  Arterial System (continued). 1. Trace the carotid arch, which gives off: (a) Two lingual arteries having a common point of origin near the carotid gland. (b) A carotid artery passing to the head. At its origin it is slightly swollen into the carotid gland. 2. Trace the systemic arches which run backwards on each side of the body, meeting posteriorly to form the dorsal aorta. Each systemic arch gives rise to an artery which branches into:— (i) A scapular artery to the pectoral girdle. (ii) A cutaneous artery to the skin. (iii) A brachial artery to the arm. Trace the dorsal aorta backwards, and note that it gives rise to the coeliaco-mesenteric artery about midway between its origin and the origin of the first pair of renal arteries. The dorsal aorta then passes between the kidneys giving four renal arteries to each, and proceeds backwards and divides into an internal iliac artery to each leg. This artery lies between the femoral and the sciatic veins. From each of these arteries a branch is given off which divides into: (i) An iliac artery to the muscles around the ilium. (ii) A cutaneous artery to the skin of the body, just anterior to the leg. (iii) A small artery to the anterior dorsal surface of the hind limb. 3. Trace the pulmo-cutaneous arch, which gives off:— (a) A pulmonary artery, running along the outer side of the whole length of the lung. (b) A cutaneous artery, which at first runs forwards to the base of the arm, and becomes spread out on the skin of the back of the head. [In the Frog 1. The carotid arch gives off:— (a) A lingual artery supplying the tongue. (b) A carotid artery, running round the side of the oesophagus, and supplying the head. At its origin it is slightly swollen into the carotid gland. 2. The systemic arches run backwards on each side of the body, and meet posteriorly to form the dorsal aorta. Each systemic arch gives off:— (a) A subclavian artery to the shoulder and fore-limb. (b) An occipito-vertebral artery to the head and the vertebral column. (c) An oesophageal artery to the dorsal wall of the oesophagus. (d) A laryngeal artery to the larynx. At the point where the dorsal aorta is formed, note the origin of the coeliaco-mesenteric artery which sends branches to the stomach, liver, intestine, and spleen. Trace the dorsal aorta backwards and note that it passes between the kidneys, to each of which it gives off four renal arteries and then it divides posteriorly into an iliac artery to each leg. The iliac artery is continued backwards as the femoral artery in the leg. 3. The pulmo-cutaneous arch gives off:— (a) A pulmonary artery, running along the outer side of the whole length of the lung. (b) A cutaneous artery, which at first runs forwards and upwards, and then turns backwards, supplying the skin of the back and the sides of the head.] Make a complete sketch of the arterial system. Cut out the heart, leaving attached to it as much as possible of the large vessels. Note the sinus venosus, truncus arteriosus, auricles, and ventricle. Open the auricles and observe the division between them and the openings of the veins passing into them. Make a section through the auricles and ventricle noting the thick muscular walls of the ventricle and the valves between it and the auricles. Respiratory System and Alimentary System (continued). 1. Remove the mylo-hyoid muscles to expose the hyoid apparatus. Pass a seeker through the glottis to one of the lungs and slit it open with a pair of scissors. Examine the structure of the lung. 2. Remove the whole of the alimentary canal with the lungs, liver, pancreas, and spleen, by cutting through the oesophagus and the large intestine before it joins the cloaca, and detaching it from the roof of the body cavity without injuring the kidneys and the reproductive organs. Draw the complete alimentary canal. Urinogenital System. Note the kidneys, two elongated, flattened, dark-red bodies lying one on each side of the vertebral column towards the posterior end of the abdominal cavity. From the outer edge of each kidney a ureter arises and runs backward, opening into the cloaca on the dorsal side, opposite the opening of the urinary bladder. [In the Frog the adrenal bodies may be seen on the ventral sides of the kidneys as small yellow patches.] In the male Platana note:— (a) The testes, a pair of ovoid pale-yellow bodies attached to the dorsal wall of the body cavity by a fold of the peritoneum. They lie on the ventral sides of the kidneys and are connected to them by efferent vessels which pass into the kidneys. (b) The corpora adiposa or fatty bodies lying in front of the kidneys. (c) The ureters which run along the outside of the kidneys and unite posteriorly to form a single duct opening into the cloaca. [In the Frog the ureters do not join together but open separately into the cloaca. Each ureter has a slight swelling, the vesicula seminalis, on its outer side.] In the female Platana note:— (a) The ovaries, a pair of irregularly-lobed organs usually consisting of a mass of rounded black and white bodies, the ova. The ovaries are attached to the dorsal wall of the body cavity by a fold of the peritoneum. (b) The corpora adiposa lying in front of the kidneys. (c) The long convoluted oviducts opening into the body cavity in front and into the cloaca behind. The ureters open separately into the cloaca in the female. Make a drawing of the urinogenital system. |
|
