1. The Mouth To study the mouth, scissors are used to cut the corners of the mouth at the angle between the upper and lower jaws on each side of the head. Tongue Maxilary Teeth Nasal Nare Glotis Vomerine Teeth Eustacian Tubes Gullet Opening Nasal Nare Typana External Frog

2. Just ventral to the gullet is a vertical slit called the glottis. The glottis opens into the trachea, or windpipe, which leads to the lungs. gullet glottis The Mouth

3. The frog is laid ventral side up. Next, beginning between the hind legs, the skin is cut along the midline to the middle of the lower jaw. The skin is loosely attached to the underlying muscle. This makes it easy to explore the spaces beneath it with a dissecting needle. The small, yellowish knots you may observe under the skin are lymph nodes. Lymph nodes are located beneath the skin in this area. The skin is cut laterally at each end of the incision and then spread open. Lymph node. Science Guys Science Guys Frog Dissection MainFrog Dissection Main Internal FrogInternal Frog BackBack NextNext Getting Under the Skin

4. Cutting Through the Muscles The body cavity is opened by cutting through the abdominal muscles and the muscles and bones of the chest and throat regions. The same line is followed as with the skin, but at a point just in front of the hind legs. The sternum, or breastbone, was freed by cutting the bones joining it to the shoulders. sternum

5. The flaps of abdominal muscle are pinned back. As you identify the organs in the body cavity, label Figure 2 in your Record Book. heart liver small intestine pericardium fat bodies stomach The flaps of abdominal muscle are pinned back. As you identify the organs in the body cavity. Here Is Your First Look Inside

6. Oviducts and Cloaca In a female frog, the abdomen may be filled with small, black eggs that would be removed. The oviducts can then be located as two twisted tubes that carry the eggs to an excretory organ, the cloaca, from which they are passed from the body. spleen egg mass oviducts spleen egg mass oviducts

7. The Heart The heart lies along the midline, just back of the forelegs. Observe the large blood vessels leading two and from the heart. heart Abdominal Vein The heart is surrounded by a thin tissue, the pericardium. pericardium

8. The pericardium is opened to reveal the lower part of the heart, the ventricle, and the upper part, which is composed of two atria. atria ventricle What is the difference between the thickness of the walls in the atria and the ventricle? What is the reason for this difference? The walls of the atria can be pushed in easily. The walls of the ventricle are sturdier. The Heart

9. Truncous Arteriosus Conous Arteriosus Ventrical Left Atrium Right Atrium The Heart

10. The Liver and Gall Bladder Posterior to the heart is a large, reddish- brown organ, the liver. It is divided into part called lobes. How many lobes are there? Liver Underneath and between the middle and right lobes of the liver, find a small greenish sac, the gall bladder. gall bladder The gall bladder stores a liquid called bile, which is produced by the liver. What is the function of bile?

11. The Small Intestine and Stomach Find the small intestine, a coiled mass of tissue. small intestine cloaca The small intestine can be traced anteriorly to the stomach, a white, curved, elongated structure. Small intestine Pyloric Valve Constriction between the small intestine and the stomach. pancreas stomach Of what significance is the constriction at the point where the stomach joins the intestine?

12. The stomach is connected to the mouth by the esophagus. This structure can be seen by lifting the left lobe of the liver. esophagus The Small Intestine and Stomach

13. Note the mesentery, the thin, delicate membrane that supports the intestines and other organs of the digestive tract. mesentery Locate the pancreas, a narrow, whitish band of tissue between the stomach and the first loop of intestines. stomach spleen pancreas mesentery The function of the pancreas is to secrete digestive enzymes. The Mesentery and Pancreas

14. The Spleen and Fat Bodies Find the yellowish fat bodies. heart fat bodies liver stomach The spleen is a reddish-brown body which stores red blood cells. spleen

15. The Kidneys Lying along the dorsal body wall are two oblong, reddish bodies, the kidneys. The other organs must be pushed aside to see them. kidney

16. The Lungs Covered somewhat by the other organs, the lungs appear as saclike organs on either side of the thorax, or chest cavity. lungs lungs stomach cloaca

17. Review stomach small intestines cloaca mesentery egg mass oviducts spleen pancreas atria ventricle Liver Abdominal Vein