Lab 3: Shark Muscles
Pp. 45 - 48; 86 - 89
1) Read the manual as you dissect. Know the actions, origins and insertions of all muscles.
Be careful as you dissect. Make certain to use a sharp scalpel (and note that they dull quickly cutting through the tough skin of the shark). Make incisions lightly - don't stab the specimen; don't go too deep. Once an incision is made, use blunt dissection (with either the scalpel handle and/or using the "scissors technique"). As you dissect, watch what you are doing, note changes in color, layers, muscle fiber orientation etc. Muscle layers are separated from each other (and from the skin) by connective tissue. The connective tissue is white and "stringy". Muscles are striated and usually a yellowish color. If you are cutting several muscles where one is superficial to the other, do not cut them in the same place.
If you haven't discovered it yet, your lab manual has a glossary. Use it. It starts on page 265.
Your lab manual has dissecting instructions that you should follow. Here are a few modifications:
DO NOT completely skin the shark. This takes too much time. Make one mid ventral incision from the lower jaw posterior to the pectoral girdle. Peel back the skin on one side and try to find the muscles.
Make a mid-dorsal incision from the area around the spiracle back to the dorsal fin. CAREFULLY peel skin ventrally to expose the muscles around the mouth and over the gills. DO NOT try to pull all of the skin off of each external gill slit. You will also have to cut open one of the gill slits - scissors work best.
Peel some of the skin off the pectoral fin to see how the muscles insert onto the fin.
Axial Musculature: Myomeres, myosepta, horizontal septum, epaxial and hypaxial musculature.
Fin Musculature: Flexors (aka adductor) and Extensors (aka abductor).
Branchial Musculature - Constrictors: Spriacular , adductor mandibulae, 2nd dorsal constrictor, 3rd - 6th dorsal constrictors (as a group, not individually); 1st ventral constrictor (intermandibularis); 2nd ventral constrictor (look on the underside of the 1st, these two can be very difficult to separate; look for different muscle fiber orientations); 3rd - 6th ventral constrictors.
Levators: Levator palatoquadrati and cucullaris.
Hypobranchial musculature: Coracomandibularis, coracohyoids, coracoarcuals, coracobranchials.
For a lateral view of shark musculature, click here.
For a ventral view of shark musculature, click here.
