Digestive System
Digestive System

3 main functions
– Digestion
– Absorption
– Elimination

2 main divisions
– Alimentary canal
• Tube from mouth to
anus
– Accessory organs
• Aid in digestion
Digestive System

Digestion
– Process of breaking
down food into
molecules the body
can absorb.

Absorption
– Process of molecules
passing from the
alimentary canal to
blood stream.

Elimination
– Process of the
body getting rid
of unabsorbed
solids and
liquids
• Feces
• Urine
Alimentary Canal

Tube from mouth to
anus
– Mouth / oral cavity
• Ingestion
– Putting food in your
mouth
• Mastication
– Chewing
• Bolus
– Mass of chewed
food
Alimentary Canal

Throat / Pharynx
– Connects mouth to
esophagus
– 3 sections
• Nasopharynx
• Oropharynx
• laryngopharynx
– Deglutition
• swallowing
Alimentary Canal

Esophagus
– Connects throat to
the stomach
• Epiglottis
– Covers the
trachea during
swallowing
– Peristalsis
• Contraction of
smooth muscle to
move food through
digestive tract.
Alimentary Canal

Stomach
– Sac like organ
• Bolus mixes with
gastric juices…
– Hydrochloric acid
– Pepsin
• Chyme
– Soupy mass of food
and gastric juices
– Digestion continues
– Absorption begins
Alimentary Canal

Small intestine
– Connects stomach to
the large intestine
– 3 main parts
• Duodenum
• Jejunum
• Ileum
– Most nutrient absorption
occurs here.
– Fat is broken down by
bile.
Alimentary Canal

Large intestine
– 3 main sections
• Cecum
• Colon
• Rectum
– Anus
– Opening to the
rectum
– Elimination occurs
here
Accessory Organs

All the organs that
aid in the digestive
process.
–
–
–
–
–
–
–
Teeth
Salivary glands
Saliva
Tongue
Muscles
Liver
Pancreas
Accessory Organs

Teeth
–
–
–
–
Incisors – cut
Cuspids – tear
Premolars – chew
Molars – grind,
chew
• Chewing
– mastication
• Mechanical break
down of food.
Accessory Organs
– Saliva glands
• 3 pair
– Parotid
– Sublingual
– Submandibular
• Produce saliva
– Saliva
• Lubricates food
• Enzyme
– Salivary amylase
– Chemically
breaks down food
Accessory Organs

Tongue (glossus muscle)
– Moves and holds food between teeth.
– Moves food (bolus) towards throat.

Muscles
– Mastication =
• chewing
– Deglutition =
• swallowing
– Paristalsis =
• contraction of smooth muscle
Accessory Organs

Liver
– Produces bile
• Breaks down fat
for absorption
• Stored in the
gallbladder
• Yellowish-green
alkaline fluid
• Found in small
intestine
Accessory Organs

Pancreas
– Produces and
secretes
pancreatic juices
containing
digestive enzymes
• Empty into small
intestine
• Completes the
breakdown of
carbohydrates
Conclusion
Understanding the digestive is very
important.
 Teeth are organs of the digestive
system, and tooth decay (caries) is
a disease of the digestive system.
 Any questions??
