Anatomy and physiology of the digestive system for nursing students

1. Digestive system
Unit – Iv system responsible for maintaining
metabolism in the body

2. General objective
• At the end of this teaching session student
should be able to describe the about
digestive system

3. Specific objectives
1. Introduction of the digestive system
2. List out the GI system
3. Describe the structure of GI tract
4. Explain the structure and function of
accessory organs

4. introduction
 performs the mechanical & chemical
processes of digestion, absorption of
nutrients, & elimination of wastes
 consists of the mouth, pharynx, esophagus,
stomach, intestine, & accessory organs

5. Functions of the digestive system
are:
1. Ingestion.
Food into the mouth, active, voluntary
process .
1. Propulsion.
swallowing of food -propulsive process
called peristalsis (involuntary

6. 3 Digestion
 Mechanical Digestion
- physical preparation of food for digestion.
- Segmentation – mixing of food in the
intestines with digestive juices.
 Chemical Digestion
- Carbohydrates, Fat, and Proteins are
broken down by enzymes

7. 5.Absorption.- At the lumen of GI tract
digested portion absorption to
the blood or lymph
6. Defecation
- removal/elimination of the waste
products from the body.

9. Digestive System Consists of
the Two main groups
1. Alimentary Canal
(gastrointestinal tract (GI tract)
2. Accessory Digestive Organs

10. 1 Alimentary Canal (muscular digestive
tract
1. Oral cavity
2. Pharynx
3. Esophagus
4. Stomach
5. Small intestine
6. Large intestine
7. Rectum
8. Anus
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

12. 2. Accessory Digestive Organs
a. Teeth
b. Tongue
c. Salivary glands
d. Gall bladder
e. Liver
f. pancreas

13. Mouth and Associated Organs
1 Mouth
• Food enters the GI tract by ingestion .
• Food is broken down by mechanical
digestion , using mastication .
• One chemical digestive process occur
where amylase
• enzyme in saliva breaks down
polysaccharide into disaccharides

14. Structures associated with mouth
• Anteriorly —by the lips
• Posteriorly — oropharynx
• Laterally —by the muscles of the cheeks
• Superiorly — hard palate and soft palate
• Inferiorly —by the muscular tongue and
the soft tissues of the floor of the
mouth.

15. cont
• lining- mucous stratified squamous
epithelium- mucus-secreting .
• uvula curved fold of muscle covered with
mucous membrane,

17. • Chemical digesting

18. Tongue (accessory)
• Voluntary muscular structure and live in the floor
of mouth.
• Attached - base hyoid bone
• By a fold of its mucous membrane covering, called
the frenulum,
• Superior surface - stratified squamous epithelium,
• With papillae - nerve endings of taste,

20. Blood supply
• lingual branch of the external carotid artery.
• lingual vein, which joins the internal jugular vein
• Nerve supply
• Hypoglossal nerves (12th cranial nerves) which
supply the voluntary muscle tissue
• Facial and glossophanryngeal nerves which
special sensation of taste

21. Functions of the tongue
• mastication (chewing)
• deglutition (swallowing)
• speech
• Taste
• Non verbal movement

22. Teeth (accessory)
• Embedded in alveoli or sockets of the alveolar
ridges in maxillary and mandibular bones
axillary and mandibular bones
• Two sets, temporary and permanent teeth
• 20 temporary teeth, about 6- 24 months
• A tooth is tight in its socket by periodontal
ligament

23. • permanent teeth begin 6th year - 24th year
32 teeth
• types: incisors (for cutting), Canines (for
tearing) ,Premolars (for crushing),and Molars
(for grinding).
• dental formula of 2 -1-2-3.
Central incisor
(erupts at 6–8 months;
lost at 5–7 years)
Lateral incisor
(erupts at 8–11 months;
lost at 6–8 years)
Canine
(erupts at 16–20 months;
lost at 8–11 years)
First molar
(erupts at 10–16 months;
lost at 9–11 years)
Second molar
(erupts at 20–24 months;
lost at 9–11 years

26. Structure of a tooth
• Shapes of different, structure is same
• the crown — juts from the gum
• The root — embedded in bone
• The neck — crown merges with root.
• In centre - pulp cavity containing blood
vessels, lymph vessels and nerves,
• Surrounding this pulp cavity hard ivory
dentine.
• Outside the dentine enamel..

28. Blood supply
• Most of the arterial blood supply to the teeth is
by branches of the maxillary arteries.
• The venous drainage is by a number of veins
which empty into the internal jugular veins
Nerve supply
• upper teeth is by branches of the maxillary
nerves
• lower teeth by branches of mandibular nerves.
• These are both branches of the trigeminal
nerves (5th cranial nerves)

29. Function of teeth
• Increase surface area for digestion
• Maintain normal facial appearance
• Formula for clear speech
• Avoided of infection

30. Salivary gland (accerssory)
• 3 pairs of salivary glands
 parotid ,
 submandibular ,
 sublingual
secrete most saliva in oral cavity , using
salivary ducts

32. Submandibular glands
• Lie one on each side of face under the angle
of the jaw.
• Two submandibular ducts open floor of
mouth, each side of frenulum of tongue

33. Sublingual glands
• Lie under the mucous membrane of floor of
mouth front of the submandibular glands.
• They have numerous small ducts that open into
the floor of mouth.
Parotid glands
• Situated one on just below external acoustic
meatus each
• Parotid duct opening to mouth at the level of
the second upper molar tooth

34. Structure of the salivary glands
• The glands are all surrounded by a
fibrous capsule.
• They consist of a number of lobules
made up of small acini
• lined with secretory cells

35. Nerve supply
• By parasympathetic (facial nerve)- stimulation
increases(smell of food-produce saliva)
• Sympathetic stimulation decreases it .
(postganglionic nerve)
Blood supply
• By various branches external carotid arteries
• Drainage by external jugular veins.

36. Composition of saliva
• About 1.5 litres of saliva is produced daily and
it consists of:
• water
• mineral salts
• enzyme: salivary amylase
• mucus
• lysozyme
• immunoglobulins
• blood-clotting factors

37. Functions of saliva
• Chemical digestion of polysaccharides.
• Lubrication of food.
• Cleansing and lubricating.
• Non-specific defence.
• Taste.

38. 2 Pharynx

39. Basic structure of GI tract
Serosa/adventitia
• composed of areolar connective tissue &
simple squamous epithelium
• esophagus lacks a serosa; as a replacement
for only a single layer of areolar connective
tissue called the adventitia forms the
superficial layer of this organ

40. Musculer leyer
• –mouth, to middle parts of esophagus contains
skeletal muscle that produces voluntary
swallowing
• external anal sphincter also which permits
voluntary control of defecation
• smooth muscle that is generally found in two
sheets: an inner sheet of circular fibers & an
outer sheet of longitudinal fibers
• –between the layers of the muscularisis a
second plexus of neurons

43. Submucosa
• consists of areolar connective tissue that
binds the mucosa to the muscularis
• contains many blood & lymphatic vessels
that obtain absorbed food molecules
• located in the submucosa is an wide network
of neurons known as the submucosalplexus
• also contain glands & lymphatic tissue

44. • Mucosa
This consists of three layers of tissue:
• mucous membrane
• In mouth, pharynx, esophagus, & anal canal is
mainly non keratinized stratified squamous
epithelium
• In stomach & intestine is simple columnar
epithelium
• Several types of endocrine cells (entero
endocrine cells) secrete hormones

45. 2 lamina propria
• is areolar connective tissue containing many
blood & lymphatic vessels
• contains mucosa associated lymphatic tissue
(MALT)
3 muscularis mucosae
• throws the mucous membrane of the stomach
& small intestine into many small folds, which
increase the surface area for digestion &
absorption

47. Blood supply
 Superior and inferior Mesenteric aterr/ veins
 Celiac artery
 Hepatic Portal System- major blood vessel that
takes blood from intestine to capillary bed in
liver

48. Regulation of gi tract activity
autonomic nervous system
 Parasympathetic-stimulate activities .
 sympathetic - inhibit activities .
Hormonal control
 Hormones from endocrine gland and from
GI tract itself help regulate GI tract
activities .
Reflex mechanism
 Stimulate or inhibit one another .

49. 3 Oesophagus
• Muscular tube about 25 cm long & 2cm wide
• It extends pharynx to stomach curved end for
prevent aspirate
• Upper end lower end ring of muscle – called a
sphincter – which keeps the esophagus
closed. (u- cricophalanjia ,cardiac )

50. Cont…..
• When food has been chewed, it is pushed into
the pharynx. The sphincter relaxes, opening the
esophagus,
• food is pushed down by muscular contractions.
• In 5 to 10 seconds the food comes to the end of
the tube.

51. Structure
• There are four layers of tissue
• outer covering, the adventitia, consists of
elastic fibrous tissue.
• Proximal third is lined by stratified squamous
Epithelium and distal third by columnar
epithelium.
• Middle third is lined by a mixture

52. Blood supply
• Arterial.- Thorasic - oesophageal arteries,
branches from the aorta.
 Abdominal region - by branches of inferior
phrenic arteries
• Venous drainage. Thoracic- azygos and hemi
azygos veins.
 Abdominal - left gastric vein.
Nerve supply
• Sympathetic and parasympathetic nerves

54. Function of esophagus
• Receivesabolusfromthepharynx
• Foodsbolustransportbyrhythmicwaveperistalsis
• Movesitintothestomach;thisneedsrelaxationof
theupperesophagealsphincter
• secretionofmucus.

55. 4 stomach
• J-shaped dilated portion of alimentary
tract
• situated in epigastric, umbilical and left
hypochondriac regions of abdominal cavity

56. • Organs associated with the stomach
• Anteriorly —left lobe of liver and anterior
abdominal wall
• Posteriorly —abdominal aorta, pancreas,
spleen, left kidney and adrenal gland
• Superiorly — diaphragm, oesophagus and left
lobe of liver
• Inferiorly — transverse colon and small intestine
• To the left — diaphragm and spleen
• To the right—liver and duodenum

57. Structure of the stomach

60. Walls of the stomach
four layers but with some modifications
. Muscle layer consists of three layers smooth
muscle fibres:
• outer layer of longitudinal fibres
• middle layer of circular fibres
• inner layer of oblique fibres
Mucosa.
• They consist of specialised cells that secrete
gastric juice into the stomach

61. Gastric secretory cells
• Chief cells: secrete pepsinogen ( inactive
enzyme).need to Hcl for active
• Parietal cells: secrete hydrochloric (HCL)
and intrinsic factor" (which helps absorption of
vitamin B12 in the intestines).
• Mucous cells: secrete mucus and alkaline
substances to help neutralize HCl in the gastric
juice .
• G cells: secrete gastrin , which stimulates the
Hcl cecretion cell and overall gastric secretion.
• gastric glands -Water, mineral salts

62. Blood supply
Arterial - by branches of coeliac artery
venous - into the portal vein.
Nerve supply
The sympathetic supply - coeliac plexus (pain
sensation)
parasympathetic supply from vagus nerves.

63. Functions of gastric juice
• Water --liquefies the food
• HCL --acidifies food and stops action of
salivary amylase
 Kills ingested microbes
• Intrinsic factor (a protein) - B12 from the ileum
.

64. • Pepsinogens + HCL pepsins
• Protein pepsins peptides (2
(pH 1.5 to 3.5)
• Mucus -- mechanical injuryof stomach wall by
lubricating the contents.
• Lipid gastric lipases fatty acids----(3 .

65. Moment of stomach

66. (1)
• Mixing waves initiated
in the body of the
stomach
• toward the pyloric
region (pink arrows
directed inward).

67. (2)
• The more fluid part of the
chyme is pushed toward the
pyloric region (blue arrows)
• , whereas the more solid
center of the chyme
• squeezes past the peristaltic
constriction back toward the
body of the stomach (orange
arrow).

68. ( 3)
• Additional mixing waves
(purple arrows) Move in
the same direction and in
the same way as The
earlier waves (1) that
reach the pyloric region.

69. (4)
• Again, the more fluid part of
the chyme is pushed toward
the pyloric region (blue
arrows),
• Whereas the more solid
center of the chyme
Squeezes past the peristaltic
constriction back Toward
the body of the stomach
(orange arrow).

70. (5)
• Some of the most fluid chyme is
squeezed through the pyloric
opening into the duodenum
(small blue arrows),
• Whereas most of the chyme is
forced back Toward the body of
the stomach For further mixing
(orange arrows).

71. Regulation of Gastric Secretion
• Regulation by both nervous and hormonal
mechanisms
• food moving along oral cavity and esophagus
stimulates parasympathetic nerves
• To activate secretion in gastric glands
• gastric hormone from G cells in turn
stimulates the gastric glands for more
activities ("positive feedback").

72. when food is emptying stomach ,
• sympathetic nerves inhibit the gastric glands
• inhibits other gastric activities.
• Stimulate small intestine
• The above regulations occur in 3 overlapping
phases:
• Cephalic Phase,
• Gastric Phase,
• Intestinal Phase

73. Cephalic phase:
1. This flow of juice occurs before food reaches
the stomach and is due to reflex stimulation
of the vagus (parasympathetic) nerves
initiated by the sight,smell or taste of food
2. Vagus stimulates acid secretion.
a. Direct stimulation of parietal cells (major
effect).
b. Stimulation of Gastrin secretion (lesser
effect).

74. Gastric phase.
When stimulated by the presence of
• food the enteroendocrine cells in the pylorus and
duodenum secrete the hormone gastrin, into
blood.
• Gastrin, stimulates gastric glands to produce
more gastric juice.
• In this way secretion of digestive juice is
continued after end of a meal and the end of the
cephalic phase.
• Gastrin secretion is suppressed when the pH in
the pylorus falls to about 1.5.

75. Intestinal phase.
• When digested contents of the stomach
reach the small intestine, secretin and
cholecystokinin, are produced by endocrine
cells in intestinal mucosa.
• They slow down secretion of gastric juice and
reduce gastric motility.
• In the duodenum becomes more thoroughly
mixed with bile and pancreatic juice.
• The rate at which the stomach empties
depends basically on the type of food eaten

77. Functions of the stomach
• Temporary storage digestive enzymes, pepsins,
to act Chemical digestion — pepsins convert
proteins to polypeptides
• Mechanical breakdown — the three smooth
muscle Layers enable the stomach to act as a
mix gastric Juice to chyme

78. • Limited absorption of water, alcohol and some
lipid soluble drugs
• Preparation of iron for absorption further
along the tract — the acid environment of the
stomach
• Production of intrinsic factor needed for
absorption of vitamin B12 in the terminal ileum
• Regulation of the passage of gastric contents
into the duodenum.

79. 5 The small intestine
• Continuous with pyloric sphincter and leads at
ileocaecal valve.
• Length is 5.9m in women and 6.4m in men.
• It is approximately 2.5–3 cm in diameter
• mucosa averages 30 square meter
• Three sections – duodenum, jejunum, ileum
• It receives bile juice and pancreatic juice through
pancreatic duct, controlled by the sphincter of Oddi

83. Duodenum
• Duodenum about 20–25 cm
• Continuous with stomach shaped like "C".
• It lies above the level of the umbilicus, 1st, 2nd
and 3rd lumbar vertebrae.
• It surrounds the head of the pancreas
• Pancreatic juice enters trough hepatopancreatic
ampulla

84. jejunum
• Midsection of the small intestine,
• Connecting the duodenum to the ileum.
• About 2.5 m long, contains plicae , and villi
• Digestion are absorbed into the bloodstream
here.

85. The ileum
• The final section of the small intestine.
• About 3 m long, contains villi similar to jejunum.
• Absorbs mainly vitamin B12 and bile acids,
remaining nutrients.
• Ileum joins to the cecum of the large intestine at
ileocecal junction.

86. Structure of the small intestine
• Composed of four layers of tissue some
modifications of peritoneum and mucosa .
Peritoneum.
• A double layer of peritoneum called mesentery
attaches the jejunum and ileum to posterior
abdominal wall
• The large blood vessels and nerves lie on posterior
abdominal wall and branches to small intestine pass
between the two layers of mesentery

87. Mucosa.
• The surface area of increased by circular folds,
villi and microvilli.
• The permanent circular folds, unlike the rugae of
the stomach, are not smoothed out when the
small intestine is enlarged .
• They promote mixing of chyme as it passes
along.
• Their covering consists of columnar epithelial
cells, or enterocytes, with tiny microvilli on their
free border

88. • Goblet cells that secrete mucus are spread
between the enterocytes.
• epithelial cells of glands migrate upwards to form
walls of villi switching those at the tips as they are
rubbed off by the passage of intestinal contents
• These epithelial cells enclose a network of blood
capilliaries and a central lymph capillary.
• Lymph capillaries are called lacteals because
absorbed fat gives

90. • Absorption of nutrients take place in the
enterocytes before entering the blood and lymph
capillaries
• Many lymph nodes are found in the mucosa (
solitary lymphatic follicles, combined lymphatic
follicles/ payers patchers)
• These lymphatic tissues, neutralise ingested
antigens

91. Blood supply
 Artery supplies by
• The superior mesenteric artery ,
 venous drainage by
• superior mesenteric vein
Nerve supply
• Sympathetic (T6-T9)
• Parasympathetic(vegus)

93. plica
densi10
to 40 per
sq. about
1 to 2
mm
long.

94. Chemical digestion in small intestine
• acid chyme in the small intestine it is mixed
with pancreatic juice, bile and intestinal juice,
• Alkaline intestinal juice (pH 7.8–8.0) assists in
raising pH of the intestinal contents to
between 6.5 and 7.5. and is in contact with
the enterocytes of the villi. The digestion of all
nutrients is completed:

95. Cont..
Digestion of proteins.
• Peptidases (Trypsinogen and chymotrypsinogen )
are inactive enzyme which converts them into the
active proteolytic enzymes trypsin and
chymotrypsin by enterokinase,
• These enzymes convert polypeptides to
tripeptides,dipeptides and amino acids.
Digestion of fats.
• Lipase converts fats to fatty acids and glycerol.
• To aid the action of lipase, bile salts emulsify fats,
(increasing theirsurface area.)

96. proteins are broken down to amino acids
Gastric
juice
pancreas
intestinal
Schy
motrip
cin(
brek
carbo
xil link

98. Cont,…
• Pancreatic amylase converts all digestible
polysaccharides (starches) not acted upon by
salivary amylase to disaccharides
• Intestinal Sucrase, maltase and lactase
complete the digestion of carbohydrates by
converting disaccharides such as sucrose,
maltose and lactose to monosaccharides at
the surface of the enterocytes

99. Chemical digestion in small intestine

101. Absorption of nutrients
Diffusion.
• Monosaccharides, amino acids, fatty acids and
glycerol diffuse gradually their concentration rises
into the enterocytes from the intestinal lumen.
Active transport.
• Monosaccharides, amino acids, fatty acids and
glycerol fat soluble vit,Na Ca,Mg may be actively
transported into villi; this is faster than diffusion.
• Pasive-Cl,K (no need enargy)

102. • Fatty acids , glycerol ,Fat-soluble vitamins into
the lacteals
• Some proteins are absorbed unchanged, e.G.
(Milk and oral vaccines),
• Absorption greatly increased by the circular
folds (plica).
• Fluid absorption is more by the small intestine

105. Control of secretion
• The secretion of pancreatic juice is stimulated
by secretin and CCK, produced by endocrine
cells in the walls of the duodenum.
• The presence in the duodenum of acid chyme
from the stomach stimulates the production of
these hormones (stimulator of CCK release is
the presence of fatty acids and/or certain
amino acids in the chyme entering the
duodenum)

106. Cont..
Release from the gall bladder
• After a meal, the duodenum secretes secretin and
CCK during the intestinal phase
• They stimulate contraction of the gall bladder and
relaxation of the hepatopancreatic sphincter, expelling
both bile and pancreatic juice
• Secretion is markedly increased when chyme entering
the duodenum contains a high proportion of fat.
• Secretin release is inhibited by H2 antagonists, which
reduce gastric acid secretion. As a result, if the pH in
the duodenum increases above 4.5, secretin cannot be
released

107. Movement of small intestine
1 Segmentation(Mixing movements )
-Rhythmical alternating contraction and
relaxation
2 Peristalsis (propulsive contractions)
food act as stretch stimulus –detect by nerve
–containing polypeptide
 Both perform similar functions. mainly churns
food but also propels it.

108. Function of small intestine
• Onward movement
• Secretion of the intestinal juice About 1500
mL of intestinal juice are secreted daily by
the glands It is slightly basic (alkaline) and
consists of water, mucus and mineral salts

109. • Conclusion of chemical digestion
–carbohydrates are broken down to
monosaccharides
–proteins are broken down to amino acids
–fats are broken down to fatty acids and
glycerol
• self protects intestinal wall by mucus
(Hcl,bacterial action and acid produced in the
feces )

110. LARGE INTE
Large intestine (colon) STINE
(COLON)
• This is about 1.5 metres long, diameter 6 cm
• Extending from the ileocecal valve(RIF) to the
anus deep in the pelvis.
• It forms an arch round the coiled-up small
intestine

111. Divided into
• Cecum
• Ascending colon
• Transverse colon
• Descending colon
• Sigmoid colon
• Rectum
• Anal canal
• Anus

113. The caecum.
• This is the first part of the colon.
• It is a dilated region and blind end inferiorly
• Continuous with the ascending colon superiorly.
• Ileocaecal valve opens from the ileum.
• Vermiform appendix is a fine tube, leads from
the caecum
• To remove water and other key nutrients from
waste material and recycle it back into body

115. The ascending colon.
• This passes upwards to the level of the liver
• Where it curves very to the left at the hepatic
flexure to become the transverse colon
• The ascending colon carries feces from the
cecum
• Bacteria digest the transitory fecal matter in
order to release vitamins.
• Absorbs water, nutrients, and vitamins

116. The transverse colon.
• Extends across the abdominal cavity in front of
the duodenum
• Stomach to the area of the spleen forms the
splenic flexure and curves downwards to
become the descending colon

118. Cont..
• Feces are mixed, bacteria ferment the waste
material to release vitamins and a few trace
nutrients
• Water, nutrients, and vitamins are absorbed
• Slow longitudinal waves of muscle contraction
known as peristalsis to push the feces along its
length

119. The descending colon
• Extends from the left colic flexure to the
pelvic.
• Store feces that will be emptied into the
rectum.
• Absorption of water and other substances
• Main function of store waste until it can be
removed till form solid

120. Sigmoid colon.(pelvic colon)
• like a Greek letter sigma (ς) or Latin letter S
• Closest to rectum and anus
• About 35–40 cm in length.
• Secretes mucus and enzymes
• Help move waste material
• Fecal material can be stored in for seven hours or
more

121. The rectum.
• This is a slightly dilated section
• About 13 cm long. It leads from the sigmoid
colon and terminates in the anal canal
• Its quality is similar to that of the sigmoid colon
• The word rectum comes from the Latin,

123. The anal canal.
• This is a short passage about 3.8 cm long
• leads from the rectum to the anus
• Below the level of the pelvic diaphragm.
• It lies in the anal triangle of perineum in
between the right and left ischioanal fossa.
• divided into three part(proximal,middl ,distol )

127. Anus
• Meaning "ring", "circle
• It is a 2-inch long
• External opening of the rectum
• There is internal and external anal sphincter ,
main function is control it
• Located behind the vagina in females and behind
the scrotum in males

128. Structure of the colon

129. Structure of the colon cont..

130. • three bands, called taeniae coli, situated at
regular intervals round the colon

131. • Submucosal layer there is more lymphoid tissue
• Rectum between anus mucosa goblet cells
forming simple tubular glands,
• Mucous membrane lining of the rectum above
and which merges with the skin
• Mucous membrane is arranged in 6 to 10 vertical
folds, the anal columns

133. Blood supply
Arterial supply - mainly by the superior(C,A,T) and
inferior mesenteric arteries( rec)
• iliac arteries distal section of rectum and anus
Venous drainage - Venous drainage is mainly by the
superior and inferior mesenteric veins which drain
blood from the parts supplied by arteries of the
same names.

134. Cont..
• These veins join the splenic and gastric veins
to form the portal vein
• Veins draining the distal part of the rectum
and the anus join the internal iliac veins,
meaning that blood from this region returns
directly to the inferior cava, bypassing the
portal circulation.

135. Functions of the large intestine
Absorption - water, by osmosis, Mineral salts,
vitamins and some drugs
Microbial activity (Escherichia coli, Enterobacter
aerogenes, Streptococcus faecali) which
synthesise vitamin K and folic acid.
–Hydrogen, carbon dioxide and methane are
produced by
–bacterial fermentation of unabsorbed
nutrients, especially carbohydrate. Gases pass
out of the bowel as flatus (wind)

136. Cont…
Mass mMass movement
• large intestine does not exhibit peristaltic
movement as in other parts of the digestive
tract.
• Only at equally long intervals (2 hour) does a
wave of strong peristalsis sweep along the
transverse colon forcing its contents into the
descending and sigmoid colons.
• This is known as mass movement and it is often
precipitated by the entry of food into the
stomach.
• This combination of stimulus and response is
called the gastrocolic reflexovement

137. Defaecation
• Usually the rectum is empty, but when a mass
movement forces the contents of the sigmoid
colon into the rectum the nerve endings in its walls
are stimulated by stretch.
• In infants, defaecation occurs by reflex
(involuntary) action.
• However, during second or third year of life
children develop voluntary control of bowel
function.

138. Cont..
• In practical terms this acquired voluntary control-
brain can inhibit the reflex until it is suitable to
defaecate.
• external anal sphincter is under conscious control
through pudendal nerve
• When need to pass faeces is voluntarily
postponed, it tends to fail until next mass
movement occurs and the reflex is initiated again.
• Repeated suppression of the reflex may lead to
constipation as more water is absorbed.

140. Constituents of faeces
• ¾ Water, ¼ Solid
• Undigested and Unabsorbed food
• Intestinal secretions, Mucous
• Bile pigments and Salts
• Bacteria and Inorganic material
• Epithelial cells, Leukocytes

142. Appendix
• Narrow, vermin tube, arises from the
posteriomedial caecal wall.
• Length can vary from 2 to 20 cm in length,
• Longer in children and may atrophy and
shorten after mid-adult life
• Blood - Appendicular artery and vein
• Nerves- sympathetic,parasympathetic

143. Function
• No reports of impaired immune or
gastrointestinal function in people without an
appendix”
• It secretes IgA rich mucus, which
• works as anti-harmful bacterial agent.
• Housekeeper of the good bacteria.

144. Pancreas (accessory)
• glandular organ in digestive and endocrine
system .
• lies in the upper left part of the abdomen. It
is found behind the stomach.
• about 15 cm (6 in) long and 60 grams
• divided - head , neck , body , and tail

146. Blood supply
• Branches of both coeliac artery and superior
mesenteric artery.
• Body and neck - drain into the splenic vein;
head drains - superior mesenteric and portal
veins.

148. Structure of pancreas

151. exocrine consists of
• Water
• Mineral salts
• Enzymes:- amylase , lipase
• Inactive enzyme originators:
— trypsinogen
— chymotrypsinogen
— procarboxypeptidase.

152. The islets are composed of:
• A or α cells (~20%), - glucagon
• B or β cells (~75%), - insulin
• D or δ cells (~5%),-somatostatin, (inhibitor of
both insulin and glucagon Secretion)
• F cells (<2%) -pancreatic polypeptide (self re
of pancreas)

154. inactive
enterokinas
e

155. Liver
• Largest gland in the body, weighing
• Situated in the upper part of abdominal
cavity occupying the greater part of
• Extend from RIF to LIF.
• Liver has four lobes.
• Right lobe, left lobe.,Caudate and
quadrate lobes,
• The portal fissure- posterior surface- various
structures enter and leave the gland.

157. Organs associated with the liver
• Superiorly— diaphragm
• Anteriorly- anterior abdominal wall
• Inferiorly —stomach, bile ducts, duodenum,
kidney and adrenal gland
• Posteriorly —oesophagus, inferior vena cava,
aorta, gall bladder, vertebral column and
diaphragm
• Laterally — lower ribs and diaphragm

158. Structure
Liver are made tiny hexagonal lobules
Formed by cubical-shaped hepatocytes,
Arranged in pairs of columns
Between columns call sinusoids and
caneliculs
A mixture of blood -portal vein and hepatic
artery
,

159. • Allows close contact with liver cells.
• Hepatic macrophages( kupffer cells) ingest and
destroy any foreign particles
• Sinusoids bloobinto central veins.
• These veins joind other veins,
• eventually they become the hepatic veins
• Hepatic vain empty into ivc

160. Structure of liver

161. • Liver is to secrete bile.
• canaliculi run between the columns of liver cells.
• Drain bile from other side of hepatocyte to the
canaliculi
• Eventually they form the right and left hepatic
ducts
• Lymph tissue and lymph vessels has each lobule.

162. Bile fome
• Hepatocyte- bile acid –(covert)-glychochoric
acid +Na or K = bile salt
• Heam(onvert) – bile pigments+glucuronic acid=
bile
• 95% reabsorb bile salt
• Bile pigment release with faces and urine

167. Functions of liver
• Carbohydrate metabolism
• Desaturation of fat,
• Protein metabolism.
 Deamination of amino acids
 Transamination —
 Synthesis of plasma proteins
 blood clotting factors

168. • Breakdown of erythrocytes and defence
against
• Metabolism of ethanol.
• Inactivation of hormones.
• Synthesis of vitamin A from carotene.
• Production of heat.
• Secretion of bile.
• Storage.

169. Composition of bile
About 500 ml of bile are secreted daily.
• Water
• Mineral salts
• Mucus
• Bile pigments, mainly bilirubin
• Bile salts,
• Cholesterol

171. • Gall bladder
• pear-shaped sac
• attached to posterior surface of liver
• ocated under the liver and on the right side of
the abdomen.
• is part of the biliary tract
• It has a fundus , body or main part and a neck
• continuous with the cystic duct

172. Structure
• same layers of tissue as alimentary canal,
• some modifications.
• Peritoneum covers only the inferior surface.
• becouse contact by posterior surface to liver
• Muscle layer.- additional layer of oblique muscle
fibres.
• Mucous membrane displays small rugae

176. Function of gold bladder
• Store bile, 30 to 60 millilitres
(when food fat enters GI , it stimulates cck . CCK
response contracts and releases by oddi )
• Absorption of water through the walls of the gall
• Bladder
• Release of stored bile.

177. Bile ducts
• Right and left hepatic ducts join to form common
hepatic duct
• Hepatic duct joined with a cystic duct (from the
gall bladder.)
• Cystic and hepatic ducts together form common
bile duct
• Common bile duct joined with main pancreatic
duct at the hepatopancreatic ampulla
• Hepatopancreatic ampulla by hepatopancreatic
sphincter conec with deodenum (sphincter of
oddi).

180. structure
• sam basic structure of the alimentary canal
• cystic duct irregularly situated circular folds in
mucus menbrain
• which have the effect of a spiral valve
• Bile passes through the cystic duct twice —
once

182. Metabolism
• All the chemical reactions that occur in the
body,
• Provide energy by chemical oxidation of
nutrients
• Two types of processes are catabolism and
anabolism
• There are three metabolic pathways
-Glycolysis
- Citric acid or krebs cycle
-Oxidative phosphorylation

183. Anabolism.
• Synthesis, of large molecules from smaller
ones
• needs a source of energy, usually ATP.
• Metabolic pathway controlled, by atp
intracellular 'explosions (on off –hormone)
• Both processes occur continuallyvery active
tissues,

184. Catabolism.
• Breaks down large molecules into smaller
ones
• Releasing chemical energy ,heat ,
• Energy stored as (ATP),
• Heat is used maintain core body temperature
and excreta by skin

185. Metabolic rate
• Energy is released from the fuel molecules
inside cells.
• Metabolic rate can be estimated by
measuring oxygen uptake or carbon dioxide
excretion

186. Metabolism of carbohydrate
• Erythrocytes and neurones can use only glucose
for fuel
• Most other cells can also use other sources of
fuel.
• After absorbed as glucouse , circulation to the
liver,and dealt with in several ways
• Glucose may be oxidised and form of ATP, takes
place in the liver

187. • Some glucose remaninig for maintain glucose
level of about 2.5 to 5.3 (mmol/l)
• Some glucose may be converted to the
insoluble polysaccharide, as glycogen,
• The hormone necessary for this change to take
place.-Adrenaline, thyroxine and glucagon

188. • Excess glucose and glycogen level is
converted to fat and stored in fat depots
• Glycogen can be used to maintain blood suger
levels or to provide ATP
• Liver, glycogen used for self activity and to
maintain the blood glucose level

189. .
• Muscle glycogen energy delivers to muscle
activity.
• need anergy multiplication of cells contraction
of muscle and synthesis of secretions(Gland)
• the body can make glucose from non-
carbohydrate sources, e.g. amino acids, glycerol.
(gluconeogenesis )

190. Carbohydrate and energy release
• Catabolism of glucose occurs in a sequence of
steps with a little energy being released at
each stage.
• The total number of ATP molecule 38, by one
glucous molecule
• Must occur in the presence of oxygen
(aerobically).
• Absence of oxygen
(anaerobically)reduced;ATP

191. Aerobic respiration (catabolism).
• Occur with oxygen supply is adequate,
• Energy is released during prolonged,
• Manageable exercise.
• When exercise levels become very forceful,
• energy requirements of increas
• Anaerobic breakdown then occurs.
• Accumulation lactic acidand reduce energy
production (pain)

192. • First stage of glucose catabolism is glycolysis.
• It anaerobic process takes place in cytoplasm
• Steps one glucose molecule is converted to
two molecules (pyruvic acid,+ 2 ATP).
• Pyruvic acid molecules to enter the citric acid
cycle -2 to 38 ATP

193. • The remaining 34 molecules of ATP enter the,
oxidative phosphorylation stage
• like the citric acid cycle, can occur only with
oxygen and takes place in the mitochondria
• Releas 34 ATP.

194. Anaerobic catabolism.
• Glycolysis of glucose with low o2
• split into two pyruvic acid, and 2ATP
• Pyruvic acid not enter the citric acid cycle or
oxidative phosphorylation;
• Instead it is converted lactic acid.Atp
• Now pain and cramps of muscles.
• When oxygen levels are restored, lactic acid is
reconverted to pyruvic acid, re start acid cycle
and oxidative pospolyration

195. End products of carbohydrate
• Carbon dioxide changed back to pyruvic acid.
• It is converted to glucose
• Carbon dioxide.- Excreted from body as a gas
by the lungs.
• Metabolic water. - Added and excess is
excreted as urine by the kidneys

197. Metabolism of protein
• There are 20 amino acids in body
• Devided as essential and non-essential
• Non-essential - they can be synthesised by
many tissues. Called transaminases.
• Essential-get by meal

198. • Amino acids required for building or repairing
Their specific type of tissue and for synthesising
their secretions, e.G. Antibodies, enzymes or
hormones..
• Cannot be stored and are broken down in the
liver.
• Deamination and excreted in the urine
• Provide energy, by remainig part by
gluconeogenesis, or stored as fat,

199. Sources of amino acids
• Exogenous. -These are derived from diet
• Endogenous. - from the breakdown of body
protein. In an adult about 80 to 100 g of
Loss of amino acids
• Deamination.
• Excretion.

200. Amino acids and energy release
• Use as potential fuel molecules-
• Used by the body only when other energy
sources are low, e.G. In starvation.
• To supply the amino acids for use as fuel the body
breaks down muscle,
• some amino acids can be converted directly to
glucose, and enters glycolysis.
• Other amino acids are changed to intermediate
compounds of central metabolic pathways, e.G.
Acetyl coenzyme A or oxaloacetic acid

201. Metabolism of fat
• Synthesized from carbohydrates and proteins
• Excess of protein and carbohydrate stored as
fat
• Fats absorbs as fatty acids and glycerol by
lacteals are transported to cisterna chyli
• Enter the bloodstream by the thoracic duct to
the bloodstream

202. • Used by the cells of organs and glands to
provide energy , synthesis their secretions.
• Liver some fatty acids and glycerol are used to
provide energy and heat,
• Some are recombined forming triglycerides,
form of flaty ascid -by liver

203. • Triglycerides are converted back to fatty acids
and glycerol to provide energy.
• End products of fat metabolism are energy,
heat, carbon dioxide and water.

204. Fatty acids and energy release
• Mainly fat stores use -when body
tissues are deprived of glucose, as
occurs in starvation, low-calorie diets
or in uncontrolled diabetes Mellitus
• Converted to acetyl coenzyme A, and
enter the energy production pathway
• Consequence - produce ketone
bodies, in the liver from
• Processing through the citric acid
cycle

205. • However, at high concentrations, ketones are
toxic, particularly in the brain.
• Uncontrolled diabetes mellitus, insulin
deficiency (hyperglycaemia). Accumulating
ketones are excreted by the lungs
• Give a sweet acetone-like smell to the breath.
• Excreted in the urine (ketonuria).

206. Glycerol and energy release
• The body converts glycerol from fats
• Into one of the intermediary compounds
produced
• During glycolysis, and in this form it enters the
central metabolic pathways.