Cat Muscle

Cat Muscle - Lab #4 Vertebrate Muscle Vertebrate Skeletal...

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Lab #4 Vertebrate Muscle 1 Vertebrate Skeletal Muscle Structure Laboratory #4 & #5 Today we will examine the muscular system of the cat, with particular emphasis on the muscles of the hind limb. The goal of this lab is to consider the relationship between fine and gross muscle structure and function. By focusing on cat hind limb muscle today, you will learn general principles of muscle structure and function that you will then apply to different systems in subsequent labs. In addition, there are many similarities but also a few interesting differences between the anatomy of the leg in the cat and in humans. Remember, muscle cells develop embryonically from mesenchyme cells, which form myoblasts that become myocytes, or muscle fibers. Based on fiber structure, there are 3 general types of muscle: 1) skeletal , 2) cardiac , and 3) smooth . Cardiac muscle is found in the walls of the heart. Smooth muscle is found in the walls of blood vessels, and in some visceral organs. Skeletal muscle fibers have a complex organization into distinct units or muscles. Skeletal muscles attach directly to the skeleton or indirectly attach via tendons (which are extensions of connective tissue in the muscle). The origin of a limb muscle is its proximal end; the insertion is its distal end. Usually skeletal muscles are arranged in groups of agonists/antagonists: one muscle (the agonist) pulls on a structure in one direction and the second muscle (the antagonist) pulls on it in the other direction (e.g., the triceps is an antagonist of the biceps). Even though we are focusing on the muscular system of the cat it is important to note that there are significant differences between some of the muscles of the cat (a quaruped) and a human (a biped), these differences are found in both the hindlimb and in the muscles of the back and shoulders. In the hindlimb the major differences between the cat and the human are the relative masses of some of the proximal hip musculature. The hamstring muscles make up the largest muscle group in the cat and include the biceps femoris, the semitendinosus and the semimembranosus. In the cat the hamstring muscles are twice as massive as the antagonistic group of muscles the quadriceps (vastus lateralis, vastus medialis, rectus femoris, vastus intermedius). In humans this trend is reversed and the quadricep muscle group weighs approximately twice as much as the hamstrings. Similarly the gluteus maximus in quadrupeds is a relatively small muscle and it accounts for only 6% of the mass of the muscles acting at the hip. In humans the gluteus maximus is the largest muscle that acts on the hip joint and it accounts for 18.3% of the muscle mass that is capable of acting at the hip and is thought to play an important role in human running (Lieberman et al., 2006). In addition humans are missing the caudifemoralis. Anatomical variation between the cat and the human can also be found in the muscles of
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This note was uploaded on 02/09/2012 for the course BIO 102 taught by Professor William during the Spring '11 term at Harvard.

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Cat Muscle - Lab #4 Vertebrate Muscle Vertebrate Skeletal...

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