PART 1 – BONES, MUSCLES, AND SKIN THE AMAZING HUMAN BODY

-YOUR SKELETON- You have an endoskeleton, meaning your skeleton is inside your body. Your skeleton is made of 206 bones. Bones have 5 major functions in the human body: 1) Bones help you keep your shape. Without them, you’d be a blob of stuff on the floor! 2) Muscles work because they are attached to a bone. (We will get into how muscles work in a few slides.) 3) Bones protect vital organs, like your head and lungs, from damage. 4)Inside bone marrow is where red blood cells are produced. 5)Bones are like a warehouse for important minerals like calcium, magnesium, and phosphorus.

-BONES ARE ALIVE!- Bones are made of layers of living tissue. Each layer has a job it performs to keep your bones healthy. The periosteum is a thin, tough, tight covering on your bones. Within this covering, new bone is being shaped and produced by osteoblasts – the bone producing cells. Osteoblasts create new bone tissue around themselves until they are completely encased in bone tissue, where they become bone cells themselves and are then called osteocytes (or bone cells). Compact bone is the layer of new bone created by the osteoblast. It is tough and hard, and just a little bit flexible. The spongy bone is the layer within the casing of the compact bone. The spongy bone is made of red and yellow marrow. Red marrow creates red blood cells which carry oxygen and remove waste products for cells throughout your body. Yellow marrow is mainly fat stores that can be converted back to red marrow when necessary.

-BONES – A GROWTH SYSTEM- Within the layers of bone you will find an amazing system of blood vessels and nerves. Bones contain a system of blood vessels bringing nutrients to the working bones and allowing the bones to share their nutrients with the rest of the body. Nerves allow the bones to “feel” and are the communication system of the body. Between bone cells is an amazing communication system of nerves! Bones are constantly forming and re-forming. Osteoblasts create new bone tissue, while osteoclasts break bone tissue down to release the calcium, magnesium, and phosphorus stored within them. The cartilage, or flexible bone, you start life with as a baby is replaced by bone as you age. Osteoclasts break down the cartilage from the inside and osteoblasts re-build it as bone.

-JOINTS – MOVING AND NOT- Joints are any area where two bones come together. There are two types of joints in the human body. Movable joints include any area where bones rub together to help you move and include: Pivot joints –arm and wrist joints that twist Gliding joints – vertebrae in your back that allow you to bend Ball-and-Socket joints – shoulders and hips that move in circles Hinge joints – knees and elbows that bend only one way Immovable joints are just that, immovable. They include the suture joints in the skull where the bones were not joined when you were very young The pelvic floor where the bones are not joined but come together to give support and protection. Cartilage is an important component in joints as it cushions the ends of bones and protects them from wear. Ligaments connect bones together at joints. A ligament is a strong connective tissue holding bones together like a strong rubber band.

-CARING FOR YOUR BONES- Getting enough calcium, magnesium, and phosphorus now will help ensure a good supply of these important minerals when you are an adult. Eating calcium-rich foods (dairy products, many dark leafy greens, soybeans, and calcium-enriched juices) helps you get your minimum daily supply of 1300mg of calcium. Exercise is another important part of bone care. Without the stress of exercise on your bones, they become brittle and weak. Regular stress on your bones from walking, running, jumping, pulling, and lifting causes your body to build more bone tissue. Joints are also strengthened by exercise. Joints that are not exercised regularly can become stiff and difficult to move. Even the swelling in the joints of people with osteoarthritis and rheumatoid arthritis can be decreased with exercise.

BONE STRUCTURE VISUAL Image courtesy of encyclopedia.lubopitko-bg.com encyclopedia.lubopitko-bg.com Image courtesy of

-REVIEW- Explain the 5 purposes of the skeletal system. Describe the structure of a bone from the outside to the inside. Name what happens in each layer of bone. Name the bone forming and bone break-down cells. Name the two types of joints and describe each of them. Explain why cartilage is important for joints. Draw your own image of a long bone with all the parts labeled.

THE MUSCULAR SYSTEM Muscles are organs that contract and relax to provide the force necessary to move body parts. Muscles are grouped into two major categories: Voluntary Muscles Muscles you control with thought Skeletal muscles fall into this category Involuntary Muscles Muscles you can’t consciously control Cardiac muscle and the smooth muscles of your intestines, bladder, blood vessels, and internal organs fall into this category

VOLUNTARY MUSCLES Voluntary muscles are controlled by your thoughts. All skeletal muscles are voluntary. Skeletal muscles are attached to bones by thick tissues called tendons. Skeletal muscles are striated muscles meaning when they are viewed under a microscope, you can see stripes in the muscle fibers.

INVOLUNTARY MUSCLES There are two types of involuntary muscles in your body: Cardiac The cardiac muscle is a very strong muscle and is striated, like the skeletal muscles. The cardiac muscle contracts quickly or slowly, depending on your activity level. The rate of this activity is known as your heart rate. Smooth Smooth muscles are not striated and are found in your internal organs. These muscles contract and relax very slowly.

THE HUMAN MACHINE The body uses bones, joints, and muscles as levers to do work. Levers are simple machines that make work easier. Levers are classified into three groups: First –class: A first-class lever uses a fulcrum, or balance point, in the center with a weight or object being moved at one end and the force at the other. Second-class: A second-class lever uses a fulcrum at one end, the force at the other end, and the weight or object being moved in the middle. Third-class: A third-class lever uses a fulcrum on on one end, the weight on the other end, and the force in the middle.

MUSCLE WORKS Muscles always work in pairs. When one muscle contracts, another relaxes. A contracted muscle is shortened. A relaxed muscle is lengthened. This constant combination of pull and push from your muscles allows all your movement. Using muscles causes muscle cells to enlarge and creates stronger muscles. The energy for muscle use comes from stored chemicals in your body. These stored chemicals are released as mechanical energy and thermal energy…movement and heat.

REVIEW Explain the activity of muscles. Describe the difference between the two major types of muscles. Compare and contrast the three classifications of muscles and name where each would be found. Describe the type of muscle found in your heart. Describe how a muscle is attached to a bone. Explain how muscles work to allow movement.