Practical Activity Portfolio
In the prawn dissection practical activity, our task was to dissect a prawn and make observations about its skeletal system. The prawn has an thin exoskeleton composed mainly of chitin and calcium carbonate. Chitin is a type of sugar found in the cell walls of mushrooms and other fungi. The calcium carbonate is there to give the exoskeleton strength. The role of the exoskeleton is to protect the prawn's vital organs, such as their heart, brain, gills and stomach. Other animals that have this type of skeletal system are crustaceans, such as crabs and lobsters. Benefits of the prawn's skeleton is that it gives some protection from outside attackers, as it hides the prawn's body and vital organs in the shell. However, the skeleton is not very strong, and is easily broken by human hands, or possibly a stronger predator than the prawn.
When prawns grow, their shells do not. Prawns regularly shed their skeleton, and then grow a new one, which would be larger, adjusting to the prawn's larger body size. The prawn's skeletal system is called an exoskeleton.
The prawn's skeleton is different to ours, as we have an endoskeleton, which is a skeleton on the inside of our bodies. The prawn has an exoskeleton, as mentioned earlier, which is a skeleton on the outside of their bodies. Our skeleton is composed of bones, which in turn contain bone marrow and bone tissue, unlike a prawn's skeleton, which contains chitin and calcium carbonate.
Worms do not have skeletons made out of bone, like us, or chitin, like the prawn. Instead, they have hydroskeletons, which are essentially skeletons made out of fluid. This fluid is kept under pressure, and in a closed section of the body. The fluid, with the help of several muscles in the worm's body, is used to change the shape of the body and produce movement. In each section of a worm's body, there are bristles, called setae. Setae help the worm to move freely.
Cuttlefish Skeletal System
The cuttlebone was a little rough to the touch. It had curves on it, which stood out a little. It was very chalky, and left a white powder on my hands after I had held it. The cuttle 'bone' is not actually a bone at all, as cuttlefish are invertebrates. This means that they do not have any bones. It is found inside the cuttlefish, and is used as a flotation device to help raise and lower them when they are in water. This is an internal 'skeleton'. It is composed mainly of aragonite, which is a type of mineral. It is also rich in calcium, which is why it is fed to budgerigars.
Skeletal System of Humans
Our skeletal system is comprised of bones. At birth, a human will have 270 bones in their body. Once they reach adulthood, however, some of these bones have joined together, and now there are only 206. Our skeleton can be split into two groups, the axial skeleton and the appendicular skeleton. The axial skeleton contains all of the bones that help us to move, for example, the ulna and radius help our arms to move. The appendicular skeleton contains the bones that protect our internal organs, like the ribs protect the heart and lungs.
There are four layers to most of our bones. The first is the tough, outer layer called periosteum. It contains our blood vessels and nerves. The second layer is compact tissue, which is hard and smooth. It protects the third layer, which is spongy tissue. This is a honeycomb-like structure that allows the bone to be both strong and lightweight. The very inner substance is the bone marrow, which is jelly-like. It produces blood cells.
The role of our skeletal system is to help us to move and be flexible, support us, and to protect our internal organs. The bone marrow, as mentioned earlier, produces blood cells. It is found in the cavities of most bones. Our skeletal system is called and endoskeleton. All mammals and birds have endoskeletons.
Name That Bone
Chicken Wing Dissection
In the chicken wing dissection, my partner and I got to explore the muscles and bones of the wing of a chicken. The upper wing, lower wing and wingtip correspond to the upper arm, forearm and hand, respectively, in humans. When I pulled on the muscles in the upper wing, the wing straightened and bent. The muscles that are allowing this to happen are the bicep and tricep of the chicken. The tricep is the extensor, and the bicep is the flexor. When I tugged the muscles in the lower wing, the wingtip extended and bent.
Below is a diagram of the main muscles in the chicken wing, and whether they are flexor muscles or extensor muscles.
Next, my partner and I cut away part of the muscle tissue, and found tendons, the tissue that connects the muscle to the bone. It was white, and it felt rough. We then looked at the elbow joint. Two bones were joined together by tissue called ligaments. The two bones formed a hinge joint, as opposed to the joint that connects the wing at the shoulder, which is a ball-and-socket joint. The cartilage that lined this joint was a tough, white substance.
Finally, we cut away all of the muscle, to reveal the bones of the wing. We identified the humerus, the ulna and the radius.
Below is a diagram of the chicken wing with the bones labelled.
In the heart dissection, we examined a sheep's heart from both the inside and out. First of all, we looked at the appearance of the heart. The heart was a pinkish-red colour. The exterior was quite smooth, and I could clearly see some blood vessels running through it. Also clear were a couple of arteries and veins.
Below is a rough sketch of the heart.
Next, we looked at the coronary artery, which was visible on the surface of the heart. It was red, and very thin. If it were to clot, the artery would swell up a little bit, because the blood would be stuck there, as it cannot flow backwards or forwards.
We located the left and right sides of the heart. We knew which was which because the left side is thicker than the right. There was a lot of fat surrounding the heart. We could just make out the aorta, but unfortunately most of it had been sliced off. We could also find the vena cava and the pulmonary artery.
Oxygenated blood leaves the right atrium in an artery and travels to the rest of the body. Here, the blood drops off oxygen, so it is now deoxygenated. The blood travels back to the heart via a vein.
The aorta was very thick. It needs to be this thick to withstand the high blood pressure of the blood running through it. It takes blood to the rest of the body.
The vena cava was not as thick as the aorta, because the pressure of the blood travelling through it is a lot lower. The vena cava goes back into the heart through the left atrium. We poured water into the vena cava, and it trickled through the heart and came out of the pulmonary artery. These two vessels are connected. We were able to put a finger in each one and have them meet. When we poured water into the pulmonary vein, it came out of the aorta.
After we had examined the outside of the heart, we cut into the heart and began to examine the inside. First of all, we cut into the left ventricle. We saw a couple of valves inside it. The valves make sure blood only flows in the one direction, never the other.
Next, we cut open both the left and right atria. Below is a table comparing the thickness of various parts of the heart.
Why do you think it is like this?
The thickness of the walls of the ventricles compared to the atrium
The atrium walls were thicker than the ventricle walls
This is because the blood in the atrium has a higher pressure
The thickness of the wall of the left ventricle compared to the right ventricle
The left ventricle is thicker than the right
The left ventricle has to pump blood further
The muscle separating the right and left sides of the heart
The septum was quite thick and prominent
This is to make sure any blood doesn’t accidentally cross over it
The size (volume) of each of the chambers. Are they different sizes? Which one is the largest?
The left ventricle is the largest of the four chambers
The walls of the left ventricle are the thickest. Also, the left ventricle has to pump blood the furthest.
Below is another table indicating the location and role of the following structures.
Where is it located
Describe its role
In the bottom left area of our heart
Sends blood to the left atrium
Bottom right section or of our heart
Sends blood to the right atrium
In the top left part of the heart
To pump blood out of the heart to the body and from the lungs to the heart
The top right of the heart
Pumps blood to the lungs and from the body
Extending from the left atrium to the rest of the body
To pump oxygenated blood from the heart to the body
The right atrium- goes to the lungs
Sends oxygenated blood from the lungs to the heart
Extending from the right atrium to the lungs
Pumps deoxygenated blood from the heart to the lungs
Extending from the right atrium to the rest of the body
To pump deoxygenated blood from to the body to the heart
Lining the veins
To ensure blood doesn’t flow the wrong way
In between the left and right sides of the heart
To separate the two sides of the heart
Walking the Heart Activity
In the Walking the Heart activity, the class went onto the oval and was split into three groups. We were each allocated a section of the basketball courts or tennis court and were instructed to draw a large drawing of the box diagram above with chalk. We had a lot of sports equipment at our disposal, including lacrosse sticks, skipping ropes and sashes. Once we had done that, we walked in our diagram, giving the rest of the class a demonstration of how blood travels through the body.
In the pluck activity, we inserted a bicycle pump into a pair of sheep's lungs and blew them up, noting what happened. The trachea, extending from the lungs, was hard to the touch. It looked stiff, but was actually surprisingly springy. The cartilage rings prevented the trachea from collapsing, breaking or folding in on itself.
When deflated, the lungs were a dark red colour, mottled with light pink spots. They were a little baggy. When inflated, however, the part that was being inflated swelled up and became white.
The heart connects to the lungs by the pulmonary artery and the pulmonary vein, which take blood back and forth from the lungs to the heart and vice versa, exchanging oxygen.
The diaphragm controls our breathing. It does this by contracting when the lungs inflate, to give the lungs more room. It expands when the lungs deflate, pushing them up.
The liver produces bile. It also helps to store glucose as glycogen, and processes alcochol.
The skeletal and muscular systems are closely connected. This is because muscles are joined to bones with tendons, as I saw in the chicken wing dissection. Also, they are both related to movement. The bones in our skeleton move together to give us motion and flexibility, and the muscles allow us to have the strength to move.
The circulatory and respiratory systems are also closely connected. The heart pumps deoxygenated blood to the lungs, where gas exchange happens between the capillaries and the alveoli, and then the now oxygenated blood returns to the heart, ready to be used by the rest of the body.