Synovial fluid is made by the synovial membrane. In synovial joints, the ends of the bones are covered with cartilage called articular cartilage which cushions the joint and prevents friction and wear and tear between the bone ends. Cartilage is a soft, spongy connective tissue. The articular capsule prevents wear and tear on the bones. The bones in a synovial joint are connected by ligaments.
The movement at a synovial joint is caused by the muscles attached across the joint. Muscles are attached to bone by tendons. Tendons are very strong, inelastic connective tissues that allow a muscle to pull on a bone to move it. Different types of synovial joints allow varying degrees of movement. Joints are the areas where 2 or more bones meet.
Most joints are mobile, allowing the bones to move. Joints consist of the following:. This is a type of tissue that covers the surface of a bone at a joint. Cartilage helps reduce the friction of movement within a joint. Synovial membrane. A tissue called the synovial membrane lines the joint and seals it into a joint capsule.
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. Muscles move body parts by contracting and then relaxing. Muscles can pull bones, but they can't push them back to the original position. So they work in pairs of flexors and extensors. The flexor contracts to bend a limb at a joint.
Then, when the movement is completed, 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. Then the biceps relaxes and the triceps contracts to straighten the elbow.
Joints are where two bones meet. They make the skeleton flexible — without them, movement would be impossible. Joints allow our bodies to move in many ways.
Some joints open and close like a hinge such as knees and elbows , whereas others allow for more complicated movement — a shoulder or hip joint, for example, allows for backward, forward, sideways, and rotating movement. Reviewed by: KidsHealth Medical Experts. Larger text size Large text size Regular text size. Bones are made up of two types of bone tissues: Compact bone is the solid, hard outside part of the bone.
It looks like ivory and is extremely strong. Holes and channels run through it, carrying blood vessels and nerves. Cancellous pronounced: KAN-suh-lus bone , which looks like a sponge, is inside compact bone.
It is made up of a mesh-like network of tiny pieces of bone called trabeculae pronounced: truh-BEH-kyoo-lee. This is where bone marrow is found. How Do Bones Grow? Bone contains three types of cells: osteoblasts pronounced: AHS-tee-uh-blastz , which make new bone and help repair damage osteocytes pronounced: AHS-tee-o-sites , mature bone cells which help continue new born formation osteoclasts pronounced: AHS-tee-o-klasts , which break down bone and help to sculpt and shape it What Are Muscles and What Do They Do?
Humans have three different kinds of muscle: Skeletal muscle is attached by cord-like tendons to bone, such as in the legs, arms, 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 help hold the skeleton together, give the body shape, and help it with everyday movements known as voluntary muscles because you can control their movement.
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