The document outlines the structure and functions of the human digestive system, including phases of digestion, main organs involved such as the alimentary canal, and accessory organs like the liver and pancreas. It details the processes of ingestion, mechanical and chemical digestion, and absorption of nutrients, as well as the roles of various digestive enzymes and juices. Additionally, it discusses the importance of the basal metabolic rate and definitions related to digestion and metabolism.

1. Prepared by
Ms. Nisha S. Mhaske
M.Pharm (Q.A.T)
Lecturer, PRES’s COPD, Chincholi.
Email : nisha.mhaske@pravara.in

2. CONTENTS
 Digestion phases
 Function of digestive system
 Main divisions of digestive system
 Buccal cavity
 Alimentary canal
 Esophagus
 Stomach
 Small intestine
 Pancreas
 Liver
 Gall bladder
 Large intestine
 Rectum
 BMR
 Definitions

4. DIGESTION PHASES
 Phases Include
1. Ingestion
2. Movement
3. Mechanical and Chemical Digestion
4. Absorption
5. Elimination

5. FUNCTION OF DIGESTIVE SYSTEM
 The cell requires essential materials for Growth, for
carrying out other structural activities & as a source of
energy for these activities.
 The food material serves these purposes.
 Hence, human organism needs a regular supply of food.
 The food that we eat contains complex substances.
 Digestion helps to convert complex food into simple food
so that they easily get absorb into blood.

6. DIGESTION
 Definition:-“The conversion of complex food into
simple form so that it is easily absorbed in the
blood is called as digestion.”
 The digestive system includes the Alimentary
canal and some accessory organs.

7. MAIN DIVISIONS OF THE DIGESTIVE SYSTEM
Alimentary Canal
 The alimentary tract is a long tube through which food
passes.
 It begins at the mouth and terminates at the anus.
 Digests and absorbs food particles
 Contains the following organs:
Mouth
Pharynx
Esophagus
Stomach
Small Intestine
Large Intestine
Rectum.

8. ACCESSORY DIGESTIVE ORGANS
 Contains the following organs
Teeth
Tongue
Gallbladder
Three pairs of salivary Glands
Liver
Pancreas.

11. TONGUE
 Taste is detected by
taste buds present on
tongue.
 It is fleshy muscular
organ attached to
floor of buccal
cavity.
 It is free at the front
& moves in all
direction.

12. TEETH & MASTICATION
 In an adult, the total number of teeth are 32, sixteen in each jaw.
 2 incisors, 1 canine, 2 pre-molars & 3 molars.

13.  Mastication is the
main work of
teeth.
 It involves biting
& grinding of
food between the
upper & lower
teeth.
 Movements of the
tongue & cheek
assist, by the
movement of food
against the hard
palate & the teeth.

14.  Teeth mechanically
break down food into
small pieces. Tongue
mixes food with saliva
(contains amylase,
which helps break
down starch).
 Epiglottis is a flap-like
structure at the back of
the throat that closes
over the trachea
preventing food from
entering it. It is located
in the Pharynx.

15. SALIVARY GLAND
Three pairs of salivary
glands
Submandibular
Glands
 Found underneath the
mandible
Sublingual Glands
 Found underneath the
tongue
Parotid Glands
 Found anterior to the
ear between masseter
and skin
 Largest gland

16. COMPOSITION OF SALIVA
 97-99.5% water
 pH 6.75-7.0
 Sodium, potassium, chloride, phosphate, and
bicarbonate
 Mucin
 Salivary amylase
 Enzyme Ptyalin acts on cooked starches in
alkaline medium & converts them to soluble form
called maltose.
 The action of the enzyme continues till the food is
rendered acidic by the action of gastric fluid.

17. FUNCTION OF SALIVARY GLAND
 Secretion of saliva which is stimulated by the sight, smell &
presence of food in the mouth.
 Saliva moistens the mouth
 Cleanses the tongue
 Makes speech easier
 Begins the chemical breakdown of food
Mouth
Digestive juices &
enzymes
Carbohydrates Proteins Fats
Saliva
Salivary Amylase Cooked Starches Maltose No action No action

19. ALIMENTARY CANAL
 The walls of alimentary canal are made up of the following 4
layers of tissue.
1. Outer covering consisting of peritoneum in the abdomen.
2. Muscle layer of both circular & longitudinal muscles
3. Submucous layer of loose connective tissue
4. Mucous membrane lining consisting of epithelial cells.

20. Peritoneum
Peritoneum is the serous membrane lining the abdominopelvic cavity.
• Visceral peritoneum covers the external surfaces of most digestive
organs and is continuous with the parietal peritoneum that lines the
body wall.
• Between the two peritoneums is the peritoneal cavity.

21. HISTOLOGY OF GI TRACT
 Mesentery is a double layer peritoneum; provides routes for
BV, lymphatics, nerves.
(BV-Blood Vessels)

22. DEGLUTITION AND THE PHARYNX
 Deglutition = swallowing
 Oropharynx and Laryngopharynx are common passage ways for
food and air
 Pharynx contains stratified squamous epithelium

24. OESOPHAGUS
 Swallowed food passes through epiglottis present behind the
tongue direct the food into oesophagus & prevent the
larynx.
 Approximately 20 cm long.
 Esophageal glands – produce mucus to lubricate bolus
 Esophageal sphincter – prevents backflow into oral cavity
 Cardiac sphincter- prevents backflow into esophagus

25.  Functions include
1. Secrete mucus
2. Moves food from the throat to the stomach using muscle
movement called peristalsis
 If acid from the stomach gets in here that’s heartburn.

26. DIGESTIVE PROCESSES IN THE MOUTH, PHARYNX, &
ESOPHAGUS
 Mouth processes
 Ingestion
 Mechanical digestion (e.g. salivary amylase)
 Initiation of Propulsion
 Mastication: chewing
 Pharyngeal processes
 Deglutition = swallowing
Voluntary Buccal phase
Involuntary Pharyngeal-Esophageal Phase
 Esophageal processes
 Peristalsis (rhythmic contractions, involuntary)

29.  J-shaped muscular bag that
stores the food you eat,
breaks it down into tiny
pieces.
 Mixes food with Digestive
Juices that contain enzymes
to break down Proteins
and Lipids.
 Acid (HCl) in the stomach
Kills Bacteria.
 Food found in the stomach
is called Chyme.

31. MICROSCOPIC ANATOMY OF THE STOMACH
 Simple columnar epithelium – contains gastric
pits that secrete gastric juices
 Goblet cells – secrete mucus that coats stomach
and prevents it from being digested itself
 Parietal cells – secrete hydrochloric acid
(converts pepsinogen into pepsin) and intrinsic
factor (necessary for absorption of vitamin B12)
 Chief cells – secrete pepsinogen which is
converted to pepsin to aid in protein digestion

32.  Enteroendocrine cells – release hormones such as:
 Histamine, Serotonin, Gastrin, Endorphins, and
Somatostatin
 Histamine
- activates parietal cells to release HCl
 Serotonin
- contraction of stomach muscle
 Gastrin
- gastric glands to increase secretion
 Endorphins
- natural opiates
 Somatostatin
- sympathetic n.s.
- inhibits gastric secretion
- inhibits gastric emptying

33. GASTRIC MOTILITY AND EMPTYING

34. CHEMICAL DIGESTION OF FOOD
Stomach ---Gastric juice
Digestive
juices &
enzymes
Carbohydrates Proteins Fats
Pepsin
Renin
Gastric
lipase
No action
Proteins peptones
Casein paracasein Fats Fatty acids &
glycerol

36.  Small intestines are roughly 7 meters long
 Lining of intestine walls has finger-like projections called villi,
to increase surface area.
 The villi are covered in microvilli which further increases
surface area for absorption.
 Nutrients from the food pass into the bloodstream through the
small intestine walls.
 Absorbs
 80% ingested water
 Vitamins
 Minerals
 Carbohydrates
 Proteins
 Lipids
 Secretes digestive enzymes

38. MICROSCOPIC ANATOMY OF SMALL INTESTINE
 Villi: fingerlike projections that increase the surface area of
the SI.

39. Intestinal juice
Digestive
juices &
enzymes
Carbohydrates Proteins Fats
Peptidase
Sucrase
Maltase
Lactase
Enteric
lipase
Disaccharides
Sucrose Glucose +
Fructose
Maltose Glucose +
Glucose
Lactose Glucose +
Galactose
Polypeptides
amino acids
Emulsified fats
fatty acids & Glycerol

41.  It is leaf shaped & located just
below the stomach.
 It secrets pancreatic juices.
Pancreatic juice
Digestive
juices &
enzymes
Carbohydrates Proteins Fats
Trypsin &
Chymotrypsin
Pancreatic
amylase
Pancreatic
Lipase
Starch
Disaccharides
Peptones Poly-
peptides
Fats fatty acids &
glycerol

43. •Produces digestive enzymes to digest fats, carbohydrates
&Proteins
•Regulates blood sugar by producing insulin

46.  Largest gland in human body
 It is reddish brown in color
 It secrets bile which breakdown fats.
 Bile is stored on gall bladder.
 filters out toxins and waste including drugs and alcohol and
poisons.
Functions of Liver
•Secretion of bile
•Glycogenic functions
•Formation of urea
•Desaturation of fats
•Functions related to blood
•Maintainace of body temperature
•Excretion of toxic substances

49.  Stores bile from the liver, releases it into the small intestine.
 Fatty diets can cause gallstones
Gall bladder
Digestive
juices &
enzymes
Carbohydrates Proteins Fats
Bile
Bile salts
(No enzyme)
Umemulsified fats
Emulsified fats

51.  The undigested & unabsorbed food enters into large
intestine.
 It is wider than small intestine, about 1.5 cm in length.
 Appendix: small structure containing lymphoid tissue;
small immune function
 Once the undigested food enters into large intestine, it
absorbs water & some salts from it & passed the
remaining waste into the rectum.

53.  Functions of Large intestine
 Reabsorption of remaining water and
electrolytes
 Production and absorption of Vitamins
B and K
 Elimination of feces

54.  Semisolid faecal matter remove from the anus.

55. BASAL METABOLIC RATE-BMR
 “The minimum energy requirement per day is called
as the Basal Metabolic Rate(BMR)”.
 This is the rate at which the sum of the metabolic
processes takes place, when an individual is at rest &
has eaten no food for 12 hrs.
 The normal BMR values are,
 Men ---170kJ/m2/hr
 Women ---155 kJ/m2/hr.

58. Digestive juices
Gastric Juice Intestinal Pancreatic Bile
Volume 1.5 to 2.5 lit/day 2 to 3 lit/day 600 to 800 ml/day 800 to 1000
ml/day
pH 1.6 to 3.2 7.5 to 8 4.5 to 7.0 6.8 to 7.7
Composition of juices
Gastric juices Intestinal juices Pancreatic juices Bile juice
Water
Mineral Salts
Hydrochloric
acids
Pepsinogen
Renin
Water
Mineral Salts
Entero Kinase
Amylase
Peptidase
Lipase
Sucrase
Maltase
Lactase
Water
Mineral Salts
Trypsinogen
Chymotrypsinogen
Amylase
Lipase
Water
Mineral Salts
Sodium Taruocholate
Sodium Glycocholate
Biliverdin
Bilirubin
cholesterol

59. IMP. DEFINITIONS
 Ingestion:- The process of taking food into the body by
swallowing or absorbing it.
 Assimilation:- absorbed food is used by various cell
components.
 Egestion:- Removal of undigested and unabsorbed food
from the GI tract through the anus.