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Digestive System
General Function
Physical/ chemical breakdown of
foods so it can be absorbed into the
bloodstream and used by the cells/
tissues and eliminate non-digestible
substances produced during
metabolism
Function
• Digestion- Conversion process of food
• Absorption- Digested nutrients are
transferred to the blood stream
• Elimination- Waste products removed from
the body
Digestion
• Process of changing foodstuffs into usable
substances
• mechanical
• chemical
Digestive process cont.
• Mechanical digestion: physical preparation
of food for chemical digestion, mixing of
food with saliva by tongue, churning an d
mixing of food in stomach, segmentation, in
intestine
• Chemical digestion: catabolic process in
which large food molecules are broken
down into smaller molecules by enzymatic
hydrolysis
Digestive Process
• Ingestion: process of taking food into
the digestive tract
• Propulsion: process of moving food
through the alimentary canal
(swallowing, peristalsis)
Continued
• Absorption: transported of digested end
products from the GI tract into the
capillaries and lymph vessels
• Defecation: elimination of indigestible
materials and waste form the body
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Structures of the Alimentary Canal
• Approximately 30 Ft. long
• Oral Cavity: Mouth (stoma)
receives and tastes food
physical breakdown of food
partial digestion by saliva
lubricate food
• hard palate: bony structure, separates mouth
from nasal cavity
Salivary Glands
• Parotid; at ear/ upper jaw
• Submandibular and sublingual
• Saliva: lubricates food for swallowing
and helps with speech, body produces
1500 cc/ 24 hrs.
• Contains enzyme (salivary amylase)
which begins chemical breakdown of
CHO and starches into sugar
Tongue
• Muscular organ with taste buds
(sweet, salt, sour, bitter) on sides of
papillae
• Maintain placement of food for
chewing and swallowing and
speech
Teeth
• 20 deciduous teeth form 6 months to 2 years
• 32 permanent teeth; incisors, canines,
premolars, molars, cuspids, bicuspids
• Enamel, dentin, pulp cavity, cementum
• mastication: chewing
• Bolus: Mass of chewed food
Pharynx and Esophagus
• Passageway 10 inches long, food only
here 4-8 secs., no chemical change takes
place
• Pharynx: throat tube that carries food and
air
• Epiglottis: flap that covers the trachea
(windpipe) when food or water is
swallowed
Esophagus
• Muscular tube behind the trachea, carries
food to the stomach by rhythmic wavelike
motion (peristalsis)
• Stricture: narrowing due to trauma,
infection, spasms, tumors
• Regurgitation: backward flow of food from
stomach to esophagus
• Reflux esophagitis: inflammation due to
regurgitation
Stomach
• Food stays in stomach for 3-4 hours for
physical and chemical breakdown
• LUQ
• Fundus, body, antrum
• Rugae folds in stomach to increase surface
area
• Sphincters: cardiac and pyloric, prevent
reflux
Stomach
Gastric Enzymes
• Pepsin (protein)
• rennin lipase (fats)
• HCL ( kills bacteria, helps in absorption of
Fe, activates pepsin)
• Chyme (gastric juices plus digested food)
Small Intestine
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Approximately 21 Ft. long/ 1 inch diameter.
80% of absorption occurs here, 3 sections
Duodenum (10-12 inches)
Jejunum (8 feet)
Ileum (final 12 feet)
Duodenum
• Receives chyme
• Pancreatic juice: amylopsin (sugars), trypsin
(proteins), lipase (fats)
• Gallbladder: bile (emulsifies and breaks
down fats)
• Intestinal juices; maltase/sucrase/lactase
(breakdown sugars)
Ileum
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Connects to large intestine at cecum
process of digestion completed
Most absorption occurs here
Villi, fingerlike projections containing
blood capillary loop and lymphatic vessels
for absorption
• Enzymes stimulate intestinal secretions
• Hormones inhibit intestinal secretions
Large Intestine
• 5 feet/ 2 inches in diameter
• Ileocecal valve: circular, shincter muscle,
prevents food from returning to ileum
• Cecum: blind pouch at beginning of large
intestine, lower end is appendix
• Colon: absorbs water, remaining nutrients,
electrolytes, storage of indigestible material
until elimination, transport waste
Colon
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Ascending (right)
Transverse
Descending (left)
Sigmoid
Rectum: Final 6-8 inches, storage of feces
Anal Canal: Outlet of rectum; 2 sphincters
Fecal matter non-digestible waste products
and bacteria
Accessory Organs
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Liver
Gallbladder
Pancreas
Salivary Glands
Tongue
Teeth
Liver
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Largest gland/ solid organ of the body
RUQ under diaphragm
secretes one liter of bile every 24 hours
Biliary tree
Function of liver
• Function: Manufacture blood proteins (ie
antibodies and blood clotting factors (ie.
Heparin)
• Stores iron, copper, vitamin A/D/B12 and
glycogen
• Produces bile for fat digestion
• Detoxifies blood (poisons absorbed in small
intestine)
Gallbladder
• Pear shaped muscular sac under the liver
• Stores bile (500- 600 ml stored)
• Fatty foods enter duodenum and stimulate
CCK hormone which contracts Gallbladder
to release bile and emulsify fat and
stimulate peristalsis
• Bile pigment: bilirubin
Pancreas
• Behind the stomach; head attached to
stomach and tail attached to spleen
• Exocrine functions:acini cells secrete
digestive juices and bicarbonate ions (adjust
pH)
• Endocrine functions: Carbohydrate
metabolism (CHO)
• Insulin and Glucagon secreted for CHO
metabolism
The End
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Digestive Diseases