Your body moves when muscles pull on the bones through ligaments and tendons. Ligaments attach the bones to other bones, and the tendons attach the bones to the muscles.
If you place your relaxed arm on a table, palm-side up, you can get the fingers to move by pushing on the tendons below your wrist. We’re going to make a real working model of your hand, complete with the tendons that move the fingers! Are you ready?
Did you know that the patterns on the tips of your fingers are unique? It’s true! Just like no two snowflakes are alike, no two people have the same set of fingerprints. In this experiment, you will be using a chemical reaction to generate your own set of blood-red prints.
In addition to looking pretty neat with all those loops and whirls, your fingertips are great at multitasking. The skin on them has a ton of receptors that help us to gather a lot of information about our environment such as texture, movement, pressure, and temperature.
This experiment will test your ability to determine textures by using touch receptors. You will use shoeboxes with holes cut into them to make texture boxes. Each box will have a textured surface that you can feel, but not see. Through the receptors in your fingers, you will determine whether the surface is rough, waxy, soft, or smooth.
This experiment has two parts. For the first half, you will mix two chemicals that will produce heat and gas. The temperature receptors in your skin will be able to detect the heat. Your ears will detect the gas at it vibrates and escapes its container.
In the second portion you will demonstrate a characteristic in a chemical reaction. For this experiment, it will be an endothermic reaction, which is the absorption of heat energy. This type of reaction is easy to notice because it makes things cold to touch. The chemical you will be using, ammonium nitrate, is actually used in emergency cold packs.
Skin has another function that it vital to your survival: temperature regulation. Being exposed to high temperatures causes your skin’s pores to open up and release sweat onto your body. This helps cool us off by the resulting process of evaporation.
Your pores will close in extremely cold temperatures. Also, the body stops blood flowing to the skin in order to conserve heat for the important vital organs and their processes.
In this lab, we study the moisture that your skin produces – even when you are not aware of it!
Your fingers have receptors which perform various jobs. In addition to touch, they can detect pressure, texture, and other physical stimuli. One specialized type of receptors is called Ruffini’s receptors. They are good at identifying changes in pressure and temperature. In this experiment, we will test their ability to distinguish between hot and cold temperatures. We are actually going to try and trick your Ruffini endings. Do you think it will work?
Some groups of muscles are stronger than others because each group is designed for a different and specific function. It just makes sense that the muscle groups in our legs would need to be stronger than the ones in our toes.
For this experiment, you will use a bathroom scale to test the strength of various muscle groups.
The skeleton is your body’s internal supporting structure. It holds everything together. In addition to providing support, bones act as shock absorbers when you jump, fall, and run. Bones have big responsibilities and so they must be really strong. They also need to be arranged properly for the best support and shock absorption.
In this experiment, we will look at the internal arrangement of the bones holding together your body.
Bones are made up of several parts; bone marrow (red and yellow), spongy bone, compact bone, and the periosteum. Bone marrow makes blood cells. Red blood cells are made in the red marrow, while white blood cells are made in the yellow marrow. When babies are born they only have red marrow. Spongy bone is a light, spongy type of bone found inside bones. Compact bone, on the other hand, is hard and makes up the outer layer of bones. The compact bone layer is covered by a thin white membrane called the periosteum.
Bones begin growing very early, and stop growing between the ages of 18-25. At about eight weeks of development, we form a skeleton of cartilage and other connective tissues. As we grow up, the cartilage becomes bone. Normally, we have all of our bones by our early twenties. We still keep some of the cartilage in areas like our nose and ears.
Joints are essential in how we move. Bones work as levers and the joints work as the fulcrums—making our movement easier. Some joints are fixed; for example, many in the skull. Some allow only little movement; for example, the vertebrae which make up the backbone. Lastly, there are movable joints; for example, our knees and elbows. These make up the three classes of joints: fixed joints, partly movable joints, and movable joints.
The keys to keeping the skeletal system healthy are: eating well, getting exercise, and taking care of injuries to the skeletal system.
Eating a good balanced diet is very important for overall health, but making sure to get specific nutrients help ensure a healthy skeletal system throughout your life! Those nutrients are: calcium and vitamin D. 1300mg of Calcium is recommended (one cup of milk has about 300mg of Calcium) and 200IU of vitamin D (31/2 ounces of cooked salmon is about 360IU of vitamin D). Calcium can be found in dairy products as well as broccoli and cabbage. Your skin makes vitamin D when exposed to sunlight. Additionally, fish is rich in vitamin D.
It’s important to get out an exercise to maintain a healthy skeletal system. When we exercise we put stress on our bones and stimulate them to stay strong. Exercising also keeps the muscles which work with the bones strong. Just remember to stretch and wear all the appropriate safety gear.
Lastly, if an injury occurs—a bone breaks or a ligament tears, for example—it’s important to see a medical professional as soon as possible. Otherwise, the skeletal system may not heal properly!
Involuntary responses are ones that you can’t control, but they are usually in place to help with survival. One good example is when you touch something hot. Your hand does not take the time to send a message to your brain and then have the brain tell your hand to pull away. By then, your hand might be seriously hurt! Instead, your body immediately removes your hand in order to protect it from further harm.
Today you will test an involuntary reflex by using the tendon reflex test. A thick, rubbery band called the patellar tendon holds your knee cap in place. Having one leg on top of the other not only stretches the tendon, but it also makes it possible to see a reaction. You can test the reflex by giving your tendon a tap and watching what happens.
The buildup of things like food and bacteria where your gums and teeth meet, and also between your teeth, is called plaque. Where plaque lives is also where the bacteria turns the sugar in your mouth into harmful acids that attack your teeth’s enamel and can lead to gum disease. Regular brushing is a great way to remove plaque and keep your mouth healthy.
Digestion involves the breakdown of what we consume into nutrients. The first step is mechanical digestion—chewing. After we mechanically break down the food with our teeth, we begin chemical digestion.
Teeth are small structures found in the mouths of vertebrates. They are calcified, meaning that they contain the element calcium, and are very distinctive based on the type of animal they are found in. Carnivores, or animals that eat meat, have sharp, pointy teeth for ripping and tearing prey. Plant-eating animals, known as herbivores, have larger flat teeth which they use to grind up the tough plant material they eat. Other animals, referred to as omnivores or generalists, eat both plant and animal material. As you might expect, these animals have both types of teeth. Humans fall into this category.
Humans and all other mammals are diphyodont, meaning we will have two sets of teeth in our lifetimes. Not all animals are this way. In fact, rodents and sharks both will continue to grow set after set of new teeth as they gnaw or bite their food. Other animals only have one set of teeth throughout their entire life.
In humans, the front teeth are called incisors. Next to the incisors are the sharp canines. To see how these two types of teeth are used, try a mini-experiment. Take a bite out of a banana and then take a bite of a carrot. Chew them as you would normally, and pay careful attention to what tooth is being used to chew. You’ll notice that for the softer banana, the incisors take the first bites. With the harder carrot, the canines do this job. In both cases, the chewing is done by the pre-molars, which are the teeth next to the canines, and the molars, the large, flat teeth closest to the back of your mouth.
Taking care of your teeth is very important. Brushing your teeth after every meal and flossing every day can go a long way in making sure your teeth stay healthy. If you don’t brush and floss, bacteria can build up over time, leading tartar and plaque on your teeth. If this continues, a small hole, or cavity, can form. Dentists can fill cavities, but this is generally something to be avoided if possible. Your gums can also become infected with bacteria if they are not cleaned. Bleeding gums can be one sign of gum disease. Serious dental procedures, such as extraction (the removal of a tooth) or a root canal are sometimes needed when dental care has been ignored for too long. The best thing to do is to avoid the problem to begin with by brushing, flossing, and visiting a dentist regularly.
The muscles in your body allow you to move. In this lab we will do two quick experiments to explore how your muscles work.