The digestive system includes the organs of the alimentary canal and accessory structures. The alimentary canal forms a continuous tube that is open to the outside environment at both ends. The organs of the alimentary canal are the mouth, pharynx, esophagus, stomach, small intestine, and large intestine.

1. ANATOMY AND PHYSIOLOGY OF DIGESTIVE SYSTEM

2. ANATOMY AND PHYSIOLOGY OF
DIGESTIVE SYSTEM
Submitted to: Submitted by:
Dr. Pallavi Pathania Nisha Kumari
Associate Professor M.Sc. Nursing 1st year
(Medical Surgical Nursing) Shimla Nursing College
Shimla Nursing College

3. INDEX
SR.
NO.
CONTENT
1 Gastrointestinal Tract
2 organs of digestive system
3 Another name of digestive system
4 Primary organs of digestive system
5 Name of Accessory digestive organs
6 Layers of Gastro Intestinal wall
7 Digestion
8 Movements in digestive system
9 Mouth

4. SR.
NO.
CONTENT
10 Tongue
11 Teeth
12 Salivary glands
13 Pharynx
14 Oesophagus
15 Stomach
16 Pancreas
17 Liver
18 Gallbladder

5. SR.
NO.
CONTENT
19 Small intestine
20 Large intestine
21 Rectum
22 Anus
23 Gut flora
24 Physiology of digestion
25 Function of GI Tract
26 Conclusion

6. GASTROINTESTINAL TRACT (GIT)
 The gastrointestinal tract is an organ
system within humans and other
animals which takes in food, digests it
and absorb energy and nutrients, and
expels the remaining waste as feces.

7. CONTD…
 The bodily system concerned with the
ingestion, digestion, and absorption of food
and the discharge of residual wastes and
consisting of the digestive tract and accessory
glands (such as the salivary glands and the
pancreas) that secrete digestive enzymes.

8. ORGANS OF DIGESTIVE SYSTEM
Mouth
Salivary
glands
Pharynx
esophagus
Stomach
Pancreas

9. CONTD…
Liver
Gallbladder
Small intestine
Large intestine
Rectum
Anus

11. DIGESTIVE SYSTEM
 Digestive system also called digestive tract, digestional
tract, GI tract, GIT, gut, or alimentary canal.

12. PRIMARY ORGANS OF THE DIGESTIVE SYSTEM
 Mouth.
 Pharynx.
 Esophagus.
 Stomach.
 Small Intestine.
 Large Intestine.
 Rectum.
 Anus

13. ACCESSORY DIGESTIVE ORGANS
 Liver
 Gallbladder
 Pancreas.
 Salivary gland

14. LAYER OF GASTROINTESTINAL WALL
 Four main layers. From inside (the lumen) to outside the
are:
1. Mucosa
2. Sub mucosa
3. Muscularis (external)
4. Serosa ( visceral peritoneum)

15. MUCOSA ( VISCERAL PERITONEUM)
 It is the innermost, moist, epithelial membrane
that lines the entire digestive tract.
(1) It secretes mucus, digestive enzymes,
and hormones.
(2) Absorbs digestive end products into the
blood.
(3) Protects against infectious disease.

16. CONTD…
 Consists of a lining epithelium, a lamina propria, and a
Muscularis mucosa.
 Epithelium - simple columnar epithelium and goblet cells
 Lamina propria – it is large layer of connective tissue.
Which separate innermost layer of epithelial cell from a
layer of muscle tissue called muscularis mucosa
 Muscularis mucosa - thin layer, produces local movements
of the mucosa.

17. SUB MUCOSA
 It is a moderately dense connective
tissue layer containing blood and
lymphatic vessels, lymphoid follicles,
and nerve fibers.

18. MUSCULARIS EXTERNA
 It typically consists of smooth muscle and is
responsible for peristalsis and segmentation.
 Contains the myenteric plexus of Auerbach, the
other major intrinsic nerve plexus. Located between
the two layers of smooth muscle, controls motility of
the Gastro Intestinal tract.

19. SEROSA
 It is the protective outer layer of the intraperitoneal organs, is the
visceral peritoneum.

20. DIGESTION
 Digestion is the process by which
insoluble food, consisting of large
molecules is broken down into soluble
compounds
 Digestion starts at the mouth and ends at
the anus.

21. FOOD IS BROKEN DOWN BY TWO ACTIONS
2. CHEMICAL
1. PHYSICAL
/MECHANICAL

22. 1. PHYSICAL DIGESTION BY
 Teeth
 Peristalsis of the alimentary canal
 Chewing

23. 2. CHEMICAL DIGESTION BY:
 Enzymes
 Digestive enzymes are the chemicals that break large insoluble
food molecules into smaller soluble molecules.

24. PHASES OF DIGESTION
1. Ingestion
2. Digestion
3.Absorption into the
bloodstream
4. Egestion

25. CONTD…
 The esophagus, stomach, small intestine, and large intestine
are the main regions of the GI tract. They are separated from
each other by special muscles, called sphincters, which
regulate the movement of ingested material from one part to
another. Each part of the GI tract has a unique function to
perform in digestion, and each has a distinct type of motility
and sensation.

26. MOVEMENTS IN ESOPHAGUS
 The function of the esophagus is to
transport the ingested material from the
pharynx to the stomach by peristaltic
waves.

28. PERISTALSIS MOVEMENTS
 Peristalsis is a series of organized muscle
contractions that occur throughout the digestive
tract. (that propels foodstuffs distally through the
esophagus and intestines).
 The synchronized contraction of the esophagus,
stomach, and intestine is called peristalsis

29. CONTD…
 Peristalsis is a series of wave- like muscle contractions that moves food to
different processing stations in the digestive tract.
 The process of peristalsis begins in the esophagus when a bolus of food is
swallowed.
 It was first described by Bayliss and Starling in 1899 as a type of motility in
which there is contraction above and relaxation below a segment being
stimulated.

30. CONTD…
 The strong wave like motions of the smooth muscle
in the esophagus carry the food to the stomach ,
where it is churned into a liquid mixture called
chyme.
 Peristalsis continuous in the small intestines where it
mixes and shifts the chyme back and forth, allowing
nutrients to be absorbed into the bloodstream through
the small intestine walls.

31. CONTD…
 Peristalsis concludes in the large intestines where water from the undigested
food material is absorbed into the bloodstream.
 While peristalsis involves one-way motion in the caudal direction, segmentation
contractions move chyme in both directions, which allows greater mixing with
the secretions of the intestines.

32. TYPES OF PERISTALSIS MOVEMENT
 Primary peristalsis: Triggered by the
swallowing center in the brain stem and the
contraction wave travel at speed 2cm/s.
 Secondary peristalsis: Induced by
esophageal distension from retained bolus,
refluxed material. Its role is to clear the
esophagus form retained bolus.

33. CONTD…
 Tertiary peristalsis: Tertiary contractions are non-propulsive and
uncoordinated and their non-peristaltic nature means they move
the bolus up as well as down the oesophagus.

35. SEGMENTATION CONTRACTIONS (OR MOVEMENTS)
 It is a type of intestinal motility.
 Unlike peristalsis, which predominates in the esophagus, segmentation
contractions occur in the large intestine and small intestine, while
predominating in the later.

36. CONTD…
 Segmentation contraction occurs 12time/min in duodenum and 8time/min in
the ileum.
 These contraction last for 5-6sec, they occur through out the digestive period.
 Segmentation involves contractions of the circular muscles in the digestive
tract, while peristalsis involves rhythmic contractions of the longitudinal
muscles in the gastrointestinal tract.

37. MOVEMENTS OF SMALL INTESTINE
 Mixing (Segmentation Contractions)
 Peristalsis (Propulsive Movements)
 Movements of Muscularis Mucosa
 Contraction of villi

38. MOVEMENTS OF COLON
 Mixing Movements (Haustrations):
 Same manner that segmentation movements the
circular muscle contracts,

39. CONTD…
 At the same time, the longitudinal muscle of the colon, which is aggregated
into three longitudinal strips called the teniae coli, contracts. move slowly
toward the anus.
 The combination of constricted and relaxed portions of the colon create
haustrations (bag-like pouches). Haustrations mix the chyme or fecal material
and provide slow persistent forward movement.

40. CONTD….
 Propulsive Movements (Mass Movements): Much of the propulsion
in the cecum and ascending colon results from the slow but persistent
haustral contractions From the transverse colon to the sigmoid,

41. CONTD….
 Mass movements one to three times each day, in many people especially for about
15 minutes during the first hour after eating breakfast.
 Occasionally (1-3 times/day), a modified contraction will propel the contents
forward.
 This occurs by a peristaltic contraction pushing the contents through 20 cm or more
of colon in which the haustrations are relaxed.

42. ORGANS

43. 1. MOUTH
 The mouth is the first portion of the alimentary canal
that receives food and produces saliva.

44. CONTD…
 Mouth or oral cavity is bounded by muscles and bones.
 The oral cavity is lined throughout with mucous membrane,
consisting of stratified squamous epithelium containing
small mucus secreting gland.
 The part of mouth between the gums and the cheeks is the
vestibule and the remainder of its interior is the oral cavity

45. CONTD…
 The palate forms the roof of the mouth & is
divided into the anterior hard palate & posterior
soft palate.
 The uvula is a curved fold of muscle covered with
mucous membrane, hanging down from the
middle of the free border of the soft palate.

46. CONTD…
 Relations:
 Anteriorly- by the lips
 Posteriorly- continue with the oropharynx
 Laterally- muscles of cheeks
 Superiorly- bony hard palate
 Inferiorly- muscular tongue & the soft tissues of the floor of the mouth

47. FUNCTION OF MOUTH
 The two main functions of the mouth are eating and speaking.
 The face's trigeminal nerve provides sensation (feeling) and helps us to bite,
chew and swallow.

48. ORAL CAVITY CONSIST OF:
1. Tongue
2. Teeth
3. Salivary glands

49. 1. TONGUE

50. TONGUE
 The tongue is a muscular organ in the mouth and
composed of voluntary muscle. It attached by its base
to the hyoid bone and by fold of its mucous membrane
covering called the frenulum to the floor of the
mouth,
 It is of importance in the digestive system and is the
primary organ of taste in the gustatory system.

51. CONTD…
 Length :3 inches
 Shape: triangular
 The tongue's upper surface (dorsum) is
covered by taste buds housed in numerous
lingual papillae
 The human tongue is divided into two parts, an
oral part at the front and a pharyngeal part at
the back.

52. PAPPILAE
 Papillae (singular papilla) are nodules on the surface of the
tongue that increase the surface area for the taste buds.

53. TYPES OF PAPILAE
1. Vallate/ circumvallate (8-12 in number)
2. Filiform (numerous in numbers)
3. Fungiform( larger than filiform pappilae)
4. Foliate

54. TASTE BUDS
 These are sensory receptor for taste.
 The sensation of taste is called Gustation.
 Taste buds are located on the surface of papilae except filiform
papillae

55. BLOOD SUPPLY TO TONGUE
 The tongue receives its blood
supply primarily from the lingual artery, a
branch of the external carotid artery. The
lingual veins drain into the internal jugular
vein. The floor of the mouth also receives
its blood supply from the lingual artery.

56. FUNCTIONS OF TONGUE
 Mastication (chewing)
 Deglutition (swallowing)
 Taste
 Speech

57. 2. TEETH

58. ERUPTION OF TEETH
 Tooth eruption in humans is a process in
tooth development in which the teeth enter
the mouth and become visible.
 Primary teeth erupt into the mouth from
around six months until two years of age.

59. TEETH
 The teeth are embedded in the alveoli or sockets of the alveolar ridges of the
mandible and the maxilla.
 Babies are born with two sets, or dentitions, the temporary or deciduous teeth
and permanent teeth.
 At birth the teeth of both dentitions are present, in immature form, in the
mandible and maxilla.

60.  There are 20 temporary teeth, 10 in each jaw. They begin to erupt at about 6 months
of age, and should all be present by 24 months.
 The permanent teeth begin to replace the deciduous teeth in the 6th year of age and
this dentition, consisting of 32 teeth, is usually complete by the 21st year.
 The human teeth function to mechanically break down items of food by cutting and
crushing them in preparation for swallowing and digesting.
CONTD…

61. CONTD…
 Humans have four types of teeth: incisors, canines, premolars,
and molars, each with a specific function.

62. PRIMARY TEETH
 Among deciduous (primary) teeth, ten are found in the maxilla (upper jaw) and
ten in the mandible (lower jaw), for a total of 20. The dental formula for
primary teeth is 2.1.0.2/2.1.0.2.
 In the primary set of teeth,
 two types of incisors – centrals and laterals, one canine & two types of
molars – first and second.
 All primary teeth are normally later replaced with their permanent
counterparts.

63. PERMANENT TEETH
 Among permanent teeth, 16 are found in the maxilla and 16 in the mandible,
for a total of 32. The dental formula is 2.1.2.3/2.1.2.3.
 Age 21, all 32 of the permanent teeth have usually erupted.
 The permanent teeth are the:
 Two incisor (for cutting)-central incisor, lateral incisor
 One canine (for tearing)
 Two premolar(for crushing)-first premolar, second premolar,
 Three molar (for grinding)-first molar, second molar, and third molar.

64. STRUCTURE OF TEETH
 ENAMEL
 Enamel is the hardest and most
highly mineralized substance of the
body.
 It is one of the four major tissues
which make up the tooth, along
with dentin, cementum, and dental
pulp.
 96% of enamel consists of mineral,
with water and organic material
comprising the rest.

65. • The normal color of enamel varies from light yellow to grayish white.
 DENTIN
• Dentin is the substance between enamel or cementum and the pulp chamber.
• Dentin is a mineralized connective tissue with an organic matrix of collagenous
proteins.
• The porous, yellow-hued material is made up of 70% inorganic materials, 20%
organic materials, and 10% water by weight
CONTD…

66.  CEMENTUM
 Cementum is a specialized bone like substance covering the root of a
tooth.
 Its coloration is yellowish and it is softer than dentin and enamel.
CONTD…

67.  DENTAL PULP
 The dental pulp is the central part of the tooth filled with soft connective
tissue.
 This tissue contains blood vessels and nerves that enter the tooth from a
hole at the apex of the root.
CONTD…

68. BLOOD SUPPLY OF TEETH
 The blood supply to the upper jaw is provided by the superior alveolar arteries,
which arise from the infraorbital and maxillary arteries.
 Blood to the lower jaw is carried by the inferior alveolar artery, another
branch of the maxillary artery.

69. FUNCTIONS OF TEETH
 Two incisor -for cutting
 One canine -for tearing
 Two premolar-for crushing
 Three molar-for grinding

70. 3. SALIVARY GLANDS
 The salivary glands in are exocrine glands that produce saliva through a system
of ducts into the mouth.
 Humans have 3 paired major salivary glands:
 Parotid
 submandibular and
 Sublingual
 as well hundreds of minor salivary glands.

72. a) PAROTID GLANDS
 The two parotid glands are major salivary glands situated one on each side of
the face just below the external meatus.
 Each gland has a parotid duct opening into the mouth at the level of the second
upper molar tooth.
 The largest of the salivary glands.

73. FUNCTION OF PAROTID GLANDS
 They secrete saliva to facilitate mastication and swallowing, and amylase to
begin the digestion of starches.

74. b) SUBMANDIBULAR GLANDS
 The submandibular glands are a pair of major salivary glands located beneath
the lower jaws.
 The secretion produced is a mixture of both serous fluid and mucus, and enters
the oral cavity via the submandibular duct.
 The submandibular ducts open on to the floor of mouth, one on each side of
the frenulum of the tongue

75. FUNCTIONS OF SUBMANDIBULAR GLANDS
 They also secrete saliva that are essential for digestion and for maintaining
healthy mouth.
 Saliva that contain enzyme that begin to breakdown food before it passes to the
stomach.
 It moistens food so that it slips easily to the esophagus.

76. c) SUBLINGUAL GLANDS
 The sublingual glands are a pair of major salivary glands located inferior to
the tongue, anterior to the submandibular glands.
 Approximately 5% of saliva entering the oral cavity comes from these glands.
 The secretion produced is mainly mucous in nature
 They have numerous small ducts that open into the floor of mouth.

77. FUNCTIONS OF SUBLINGUAL GLANDS
 The main role of sublingual gland is to produce saliva, which has
many functions like food moisturizing, carbohydrate digestion,
protection against bacteria flora etc.

78. d) MINOR SALIVARY GLANDS
 There are 800 to 1,000 minor salivary glands located throughout the oral
cavity within the submucosa of the oral mucosa in the tissue of the buccal, and
lingual mucosa.

79. COMPOSITION OF SALIVA
 About 1.5 litres of saliva is produced daily & it consists of:
 Water
 Mineral salts
 An enzyme
 Mucus
 Lysozyme
 Immunoglobulins

80. FUNCTION OF SALIVA
1. Saliva contributes to the digestion of food and to the maintenance
of oral hygiene.
2. Without normal salivary function the frequency of dental caries,
gum disease and other oral problems increases significantly.

81. LUBRICANT
3. Saliva, coats the oral mucosa, mechanically protecting it from
trauma during eating, swallowing and speaking.
4. In people with little saliva soreness of the mouth is very
common, and the food (especially dry food) sticks to the
inside of the mouth.

82. DIGESTION
5. The digestive functions of saliva include moistening food and
helping to create a food bolus.
6. This lubricative function of saliva allows the food bolus to be
passed easily from the mouth into the esophagus.

83. ROLE IN TASTE
 Saliva is very important in the sense of taste.
 It is the liquid medium in which chemicals are carried to taste receptor cells
(mostly associated with lingual papillae).
 Other Function
 Saliva maintains the pH of the mouth.
 Saliva is supersaturated with various ions.

84. HOW FOOD MOVE
 STEP 1. Mouth: when we eat food mastication &
saliva helps to make the soft bolus of food so the
content travel easily and smoothly through pharynx.
 STEP 2. PHARYNX: The pharynx receives the food
from the mouth. When food reaches the pharynx food
moves towards the esophagus by the involuntary
muscle contractions.

85. CONTD…
 STEP 3. ESOPHAGUS: the bolus move through the esophagus by a movement
called peristalsis ( contraction and relaxation of muscles). That pushes the bolus
towards the stomach.
 STEP 4. STOMACH: the stomach is an organ where food stores and further
broken down by gastric acid and powerful enzymes. From there, food moves
into the small intestine.

86. CONTD…
 STEP 5. SMALL INTESTINE: Most of nutrients are absorbed in the small
intestine, where food is broken down even more by enzymes released from the
pancreas & bile from the liver. Anything left in the small intestines move into
the large intestine by the segmentation contraction.
 STEP 6. LARGE INTESTINE: the colon is a 5-7 foot long muscular tube that
connect the small intestine to the rectum. It is responsible for processing waste.
On average, it takes about 36 hours for waste, or stool, to get through the colon
and exit the rectum through the anus.

88. 2. PHARYNX
 The pharynx is the part of the throat that is behind the mouth and nasal
cavity and above the esophagus and the larynx, or the tubes going down to
the stomach and the lungs.
 The pharynx is the portion of the digestive tract that receives the food from
your mouth.
 Branching off the pharynx is the esophagus, which carries food to the
stomach,

89. CONTD…

90. CONTD…
 The pharynx is devided for descriptives purpose into three parts, the
nasopharynx, oropharynx and laryngopharynx.
 The nasopharynx is important in respiration.
 The oropharynx and laryngopharynx are passages common to both the
respiratory and the digestive system.

91.  Food passes from the oral cavity into the pharynx then to the oesophagus below,
with which it is continuous,
 The walls of the pharynx consist of three layers of tissue.
 The lining membrane (Mucosa) is stratified squamous epithelium, continuous with
the lining of the mouth at one end and the esophagus at the other. Stratified
epithelial tissue provides a lining well suited to the wear and tear of swallowing
ingested food.
CONTD…

92.  The middle layer consists of connective tissue, which become thinner towards
the lower end and contains blood and lymph vessels and nerves.
 The outer layers consists of a number of involuntary muscles that are involved
in swallowing. When food reaches the pharynx, swallowing is no longer under
voluntary control.
CONTD…

93. FUNCTION OF PHARYNX
 For digestive purpose;
1. The muscular walls function in the process of swallowing.
2. It serves as a pathway for the movement of food from the
mouth to the esophagus.

94. 3. OESOPHAGUS

95. ESOPHAGUS
 The esophagus or oesophagus, commonly known as the food pipe or gullet,
The esophagus is a muscular tube connecting the throat (pharynx) with the
stomach.
 The esophagus runs behind the windpipe (trachea) and heart, and in front of
the spine.
 Length :25 cm
 Diameter:2 cm

97.  It passes between muscle fibres of the diaphragm behind the central tendon at the
level of the 10th thoracic vertebra. Immediately the oesophagus has passed through
the diaphragm it curves upward before opening into the stomach. This sharp angle is
believed to be one of the factors that prevents the regurgitation into the oesophagus.
 The upper and lower ends of the oesophagus are closed by sphincters.
CONTD…

98.  The upper cricopharyngeal or upper oesophageal sphincter prevents
air passing into the oesophagus during inspiration and aspiration of
oesphageal contents.
 The cardiac or lower oesophageal sphincter prevents the reflux of acid
gastric contents into the oesophagus.
CONTD…

100. STRUCTURE
 The wall of the esophagus from the lumen outwards consists of mucosa, submucosa
(connective tissue), layers of muscle fibers between layers of fibrous tissue, and an
outer layer of connective tissue.
 The mucosa is a stratified squamous epithelium of around three layers of squamous
cells, which contrasts to the single layer of columnar cells of the stomach.
 Most of the muscle is smooth muscle although striated muscle predominates in its
upper third.

101.  It has two muscular rings or sphincters in its wall, one at the top and one at the
bottom.
 A sphincter is a circular muscle that normally maintains constriction of a natural
body passage or orifice and which relaxes as required by normal physiological
functioning.
 The lower sphincter helps to prevent reflux of acidic stomach content.
CONTD…

102. PARTS OF ESOPHAGUS
 The esophagus is split into the following 3 parts:
 Cervical part (4 cm in length).
 The cervical part extends from the lower border of cricoid
cartilage to the superior border of manubrium sterni.

103. CONTD…
 Thoracic part (20 cm in length).
 The thoracic part extends from superior border of manubrium
sterni to the esophageal opening in the diaphragm.

104. CONTD…
 Abdominal part (1-2 cm in length).
 The abdominal part extends create esophageal opening in the
diaphragm to the cardiac end of the stomach.

105. BLOOD SUPPLY TO OESOPHAGUS
 The inferior thyroid artery supplies the cervical esophagus. Branches of the
bronchial arteries and branches directly off of the aorta supply the proximal and
distal thoracic esophagus, respectively. Finally, branches of the left gastric and
inferior phrenic artery supply the abdominal esophagus.

106. FUNCTIONS OF OESOPHAGUS
1. Formation of a bolus
2. Swallowing
3. Food is ingested through the mouth and when swallowed passes
first into the pharynx and then into the esophagus.
4. Reducing gastric reflux
 Constriction of the upper and lower esophageal sphincters help to prevent
reflux (backflow) of gastric contents and acid into the esophagus, protecting
the esophageal mucosa.

107. 4. STOMACH

108. STOMACH
 The stomach is a J- shaped dilated portion of the alimentary tract situated in
the epigastric, umbilical and left hypochondriac regions of the abdominal
cavity.
 The stomach is a muscular organ. The stomach receives food from the
esophagus.
 As food reaches the end of the esophagus, it enters the stomach through a
muscular valve called the lower esophageal sphincter.

109. RELATIONS
 Anteriorly-left lobe of liver & anterior abdominal wall
 Posteriorly-abdominal aorta,pancreas,spleen,left kidney
 Superiorly-diaphragm,oesophagus & left lobe of liver
 Inferiorly-transverse colon & small intestine
 Left side-diaphragm & spleen
 Right side-liver & duodenum

110. STRUCTURE OF STOMACH
 A pouch-like organ primarily designed for food storage (for 2-4 hours) , some
mechanical and chemical digestion also occur .
 Contains two sphincters at both ends to regulate food movement :
 cardiac sphincter near the esophagus , Which close off the top end of the
stomach
 pyloric sphincter near the small intestine, which close the bottom end of
the stomach.

111.  There are two curvature of stomach
1. Greater curvature – forms the long, convex, lateral
border of the stomach.
2. Lesser curvature – forms the shorter, concave, medial
surface of the stomach. The most inferior part of
the lesser curvature, the angular notch, indicates the
junction of the body and pyloric region.
CONTD…

112.  Divided into 4 regions :
 cardiac stomach (or cardiac), Which surrounds the opening of the
esophagus into the stomach.
 Fundus of stomach (or funded) , which area above the level of the cardial
orifice.
 body of stomach, which is the largest region of the stomach.
CONTD…

113. CONTD…
 pyloric stomach (or Pylorus), which is divided
into the pyloric Antrum and pyloric canal and
is the distal end of the stomach.
 Contain thick folds called rugae at its layer , for
providing larger surface area for expansion ,
secretion , digestion , and some absorption.

114. LAYERS OF STOMACH
The stomach is made of these five layers:
1. MUCOSA: This is the first and innermost layer or lining. It
contains the glands that release digestive juices. These are
called hydrochloric acid and pepsin. This is where most
stomach cancer start.
2. SUBMUCOSA: This second layer supports the mucosa. It is
rich in blood vessels.

115. CONTD…
3. MUSCULRIS: The third layer is made of thick
muscles. They help to mix food with the digestive
juices.
4. SUBSEROSA: This layer contain supporting tissues
for the serosa.
5. SEROSA : this is the last and outermost layer. It’s the
lining that wraps around the stomach to confine it.

116. MOVEMENTS IN STOMACH

117. BLOOD SUPPLY OF STOMACH
 The stomach is supplied by a rich system of arteries derived from the celiac
trunk, the first major visceral branch of the abdominal aorta. The lesser
curvature of the stomach is supplied by the left and right gastric artery, which
are branches of the celiac trunk and the common hepatic artery respectively.

118. FUNCTIONS OF STOMACH
1. Digestion
 The stomach releases proteases (protein-digesting enzymes
such as pepsin) and hydrochloric acid, which kills or inhibits
bacteria and provides the acidic pH of 2 for the proteases to
work.
 Food is churned by the stomach through muscular
contractions of the wall called peristalsis

119. 2. Absorption
 some absorption of certain small molecules nevertheless does
occur in the stomach through its lining
3. Non- specific defense against microbes- provided by
hydrochloric acid in gastric juice. Vomiting may occur in
response to ingestion of gastric irritants, e.g. microbes &
chemicals.
CONTD…

120. GASTRIC JUICE
 Gastric acid, gastric juice or stomach acid, is a digestive fluid
formed in the stomach and is composed of hydrochloric acid
(HCl), potassium chloride (KCl) and sodium chloride (NaCl).
 The acid plays a key role in digestion of proteins, by activating
digestive enzymes, and making ingested proteins unravel so that
digestive enzymes break down the long chains of amino acids.

121. GASTRIC SECRETORY CELLS
1. Chief cells: secrete pepsinogen (an inactive enzyme).

122. CONTD…
2. Parietal cells: secrete hydrochloric and (HCl)
and "intrinsic factor" (which helps absorption
of vitamin B12 in the intestines).
3. Mucous cells: secrete mucus and alkaline
substances to help neutralize HCl in the
gastric juice .

123. CONTD..
4. G cells: secrete a hormone called gastrin , which stimulates the
parietal cells and overall gastric.

124. 5. PANCREAS

125. PANCREAS
 The pancreas is a pale grey gland weighing about 60 grams.
 It is a glandular organ in the digestive system
 It is located in the abdominal cavity behind the stomach.
 Length: 15 cm or 6 inch
 The pancreas is both an exocrine and endocrine gland.

126. CONTD…
Pancreas
Endocrine
gland
Exocrine
gland

127.  Exocrine Pancreas
 This consist large number of lobules made up of small
acini, the walls of which consist of secretory cells.
Each lobule is drained by a tiny duct these unite
eventually to form the pancreatic duct, which extends
along the whole length of the gland and open into the
duodenum
CONTD…

128. FUNCTION OF EXOCRINE PANCREAS
 The function of exocrine pancreas is to produce pancreatic juice
containing enzyme, some in the form of inactive percursors, that
digest carbohydrates, proteins and fats.

129.  Endocrine Pancreas
 The endocrine pancreas disrtibuted
throughout the gland are groups of
specialised cells called the pancreatic islets
( of langerhans). The isleits have no ducts
so the hormones diffuse directly into the
blood.
CONTD…

130. FUNCTION OF ENDOCRINE PANCREAS
1. The endocrine component of the pancreas consists of islet cells (islets of
Langerhans) that create and release important hormones directly into the
bloodstream.
2. Two of the main pancreatic hormones are insulin, which acts to lower blood
sugar, and glucagon, which acts to raise blood sugar

131. STRUCTURE
 Anatomically, the pancreas is
divided into
 the head of pancreas,
 the neck of pancreas,
 the body of pancreas,
 and the tail of pancreas.

132. CONTD…
 The head lies in the curve of duodenum.
 The neck is about 2.5 cm or 1 inch long and lies between the head and the body
 The body is the largest part of the pancreas and lies behind the pylorus (
stomach).
 The tail lies in front of the left kidney and just reaches the spleen.

133. BLOOD SUPPLY OF PANCREAS
 The pancreas is supplied by the pancreatic branches of the splenic artery. The
head is additionally supplied by the superior and inferior pancreaticoduodenal
arteries which are branches of the gastroduodenal (from coeliac trunk) and
superior mesenteric arteries, respectively.

134. FUNCTION
1. The pancreas is involved in blood sugar control and metabolism within the
body.
2. Pancreatic islets are present in the pancreas.
3. Within these islets are four main types of cells which are involved in the
regulation of blood glucose levels.
4. Each type of cell secretes a different type of hormone:
5. α alpha cells secrete glucagon (increase glucose in blood)

135. 6. β beta cells secrete insulin (decrease glucose in blood)
7. δ delta cells secrete somatostatin (regulates/stops α and β cells) and
8. γ (gamma) cells, secrete pancreatic polypeptide.
CONTD….

136. 6. LIVER
 The liver is the largest gland in the body, weighing between 1 and 2.3kg .
 It is situated in the upper part of the abdominal cavity occupying the greater
part of the hypochondriac region, part of the epigastric region and extending
into the left hypochondriac region.
 Its upper and anterior surfaces are smooth and curved to fit the under surface of
the diaphragm, its posterior surface is irregular in outline.

137. RELATION
 Anteriorly- diaphragm & anterior abdominal wall
 Posteriorly- oesophagus, inferior vena cava, aorta, gall bladder, vertebral
column & diaphragm
 Laterally- lower ribs & diaphragm
 Superiorly- diaphragm & anterior abdominal wall
 Inferiorly- stomach, bile ducts, duodenum, hepatic flexure of colon, right
kidney

138. STRUCTURE
 The liver is a reddish-brown wedge-shaped organ with four lobes of unequal
size and shape.
 width -15 cm.
 It is both the heaviest internal organ and the largest gland in the human body
 The lobes of the liver are made up of tiny functional units, called lobules,
which are just visible to naked eye.

139. CONTD…
 Sinusoids containing a mixture of blood from the tiny branches of the portal
vein and hepatic artery.
 This allows the arterial blood and portal venous blood to mix and come into
close contact with liver cells.
 Amongst the cell lining the sinusoids are hepatic macrophages (Kupffer cells)
whose function is to ingest and destroy worn out blood cells and any foreign
particles present in the blood flowing through the liver.

140.  The liver is grossly divided into two parts when viewed from above – a right
and a left lobe.
 The falciform ligament, divides the liver into a left and right lobe.
CONTD…

141. SCHEME OF BLOOD FLOW THROUGH
THE LIVER
Hepatic artery (
Oxygenated blood)
Portal vein ( Deoxygenated
blood rich in nutrients)
Interlobular vein
Sinusoid
Central vein
Hepatic vein
Inferior vena cava
right atrium of the
heart

142. BLOOD SUPPLY TO LIVER
 The liver receives a blood supply from two sources. The first is the hepatic
artery which delivers oxygenated blood from the general circulation. The
second is the hepatic portal vein delivering deoxygenated blood from the small
intestine containing nutrients.

143. FUNCTIONS OF LIVER
1. Synthesis
 Proteins produced and secreted by the liver.
 The liver plays a major role in carbohydrate, protein, amino acid, and lipid
metabolism.
 The liver is responsible for the breakdown of insulin and other hormones.

144. 2. Other
 The liver stores a multitude of substances, including glucose (in the form of
glycogen)
 vitamin A (1–2 years' supply)
 vitamin D (1–4 months' supply)
 vitamin B12 (3–5 years' supply)
 vitamin K, iron, and copper.
CONTD…

145. CONTD….
 The liver produces albumin, the most abundant protein in blood serum.
 Contains phagocytes to destroy damaged erythrocytes and foreign
substances, using phagocytosis

146. 7. GALLBLADDER
 The gallbladder is a small hollow organ
where bile is stored and concentrated
before it is released into the small
intestine.
 In humans, the pear-shaped gallbladder
lies beneath the liver.

147. STRUCTURE
 Sits in a shallow depression below the right lobe of the liver.
 Length-7 to 10 cm or 2.8 to 3.9 inches
 Diameter -4 cm or 1.6 inch
 The gallbladder has a capacity of about 50 millilitres
 It has a fundus or expended end, a body or main part and a neck, which is
continuous with the cystic duct.

148. BLOOD SUPPLY TO GALLBLADDER
 The arterial supply to the gallbladder is via the cystic
artery - a branch of the right hepatic artery (which itself
is derived from the common hepatic artery, one of the
three major branches of the coeliac trunk).

149. FUNCTIONS
1. The main purpose of the gallbladder is to store bile, also called gall, needed
for the digestion of fats in food.
2. Bile flows through small vessels into the larger hepatic ducts and ultimately
through the cystic duct into the gallbladder, where it is stored.

150. 8. SMALL INTESTINE
 The small intestine or small bowel is the part of the gastrointestinal tract
between the stomach and the large intestine, and is where most of the end
absorption of food takes place.
 It lies in the abdominal cavity surrounded by the large intestine. In the small
intestine the chemical digestion of food is completed and absorption of most
nutrients takes place.

152. STRUCTURE
 Length- 3m – 5m
 Diameter- 2.5- 3cm or 1 inch
PARTS
 The small intestine is divided into three
structural parts:
(I)The duodenum
(II)The jejunum
(III)The ileum

153.  The duodenum is a short structure ranging from 20 cm to 25 cm in length, and
shaped like a "C".
 The jejunum is the midsection of the small intestine, connecting the duodenum
to the ileum. It is about 2.5 m long.
 The ileum is the final section of the small intestine.
CONTD…

154. CONTD…
 It is about 3 m long and end at ileocecal valve, which controls the flow of
material from the ileum to the caecum, the first part of the large intestine , &
prevents backflow

155. BLOOD SUPPLY TO SMALL INTESTINE
 The superior mesenteric artery supplies the whole small intestine and extends
branches up to the middle third of the transverse colon. Up to this
point, the innervation is taken over by the vagus nerve (CN X)

156. FUNCTIONS
1. Digestion
 The small intestine is where most chemical digestion takes place.
 Many of the digestive enzymes that act in the small intestine are secreted
by the pancreas and liver and enter the small intestine via the pancreatic
duct.
 Digestion of proteins & carbohydrate

157. 2. Absorption
 Digested food is now able to pass into the blood vessels in the wall of the
intestine through either diffusion or active transport.
 The small intestine is the site where most of the nutrients from ingested
food are absorbed.
CONTD…

158. CONTD..
3. Immunological
 The small intestine supports the body's immune system.
 The presence of gut flora appears to contribute positively to the host's
immune system

159. 9. LARGE INTESTINE
 The large intestine, also known as the
large bowel or colon, is the last part of
the gastrointestinal tract and of the
digestive system.
 Water is absorbed here and the remaining
waste material is stored as feces before
being removed by defecation.

160. STRUCTURE
 The length of male colon is 166 cm .
 female colon 155 cm
 The colon consists of five sections:
1. the cecum
2. ascending colon,
3. the transverse colon,
4. the descending colon,
 the sigmoid colon and the rectum.

161.  Sections of the colon are:
 The ascending colon including the cecum and appendix
 The transverse colon including the colic flexures and transverse
mesocolon
 The descending colon /The sigmoid colon – the s-shaped region of the
large intestine
CONTD…

162.  The average inner diameter of sections of the colon in centimeters
 cecum 8-9cm
 ascending colon 6.6cm
 transverse colon 5.8cm
 descending/sigmoid colon 6.3cm
 and rectum near rectal/sigmoid junction 5.7cm
CONTD…

163. THE CECUM
 The cecum is the first section of the colon and involved in the digestion, while
the appendix is a structure of the colon, not involved in digestion.
 There is no function of the appendix in digestive system. But can cause
significant problems when it becomes inflamed (appendicitis).

164. CONTD…
 The ileocecal valve is a sphincter muscle valve that separates the small intestine
and the large intestine.
 Its critical function is to limit the reflux of colonic contents into the ileum

165. THE ASCENDING COLON
 It is connected to the small intestine by a section of bowel called the cecum.
 The ascending colon runs upwards through the abdominal cavity toward the
transverse colon for approximately eight inches or 20 cm.
 The unwanted waste material is moved upwards toward the transverse colon
by the action of peristalsis.

166. TRANSVERSE COLON
 This part extends across the abdominal cavity in
front of the duodenum and the stomach to the
area of the spleen where it forms the splenic
flexure & curves acutely downwards to become
the descending colon.

167. DESCENDING COLON
 The descending colon is the part of the colon from the splenic
flexure to the beginning of the sigmoid colon, descending colon is
also called the distal gut.
 One function of the descending colon in the digestive system is to
store feces that will be emptied into the rectum.

168. SIGMOID COLON
 The sigmoid colon is the part of the large intestine after the descending colon and
before the rectum.
 The name sigmoid means S-shaped .
 The walls of the sigmoid colon are muscular, and contract to increase the pressure
inside the colon, causing the stool to move into the rectum.

169. APPENDIX
 It is a blind- ended muscular tube attached to the posteromedial wall
of the caecum, about 2cm below ileocaecal junction.

170. CONTD…
 The appendix is 9 cm (7 to 11cm) in length but
can range from 2 to 20 cm. The diameter of the
appendix is 1 to 7 mm.
 It is relatively longer in children and decreases
after 40 years of age.

171. PARTS OF APPENDIX
A) Base
B) Body
C) Tip

172. A) BASE
 It is attached to posteromedial wall of caecum about 2 m below the ileocaecal
junction.
 All taenia of caecum converge to the base and serve as a guide for the
identification of the appendix.

173. B) BODY
 Body is narrow, tubular and contains a
canal which opens into the caecum.
 The caecal opening is guarded by an
incomplete mucous fold called as,”THE
VALVE OF GERLACH”

174. C) TIP
 It is least vascular and is directed in various direction

175. STRUCTURE OF APPENDIX
 The appendix sits at the junction of the small intestine and large intestine. It’s a
thin tube about four inches long. Normally, the appendix sits in the lower right
abdomen.
 The function of the appendix is unknown. One theory is that the appendix acts as a
storehouse for good bacteria, “rebooting” the digestive system after diarrheal
illnesses. Other experts believe the appendix is just a useless remnant from our
evolutionary past. Surgical removal of the appendix causes no observable health
problems.

176. 10. RECTUM
 The rectum is the last section of the large intestine. It holds the formed feces
awaiting elimination via defecation. It leads from the sigmoid colon & terminate
in the anal canal.

177. 11. ANUS
 The anus is the external opening of the rectum.
 This is short passage about 3.8 cm long in the adult.
 Its function is to control the expulsion of feces.
 Two sphincters control the exit of feces from the body during an act of
defecation.

178. CONTD…
 These are the internal anal sphincter and the external anal sphincter, which are
circular muscles that normally maintain constriction of the orifice and which
relaxes as required by normal physiological functioning.

179. BLOOD SUPPLY TO LARGE INTESTINE
 The large intestine is supplied by the branches of the inferior mesenteric artery
(IMA)

180. FUNCTIONS
1. The large intestine absorbs water and any remaining absorbable nutrients
from the food before sending the indigestible matter to the rectum.
2. The large intestine is heavily colonised by certain types of bacteria, which
synthesize vitamin K and folic acid.

181. CONTD….
3. They include Escherichia coli, enterobacter aerogens, streptococcus fascalis
and clostridium perfringens. These microbes are commensals i.e normally
harmless in humans. However they become pathogenic if transferred to
another part of the body, e.g. E. coli may cause cystitis if it gains access to the
urinary bladder.

182. GUT FLORA
 The large intestine houses over 700 species of bacteria that perform a variety of
functions.
 The large intestine absorbs some of the products formed by the bacteria
inhabiting this region.
 Undigested polysaccharides (fiber) are metabolized to short-chain fatty acids
by bacteria in the large intestine.

184. PHYSIOLOGY OF DIGESTION
The mouth is the beginning of the digestive tract.
Chewing breaks the food into pieces that are more easily
digested,
while saliva mixes with food to begin the process of
breaking it down into a form your body can absorb and
use.
From pharynx food travels to the esophagus or swallowing
tube

185. CONTD…
Due to series of contractions, called peristalsis, the
esophagus delivers food to the stomach.
The lower esophageal sphincter prevents food from
passing backwards into the esophagus
The stomach secretes acid and powerful enzymes that
continue the process of breaking down the food.
When it leaves the stomach, food is the consistency of a
liquid or paste. From there the food moves to the small
intestine.

186. CONTD…
The small intestine continues the process of breaking
down food by using enzymes released by the pancreas
and bile from the liver.
Bile is a compound that aids in the digestion of fat and
eliminates waste products from the blood.
Peristalsis is also at work in this organ, moving food
through and mixing it up with digestive secretions
The duodenum is largely responsible for continuing the
process of breaking down food, with the jejunum and
ileum being mainly responsible for the absorption of
nutrients into the bloodstream.

187. CONTD…
pancreas secretes enzymes into the small intestine.
These enzymes break down protein, fat, and carbohydrates
from the food we eat.
Stool, or waste left over from the digestive process, is
passed through the colon by means of peristalsis, first in a
liquid state and ultimately in solid form as the water is
removed from the stool.
A stool is stored in the sigmoid colon until a "mass
movement" empties it into the rectum once or twice a day.

188. FUNCTIONS OF GI TRACT
1. Ingestion: taking of food into the alimentary tract. i.e. eating & drinking.
2. Propulsion: mixes & moves the contents along the alimentary tract.
3. Digestion: consist of:
 Mechanical breakdown of food e.g. mastication (chewing)
 Chemical digestion of food into small molecules by enzymes

189. CONTD….
4. Absorption: this is the process by which digested food
substances pass through the walls of some organs of the
alimentary canal into the blood for circulation.
5. Elimination: food substances that have been eaten but
cannot be digested & absorbed are excreted from the
alimentary canal as faeces by the process of defaecation

190. CONCLUSION
 The digestive system helps the human body absorb nutrients, and rid the body
of waste.
 With the use of the digestive system, our food we ingest can be use to help
growth development, healthy eyesight and skin complexion.

193. RECAPITALIZATION
 Parts of large intestines.
 Parts of Appendix.
 Diameter of cecum

194. ASSIGNMENT
 Draw a well labeled diagram of large intestine.

195. REFERENCES
 Wilson and Ross. A textbook of Anatomy & Physiology
in health & illness: Elsevier publisher; 12th edition. Page
no. 299- 325.
 www.slideshare.com. Viewed on 26/05/2020.