- Inquiry Into Life Laboratory Manual 16th Edition Opening The Frog 1 Place The Frog Ventral Side Up In The Dissecting P 1 (237.55 KiB) Viewed 74 times
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Inquiry into Life Laboratory Manual, 16th Edition Opening the Frog 1. Place the frog ventral side up in the dissecting pan. Lift the skin with forceps, and use scissors to make a large, circular cut to remove the skin from the abdominal region as close to the limbs as possible. Cut only skin, not muscle. 2. Now, remove the muscles by cutting through them in the same circular fashion. At the same time, cut through any bones you encounter. A vein, called the abdominal vein, will be slightly attached to the internal side of the muscles. 157 3. Identify the coelom, or body cavity. Recall that vertebrates are deuterostomes in which the first embry- onic opening becomes the anus and the second opening becomes the mouth. 4. If your frog is female, the abdominal cavity is likely to be filled by a pair of large, transparent ovaries, each containing hundreds of black and white eggs. Gently lift the left ovary with forceps, and find its place of attachment. Cut through the attachment, and remove the ovary in one piece. Respiratory System and Liver 1. Insert a probe into the glottis, and observe its passage into the trachea. Enlarge the glottis by making short cuts above and below it. When the glottis is spread open, you will see a fold on either side; these are the vocal cords used in croaking. 2. Identify the lungs, two small sacs on either side of the midline and partially hidden under the liver (Fig. 31.7). What path does air take through the respiratory tract? List all structures it passes from the external nares to the lungs. 3. Locate the liver, the large, prominent, dark-brown organ in the midventral portion of the trunk (Fig. 31.7). Between the right half and left half of the liver, find the gallbladder. Circulatory System 1. Lift the liver gently. Identify the heart, covered by a membranous covering (the pericardium). With for- ceps, lift the covering, and gently slit it open. The heart consists of a single, thick-walled ventricle and two (right and left) anterior, thin-walled atria. 2. Locate the three large veins that join together beneath the heart to form the sinus venosus. (To lift the heart, you may have to snip the slender strand of tissue that connects the atria to the pericardium.) Blood from the sinus venosus enters the right atrium. The left atrium receives blood from the lungs. 3. Find the conus arteriosus, a single, wide arterial vessel leaving the ventricle and passing ventrally over the right atrium. Follow the conus arteriosus forward to where it divides into three branches on each side. The middle artery on each side is the systemic artery, which fuses behind the heart to become the dorsal aorta. The dorsal aorta transports blood through the body cavity and gives off many branches. The posterior vena cava begins between the two kidneys and returns blood to the sinus venosus. Which vessel lies above (ventral to) the other? 077 Digestive Tract 1. Identify the esophagus, a very short connection between the mouth and the stomach. Lift the left liver lobe, and identify the stomach, whitish and J-shaped. The stomach connects with the esophagus anteri- orly and with the small intestine posteriorly. 2. Find the small intestine and the large intestine, which enters the cloaca. The cloaca lies beneath the pubic bone and is a general receptacle for the intestine, the reproductive system, and the urinary system. It opens to the outside by way of the anus. What path does food take through the digestive tract? List the organs in order from mouth to cloaca. JE Laboratory 31 The Vertebrates 431
Inquiry into Life Laboratory Manual, 16th Edition Opening the Frog 1. Place the frog ventral side up in the dissecting pan. Lift the skin with forceps, and use scissors to make a large, circular cut to remove the skin from the abdominal region as close to the limbs as possible. Cut only skin, not muscle. 2. Now, remove the muscles by cutting through them in the same circular fashion. At the same time, cut through any bones you encounter. A vein, called the abdominal vein, will be slightly attached to the internal side of the muscles. 3. Identify the coelom, or body cavity. Recall that vertebrates are deuterostomes in which the first embry- onic opening becomes the anus and the second opening becomes the mouth. 4. If your frog is female, the abdominal cavity is likely to be filled by a pair of large, transparent ovaries, each containing hundreds of black and white eggs. Gently lift the left ovary with forceps, and find its place of attachment. Cut through the attachment, and remove the ovary in one piece. Respiratory System and Liver 1. Insert a probe into the glottis, and observe its passage into the trachea. Enlarge the glottis by making short cuts above and below it. When the glottis is spread open, you will see a fold on either side; these are the vocal cords used in croaking. 2. Identify the lungs, two small sacs on either side of the midline and partially hidden under the liver (Fig. 31.7). What path does air take through the respiratory tract? List all structures it passes from the external nares to the lungs. 3. Locate the liver, the large, prominent, dark-brown organ in the midventral portion of the trunk (Fig. 31.7). Between the right half and left half of the liver, find the gallbladder. Circulatory System 1. Lift the liver gently. Identify the heart, covered by a membranous covering (the pericardium). With for- ceps, lift the covering, and gently slit it open. The heart consists of a single, thick-walled ventricle and two (right and left) anterior, thin-walled atria. 2. Locate the three large veins that join together beneath the heart to form the sinus venosus. (To lift the heart, you may have to snip the slender strand of tissue that connects the atria to the pericardium.) Blood from the sinus venosus enters the right atrium. The left atrium receives blood from the lungs. 3. Find the conus arteriosus, a single, wide arterial vessel leaving the ventricle and passing ventrally over the right atrium. Follow the conus arteriosus forward to where it divides into three branches on each side. The middle artery on each side is the systemic artery, which fuses behind the heart to become the dorsal aorta. The dorsal aorta transports blood through the body cavity and gives off many branches. The posterior vena cava begins between the two kidneys and returns blood to the sinus venosus. Which vessel lies above (ventral to) the other? Digestive Tract 1. Identify the esophagus, a very short connection between the mouth and the stomach. Lift the left liver lobe, and identify the stomach, whitish and J-shaped. The stomach connects with the esophagus anteri- orly and with the small intestine posteriorly. 2. Find the small intestine and the large intestine, which enters the cloaca. The cloaca lies beneath the pubic bone and is a general receptacle for the intestine, the reproductive system, and the urinary system. It opens to the outside by way of the anus. What path does food take through the digestive tract? List the organs in order from mouth to cloaca..
g re nd internal naris auditory tube glottis- b. a. vomerine teeth -maxillary teeth esophagus tongue ·lower jaw internal nares vomerine teeth openings to auditory (eustachian) tubes tongue 31-6