Bone composition and structure:
Bones (or osseous material) serve a number of diverse purposes in the human anatomy.  In addition to providing structure, protection, and support for the organs of the body, bones also house marrow, which produces blood cells.  Within the bones are also stored the calcium deposits which the body may access, via resorption, when needed.  Additionally, bones detoxify the system, by removing heavy metals, such as lead and arsenic, as well as other toxins, from the bloodstream.  Osseous tissue itself is made of water (about 1/4 of the bone weight), organic material (about 1/3 of the bone weight, most of which is the protein, ossein) and inorganic minerals (calcium, phosphorus, and magnesium predominate,  though iron, sodium, potassium, chlorine, and fluorine are also present in small amounts). Most bones (with the exception of those of the cranium) are initially pre-formed in cartilage and are then ossified as the newborn develops.

Two basic classification methods exist to categorize the bones of the body.  These two classification systems are based upon anatomical location (axial or appendicular), and shape (long, short, flat, and irregular).  Axial bones are the eighty bones which lie along the central, vertical axis of the body and support and protect the head and torso and include the skull and the spinal
(vertebral) column.  Appendicular bones include the one hundred twenty-six bones which comprise the appendages, including the shoulders and hips, arms and legs, hands and feet, and fingers and toes.  The shape classifications include long bones (such as the radius, humerus, and femur), the short bones (such as the carpals, tarsals, and manual and pedal phalanges), flat bones
(such as the sternum, skull bones, and scapulae), and irregular bones (such as the vertebrae).

Articulated bones feature a cartilaginous covering at the joints, which facilitates the articulation by protecting the bones from shock and providing a softer bed to which the synovial membrane may be attached.  Osteoarthritis is a common disease among middle-aged and elderly people in which the articular cartilage becomes inflamed making movement of the bones at the
affected joints painful.

The compact bone tissue serves as the outer shell of the bone and serves to protect the inner core of spongy bone (trebiculae, or substantia spongiosa).  The compact bone shell is particularly thick in the middle of the shaft in long bones in order to protect the bone against bending.  The compact bone is covered by the periosteum.

The compact bone layer features a number of foramina (openings) which allow the nutrient vessel(s) to tunnel through to reach the marrow cavity and spongy bone tissue within.  Most bones have one main nutrient vessel which, by branching into a web of arterioles within the bone, feeds them, though the femur has two such nutrient blood vessels.  The bone has one foramen for the
entrance of each nutrient vessel, and foramina at the extremities for the produced blood to pass out of the bone.

The Haversian lamellae are layers of bone formed during the development of the bone which contain the Haversian canals.  These canals house the blood vessels, lymph vessels, nerves, and marrow of the bone.

The Volkmann's vessels are located within the Haversian canals in the Haversian lamellae.  These vessels carry the nutrients which nourish the bone tissue and carry newly generated blood cells and lymphocytes from the marrow
to the bloodstream.

The osteocytes are bone cells which have lost their ability to produce bone material.  These are the remnants of the osteoblasts which form bone tissue as the bone is developing.

The outer lamellae are the thin layers of bone tissue which are laid down as the bone is formed.  They lie just below the periosteum and form the outer surface of the compact bone tissue.

The periosteum is the tough, vascular membrane which covers the surface of a bone, except for the articular cartilage.  The periosteum contains the blood vessels which supply nutrients to the bones enabling them to regenerate.  The bones of the skull feature no such periosteum, and so cannot regenerate themselves.  The periosteum also facilitates the regeneration of bone by
serving as a confining membrane for the deposition of new bone cells, insuring that any regeneration of osseous material is added to the pre-existing bone.

The diaphysis, or shaft, of a long bone features a shell of compact bone surrounded by the periosteum, a cartilaginous membrane which contains the blood vessels which provide nutrients to the bone.  The diaphysis is separated from the epiphyses (ends) of the bone by the epiphyseal line.  When bones form, calcium salts are first deposited within the shaft (diaphysis), and this calcification spreads outward to the ends of the bone (epiphyses).  As this progresses, the periosteal membrane produces a network of fibrils (osteoblasts) in front of this advancing line of calcification, which provides a mesh framework for the ensuing calcification.  Once this calcified cartilage has developed, the periosteal membrane sends blood vessels into the bone which
carry nutrients as well as regulatory cells known as osteoclasts.  The osteoblasts and osteoclasts work together to replace the calcified cartilage with true, osseous material.  This process is carried out on the ends (epiphyses) of the bones as well, though a layer of uncalcified cartilage demarcates the epiphyses from the diaphysis until later in the life of the bone.  Once the true bone has developed, the center becomes hollowed out, which allows for the development of the marrow and the spongy tissue layer
(trabeculae).  The growth and development of the bone is regulated by a hormone secreted by the pituitary gland, with new growth taking place at the epiphyseal line.  At some stage, however, hormones, secreted by the testes in the male and ovaries in the female, cause this bone growth to cease, whereupon the epiphysis fuses to the diaphysis.  Beyond this point, which usually occurs earlier in females, the bone undergoes simultaneous resorption (where it breaks down and re-absorbs osseous material) and reconstruction.  Healthy bone is constantly undergoing resorption and reconstruction, though,  in the elderly, the reconstruction of bone is somewhat diminished, making  healing of fractures slower.

The spongy bone tissue (also called the substantia spongiosa, or trabeculae) is the porous, inner layer of bone beneath the compact bone shell.  So called because of its sponge-like structure of bony fiber, the spongy layer is actually very strong and resistant to compressive damage.  The spongy bone is particularly prevalent in the ends of long bones, where they are more subject to such damage.  Osteoporosis is a disease common in post-menopausal women (as well as others who do not get sufficient calcium and phosphorus in their diets) which degrades the structural integrity of the spongy tissue, causing
it to become brittle and more likely to chip or fracture.

The epiphysis (plural, epiphyses) is the end of a developing bone.  It is distinguished from the non-developing segment of the bone by the epiphyseal line.  When bones form, calcium salts are first deposited within the shaft (diaphysis), and this calcification spreads outward to the ends of the bone (epiphyses).  As this progresses, the periosteal membrane produces a network of fibrils (osteoblasts) in front of this advancing line of calcification, which provides a mesh framework for the ensuing calcification.  Once this calcified cartilage has developed, the periosteal membrane sends blood vessels into the bone which carry nutrients as well as regulatory cells known as osteoclasts.  The osteoblasts and osteoclasts work together to replace the
calcified cartilage with true, osseous material.  This process is carried out on the ends (epiphyses) of the bones as well, though a layer of uncalcified cartilage demarcates the epiphyses from the diaphysis until later in the life of the bone.  Once the true bone has developed, the center becomes hollowed out, which allows for the development of the marrow and the spongy tissue layer (trabeculae).  The growth and development of the bone is regulated by a hormone secreted by the pituitary gland, with new growth taking place at the epiphyseal line.  At some stage, however, hormones, secreted by the testes in the male and ovaries in the female, cause this bone growth to cease, whereupon the epiphysis fuses to the diaphysis.  Beyond this point, which usually occurs earlier in females, the bone undergoes simultaneous resorption (where it breaks down and re-absorbs osseous material) and reconstruction.  Healthy bone is constantly undergoing resorption and reconstruction, though,  in the elderly, the reconstruction of bone is somewhat diminished, making healing of fractures slower.

The endosteum is the layer of bone which lines the inner (marrow) cavity within the long bones which houses the bone marrow.  It is distinguished from the periosteum, which is the external membrane which covers the surface of the compact bone tissue.

The marrow (also called medullary) cavity is the region within the bone which houses the marrow, responsible for generation of blood cells.  The marrow in newborns and children is generally red, turning yellow in adults in all bones with the exceptions of upper ends of the humerus and femur and in many of the flat bones of the skull, vertebrae, ribs, sternum, and hip.  The red marrow, also known as myeloid tissue, produces all types of blood cells except for lymphocytes and monocytes (which are formed primarily in the lymph nodes and the spleen).  Anemia is a disease in which the myeloid tissue cannot produce sufficient red blood cells (as when the body does not get enough of the mineral iron), with the chief symptom being chronic fatigue.

List of bones
Types of movement

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