Bones

A long bone is a bone that is narrow and long, with two ends. The shaft is the long, central section of a long bone; it is also known as the diaphysis. Most of the bones found in the arms and legs are long bones. A short bone is a bone that is cube-shaped. The height, width, and length of short bones are approximately equal. These bones are found mostly in the wrists and ankle.

A flat bone is a bone that has a thin, flattened shape. It is typically curved. The ribs and most of the bones of the skull are flat bones. An irregular bone is a bone that is neither long, short, nor flat, but often has a complex shapes. The bones that make up the spine and the hips are examples of irregular bones.

Only a portion of the bone is made of cells. The rest of the bone is composed of bone matrix. Bone matrix is a mixture of fibers, minerals, and other substances in which bone cells are embedded

About 60 percent of bone mass is made of minerals. The minerals that make up bone are rich in the elements calcium and phosphorous. These minerals give bone its hardness and durability. Even after the living tissue dies, the minerals remain. Bones can be studied thousands of years after a person has died.

Bone is a living tissue that constantly remodels itself during a person's lifetime. Bone gets stronger in response to stress put on the bone, such as weight-bearing exercise like running and weightlifting. Osteoblasts build more bone in areas under the highest stress, and osteoclasts break down bone in areas of the least stress.

Bone density, also called bone mineral density, is a measurement of the amount of minerals per unit area of bone. Bone density is correlated with bone strength. A person with low bone density is said to have osteoporosis. Osteoporosis is a disease characterized by weak bones that increases risk of bone fracture. It is most common among older women. Risk can be decreased with weight-bearing exercise and a diet high in bone-building minerals, such as calcium.

osteoblast - a cell that builds bone tissue. osteoclast - a cell that breaks down bone tissue. osteocyte - a mature bone cell that has many branches.

Bone is also made of nonliving structures, such as minerals and salts. A mineral is a natural substance with a crystal structure. Minerals and salts give bones strength and the ability to withstand physical impact

An atom is the smallest particle of matter. An element is a chemical made up of identical atoms.

Calcium and phosphorous are two elements that make up a large part of the structure of human bones. They are nutrients that people get from foods, and they help make bones strong. Foods rich in calcium include milk and broccoli. Foods high in phosphorous include fish, turkey, and beans.

Another important part of the matrix is made up of collagen fibers. A collagen fiber is a ropelike material that forms a mesh framework in the bone matrix. Minerals are deposited within the framework to give the bone its shape.

Collagen is one of many proteins found in the bone matrix. A protein is a type of organic (made from living matter) substance that is necessary for life. Collagen provides bone with flexibility and the ability to resist twisting forces. Other proteins perform functions related to bone growth.

Bones grow and develop throughout a person's lifetime. A child's long bones contain epiphyseal plates. The epiphyseal plate, also called the growth plate, is an area between the diaphysis and epiphysis where cartilage cells are actively dividing. As new cartilage cells are formed, they cause the ends of the diaphysis to lengthen, which elongates the bone. The cartilage becomes ossified (an adjective that describes something that has been turned into bone) as minerals are added to the site.

In children and teenagers, the growth plate constantly produces new cartilage and new bone as the bones enlarge. Epiphyseal closure is the process by which bone growth stops as adulthood is reached, which is characterized by the ossification of the growth plate. Even in adulthood, old bone cells are replaced with new ones. Bone remodeling is the process of bone cells being deposited and removed.

Bone marrow is a tissue that contains stem cells, unspecialized cells that have the potential to develop into specialized cells. Some bone marrow produces only blood cells. Other bone marrow produces fat, cartilage, and bone cells.

Infants are born with only red bone marrow. Over time, children develop yellow marrow. When a disease destroys or damages a person's bone marrow, it can be fatal. A bone marrow transplant is a medical procedure that takes healthy bone marrow from one person and transfers it into the body of an ill person to treat certain diseases.

Earlier in this lesson, you learned that long bones are longer than they are wide and are composed of a shaft and two ends.

The epiphyses are the ends of a long bone. These are usually wider than the shaft. The outside of the epiphyses is made of compact bone, and the interior is filled with spongy bone. Diaphysis is another name for the shaft, or the long, central section of a long bone. The diaphysis is usually composed of a ring of compact bone and a central channel filled with bone marrow. Long bones include the thighbone and upper arm bone, but not all long bones are "long" in terms of measurement. For example, each of the three bones that make up your pinky finger is classified as a long bone.

Tissue is a group of similar cells that work together. A cell is the basic structural and functional unit of life. An organ is a group of tissues working together to complete a task

The human body contains many different types of bones. Anatomy is the study of the physical structure of the human body. In this lesson, you will learn about anatomy and the functions of bones.

Short, flat, and irregular bones all have similar internal structures.

The outside surfaces of these bones are made of compact bone tissue. Their internal structures are composed of spongy bone. Bone marrow fills the spaces within the spongy bone. There are no central channels in short, flat, and irregular bones as there are in long bones.

Flat bones do not arise from cartilage as long bones do. Instead, osteoblasts create flat bones directly. Sheets of fibers form the basic structure of the flat bones. Blood vessels grow alongside the fibers. A blood vessel is a tube through which blood flows. These blood vessels deliver the nutrients and minerals necessary for bone growth.

This type of bone growth occurs during fetal development. It is also the process by which broken bones heal themselves.

Certain foods promote the development of healthy bones. Foods rich in calcium include: milk and dairy products. dark, leafy green vegetables. white beans.

Vitamin D is also essential, but it is not found naturally in many foods. As a result, several common products have been fortified with vitamin D, such as dairy products and breakfast cereals. A fortified food is a food that has had certain nutrients added to improve its healthful qualities. Some foods can negatively affect bones. Diets high in caffeinated beverages, such as soda, are linked to an increased risk of fracture. It is unknown whether this is due to reduced milk intake or to the caffeine. High-sugar diets are also related to decreased bone health.

Calcium is the most important mineral related to building strong and healthy bones. Other vitamins and minerals are necessary to help the body absorb calcium and use it to promote bone growth.

Vitamins that encourage bone growth include vitamin D and vitamin K. Elements responsible for healthy bones include magnesium, copper, and iron.

skeleton

an arrangement of bones that forms the structure of the human body

Cartilage and ligaments are structures of the skeletal system that help bone do its job. Cartilage is tough, flexible tissue that is not as rigid as bone. Cartilage:

covers the ends of bones at the joints. provides shape to nonbony structures, such as the ears and nose. acts as a shock absorber between the bones of the spine and in the knee. Ligaments are flexible, ropelike structures that attach bones to each other. They help keep joints stable during movement.

Bones have several functions, including:

giving the body structure. Bones support other tissues, like muscle (a tissue that can contract to enable movement) and skin, to support the shape of the body. protecting internal organs. Bones form a protective shield for organs. For example, the skull (a bony structure forming the shape of the head) protects the brain (the control center of the body). producing blood. The innermost cavities of some bones make blood cells. enabling the body to move. Muscles pull on the bones to produce movement. storing nutrients. Bones store minerals, such as calcium and phosphate, and then release them as necessary.

A bone contains several types of tissue. The tissues that make up bone are called:

periosteum - the outermost layer of bone. compact bone - bone tissue that is made up of stacks of cells arranged to form tiny, tightly packed cylinders that give the bone strength. spongy bone - bone tissue that is full of holes and made of cells arranged in beamlike structures that are positioned to support the stresses put on the bone. bone marrow - bone tissue that can create different types of cells. Red bone marrow is marrow that produces blood cells. Yellow bone marrow is marrow that produces fat, cartilage, and bone cells. Bone marrow is found in the holes in spongy bone.

bone

type of sturdy tissue that provides shape to the human body

In a developing fetus (unborn child), the skeleton begins as a basic structure made of fibers and cartilage. Bone begins to develop at about six to eight weeks. Ossification is the process of bone formation from fibers or cartilage. Flat bones develop from fibers in the fetus. Collagen fibers and osteoblasts begin the process. Bone matrix fills in the space between the fibers. Then bone cells and bone marrow form.

Most of the other bones form from cartilage. A bony ring forms around the middle of the cartilage. The cartilage then begins to break down within the center of the cartilage. Spongy bone replaces the disappearing cartilage. A cavity forms in the center of the bone. Finally, bone replaces the cartilage at the epiphyses. When a baby is born, the skeleton is still developing. A baby's skeleton has about 300 parts made of bone and cartilage tissue. Adults have 206 bones. Over time, the baby's cartilage will ossify, and some bones will fuse. For example, a baby's six skull bones are separate for the first year of its life. They fuse as the baby grows.

Bone density, also called bone mineral density, is a measurement of the amount of minerals per unit area of bone. Bone density is correlated with bone strength. A person with low bone density is said to have osteoporosis. Osteoporosis is a disease characterized by weak bones that increases risk of bone fracture. It is most common among older women. Risk can be decreased with weight-bearing exercise and a diet high in bone-building minerals, such as calcium.

Osteoblasts and osteoclasts arrive at the fracture and begin to produce bone tissue there. The broken bone begins to take the shape it had prior to the fracture.