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SC BIOL 110 - lab workbook part 3 frogs

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PHYLUM CHORDATAThe Chordates you are most familiar with are in the Sub-phylum Vertebrates whose animals are characterized by having a backbone and a skull. LA FrogEXTERNAL ANATOMYNote the head, trunk, and sacral hump (produced by internal pelvic girdle bones). The cloacal aperture is an orifice through which solid waste, urine, and egg/sperm are expelled. It is located on the upper surface about where the hind legs join. The eyes are protected by eyelids and a covering over the eye, a transparent nictitating membrane. This membrane allows the frog to open his lids and see underwater without fear of damage. Humans have a vestige of this membrane in the corner of their eyes. The tympanic membrane functions as the ear of the frog. Beneath it (not seen) is the eustachion tube, connecting the mouth cavity to the inner membrane cavity.INTERNAL ANATOMYThe mouth opening is too small to adequately see inside the mouth and identify required structures. You must cut through the jaw bone as shown. Insert a scissor blade into the mouth and cut through the jaw where upper meets lower on both sides of the mouth.Identify and know structures shown.You need to open the abdominal cavity.Make an incision first beginning at the intersection of 1 & 3 and cut toward head. You need to cut through the pectoral bone between the forelegs. Next make cuts from the center cut as shown by lines 2 & 3. go at least halfway up the sides of the frog. Remove the flaps of epidermis and muscle. Bend the frog over backwards holding it between thumb and forefinger. If finger-like yellow fat bodies are present carefully cut them off at their base. If the abdominal cavity is filled with eggs remove them careful not to damage/destroy other internal parts. It may also be necessary to remove the white tubularoviducts if they are also obstructing organs.Internal Anatomy Cont.Hold the frog in a back bend position to see best.READ THE PARAGRAPH FIRST TO GET A FEEL FOR WHAT YOU NEED TO SEELocate the liver (2), a many lobed dark structure sited between the forelegs. The heart (3), is over the center liver lobes. Somewhat hidden (tucked down under) the outer lobesof the liver are the lungs (4), dark in hue and collapsed. Looking at the innards with the head away from you, flip up the left lobes and note a greenish sac, the gall bladder. It stores bile, a fluid secreted by the liver. Bile eventually empties into the small intestine where it aids in digestion. Locate the stomach (1) and note the esophagus, the tube leading from the mouth to the ‘top’ of the stomach. It might help if you insert a probe into the esophagus via the mouth and feel for it in the abdominal cavity. The stomach dramatically narrows to become the small intestine (8). The first ½” of the small intestine is called the duodenum. Follow the small intestine down to where it suddenly enlarges; that’s the large intestine (7). The large intestine narrows and becomes the cloaca. (To see the cloaca it is necessary to cut through the pelvic girdle. Ask the instructor to do it.) Surrounding the lower half of the large intestine, looking like a deflated transparent bag/tissue, is the deflated urinary bladder (9). On the right hand side of the frog, under the small intestine, near the midline, looking like it is attached tothe backbone is a spherical red/brown organ, the spleen. Binding the organs together are clear/cloudy membranes called mesentery tissue. This tissue prevents the organs from flopping around. There is mesentery tissue between the stomach and the small intestine. Note that it is not clear/cloudy but has a substance “in” it. This formless mass is the pancreas, an organ that produces enzymes that aid in digestion.Underneath of the small intestine and on either side of the backbone are long brownish somewhat flat, paired kidneys. Yellow, many lobed fat bodies may also be present. In males, yellowish, pale, oval testes are located on the upper portion of the kidneys. They are a little thicker than a pencil lead and about 3/16ths” long. Sperm passes via tubes called vasa efferentia to the cloaca.Ovaries are also located on the surface of the kidneys. They appear as white tubes/sacs, somewhat twisted. Do not confuse them with the white coiled oviducts which will carry eggs from the ovaries to the


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