The digestive system breaks down ingested food into smaller molecules that can be absorbed and used by the body. It includes the alimentary canal and accessory organs. In the alimentary canal, food is ingested, digested, and absorbed. Accessory organs like the liver, pancreas and gallbladder secrete enzymes and bile to aid in digestion. Nutrients are then absorbed and circulated while waste is eliminated, completing the digestive process.

1. Digestive system
Anil N Lawrence
Lecturer
LNH CON

2. Function of the digestive system
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 Ingestion: taking food and liquid into
mouth
Secretion: total about 7 liter into lumen
Mixing and propulsion: through GI
muscle and peristalsis and motility
Digestion: Breakdown of ingested food
(mechanical and chemical)
Absorption: Passage of nutrients into
the blood
 Metabolism: Production of cellular
energy (ATP)
Defecation: waste substance leave the
GI tract through anus

3. Organs of the Digestive System
 Two main groups
 Alimentary canal or gastrointestinal tract –
continuous coiled hollow tube from mouth to
anus(5-7 meter)
 Accessory digestive organs: teeth ,tongue
,salivary gland ,liver ,gallbladder ,and
pancreas

4. Organs of the Digestive System

5. Organs of the Alimentary Canal
 Mouth
 Pharynx
 Esophagus
 Stomach
 Small intestine
 Large intestine
 Anus

6. Mouth (Oral Cavity) Anatomy
 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

7. Mouth (Oral Cavity) Anatomy
 Vestibule – space
between lips
externally and teeth
and gums internally
 Oral cavity – area
contained by the
teeth
 Tongue – attached
at hyoid bone and
styloid processes of
the skull, and by the
lingual frenulum

8. Tongue

 Dorsum (upper part of
tongue covered with
papillae taste receptor and
buds)
filiform papillae( griping
food)
Fungiform papillae
(The fungiform papillae are involved
in the sensations of taste and have
taste buds)
 circumvallate papillae
( particularly sensitive to sour
and bitter tastes)

9. Cont.
Palatine tonsil: play a role in protecting the body against respiratory
and gastrointestinal infections.
lingual tonsil: production of antibodies in response to invading
pathogenic bacteria or viruses.

10. Teeth
• Teeth
(mechanical breakdown)
– Incisors used for cutting
– Canines used for stabbing
and holding
– Molars large surface area
used for grinding
• Primary or deciduous
teeth 20
• Secondary or permanent
teeth 32

11. Structure of Teeth
Crown - exposed surface of tooth
Neck - boundary between root and crown
Enamel - outer surface (the hardest substance in the
body 95% calcium salts)
Dentin – bone-like, but noncellular(70% calcium
salts)
Pulp cavity - hollow with blood vessels and nerves
Root canal - canal length of root
gingival sulcus - where gum and tooth meet

12. Processes of the Mouth
 Mastication (chewing) of food
 Mixing masticated food with saliva to
produce easy digestied food called
bolus
 Saliva contain 2 enzyme,
salivary amylase(hydrolysis of starch into
sugars.) and lingual lipase(breakdown of
fats to fatty acids)
 Initiation of swallowing by the tongue
 Allowing for the sense of taste

13. Layers of Alimentary Canal Organs
 Mucosa
 Submucosa
 Muscularis propria
 serosa

14. Layers of Alimentary Canal Organs

15. Pharynx Anatomy
 Nasopharynx –
not part of the
digestive system
 Oropharynx –
posterior to oral
cavity
 Laryngopharynx –
below the oropharynx
and connected to
the esophagus

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

17. Esophagus
 Runs from pharynx to stomach through
the diaphragm( 25 cm)
 Conducts food by peristalsis
(slow rhythmic squeezing): contraction
of circular layer above the food and
contraction of longitudinal below the
food
 Passageway for food only (respiratory
system branches off after the pharynx)

18. Peristalsis in Esophagus
Bolus of
food
Muscles relax,
allowing
passageway
to open
Stomach
Muscles
contract,
constricting
passageway
and pushing
bolus down
Muscles
relax
Muscles contract
Muscles relax
Muscles contract

19. Stomach Anatomy
 Located on the left side of the
abdominal cavity
 Food enters at the
cardioesophageal sphincter
Site where food is churned into chyme
Protein digestion begins

20. Stomach Anatomy
 Regions of the stomach
Cardiac region – near the heart
Fundus
Body
Phylorus – funnel-shaped terminal end
 Food empties into the small intestine at
the pyloric sphincter

21. Stomach

22. Stomach Anatomy
 Rugae – internal folds of the mucosa
 External regions
Lesser curvature
Greater curvature

23. Stomach

24. Stomach Functions
 Acts as a storage tank for food
 Site of food breakdown and mixing
 Chemical breakdown of protein begins
 Delivers chyme (processed food) to the
small intestine

25. Specialized Mucosa of the
Stomach
 Simple columnar epithelium
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 Mucous neck cells – produce a sticky
alkaline mucus
Gastric glands – secrete gastric juice
Chief cells – produce protein-digesting
enzymes (pepsinogens)
Parietal cells – produce hydrochloric acid
and Intrinsic factor(B12 absorption)
Endocrine cells (G cell) – produce gastrin
which stimulates both parietal and chief cells)

26. Peritoneum
• Is the largest serous membrane of the body consist of
mesothelium
• Divide into
1. Parietal peritoneum: lines the wall of abdominopelvic
cavity internally
2. Visceral peritoneum: cover some oh the organs in the
cavity
3. The space between them contain fluid and called
peritoneal cavity this cavity may be accumulated by
several liters of fluid state called ascites

28. Small Intestine
 The body’s major digestive organ
 Site of nutrient absorption into the blood
 Muscular tube extending form the
pyloric sphincter to the ileocecal valve

29. Subdivisions of the Small Intestine
 Duodenum(25cm)
Attached to the stomach
Curves around the head of the pancreas
Fixed retroperitoneal structure
 Jejunum (2.5m)
Attaches anteriorly to the duodenum
 Ileum (3.5m)
Extends from jejunum to large intestine

30. Regions of Small Intestine

31. Small intestine

32. Chemical Digestion in the Small
Intestine
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 Source of enzymes that are mixed with
chyme
Intestinal cells
Pancreas
 Bile enters from the gall bladder

33. Structures Involved in Absorption
of Nutrients
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
 Absorptive
cells(absorption of nutrients)
 Blood capillaries
(transport nutrients)
 Lacteals (specialized
lymphatic capillaries)
absorb digested fats
Figure 14.7b

34. Large Intestine
SlideCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
 Larger in diameter, but shorter than the
small intestine
 Frames the internal abdomen

35. Large Intestine
SlideCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 14.8

36. Regions of Large Intestine
Cecum – pocket at proximal end with
Appendix
Colon
Ascending colon - on right
Transverse colon - horizontal
portion
Descending colon - left side
Sigmoid colon - S bend near terminal
end
Rectum – terminal end is anal canal - ending at the anus -
which has internal involuntary sphincter and external voluntary
sphincter

37. Functions of the Large Intestine
SlideCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
 Absorption of water
 Eliminates indigestible food from the
body as feces
 Does not participate in digestion of food
 Goblet cells produce mucus to act as a
lubricant

38. Structures of the Large Intestine
SlideCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
 Cecum – saclike first part of the large
intestine
 Appendix
Accumulation of lymphatic tissue that
sometimes becomes inflamed
(appendicitis)
Hangs from the cecum

39. Structures of the Large Intestine
SlideCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
 Colon
Ascending
Transverse
Descending
S-shaped sigmoidal
 Rectum
 Anus – external body opening

40. Food Breakdown and Absorption in
the Large Intestine
SlideCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
 No digestive enzymes are produced
 Resident bacteria digest remaining
nutrients
Produce some vitamin K and B
Release gases
 Water and vitamins K and B are absorbed
 Remaining materials are eliminated via
feces

41. Propulsion in the Large Intestine
SlideCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
 Sluggish peristalsis
 Mass movements
Slow, powerful movements
Occur three to four times per day
 Presence of feces in the rectum causes
a defecation reflex
Internal anal sphincter is relaxed
Defecation occurs with relaxation of the
voluntary (external) anal sphincter

42. Liver
SlideCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
 Largest gland in the body
 Located on the right side of the body
under the diaphragm
 Consists of four lobes suspended from
the diaphragm and abdominal wall by
the falciform ligament
 Connected to the gall bladder via the
common hepatic duct

43. Liver
e
,
On right under diaphragm,
largest organ made up of 4
lobes (left and right, caudat
and quadrate)
Hilus (porta hepatis) –
underside "entry" point
Gall bladder

44. Role of the Liver in Metabolism
SlideCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
 Several roles in digestion
 Detoxifies drugs and alcohol
 Degrades hormones
 Produce cholesterol, blood proteins
(albumin and clotting proteins)
 Plays a central role in metabolism

45. Bile
SlideCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
 Produced by cells in the liver
 Composition
Bile salts
Bile pigment (mostly bilirubin from the
breakdown of hemoglobin)
Cholesterol
Phospholipids
Electrolytes

46. Gall Bladder
SlideCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
 Sac found in hollow fossa of liver
 Stores bile from the liver by way of the
cystic duct
 Bile is introduced into the duodenum in
the presence of fatty food
 Gallstones can cause blockages

47. Chemical Digestion in the Small
Intestine
SlideCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 14.6

48. Processes of the Digestive System
SlideCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
 Ingestion – getting food into the mouth
 Propulsion – moving foods from one
region of the digestive system to
another

49. Processes of the Digestive System
SlideCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Peristalsis – alternating
waves of contraction
Segmentation – moving
materials back and forth
to aid in mixing
Figure 14.12

50. Processes of the Digestive System
SlideCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
 Mechanical digestion
Mixing of food in the mouth by the tongue
Churning of food in the stomach
Segmentation in the small intestine

51. Processes of the Digestive System
SlideCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
 Chemical Digestion
Enzymes break down food molecules into
their building blocks
Each major food group uses different
enzymes
Carbohydrates are broken to simple sugars
Proteins are broken to amino acids
Fats are broken to fatty acids and alcohols

52. Processes of the Digestive System
SlideCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
 Absorption
End products of digestion are absorbed in
the blood or lymph
Food must enter mucosal cells and then
into blood or lymph capillaries
 Defecation
Elimination of indigestible substances as
feces

53. Processes of the Digestive System
Slide

54. Nutrition
Slide
 Nutrient – substance used by the
body for growth, maintenance, and
repair
 Categories of nutrients
Carbohydrates: simple sugars, starches,
fiber
Lipids: triglycerides, phospholipids, fatty
acids
Proteins: amino acids
Vitamins
Mineral
Water