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Frogs

The Leopard Frog

Scientific Name: Rana pipiens

What are the frogs preserved in?

•  The frogs we’ll be dissecting are not in formaldehyde, as what used to be the case. •  Why? Is a carcinogen (cancer causing

agent) • Instead, they are preserved in formalin

- 90% water - 9% propane glycol - 1% ether

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Why frogs??

•  First of all, frogs are valuable to man. They eat insects, which keeps the insect population down

•  We dissect frogs because their internal anatomy is much like our own.

Dorsal vs. Ventral Side

Dorsal-coarse, moist, dark

Ventral—light, smooth

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Posterior- back end of frog

Anterior- front end of frog

q  The frog's powerful hind legs are equally effective in jumping or swimming. On land frogs sit with their hind legs folded against the body, poised to jump at the first sign of danger.

q  Most frogs can make leaps many

times their body length.

q The frog’s front legs are used for balance.

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Frogs’ eyes also work equally well in or out of water. Because the eyes bulge out from the head, the frog can stay submerged while literally "keeping an eye out" for predators.

q The frog's thick, moist skin unlike it’s cousin the “toad” whose skin is “dry and warty”.

q  serves two important functions— respiration and protection…

q Glands secrete mucus to keep it from drying up.

q Like humans, frogs breathe by using lungs.

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Some glands secrete foul-tasting or poisonous substances that protect the frog from enemies

Some frogs, such as Hyla versicolor, can change color in

order to blend with the environment.

Count the number of

frogs in the picture?

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Frog External Anatomy

Nictitating membrane image from: http://www.spc.cc.tx.us/biology/jmckinney/Studyimages/frog/frogdissectlist.html

“eardrum”

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Nose and Eyes •  The nostrils of frogs are

called “Nares”. These are both internal and external.

•  The eyes of a frog are protected from the water by a structure known as the “nictitating membrane”. They act as goggles.

Nictitating Membrane

q  “Nictitating Membrane” q Don’t be fooled, frogs have regular eyelids that

can blink. This protects the frog's eyes from dust and dehydration

q The nictitating membrane is transparent and joins the upper and lower eyelid together, which allows the frog to have goggles as it swims under water.

q This membrane keeps the eyelid moist and protects it when it is under water.

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image from: http://www.spc.cc.tx.us/biology/jmckinney/Studyimages/frog/frogdissectlist.html

“eardrum”

Frogs have eardrums

•  Frogs are able to hear thanks to a special structure located just behind the eye called the “Tympanic Membrane”.

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Inner ears??????? The tympanic

membrane on the outside of a frog’s head is also connected to the Eustachian tubes on the inside of the frog’s mouth. This equalize the air pressure in the head of the frog.

NO CLAWS image from: http://www.spc.cc.tx.us/biology/jmckinney/Studyimages/frog/frogdissectlist.html

Aids the Frog in swimming

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What sex is it?

Images from: http://sps.k12.ar.us/massengale/frog_dissection.htm

These are found on males during breeding season

Is this a male or female?

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TONGUE attached at front not back like yours!

Imagse from: http://www.animationlibrary.com http://www.geocities.com/animalbio/biology.htm

TEETH ( Two sets) •  Vomerine Teeth

are located at the top of the mouth that hold prey captive

•  Maxillary Teeth are located around the edge of the mouth that are used to grasp things

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Other important features of the mouth…..

This is an upclose picture of the inside of the frog’s mouth

Connect ears to back of throat

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Frog Internal Anatomy

Females may have black & white eggs

Image from; http://faculty.clintoncc.suny.edu/faculty/Michael.Gregory/files/Bio%20102/Bio%20102%20 Laboratory/frog%20dissection/frog%20dissection_files/frame.htm

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Pericardial membrane around heart Mesentery holds intestines together

image from: http://www.spc.cc.tx.us/biology/jmckinney/Studyimages/frog/frogdissectlist.html

Mesentery holds intestines together

image from: http://www.manheimcentral.org/~tw005690/Frog/frog.htm

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Image from: http://step.sdsc.edu/projects95/Frog.Dissection/index.html

LARGE INTESTINE

Removes water from digestive waste;

concentrates feces

SMALL INTESTINE

DUODENUM Receives trypsin and bile;

finishes digestion

ILEUM Absorbs nutrients

http://www.flushing.k12.mi.us/srhigh/tippettl/biology/frog/largeintestine.html

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Gall Bladder

Pancreas (enlarged)

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SPLEEN

Produces and stores new Red blood cells and processes old worn out ones

LUNGS: GAS EXCHANGE

http://www.flushing.k12.mi.us/srhigh/tippettl/biology/frog/index.html

http://www.stclement.pvt.k12.il.us/studentWeb/science98/GarrittPatM/alveoli.gif

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TESTES MAKE SPERM http://step.sdsc.edu/projects95/Frog.Dissection/index.html

TESTES KIDNEY

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Key Terms to remember:

•  Peritoneum •  Messentary •  Pectoral Girdle

•  Pericardial Sac

•  --Lining of abdominal cavity

•  --tissue that holds organs in place (such as intestines)

•  Bone that protects the heart

•  Sac that encloses and protects the heart