Here is the link with photos for the Frog Dissection

http://us.geocities.com/sciencejanetc/7th_8th_grade/animal_kingdom/frog_dissection.html

Rat Dissection (4th and 6th Period)

Rat Dissection

PowerPoint Presentation, Rats

Back to Lab Schedule

Cool Virtual Dissections Link

Frog Dissection

Frog Dissection

Parts of this lab by E.S. Belasic

Pre-Lab Research:

• Study these websites before you start your dissection. Froguts and Net Frog
• All About Frogs gives all sorts of information on frogs

Objectives:

• to observe the external and internal anatomy of a frog.
• to determine the sex of a frog using internal anatomy.
• to view the body systems : epidermal, muscular, digestive, respiratory, circulatory, urogenital, and skeletal

Procedure:

External Anatomy:

• Sketch the dorsal side of your frog in Fig 1.
• Label the 4 directions : dorsal, ventral, anterior, posterior
• Identify the eyes, which have a non-moveable upper and lower lid, but can be covered with a nictitating membrane which serves to moisten the eye.
• Locate the tympanum behind each eye and label.
• Examine the external nares (nostrils). Insert a probe into the external nares and note that it protrudes from one of the paired small openings, the internal nares inside the mouth cavity.
• Label the tympanic membrane, eye, mouth, and external nares.
• Sketch the ventral side of your frog in Fig 2. Label the 4 directions: dorsal, ventral, anterior, and posterior.
• Which feet are webbed?__________________________
• The sex of a frog may be determined externally by examining the thumb pags on the front feet. The thumb pads of males are enlarged at the base as in the drawing. Determine the sex of your frog. _____________

• Open your frog's mouth very wide, cutting the angles of the jaw if necessary. Are there teeth on the lower jaw, upper jaw or both? _________________
• Identify the tongue attached to the lower jaw's anterior end.
• Find the Eustachian tube opening into the angle of the jaws. These tubes lead to the ears. Eustachian tubes equalize air pressure in the ears.
• Examine the maxillary teeth located along the rim of the upper jaw. Another set of teeth, the vomerine teeth, is present just behind the mid portion of the upper jaw.
• Locate the glottis, a slit through which air passes in and out of the trachea, the short tube from the glottis to the lungs.
• Identify the esophagus. which lies dorsal and posterior to the glottis and leads to the stomach.


• Pin your frog to the pan by placing pins through the 4 limbs


Internal Anatomy: Be Careful : DO NOT CUT TOO DEEPLY!

1. Take your scalpel or scissors and carefully make an incision from the throat to where the legs meet.
2. Make your second incision across the shoulders and across the lower abdomen.
3. Peel back the skin flaps
4. You may remove all the skin on your frog to examine the muscles.
5. Carefully cut through the muscles of the abdomen the same way you made the skin incisions and pin the muscles back.
6. Unlike humans, frogs do not store fat next to the skin. Frogs store fat for winter in fat bodies inside the body cavity. If your frog was collected late in the year, the body cavity may be full of these orange fat bodies. Does your frog have much stored fat?


7. Find the Liver and heart. This is the first layer of organs. How many lobes does the liver have? __________
8. At this point you may also see masses of eggs if you have a female.
9. Push the 3-lobed liver and heart to the left and expose the esophagus running back from the mouth to the large J-shaped stomach and small intestines.. The gall bladder can be seen on the back side of the liver. This is the second layer.
10. Cut the esophagus as close to the mouth as possible.
11. The stomach consists of a large anterior cardiac portion and smaller posterior pyloric portion which ends at the pyloric sphincter. This circular muscle opens and closes the bottom of the stomach.


The first portion of the small intestine, the duodenum is directly below the pyloric sphincter. Posterior to the duodenum lies the elongated and coiled ileum, which in turn, connects with the large intestine. The large intestine is easily identifiable as a marked expansion of the alimentary canal in the posterior region of the body cavity.

The gall bladder is located on the dorsal surface of the right lobe of the liver. The bile duct carries bile from the liver to the duodenum. The spleen is a roughly spherical dark organ which lies in the intestinal mesentery ventral to the kidneys.


12. Cut the large intestine as close to the anus as possible. Both ends of the canal have now been cut. Carefully remove the alimentary canal in one piece. Measure the length of each organ of the alimentary canal in centimeters and record them below.
• Esophagus
• Stomach
• Small intestines
• Large intestines


13. Find and remove the following : stomach, intestine, (yellowish) pancreas, (clear/green) gall bladder
14. Find and remove the following : heart, right and left lungs
15. Find and remove the following: (reddish) spleen, (dark brown) kidneys
16. Find and remove the following: ovaries or testes
17. When you are done, remove as much tissue as you can until the bones are exposed. Try to find the following: humerus, radioulna, femur, tibiofibula Data: (leave a 1/2 page for each figure and table)

Data:

Figure 1: Dorsal view of frog (d, v, a, p)
Figure 2: Ventral view of frog (d, v, a, p)

Figure 3: Musculature : deltoid, pectoralis, rectus abdominis, gastrocnemius

Analysis: Discuss how the organs of a frog are similar to the organs of a human.
Conclusion: 2-3 sentences on what you learned