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Dogfish Shark Dissection
Introduction
During this activity you will observeand dissecta shark to developa better understandingof vertebrate
anatomy'The dogfishsharkis an excellentmodel organismfor comparativevertebrateanatomydue to
its sizeand availability.Studyingdogfishanatomyalsohelpsprovide someinsighrinro verrebrate
evoludon and classification.As you proceedthrough this investigation,ysu will be askedto consider
how the form of a particularstructurefits its function. Correlatingstructureand function is an
underlyingthemein all anatomicalstudies.
Background
Squalus
a.canthias
is one of the most common typesof migratorysharks,the spinydogfish.Dogfishtravel
in largeschools,often composedo{ individualsof the samesizeand sex.Dogfishmay live up to 30 years.
They reachsexualmaturity at about 6-12 years.Dogfishear a variety of small fish and marine animals
such assquid,shrimp,crabs,and octopus.They are eatenby largerfish (especiallyother sharks)and by
marine mammalssuch assealsand killer whales.While the name "spinydogfish"seemsominous,rhis
sharkposeslittle threat to humans.A poisonousspinelocatedon the dorsalfin is usedfor protection
againstpredators'The dogfishsl-rarkis often seenasa nuisanceto fishermanas theseanimalsshred
through fishingnets to reach tl-reirfood. Another interestingfeatureof tl-iedogfishis its lengthy
gestationpericld,up to 2 yearsl
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Pre,Lab ObservationSheet
Part 1. Directional Termsand Body Planes
Review the following directional terms and body planes. Write a definition for each term. Then, label
the directionaltermsand planeson the dogfishillustration.Items markedwith an asrerisk(x) are not in
the illustration.
Direction
Definition
Lateral-
Medial -
Proximalx-
Distal* -
Dorsal-
Ventral-
Anterior (cranial)-
Posterior(caudal)-
S"n^.fi.i"l*
-
DeepxPlane
Definition
Sagittalplanex-
Midsagittalplane*
Tiansverseplane-
Frontal plane-
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DogfishDissection
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Pre,Lab Observation Sheet (cont.)
Orientation of Bodv Planes and Directions
plane
plane
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DogfishDissection
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Pre'Lab Observation Sheet (cont.)
Paft 2. Characteristicsof the Dogftsh Shark
1. What have you learned about the dogfishshark in terms of physical characteristics,range, habitat,
behavior,reproduction,and food habits.
2. Why is the dogfisha good choicefor study and dissectionl
3' What are three questionsyou have concerningthe dog{ishshark that can be answeredonly
through dissection?
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DogfishDissection
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Procedure
This dissectionprocedureis divided into severalparts,eachpart addressinga di{Ierentbody system.
Beforeyou begin this dissection,read the entire procedurecarefully.As you follow the step-bystep
instructions,any observationsand answersshouldbe recordedon the DogflshDisectionObservation
Sheetprovidedby your instructor.Use the diagramsto reconcilewhat you have learnedfrom the
procedure.And remember-form fits function.
Part I. External Anatomy
1. The spinydogfishsharkis an agileswimmerwith a long, streamlinedbodir k possesses
a caudal fin,
two singledorsal fins, one pair of pelvic fins, and one pair of pectoral fins. Referto the figure
below to locateeach type of fin on your specimen.Payparticularattention to the largepoisonsecretingspinethat precedeseach dorsalfin and the asymmetricalshapeof the caudalfin. Basedon
the shapeand locatior-rof each {in, what type of funcrion, or movement,do you think it might
provide the sharkl Recordyour ideason the ObservationSheet.
1 . Mouth
4 . Pelvic fin
7. Posteriordorsalfin
7. Gill siits
5. Lateral line
8, Anterior dorsalfir-r
3. Pectoralfin
6. Caudal fin
2. The skin is coveredb)'tiny placoid scales,or dermal denticles,
with sharpspinesthat project posteriorly.Ycrucan run your
hand over the shark'sbody from tail to head to feel this
rough texture. Run your hand in the oppositedirection and
it feelssmooth.Amazingiy,thesescalesare considered
modificationsof teeth and consistof enameland dentin.
What benefit might the configurationof rhesescaleshave
to a shark'sswimmingabihtyt Recordyour answeron the
ObservationSheet.
Placoidscale
4x magnification
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3 . Locatethe narrow horizontalstripealongeachsideof the body of your shark.This interesting
characteristiccommon to all fish is calledthe lateral line systenr..
Using your hand lens,observethe
smallporesfound along this line. Tl-reyare openingsthat lead to sensitivenerve receptorsbelow the
skin. What purposemight this lateral line systemhave to a fish, especiallyin rnurkywatersl Record
your thoughtson the ObservationSheet.
4
Examinethe head of your specimen.The pointed snout is called the rostrum. Orr the undersideof
the rostrum,the nares,or nostrils,allow water in to moistenthe olfactorysensorycellsand permit
the sl-rarkto detect odorsin the environment.The eyesare very similar to human eyes,rvith an iris,
pupil, cornea,and conjunctiva.just beirind the eyes,locate two tiny pores.Theseopeningslead
deepvvitirinthe braincaseto the inner ear,the organof equilibrium.Horv doesthe taperedrostrum
benefit the shark?Recordyour ideason the ObservationSheet.
5, Next locate tl-relargeopeningscalledthe spiracles,which serveaspassageways
for water into the
mouth. This rnakesit possiblefor rvaterto be bror,rghtin to tire gills for respirationwl-ienthe mouth
is closed.How rvouldthis benefit a bottom-dwellir"rg
sharkor rayJRecordvour ideason the
ObservationSheet.
6. Determine the sexof your specitnen.Use the diagramsbelorvto comparenale and femalesharks.
The nralespecimenhas a noticeablefinger-likestructurecalled a clasperon tl'remedial sideof each
peivic fin. During copulation,the clasperis insertedinto the femaie{or transferof sperm.Record
the sexof vour soecimenon the ObservationSheet.
Part II. Internal
Anatomy
7. Place the clogfishon the dissectir-rgtray rvith the
ventral side facing up. Using a scalpel, make an
incision just anterior to the pelr.ic fins. Because the
skin is tough, you lna)'need to use scissorsto cut
thrc''ugh the bt.{y rvall from the pelr'ic fins anteriorly
to rhe riohr nec.roralfin. Make an incision at t1-iebase
ot ' t hc l e ft p e c tu ra lfi n rrn dc u t c a l eful l y through the
body wallback to the pelvic girdle. Then, make a
transverse incision across the pelvic girdle (frorn the
rigl'rt pectoral fin to the left pectoral fin). Contir-rue
tl-reincision L-'osteriorlyto the peh,ic fins. Tl-ris
incision should resemble a triar-igle.Remove the
rrentral body rvall. You har.e now expcisedthe coelon,
the large central body cavity found in all ieriebrates.
In the shark, it is divided into trvo parts: the large
posterior portion called the pleuroperitoneal cavity,
and the small anterior portion called the pericardial
cavity, which contains the heart. How rvoul.l an airbreathingvertebrate (such as a human) be ditferent
from the.1ogfish in terms of its body cavitiesJ Refer tcr
the following diagram, if needed, irnd recorcl your ideas
on the Observation Sheet.
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Esophagus
/4'
. ::rt;
Heart
Smail
intestine
Liver
Liver
Stomacl-r
Laf
{L
lntestlne
q^t-^-
Esophagus
Stomach
Small
intestine
:1.:
rl:,
,lril,.
;Hi
ig,liil
8. The most conspicuous organ in the pleuroperitoneal cavity is the liver. Note the eh 'ngated right
and left lobes and the median lobe. In addition to producing bile and detoxifyir-rgwastes, the liver
also stores energy in large amounts of oil, wl-rich can provide limited buoyancy in the absence of a
swim bladder. How does tl-ie oil pror.'idethis abilityl Record yolrr answer on the Observation Sheet.
The DIGESTIVE SYSTEM is responsible for chemically and mechanically breaking dorvn fuod intcr
smaller compounds that can be released into the bloodstream and then transported to body cells. Let's
investigate the specializedorgans of this system.
9; Using the diagrams provided, locate the najor orgarls of the digestive system, including the
esophagus, stomach, small intestine, and colon. You rviil have to move the long liver lobes gently
to tl-reside to see the esophagusand stomach. As you locate and observe these organs, provide a
detailed description (relative size,shape,color) of each on your Observation Sheet.
10. Examine the esophagusand J-shaped stomach more closell'. Because it is sometimes difficult to
distinguishthesetwo organsexternally,observe
their internal structure.Make an incision
and
tl-rroughthe ventral rvali of the esophagus
stomach.Open both organs,
extend down to t1-re
noting the stomachcontents,if an1,,on yout
observationsheet.\bu tnay need to washout
conrer'Itsto \/iew the lining. Tl're lining of the
is coveredu'ith small,finger-iike
esophagus
projectionscalledpapillae,rvhile tire stomach
lining has deepfolds calledrugae. Basedon your
obsenations,which organis more suitedfor
mechanicaldigestionof food?Explainyour icleas
on the Obsen ation Sheet.
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11. The contentsof the stomachemptyinto the U-shapedduodenum,the {irst of threesectionsof the
small intestine. At this point, digestivelluids are secretedinto the small intestine from two important
accessory
organs,the gallbladderand the pancreas.Locatethe gallbladderalongthe right edgeof
middle lobe of the liver. It is responsiblefor concentratingand storingbile that is producedby the liver.
Bile providesfor the emulsificationof fats.The lightly coloredpancreascan be founclat the curveof
pancreaticjuice, a cocktailof digestive
the duodenum.This two-lobedglandularorganreleases
chemicals,into the duodenum.From the duodenum,foodstufftravels to the noticeably largervah'ular
intestine,whoseouter surfaceis markedby rings.Cut open this structureby makinga shallowincision
alongone side.Youwill seesomethingunique.In sharks,the spiral valve servesto increasesurface
areain a very short intestine.How is this increasein surfaceareaaccomplished
in highervertebrates,
Recordyour answelon the ObservationSheet.
suchasmarnmals?
12. The colon is a narrowedcontinuation of the valvular intestine.It terminatesat the anus, which
opensinto the cloaca.Leadinginto the colon, a slender,finger-likestructurecalled the rectal gland
excretessalt as a meansof regulatingexcessiveconcentrationsin tire blood. Why ra,ssli a shark
needto regulateits saltconcentrations?
Recordyour ideason your ObservationSheet.
The RESPIRATORY SYSTEM functionsin gasexchange,in which outgoingcarbondioxide u,asteis
replacedwith freshoxygento the bloodstream.The CIRCULATORY SYSTEM is responsiblefor the
gases,
transportbf respir:rtory
nutrients,hormones,def'ense
celis,and wastesthroughoutthe bodl'.Dissection
of tl-ieprimitivesharkprovidesan excellentopportunityto conpare to moreadvancedrrertebrates.
13. In fish, respirationoccursby the diffusionof oxygenand carbon dioxiclebetweenthe water and
specialized
structutescalledgills. Tb exanine thesestructllres,insert the scissorsinto the right
cornerof 1,surshark'smouth. Cut posteriorlythrough the jaws and acrossthe externalgill slitsas far
asthe pectoralgirdle.Finally,cut acrc)ss
the ventral musclesto open this flap alongyour dissection
tray and securervith pins.Ycruharreexposedthe pharynx, the muscularchamberthzrtextendsfrom
Along the lateral walls,locate the five pairsof internal gill slits.
the t rai cavity to the esophagus.
They lead to tl"regill pouches,u'hich ir-rturn ieaclto the external gill slits. The gi1lslits are protected
b1's[rsslaltinger-likestructurescalledgill rakers that act as strainersto block food particies.Norv
examinethe cut surfacesof the gilis.Thesehighly fol.led filamentousgill lamellae are the primary "
respirattrrl'por-titrrof the gilis.Using your haud lens,carefullyobservetheselamellaeto notice tirat
eachis coveredby tiny, closelypackedsecondarylamellae.Hor.r'is tl'restructureof thesegills suited
to tl-reirfunction in respiratic'rn?
Recordyour ans\veron the ObservationSheet.
Pharlr-rx
External
gill slit
trlil
lamellae
Spiracle
,
raKers
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14. Now examinethe pericardialcavity anclheart. The dogfishI'rearthas four chambersarrangedir-ra
tube-likeconfiguration:sinus venosus,atrium, ventricle, and the conus arteriosus.Using the
diagramsprovided,locate thesefour chambersin your specimenand trace the path of deoxygenated
blood through the l-reartbeginningwith the sinusarteriosus.Unlike the heart of mammalsand birds,
the heart of the shark transportsonly deoxygenatedblood. \Vl-reredo you think rhe blood is
oxygenatedin the sharkl Recordyour thoughtson rhe ObservationSheet.
Conus
arteriosus
:&',,,,,
ff
, ..i*!!!S
Ventricle
The UROGEI{ITAL
SYSTEM ir-rch-rdes
both reproductive and excretory organs and structures. These
systemsare often stlldiecl together because they shiire common ducts. The main purpose of the excretor,v
organs (kidneys) is to filter nitrogenous wastes from the blood, producing urine. Ti're reproductive
organs. of course, lre responsible fcrr the production of the egg and speln-iand the necessarymeans for
the union of these tu,o special cells.
15. Returnir-rgto the pleuroperitoneal cavit)-,remove the liver at its anterior end. If you have not
removed it alreadl',relnove the digestive tract from the anterior end of the esophagusto tl're posterior
end of the colon. This u'iil reveal the slender paired kidneys in your specimen iocated along the
clorsalwall lateral to the midline. While the kidneys are the primary organs of excretion,
will
-vou
lcern that thel'also have a reproductive role in the male shark. Considering the sex of your specinen,
rr'hat specific structures do you expect to observe?Record your ideas on the Observation Sheet.
If 1*ourspecimenis male, contirTuewith ste116. If ,-our specimenis female, skipto srep'18.You willbe expected
to be familiar witl't structtLres
of eachsc.x,so it is impnrtant to work witl't another grottp that."hasa sharkof the
opposrce
sex.
16. Locate the paired testes acljacentto the cranial end of the kidr-reys.Minute ducules carry slrerm
prc'duced in the testesto the anterior portion of the kidney called the epididpnis. The sperlr then
travel tl'rrough the ductus deferens, ilhicl'r widens into t1-reseminal vesicle. ]n an immature specimen
this tube will appear straight in comparison to the coiled tube of a mature male. The sperm-cunraining
fluid is received by the paired sperm sacs (located just dorsal to the cloaca) and then passesthrough
the ckraca to exit the body. (Ttre cloaca is also the exit for rectal rvasteand urine.) Study the diagrams
belou' that c('mpare the shark anatoilly to that of a l-righervertelrrate. Explain the primitive nature of
the shark's urogenital s)rstem.Record your ideas on the Obsen ation Sheet.
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Spermsac
17. How is sperm transferred frorn the male to female during copuladon? The previously identified
claspers (located on the medial aspect of the pelvic fins) each have a dorsal groove that carries the
fluid from the cloaca to tl-ie female. Also associatedwith the clasper is a thin-walled siphon that is
connected to the dorsal groove just under the skin. You can make a transverse cut into the ventral
surface of a pelvic fin to locate this structure. The siphons secrete a ir-ibricating fluid for the claspers.
On your Observation Sheet, trace the path of sperm frctm its production in the testes to its release
into the female.
18. In the female, loczite the large, paired ovaries adjacent to the anterior end of the kidneys. If vour
specinen is immature, these egg-producing organs r.r'illappear quite small and smooth. Use the
di:igram below to locate the paired oviducts ancl uterus in your specimen. The eggs are released from
the ovary into the oviducts through a smallpore called the ostium. (lt is difficulr to see in mosr
specimens.) The egg is fertilized here, then passesthrough tire shell gland, rvhich secreres a rhin
metnhrane around the fertilized egg.From there, the egg continues down the oviduct to the uterus,
rvhere gestation occurs. As the ),'ounggroq they are attached to the nourishing yolk sac by means of a
stalk. Tl-rismethod of development in tl"redogfish shark is known as o+touiuiparous.Chickens are
ouiparous, and humans are uiuiparous. Explain the differences on your Observation Sheet.
Oviducts
Devekrping
young
Yolk sac
Ovar1,
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DogfishDissection
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Dogfish Dissection Observation Sheet
fins
I
Basedon the shapeand location, what type of function
or movement does each fin provide the dogfish sharkl
caudal fin:
dorsal{ins:
pelvic fins:
pectoral fins
2
3
placoidscales
\What benefit might the configuration of the placoid scaleshave to a shark'sswimming ability?
lateralline system
What purposemight the lateral line systemhave to a fish, especiallyin murky warers?
rostrum
4
How does the tapered rostrum benefit the shark?
spiracles
)
How would being able to bring water in to the gills when the mouth is closed
benefit a bottom.dwelling shark or ray?
gender (male or female)
6
02 00 8
\il/hat genderis your specimen? E Mul"
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body cavity
7
Compare the body cavity of the dogfish shark to a human. How are they different?
liveroil
8
How does the oil from the liver provide limited buoyancy in the absenceof a swim bladder?
maior organs of the digestive tract
W'ritea detaileddescription(relativesize,shape,color) of eachof the followingorgans:
9
esophagus:
stomach:
small intestine:
colon:
esophagusand stomachlinings
10
1l
t2
02 00 8
What are the contents of the stomach (if anyd-ring)/
Cornpare the lining of the esopl'ragus
and the lining of the stomach.
Wl-rich organ is rnore suited for mechanical digestion of food?
spiral valve
Comparethe smaliintestineof the dogfishsharkand the smallintestineof a mammal.
How is the insidesurfaceareamaximizedin eachanimal?
rectal gland
!7hy would a shark need to regulateits internalsaltconcentration?
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gills
How is the structure of the gills suited to their function in respiration?
oxygenation
I4
15
Unlike the heart of mammals and birds, the heart of the shark transporrs only
deoxygenatedblood. lil/here do you think the blood is oxygenaredin the shark?
reproductive structures
Considering the sex of your specimen,what specificstructuresdo you expect to observe?
male urogenitalsystem
t6
I7
18
Compare the shark anatomy to that of a higher vertebrate.
Explain the primitive nature of the male shark'surogenitai system.
path of sperm
Dralva diagramor simplesketchof the path of spermfrom productionin the testes
to its releaseinto the female.
ovoviviparous,oviparous,viviparous
Explain the differencesof each method of offspring development listed below:
o\/ovlvlparous:
ovlparous:
vlvlparous:
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DogfishDissection
Name
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Questions
1. Discussthe hydrodynamicsof the dogfish shark.
2.
'!7hat
are the two classesof fishl In which classis the sharkl
3. Draw the digestivetract of the sharkfrom mouth to anus.Label the structures.
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4. What is the advantageof the spiral valve in the shark'sintestine?How doesthis differ from the
extremelylong intestine of the humanJ
5. How do the gills function in respiration?
6. What advantages does a caftilaginous skeleton have over a bony skeleton?
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Glossary
Ampullae. Senseorgansthat form a network of jelly-filledcanals.
Anterior chamber.The fluid-filled spaceinside the eyebetweenthe iris and the cornea.
Anus. The openingthrough which solid wasteis eliminatedfrom the body.
Atrium. Either of the two upper chambersof the heart. The left atrium receivesoxygenatedblood into
the heart via the pulmonaryveins,and tl-reright atrium receivesblood from theluperior and inferior
vena cava,
Bile. A greenish'yellowfluid secretedfrom the liver that is releasedinro rhe duodenumof the small
intestine.Bile aidsin the processof digestion.
Caudal fin. The tail fin, or main propeiling fin of a fish.
Ciliary body. Thin, vascular,rniddlelayerof the eye,locatedbetu,eenthe scleraand the rerlna.
Claspers.Pairedmale copulatoryorganslocatedon the rear baseof the pelvic fi1s.
Cloaca. Tl-reposterioropeningthat servesas the openingfor the intestinal,urinar1,,and genital tracts.
coelom. A secondaryb.dy cavity thar surroundsthe digestivesystem.
Colon. Largeintestine;functionsin formation of fecesfrom undigestedremainsof food through the
reabsorptionof water and action of intestinalbacteria.
Conjunctiva. The thin, transparenttissuethat coversthe outer surfaceof the eye.
Conus arteriosus.Tl-recavity of the heart which begir-rs
at the suprayentricularcresta1d e.ds in the
pulmt'rrary
rrunk.
Cornea. Tiansparentcoveringthat allowslight to enter the eye;in a preservedspecimen,the eyeis
cloudy.
Dermal denticles (placoid scales).Tiny scaleswith sharpspinesrhat cover the skin of tl-reshark.
Dorsal fin. Fin locatedon rhe back of a fish.
Ductus deferens.Tlrbethat carriesspermfrom the testis (via epididymis)to the urethra.
.-..
Duodenum. The {irst part of tl'resrnallintestine,connectingthe stomachto the jejunum. This is the
location of further breakdownof food a{terbreakdownin the stomach
Epididymis. Connectsthe testisto the vas deferens.Also servesas a srorageareafor spermoroducedbv
the testisbut not yet ejaculated.
Esophagus.Musculartube through which food passesfrom the pharl,nx to the stomach.
Gallbladden Small sacattachedto the liver; storesbile producedby the liver.
Gill arches.The bony or cartilaginoussupportto which gill filamentsand gill rakersare atrached.
Gill lamellae.An arrangementof thin platesthat increasesurfaceareafor gasexchange.
Gill pouches.Area berweenthe internal and exrernalgill slits.
Gill rakers. Bony or cartilaginousprojectionsthat poinr forward and inwarclfrom tl'regill arches.
Gill slits. Gills with individual openingsrather than a' outer cover.
Gill. A highly vascularrespiratoryorgan through which oxygenis obtainedfrom warer.
Iris. Diaphragmthat regulatesthe sizeof the pupil.
Kidneys. Rean'shapedexcretoryorgansrespor-rsible
for filtering excesswater and wasteprodlictsfrom
the blood,
Lateral line. Senseorgan usedto detect nlovenent and vibration in the surroundinswater.
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Lens. Biconvex,transparentstructurethat focusesthe light coming in througl-rthe corneaand pupil of
the eye.
Liven Accessorydigestiveorganwith many functions,including fat digestionand storage,bile
production,glucosemetabolism,and detoxification;the largestvisceralorgan.
Nares. Nosrils. Incurrent openingsfor the respiratorysystem.
Ostium. Small poresin which eggsare fertilizedand passfrom the ovariesto the oviduct.
Ovaries. Femalegonads.Releaseeggsinto the fallopiantubes.
for eggcellsfrom the ovariesto the uterus.
Oviducts. Fallopiantubes;passageway
Pancreas.Accessoryglandwith both an endocrineportion, producinginsulin and glucagon,and an
exocrineportion, producingdigestiveenzymes.
Papillae.Srnall,finger-likeprojectionscoveringthe esophagus.
Pectoral fins. Pairedfins iocatedon each side,usuallyjust behind the operculum.
Pectoral girdle. Portion of the appendicularskeletonsupportingthe forelimbs.
Pelvic fins. The most posteriorpairedfins of a fish, usedfor stability.
Pelvic girdle. Portionof the appendicularskeletonsupportingthe hind limbs.
peritoneumthat enclosesthe heart; surroundedby pericardialfluid that
Pericardium. Sacof specialized
cushionsand protectsthe heart.
Peritoneum. Thin membranethat lines the abdominal cavity.
Pharynx. The muscularchamberthat extendsfrom the oral cavity to the esophagus.
Placoid scales(dermal denticles). Tiny scaieswith sharpspinesthat cover the skin of the shark.
Pleuroperitonealcavity. Largerposteriorportion of the coelom.
Pupil. The openingthrough which light entersthe eye.
Rectal gland. Salt-secretingorgan that regulatessalt concentrationsin the shark'sblood.
Retina. Light-sensitiveportion of the eye,composedof receptorcellscalledconesand rods.
Rostrum. Structureof the anterior,ventral regionof the cerebrum,extendingventrallyfrom dre genu rd
the septumpellucidum.
foldsin the wall of the stomachthat allow for expansion.
Rugae.Severallongitudir-ral
Sclera.Outer coveringof the eyeball;a tough, opaquesheetof connectivetissuethat protectsthe inner
structuresof tl-reeyeballand helpsmaintain rigidity.
Seminal vesicle.Gland locateddorsalto the urinary bladderin males.This gland releasesfluid tl-iat
combineswith spermto make semen.
Shell gland. Glarld wllich secretesa thin membranearound the fertilized egg.
Sinus venosus.Largechanber ofthe heart that receivesdeoxygenatedblood from the body and has a
valve that opensto the atrium.
Siphon. Thin-walled sacthat secreteslubricatingfluid for the claspers.
Sperm sacs.Sperm-collectingsacslocatedjust abovethe cloaca.
Spiracle.Small openingfound behind each eye;usedto pump water through the gilis while the animal is
at rest.
Spiral valve. The lower portion of tl-reintestine.
organto the circulatorysystemthat produceslymphocytesand destroysold and
Spleen.An accessory
defectivered blood cells.
Stomach. Organ responsiblefor tl-rebreakdownof food into absorbableparticles.Locatedin the
digestivetract betweenthe esophagusarid the small intestine.
Testes.Organsresponsiblefor production of spermin males.
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Urinary papilla. The external projection of the male urinary bladder.
Urogenital papilla. A small conical tube located just aheadof the anal fin.
Urogenital sinus, Cavity that surroundsboth the urethral and vaginal openings.
IJterus. Femalereproductiveorganthat holds developingfetuses.
Valvular intestine. The second,and much larger portion of the small intestine.
Ventricle. One of two lower chambersof the heart; the left ventricle forcesblood into rhe aorra, and the
right ventricle forcesblood into the pulmonary arteries.
Vitreous chamber. A cavity of the eye posterior to the crystalline lens and anterior to the retina.
O20 08 Car oiina Biologic al
Supply C o m p a n y
9-18