Digestive System
Joe Cristofano
Billy Sieff
Cnidarian Digestive
system
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Cnidarians have a unique digestive cavity
called the Gastrovascular cavity.
The two body plans for cnidaria are Polyps
and Medusa.
Cnidarian Digestive
system
• The gastrovascular cavity has only one
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opening which functions as both a mouth
and an anus.
The gastrovascular cavity is responsible for
not just digestion but also the distribution of
the nutrients being digested.
Cnidarian Digestive
system
Hydra, a carnivorous Cnidarian is a good
example.
It uses its tentacles to shove its prey through
its mouth into the gastrovascular cavity.
Then the Gastrodermis(the inside layer of
its epidermis) will release digestive enzymes
into the cavity.
The enzymes break down soft tissue of the
prey and then other specialized cells in the
gastrodermis will engulf the food particles.
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Cnidarian Digestive
system
• All undigested materials remaining in the
gastrodermis and then released out of the
singular opening.
Cnidarian advantages and
adaptations
• Cnidaria are not very complex organisms
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and it makes for a simple life.
The tentacles make it easy to pull in prey
and due to the simple body plan, they have a
gastrovascular cavity, and the lining of it
distributes the nutrients directly to the
necessary parts of the organism.
Annelida Digestive Tract
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In typical annelids such as earthworms and
flatworms, the alimentary canal usually
includes a muscular pharynx whose purpose
is to draw food into the mouth.
Annelida Digestive Tract
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Food then moves through the esophagus
down into the crop, a compartment used for
storing and moistening food.
food moves from the crop to the gizzard.
This is where mechanical digestion takes
place.
The muscular gizzard crushes and breaks
down food, often with the aid of small grains
of gravel and sand previously ingested.
Annelida Digestive Tract
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Further digestion and absorption continues
to take place in the intestine. Waste
productions are then excreted through the
anus.
Annelida Digestive
Adaptation
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One adaptation in most annelids (especially
earthworms and flatworms) is their muscular
gizzards, whose thick,tough, rigid walls of
muscle allow them to keep particles of sand
and gravel within their gizzards for extended
periods of time to allow for further
breakdown of food.
This is an imperative adaptation for
invertebrates who spend most of their time
on or underneath the ground.
Arthropod Digestive Tract
• Arthropod digestive systems are
normally composed of 3 general
sections of several digestive
chambers, the foregut, midgut, and
hindgut.
Arthropod Digestive Tract
• The foregut is composed of the
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esophagus and the crop.
The midgut is primarily made of
gastric cecae, which are pouches
that extend from the beginning of the
midgut and play large roles in
absorption and digestion.
The hindgut is comprised of a rectum
Arthropod Digestive Tract
Arthopod Adaptations
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Multiple pouches of gastric cecae allow for
large amounts of food to be processed and
digested simultaneously.
Multiple sections for the digestive tract within
the foregut, midgut, and hindgut allow for
more space for the crop, gastric cecae, and
gizzards.
Mammalian Digestion
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Most animals have an
Alimentary Canal
(digestive tract or tube
with a separate
entrance and exit)
Mammalian digestive
system consists of an
alimentary canal and
accessory glands to
release digestive fluids
Digestive Pathway
• In order for food particles and nutrients to
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travel through the alimentary canal,
peristalsis must occur.
Peristalsis is the alternating, wave-like
contraction/relaxation of the smooth muscle
in the digestive tract. This action pushes the
nutrients through the tract.
Digestive Pathway
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Sphincters are valves found the
junctions between compartments that act
like clamps or drawstrings, closing and
opening to allow food particles to pass or
not pass.
With the human digestive system as an
example, the initial step of the process is
the entrance through the oral cavity.
Oral Cavity
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Teeth in the mouth mash, grind and break
down food into smaller chunks.
Salivary glands are stimulated by the
presence of food and they release saliva into
the oral cavity through ducts.
Saliva starts the process of breaking down
the food while it also protects the oral cavity.
3 pairs of salivary glands
Saliva
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Amylase is the enzyme found in saliva.
It hydrolyzes starch & glycogen into smaller
polysaccharides and maltose ( a disaccharide).
Mucus is responsible for most of the protective
effect.
it is a mixture of water, salts, cells and slippery
glycoproteins, these make it very viscous.
Mucus mainly protects the lining of the oral
cavity from abrasion and it also is a lubricant
for food traveling through the tract.
Beginning of Digestive
Tract
• The tongue is vital for digestion, because is
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decides what needs to be digested and what
doesn't.
The tongue also pushes food down into the
Pharynx or throat.
When moving the food towards the pharynx,
the tongue molds the food into a Bolus (ball
shape)
The tongue aids in pushing downward during
swallowing and official entering the Pharynx.
Digestive Tract
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At the bottom of the Pharynx there are 2
openings to the Larynx (wind-pipe) and the
esophagus ( connects to stomach).
The Epiglottis is a flap of cartilage that will
flip up or down covering up either the Larynx
or Esophagus in order for breathing or
swallowing food.
swallowing directs the bolus into the
esophagus, and if it fails the food one is
currently digesting could reach the Trachea,
Stomach
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The stomach is where food is stored and
begins digestion of proteins.
Due to the elasticity of the lining of the
stomach, it can hold up to about 2 L of
food/drink on average.
Gastric Juice is secreted by the stomach
mixes with the food while it is being churned,
the mixture is called Chyme.
Gastric glands in the stomach produce the
gastric juice
Stomach
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Two components of gastric juices catalyze
chemical digestion.
One of which is Hydrochloric Acid (HCl
HCl has a very low pH,making it acidic
enough to dissolve iron nails!
The second is pepsin, a protease (protein
digesting enzyme).
Stomach
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Parietal cells secrete hydrogen and chloride
ions to create HCl.
Chief cells release inactive pepsin into the
lumen. This inactive pepsin is known as
pepsinogen.
Small Intestine
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Most of the enzymatic hydrolysis that of the
macromolecules from food happens in the
Small Intestine.
In humans, it is over 20 feet long.
The first 10 inches is the Duodenum, where
Chyme mixes with digestive fluids that are
secreted from the pancreas liver and
gallbladder and even from cells in the small
intestinal wall.
Pancreas,Liver and
Gallbladder
• The Pancreas produces an Alkaline solution,
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which is rich in bicarbonate, and many other
enzymes.
This neutralizes the Chymes acidity
The liver produces Bile (contains bile salts
that aid in absorption and digestion of lipids),
which is vital for digesting fats and other
lipids.
The epithelial tissue that lines the duodenum
secrets many digestive enzymes.
Large Intestine
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The last organ in the Digestive Tract is the
Large Intestine
it is made up of the colon, cecum and rectum
Large Intestine
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The cecum is pouch important for fermenting
ingested materials.
o more important in animals that eat alot of
plants.
The Colon leads to the rectum and the anus
The Appendix is removable due to its very small
role in immunity.
colon is mainly meant to recover water that
entered the tract as a solvent of digestive
juices.
Mammalian adaptation
and advantages
• The length of the digestive tract directly
correlates with the diet of the species.
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for example, omnivores and herbivores have longer
tracts because vegetation is harder to digest do to
cell walls and cellulose.
Animals do not contain enzymes to digest
cellulose, so bacteria is present in the
digestive system to carry out that function.
o The microorganisms contain the necessary enzymes
to digest the cellulose into simple sugars and other
consumeable materials.
Mammalian adaptation
and advantages
• Out of all of the herbivorous diets, the
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ruminants have the most elaborate
adaptations.
The ruminant digestive tract has four main
chambers.
The diet that ruminants absorb their nutrients
ends up being much richer than the grass
that it eats.
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Ruminants actually get most of their nutrients by
digesting the mutualistic microorganisms, this is
Why is it Important?
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Digestion is very important to breaking down
the products of food into usable forms, such
as energy and cellular components.
Also the food needs to be broken down into
a reasonable size for consumption without
rupturing organs.
also upon breaking down food it makes thing
more easily digested by increasing surface
area thus decreasing time needed to digest,
making it much more efficient.
Interdependence with
other systems
• One of the main interdependencies is how in
order for a bolus of food to travel through the
esophagus, contractions and relaxations
must occur.
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smooth muscle is responsible for this, and the
muscular system is responsible for this.
Another very important interdependence is
with the endocrine system because it is
responsible for the glands that secrete fluids
and enzymes vital to digestion.
Interdependence
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The circulatory system is very dependant on
the digestive system because it delivers
nutrients to the blood stream.
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By digesting food and getting the nutrients sent to
the blood stream, it allows the nutrients to be
distributed throughout the body to the desired
locations.
Digestive Diseases in
Humans
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One major digestive disease that affects
humans is known as Celiac's Disease.
This disease can cause damage to the small
intestine which prevents it from absorption of
nutrients.
The exact cause of celiac disease is
unknown. The lining of human is full of villi
which help absorb nutrients. When people
with celiac disease eat foods or use products
that contain gluten, their immune system
Celiac's Disease
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Symptoms include: lactose intolerance,
abdominal pain, decreased appetite,
diarrhea, and unexplained weight loss.
Unfortunately, Celiac's Disease cannot be
cured. However, symptoms can be avoided
and the lining of the small and large intestine
can be healed if that person remains on a
lifelong gluten-free diet.
Crohn's Disease
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Like Celiac's Disease, the cause of Crohn's
Disease is unknown. It is an autoimmune
disorder in which the body's immune system
mistakenly attacks the body's healthy body
tissue.
Symptoms include: crampy abdominal pain,
fever, fatigue, and pain with passing stool.
Though there are no cures for this disease, it
can be managed with proper diets and low
levels of stress.