Bones, Muscles, and Joints (for Teens)
Joints are where two bones meet. Bones are fastened to other bones by long, fibrous straps called ligaments (pronounced: LIG-uh-mentz). Cartilage. (hinge, ball-and-socket, and sliding joints). • Your joints allow your body to move when your muscles contract. The place where two bones meet is called a joint. The core of some small bones is called marrow, it is soft and jellylike. the surfaces of two or more bones meet and articulate with each other.
The bones of kids and young teens are smaller than those of adults and contain "growing zones" called growth plates. These plates consist of columns of multiplying cartilage cells that grow in length, and then change into hard, mineralized bone. These growth plates are easy to spot on an X-ray. Because girls mature at an earlier age than boys, their growth plates change into hard bone at an earlier age. Bone building continues throughout your life, as your body constantly renews and reshapes the bones' living tissue.
Bone contains three types of cells: AHS-tee-uh-blastzwhich make new bone and help repair damage; osteocytes pronounced: AHS-tee-o-klastswhich break down bone and help to sculpt and shape it. Osteoclasts are very active in kids and teens, working on bone as it is remodeled during growth. They also play an important role in the repair of fractures.
Bones are made up of calcium, phosphorus, sodium, and other minerals, as well as the protein collagen. Calcium is needed to make bones hard, which allows them to support your weight.
Bones also store calcium and release some into the bloodstream when it's needed by other parts of the body. The amounts of certain vitamins and minerals that you eat, especially vitamin D and calcium, directly affect how much calcium is stored in the bones. The soft bone marrow inside many of our bones is where most of the blood cells flowing through our bodies are made.
The bone marrow contains stem cells, which produce the body's red blood cells and platelets, and some types of white blood cells. Red blood cells carry oxygen to the body's tissues, and platelets help with blood clotting when someone has a cut or wound.
White blood cells help the body fight infection. Bones are made up of two types of material — compact bone and cancellous bone. Compact bone is the solid, hard outside part of the bone. This type of bone makes up most of the human skeleton. It looks like ivory and is extremely strong. Holes and channels run through it, carrying blood vessels and nerves from the periosteum, the bone's outer membrane.
KAN-suh-lus bone, which looks like a sponge, is inside the compact bone. It is made up of a mesh-like network of tiny pieces of bone called trabeculae pronounced: This is where red and white blood cells are formed in the marrow.
Bones are fastened to other bones by long, fibrous straps called ligaments pronounced: KAR-tul-ija flexible, rubbery substance in our joints, supports bones and protects them where they rub against each other. Bones don't work alone — they need help from the muscles and joints. Muscles pull on the joints, allowing us to move.
They also help the body perform other functions so we can grow and remain strong, such as chewing food and then moving it through the digestive system.
Skeletal System: Bones, Joints, Cartilage, Ligaments, Bursae
The human body has more than muscles. They are connected to bones by tough, cord-like tissues called tendons, which allow the muscles to pull on bones.
If you wiggle your fingers, you can see the tendons on the back of your hand move as they do their work. Humans have three different kinds of muscle: Skeletal muscle is attached to bone, mostly in the legs, arms, abdomen, chest, neck, and face. Skeletal muscles are called striated pronounced: STRY-ay-ted because they are made up of fibers that have horizontal stripes when viewed under a microscope.
These muscles hold the skeleton together, give the body shape, and help it with everyday movements they are known as voluntary muscles because you can control their movement.
They can contract shorten or tighten quickly and powerfully, but they tire easily and have to rest between workouts. Smooth, or involuntary, muscle is also made of fibers, but this type of muscle looks smooth, not striated. Generally, we can't consciously control our smooth muscles; rather, they're controlled by the nervous system automatically which is why they are also called involuntary.
Examples of smooth muscles are the walls of the stomach and intestines, which help break up food and move it through the digestive system. Smooth muscle is also found in the walls of blood vessels, where it squeezes the stream of blood flowing through the vessels to help maintain blood pressure. Smooth muscles take longer to contract than skeletal muscles do, but they can stay contracted for a long time because they don't tire easily.
Joints are the place where two bones meet or connect. by sniper freedycouger on Prezi
KAR-dee-ak muscle is found in the heart. The walls of the heart's chambers are composed almost entirely of muscle fibers. Cardiac muscle is also an involuntary type of muscle.
Its rhythmic, powerful contractions force blood out of the heart as it beats. Muscles and Movement Even when you sit perfectly still, there are muscles throughout your body that are constantly moving. Muscles enable your heart to beat, your chest to rise and fall as you breathe, and your blood vessels to help regulate the pressure and flow of blood through your body.
When we smile and talk, muscles are helping us communicate, and when we exercise, they help us stay physically fit and healthy. The movements your muscles make are coordinated and controlled by the brain and nervous system.
The involuntary muscles are controlled by structures deep within the brain and the upper part of the spinal cord called the brain stem. The voluntary muscles are regulated by the parts of the brain known as the cerebral motor cortex and the cerebellum. When you decide to move, the motor cortex sends an electrical signal through the spinal cord and peripheral nerves to the muscles, causing them to contract.
The motor cortex on the right side of the brain controls the muscles on the left side of the body and vice versa. Sensors in the muscles and joints send messages back through peripheral nerves to tell the cerebellum and other parts of the brain where and how the arm or leg is moving and what position it's in. This feedback results in smooth, coordinated motion. If you want to lift your arm, your brain sends a message to the muscles in your arm and you move it. When you run, the messages to the brain are more involved, because many muscles have to work in rhythm.
- What is the junction of two bones called?
Muscles move body parts by contracting and then relaxing. Your muscles can pull bones, but they can't push them back to their original position. So they work in pairs of flexors and extensors. The flexor contracts to bend a limb at a joint. Then, when you've completed the movement, the flexor relaxes and the extensor contracts to extend or straighten the limb at the same joint: For example, the biceps muscle, in the front of the upper arm, is a flexor, and the triceps, at the back of the upper arm, is an extensor.
When you bend at your elbow, the biceps contracts. Skull facial and cranial bones Hyoid Vertebrae in the spine backbones Ribs Our arms and shoulders hang from the axial skeleton.
Bones, Muscles, and Joints
The Appendicular Skeleton There are bones in the arms, shoulders, hips, and legs. The appendicular skeleton is made up of our limbs or appendages—two arms and two legs—our pelvis and right and left shoulders. Our arms hang from our shoulders and legs attached to our hips. There are about joints in the human body. Joints allow both movement and flexibility. Joints are classified by how much movement they allow—function—or what they are made of—structure.
Joints are usually classified structurally by the tissue that connects them. The tissue could be cartilage, fibrous tissue, synovial fluid, or some combination of the three.
Functionally, joints can be classified by the degree of movement possible, the number of bones involved, and the complexity of the joint. Most body joints allow us to move, and some only allow movement in certain ways. Fixed or immovable joints allow no movement. A dislocated joint happens when the bones of the joint are forced out-of-place, usually while playing sports but can also happen with accidents. There are 3 major functional joints and 3 major types of structural joints.
Very little movement is possible. Examples of fibrous joints are sutures, syndesmoses, and gomphoses. The growth plates of long bones are examples of this type of joint.
They bones are held together in the joint by ligaments lined with synovial membranes which produce the synovial fluid.
These freely moving joints are mostly found in our arms and legs. Synovial joints also include: The articulating surfaces are covered with a layer of hyaline cartilage that cushions and protects the bones.
The synovial membrane defines the boundaries of the joint space—everything outside of the synovial membrane is outside the joint space. The synovial membrane is wrapped by layers of connective tissue that form the joint capsule.
Synovial fluid acts as a lubricant, forms a fluid seal and helps distribute the force placed on the joint. On the outside of the joint capsule are thick strap-like bands, called collateral ligaments. These ligaments direct the force that travels through the joint and keep the joint on track. Outside of these structures are the muscles that travel across the joint. Types of Synovial Joints Synovial Joints of the Skeletal System Based on the type of movement the joint allows and its structure, synovial joints can be put into several categories.
The way they are bound together by the ligaments may not allow movement in all directions. Examples of a gliding joint are the intertarsal and intercarpal joints of the hands and feet.
The action of the hinge joint is like that of a door hinge and motion is limited to bending and straightening. Our elbows and knees are examples of hinge joints.
Pivot joints allow one bone to pivot on the other bone. An example is head of the radius rotates within the groove of the ulna. These joints allow bending, straightening, abduction, adduction and circumduction. An example of condular joints are in the hands. The only saddle joints are in the thumb. The only ball-and-socket joints are the shoulders and hips.