The digestive system is made up of the gastrointestinal tract—also called the GI tract or digestive tract—and the liver, pancreas, and gallbladder. The GI tract is a series of hollow organs joined in a long, twisting tube from the mouth to the anus.

1. THE DIGESTIVE SYSTEM
MOHANRAJ.S-B.PHARM
KMCH college of pharmacy
Coimbatore-48

2. The Digestive System

3. Steps in food digestion
Carbohydrates, proteins and lipids are absorbed in a form that can
not be taken up by the cells  food needs to be broken a small
pieces (mechanical digestion) and broken down chemically
(chemical digestion)
Chemical digestion refers to the degradation of:
1 2
 1- Carbohydrates ---> disaccharides ---> monosaccharides
 2- Proteins ---> peptides ---> amino acids
 3- Lipids ---> diglycerides ---> monoglycerides and
fatty acids

4. Digestive System
Alimentary canal Approximately 30 feet long
 Begins with mouth (oral cavity), ends with anus
Functions
 Prepare foods for absorption into the bloodstream
 Prepare foods for use by the body cells
 Responsible for elimination of solid wastes from the body
Digestion:
- Mechanical digestion: breaking food in small particles so they
are easily broken down by enzymes  mouth and stomach
- Chemical digestion: pancreas and duodenum
 Nutrient absorption: small intestine
 Water reabsorption: colon

5. Alimentary canal-Structures
 Mouth
 Pharynx
 Esophagus and Stomach
 Duedenum
 Jejenum
 Ileum
 Cecum
 Ascending colon
 Transverse colon
 Descending colon
 Sigmoid colon
 Rectum and Anus
Accessory structures
 Not in tube path
 Organs
 Teeth
 Tongue
 Salivary glands
 Liver
 Gall bladder
 Pancreas

7. Structure of the GI tract 4 layers:
1. mucosa: epithelial cells
- lamina propria = tissue under the
epithelial, containing blood vessels,
nerves and lymphatic vessels
2. submucosa: layer of connective
tissue rich containing the
submucosal plexus
3. muscularis externa – radial and
longitudinal smooth muscles
4. serosa:connective tissue
continuying through the
mesenteries and the peritoneum

8. The Mouth
 Mouth: mostly mechanical digestion  mastication  food is broken down
in small particles so food particles can be chemically digested  bolus
 Lips and cheeks enclose the mouth.
 Taste buds on the tongue provide the sense of taste; skeletal muscle in
the tongue allows it to move.
 The roof of the mouth is formed by the hard and soft palates that
separate it from the nasal cavities.
 The soft palate ends in a finger-shaped projection called the uvula.
 Tonsils at the back sides of the mouth protect against infections.
 Three pairs of salivary glands send saliva (containing salivary amylase for
digestion of starch to maltose) into the mouth.

9. The Teeth
Twenty deciduous (baby) teeth are
replaced by 32 adult teeth.
Each tooth has a crown and a root.
The crown has a layer of enamel,
dentin, and an inner pulp with
nerves and blood vessels that
extend into the root.

The tongue mixes the chewed
food with saliva and then forms
the mixture into a mass called a
bolus in preparation for
swallowing.

10. DigestionProcessing of food
Types
Mechanical (physical)
Chew
Tear
Grind
Mash
Mix
Chemical
Catabolic reactions
Enzymatic hydrolysis
 Carbohydrate
 Protein
 Lipid
Phases
Ingestion
Movement
Digestion
Absorption
Further digestion

11. Digestion

12. The Major Salivary Glands

13. Salivary glands
Three pairs
Parotids
Submandibulars
Sublinguals
Secrete saliva
Mostly water, but contains mucus and digestive enzymes that aid in
digestive process
Digestive enzymes contained in saliva
Amylase – aids in digestion of carbohydrates
Lipase – aids in digestion of fats

14. The Pharynx
The air passage and food passage cross in the pharynx because the
trachea is ventral to the esophagus.
Swallowing occurs in the pharynx and is a reflex action.
During swallowing, the air passage is usually blocked off by the
soft palate and uvula, and the trachea moves under the epiglottis
to cover the glottis opening to the windpipe.

15. Digestive System Structures
Pharynx
Known as the throat
Serves as passageway for both respiratory and digestive systems
Oropharynx
Section leading away from oral cavity
Nasopharynx
Behind nasal cavity
Laryngopharynx
Lower portion – opens into esophagus and larynx

16. Esophagus
Esophagus
Receives food from pharynx and propels it to stomach
Cardiac sphincter (lower esophageal sphincter) controls passage of food from
esophagus into the stomach
Relaxes = food enters stomach
Contracts = stomach contents prevented from reentering the esophagus
 The esophagus is a muscular tube that conducts food through the thoracic cavity and
diaphragm into the stomach.
 Peristalsis begins in the esophagus; this collapsed tube moves the bolus of food downward
after swallowing occurs.
 Heartburn is a burning pain when acidic stomach contents enter the esophagus.
 No chemical digestion occurs in the esophagus.
 The entrance of the esophagus to the stomach is marked by a constriction, called a
sphincter; the sphincter must relax in order for food to enter the stomach.
 The sphincter prevents food from backing up into the esophagus.
 Functions
Secrete mucous
Transport food

17. Stomach
 The stomach expands to store food.
 Food in the stomach is churned, mixing the food with gastric juices containing
hydrochloric acid and pepsin for the digestion of protein to peptides.
 Alcohol, but not food, is absorbed here.
 In 2–6 hours, the soupy chyme leaves the stomach.
 Ulcers are usually caused by a bacterial infection.
 Usually “J” shaped
 Mucous membrane
 G cells – make gastrin
 Goblet cells – make mucous
 Gastric pit – Oxyntic gland – Parietal cells – Make HCl
 Chief cells – Zymogenic cells
 Pepsin
 Gastric lipase

18. Anatomy of the Stomach
Fundus
Upper rounded portion
Body
Central part
Pylorus
Lower tubular part (also called
the gastric antrum)
Pyloric sphincter regulates
passage of food from stomach
into the duodenum
Folds in mucous membranes of
stomach = Rugae
Gastric juices breakdown food in
stomach
Muscular action of stomach causes
churning of food
Mixes food with the secretions
Chyme = liquidlike mixture of
partially digested food and
digestive secretions

19. FUNCTIONS OF STOMACH
Mixing of food
Reservoir
Start digestion of
Protein
Nucleic acids
Fats
Activates some enzymes
Destroy some bacteria
Makes intrinsic factor – B 12
absorption
Absorbs
Alcohol
Water
Lipophilic acid
B 12

20. Cephalic phase: salivary and gastric secretions
Salivary secretion stimulated by
parasympathetic NS by odors,
sight, taste  saliva fluid and rich
in enzymes
Stimulated by sympathetic NS
thick secretion, rich in proteins
Gastric secretion: increase acid
and enzymes secretion in response
to sight, smell and taste of food

21. Gastric
phase
Stimuli: presence of food in
the stomach (both distention
and nutrients)
Stimulation of the
parasympathetic NS and
secretion of gastrin (hormone)
Response: increased motility
and juice secretion

22. Intestinal phase
Arrival of nutrients in duodenum  decreased gastric secretion and
motility
Promotes secretion of cholecystokinin (CCK) and secretin
- CCK promotes:
- increased pancreatic enzyme secretion
- gallbladder contraction and sphincter of Oddi relaxation
- secretin promotes:
- bicarbonate ion secretion (pancreas)
- bile secretion

23. Small Intestine
It Extends from pyloric sphincter
to ileocecal valve
Approximately 20 feet long
Also known as the small bowel
Divided into three parts
Duodenum
Jejunum
Ileum
Movements in small intestine
Segmentation-circular muscle
contraction.
Peristalsis-waves of contraction
of longitudinal muscle fibers
moving down the GI tract

24. Small Intestine
 Enzymes that finish the process of digestion are produced by the
intestinal wall.
 Walls of the small intestine have finger-like projections called villi
where nutrient molecules are absorbed into the cardiovascular and
lymphatic systems.
 Villi have microvilli that increase the surface area available for
absorption.
 In response to eating protein foods, the hormone gastrin which
stimulate the stomach to produce digestive juice.
 The hormones secretin and cholecystokinin (CCK) are produced by the
duodenal wall and stimulate the pancreas to secrete digestive juice and
the gallbladder to release bile.
 Acidic chyme stimulates the secretion of secretin, while fatty chyme
with protein triggers CCK release.

25. Structure of the Villi in the Small Intestine

26. Functions of Small IntestineIt Absorbs
 80% ingested water
 Electrolytes
 Vitamins
 Minerals
 Carbonates
 Active/facilitated transport
 Monosaccharides
 Proteins
 Di-/tripeptides
 Amino acids
 Lipids
 Monoglycerides
 Fatty acids
 Micelles
 Chylomicrons
 Secretes digestive enzymes
Peptidases
Sucrases
Maltase
Lactase
Saccharidases
Lipase
Nucleases
Carbohydrate digetion,
Protein digetion
Fat digetion

27. The Large Intestine
It Extends from ileocecal valve to anus
Regions
The large intestine consists of the cecum, colon, rectum and anal canal.
The large intestine does not produce digestive enzymes but does absorb
water, salts, and some vitamins.
The colon includes the ascending colon, the transverse colon, the descending
colon, and the sigmoid colon.
The appendix is an extension of the cecum.
Indigestible material is stored in the rectum until the anus allows
defecation.
Anaerobic bacteria in the feces break down indigestible material and
produce some vitamins.
Water tests that show the presence of the bacterium Escherichia coli
indicate water is contaminated.

28. Anatomy of the Large Intestine

29. Functions of Large Intestine
1.Mechanical digestion
2.Chemical digestion – Bacterial
digestion
Ferment carbohydrates
Protein/amino acid breakdown
3.Absorption
• More water
• Vitamins B, K
4. Concentrate/eliminate
wastes
5.Feces formation and elimination
Chyme dehydrated to form feces
Feces composition
Water
Inorganic salts
Epithelial cells
Bacteria
Byproducts of digestion
6.Defecation
Peristalsis pushes feces into rectum
Rectal walls stretch
Control
Parasympathetic
Voluntary

30. Liver
 Bile is secreted by the liver hepatocytes & stored in
the gallbladder.
 Bile emulsifies fats; it is a yellowish-green substance
containing bilirubin from hemoglobin breakdown
and bile salts derived from cholesterol.
 The bile salts are reabsorbed back to the liver for
reuse.
 Location
 R. Hypochondrium-Epigastric region
 It has 4 Lobes
Left ,Quadrate,Caudate and Right
 Each lobe has lobules – Contains hepatocytes –
Surround sinusoids – Feed into central vein

31. Functions of
Liver
1.Bile Production
Detergent – emulsifies fats
Release promoted by
Vagus n.
CCK
Secretin
Composition of bile
Water
Bile salts
Bile pigments
Electrolytes
Cholesterol
Lecithin
2.Detoxifies/removes drugs
and alcohol
3.Storage functions
 Gycolgen
 Vitamins (A, D, E, K)
 Fe and other minerals
 Cholesterol
4.Activates vitamin D
5.Fetal RBC production
6.Phagocytosis
7.Metabolizes absorbed food molecules
 Carbohydrates
 Proteins
 Lipids
Additional Functions of liver
produces urea from amino acids,
Removes bilirubin after dismantling blood cells
Regulates blood cholesterol level when producing bile salts.
Synthesis of vitamin K-dependent plasma proteins

32. The Duodenum and Related Organs

33. The Pancreas
 The pancreas produces pancreatic juice, which contains digestive enzymes for
carbohydrate (pancreatic amylase), protein (trypsin), and fat (lipase), along with
sodium bicarbonate (NaHCO3) to neutralize acid in chyme.
 The pancreas is also an endocrine gland that secretes insulin and glucagon,
hormones that keep blood glucose within normal limits.
Pancreatic amylase Step 1 carbohydrate digestion
- Pancreatic lipase step 1 lipid digestion
- Bicarbonates ions from the pancreatic juice help neutralize the acidity of the
chyme.
Gallbladder
 The gallbladder is a pear-shaped muscular organ that stores bile until it is sent
to the duodenum.
 Water is reabsorbed in the gallbladder making the bile thick and mucus-like.
 Bile enters the duodenum via the common bile duct.
 Gallstones are crystals of cholesterol.

34. Figure 20.7
Absorption of carbohydrates
 Monosaccharides (mostly glucose) are absorbed
 The monomers are carried by transporter molecules across the epithelial cells and
into the blood capillary present in the villus  portal vein  liver
Absorption of proteins
 Proteins are degraded into amino acids and carried by transporter molecules across
the cells and into the blood capillaries  portal circulation  liver
Lipid absorption
 Lipids (triglycerides) are degraded to monoglycerides and fatty-acids.
 They are absorbed into the cell by diffusion. The cell resynthesizes triglycerides.
Because TG are not soluble in H2O, the TG are surrounded with proteins and
packaged into chylomicrons
 The chylomicrons are emptied into lymphatic capillaries, the lacteal  lymph
circulation  blood  cells and liver

35. Digestive System
PATHOLOGICAL
CONDITIONS

36. Liver Disorders
When a person has a liver disorder, jaundice may occur.
Jaundice is a yellowish tint to eyes and skin, indicating abnormal
levels of blood bilirubin.
Hepatitis is inflammation of the liver; different strains of virus
cause hepatitis A, B, etc.
Cirrhosis is scar tissue that can form when the liver is diseased or
killed by exposure to alcohol.

37.  Achlorhydria
 Abnormal condition characterized by the absence of hydrochloric acid in the gastric juice
 Anorexia
 Lack or loss of appetite, resulting in the inability to eat
 Aphagia
 Condition characterized by the loss of the ability to swallow as a result of organic or
psychologic causes
 Ascites
 Abnormal accumulation of fluid within the peritoneal cavity
 Fluid contains large amounts of protein and electrolytes
 Emesis
 Material expelled from the stomach during vomiting
 Vomitus
 Flatus; Flatulence
 Air or gas in the intestine that is passed through the rectum
 Gastroesophageal Reflux
 Backflow of contents of stomach into esophagus
 Often result of incompetence of the lower esophageal sphincter

38.  Nausea
 Unpleasant sensation often leading to the urge to vomit
 Vomit
 To expel the contents of the stomach through the esophagus and out of the mouth
 Appendicitis
 ]Inflammation of the vermiform appendix
 Usually an acute condition that can lead to rupture (perforation) with resultant inflammation of the peritoneum
(peritonitis)
Cirrhosis
 Disease of the liver that is chronic and degenerative causing injury to the hepatocytes (functional cells of the liver)
 Fat infiltrates lobules of the liver, causing tissue covering the lobes to become fibrous
 Functions of liver eventually deteriorat
 Colorectal Cancer
 Presence of a malignant neoplasm in the large intestine
 Constipation
 A state in which the individual’s pattern of bowel elimination is characterized by a decrease in the frequency of
bowel movements and the passage of hard, dry stools
 Individual experiences difficult defecation
 Crohn’s Disease
 Digestive tract inflammation of a chronic nature causing fever, cramping, diarrhea, weight loss, and anorexia

39.  Dysentery
 A term used to describe painful intestinal inflammation typically caused by ingesting water or
food containing bacteria, protozoa, parasites, or chemical irritants
 Person has frequent stools that often contain blood
 Gallstones (Cholelithiasis)
 Pigmented or hardened cholesterol stones formed as a result of bile crystallization
 Hemorrhoids
 Hemorrhoid is an unnaturally distended or swollen vein (varicosity) in distal rectum or
anus
 Hepatitis
 Acute or chronic inflammation of the liver due to a viral or bacterial infection, drugs,
alcohol, toxins, or parasites
Hernia
 Irregular protrusion of tissue, organ, or a portion of an organ through an abnormal break
in the surrounding cavity’s muscular wall
 Irritable Bowel Syndrome
 Increased motility of the small or large intestinal wall resulting in abdominal pain,
flatulence, nausea, anorexia, and the trapping of gas throughout the intestines

40.  Pancreatitis
 Acute or chronic destructive inflammatory condition of the pancreas
 May be acute or chronic
 Peptic Ulcers
 Break in the continuity of the mucous membrane lining of the gastrointestinal tract
as a result of hyperacidity or the bacterium, Helicobacter pylori
 Peptic ulcer descriptions
 Acute or chronic
 Singular or clustered
 Shallow or deep
 Symptoms of an ulcer
 Gnawing epigastric pain
 Heartburn or indigestion
 Nausea and vomiting
 Bloated feeling after eating
 Ulcerative Colitis
 Chronic inflammatory condition resulting in a break in the continuity of the mucous
membrane lining of the colon in the form of ulcers
 Characterized by large watery diarrheal stools containing mucus, pus, or blood