The digestive system breaks down food into nutrients that can be absorbed and used by cells in the body. It consists of a digestive tract made up of the oral cavity, esophagus, stomach, and small and large intestines. Accessory organs that help digestion include salivary glands, liver, gallbladder and pancreas. Food is ingested, mechanically and chemically broken down, absorbed, and waste is eliminated in a complex multi-step process involving both the digestive tract and accessory organs.

1. DIGESTIVE SYSTEM
PREPARED BY: GROUP 3

2. DIGESTIVE SYSTEM
• Digestive system, with the help of circulatory system, is a complex set of organs,
glands, and ducts that work together to transform food into nutrients for cells.
COMPONENTS:
1. Digestive tract
• A core tube that starts from mouth down to the anus – ALIMENTARY CANAL.
• Oral cavity, Pharynx, Esophagus, Stomach, Small and Large intestine.
2. Accessory glands
• Secrete products into digestive tract.
• Salivary glands, teeth and tongue, liver, and pancreas.

3. DIGESTIVE SYSTEM

4. DIGESTIVE SYSTEM
 Ingestion
• Occurs when solid food and liquid enter the oral cavity.
 Mechanical digestion and propulsion
• Involves crushing and shredding of food in the oral cavity and mixing and churning
in the stomach.
 Chemical digestion
• Chemical and enzymatic breakdown of food into small organic molecules that can be
absorbed by the digestive epithelium.
 Secretion
• The release of water, acids, enzymes, buffers, and salts by the digestive tract
epithelium and by accessory digestive organs.
 Absorption
• Movement of nutrients across the digestive epithelium and into the bloodstream.
 Defecation
• Indigestible food is compacted into material waste called feces, which are
eliminated by defecation.

5. DIGESTIVE TRACT STRUCTURES
4 MAJOR TUNICS
1. MUCOSA (Inner tunic)
• Mucous epithelium
• Lamina propria – loose connective tissue
• Muscularis mucusae – thin outer layer of smooth muscle.
2. SUBMUCOSA
• Thick Layer of loose connective tissue – contains nerves, blood vessels and small
glands.
• An extensive network of nerve cell forms plexus within submucosa.
• Autonomic nerves innervate this plexus.

6. DIGESTIVE TRACT STRUCTURES
4 MAJOR TUNICS (continue)
3. MUSCULARIS
• Circular smooth muscle
• Longitudinal smooth muscle
• Enteric nervous system
• Composed by the nerve plexus of submucosa and muscularis.
• Controls movement and secretion within the tract.
4. SEROSA
• Consist of peritoneum, smooth epithelial layer and its underlaying connective tissue.
• Adventitia – covered by a connective tissue but not peritoneum.
• Means “foreign/coming from the outside”

7. PERITONEUM
• A walls of abdominal cavity and the abdominal organs that are
associated with serous membrane.
• VISCERAL PERITONEUM – serous membrane that covers organs.
• PARIETAL PERITONEUM – serous membrane that line the wall of abdominal
cavity.
• MESENTERIES – connective tissue sheets where many organs of abdominal cavity
are being held.
• Provide a route for blood vessels and nerve from abdominal wall to the organs.
• MESENTERY PROPER – mesentery associated with the small intestines.
• LESSER OMENTUM – mesentery connecting the lesser curvature of the stomach
to the liver and diaphragm.
• GREATER OMENTUM – mesentery connecting the greater curvature of the
stomach to the transverse colon.
• OMENTAL BURSA – double fold mesentery that extends inferiorly from the
stomach before looping back to the transverse colon which to create cavity.

8. DIGESTIVE TRACT STRUCTURE
PERITONITIS
Life-threatening inflammation of the
peritoneal membrane.
CAUSES:
• Chemical irritation by substances, such
as bile, that escape from the digestive
tract.
• Infected appendix ruptures.
SYMPTOMS:
• Acute abdominal pain
• Tenderness that are worsened by
movement.

9. MAJOR ORGANS
1. ORAL CAVITY
• Mechanical processing.
2. PHARYNX
• Muscular propulsion of food.
3. ESOPHAGUS
• Transport material to the stomach.
4. STOMACH
• Chemical breakdown and mechanical processing.
5. SMALL INTESTINE
• Enzymatic digestion and absorption.
6. LARGE INTESTINE
• Dehydration and compaction of indigestible materials.

10. ANATOMY OF ORAL CAVITY
PARTS OF ORAL CAVITY:
1. Lips (labia) – protect the anterior opening
2. Cheeks – form the lateral walls
3. Hard palate – forms the anterior roof
4. Soft palate – forms the posterior roof
5. Uvula – fleshy projection of the soft palate
6. Vestibule – space between lips externally and teeth
and gums internally
7. Oral cavity – area contained by the teeth

11. ORAL CAVITY FUNCTIONS
• Begins the process of digestions.
• Break down large food particles into smaller ones.
• Mastication.
MASTICATION
Is a complex mechanism involving opening and closing of the jaw,
secretion of saliva, and mixing of food with the tongue.

12. PHARYNX
PARTS OF PHARYNX
1. Nasopharynx – not part of digestive system.
2. Oropharynx – posterior to the oral cavity.
3. Laryngopharynx – inferior to the oropharynx.
• The posterior walls of the of the oropharynx and
laryngopharynx are formed by the superior,
middle and inferior pharyngeal constrictor
muscles.
FUNCTIONS
• Connects the mouth with the esophagus.
• Carry food to the esophagus.

13. ESOPHAGUS
• A muscular tube , lined with moist squamous
epithelium, that extends from the pharynx to
the stomach.
• It is about 25 cm long.
• Upper 2/3 of the esophagus has skeletal muscle
in its wall, while the lower 1/3 has a smooth
muscle in its wall.
CONTROL MOVEMENT:
1. Upper esophageal sphincters
• Prevent air from entering the stomach.
2. Lower esophageal sphincters
• Prevent backflow of stomach contents.

14. SWALLOWING
1. Voluntary phase
• Bolus (mass of foods) is formed in the mouth.
• Tongue pushes the bolus against the hard palate.
• This forces the bolus toward posterior parts of the mouth and into the
oropharynx.
2. Pharyngeal phase
• Controlled by the reflex.
• Bolus stimulate oropharynx receptor to close of nasopharynx.
• Pharyngeal constrictor muscles contract in succession.
• Upper esophageal sphincter relaxes making foods pushes into esophagus.
• Vestibular and vocal folds closes and epiglottis is tipped posteriorly, so that
the opening into the larynx is covered.
3. Esophageal phase
• Muscular constrictions of the esophagus occur in peristalsis wave .

15. PERISTALSIS
• Wave of muscle contraction
• Food enters the digestive tract as a
bolus
• Moist, compact mass of material
• Bolus is propelled along the tract by
contractions of the muscularis externa
(peristalsis)
• Circular muscles contract behind bolus
• Longitudinal muscles ahead of bolus contract
• Process repeats

16. ANATOMY OF THE STOMACH
REGIONS OF THE STOMACH
• Cardiac region
• Near the heart
• Around the gastroesophageal opening
• Fundus
• Most superior part of the stomach.
• Body
• Larger part of the stomach.
• Greater curvature -
• Lesser curvature
• Pyloric
• Pyloric sphincter- pyloric opening surrounded by the
thick ring smooth muscle.
• Pyloric region – region of the stomach near the pyloric
opening.
MUSCULARIS LAYERS
• Produces a churning actions in the
stomach, important in digestive process.
1. Outer longitudinal layer
2. Middle circular layer
3. Inner oblique layer
SUBMUCOSA AND MUCOSA
• RUGAE
• Has a large folds.
• Allow the submucosa and mucosa to
stretch.
• Disappear when the stomach is filled.

17. ANATOMY OF THE STOMACH
• Simple columnar epithelium.
• Gastric pits
• Mucosal surface forms numerous tubelike which the gastric glands open.
• Gastric glands.
• Mucous neck cells – produce mucous
• Parietal cells – produce hydrochloric acid and intrinsic factor.
• Endocrine cells – produce regulatory chemicals.
• Chief cells – produce pepsinogen (precursor of the protein digesting enzyme)
• Surface mucous cells
• first group of epithelial cells consist of surface mucous cells.
• Produce mucus
• Coat and protect the stomach lining.

18. ANATOMY OF THE STOMACH

19. SECRETIONS OF THE STOMACH
• As food enter stomach, the food mixed with stomach secretions to become a semifluid
mixture called chyme.
1. Hydrochloric acid
• Produces a pH of about 2.0 in the stomach
• Kills microorganism and activates the pepsin.
2. Pepsin
• Pepsinogen (inactive form)
• Breaks a covalent bonds of protein to form smaller peptide chains.
3. Mucus
• Form thick layer, lubricates the epithelial cells and protect them form the damaging effect of the acidic
chyme and pepsin.
• Irritation of the stomach mucosa stimulates secretion f a great volume of mucus.
4. Intrinsic
• Binds with vitamin B12 and make it more readily absorbed in the small intestine.
• Important in DNA synthesis and in red blood cell productions.

20. REGULATION OF STOMACH SECRETIONS
• 2l of gastric secretions are produce each day.
• Both nervous and hormonal mechanism regulates gastric secretions.
• Neural mechanism involve CNS reflexes integrated within the medulla
oblongata.
• Hormone produced by the stomach and intestine help regulate stomach
secretions.
• Three phase of stomach secretions
1. Cephalic phase
2. Gastric phase
3. Intestinal phase.

21. REGULATION OF STOMACH SECRETIONS
1. Cephalic phase
• Tactile sensation of the food in the mouth stimulate the medulla oblongata.
• Vagus nerve carry parasympathetic action potentials to the stomach, where the enteric plexus neuron
are activated.
• Postganglionic neurons stimulate secretion by parietal and chief cell and stimulate gastrin and
histamine secretion by endocrine cells.
• Gastrin carried through the blood back to the stomach along with the histamine.
2. Gastric phase
• Distention of the stomach stimulates mechanoreceptors parasympathetic reflex.
• Medulla oblongata increases action potential in the vagus nerve.
• Distention of the stomach also activates local reflexes that increase stomach secretions.
• Gastrin carried through the blood back to the stomach along with the histamine.
3. Intestinal phase
• Chyme in duodenum with a pH less than 2 inhibits gastric secretions by three mechanism.
• Chemoreceptor in the duodenum are stimulated by low pH. Action potential generated by the
chemoreceptors are carried by the vagus nerve to the medulla oblongata, where they inhibit
parasympathetic action potentials, there by decreasing gastric secretions.
• Local reflexes activated by lipids also inhibit gastric secretion.
• Secretin and cholecystokinin produced b the duodenum decrease gastric secretions in the stomach.

22. ANATOMY OF SMALL INTESTINE
• Another name for the small intestine is the small bowel.
• Small intestine is a 22-foot long muscular tube that breaks down food
using enzymes released by the pancreas and bile from the liver.
SUBDIVISION:
 Duodenum
 Attached to the stomach
 Curves around the head of the pancreas
 Most chemical digestion takes place.
 Jejunum
 Attaches anteriorly to the duodenum
 Has a lining designed for carbohydrates and protein absorption.
 Ileum
 Extends from jejunum to large intestine
 Absorb vitamin b12, bile salt, and any product of digestion that were not
absorbed by the jejunum.

23. ANATOMY OF SMALL INTESTINE
STRUCTURE INVOLVE IN ABSORPTION
• VILLI
 Fingerlike structures formed by the mucosa
 Give the small intestine more surface area
 Absorptive cells
 Blood capillaries
 Lacteals (specialized lymphatic capillaries)
• MICROVILLI
 Small projections of the plasma membrane
 Found on absorptive cells
FOLDS IN SMALL INTESTINE
Called circular folds or plicae circulares
Deep folds of the mucosa and submucosa
Do not disappear when filled with food
The submucosa has Peyer’s patches (collections of
lymphatic tissue)

24. ANATOMY OF SMALL INTESTINE

25. ANATOMY OF LARGE INTESTINE
CECUM
• The proximal end of the large intestine that joins with the small intestine at
ileocecal junction.
• Located in the right lower quadrant of the abdomen near the iliac fossa.
APPENDIX
• Attached to the cecum and about 9 cm long.
RECTUM
• Straight muscular tube that begins at the termination of sigmoid colon and end at
the anal canal.
• Compose of smooth muscle and relatively thick.
ANAL CANAL
• Begins at the end of the rectum and ends at the anus.
• Has an internal and external anal sphincter.

26. ANATOMY OF LARGE INTESTINE
COLON
1. Ascending colon – located near at the liver.
2. Transverse colon – located near the spleen.
3. Descending colon- located at the left flexure to the pelvis.
4. Sigmoid colon – located inferiorly into the pelvic cavity and ends at the
rectum.
Crypts
• Mucosal lining of the colon
• Mucus-producing goblet cells.
Teniae coli (Three bands)
• The longitudinal smooth muscle layer of the colon does not completely envelop
the intestinal wall but forms three bands.

27. ANATOMY OF LARGE INTESTINE

28. FUNCTIONS OF LARGE INTESTINE
 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

29. DIGESTIVE SECRETIONS FUNCTIONS

30. ACCESSORY ORGANS
1. SALIVARY GLANDS
• Produce saliva containing enzymes.
2. TEETH AND TONGUE
• Mechanical processing.
3. LIVER
• Produce bile.
4. GALLBLADDER
• Stores and concentrates bile.
5. PANCREAS
• Secretes enzymes and hormones.

31. SALIVARY GLANDS
SALIVA-PRODUCING GLANDS:
1. Parotid gland (Glandula parotidea)
• Largest among the 3 major glands.
• Located around the mandibular ramus.
• Produce 20% total of (serous type) salivary production.
• Rich in salivary amylase.
3. Sublingual gland (Glandula Sublingualis)
• Smallest among the 3 major glands.
• Located inferior to the tongue.
• Produce thick mucinous fluid
• Allow swallowing, initiating digestion and dental hygiene.
• Classified as Seromucous Type.
2. Submandibular gland (Glandula
Submandibularis)
• Located above the gastric muscles.
• Produces the majority of saliva production (70%)
• Classified as Seromucous Type.

32. SALIVARY GLANDS
Saliva – a watery which is secreted by salivary glands.
• Components of saliva:
• Serous component – contains enzymes (amylase).
• Mucous components – lubricates the ingested food (mucin).
• MINOR SALIVARY GLANDS
• Located throughout the oral cavity.
• Produce saliva continuously without neural stimuli.
• Contribute less than 5% of the total amount of salivary production.
• 3 types of minor glands
1. Buccal glands – located on cheeks.
2. Lingual glands – located on the tongue and lips.
3. Palatine glands – located on the root of the mouth.

33. STRUTURES AND FUNCTIONS OF TEETH
4 CLASSIFICATION OF TEETH
1. Incisors
• Located at center part of the mouth.
• 4 upper and 4 lower incisors present at primary and permanent dentition.
• Responsible for cutting foods.
2. Canines
• Located at the sides of incisors.
• 2 on the top and 2 on the bottom that features in both arches.
• Responsible for tearing foods.
3. Premolars
• Located after the canines and before molars.
• 4 on the top (2 on each sides) and 4 on the bottom.
• Responsible for crushing foods.
4. Molar
• Located behind the premolar.
• 12 molars in an adult (3 on each sides).
• Responsible for grinding and crushing food.

34. STRUTURES AND FUNCTIONS OF TEETH
REGIONS OF THE TOOTH
1. Crown
• Visible above the gum.
• Dentin
• Outer enamel
• Pulp cavity.
2. Neck
• Located at the gum line, between the root and the
crown.
• Connects the crown to the root.
3. Root
• Located below the gum.
• Root canal carry blood vessels and nerves.

35. ANATOMY OF LIVER
• Largest internal organ of the body and weighs about 1.36kg.
• Located at right upper quadrant of the abdomen and tucked
against the inferior surface of the diaphragm.
• Consist of two major lobe
• Right and Left lobe
• Separated by the connective tissue (falciform ligaments)
• Consist of two smaller lobe
• Caudate and Quadrate (inferior view)
• Porta (gate) through which blood vessel, nerves and ducts enter and exit the
liver.

36. ANATOMY OF LIVER

37. FUNCTIONS OF LIVER

38. ANATOMY OF GALLBLADDER
• Located on the posterior surface of
the liver’s right lobes.
• Stores and concentrates bile
secreted from the liver.
• Bile salt breaks lipid droplets apart by
emulsification.
• DIVIDED INTO 3 REGIONS
1. Fundus
2. Body
3. Neck
PATH OF BILE
• Right and left hepatic duct collect bile from the liver
bile duct.
• Hepatic duct reunited to form the common hepatic
duct.
• Bile flow from the common hepatic duct into:
• Bile duct (to the duodenum)
• Cystic duct (to the gallbladder for storage)
• The common bile duct penetrates the duodenal wall
and meet pancreatic duct at the duodenal ampulla.
• The hepatopancreatic sphincter encircles the lumens
of the areas where they enter the duodenum.

39. ANATOMY OF GALLBLADDER

40. ANATOMY OF PANCREAS
• Located retroperitoneal, posterior to the stomach and inferior part of
the left upper quadrant.
• It has head (near the midline of the body) and tail (extends to the left,
where touches the spleen)
• Has a complex organ composed of both endocrine and exocrine tissues.
• Pancreatic islet ( islets of Langerhans)
• Located in endocrine part of the pancreas.
• Produce the hormone insulin and glucagon.
• Acinar gland
• Located in exocrine part of the pancreas.
• Acini (grape) produce enzyme.
• Pancreatic duct (cluster of acini joined together to form a duct).

41. FUNCTIONS OF PANCREAS
MAJOR PROTEIN-DIGESTING ENZYME
1. Trypsin
• Trypsinogen (inactive)
• Stimulate production of cytokines from peritoneal macrophages.
2. Chymotrypsin
• Cleaves peptide bond.
3. Carboxypeptidase
• Break down protein into it’s constituent amino acids.
4. Pancreatic amylase
• Breaks down certain starches.
• Almost identical to salivary amylase.
5. Lipase
• Break down certain complex lipids.
• Releases products that can be easily absorb.
6. Nucleases
• Break down RNA and DNA.

42. SUMMARY OF DIGESTIVE SYSTEM
SEGMENTATION PERISTALSIS