• There are 206 bones in the average human skeleton.

• There is a naturally occurring variant in which approximately one person out of 200 possesses an additional rib.

• Bone is an active tissue that, while being around 22 percent water, has a structure that is incredibly robust while also being remarkably lightweight and flexible.

• The skeleton has the ability to mend whatever damage it sustains, which is a significant benefit.

• It is also capable of remodeling its bones in order to thicken and strengthen places that receive greater stress as a result of activities such as weightlifting and running.

• The axial and appendicular skeletons are the two primary divisions of the skeleton that make up the human body.

• The sternum, the ribs, the vertebral column, and the skull are the components that make up the axial skeleton.

• The bones of the shoulder, arm, wrist, and hand, as well as the bones of the hips, legs, ankles, and feet, are all included in the appendicular skeleton.

• Eighty of the 206 bones are located in the axial skeleton, while 64 are located in the upper appendicular skeleton and 62 are located in the lower appendicular skeleton.

BONE SHAPES

• The structure of a bone can be used to infer its function.

• Sesamoid bones are small and are immersed within tendons; flat bones provide big surface areas for the attachment of muscles; long bones function like levers; and flat bones have large surface surfaces.

STRUCTURE OF A BONE

• The medullary canal, also known as the marrow cavity, can be found running along the middle of the shaft of a long bone (like the femur or the humerus).

• This contains red bone marrow, which is responsible for the production of blood cells; yellow bone marrow, which is primarily composed of fatty tissue; as well as blood arteries.

• A layer of spongy bone (called cancellous bone) surrounds the marrow cavity.

• Within the honeycomb-like spaces of this layer of cancellous bone lies more marrow.

• This is surrounded by a layer of compact (cortical) bone, which is bone that is extremely hard, thick, and robust.

• The periosteum, which is a membrane that covers the surface of the bone, is connected to the marrow cavity by a network of small canals.

• Bone tissue is composed of specialized cells and protein fibers, which are woven into a matrix of water, mineral salts, and other substances.

• These components are held together by a network of connective tissue.

• Osteocytes are responsible for maintaining a healthy bone structure, while osteoblasts are responsible for calcifying bone as it is being formed, and osteoclasts are responsible for absorbing bone tissue in areas where it is either degenerating or is no longer required.

Blood vessel

• Rich network of blood vessels nourishes bone

Compact bone

• Bone gets its strength from this hard, shell-like tissue

Periosteum

• Fibrous membrane covering entire bone surface (except in joints)

INSIDE A BONE

• The longer bones in the body, such as those in the leg, are made up of a variety of distinct forms of bone tissue.

BONE GROWTH

• The majority of bones originate from cartilage-based structures during the stages of development that occur in the womb and in early childhood.

• The transformation of cartilage into bone tissue is accomplished through a process called ossification, which involves the deposition of mineral salts and crystals.

• There is a region called the growth plate close to each end of a long bone.

• This is the location where the bone lengthens and ossifies.

• In this region, cartilage cells proliferate and organize themselves into columns that extend toward the bone shaft.

• New bone cells go in to occupy the space left behind by expanding cartilage cells when these cells eventually perish.

CARTILAGE TO BONE

• When a long bone is developing, the process of ossification begins between the shaft and the head.

• Ossification will eventually take place on the inside of the head as well.

CARTILAGE

• The resilient and malleable type of connective tissue known as cartilage.

• It is made up of a matrix that is similar to gel and contains a variety of substances, including proteins and carbohydrates.

• In addition to the chondrocyte cells that are responsible for the formation and upkeep of the entire tissue, this tissue contains a variety of different types of fibers.

• There are a few different types of cartilage, the most common of which are hyaline cartilage, fibrocartilage, and elastic cartilage.

• Elastic cartilage is a springy material that may be found in places like the larynx and the outer ear flap.

OSTEON

• This unit, which is in the shape of a rod, is the fundamental component of compact bone.

• Its core canal, known as the Haversian canal, is encircled by concentric layers of tissue. These layers include blood vessels and nerves (lamellae).

• Osteocytes, the cells responsible for the maintenance of bones, are found in the lacunae, which are gaps in the tissue.

HYALINE CARTILAGE

• This cartilage has dense collagen fibers, which makes it exceptionally robust and resistant.

• In addition to these functions, it can be found in the trachea and the nose, where it protects the ends of bones in joints and connects the ribs to the sternum.

Bone marrow

• The tissue that fills the central chamber of a bone; initially, long bones have red marrow, but over time, this transforms into yellow marrow.

Spongy bone

• Structure in the form of a latticework made up of bone spikes (trabeculae), which are placed along the lines of highest stress.

Epiphysis

• enlarged portion of bone that is primarily composed of spongy bone tissue

Bone shaft

• Mostly compact bone and marrow

FIBROCARTILAGE

• The majority of this consists of tight bundles of collagen fibers, with only a little amount of a gel-like matrix.

• It is also present in the knee joints and the intervertebral disks of the spine.