DO NOW:Digestive Enzymes Pre-Lab
• What molecule does our body break down
for energy?
• Where do we get this molecule?
• Recall from Biology Lab, what do Iodine
and Benedict’s solution test for?
• Explain the reactions of these two
indicators.
Objectives
• To use your knowledge of indicators and
macromolecules to determine the effects
of digestive enzymes.
• To explain how digestion begins in the
mouth.
Do Now
• What do we already know about the
digestive system? List 3 things!
• What would happen if you were tied
upside down, would you still be able to
eat? Explain.
The Digestive System!
Chapter 15
Objectives
• To compare and contrast chemical vs.
mechanical digestion.
• To explain the general characteristics of the
alimentary canal.
• To explain the process of swallowing and
peristalsis.
• To identify the structures of the mouth and
explain their function.
• To understand the necessity of salivary glands
and name each type.
Digestion
• Chemical digestion- complex molecules are
broken down into smaller molecules
• Mechanical digestion- physical movement of
food that breaks it down into smaller pieces
– Ex. Chewing, grinding, mashing
– Chewing is called “mastication”
Components of Digestive System
• Alimentary Canal
– “digestive tract”
– Mouth, pharynx,
esophagus, stomach, small
intestine, large intestine,
and anal canal
• Accessory Structures:
– Salivary glands, liver,
gallbladder, & pancreas
Alimentary Canal
• Muscular tube that
passes through the
body’s ventral
cavity
• 9 meters long
• Contains 4 layers
Alimentary Canal
1) Mucosa:
– Protects the tissues beneath it & carries out
secretion and absorption
– Consists of epithelium, underlying CT, and a little
bit of muscle.
2) Submucosa:
– Nourishes surrounding tissue and carries away
absorbed materials
– Consists of loose connective tissue, blood vessels,
glands.
Alimentary Canal
3) Muscular Layer:
– Layer which moves the tube
– Contains: Two coats of smooth muscle tissue & nerves
(plexus)
– Fibers of the inner coat surround the tube
• When they contract the tube’s diameter decreases
– Fibers on the outer muscular coat run lengthwise
• When they contract the tube shortens
4) Serosa:
– Protects underlying tissues and secrete serous
fluid
Alimentary Canal
Movements of theAlimentary Canal
• Mixing Movement
– Occurs when smooth
muscle in small units of
the tube contract
rhythmically
– Mixes food with
digestive juices
secreted by the mucosa
• Propelling Movement
– Known as peristalsis
Organs of the Digestive System
•
•
•
•
The Mouth
Receives food and begins
digestion mechanically
Reduces the size of solid
particles and mixes them
with saliva
Oral cavity - Lips, cheeks,
tongue & palate
Vestibule - Narrow space
between teeth, cheeks, &
lips
Salivary Glands
• Secrete saliva
• Contain 2 cells
– Serous cells:
produce amylase
(breaks down
carbs)
– Mucus cells:
produce mucus to
bind to food and
lubricate during
swallowing.
Pharynx
• Connects nasal and
oral cavities
• Contains 3 parts
– Nasopharynx
– Oropharynx
– Laryngopharynx
(passageway to the
esophagus)
Swallowing Mechanism
1. Food is chewed and mixed with
saliva,tongue rolls this into a mass or
bolus and forces it into the pharynx
2. Food stimulates sensory receptors
around the pharyngeal opening triggering
the swallowing reflex.
3. Momentarily inhibits breathing,
peristalsis transports food into the
esophagus and to the stomach.
Do Now
1) Read the story about William Beaumont
and his work with St. Martin in the early
1800s.
3) Write a short summary of what you read.
Objectives
• Explain the functions of the esophagus,
stomach, small intestines, and large
intestines in digestion.
• Identify different enzymes located in the
digestive system and explain their
function.
• Understand different conditions caused by
improper functioning of the digestive
system.
Swallowing Mechanism
Esophagus
• About 25 cm long
• Connects pharynx
to the stomach
• Separated from the
stomach by the
cardiac sphincter.
• Contracts and
closes the sphincter
to prevent
regurgitation.
Heartburn!
• Regurgitation of
stomach acid into
the esophagus.
Stomach
• J shaped with about
a 1 liter capacity.
• Contains rugae
which allow it to
expand
• Divided into 4
regions
–
–
–
–
Cardiac
Fundic
Body
Pyloric
Stomach
Stomach Ulcers
• Breaking down of
the mucosal lining.
Stomach Juices
• “Gastric Juice”
consists of…
– HCl
– Mucus
– Viscous alkaline
secretion that coats
the stomach
– Enzymes
• Proteases such as
Pepsin- digests
protein (starts as
pepsinogen and
when mixed with HCl
makes pepsin)
– Intrinsic factor which
helps the small
intestine absorb B12
Stomach Juices
• The mixture of gastric
juice and the bolus
gives us chyme.
• Stomach contractions
push chyme a little at a
time into the sm.
Intestine.
• Type of food can effect
rate of emptying
– Fatty food = 3-6 hrs. in
stomach
– Proteins move more
quickly
– Carbs go through the
fastest!
Gastric Absorbtion
• The stomach
mostly breaks
things down
• Can absorb only
small amounts of
water, certain salts,
alcohol, and some
lipid-soluble drugs.
– EX: Aspirin
Pancreas
• Secretes pancreatic
juice into the
duodenum (1st part
of sm. Intestine)
• Pancreatic enzymes:
– Pancreatic amylase
• Digests carbs
– Pancreatic lipase
• Digests fats
– Nucleases
• Digests nucleic acids
– Proteases: trypsin,
chymotrypsin &
carboxypeptidase
• Digest protein
Liver
• Effects
carbohydrate, lipid,
and protein
metabolism.
• Produces bile
– Contains bile salts,
bile pigments
(bilirubin and
biliverdin)
– **bile salts emulsify
fats (turn them into
little globs instead of
big globs!) and also
increase absorption
of fat-soluble
vitamins (A,D,E, & K)
Review
• What is the process that occurs after
swallowing?
• What is the scientific name for the
digestive tract?
• How many layers is this tract?
• What are the 3 parts of the pharynx?
• What is absorbed in the stomach?
• What does the pancreas do?
• Why are bile salts important?