Interior of the Dogfish Shark
Reasons to Use the Dissection Video and
Accompanying PowerPoint Presentation
 Reduce the number of specimens used by a class
 Increase the quality of the dissection for the students
 Review opportunity, increasing the learning experience
for the students
 Student unable to dissect due to pregnancy or
hypersensitivity to the preservatives
 Student chooses not to dissect due to ethical/moral
reasons
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Interior of the Dogfish Shark
As an educator
you are responsible for the implementation
Safety
Considerations
of the dissection activity described in the video and
 Age appropriate
activity
for the
children
in your care
PowerPoint.
You must
have
safety
procedures
and rules
 (Material)for
Safety
Data
Sheet (M)SDS
available
for all
accident
established
your
classroom
and make
sure
of the
reference
students
follow the rules to ensure a safe environment.
 Poison control number/phone readily available
South Dakota Public Broadcasting and Dakota State
 Latex free gloves, eye protection and apron/lab coat
University
any way
be responsible or liable for
 Eyewashcannot
station,in
shower
and sink
injury
as a result
of performing
the
described
 any
Sharp
instruments
(cut away
from self and
others)
dissection.
Sharps and specimen(s)
disposal
Complete the
dissection if you feel it is
 Encourage
students
report
accidents
appropriate
and to
safe
for all
your
individual class.
 Basic science laboratory
enforced)
Have funrules
and (strictly
stay safe!
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Interior of the Dogfish Shark
Getting Started
 Use water to rinse the excess preservative from
your specimen
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Interior of the Dogfish Shark
Many times a section of intestine may be prolapsed (shown below).
Do not remove the prolapse; once the body cavity is exposed, it
can be corrected by following the steps shown in the photos below.
Gently pull on the intestine while placing pressure near the cloaca.
Prolapse
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Interior of the Dogfish Shark
Always cut away
from yourself
3
4
2
1
 Shown above - Make an incision on the side of the shark near the
pelvic fin. Place the scissors in the incision and press upward with
lower part of the scissors against the muscle/skin to prevent cutting
too deep; 1. cut toward the pectoral fin; 2. cut toward the opposite
pectoral fin; 3. cut toward the pelvic fin; 4. cut toward the opposite
lateral cut; carefully remove the flap of muscle/skin to expose the
coelom (body cavity) - example next
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Interior of the Dogfish Shark
Structure identification: Your specimen is
unique; many of the structures will not look
exactly like the photos or drawings in your book;
the following slides will identify structures using
multiple views and specimens.
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Interior of the Dogfish Shark
Spleen – Immune (white blood cell
production); filters and stores blood
Rectal gland – removal of salt,
deposits into large intestine
Small intestine – Digestion and nutrient absorption
Liver – The three lobed liver is the largest organ in the abdomen cavity; the liver is
comprised of two large lateral lobes and a smaller medial lobe; the liver has many
functions including detoxifying blood, stores oil for energy and density reduction (lacks
swim bladder), and produces bile for fat digestion
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Interior of the Dogfish Shark
Esophagus – Connects
Liver
pharynx to the stomach
Male or Female?
Stomach
– Food
Cardiac
region
of stomach
It
can
be
difficult
to identify whether
storage and digestion
the following structure is a testis
(male) or ovarySpleen
(female),
especially
Pyloric
region
of stomach
when the shark is immature. Both are
located below the liver, toward the
dorsal and cranial region of the cavity.
Spleen
Bile duct
Small intestine
The organ above is a testis. The easiest
Rectal
way to identify this specimen Intestine
is bygland
identifying whether there are claspers
Bile ductbelow).
on the pelvic fins (shown
Regions of the Stomach – The cardiac region of the stomach has rugae,
Gallbladder – Attached to the middle lobe of the liver; stores bile that was
which are folds that increase surface area for digestive juices and for
producedvolume
in the liver
can have
a greenregion
tint from
the bile); during
increased
for(gallbladder
food storage;
the pyloric
(J-shaped)
has the
fat digestion
the bile isinto
released
via the bile
duct
to the small
intestine
pyloric
value leading
the intestine
that
regulates
food
passage
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Interior of the Dogfish Shark
Things to look for:
Female
or Male
(Internal)
Mature
Female
• Paired gonads in female (ovary); paired gonads in male (testes)
Oviduct
Female
• Generally testes are slender; ovaries plump
Uterus – Enlarged
with pups
Female
Small intestine
Male
Cloaca
Large intestine
(colon)
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Interior of the Dogfish Shark
Mature Female
Internal fertilization
Developing pup
During
Yolk copulation, the clasper of the male is
Dissect the uterus
inserted into the cloaca of the female,
transferring sperm. The eggs released by the
ovaries are fertilized in the oviduct. The
fertilized eggs develop in the uterus of the
female (ovoviviparous). The developing
embryos each have their own egg (yolk); no
connection to the mother. After approximately
2 years the pups are born live via the cloaca.
-no additional parental carePreserved pup with
intact yolk
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Interior of the Dogfish Shark
Mesentery and Digestive System Removed (Male Shown)
Testes
Kidneys – Excrete
waste from the
Prolapse
blood; long, thin, and paired;
contained within the body wall
Kidney
Vas deferens
Vas deferens – Coiled reproductive duct;
transfers sperm; lies anterior to the kidney
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Interior of the Dogfish Shark
Cardiac region of stomach
Spleen
Pyloric
region of stomach
Closeup
View
Rectal
gland
Spleen
Pancreas – Two lobes
Small intestine
Mesentery – Connective tissue;
houses lymphatic tissue and blood
vessels
Small intestine
Large intestine
(colon) - Water
absorption
Pancreas – Located by the start of the small intestine; enzyme
producing structure for digestion; hormone production
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Interior of the Dogfish Shark
Dissect the esophagus and the stomach.
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Interior of the Dogfish Shark
Dissect the Esophagus and the Stomach
Esophagus
Prolapse
Pyloric region of
stomach –
smooth, no folds
Cardiac region of
the stomach Rugae (folds)
increases surface
area and allows
for expansion
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Interior of the Dogfish Shark
Dissect the Small Intestine
Prolapse
Spiral valve of the
small intestine –
increased surface
area for nutrient
absorption without
increased length
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Interior of the Dogfish Shark
Heart – Two
chambered (one
ventricle and one
atrium)
Gills
The next three cuts (above) will expose the heart and gills.
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Interior of the Dogfish Shark
Heart Lifted Up
Gills
Atrium
Gills: Feather-like
structures (increased
surface area); used to
remove oxygen from
water for respiration
Sinus
Venosus
Conus
Arteriosus
Ventricle
Deoxidated blood enters
the sinus venosus from the
body. Blood then enters
the atrium (which has two
lobes), and is then pumped
to the ventricle. The
ventricle pumps the blood
through the conus
arteriosus to the gills
whereGillgas
exchange
Rakers:
Projections
that prevent blood,
occurs. Oxygenated
(strain/filter)
particles,is
with reduced
pressure,
like food, from entering
distributed the
to the
body.
gills.
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Interior of the Dogfish Shark
Additional Resources Available @ Dissection 101
•
Interactive PowerPoints
•
Videos
•
Lesson Plans
•
Handouts
•
Quizzes
•
Additional Dissections
Next: We did not dissect the central nervous system because many
schools do not complete this due to time constraints. You could have
the students dissect the central nervous system to improve their
dissection skills or for extra credit. Extra care and supervision is
advised (always cut away from yourself). Video
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Interior of the Dogfish Shark
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