostomach also controls the rate of delivery of chyme to
the small intestine so that efficient digestion andthe small intestine so that efficient digestion and
absorption can take place.absorption can take place.

27. ThankThank you for attention!you for attention!