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Actions for this page Listen Print. Summary Read the full fact sheet. On this page. The skeleton The human skeleton is made up of bones, including bones of the: Skull — including the jaw bone Spine — cervical, thoracic and lumbar vertebrae, sacrum and tailbone coccyx Chest — ribs and breastbone sternum Arms — shoulder blade scapula , collar bone clavicle , humerus, radius and ulna Hands — wrist bones carpals , metacarpals and phalanges Pelvis — hip bones Legs — thigh bone femur , kneecap patella , shin bone tibia and fibula Feet — tarsals, metatarsals and phalanges.
Bone types There are four different types of bone in the human body: Long bone — has a long, thin shape. Examples include the bones of the arms and legs excluding the wrists, ankles and kneecaps. With the help of muscles, long bones work as levers to permit movement.
Short bone — has a squat, cubed shape. Examples include the bones that make up the wrists and the ankles. Flat bone — has a flattened, broad surface. Examples include ribs, shoulder blades, breast bone and skull bones. Irregular bone — has a shape that does not conform to the above three types. Examples include the bones of the spine vertebrae.
Bone tissue The different layers of bone tissue include: Periosteum — the dense, tough outer shell that contains blood vessels and nerves Compact or dense tissue — the hard, smooth layer that protects the tissue within Spongy or cancellous tissue — the porous, honeycombed material found inside most bones, which allows the bone to be strong yet lightweight Bone marrow — the jelly-like substance found inside the cavities of some bones including the pelvis that produces blood cells.
Bone marrow Bone marrow is where blood cells are made. The three different types of blood cell made by bone marrow include: Red blood cells — carry oxygen around the body. This is where bone marrow is found. How Do Bones Grow? Bone contains three types of cells: osteoblasts AHS-tee-uh-blastz , which make new bone and help repair damage osteocytes AHS-tee-o-sites , mature bone cells which help continue new born formation osteoclasts 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 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 them. They can contract shorten or tighten quickly and powerfully, but they tire easily. Smooth, or involuntary, muscle is also made of fibers, but this type of muscle looks smooth, not striated. We can't consciously control our smooth muscles; rather, they're controlled by the nervous system automatically which is why they're 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. Cardiac 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. How Do Muscles Work? Joints are classified by their range of movement: Immovable, or fibrous, joints don't move.
The dome of the skull, for example, is made of bony plates, which move slightly during birth and then fuse together as the skull finishes growing. Between the edges of these plates are links, or joints, of fibrous tissue.
Fibrous joints also hold the teeth in the jawbone. Partially movable, or cartilaginous kar-tuh-LAH-juh-nus , joints move a little. They are linked by cartilage, as in the spine.
Each of the vertebrae in the spine moves in relation to the one above and below it, and together these movements give the spine its flexibility. Freely movable, or synovial sih-NO-vee-ul , joints move in many directions. The main joints of the body — such as those found at the hip, shoulders, elbows, knees, wrists, and ankles — are freely movable.
They are filled with synovial fluid, which acts as a lubricant to help the joints move easily. Three kinds of freely movable joints play a big part in voluntary movement: Hinge joints allow movement in one direction, as seen in the knees and elbows.
This is shown in the animation below. However, whereas HA as has a Ca:P ratio of 1. This is because the composition of bone mineral is much more complex and contains additional ions such as silicon, carbonate and zinc. Cartilage is a collagen-based tissue containing very large protein-polysaccharide molecules that form a gel in which the collagen fibres are entangled.
Articular, or hyaline, cartilage forms the bearing surfaces of the movable joints of the body. Mechanically, articular cartilage behaves as a linear viscoelastic solid. Bones such as the femur are subjected to a bending moment, and the stresses both tensile and compressive generated by this bending moment account for the structure and distribution of cancellous and cortical bone. In the upper section of the femur, the cancellous bone is composed of two distinct systems of trabeculae.
One system follows curved paths from the inner side of the shaft and radiates outwards to the opposite side of the bones, following the lines of maximum compressive stress.
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