The flap of body wall that contains the navel can be folded posteriorly to reveal the internal organs of the abdomen. Extend a single cut along the midline of the ventral surface of the animal to about 2 cm. Cut completely through the body wall in the abdominal area but keep the cut shallow in the neck region. A cut is made on the side of the animal from the point just posterior to the diaphragm dorsally.
A similar cut is made on the other side. These two cuts will enable you to spread open the abdominal cavity. Use a scalpel to cut the sides of the mouth so that the bottom jaw can be opened for easier viewing see figure You will need to cut through the musculature and the joint that holds the lower jaw to the skull.
Open the jaw wide enough so that the glottis and epiglottis are exposed. The epiglottis projects up through the soft palate into a region called the nasopharynx. The hard palate and soft palate separate the nasal and oral cavities. When breathing, air passes through the nasal passages to the pharynx. The pharynx is the space in the posterior portion of the mouth that both food and air pass through. From the pharynx, it passes through the glottis to the trachea.
Carefully, peel the skin away from the incision in the neck region using a blunt probe a needle or the point of scissors will do if a blunt probe is not available. Use the probe to peel away muscle tissue until the thymus gland on each side of the trachea is exposed. Use a probe to separate the two lobes of the thymus gland and to further separate the musculature over the trachea. The thyroid gland is darker and lies between the posterior ends of the two lobes of the thymus gland.
Figure The surrounding tissues have been separated to reveal the thyroid gland. Continue separating the tissue with a probe until the trachea and esophagus are exposed. The esophagus is dorsal to the trachea. The large hard structure attached to the trachea is the larynx. It contains the vocal chords.
In the photograph below, the heart and blood vessels of the neck region have been removed so that the trachea can be seen more clearly. You should not remove these structures yet because you will need to identify the blood vessels later in the dissection.
Observe how the diaphragm attaches to the body wall and separates the abdominal cavity from the lung pleural and heart pericardial cavities figure 16 and 18 below. Contraction of the diaphragm forces air into the lungs. You have already seen the nasopharynx, hard palate, soft palate, epiglottis, glottis, trachea, and larynx. Follow the trachea to where it branches into two bronchi and observe that each bronchus leads to a lung.
The left lung contains three lobes and the right lung contains four. Each lung is located in a body cavity called a pleural cavity. You have already seen how the esophagus leads from the pharynx through the neck region. Using a probe, trace follow the esophagus to the stomach. Identify the small intestine and large intestine. Find the posterior part of the large intestine called the rectum and observe that it leads to the anus. Locate the cecum , a blind pouch where the small intestine joins the large intestine.
Identify the liver. Lift the right lobe and find the gallbladder. This structure stores bile produced by the liver.
Find the bile duct that leads to the small intestine. The pancreas is located dorsal and posterior to the stomach. It extends along the length of the stomach from the left side of the body your right to the point where the stomach joins the small intestine.
Lift the stomach and identify this light-colored organ. The spleen is an elongate, flattened, brownish organ that extends along the posterior part of the stomach ventral to above the pancreas. The cecum is a blind pouch where the small intestine joins the large intestine.
It houses bacteria used to digest plant materials such as cellulose. The cecum is large in herbivores but much of it has been lost during evolution in humans.
The appendix in humans is the evolutionary remains of a larger cecum in human ancestors. Duodenum, gallbladder, liver, lungs, large intestine, pancreas, small intestine, stomach. The liver has been lifted to reveal the gallbladder.
Large intestine, pancreas, small intestine, spleen, and stomach. The cecum is found at the point where the small intestine joins the large intestine. The drawing below shows some of the major arteries that carry blood to the body. Blood vessels that branch from the aorta carry blood to most of the body. The pulmonary artery is capable of delivering a large amount of blood to the lungs but the lungs are not needed to oxygenate the blood of a fetus, so most of the blood is diverted to the aorta.
This diagram shows that the ductus arteriosus connects the pulmonary artery to the aorta and diverts blood that would otherwise go to the lungs. Shortly after birth, the ductus arteriosus closes and blood in the pulmonary artery goes to the lungs instead of the body. Blood passes from the left ventricle through the aortic arch and aorta to the body. The first branch of the aorta is the brachiocephalic artery. The second branch is the left subclavian artery which goes to the left front leg.
The right subvclavian carries blood to the right front leg and the carotids carry blood to the head. The pericardium is a membrane that surrounds the heart and lines the pericardial cavity. It contains a lubricating fluid and isolates the heart from body movements such as the expansion and contraction of the nearby pleural lung cavity. To view details of the aortic arch, ductus arteriosus, and pulmonary artery, it will be helpful to remove the left lung.
With the left lung removed, the heart can be pushed to the right side to reveal the aorta and other blood vessels shown in figures 33— Aortic arch, coronary artery, left atrium, left ventricle, pulmonary artery, right atrium, right ventricle. Aorta, aortic arch, left atrium, brachiocephalic artery, ductus arteriosus, lung, pulmonary artery, pulmonary trunk, left subclavian artery,.
Aorta, aortic arch, left atrium, brachiocephalic artery, left common carotid artery, right common carotid artery, ductus arterious, pulmonary artery, pulmonary trunk, left subclavian artery, right subclavian artery, trachea, left ventricle.
Aortic arch, left atrium, brachiocephalic artery, left common carotid artery, right common carotid artery, larynx, pulmonary trunk, left subclavian artery, right subclavian artery, left ventricle. Anterior vena cava, coronary artery, larynx, posterior vena cava, right subclavian vein, trachea.
The aorta supplies the body with fresh blood. Underneath they aorta is the pulmonary artery, which takes blood to the lungs, in a fetal pig this vessel is unused the fetus doesn't get breathe to get oxygen and a shunt called the ductus arteriosus allows fetal blood to bypass the pulmonary vessels and go straight to the aorta.
Lift the heart to look on its dorsal side toward the back , you should be able to see the anterior and posterior vena cava, which brings blood from the body back to the heart.
Follow the aorta to where it arches appropriately called the "aortic arch", if you carefully pick away the surrounding tissue, you will find three main branches from the aortic arch. Toward the pig's right, two branches move to the arm and to the neck. The rightmost branch is the right subclavian artery and it supplies blood to the pig's arm and shoulder. Next to the right subclavian and heading directly toward the pig's head is the bicarotid, which will divide in a Y shape to form the left and right carotid arteries, which supply blood to the head and neck.
Toward the pig's left, you'll find the left subclavian artery which provides blood to the left shoulder and arm. Also note the arteries that run along the ribs of the pig, these are the intercostal arteries. Trace the abominal aorta to the lower part of the body, careful teezing of the tissue will reveal several places where it branches, though some of the arteries may have been cut when you removed organs of the digestive system.
The hepatic artery leads to the liver. The splenic artery leads to the spleen may not be visible. The renal arteries lead to the kidney. The mesenteric artery leads to the mesentery and branches into many smaller vessels.
0コメント