Body Systems: Prac Portfolio

By Ella Baldwin

The Skeletal System

Prawn

The prawn has an exoskeleton, meaning its skeleton is on the outside of its body. It is a hard shell made from chitlin, and is broken up into sections to allow movement. For the prawn to swim, it uses its muscles and moves in the breaks of the shell. The shell is grown over the prawn, and when the prawn outgrows it, the shell is shed and another is formed. Some advantages of having an exoskeleton such as this are that the shell protects the prawn from harm, but also protects its muscles. Some disadvantages of this system include; if the shell brakes or falls away, the prawn is highly vulnerable whilst the shell is growing back, making for easier prey.

Worm

The worm has a hydro skeleton, implying that it doesn’t actually have a skeleton, but is supported by its surroundings, in this case: dirt or soil. The movement of the worm is created by a series of muscle contractions to transfer the body through the dirt.

Cuttlefish

The cuttlefish has an endoskeleton, because it's skeleton is on the inside, and you cannot actually see the cuttlebone on the living creature. The cuttlebone is hard, dry and porous, but is also very light, enabling buoyancy for the fish so it has structure but will not sink. The cuttlebone is made from calcium carbonate, a substance used in many shells from various animals.

Hard, Dry Cuttlebone

Human

The human skeleton is an endoskeleton, and is strong, lightweight and made from bone. The role of the human skeletal system is to support the soft tissues, preventing the body being a pile of tissues, organs and muscle. Part of the skeleton protects the organs from harm, called the axial skeleton, which has 80 bones in total. The axial skeleton includes, ribcage, vertebrae and skull. Another part of the skeleton allows the body movement, and is called the appendicular skeleton, having 126 bones. The appendicular skeleton includes the shoulder blades and all the bones in the arms and legs. The role of bone marrow in the human bones is vital. It produces red and white blood cells, along with platelets, which help clot the blood if it reaches the air outside the body. Bone marrow is found inside the spongy bone, which is on the inside.

Bones are broken into two categories: compact bone and spongy bone. The compact bone is the hard outer layer that gives the bone most of its strength. The spongy bone lies inside the compact bone, and looks similar to honeycomb. It provides the bone with a strong interior, despite the lightness. Bone marrow fills the holes inside the honeycombed spongy bone. Bones also contain calcium phosphate, which hardens the bones, collagen, which gives them the necessary elasticity, and blood vessels, which supply the damaged areas with nutrients and oxygen.

The human skeleton changes as we grow from a child’s body to an adult's. As a baby, the skeleton is made from flexible cartilage, but within a few weeks, the bones begin to develop. The cartilage gradually starts to be replaced by calcium phosphate and collagen, and it takes around 20 years for this process to be complete. The bones of children and young teens are smaller than those of adults and contain growth plates, which consist of columns of multiplying cartilage cells that grow in length, which then change into hard, mineralized bone. Girls mature at an earlier age than boys, meaning their growth plates change into hard bone at an earlier age.

Other animals that possess an endoskeleton include dogs, pelicans and elephants. Most of the animals that live on land have an endoskeleton, although not all.

Labelled diagram of the Human Skeletal System

The Muscular System

Chicken Wing

Structures in the upper and lower wing of the chicken, along with the wing tip, correspond to the human body as the upper arm, lower arm, and hand, having the humerus, radius and ulna, as well as the biceps, triceps, radialis longus and the ulnaris muscles.

When you tug on the muscles in the upper wing (i.e. the biceps), the lower arm at the elbow joint is moving up with it, showing that the whole arm is connected through ligaments and tendons. When pulling at the biceps, the triceps are lengthening out to allow for the biceps to contract, and you are able to see the tendon connecting the muscle to the bone moving up and down with the motion. These muscles correspond to the biceps and triceps in the human, as I have been referring to them, and depending on the movement, one muscle is the extensor, and the other is the flexor. As the chicken wing’s relaxed position is up, with the elbow bent and the wrist also bent, straightening it would mean that the triceps and ulnaris are the flexors and the biceps and radialis longus are the extensors.

When you tug on the muscles in the lower wing, corresponding to the human radialis longus and ulnaris, the wing tip moves up and down with the action. You can see the tendon holding the muscle to the bone, and how the tendons and ligaments are working together to create movement.

The tissue that connects muscle to bone is called a tendon, and is a thin, white band that appears to be the extension of the muscle. The tissues that connect the bones at the elbow joint are called ligaments. The different joints in the wing have different styles and named joints, for example, the elbow joint is a hinge joint, because it can only move back and forth. The shoulder joint is a ball and socket joint, which allows movement in all directions. The cartilage in the wing covers the ends of the bones, and is very smooth and slippery, and is a shiny white.

The bones found in the chicken wing are the humerus, radius and ulna, although the wing tip doesn’t actually have any bones in it.

The Heart and Circulatory System

Heart Dissection Prac

Aim: To locate the chambers and major vessels of the heart and to understand the processes the blood goes through.

External Examination

1. Describe the appearance of the heart. What does it look like? How does it feel? Are there any features you can describe?

The heart is red, white and reddy brown, with fat and blood covering it. There are blood vessels visible around the majority of the heart, and you can see the openings to the vena cava and aorta. It feels very firm and muscular; the walls are really thick and firm. Fat covers the top of the heart as well, and is a creamy white colour.

2. Provide a sketch of the front exterior of the heart. Label all the key parts.

Annotated sketch of the Heart

    3. Find the blood vessels on the surface of the heart muscle. These are the coronary arteries. They carry nutrients and oxygen to the heart muscle.

    a. Describe what it looks like.

The coronary arteries look like thin, red/brown branches that appear to be outlining the exterior of the ventricles. They are well protected by heart tissue and look buried into it.

b. What do you think would happen if this artery was blocked by a clot?

The heart wouldn’t get enough nutrients and oxygen to function, possibly causing an angina.

4. How do you know which is the left and right side of the heart?

The left ventricle wall is much thicker and more muscular than the right. This is because it has to pump masses of blood into the aorta, the major artery.

    5. Have a feel of the thickness of the heart muscle at the top and bottom of the heart. Describe the following features;

    a. The thickness of the muscles at the top of the heart.

It is very firm, strong and muscular, and also has some spring to it.

b. The thickness of the muscles at the bottom of the heart.

Firm, muscular and springy, has more dense muscle than the top of the heart.

c. The amount of fat surrounding the heart.

There is lots of fat surrounding the heart and the coronary arteries. There is also a large amount in the upper area of the heart. The fat is hard and fairly thick.

d. Any major vessels entering and exiting the heart.

The major vessels entering and exiting the heart are the aorta, vena cava, pulmonary artery and pulmonary vein. Although all these vessels are chopped down very finely and they are difficult to locate, they are still there.

6. Find the pulmonary artery that leaves the right ventricle. Find the pulmonary veins that enter the left atrium. Circle the correct answer.

Deoxygenated blood leaves the right ventricle in an artery and travels to the lungs. Here, the blood collects oxygen, so it is now oxygenated. The blood travels back to the heart via a vein.

    7. Find the aorta that carries the blood away from the left ventricle of the heart.

    a. Describe the thickness of this vessel. Why do you think it needs to be so thick?

The aorta is wide and thick. It needs to be thick and muscular to be able to contract and force highly energised and oxygenated blood cells through.

b. Where is it taking blood to?

The aorta takes the blood to first the brain and then to the rest of the body, including your organs such as the kidneys, liver and stomach.

Inside one of the major blood vessels, the aorta

    8. Find the vena cava. This is the vein that returns blood away from the body.

    a. Compare the thickness of the vena cava to the aorta. Why do you think it is different?

The vena cava is thinner than the aorta because it doesn’t have to withstand the pressure of the heartbeat, and therefore does not need to contract as rapidly.

b. What part of the heart does the vena cava go back into?

The vena cava enters into the right atrium.

c. Remember what you observed the water flowing through the heart. The water went into the vena cava and into the heart. Which blood vessel did the water come out of the heart from?

Although we didn't do this demonstration, from what I already know, I can conclude that the water would have come out of the pulmonary artery when entering the heart through the vena cava.

The vena cava is shown, but it is slashed

    9. When the water was flowing into the pulmonary vein, which vessel did it come out of?

    The water would have come out of the aorta if demonstrated, because the pulmonary vein enters the left atrium and then moves to the left ventricle, which then sprouts off to the aorta.

Internal Examination

Firstly cut open the LEFT VENTRICLE following the lines on the diagram above.

1. Describe what you see inside the left side of the heart.

Brown/red muscular tissue with lots of arteries and valves inside a narrow cavity was visible inside the ventricle. You can also see the septum in the centre and some valves.

2. Observe any valves you see. What do you think their job would be?

To open and close to stop the blood flowing in the wrong direction, as it is not as energised as the oxygenated blood.

3. Cut the aorta. Describe how it appears and how it feels and any other features.

Has a thick, muscular wall and is quite a large space. Not much was visible, as the top had been cut off very short.

4. Fill out the table below;

1. In the table below, indicate the location and role of the following structures;

'Walking the Heart' activity discussion

The ‘Walking the Heart’ explains the path that blood takes in a more creative way. Starting from the right atrium, the blood is deoxygenated, and travels to the right ventricle to then go down the pulmonary artery. This artery goes to the lungs to collect oxygen, and travels back to the heart through the pulmonary vein. The blood is now oxygenated, and enters the left atrium, where it goes to the left ventricle and out of the heart in the aorta. The aorta travels around the whole body, giving oxygenated blood to organs including the brain, liver, stomach and kidneys. Once the oxygen has been used, the blood travels back to the heart for more oxygen through the vena cava, which enters the heart through the right atrium, and the process begins again.

Our Walking the Heart diagram, made from sports equipment

The Respiratory System

The PLuck Demonstration

The pluck demo showed air entering the lungs and the lungs expanding.

The air enters the body through the nasal passage or the mouth, and then goes down the pharynx (throat). It then goes down the trachea (windpipe) and into the lungs, through the bronchi and bronchiole, then to the alveoli. The alveoli are small air sacs at the end of the bronchiole and are circular to increase surface area. The alveoli are surrounded by capillaries that collect oxygen for the heart, in the process of gas exchange, which happens by diffusion in the lungs.

Full photo of the pluck

The trachea is made of very strong cartilage, and has solid rings of cartilage on the exterior, which holds the trachea open to enable air to pass through. It feels “like a spring inside a thin plastic water-bottle” to the girls who felt it. It runs from the mouth and nasal passage, through the pharynx and the larynx, and finishes in the lungs.

The trachea

The lungs were a dull red colour, and had fat on and around them. They felt like sponge cakes, and were spongy and soft. Inside the lungs there are the bronchi, bronchiole and the alveoli, which all are deoxygenated in this circumstance. The bronchioles hold the lungs open, and are not spongy and soft, but harder to support the lung. The bronchioles are made of cartilage and allow oxygen to enter the lungs right to the maximum amount.

The two lungs

The liver and heart were part of the pluck, and it showed the pulmonary artery connecting the heart and lungs together.

Part of the diaphragm was also visible, and was a very small, thin band of muscle around the lungs. We could see the gall bladder as well, which was a small organ that was connected to the liver through muscle. The gall bladder stores bile, which breaks down fats.

When pumping air into the lungs through a tube, the lungs expanded and gradually became a brighter red. This occurred because the lungs were oxygenated, and had some air circulating through them. Pumping air into the lungs showed that they were very expandable and elastic, allowing for lots of air to enter them. When the alveoli are filled with air, they puff up, and that expands the lungs and fills them with air.

Conclusion

The skeletal and muscular systems are essential for movement of the body. This is best shown in the chicken wing dissection prac, where we could easily see the tendons and ligaments joining the muscles and bones together. When stripping the chicken wing down to just the bones, we could see the joints and how they worked, and where the muscles would be if they were still there. It was also easy to see the connections from the muscles to the bones, and when moving the muscles up and down, you could see the tendons moving along the bone, allowed contraction and expansion.

The circulatory and respiratory systems are necessary for survival, as they provide the body with oxygen. The pluck demo showed how the lungs and heart were attached, and how the pulmonary artery and vein went from the heart to the lungs and back. We could see in the pluck demo how the lungs were connected to the trachea and the heart, and where the blood went in the two systems. The circulatory system depends on the respiratory system to supply the heart with oxygen to pump around the body. Without oxygen from the lungs, your heart would not function properly and you would be dead. The oxygen we breathe in is transferred to the blood stream by the heart, and the carbon dioxide is transferred back to the lungs to be breathed out. This is the process of gas exchange, which takes place in the capillaries that surround the alveoli.

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