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why do we need the skeletal system

What is the purpose and structure of the skeleton? 1. Supports and protects the softer parts of the body (the very important organs! )P
The brain is protected by the skull. The heart and lungs are protected by a strong rib cage. It is also protected by the breast bone (sternum) at the front and vertebral spinal column at the back. The spinal cord is protected by the vertebrae (bones of the spine). The intestines and reproductive organs are protected by the pelvis. 2. Supports our body through a framework of bones. Bones are not solid. The hard outer layer of the bone protects the light, porous (not solid) bone inside. This porous bone contains the marrow, which is the factory where red blood cells are produced a process called haematopoiesis. Red blood cells carry oxygen around the body, providing energy for our muscles. However, before we are born, all of our bones begin as a rubbery material called cartilage. As we grow, more and more deposits of calcium are laid down which change some of the cartilage into a more solid and rigid mass bone. act as an anchor for muscles which together, along with other soft tissues, make the body move. contain calcium and other minerals which make them hard (rigid) and provide strength. supply the body with calcium when the diet is calcium deficient. 3.

Prevents the body from losing its shape. P 4. Suspends some of the vital organs, preventing them from crushing each other. 5. Helps keep the calcium levels in the blood constant. Calcium is essential for the functioning of all the cells in the body, in particular the bones, brain and muscles. Without enough calcium, these cells do not operate properly. The body needs a constant level of calcium. If there is not enough calcium in the blood then cells called osteoclasts dissolve calcium from the bones. The appendicular skeleton refers to your arms and legs. It is called appendicular, from append because they are attached by girdles, which bridge each with the main body. How do our bones move? Bones cannot move without muscles. Most muscles (like those in our arms and legs) work in pairs one muscle contracts as the other one relaxes. The bone is pulled towards the contracted muscle. Muscles are attached to bone by tendons. How are bones joined together? The place where two or more bones meet is called a joint.

P Some joints are fixed as in the skull, but others can move such as where the bones in the leg meet. (See Joints. )P At these joints, ligaments hold the bones together. Can bones bend? Bones in the body do not bend but break when abnormal pressure is placed on them. There is an exception to this and that is in a small child, called a greenstick fracture because it looks like a green rather than dry stick has tried to be broken. The process through which bone grows in the body is called ossification. Bones, in particular long bones, have cartilaginous growth plates located at either end called epiphyseal plates. Initially, these plates are not completely hardened and are where growth occurs in the bone. These fragile growth plates can be damaged in growing children or teens and affect bone development. As a person matures, the epiphyseal plates harden, and growth stops between the ages of 21 and 25. Children have large amounts of organic material in their bones, making their bones softer and more pliable. As we age, we have larger proportions of inorganic material, which causes bones to become brittle and more fragile. The structures in bones are in a continuous state of being built up and broken down.

When exercise is combined with adequate rest and nutrition, healthy bones become thicker and stronger. Exercise helps build and promote healthy bone tissue and reduces the risk of bone disease such as osteoporosis. The human skeleton consists of 206 bones and is divided into two parts: the axial skeleton and the appendicular skeleton. The axial skeleton consists of the bones found around the axis (the imaginary midline of the body) and includes the skull, vertebral column, sternum, and ribs. The appendicular skeleton refers to the bones associated with the appendages and includes the bones in the arms, shoulders, legs, and hips (figure 2. 3). An articulation (joint) is the point of contact between bones or cartilage and bones. Joints are classified as immovable, slightly movable, or freely movable. The amount of movement possible at a joint depends on the way in which the bones fit together, the tightness of the tissue that surrounds the joints and the position of ligaments, muscles, and tendons. Ligaments are dense, regular, connective tissue that attach bone to bone at movable joints and help to protect the joint from dislocation.

The vertebral column, or backbone of the human skeleton, is typically made up of 26 bones called vertebrae (figure 2. 4 on page 22). These vertebrae are divided into five sections. The part of the vertebral column found in the neck is called the cervical spine and contains seven smaller vertebrae. The part of the vertebral column found behind the rib cage is called the thoracic spine and consists of 12 midsized vertebrae. The lower back area of the vertebral column is called the lumbar spine and consists of five large vertebrae. Below the lumbar spine is the sacrum, which is one bone made up of five fused sacral vertebrae. The coccyx, or tailbone, is made up of four vertebrae fused into one or two bones. A fibrocartilaginous tissue, called an intervertebral disc, is found between each vertebra. This tissue can be injured through trauma or overuse, especially in the weight-bearing lumbar area or in the delicate cervical area of the spine. Disc problems are not as common in the thoracic area because of the support and stability the ribs provide the vertebral column in this region. This is an excerpt from.

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