Hello friends! Have you ever wondered why we all have the ability to move? We can write, carry things, walk, and even jump because we have locomotor system. Our body is made up of many skeletons or bones connected by joints. The bones are also attached to the muscles. These muscles move the bones. Therefore, the bones function as a passive means of movement, while the muscles as an active means of movement. The human skeleton consists of a skull, body, and limbs. The skull consists of the cranial bones and facial bones. The skull serves to protect the brain and shape the face, such as the eyes, nose, cheeks, and jaws. The body skeleton consists of the shoulder girdle, spine, ribs, sternum, and pelvis. The shoulder girdle consists of the collarbones and shoulder blades. The spine starts from the neck, back, to the tail. The spine will support the head and support the body posture. The sternum is connected to the ribs, while the ribs are attached to the spine. The sternum and ribs protect the heart and lungs, and play a role in breathing. The pelvis are 3 pairs of bones that are fused together, namely the iliac bones, pubic bones, and sit bones. The pelvis supports the body weight, protects the bladder and uterus in women. The limbs consist of hands and legs. The hand is composed of the bones of the upper arm, the lever and cubit, the bones of the wrist, the palm, and the fingers. While the leg is composed of the femur, kneecap, shin and calf, wrist bones, soles, and toes. There are 3 types of human muscle, namely smooth muscle, cardiac muscle, and skeletal muscle. Smooth muscle is spindle-shaped with a pointed end, and is attached to the respiratory or digestive organs. Cardiac muscle is cylindrical and branched, and is attached to the heart. Smooth muscle and cardiac muscle work involuntarily. The muscles attached to the bones are skeletal muscles. Skeletal muscle is cylindrical in shape with a dark-light patterns. This muscle works voluntarily, meaning that your body moves because you want to move it. When muscles work, they contract or shorten. Conversely, when the muscles do not work, the muscles will relax. Muscles can work antagonistically as in the biceps and triceps. When lifting the forearm, the biceps contract and the triceps relax. Conversely, when the forearm is lowered, the biceps relax and the triceps contract. There are also muscles that work synergistically. For example the pronator muscle for prone motion. Bones can also be moved through the joints. There are many types of joints. This lifting motion of the leg is caused by the hinge joint in the knee that allows movement in one direction. Hinge joints are also present at the elbows and knuckles. Now try moving your thumb like this. Between the palm of the hand and the thumb there is a saddle joint that allows movement in both directions. You can rotate your neck like this because of the swivel joint between the atlas bone and the skull. Or the swivel joint between the ulnar bone and the radius that allows you to turn your palms over. Next, ball joint allows free movements in all directions. The ball joint is located between the shoulder girdle and upper arm, and it allows you to rotate your hand like this. Or between the pelvic girdle and femur. Wow, we can actually exercise while learning about joints! Body posture is influenced by the shape of the bones. Bad posture can cause a stooped, curved forward or sideways shape in the skeletal system. When the bone is being hit hard by an object, the bone might be fractured or broken. We should be grateful that there are organs that allow us to move easily. We should also take care of these organs by maintaining the correct body posture, exercising regularly to strengthen muscles, and eating foods that contain calcium and vitamin D to strengthen our bones. There are 206 human bones. Which part of the bone is the largest and which is the smallest? Please write your answer in the comments column.