Human Digestive System - Anatomy & Physiology - B.Pharm & Pharm.D - GIT & Its Accessory Organs

1. DIGESTIVE SYSTEM
By – Dr.S.Kameshwaran

3.  Digestive system describes alimentary
canal and its accessory organs
Digestion
“It is a processes that prepare food eaten in
the diet for absorption”
 System begins at the mouth passes
through thorax, abdomen, pelvis and ends
at the anus.
 Digestive process gradually breakdown the
food eaten until they are in the form
suitable for absorption

4. ACTIVITIES OF DIGESTIVE
SYSTEM
1. Ingestion – TAKING OF FOOD IN TO ALIMENTARY
CANAL (Eating/ Drinking)
2. Propulsion: Mixes & moves the content along the
alimentary canal
3. Digestion
A. Mechanical breakdown – fragment food into
smaller particles (Mastication) (Chewing)
B. Chemical Digestion of food into small molecules
by enzymes present in secretions produced by
glands and accessory organs of digestive system
 Mouth = carbohydrates
 Stomach = Proteins
 SI = CH, Proteins, fats, nucleic acids

5. 4. Absorption – digested food contents
pass through the walls of alimentary
canal in to blood and lymph
capillaries for circulation and use by
body cells
5.Defecation – indigestible un
absorpable food substance excreted
form ali canal as feces by the process
of defecation.

6. Anatomy
Alimentary canal
 Also known as Gastrointestinal tract (GI)
 Long tube through which food passes
 Commences at mouth terminates at anus
 Various organs includes:
Mouth  pharynx 
esophagus  stomach 
small intestine  large
intestine

8.  Accessory digestive organs
 Various secretion are poured in the
alimentary tract
Eg: Gastric juice secreted by glands in the
lining of stomach
 Some by glands situated outside the
tract
 Three pairs of salivary glands
 The pancreas
 The liver and biliary tracts

9. LAYERS OF GIT
The GI tract contains four layers:
 the innermost layer - mucosa,
 Submucosa,
 followed by muscularis propria and
 the outermost layer -adventitia.
 The structure of these layers
varies, in different regions of
the digestive system,
depending on their function.

11. MUCOSA (Mucus membrane):
 Innermost membrane
 Contains a lining columnar epithelium, including
glandular tissue
 Glandular tissue secretes mucus – lubricates the inner
line,
 Forms physical barrier that protects them from the
damaging effect of digestive enzymes
 Consist of an underlying layer of loose connective
tissue called the lamina propria - which provides
vascular support for the epithelium
 Finally a thin double layer of smooth muscle is often
present - the muscularis mucosa for movement of the
mucosa.

12. SUB MUCOSA:
 This layer consist of loose connective tissue,
contains collagen and some electric fibers
 Helps in binding of muscle layer to mucosa
 Contains sympathetic and parasympathetic
nerve supply
 Contains larger blood vessels

13. Muscularis propria
 smooth muscle layer.
 There are usually two layers;
 the inner layer is circular, and the outer layer is
longitudinal.
 These layers of smooth muscle are used for
peristalsis (rhythmic waves of contraction),
 Helps to move food down through the gut.
 Myenteric plexus – the sympathetic and para
sympathetic nerve innervation

15. Adventia layer (or serosa)
 It is also called as serosa layer
 Outermost layer
 blood vessels, lymphatics and nerves.
 Made up of loose connective tissue
 This connective tissue covered by the visceral
peritoneum.
 Which reduces the friction during movements

16. Organs of digestive system:
 Salivary glands
 Pharynx
 Esophagus
 Stomach
 Small Intestine
 Large Intestine
 Rectum
Accessory digestive organs:
liver,
gallbladder,
pancreas

17. Mouth
 Oral cavity:
mechanical, chemical digestion
 Mastication:
teeth chew food
 Tongue
mixes food + saliva

18.  The mouth or oral cavity is bounded by muscles
and bones
 Oral cavity is lined throughout with mucous
membrane
 It contains stratified squamous epithelium
containing small mucus secreting glands
 The uvula is a curved fold of muscle covered
with mucous membrane
 Hanging down from the middle of the soft palate

19. Teeth:
Food is chewed with the help of teeth to breakdown
in to smaller particles – mastication
Teeth are hard calcified structures that help in
mastication
Teeths are embadded in the sockets of the
mandible and the maxilla
Babies are born with two sets
deciduous teeth (baby/ Milk teeth) &
Permanent teeth (adult teeth)

20. DECIDUOUS TEETH
 There are temporary teeth
 10 in each jaw
 They begin to erupt at about 6 months of age
 Should all be present by 36 months
 The permanent teeth begin to replace the
deciduous teeth in the 6 th year
 Consisting 32 teeth is usually completed by the
21 st year (16 in each jaw)

21.  STRUCTURE:
 Basic structure of tooth
 Crown – visible part
 Root – part with in gum
 Crown – is covered with enamel (highly
mineralised tissue) + dentin
 Root – is covered with cementum (Hard
connective tissue)
 The part connect the crown & root portion of
tooth known as neck

23. CROWN:
 The crown contains enamel & dentin
ENAMEL:
 Hardest and most mineralized part of human body
 It form outer covering of the tooth
 Calcium phosphate is the major mineral present
DENTIN:
 It is a hard connective tissue just like a bone
 It present behind the enamel
 Accounts for largest portion of tooth
 It surrounds the pulp (soft CT contains BV & nerve
innervating to tooth
ROOT
 Root covered with cementum (Hard connective tissue)
 All blood vessels and nerves enters in to pulp through
the root of teeth

24. PERMANENT TEETH:
INCISORS – 2-2
CANINE – 1-1
PREMOLARS – 2-2
MOLARS – 3-3
DECIDUOUS TEETH
INCISORS – 2 -2
CANINE – 1 - 1
MOLARS -2 – 2
Functions:
INCISORS - cutting teeth used for biting of pieces of food
CANINES – conical shaped teeth – grasping & tearing the
food
PREMOLARS – grinding the food (ab in children) (after 9 yrs)

25. SALIVARY GLANDS:
 Oral cavity contains three main pairs of salivary
glands
 Their secretions termed as saliva
 Which helps to moisten the oral cavity & bolus
formation
 Saliva is the mixture of mucus & serous (watery type)
 Every day 1.5 lit of saliva produced
Types of salivary glands:
 The parotid glands
 The submandibular
 The sublingual glands
 Apart from that 600-1000 are present in the oral cavity
– contribute to small amount of hole saliva production

26. PAROTID GLAND:
 Largest salivary gland
 Located immediately anterior to the ear on
either side
 It releases serous secretion – via parotid
duct - Opens at second upper molar tooth of
oral cavity

27. THE SUBMANDIBULAR:
 This is second largest gland – located below the
mandible
 It produce mixed secretions – releases via
submandibular duct - Opens in the mandibular
region of the oral cavity (adjacent to the frenulum
of the tongue)

28. The sublingual glands
 This is the smallest major salivary gland
 Located in the floor of the mouth
 It produces mixed secretions
 It does not have specialized ducts -ductless
glands
 It releases secretions directly in to the floor of
mouth via 10-12 small ducts

29. COMPOSITION OF SALIVA:
 Water – 99%
 Electrolytes (Sod, Pot, Cal, Mag, Bicar, Phosp)
 Proteins
 Mucosal glycoprotein
 Trace of albumin
 Polypeptides & Oligopeptides
Functions of saliva:
 Chemical digestion of polysaccarides
 Lubrication of food
 Cleaning and lubricating mouth
 Non specific defence – ig & lysosyme combat microbs
 Taste

30.  PHARYNX:
 It is a funnel shaped tube
 It is made up of skeletal muscle – lined with
mucus membrane
 Divided in to
 Nasopharynx
 Oropharynx
 Laryngopharynx
Nasopharynx:
 Contributes to respiration
Oropharunx & Laryngopharynx
 Contributes to respiratory as well as digestive
functions

31.  Oropharynx & laryngopharynx is common
passage way for both respiratory and
digestive system
 food – oral – pharynx – esophagus
Pharynx walls
3 layers of muscles:
Mucosa – stratified squamous epithelium
Middle – fibrous connective tissue- BV, lymph,
Nerves
Outer layer – number of involuntary muscle –
swallowing

32. OESOPHAGUS:
 Also known as food
pipe
 It is a long muscular
tube
 About 25 cm long – 2
cm in dia
 Lies in the thorax in
front of vertebral
column
 Behind trachea and
heart
 Which joins pharynx

34.  It curves upwards before opening in to the
stomach
 Sharp angle – prevents regurgitation (back
flow ) of gastric contents to the
oesophagus
 The upper and lower ends of the
esophagus are closed by sphincter
 Cricopharyngeal/ upper oesphagel
sphincter prevents air passing in to the
oesophagus

35. Anatomy of esophagus:
 Mucosa
 Sub mucosa
 Muscularis propria
Functions:
 Functions of mouth - pharynx - oesophagus
 Formation of bolus
 Swallowing (deglutition)
 A wave of peristalsis is stimulated when the
bolus is present in the pharynx – bolus propelled
to the stomach via esophagus

36. STOAMCH:
 It is a J shaped dilated portion of alimentary tract
 It is a hollow, muscular, bag like structure
 The second phase of digestion takes place in the
stomach
 Stomach size varies with the volume of food it contains
 1.5liter for an adult
Structure of stomach:
 Continues with oeophagus at cardiac sphincter
 Ends with duodenum at pyloric sphincter
 It has two curvatures
 Lesser curvature is short
 Lies on the posterior surface of the stomach
 It is the downward continuation of posterior wall of
oesophagus
 Just before the pyloric sphincter it curves uwpard o
give J shape

38.  Greater curvature – outer portion of stomach
 Stomach – divided in to 3 regions
FUNDUS – BODY – PYLORUS
Fundus:
 The dome shaped part is formed by the upper
curvature of the stomach
Body
 The central region of the stomach
Pylorus:
 It is the lower region of the stomach, that
continues in to the duodenum

40.  At the distal end of pylorus – pyloric
sphincter
 Pyloric sphincter – Guarding the opening
between stomach and duodenum
 When stomach is inactive – sphincter relaxed
and open
 When stomach contains food – sphincter is
closed

41. WALLS OF THE STOMACH
The stomach has 4 layers
 SEROSA/ VISCERAL
PERITONEUM
 MUSCLE LAYER
Outer Longitudinal layer
Middle circular layer
Inner oblique layer
 SUBMUCOSA

43.  GASTRIC JUICE:
 About 2 liters of gastric juice are secreted daily
by specialized secretory glands present in the
mucosa
Composition of Gastric Juice :
 Water
 Mineral salts
 Mucus – by mucus membrane
 HCL – by Parietal cells in gastric glands
 Intrinsic factor – by Parietal cells in gastric
glands
 Inactive enzyme precursor - pepsinogen

44. FUNCTIONS OF GASTIC JUICE:
WATER:
 Further liquefies the food swallowed
HCL:
 Acidifies the food and stop the action of salivary
amylase
 Kills ingested microbs
 Provide acid environment needed for the action of
pepsins
PEPSINOGENS:
 Pepsinogen activated to pepsin by HCL & by pepsin
already present in the stomach
PEPSIN
 Pepsin is more active at ph between 1.5 - 3.5
 digest the proteins

45. INTRINSIC FACTOR:
 It is a protein
 Important for absorption of vit B12 from ileum
(def: pernicious anaemia)
MUCUS:
 Prevents mechanical injury to stomach

46. SECRETION OF GASTRIC ACID:
 HCL in stomach with out food - Fasting juice
 Secretion reaches max level 1 hour after
meal
 decline to fasting level after 4 hour
 Acid production is regulated by the
parasympathetic nervous sytem
3 PHASES OF GASTRIC ACID SECRETION:
 CEPHALIC PHASE
 GASTRIC PHASE
 INTESTINAL PHASE

47. CEPHALIC PHASE:
 The rate of secretion of gastric juice is high
(around 500ml/h) in this phase
 Flow of juice before food reaching the
stomach
 Occurs due to reflex stimulation of vagus
nerves initiated by sight, smell, taste or
thought of food
 Cerebral cortex and appetite centres of
hypothalamus sends the neurogenic signal
 Impulses from hypothalamus reaches the
stomach via vagus nerve - and stimulate the
secretions of
 HCL – secreted from parietal cell

48. GASTRIC PHASE:
 Rate of secretion of gastric juice in this
phase is lesser (200ml/h)
 This phase begins as soon as the food
enters the stomach
 G cells in the pylorus & duodenum – secrete
gastrine – passes directly in to the
circulating blood
 Gastrine present in blood supplies to
stomach – stimulate the gastric glands to
produce more gastric juice
 Gastrine secretion stopped when the pH in
pylorus falls less than 3

49. INTESTINAL PHASE:
 Partially digested stomach contents (Chyme)
– reach small intestine – secretin &
cholecystokinin are produced by endocrine
cells of intestinal mucosa
 They slow down the secretion of Gastric
juice & reduce gastric motility
 Process in more faster if meal contain high
fat
 CH Leaves stomach – 23 hours
 Protein meal – longer
 Fatty meal – remain longest

50. HCL ACID SECRETION

51. PEPSIN ROLE IN PROTEIN DIGESTION:
 Pepsinogen is secreted by the chief cells
present in the gastric glands
 Pepsinogen is converted in to pepsin by HCL
acid and previously formed pepsin
 At pH 3 or less than that the pepsin exerts
maximum enzymatic activity
 It breaks the protein molecule in to smaller
peptide chains by acting as catalyst

52. FUNCTIONS:
 Break downs larger molecules in to smaller
 2-3 liters of gastric acid secreted per day,
high amount secreted in evening
 Pepsinogen – converted in to pepsin – helps
in protein digestion
 Intrinsic factor produced by parietal cells of
stomach is essential for vit B12 absorption

53. SMALL INTESTINE:
 Continue with stomach @ pyloric sphincter
 Present between the stomach and small intestine
 2.5 cm dia, little over 5 meter long
 Leads in to large intestine @ ileocaecal valve
 Lies in the abdominal cavity
 Chemical digestion of food is completed and
absorption of most nutrients
 Absorption of 90% of nutrients from digested food
 Internal wall is folded to form villi (finger like
projections) absorb all the nutrients

54. Structurally small intestine can be divided
in to
3 parts
 DUODENUM
 JEJUNAM
 ILEUM

55. DUODENUM:
 It is the initial and smallest part of small intestine
 25 cm long
 It is a hollow tube like structure connecting stomach
to jejunum
 Curves around the head of pancreas
 Majority of the chemical digestion takes place in
duodenum
 Secretions of gall bladder and pancreas merge in a
common structure – hepato pancreatic ampulla
 Enters the duodenum @ duodenal papilla –
gaurded by – hepato pancreatic sphincter
(Sphincter of oddi)

58. JEJUNAM
 It is a part of small intestine
 Present between duodenum & ileum
 2 meter long
ILEUM
 It is the lower end of the small intestine
 Continues in to the large intestine to form the caecum
 3 meters long,
 The diameter of intestinal lumen decreases towards
the ileum
 ends at ileocaecal valve
 Controls flow of material from ileum to caecum (1st
part of Large intestine) prevents back flow

59. STRUCTURE OF SMALL INTESTINE:
 Wall of SI – 4 layers
 Some modifications only in the peritoneum &
Mucosa
MUCOSA :
 Surface of SI mucosa is greatly increased by
permanent circular folds,
 VILLI – finger like projections of mucosal layer
 0.5 – 1 mm long
 Coverings consist of columnar epithelial cells
with tini micro villi
 micro villi - 1 micro meter long

62. INTESTINAL JUICE:
 1-2 liters of intestinal juice secreted/day
 Present in the form of clear yellow fluid
 Consist of water, mucus and mineral salts
 It is slightly alkaline (basic) in nature pH 7.6

63. CHEMICAL DIGESTION IN SI
 When food present in the small intestine
Cholecystokinin is produced in the small intestine
 which promotes the release of Pancreatic enzymes
and bile from the gallbladder in to the small intestine
 Proteins are degraded into small peptides and amino
acids
 Lipids (fats) are degraded into fatty
acids and glycerol,
 Pancreatic lipase & bile - breaks
down triglycerides into free fatty acids
and monoglycerides
 Pancreatic amylase breaks down some
carbohydrates into oligosaccharides

64. Functions:
 Carbohydrate metabolism
 Lipid metabolism
 Protein metabolism
 Processing of drugs and hormones
 Excretion of bilirubin
 Synthesis of bile salts
 Storage
 Phagocytosis
 Activation of vitamin D

65. PANCREATIC JUICE:
 Secreted by exocrine pancreas
 Which enters the duodenum at the duodenal
papilla
It consist of
 Water
 Mineral salts
 Enzymes
Amylase, lipase, nucleases that digest
DNA & RNA
INACTIVE ENZYME PRECUROSORS
Tripsinogen

66. FUNCTIONS:
 Digestion of proteins
 Digestion of CH
 Digestion of fats

67. LARGE INTESTINE:
 It is about 1.5m long
 Beginning at caecum & terminating at the
rectum and anal canal
 6.5cm diameter
 It forms an arch round the coiled up small
intestine
It is divided in to
 Caecum
 Colon
 Sigmoid colon
 Rectum

68. THE CAECUM:
 This is first part of large intestine
 It is a dilated region
 It has no digestive function
 Can cause significant problems when
inflamed
THE COLON:
 It has 4 parts has same structure and
function
 THE ASCENDING COLON
 THE TRANSVERSE COLON
 THE DESCENDING COLON

69.  THE ASCENDING COLON
 This passes upwards from he caecum to the level of
liver
 Where it curves to left at hepatic flexure to become
transverse colon
 THE TRANSVERSE COLON:
 This extends across the abdominal cavity in front of
the duodenum & the stomach
 Near to the spleen it forms splenic flexure and curves
downwards to become descending colon
 THE DESCENDING COLON:
 It passes down the left side of the abdominal cavity
 Curves towards the midline
 It known as sigmoid colon

71. THE SIGMOIDCOLON:
 This part describes as s shaped curve in the
pelvic cavity
 It continues downward to become the rectum
THE RECTUM:
 This is slightly dilated section of the large
intestine
 It is about 13cm length
 Leads from sigmoid colon
 Terminates at anal canal
THE ANAL CANAL:
 It is a short passage about 3.8cmlong in
adults

73.  The internal sphincter – contains smooth
muscles – under the control of ANS
 External sphincter – formed by skeletal muscles
– its under voluntary control.
 When individuals wants to defecate – they open
it up allowing evacuation of the bowel.
STRUCTURE:
 4 layers of tissue

74. SECRETIONS:
 Colon mucosa contains number of goblet cells –
secrete mucus – lubricate the colon walls
CONSTITUENTS OF FEACES:
 It is a semisolid brown mass
 Colour due to the presence of stercobilin (heam –
bilirubin – enters intestine – excreted in faeces
 Fibre
 Dead and live microbes
 Epithelial cells shed from the walls of the tract
 Fatty acid
 Mucus secreted by the epithelial lining of the large
intestine
 Mucus – helps to lubricate the faeces

75. FUNCTIONS OF LARGE INTESTINE
 Absorption – absorption of water by osmosis
until food content become semi solid mass
 Mineralsalts, vitamins and some drugs also
absorbed
MICROBIAL ACTIVITY:
 Large intestine contains certain types of
bacteria
 Which synthesis Vitamin k and folic acid
 Includes Escherichia Coli, Enterobacter
aergenes
 Streptococcus faecalis, Clastridium perfringens
 They are harmless in humans
 Become pathogenic if transferred to other part

76. Pancreas:
 It is an elongated digestive gland
 Pale gray gland
 12-15 cm long & 60gms weight
 Present in the abdominal cavity
 Consist of broad head a body and a narrow tail
 Head lies in the curve of duodenum
The exocrine pancreas:
 It contains large number of lobules made up of small
acini
 The walls of it consist of secretory cells
 Each lobule drained by small duct –unite to form
pancreatic duct – open to the duedenum

78.  Before entering in to deudenum it joins common
bile duct to form hepatopancreatic ampulla
 Opening is controlled by hepato pancreatic
sphincter (of oddi) at the duodenal papilla
THE ENDOCRINE PANCREAS:
 Contains specialized cells called pancreatic
islets
 It has no ducts - hormones diffuse directly in to
blood
 Secretes insulin & glucagon – maintains blood
glucose level

79. LIVER:
 Largest gland in the body
 Weighing about 1-2.3 kg
 Situated in the upper part of the abdominal cavity
 The liver is enclosed in a thin inelasstic capsule and
incompletely covered by a layer of peritoneum
 Folds of peritoneum form supporting ligaments that
attach the liver to the inferior surface of the
diaphragm
 Liver has 4 lobes
 Obvious Large right lobe
 Smaller wedge shaped left lobe
 Two others are caudate & quadrate lobes – in
posterior surface

81. THE PORTAL FISSURE:
 The part is posterior surface of the liver
where various structures enters and leave
the liver
 Portal vein, hepatic artery, nerve fibres,
hepatic ducts, lymph vessels

82. STRUCTURE:
 Lobes of liver made by functional units –
lobules
 Visible to the naked eye
 Hexagonal in outline formed by cuboidal
cells
 Hepatocytes arranged in a pairs of
columns radiating from a central vein

83.  The spacce between the two pairs of
columnar cell is – sinusoid
 The blood vessels are having incomplete
walls - - contents of blood mix and come in
to close contact with liver cells
 Kupffer cells (hepatic macrophages)
 Ingest and destroy the worn out blood cells
& foreign particles present in the blood
 Liver also secretes bile
 Bile canaliculi run between the column of
liver
 Each hepatocyte having one side sinusoid
and bile canaliculus on other side

84. FUNCTIONS OF LIVER:
 Carbohydrate metabolism
 Fat metabolism
 Protein metabolism
 Breakdown of erythrocytes & defense
against microbes
 Detoxification of drugs and toxic substances
 Inactivation of hormones
 Production of heat
 Secretion of bile
 storage

85. COPOSITION OF BILE:
 500 – 1000 ml of bile is secreted by liver
Bile consist of
 Water
 Mineral salts
 Mucus
 Bile pigments - bilirubin
 Bile salts
 Cholesterol
Functions of bile
 Fat digestion
 Excretion of bilirubin

86. GALL BLADDER:
 It is a pear shaped sac attached to the posterior surface
of the liver by connective tissue
 It has a fundus/ expanded end
 A body or main part and a neck
 Which is continues with the cystic duct
 Structure is same like that of GIT with small
modifications In peritonium muscle layer & mucus
membrane
FUNCTIONS OF GALLBLADDER:
 Reservoir for bile
 Concentration of the bile increases10 – 15 folds by
absorbing the water through the wall of the gallbladder
 Release of stored bile

88. DISEASE OF MOUTH:
 Mouth ulcers
 Acute Gingivities (inflammation of gums)
 Squamous cell carcinoma
CONGENITAL DISORDER:
 Cleft palate and cleft lip
DISORDERS OF SALIVARY GLAND:
 Mumps – viral disease at parotid gland
 Tumor of salivary glands
 Sialolithiasis – stones in the salivary duct

89. DISORDERS OF THE PHARYNX:
Pharyngitis – infected and swellon
Tonsillitis – inflammation in tonsils
DISORDERS OF OESOPHAGUS:
GERD – Gastro Esophageal Reflex Disease
Achalasia – esophagus empties slowly
DISORDERS OF STOMACH:
Gastritis – stomach lining becomes inflamed,
irritated, or eroded
Gastric Ulcer – condition – sore appear in the inner
lining of the stomach

90.  DISORDERS OF INTESTINE:
 Appendicitis – Inflammation in appendicitis
and filled with pus
Crohns disease
“Condition in which the GIT become
inflammed – progress to all layers of GIT”
Symptoms:
 Chronic diarrhoea
 Loss in weight
 Fever
 Pain and tenderness in abdomen
 Rectal bleeding

91. Disorders of pancreas:
 Pancreatitis – inflammation in pancreas
Zollinger – Ellison Syndrome
 It is a rare disorder
 Tumours and ulcer in the digestive system
 Less than 3 peoples affected in million peoples
 Due to the tumor increase in gastrin production which
increases gastric acid secretion
Disorders of Liver:
 Liver cirrhosis – Loss of liver cells, irreversible scarring
of liver cells
 Hepatitis – liver inflammation
Disorders of gall bladder:
 Gall stones – cholelithiasisi
 Cholecystitis – inflammation in gallbladder

92. Movements of GIT:
 Also known as Gastro intestinal motility
 Involuntary mobility of human tubular organs is
termend as Motility
 There are two main movements present in the
GIT
Propulsion movement & Mixing Movements
1. Propulsion movement
 Invloved in the movement of chyme through the
digestive tract at a rate proportional to the
absorption and digestion rate
 The propulsion movement is called as
PERISTALSIS

93. MIXING MOVEMENTS:
 It involved in constant mixing of chyme to expose all the
nutritionally important components to the enzyme
 So the components come in to contact with the lining of
intestine where it needs to be absorbed – absorption of
nutrients
MASTICATION:
 “IT IS THE PROCESS BY WHICH THE LARGER FOOD
PARTICLES BREAKDOWNS IN TO SMALLER ONES BY
THE PREMOLAR AND MOLAR TEETH'S”
 Previously the food is tore and cut by the incisors and
canines
 Temporalis, masseter, medial prerygoid & lateral
pterygoid are the muscles involved in the mastication
process

94. SWALLOWING/ DEGLUTITION
“passage of food from mouth to stomach”
 This process involved in mouth, pharynx &
oesophagus
 There are 3 main phase in swallowing
Voluntry phase
 passage of bolus in to oropharynx
Pharyngeal Phase
 involuntary passage of bolus from pharynx to
esophagus
Oesophageal Phase
 Involuntary passage of bolus from esophagus to
stomach

95. STOMACH MOVEMENTS:
Stomach filling
 Food present in the stomach increases the
stomach volume
 The pressure with in the stomach remain
unchanged untill the volume reaches maximum
capacity
 Occur due to the stretching of smooth muscle with
out increase in tension

96. Mixing stomach contents
 The food and secretions of stomach glands
are mixed to form – chyme
 Mixing wave (peristalsis) like contraction
produced in the stomach body for every 20
seconds towards the pyloric region
 Fluid part of the Chyme pushed towards the
pyloric region while the solid part pushed
back towards stomach body
 This process repeats until food mixes with
secretions fully

97.  STOMACH EMPTYING
 The food remains in the stomach depends on the
type and volume of food
 After having meal stomach empties with in 3-4
hours
 Each peristaltic movement pushes small amount
of chyme in to the duodenum through pyloric
sphincter opening - pyloric pump

98. MOVEMENTS OF SMALL INTESTINE:
 Small intestine carry out mixing and propulsion
of chyme – occurs due to the segmental and
peristaltic contractions of the smooth muscles
 Segmental contractions – initiate mixing of the
intestinal contents
 Peristaltic contractions initiate propelling the
content further along the digestive tract
 The rate at which the contraction move is about
1cm/min
 The contractions faster at proximal end slower
at distal end
 The intestinal motility is regulated by
mechanical, chemical stimuli also by

99. MOVEMENT OF LARGE INTESTINE:
 Peristaltic contraction moves the chyme along
the ascending colon
 In transverse colon and descending colon
undergo strong peristaltic contraction – called
mass movements
 Which occurs atleast 3-4 times a day
 A mass movement moves the colon content
around 20cms
 Pushing the content of the colon towards the
anus
 Defecation reflex – stimulated by rectal wall –
when it is distended by faeces
 Which weakly contract rectum - relaxes the

100.  External anal sphincter – made up of skeletal
muscle – controlled by cerebrum – relaxes to
expel the faeces.
DEFECATION:
 Voluntary movement to expel faeces
 Contraction of abdominal muscles – to force
the colon contents – expel through anal canal.

101. DIGESTION
“The process of breakdown of food into
smaller molecules that can be absorbed in
the blood circulation “
 There are two types of digestion
 Mechanical Digestion – breakdown of food in
to smaller molecules
 Chemical Digestion – Breakdown of chemical
covalent bonds in organic molecules
(CH,PTN, FAT)
 The process by which the digested nutrients
reaches the blood circulation is called as
absorption

102. DIGESTION & ABSORPTION OF
CARBOHYDRATES:
 Carbohydrates consist of Polysaccharides,
disaccharides & Monosacchardies
 Digestion invloved in breakdown of
 Polysaccharides in to smaller chains in to
Disaccharides then further breakdow in to
Monosacchardies
 Digestion of CH begins at the oral cavity
 Partial digestion of starch by salivary
amylase
 Small amount of CH digested in the
stomach by gastric amylase & Gelatinase

103.  Digestion continues in the small intestine by
pancreatic amylase
 Disaccharides are converted in to
monosaccharides by the enzyme
disaccharidases bound to microvilli of the
intestinal epithelium
 Monosaccharides (glucose & galactose) are
taken up into the intestinal epithelium cells via –
secondary active transport by sodium ion
gradient
 Monosaccharides (Fructose) – taken up by
falicitated diffusion
 Monosaccharides enters in to the capillaries of
intestinal villi are carried via hepatic portal

104. DIGESTION & ABSORPTION OF LIPIDS
 Lipids are insoluble or slightly soluble in water
 They includes triglycerides, phospholipids,
cholesterol, steroids and fat soluble vitamins
 Triglycerides consist of covelently bound 3 fatty acids
and a glycerol molecule
 Lingual lipase secreted in the oral cavity digest minor
amount of lipids
 Emulsification – conversion of larger lipid droplets in
to smaller ones with the help of bile salts
 Then the lipid molecules are digested by the lipase
from pancreas
 Lipids are digested in to free fatty acids, glycerol,
cholesterol and phospholipids

105.  After the digestion the droplets of fatty acids
aggregated by the bile salts to form micelles
 The micelles attach to the plasma memebranes of
intestinal epithelial cells – Fatty acid, glycerol pass in
to the cell via simple diffusion
 With in the cell the fatty acid and glycerol converted in
to triglyceride – by protein coating they converted in
to chylomicrons – enters in to the circulation

106.  DIGESTION AND ABSORPTION OF PROTEIN
 Protein breakdown in to amino acids
 Actively transported in to various body cells
 The transport of amino acid is stimulated by Growth
hormone & insulin
 Stomach secrete pepsin – cleaves the covalent bonds of
proteins –in to smaller polypeptide chain
 10-20 % of ingested protein is digested by gastric pepsin
 Proteolytic enzyme form pancreas carry out the further
digestion
 PEPTIDASE bound to the microvilli of small intestine
breakdown the protein in to dipeptides, tripeptides & amino
acids
 dipeptides, tripeptides enters the intestinal epithelial cells

107.  More amount of amino acids enters in to the
intestinal epithelium when it is in the
dipeptides, tripeptides
 With in the cell dipeptides, tripeptides broken
down by dipeptidases and tripeptidases in to
amino acids
 They moves from intestinal epithelial cells in to
liver by hepatic portal vein