Unit 4 Physical Fitness
Bones and Muscles by Microbiology Doctor-dr
Bones are organs that are alive. If you've ever seen bones at the dinner table, you might find this hard to believe. They're made up of cells that can mend, grow, and replenish themselves. Minerals, which are nonliving things, are also found in bones. The human skeleton's bones vary in size and shape, yet they all serve the same job. Bones provide structure, protect internal organs, and provide vital minerals to the body. Minerals are stored in bones until they are needed by other areas of the body. They also house the tissues responsible for the production of blood cells.
Structure of Bone
Figure 11-1 depicts the structure of the type of bone found in your thigh or upper arm. A long bone is a type of bone that has broad ends and a narrow centre. The shaft is the narrow part of the bone between the bone ends.
A robust membrane surrounds the outside of the bone. The periosteum is also known as the periosteum [per ee AHS tee uhm]. Figure 11-1 shows the periosteum, which covers the whole bone except for the ends. The periosteum's blood arteries penetrate the bone at a number of locations, supplying the bone's cells.
A layer of tissue called compact bone lies beneath the periosteum. Bone that is compact is difficult to break. The compact bone thickens as the bone grows larger. The entire bone is covered in compact bone. In the layer of compact bone, a network of blood arteries runs through canals. The Haversian system is the name given to this canal system.
Take another look at Figure 11-1. It's worth noting that the ends of the bone are made up of spongy bone. Many cavity connections are formed by the cells of spongy bone. These chambers are arranged in such a way that they can support a lot of weight. By absorbing shocks, the spongy bone acts as a cushion for the remainder of the bone. Red bone marrow is found in the spongey bone. The red bone marrow is a tissue that produces red and white blood cells. Every minute, your body produces millions of blood cells.
There is no red bone marrow beneath the compact bone in the shaft of an adult. Yellow bone marrow, on the other hand, fills a cavity that runs the length of the shaft. Fat cells make up the majority of yellow bone marrow. However, in rare situations, such as after extensive bleeding, yellow bone marrow can produce blood cells.
Bones contain more nonliving stuff than living material in adults. Figure 11-2 depicts the arrangement of materials in bone. Calcium and phosphorus minerals are used to make the rings. Collagen, a strong, flexible substance produced by bone cells, holds minerals together. Bone is made up of minerals that give it its strength. The rings' lighter-colored centre is made up of blood vessels and nerves. Living bone cells fill the dark regions between the mineral rings.
Figure 11-1 Structure of a long bone. The wedge is taken from the bone shaft below.
How Bones Change
Bones change as we become older. The majority of a baby's bones are cartilage. Cartilage, which is primarily composed of collagen, is tough and bendable. Babies and children's bones bend easily and rarely shatter. This is a good thing, because toddlers are prone to falling. Cartilage cells are replaced by bone cells and calcium and phosphate rings between bone cells as a newborn grows. Ossification [lahs uh fih KAY shun] is the transformation of cartilage into bone cells and minerals. Ossification occurs throughout childhood and into early adulthood. Your bones become heavier and harder as you get older, but they also become less flexible. This means they're strong, but they're also more prone to breaking.
Adults lose minerals and living materials from their bones as they age. The bones become weaker and more brittle as time goes on. The elderly are more likely than the middle-aged to suffer from shattered bones. Their bodies also have a harder time healing breaks. Activity, on the other hand, strengthens bones. Exercise helps the formation of thicker layers of compact bone and heavier mineral deposits in the bones.
Osteoporosis is a bone disease that affects some people.
The loss of calcium from bone is known as osteoporosis [ahs tee oh puh ROH suhs]. The bloodstream re-absorbs the calcium. This weakens the bone, making it more susceptible to fracture. Exercise and a healthy, long-term diet rich in calcium and vitamin D may help to avoid osteoporosis.
Review of the Lesson
Bones provide a living framework for bodies that changes over time. The cartilage in children's skeletons is replaced by bone as they grow, a process known as ossification. The periosteum, compact bone, spongy bone, and bone marrow are all layers of tissue found within bones. Bone health is aided by exercise and a well-balanced diet rich in calcium and vitamin D.
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