Thursday, April 12, 2012

Human Biology: Chicken Leg Dissection Lab Project/Unit 3

The objective in this lab project is to be able to identify and describe the structure and function of tendons, ligaments, and cartilage. We also need to be able to identify muscles and their functions. And finally there is bone and what if consists of. This will also give us a little more experience dissecting fresh material.

The material used for this lab:

Chicken leg
Tray with foil covering
Paper towels


cutting skin

I covered a tray with tinfoil, so that I could just pick up the foil to throw away contents later. Then I laid out all the other instruments I would need.  I washed the chicken leg with soap and dried with a paper towel. I examined the outside of the leg first – then carefully cut the skin off, noting the connective tissue underneath. I observed the fat tissue on the outside of the skin. There were bundles of pink muscle underneath the skin. I then probed and found a tendon (shiny, white tissue). Next, I removed a single muscle, cutting away the tendons and prying it from the
all skin is off
bone. Then I proceeded to remove all muscle tissue, exposing the rest of the bone. Next, I operate the leg joint, noting the movement. Then I cut the ligaments at the joint to observe how the bones fit together. Then I observed the interior of the bone (I accidentally bought just the leg without the thighs – so my bone interior was actually exposed). Once done, I threw everything away and washed knife, scissors, and hands thoroughly.

one muscle separated

cut to the bone

all muscle off

connective tissue just below the skin
The loose, connective tissue under the skin was clear and elastic. It is made of fibroblasts and a matrix with elastin and collagen fibers. The fat in the skin was lumpy, gelatinous and somewhat yellow. Two of the functions of fat include providing energy (which is its main function), and storing energy. By supplying energy, fat allows protein to be used for repairing and building tissue, rather than supply energy.  We also eat more than what we need to use at the current moment, so fat stores the rest. These fat cells are called adipocytes, sometimes just referred to as adipose.

There were several muscles present in the leg. You could see some distinction as well as tendons that were holding them together. Where I noticed this the most was under the joint. You could definitely see some distinction between these muscles and the connective tissue holding them together.

The tendons were white and shiny and at the ends of the muscle. They were rather tough, fibrous bands of connective tissue. They felt almost like bone, they were that hard. There was just a little bit of give to them.

Skeletal muscles are striated muscles that are arranged in bundles called fascicles. Theses fascicles are enclosed in a sheath called a fascia. And each fascicle contains anywhere from a few dozen to thousands of muscle fibers, or cells. Muscles cells have more than one nucleus and they are located just underneath the cell membrane because most of the interior of the cell is packed with myofibrils (long, cylindrical structures arranged parallel). And the myofibrils contain proteins called actin and myosin. (It is the interaction of these two proteins that allow muscle contraction). Besides being able to contract, allowing us to move, muscles resist movement, and they also generate heat.

showing the hinge movement of the synovial joint
You will notice from the picture that the joint moves like a hinge, with flexion and extension movements. After cutting away the ligaments, (smooth and thick, and hold bone to bone) we can observe how the bones fit together. They are connected via hyaline cartilage at this synovial, hinge joint. When the cartilage wears away, there is too much friction. This causes pain, inflammation, loss of movement, and disability in humans. It also places more stress on the bones, which can cause bone spurs. (Currently, there are a couple of surgeries to try and correct this.) The synovial joint does have an added protection against this occurring, however. Besides the hyaline cartilage, inside of the synovial membrane, a fluid is secreted in the interior cavity that also helps to reduce friction.

inside the bone
Last, but not least, we see the inside of the bone. This bone is spongy bone, which is made from trabeculae. Trabecula is made of calcium and living cells. The spaces between the trabeculae are filled with red bone marrow. Within red bone marrow are stem cells that are responsible for RBC production, WBC or leukocyte production, and platelet production. To break this down even further, stem cells create:

Erythroblasts  - this translates to RBC’s
Myeloblasts – this translates to Neutrophils, Eosinophils, and Basophils (granular leukocytes)
Monoblasts – translates to monocytes (agranular leukocyte)
Lymphoblasts  - translates to lymphocytes (agranular leukocyte)
Megakaryoblasts – translates to platelets  


In summary, I have demonstrated some of the components of the muscular system. And explained some of their function. It was interesting to see the texture and feel of a tendon. Maybe this explains why you can have tendonitis and it can feel like you have broken a bone, but you haven’t. You have an inflamed tendon instead. This lab helped to give me a better understanding of how it all works. Especially the stem cells and what they produce.

Human Biology: Concepts and Current Issues, 6th edition, Johnson  (Biology: The Unity and Diversity of Life, 12th edition, Starr, Taggart, Evers, Starr

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