The document discusses the anatomy and functions of the digestive system. It describes the organs of the alimentary canal including the mouth, esophagus, stomach, small intestine, and large intestine. It details the layers of the digestive tract walls and the roles of various glands and tissues in ingestion, digestion, absorption, and defecation. Key processes like peristalsis and the roles of enzymes are also summarized.
2. Function of the digestive system
ingestion: taking food and liquid into
mouth
Secretion: total about 7 liter into lumen
Mixing and propulsion: through GI
muscle and peristalsis and motility
Digestion: Breakdown of ingested food
(mechanical and chemical)
Absorption: Passage of nutrients into the
blood
Metabolism: Production of cellular
energy (ATP)
Defecation: waste substance leave the
GI tract through anus
3. Organs of the Digestive System
Two main groups
Alimentary canal or gastrointestinal tract –
continuous coiled hollow tube from mouth to
anus(5-7 meter)
Accessory digestive organs: teeth ,tongue
,salivary gland ,liver ,gallbladder ,and
pancreas
5. Organs of the Alimentary Canal
Mouth
Pharynx
Esophagus
Stomach
Small intestine
Large intestine
Anus
6.
7. Mouth (Oral Cavity) Anatomy
Lips (labia) – protect
the anterior opening
Cheeks – form the
lateral walls
Hard palate – forms
the anterior roof
Soft palate – forms
the posterior roof
Uvula – fleshy
projection of the
soft palate
8. Mouth (Oral Cavity) Anatomy
Vestibule – space
between lips
externally and teeth
and gums internally
Oral cavity – area
contained by the
teeth
Tongue – attached
at hyoid bone and
styloid processes of
the skull, and by the
lingual frenulum
9. Tongue
Dorsum (upper part of
tongue covered with papillae
taste receptor and buds)
filiform papillae
fungiform papillae
circumvallate papillae
Paltine tonsil and
lingual tonsil
10. Salivary glands
-Parotid gland: In the parotid fossa, three main
structures transverse this gland – facial nerve,
external carotid artery, and retromandibular
vein. The parotid duct opens near the upper 2nd
molar tooth. The gland is completely serous.
-Submandibular gland: Sitting most
posteriorly in the submandibular triangle, it is
supplied by the facial artery and vein.
Submandibular ducts, which cross the lingual
nerves, open on both sides of the tongue
frenulum. It is mostly serous but partially
mucus,.
-Sublingual gland: The smallest salivary
gland sits beneath the oral mucosa in the floor
of the mouth. It has multiple small openings.
This gland is almost completely mucus-
secreting.
11. Teeth
• Teeth
(mechanical breakdown)
– Incisors used for cutting
– Canines used for stabbing
and holding
– Molars large surface area
used for grinding
• Primary or deciduous
teeth 20
• Secondary or permanent
teeth 32
12. Structure of Teeth
Crown - exposed surface of tooth
Neck - boundary between root and crown
Enamel - outer surface (the hardest substance in the
body 95% calcium salts)
Dentin – bone-like, but noncellular(70% calcium
salts)
Pulp cavity - hollow with blood vessels and nerves
Root canal - canal length of root
gingival sulcus - where gum and tooth meet
13. Processes of the Mouth
Mastication (chewing) of food
Mixing masticated food with saliva to
produse easy digestied food called
bolus
Saliva contain 2 enzyme,salivary
amylase and lingual lipase
Initiation of swallowing by the tongue
Allowing for the sense of taste
14. Layers of Alimentary Canal Organs
Submucosa
Just beneath the mucosa
Soft connective tissue with blood vessels,
nerve endings, and lymphatics also contain
submucosal plexus
15. Layers of Alimentary Canal Organs
Mucosa
Innermost layer
Moist membrane
1. Surface epithelium : secretion and
absorbtion,renew every 5-7 days also
contain enteroendocrine cells
2. Small amount of connective tissue
(lamina propria): contain blood and
lymphatic vessele also contain MALT
3. Small smooth muscle layer
16. Layers of Alimentary Canal Organs
Muscularis externa – smooth muscle
1. Inner circular layer
2.Outer longitudinal layer
Between them is myenteric plexus
Serosa
Outermost layer – visceral peritoneum
Layer of serous fluid-producing cells
(mesothelium)
19. Pharynx Anatomy
Nasopharynx –
not part of the
digestive system
Oropharynx –
posterior to oral
cavity
Laryngopharynx –
below the oropharynx
and connected to
the esophagus
20. Pharynx Function
Serves as a passageway for air and
food
Food is propelled to the esophagus by
two muscle layers
Longitudinal inner layer
Circular outer layer
Food movement is by alternating
contractions of the muscle layers
(peristalsis)
21. Esophagus
Runs from pharynx to stomach through
the diaphragm( 25 cm)
Conducts food by peristalsis
(slow rhythmic squeezing): contraction
of circular layer above the food and
contraction of longitudinal below the
food
Passageway for food only (respiratory
system branches off after the pharynx)
22. Esophagus
-The esophagus is posterior to the larynx
and trachea in the neck region and upper
thorax. It travels on the right side of the
descending aorta, passes through the
diaphragm, and connects with the
stomach.
-There are also inner circular and outer
longitudinal muscle layers.
-The upper third is skeletal muscle
(voluntary), middle third is mixed, and lower
third is smooth muscle (involuntary).
-esophagogastric junction is located
approximately at the level of the diaphragm.
Contractions of the diaphragm create sphincter-
like effects, preventing reflux of stomach acids
and content. The esophagogastric junction is a
functional, not anatomical, sphincter.
23. Peristalsis in Esophagus
Bolus of
food
Muscles relax,
allowing
passageway
to open
Stomach
Muscles
contract,
constricting
passageway
and pushing
bolus down
Muscles
relax
Muscles contract
Muscles relax
Muscles contract
24. Stomach Anatomy
Located on the left side of the
abdominal cavity
Food enters at the
cardioesophageal sphincter
Site where food is churned into chyme
Protein digestion begins
25. Stomach Anatomy
Regions of the stomach
Cardiac region – near the heart
Fundus
Body
Phylorus – funnel-shaped terminal end
Food empties into the small intestine at
the pyloric sphincter
29. Stomach Anatomy
Layers of peritoneum attached to the
stomach
Lesser omentum – attaches the liver to the
lesser curvature
Greater omentum – attaches the greater
curvature to the transverse colon which
Contains fat to insulate, cushion, and
protect abdominal organs
33. Stomach Functions
Acts as a storage tank for food
Site of food breakdown and mixing
Chemical breakdown of protein begins
Delivers chyme (processed food) to the
small intestine
34. Specialized Mucosa of the
Stomach
Simple columnar epithelium
Mucous neck cells – produce a sticky
alkaline mucus
Gastric glands – secrete gastric juice
Chief cells – produce protein-digesting
enzymes (pepsinogens)
Parietal cells – produce hydrochloric acid
and Intrinsic factor(B12 absorption)
Endocrine cells (G cell) – produce gastrin
which stimulates both parietal and chief cells)
35. Structure of the Stomach Mucosa
Gastric pits
formed by
folded mucosa
Glands and
specialized
cells are in the
gastric gland
region
37. Peritoneum
•
•
Is the largest serous membrane of the body consist of
mesothelium
Divide into
1. Parietal peritoneum: lines the wall of abdominopelvic
cavity internally
2. Visceral peritoneum: cover some oh the organs in the
cavity
3. The space between them contain fluid and called
peritoneal cavity this cavity may be accumulated by
several liters of fluid state called ascites
38. Membranes
Mesenteries - double sheets of peritoneum, surrounding and
the digestive
suspending portions of
organs
Peritoneal folds
•
1. falciform ligament:- attach the liver to anterior abdominal
wall and diaphragm
2. Greater omentum - "fatty apron", hangs anteriorly from
stomach, double layer encloses fat
3. Lesser omentum - between stomach and liver
4. Mesentery proper - suspends and wraps the small intestine
5. Mesocolon - suspends and wraps the colon, parts are
i. transverse mesocolon
ii. sigmoid mesocolon
Ascending and descending ,pancreas, first 2 parts of the
duodenum and kidneys are Retroperitoneal structure
42. Small Intestine
The body’s major digestive organ
Site of nutrient absorption into the blood
Muscular tube extending form the
pyloric sphincter to the ileocecal valve
Suspended from the posterior
abdominal wall by the mesentery
43. Subdivisions of the Small Intestine
Duodenum(25cm)
Attached to the stomach
Curves around the head of the pancreas
Fixed retroperitoneal structure
Jejunum (2.5m)
Attaches anteriorly to the duodenum
Ileum (3.5m)
Extends from jejunum to large intestine
46. Duodenum and Related Organs
Liver
Bile
Gall-
bladder
Bile
Duodenum of
small intestine
Acid chyme
Pancreatic
juice
Intestinal enzymes
Stomach
Pancreas
51. Folds of the Small Intestine
Called circular folds or plicae circulares
Deep folds of the mucosa and
submucosa
Do not disappear when filled with food
The submucosa has Peyer’s patches
(collections of lymphatic tissue)
52.
53.
54.
55.
56.
57.
58.
59. Digestion in the Small Intestine
Enzymes from the brush border
Break double sugars into simple sugars
Complete some protein digestion
Pancreatic enzymes play the major
digestive function
Help complete digestion of starch
(pancreatic amylase)
Carry out about half of all protein digestion
(trypsin, etc.)
61. Digestion in the Small Intestine
Pancreatic enzymes play the major
digestive function (continued)
Responsible for fat digestion (lipase)
Digest nucleic acids (nucleases)
Alkaline content neutralizes acidic chyme
62. Absorption in the Small Intestine
Water is absorbed along the length of
the small intestine
End products of digestion
Most substances are absorbed by active
transport through cell membranes
Lipids are absorbed by diffusion
Substances are transported to the liver
by the hepatic portal vein or lymph
63. Propulsion in the Small Intestine
Peristalsis is the major means of
moving food
Segmental movements
Mix chyme with digestive juices
Aid in propelling food
64. Digestive Secretions:
(7 L / Day From Tissues into
Lumen)
• Salivary glands
• Pancreas
• Water
• Enzymes
• Mucus
• Ions: H+, K+, Na+
• HCO3
-, Cl-
• Mass Balance (H2O)
65. Large Intestine
Larger in diameter, but shorter than the
small intestine
Frames the internal abdomen
67. Regions of Large Intestine
Cecum – pocket at proximal end with
Appendix
Colon
Ascending colon - on right, between
cecum and right colic flexure
Transverse colon - horizontal portion
Descending colon - left side, between
left colic flexure and
Sigmoid colon - S bend near terminal
end
Rectum – terminal end is anal canal - ending at the anus -
which has internal involuntary sphincter and external voluntary
sphincter
68. 1. Mucosa - abundant goblet cells, stratified
squamous epithelium near anal canal
2. No villi
3. Longitudinal muscle layer incomplete, forms
three bands or taenia coli
4. Circular muscle - forms pockets or haustra
between bands
Histology of Large Intestine
69. Functions of the Large Intestine
Absorption of water
Eliminates indigestible food from the
body as feces
Does not participate in digestion of food
Goblet cells produce mucus to act as a
lubricant
70. Structures of the Large Intestine
Cecum – saclike first part of the large
intestine
Appendix
Accumulation of lymphatic tissue that
sometimes becomes inflamed
(appendicitis)
Hangs from the cecum
71. Structures of the Large Intestine
Colon
Ascending
Transverse
Descending
S-shaped sigmoidal
Rectum
Anus – external body opening
72. Food Breakdown and Absorption in
the Large Intestine
No digestive enzymes are produced
Resident bacteria digest remaining
nutrients
Produce some vitamin K and B
Release gases
Water and vitamins K and B are absorbed
Remaining materials are eliminated via
feces
73. Propulsion in the Large Intestine
Sluggish peristalsis
Mass movements
Slow, powerful movements
Occur three to four times per day
Presence of feces in the rectum causes
a defecation reflex
Internal anal sphincter is relaxed
Defecation occurs with relaxation of the
voluntary (external) anal sphincter
74. Saliva
Mixture of mucus and serous fluids
Helps to form a food bolus
Contains salivary amylase to begin
starch digestion
Dissolves chemicals so they can be
tasted
77. Pancreas
Produces a wide spectrum of digestive
enzymes that break down all categories of food
Enzymes are secreted into the duodenum
Alkaline fluid introduced with enzymes
neutralizes acidic chyme
Endocrine products of pancreas (langerhans
island)
Insulin
Glucagons
Somatostatin
80. Composition and Function of
Pancreatic Juice
• Examples include
• Trypsinogen is activated to trypsin
• Procarboxypeptidase is activated to
carboxypeptidase
• Active enzymes secreted
• Amylase, lipases, and nucleases
• These enzymes require ions or bile for
optimal activity
81. • Retroperitoneal :compose
of head, body and tail
• Endocrine and exocrine
gland
• Common bile duct and
major pancreatic duct lead
to ampulla of vater then to
second part of duodenum
through sphincter of oddi
Pancreas
82. Liver
Largest gland in the body
Located on the right side of the body
under the diaphragm
Consists of four lobes suspended from
the diaphragm and abdominal wall by
the falciform ligament
Connected to the gall bladder via the
common hepatic duct
83. Liver
e
,
On right under diaphragm,
largest organ made up of 4
lobes (left and right, caudat
and quadrate)
Hilus (porta hepatis) –
underside "entry" point
Gall bladder
Microscopic anatomy: Liver lobules and triads
86. Role of the Liver in Metabolism
Several roles in digestion
Detoxifies drugs and alcohol
Degrades hormones
Produce cholesterol, blood proteins
(albumin and clotting proteins)
Plays a central role in metabolism
87. Bile
Produced by cells in the liver
Composition
Bile salts
Bile pigment (mostly bilirubin from the
breakdown of hemoglobin)
Cholesterol
Phospholipids
Electrolytes
88. Gall Bladder
Sac found in hollow fossa of liver
Stores bile from the liver by way of the
cystic duct
Bile is introduced into the duodenum in
the presence of fatty food
Gallstones can cause blockages
90. Gallbladder
• Stores and concentrates bile to ten folds
• Expels bile into duodenum
– Bile emulsifies fats
91. Processes of the Digestive System
Ingestion – getting food into the mouth
Propulsion – moving foods from one
region of the digestive system to
another
92. Processes of the Digestive System
Peristalsis – alternating
waves of contraction
Segmentation – moving
materials back and forth
to aid in mixing
93. Processes of the Digestive System
Mechanical digestion
Mixing of food in the mouth by the tongue
Churning of food in the stomach
Segmentation in the small intestine
94. Processes of the Digestive System
Chemical Digestion
Enzymes break down food molecules into
their building blocks
Each major food group uses different
enzymes
Carbohydrates are broken to simple sugars
Proteins are broken to amino acids
Fats are broken to fatty acids and alcohols
97. Control of Digestive Activity
Mostly controlled by reflexes via the
parasympathetic division
Chemical and mechanical receptors are
located in organ walls that trigger
reflexes
98. Nutrition
Slide
Nutrient – substance used by the
body for growth, maintenance, and
repair
Categories of nutrients
Carbohydrates: simple sugars, starches,
fiber
Lipids: triglycerides, phospholipids, fatty
acids
Proteins: amino acids
Vitamins
Mineral
Water