DISSECTION OF THE FROG

External view:

Observe the external features of the frog before doing any cutting.

Find the tympanic membrane; look closely at the structure of the eyes; find the anus. Next open the mouth. You may have to cut the hinge of the jaws in order to open it wide.

Identify the maxillary teeth, the vomerine teeth, the bulging eye-sockets, the glottis (opening to the trachea), the gullet (opening to esophagus), the eustachian tube openings, and the tongue.

Muscles:

Remove the skin completely from the frog's muscles, taking care not to injure any of the muscles. Using the diagrams provided, locate and be able to identify the following muscles: 

Ventral View:			Dorsal View:


Mylohyoid  		  	Latissimus dorsi


Pectoralis			Longissimus dorsi


Rectus abdominis			Dorsalis scapulae


External oblique			Semimembranosus


Sartorius				Iliofibularis


Adductor magnus			Peroneus


Gracilis major			Gastrocnemius


Gracilis minor			Achilles tendon


Semitendinosus			Vastus externus


Tibialis anticus longus		Vastus internus




INTERNAL DISSECTION OF THE FROG

Open the body cavity by making an incision down the middle of the ventral side of the frog. Be careful not to cut the organs underneath. Around the pectoralis muscles the cutting may become hard because of the bones underneath. Cut up to the chin. Next make a lateral cut (on each side) at the arms and at the waist. Fold the skin back and observe the body cavity.

If your frog is a female she may contain eggs. In order to see anything else you will have to remove these eggs. There may also be some yellow or orange fat bodies inside. Be careful in removing these as some of these are attached to other organs.

Identify the following organs:

Heart - The lighter part is the more muscular ventricle. The atria are smaller and darker.

Liver - the largest organ; divided into 3 lobes

Gallbladder - resembles a green pea; look underneath the liver to find it.

Stomach - large whitish sac under the liver, on the right as you look in.

Small intestine - small (but long) tube attached to stomach

Mesentery - transparent membrane attaching intestines to body wall

Large intestine (Colon) - larger in diameter but shorter than sm. intestine

Spleen - reddish brown spherical body embedded in mesentery; lift stomach and intestines to find it

Kidneys - two reddish organs in the dorsal wall of the body cavity

Ovaries - (females only) large sacs often packed with eggs

Oviducts - (females only) coiled tubes on both sides

Testes - (males only) white to yellow oblong organs attached to kidneys

Cloaca - common meeting point of digestive, excretory, and reproductive systems just inside the anus. (You don't have to actually see it)

Lungs - small dark organs deep in body cavity on each side (near armpits) that resemble raisins

After you have located, identified, and can identify these on a test, you should review the muscles that you learned yesterday. Then place your frog in the plastic bag and clean up your area, wash all utensils, and wash your tray.