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In the adult skeletal system it contains 206 individual bones. But in the infants , bones are very soft spot on the baby’s head, the fontanel. The bone has not yet been formed there ,but later it will harden when ossification occurs ,Due to mineral deposits continues through child hood.

The functions of bone are .....
Bones make up the structure of your body, but it has a lot of jobs it does. It protects all the organs in your body , For example : the ribs and breastbone protect the lung and the heart, the vertebral column protects and encases the spinal cord , the brain , parts of the eye and the inter ear. Bone is hard but it allows movement. Ligaments , are fibrous bands that connect bone to bones and Cartilage and serve as support for muscles. It also provides mineral storage. It stores - calcium and phosphorus. The body uses these stored minerals to maintain homeostasis. It’s also the site for hematopoiesis , which is the formation of red blood cells.

Structure of a long bone :
A typical long bones contains shaft
, or diaphysis . This is a hollow cylinder of hard , compact bone. It is what makes a long bone strong and hard yet light enough for movement. At each end of the diaphysis is an epiphysis. In the center of The shaft is a broad Medullary canal. This is filled with yellow bone marrow mostly made of fat cells. The Marrow also contains many blood vessels and some cells that form white blood cells, also know as leukocytes . The endosteum is the lining of the marrow canal , that keeps the cavity intact. Spongy bone is located at the ends of the long bones and forms the center of all other bones. The outside of the bone isn’t covered with periosteum. Covering the epiphysis is the articular cartilage.

the compact bone that surrounds the typical long bone:
Compact bone, also called cortical bone, dense bone in which the bony matrix is solidly filled with organic ground substance and inorganic salts, leaving only tiny spaces (lacunae) that contain the osteocytes, or bone cells. Compact bone makes up 80 percent of the human skeleton; the remainder is cancellous bone, which has a spongelike appearance with numerous large spaces and is found in the marrow space (medullary cavity) of a bone. Both types are found in most bones. Compact bone forms a shell around cancellous bone and is the primary component of the long bones of the arm and leg and other bones, where its greater strength and rigidity are needed.

On the average the skeletal system replaces itself around every 7 years.

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The metaphysis is the narrow portion of a long bone between the epiphysis and the diaphysis. It contains the growth plate, the part of the bone that grows during childhood, and as it grows it ossifies near the diaphysis and the epiphyses.This region (metaphysis) functions to transfer loads from weight-bearing joint surfaces to the diaphysis.

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It consists of meshwork Of interconnecting sections of bone called trabeculae , trabeculae of bone provide structural support to the spongy bone found at the ends of long bones.

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Is the lowest level of the bone which contains trabeculae , spongy bone , periosteum and compact bone

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The diaphysis  is the main or midsection (shaft) of a long bone. It is made up of cortical bone and usually contains bone marrow and adipose tissue (fat). It is a middle tubular part composed of compact bone which surrounds a central marrow cavity which containd yellow marrow.It is responsible for supporting the weight of the body as columns and, at the same time, increase the power of the muscles working as a lever. Not all bones have diaphysis, only long bones.

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Is the top section of the long bone. It Contains the growth line and the articular cartilage.

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is the smooth, white tissue that covers the ends of bones where they come together to form joints. Healthy cartilage in our joints makes it easier to move. It allows the bones to glide over each other with very little friction. The articular cartilage can be damaged by injury or normal wear and tear.

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is found mostly at the ends of bones and joints. About 20% of the bone in your body is spongy . Unlike compact bone that is mostly solid, spongy bone is full of open sections called pores. ... Pores are filled with marrow, nerves, and blood vessels that carry cells and nutrients in and out of the bone.

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The epiphyseal line the part of the bone that replaces the epiphyseal growth place in long bones once a person has reached their full adult height.  It permits growth and lengthening of the bone, as the cartilage reproduces and ossifies. Either rounded end of a long bone is called an epidhysis and the shaft of the bone is called the diaphysis .  The epiphyseal line is the marking that indicates where the two parts of the bone meet and where the Epiphyseal plate was once located in children and young adults.

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The endosteum is a thin vascular membrane of connective tissue that lines the inner surface of the bony tissue that forms the medullary cavity of long bones. It is responsible for bone growth and repair after a bone is broken. It also helps trigger bone remodeling. In organisms that suffer from malnutrition, this layer can be reabsorbed.

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Compact bone, also called cortical bone, dense bone in which the bony matrix is solidly filled with organic ground substance and inorganic salts, leaving only tiny spaces (lacunae) that contain the osteocytes, or bone cells.Repair , replace , remodel : In these lacunae they contain Osteoblasts which build up the bone , When they Mature they become osteaocytes . Osteoclasts is what breaks down the bone to get ready to lay new bone Down which is done by osteoblasts.

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The periosteum is a membrane that covers the outer surface of all bones except at the joints of long bones endosteum lines the inner surface of the medullary cavity of all long bones . It’s necessary for bone growth repair and nutrition

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, usually accompanied by one or two veins ,enters the bone through the nutrient foramen, runs obliquely through the cortex, sends branches upward and downward to the bone marrow which ramify in the endosteum – the vascular membrane lining the medullary cavity , and give twigs to the adjoining canals. Nutrient arteries are the most apparent blood vessels of the bones. One of the main arterial blood supplies to a typical long bone; . Other blood supply routes to bone include metaphyseal, epiphyseal and periosteal arteries.