THE DIGESTIVE SYSTEM
Mechanical &
Chemical breakdown
of food
Converts food into
energy & nutrients to
feed body
Consists of the
alimentary canal &
the accessory organs
ALIMENTARY CANAL
Muscular tube about
8 meters long
Passes through
thoracic &
abdominopelvic
cavities
ALIMENTARY CANAL
Consists of :
Mouth
Pharynx
Esophagus
Stomach
Small Intestine
Large Intestine
Rectum
Anus
ALIMENTARY CANAL WALL STRUCTURE
4 Layers
Mucosa
1. Protects tissue beneath
Submucosa
1. Nourishes surrounding tissues
Muscular Layer
1.Provides movement of the tube
Serosa
1.
Outer covering of tube
ACCESSORY ORGANS
Includes
 Salivary glands
 Liver
 Gallbladder
 Pancreas
MOUTH
Begins digestion
Mechanical
digestion
Receives food
CHEEKS & LIPS
Cheeks
•associates with
chewing and
expression
•Lateral walls of the
mouth
Lips
•Skeletal muscle
•Sensory receptors
TONGUE
 Skeletal muscle
 Mixes food
 Taste buds to
detect sensation
 Papillae provides
friction
 Lingual tonsils
 Lingual frenulum
PALATE
 Roof of oral
cavity
 Hard palate
 Soft palate
 Uvula
 Palatine tonsils
 Pharyngeal
tonsils
TEETH
 Breakdown food
mechanically
 Unique two structures
-primary
-secondary
 Types of teeth:
-incisors
-canines
- pre molars
- molars
 Enamel as protection
SALIVARY GLANDS
 Secrete saliva
 Bicarbonate breaks
down acid
concentration
 3 major glands
- Parotid
- submandibular
- sublingual
 Salivary amylase
 Mucus
PHARYNX
 Divided into 3 parts
-Nasopharynx
-Oropharynx
-Laryngopharynx
 Important
passageway
 Part of swallowing
mechanism
 Move food to
esophagus
SWALLOWING MECHANISM
ESOPHAGUS
 About 25 meters long
 Propels food from
pharynx to stomach
 Descends from
thorax to trachea
 Mucus glands
moisten & lubricate
 Closes stomach
entrance
 Prevents
regurgitation
STOMACH
STOMACH
Regions
1.Cardiac region
2.Fundus (Fundic) region
3.Body region
4.Pyloric (Antrum) region
•Function: churn/mix food
with gastric juices
(segmentation), send
chyme to small intestine
GASTRIC ENZYMES
Function of enzymes: Speed up breakdown of food molecules into their ‘building
block’ components
Reactions occur outside of cell lining the gut
•
Pepsin: degrades food proteins into peptides
•
Hydrochloric acid: break down foods and release enzymes to continue break
down
•
Intrisic factor: important for absorption of vitamin B12
•
Mucin: lubrication and signaling for cell barriers
•
Gastrin: aids in gastric motility
•
Rugae: Thick folds in the inner wall of the stomach that disappear when the
stomach is destended
REGULATION OF HORMONES IN THE DIGESTIVE
SYSTEM
*Hormones reach target cells by the circulatory system
Stimulating hormones of digestive process
• Cholecystokinin (CCK)
• Gastrin
• Ghrelin
• Secretin
Inhibiting hormones of digestive process
• Cholecystokinin (CCK)
• Gastric inhibitory polypeptide
• Enterogastrin
• Secretin
• Somatostatin
STIMULATING HORMONES
1.Cholecystokinin:
Site of production: Small intestine
Mucosa
Target Organ: Pancreas, Gallbladder,
Hepatopancreatic Sphincter
2.Gastrin:
Site of production: Stomach Mucosa
Target Organ: Stomach, Small
Intestine, Large Intestine
3.Ghrelin:
Site of production: Stomach
Target Organ: Brain
4.Secretin:
Site of production: Small Intestine
Mucosa
Target Organs: Pancreas, Liver
INHIBITING HORMONES
Cholecystokinin:
Site of production: Small Intestine Mucosa
Target Organ: Brain
2. Gastric Inhibitory Polypeptide:
Site of production: Small Intestine Mucosa
Target Organ: Stomach
3. Enterogastrin:
Site of production: Small Intestine
Target Organ: Stomach
4. Secretin:
Site of production: Small Intestine Mucosa
Target Organ: Stomach
5. Somatostatin:
Site of production: Stomach Mucosa, Small Intestine Mucosa
Target Organ: Stomach, Pancreas, Small Intestine, Gall
bladder
1.
PANCREAS
• Function:
Secretes digestive
juice, or pancreatic
juice
• Associated with
small intestine
• Located posterior
to parietal
peritoneum
PANCREATIC DUCT
Function:
•Transports
pancreatic juice to
small intestine
•Hepatopancreatic
Ampulla
•Hepatopancreatic
Sphincter
PANCREATIC JUICE
•After food enters the
duodenum the pancreas
secretes pancreatic juice
•Contains enzymes that
break down foods
•These enzymes digest
carbohydrates, fats,
proteins, and nucleic
acids
PANCREATIC ENZYMES
Carbohydrate- digesting enzyme:
Pancreatic Amylase: Splits molecules of starch or glycogen disaccharides
Fat-digesting Enzyme:
Pancreatic Lipase: Breaks triglyceride molecules into fatty acids & monoglycerides
Protein-Splitting (Proteolytic) Enzymes:
Trypsin, Chymotrypsin, Carboxypeptidase: Each split bonds between particular
combinations of amino acids in proteins, Secreted in inactive forms, Must be
activated by other enzymes
REGULATION OF SECRETION
• Nervous and endocrine systems
regulate secretion of pancreatic juice
• Stimulation of hormones:
• Secretin
• Cholecystokinin
LIVER
Functions:
•Carbohydrate
Metabolism
•Produces bile which
breaks down fats
•Takes glucose and turns
it into glycogen
•Storage
•Blood filtering
•Detoxification
GALLBLADDER
Function:
•Stores bile
•Bile exits
gallbladder and
enters small
intestine through
the bile duct they
share
SMALL INTESTINE
Tubular organ
that extends from
pyloric sphincter to
large intestine
Fills up most of
abdominal cavity
5.5-6 meters long
PARTS OF SMALL INTESTINE
Duodenum
-shortest & most fixed
portion of small intestine
-follows a C shaped path
as it passes anterior to R kidney &
3 upper lumbar vertebrae
Jejunum
-Proximal two fifths of
small intestine
-diameter of the wall is
thicker than ileum
Ileum
-remainder of small
intestine
-more lymph nodules
-higher bacterial
population
WALLS OF SMALL INTESTINE WALL
 Inner wall has a velvety appearance
 Intestinal villi, most numerous in duodenum and proximal parts of the jejunum
 Increase surface area of the intestinal linin, aiding absorption of digestive product
 Villi absorbs the fluid that intestinal gland secrete
ENZYMES OF THE SMALL INTESTINE
peptidases- which breaks down
peptides into amino acids
Sucrose, Maltase & Lactase –
breaks down disaccharides into
monosaccharides glucose,
fructose and glactose
Intestinal lipase – breaks down
fat into fatty acids & glycerol
Enterokinase shortens trypsin
Secretion is stimulated by
gastric juice, chyre, and reflexes
stimulated by expansion od the
small intestine
LARGE INTESTINE
Diameter is greater
than small intestine
Begins in lower right
side of the abdominal
cavity the ileum joins
cecum
Function: absorbs
water & electrolytes
-forms and stores
feces
-secretes mucus
PARTS OF LARGE INTESTINE
Consists of cecum, colon,
rectum & anal canal
Cecum: - beginning, pouch like
-vermiform appendix is
the worm like narrow tube that
closes the end (unknown digestion
function)
Colon: - Ascending colon –
begins at cecum & extends to
posterior abdominal wall to piny
inferior to the liver
- Transverse colon
– longest and most
moveable
- sags un the middle
below stomach
CONTINUED
- Descending Colon:
- Passes to left abdominal cavity to the brim of the pelivis
-Sigmoid Colon:
- S shaped part, descends from colon to rectum
-walls lack villi & plicae circularis
- longitudeinal muscle fibers don’t cover the wall
-small collections of fat in serosa on outer surface
- movements are similar to small intestine but slower
- peristaltic waves occur only 2 or 3 times a day
- waves produce mass movements which large secretion of wall
constricts inside to move toward rectum
RECTUM
Firmly attached to
sacrum by
peritoneum
Ends about 5 cm
inferior to tip of
coccyx
Regulates
elimination of feces
ANAL CANAL
Formed by last 2.5 – 4 cm of large
intestine
Mucus membrane in canal folded
in series of 6-8 longitudinal canals
Distal ends of canal opens to the
outside as the anus
2 sphincter muscles guard the
anus
Internal anal sphinter muscles,
involuntary control, smooth muscle
External anal sphinter muscle,
skeletal muscle voluntary control
DIGESTION VIDEO
WORKS CITED
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