Provide structural support for the body Provide protection of vital organs Provide an environment for marrow where blood cells are produced Act as a storage area for minerals such as calcium. Bones are made of two tissue types:. Compact bone: also known as cortical bone, this hard-outer layer is strong and dense Cancellous bone: also known as trabecular bone, this spongy inner layer network of trabeculae is lighter and less dense than cortical bone. Bones are composed of:.
Osteoblasts and Osteocytes: these are bone forming cells Osteoclasts: these are bone resorbing cells Osteoid: this is the non-mineral, organic part of the bone matrix made of collagen and non-collagenous proteins Inorganic mineral salts deposited within the matrix. Bone Cells. Cells in our bones are responsible for bone formation, resorption, maintenance and re- modelling: Osteoblasts: These cells are derived from mesenchymal stem cells and are responsible for bone matrix synthesis and its subsequent mineralization.
In the adult skeleton, the majority of bone surfaces that are not undergoing formation or resorption i. Osteocytes: These cells are osteoblasts that become incorporated within the newly formed osteoid, which eventually becomes calcified bone.
Osteocytes situated deep in bone matrix maintain contact with newly incorporated osteocytes in osteoid, and with osteoblasts and bone lining cells on the bone surfaces, through an extensive network of cell processes canaliculi.
They are thought to be ideally situated to respond to changes in physical forces upon bone and to transduce messages to cells on the bone surface, directing them to initiate formation or resorption responses.
You can feel your skull by pushing on your head, especially in the back a few inches above your neck. The skull is actually made up of different bones.
Some of these bones protect your brain, whereas others make up the structure of your face. If you touch beneath your eyes, you can feel the ridge of the bone that forms the hole where your eye sits. And although you can't see it, the smallest bone in your whole body is in your head, too. The stirrup bone behind your eardrum is only. Want to know something else? Your lower jawbone is the only bone in your head you can move. It opens and closes to let you talk and chew food. Your skull is pretty cool, but it's changed since you were a baby.
All babies are born with spaces between the bones in their skulls. This allows the bones to move, close up, and even overlap as the baby goes through the birth canal. As the baby grows, the space between the bones slowly closes up and disappears, and special joints called sutures say: SOO-churs connect the bones.
As you sit and type at the keyboard, while you swing on a swing, even when you pick up your lunch, you're using the bones in your fingers, hand, wrist, and arm. Each arm is attached to a shoulder blade or scapula say: SKA-pyuh-luh , a large triangular bone on the upper back corner of each side of the ribcage. The arm is made up of three bones: the humerus say: HYOO-muh-rus , which is above your elbow, and the radius say: RAY-dee-us and ulna say: UL-nuh , which are below the elbow.
Each of these bones is wider at the ends and skinnier in the middle, to help give it strength where it meets another bone. At the end of the radius and ulna are eight smaller bones that make up your wrist. Although these bones are small, they can really move! Twist your wrist around or wave and you'll see how the wrist can move.
The center part of your hand is made up of five separate bones. Each finger on your hand has three bones, except for your thumb, which has two. So between your wrists, hands, and all your fingers, you've got a grand total of 54 bones — all ready to help you grasp things, write your name, pick up the phone, or throw a softball!
Sure, your arm, wrist, hand, and finger bones are great for picking up the phone, but how are you supposed to run to answer it? Well, with the bones of the legs and feet! Your legs are attached to a circular group of bones called your pelvis. The pelvis is a bowl-shaped structure that supports the spine. It is made up of the two large hip bones in front, and behind are the sacrum and the coccyx. The pelvis acts as a tough ring of protection around parts of the digestive system, parts of the urinary system, and parts of the reproductive system.
Your leg bones are very large and strong to help support the weight of your body. The bone that goes from your pelvis to your knee is called the femur say: FEE-mur , and it's the longest bone in your body. At the knee, there's a triangular-shaped bone called the patella say: puh-TEL-luh , or kneecap, that protects the knee joint. Just like the three bones in the arm, the three bones in the leg are wider at the ends than in the middle to give them strength. The ankle is a bit different from the wrist; it is where the lower leg bones connect to a large bone in the foot called the talus say: TAL-iss.
Next to the talus are six other bones. But the main part of the foot is similar to the hand, with five bones. Produced by the ovaries, estrogen has been shown to have a protective effect on bone. Women usually go through menopause between age 45 and After menopause, bone loss in women greatly exceeds that in men. However, by age 65, women and men tend to lose bone tissue at the same rate. Although men do not undergo the equivalent of menopause, production of the male hormone testosterone may decrease, and this can lead to increased bone loss and a greater risk of developing osteoporosis.
Osteoporosis is preventable for many people. Prevention is important because although there are treatments for osteoporosis, a cure has not yet been found. A comprehensive program that can help prevent osteoporosis includes:. This type of cell is within the bone. It helps to maintain bone as living tissue. This type of cell is found in bone marrow. Its function is to make red blood cells, white blood cells, and platelets. Search Encyclopedia.
Understanding Bones What are bones? There are 3 types of bone tissue: Compact tissue. This is the harder, outer tissue of bones. Cancellous tissue. This is the sponge-like tissue inside bones.
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