Gray's Anatomy illustration of a human femur. Henry Gray's Anatomy of the Human Body (or Gray's Anatomy as it has commonly been shortened is an English-language Human anatomy Textbook The femur is the thigh bone In Humans, it is the longest, most voluminous and strongest Bone.

Bones are rigid organs that form part of the endoskeleton of vertebrates. In Biology, an organ ( Latin: organum, "instrument tool" from Greek όργανον - organon "organ instrument An endoskeleton is an internal support structure of an Animal. Vertebrates are members of the Subphylum Vertebrata, Chordates with backbones or spinal columns The grouping sometimes includes They function to move, support, and protect the various organs of the body, produce red and white blood cells and store minerals. Red blood cells are the most common type of Blood cell and the Vertebrate body's principal means of delivering Oxygen to the body tissues via the Blood Because bones come in a variety of shapes and have a complex internal and external structure, they are lightweight, yet strong and hard, in addition to fulfilling their many other functions. One of the types of tissues that makes up bone is the mineralized osseous tissue, also called bone tissue, that gives it rigidity and honeycomb-like three-dimensional internal structure. Osseous tissue, or bone tissue is the major structural and supportive Connective tissue of the body Other types of tissue found in bones include marrow, endosteum and periosteum, nerves, blood vessels and cartilage. Bone marrow is the flexible tissue found in the hollow interior of Bones In adults marrow in large bones produces new Blood cells It constitutes 4% of The endosteum (plural endostea is a thin layer of Connective tissue which lines the surface of the bony tissue that forms the Medullary cavity of long Bones Periosteum is a Membrane that lines the outer surface of all bones, except at the joints of Long bones. A nerve is an enclosed cable-like bundle of peripheral Axons (the long slender projections of Neurons. The blood vessels are part of the Circulatory system and function to transport Blood throughout the body Cartilage is a type of dense Connective tissue. It is composed of specialized cells called chondrocytes that produce a large amount of extracellular matrix There are 206 bones in the adult body and about 300 bones in the infant body.

Functions

Bones have eight main functions:

• Protection — Bones can serve to protect internal organs, such as the skull protecting the brain or the ribs protecting the heart and lungs. The brain is the center of the Nervous system in animals All Vertebrates and the majority of Invertebrates have a brain In Vertebrate Anatomy, ribs ( Latin costae) are the long curved Bones which form the ribcage. The heart is a muscular organ in all Vertebrates responsible for pumping Blood through the Blood vessels by repeated rhythmic lung is the essential Respiration organ in air-breathing Animals including most Tetrapods a few Fish and a few Snails The most primitive
• Shape — Bones provide a frame to keep the body supported.
• Blood production — The marrow, located within the medullary cavity of long bones and interstices of cancellous bone, produces blood cells in a process called haematopoiesis. Bone marrow is the flexible tissue found in the hollow interior of Bones In adults marrow in large bones produces new Blood cells It constitutes 4% of The medullary cavity ( medulla, innermost part is the central cavity of Bone shafts where red bone marrow and/or yellow bone marrow ( Adipose tissue is Haematopoiesis (from Ancient Greek haima blood poiesis to make (or hematopoiesis in the United States sometimes also haemopoiesis or
• Mineral storage — Bones act as reserves of minerals important for the body, most notably calcium and phosphorus. Calcium (ˈkælsiəm is the Chemical element with the symbol Ca and Atomic number 20 Phosphorus, (ˈfɒsfərəs is the Chemical element that has the symbol P and Atomic number 15
• Movement — Bones, skeletal muscles, tendons, ligaments and joints function together to generate and transfer forces so that individual body parts or the whole body can be manipulated in three-dimensional space. Skeletal muscle is a type of Striated muscle, which usually attaches to tendons A tendon (or sinew) is a tough band of Fibrous connective tissue that usually connects Muscle to Bone and is capable of withstanding tension In Anatomy, the term ligament is used to denote three different types of structures Fibrous tissue that connects Bones to other bones A joint is the location at which two or more Bones make contact The interaction between bone and muscle is studied in biomechanics. Biomechanics is the application of mechanical principles on living organisms
• Acid-base balance — Bone buffers the blood against excessive pH changes by absorbing or releasing alkaline salts.
• Detoxification — Bone tissues can also store heavy metals and other foreign elements, removing them from the blood and reducing their effects on other tissues. These can later be gradually released for excretion.
• Sound transduction — Bones are important in the mechanical aspect of hearing.

Characteristics

The primary tissue of bone, osseous tissue, is a relatively hard and lightweight composite material, formed mostly of calcium phosphate in the chemical arrangement termed calcium hydroxylapatite (this is the osseous tissue that gives bones their rigidity). Osseous tissue, or bone tissue is the major structural and supportive Connective tissue of the body The Rockwell scale is a Hardness scale based on the Indentation hardness of a material Composite materials (or composites for short are engineered Materials made from two or more constituent materials with significantly different physical or chemical Calcium phosphate is the name given to a family of Minerals containing Calcium Ions (Ca2+ together with orthophosphates (PO43- Hydroxylapatite, also called hydroxyapatite, is a Mineral. It is a naturally occurring form of calcium Apatite with the formula Ca5(PO43(OH Osseous tissue, or bone tissue is the major structural and supportive Connective tissue of the body It has relatively high compressive strength but poor tensile strength, meaning it resists pushing forces well, but not pulling forces. Compressive strength is the capacity of a Material to withstand axially directed pushing forces Tensile strength \sigma_{UTS} or S_U is the Stress at which a material breaks or permanently deforms While bone is essentially brittle, it does have a significant degree of elasticity, contributed chiefly by collagen. A material is said to be elastic if it deforms under stress (e Collagen is the main Protein of Connective tissue in Animals and the most abundant protein in Mammals making up about 50% of the whole-body protein All bones consist of living cells embedded in the mineralized organic matrix that makes up the osseous tissue. The cell is the structural and functional unit of all known living Organisms It is the smallest unit of an organism that is classified as living and is often called

Masto-structure

Gross anatomy

See also: Human skeleton and List of bones of the human skeleton

Individual bones

Bone is not a uniformly solid material, but rather has some spaces between its hard elements. The human skeleton consists of both fused and individual Bones supported and supplemented by Ligaments Tendons Muscles and Cartilage A typical Adult Human skeleton commonly consists of 206 208 or more bones depending on the method used in counting

Section through the head of the femur, showing the outer layer of compact bone and the soft center of trabecular bone, filled with red bone marrow and a spot of yellow bone marrow (white bar = 1 centimeter)

Compact bone

The hard outer layer of bones is composed of compact bone tissue, so-called due to its minimal gaps and spaces. Cortical bone, or compact bone, is one of two main types of Osseous tissue. This tissue gives bones their smooth, white, and solid appearance, and accounts for 80% of the total bone mass of an adult skeleton. Compact bone may also be referred to as dense bone or cortical bone.

Trabecular bone

Filling the interior of the organ is the trabecular bone tissue (an open cell porous network also called cancellous or spongy bone) which is composed of a network of rod- and plate-like elements that make the overall organ lighter and allowing room for blood vessels and marrow. Cancellous Bone is a type of Osseous tissue with a low density and strength but very high Surface area, that fills the inner cavity of long bones Porosity is a measure of the void spaces in a material and is measured as a fraction between 0–1 or as a Percentage between 0–100% Trabecular bone accounts for the remaining 20% of total bone mass, but has nearly ten times the surface area of compact bone.

Cellular structure

There are several types of cells constituting the bone;

• Osteoblasts are mononucleate bone-forming cells which descend from osteoprogenitor cells. An osteoblast (from the Greek words for " Bone " and "germ" or embryonic is a mononucleate cell that is responsible for bone formation An osteoblast (from the Greek words for " Bone " and "germ" or embryonic is a mononucleate cell that is responsible for bone formation They are located on the surface of osteoid seams and make a protein mixture known as osteoid, which mineralizes to become bone. Osteoid is the organic portion of the matrix of bone tissue. Osteoblasts begin the process of forming bone tissue by secreting the osteoid as several specific Osteoid is primarily composed of Type I collagen. Collagen is the main Protein of Connective tissue in Animals and the most abundant protein in Mammals making up about 50% of the whole-body protein Osteoblasts also manufacture hormones, such as prostaglandins, to act on the bone itself. Hormones (from Greek ὁρμή - "impetus" are chemicals released by cells that affect cells in other parts of the body A prostaglandin is any member of a group of Lipid compounds that are derived enzymatically from Fatty acids and have important functions in the Animal body They robustly produce alkaline phosphatase, an enzyme that has a role in the mineralisation of bone, as well as many matrix proteins. Alkaline phosphatase ( ALP) ( is a Hydrolase Enzyme responsible for removing Phosphate groups from many types of molecules including In Biology, the extracellular matrix ( ECM) is the Extracellular part of animal tissue that usually provides structural support to the cells Osteoblasts are the immature bone cells.

• Bone lining cells are essentially inactive osteoblasts. They cover all of the available bone surface and function as a barrier for certain ions.
• Osteocytes originate from osteoblasts which have migrated into and become trapped and surrounded by bone matrix which they themselves produce. An osteocyte, a star-shaped cell, is the most abundant cell found in Bone. The spaces which they occupy are known as lacunae. Osteocytes have many processes which reach out to meet osteoblasts and other osteocytes probably for the purposes of communication. Their functions include to varying degrees: formation of bone, matrix maintenance and calcium homeostasis. They have also been shown to act as mechano-sensory receptors—regulating the bone's response to stress and mechanical load. They are mature bone cells.

• Osteoclasts are the cells responsible for bone resorption (remodeling of bone to reduce its volume). An osteoclast (from the Greek words for "bone" and "broken" is a type of Bone cell that removes Bone tissue by removing its Mineralized matrix Bone resorption is the process by which Osteoclasts break down Bone and release the Minerals resulting in a transfer of calcium from bone fluid to the blood Osteoclasts are large, multinucleated cells located on bone surfaces in what are called Howship's lacunae or resorption pits. These lacunae, or resorption pits, are left behind after the breakdown of bone and often present as scalloped surfaces. Because the osteoclasts are derived from a monocyte stem-cell lineage, they are equipped with engulfment strategies similar to circulating macrophages. Monocyte is a type of Leukocyte, part of the Human body 's Immune system. Stem cells are cells found in most if not all multi-cellular Organisms. Macrophages ( Greek: "big eaters" from makros "large" + phagein "eat" ( Mø) are cells within the tissues that Osteoclasts mature and/or migrate to discrete bone surfaces. Upon arrival, active enzymes, such as tartrate resistant acid phosphatase, are secreted against the mineral substrate. Tartrate resistant acid phosphatase is a Glycosylated monomeric metalloenzyme expressed in mammals

Molecular structure

Matrix

The matrix is the major constituent of bone, surrounding the cells. It has inorganic and organic parts.

Inorganic

The inorganic is mainly crystalline mineral salts and calcium, which is present in the form of hydroxyapatite. Hydroxylapatite, also called hydroxyapatite, is a Mineral. It is a naturally occurring form of calcium Apatite with the formula Ca5(PO43(OH The matrix is initially laid down as unmineralized osteoid (manufactured by osteoblasts). Mineralisation involves osteoblasts secreting vesicles containing alkaline phosphatase. A vesicle is a small bubble of liquid within a cell A more formal definition in Cell biology, would be that a vesicle is a relatively small intracellular membrane-enclosed This cleaves the phosphate groups and acts as the foci for calcium and phosphate deposition. The vesicles then rupture and act as a centre for crystals to grow on.

Organic

The organic part of matrix is mainly composed of Type I collagen. Collagen is the main Protein of Connective tissue in Animals and the most abundant protein in Mammals making up about 50% of the whole-body protein This is synthesised intracellularly as tropocollagen and then exported. It then associates into fibrils. Fibril is a fine Fiber approximately 1 nm in diameter Cytoplasmic fibrils are observed on the protoplasmic cylinders found in most Spirochetal Also making up the organic part of matrix include various growth factors, the functions of which are not fully known. Other factors present include glycosaminoglycans, osteocalcin, osteonectin, bone sialo protein and Cell Attachment Factor. Glycosaminoglycans (GAGs or mucopolysaccharides are long unbranched Polysaccharides consisting of a repeating Disaccharide unit Osteocalcin is a noncollagenous protein found in bone and dentin Osteonectin is a Glycoprotein in the Bone that binds Calcium. Bone sialoprotein (BSP is a component of mineralized tissues such as Bone, Dentin, Cementum and calcified Cartilage. One of the main things that distinguishes the matrix of a bone from that of another cell is that the matrix in bone is hard.

Woven or lamellar

Collagen fibres of woven bone

Bone is first deposited as woven bone, in a disorganized structure with a high proportion of osteocytes in young and in healing injuries. An osteocyte, a star-shaped cell, is the most abundant cell found in Bone. Woven bone is weaker, with a small number of randomly oriented collagen fibers, but forms quickly. It is replaced by lamellar bone, which is highly organized in concentric sheets with a low proportion of osteocytes. Lamellar bone is stronger and filled with many collagen fibers parallel to other fibers in the same layer (these parallel columns are called osteons). The fibers run in opposite directions in alternating layers, much like plywood, assisting in the bone's ability to resist torsion forces. The term torsion may refer the following In geometry Torsion of curves Torsion tensor in differential geometry After a break, woven bone quickly forms and is gradually replaced by slow-growing lamellar bone on pre-existing calcified hyaline cartilage through a process known as "bony substitution. Cartilage is a type of dense Connective tissue. It is composed of specialized cells called chondrocytes that produce a large amount of extracellular matrix "

Five types of bones

There are five types of bones in the human body: long, short, flat, irregular and sesamoid.

• Long bones are characterized by a shaft, the diaphysis, that is much greater in length than width. The long bones are those that are longer than they are wide and grow primarily by elongation of the Diaphysis, with an Epiphysis at the ends of the growing Bone The diaphysis is the main or mid section (shaft of a long bone. They are comprised mostly of compact bone and lesser amounts of marrow, which is located within the medullary cavity, and spongy bone. Cortical bone, or compact bone, is one of two main types of Osseous tissue. Bone marrow is the flexible tissue found in the hollow interior of Bones In adults marrow in large bones produces new Blood cells It constitutes 4% of The medullary cavity ( medulla, innermost part is the central cavity of Bone shafts where red bone marrow and/or yellow bone marrow ( Adipose tissue is Cancellous Bone is a type of Osseous tissue with a low density and strength but very high Surface area, that fills the inner cavity of long bones Most bones of the limbs, including those of the fingers and toes, are long bones. The metacarpus is the intermediate part of the Hand Skeleton that is located between the Phalanges (bones of the fingers Distally and the The metatarsus consists of the five long Bones of the Foot, which are numbered from the medial side ( ossa metatarsalia I The exceptions are those of the wrist, ankle and kneecap. In Tetrapods the carpus is the sole cluster of the Bones in the Wrist between the radius and Ulna and the Metacarpus In Tetrapods the tarsus are the cluster of Bones in the Foot between the Tibia and Fibula and the Metatarsus. The patella or kneecap is a thick triangular Bone which articulates with the Femur and covers and protects the knee joint

• Short bones are roughly cube-shaped, and have only a thin layer of compact bone surrounding a spongy interior. Where a part of the skeleton is intended for strength and compactness his kaka combined with limited movement it is constructed of a number of short bones, as in the Carpus The bones of the wrist and ankle are short bones, as are the sesamoid bones. In Anatomy, a sesamoid bone is a Bone embedded within a Tendon.
• Flat bones are thin and generally curved, with two parallel layers of compact bones sandwiching a layer of spongy bone. Flat Bones.—Where the principal requirement is either extensive protection or the provision of broad surfaces for muscular attachment the bones are expanded into broad flat plates Most of the bones of the skull are flat bones, as is the sternum. The sternum (from Greek στέρνον sternon, "chest" or breastbone) is a long flat Bone located in the center of the thorax (chest
• Irregular bones do not fit into the above categories. The irregular bones are bones which from their peculiar form cannot be grouped as Long bone, Short bone, Flat bone or Sesamoid bone. They consist of thin layers of compact bone surrounding a spongy interior. As implied by the name, their shapes are irregular and complicated. The bones of the spine and hips are irregular bones.
• Sesamoid bones are bones embedded in tendons. In Anatomy, a sesamoid bone is a Bone embedded within a Tendon. Since they act to hold the tendon further away from the joint, the angle of the tendon is increased and thus the force of the muscle is increased. Examples of sesamoid bones are the patella and the pisiform

Formation

The formation of bone during the fetal stage of development occurs by two processes: intramembranous and endochondral ossification. The pisiform bone (also called pisiform or lentiform bone) is a small knobbly pea-shaped Wrist bone Intramembranous ossification is one of the two processes during Fetal development of the mammalian skeletal system in which Bone tissue is created Endochondral ossification is one of the two processes during Fetal development of the mammalian skeletal system in which Bone tissue is

Intramembranous ossification mainly occurs during formation of the flat bones of the skull; the bone is formed from mesenchyme tissue. Mesenchyme refers to loosely organized connective tissue present in the embryo regardless of origin The steps in intramembranous ossification are:

1. Development of ossification center
2. Calcification
3. Formation of trabeculae
4. Development of periosteum

Endochondral ossification

Endochondrial ossification

Endochondral ossification, on the other hand, occurs in long bones, such as limbs; the bone is formed from cartilage. The steps in endochondral ossification are:

1. Development of cartilage model
2. Growth of cartilage model
3. Development of the primary ossification center
4. Development of the secondary ossification center
5. Formation of articular cartilage and epiphyseal plate

Endochondral ossification begins with points in the cartilage called "primary ossification centers. The epiphyseal plate (or epiphysial plate, physis, or growth plate) is a hyaline Cartilage plate in the metaphyses of children and " They mostly appear during fetal development, though a few short bones begin their primary ossification after birth. They are responsible for the formation of the diaphyses of long bones, short bones and certain parts of irregular bones. Secondary ossification occurs after birth, and forms the epiphyses of long bones and the extremities of irregular and flat bones. The diaphysis and both epiphyses of a long bone are separated by a growing zone of cartilage (the epiphyseal plate). The epiphyseal plate (or epiphysial plate, physis, or growth plate) is a hyaline Cartilage plate in the metaphyses of children and When the child reaches skeletal maturity (18 to 25 years of age), all of the cartilage is replaced by bone, fusing the diaphysis and both epiphyses together (epiphyseal closure).

Bone marrow

There are two types of bone marrow, yellow and red, most commonly seen is red Bone marrow can be found in almost any bone that holds cancellous tissue. Bone marrow is the flexible tissue found in the hollow interior of Bones In adults marrow in large bones produces new Blood cells It constitutes 4% of In newborns, all such bones are filled exclusively with red marrow , but as the child ages it is mostly replaced by yellow, or fatty marrow. In adults, red marrow is mostly found in the flat bones of the skull, the ribs, the vertebrae and pelvic bones.

Remodeling

Remodeling or bone turnover is the process of resorption followed by replacement of bone with little change in shape and occurs throughout a person's life. Osteoblasts and osteoclasts, coupled together via paracrine cell signalling, are referred to as bone remodeling units. Paracrine signaling is a form of Cell signaling in which the target cell is near (" Para " = near the signal-releasing cell

Purpose

The purpose of remodeling is to regulate calcium homeostasis, repair micro-damaged bones (from everyday stress) but also to shape and sculpture the skeleton during growth. Calcium metabolism or calcium homeostasis is the mechanism by which the body maintains adequate Calcium levels

Calcium balance

The process of bone resorption by the osteoclasts releases stored calcium into the systemic circulation and is an important process in regulating calcium balance. As bone formation actively fixes circulating calcium in its mineral form, removing it from the bloodstream, resorption actively unfixes it thereby increasing circulating calcium levels. These processes occur in tandem at site-specific locations.

Repair

Repeated stress, such as weight-bearing exercise or bone healing, results in the bone thickening at the points of maximum stress (Wolff's law). It has been hypothesized that this is a result of bone's piezoelectric properties, which cause bone to generate small electrical potentials under stress. Piezoelectricity is the ability of some materials (notably Crystals and certain Ceramics including bone to generate an Electric potential in response to ^[1]

Paracrine cell signalling

The action of osteoblasts and osteoclasts are contolled by a number of chemical factors which either promote or inhibit the activity of the bone remodelling cells, controlling the rate at which bone is made, destroyed or changed in shape. An osteoblast (from the Greek words for " Bone " and "germ" or embryonic is a mononucleate cell that is responsible for bone formation An osteoclast (from the Greek words for "bone" and "broken" is a type of Bone cell that removes Bone tissue by removing its Mineralized matrix Enzymes are Biomolecules that catalyze ( ie increase the rates of Chemical reactions Almost all enzymes are Proteins The cells also use paracrine signalling to control the activity of each other. Paracrine signaling is a form of Cell signaling in which the target cell is near (" Para " = near the signal-releasing cell

Osteoblast stimulation

Osteoblasts can be stimulated to increase bone mass through increased secretion of osteoid and by inhibiting the ability of osteoclasts to break down osseous tissue. Osteoid is the organic portion of the matrix of bone tissue. Osteoblasts begin the process of forming bone tissue by secreting the osteoid as several specific Enzyme inhibitors are Molecules that bind to Enzymes and decrease their activity. Osseous tissue, or bone tissue is the major structural and supportive Connective tissue of the body

Bone building through increased secretion of osteoid is stimulated by the secretion of growth hormone by the pituitary, thyroid hormone and the sex hormones (estrogens and androgens). Growth hormone ( GH) is a Peptide hormone that stimulates growth and cell reproduction in humans and other animals The pituitary gland, or hypophysis, is an Endocrine gland about the size of a Pea. The thyroid hormones, Thyroxine ( T4) and Triiodothyronine ( T3) are Tyrosine -based Hormones produced Estrogens (US otherwise oestrogens or œstrogens) are a group of Steroid compounds named for their importance in the Estrous cycle, Androgen is the generic term for any natural or synthetic compound usually a Steroid Hormone, that stimulates or controls the development and maintenance of masculine These hormones also promote increased secretion of osteoprotegerin. Osteoprotegerin (OPG, also known as osteoclastogenesis inhibitory factor (OCIF is a Cytokine, which can inhibit the production of Osteoclasts. ^[2] Osteoblasts can also be induced to secrete a number of cytokines that promote reabsorbtion of bone by stimulating osteoclast activity and differentiation from progenitor cells. Cytokines are a category of signalling Proteins and Glycoproteins that like Hormones and Neurotransmitters, are used extensively in cellular Vitamin D, parathyroid hormone and stimulation from osteocytes induce osteoblasts to increase secretion of RANK-ligand and interleukin 6, which cytokines then stimulate increased reabsorbtion of bone by osteoclasts. Vitamin D is a group of fat-soluble Prohormones, the two major forms of which are vitamin D2 (or Ergocalciferol) and vitamin D3 (or Parathyroid hormone (PTH, or parathormone, is secreted by the Parathyroid glands as a Polypeptide containing 84 Amino acids. In Chemistry, a ligand is either an Atom, Ion, or Molecule (see also Functional group) that bonds to a central metal generally These same compounds also increase secretion of macrophage colony-stimulating factor by osteoblasts, which promotes the differentiation of progenitor cells into osteoclasts, and decrease secretion of osteoprotegerin. Macrophage colony-stimulating factor, or M-CSF is a secreted Cytokine which influences Hemopoietic stem cells to differentiate into Macrophages or other Osteoprotegerin (OPG, also known as osteoclastogenesis inhibitory factor (OCIF is a Cytokine, which can inhibit the production of Osteoclasts.

Osteoclast inhibition

The rate at which osteoclasts resorb bone is inhibited by calcitonin and osteoprotegerin. Calcitonin is a 32-amino acid linear polypeptide Hormone that is produced in Humans primarily by the parafollicular (also known as C-cells of the Calcitonin is produced by parafollicular cells in the thyroid gland, and can bind to receptors on osteoclasts to directly inhibit osteoclast activity. Parafollicular cells (also called C cells) are cells in the Thyroid which produce and secrete Calcitonin. The thyroid is one of the largest Endocrine glands in the body Osteoprotegerin is secreted by osteoblasts and is able to bind RANK-L, inhibiting osteoclast stimulation. ^[2]

Disorders

See also: List of skeletal disorders

There are many disorders of the skeleton. This is a list of skeletal disorders, these affect the development and structure of the Skeletal system Bone cyst Bone spur (Osteophytes One of the more prominent is osteoporosis. Osteoporosis is a Disease of Bone that leads to an increased risk of fracture.

Osteoporosis

Main article: Osteoporosis

Osteoporosis is a disease of bone - leading to an increased risk of fracture. Osteoporosis is a Disease of Bone that leads to an increased risk of fracture. A disease is an abnormal condition of an organism that impairs bodily functions and can be deadly A bone fracture (sometimes abbreviated # or Fx or Fx) is a medical condition in which a Bone is cracked or broken In osteoporosis, the bone mineral density (BMD) is reduced, bone microarchitecture is disrupted, and the amount and variety of non-collagenous proteins in bone is altered. Collagen is the main Protein of Connective tissue in Animals and the most abundant protein in Mammals making up about 50% of the whole-body protein Osteoporosis is defined by the World Health Organization (WHO) in women as a bone mineral density 2. 5 standard deviations below peak bone mass (20-year-old sex-matched healthy person average) as measured by DXA; the term "established osteoporosis" includes the presence of a fragility fracture. In Probability and Statistics, the standard deviation is a measure of the dispersion of a collection of values Dual energy X-ray absorptiometry ( DXA, previously DEXA is a means of measuring Bone mineral density (BMD In Traumatology, a fragility fracture is a Bone fracture that occurs as a result of a fall from standing height or less ^[3] Osteoporosis is most common in women after the menopause, when it is called postmenopausal osteoporosis, but may develop in men and premenopausal women in the presence of particular hormonal disorders and other chronic diseases or as a result of smoking and medications, specifically glucocorticoids, when the disease is called steroid- or glucocorticoid-induced osteoporosis (SIOP or GIOP). Menopause is the permanent shutting down of the female Reproductive system, a considerable length of time before the end of the lifespan In Medicine, a chronic disease is a Disease that is long-lasting or recurrent Tobacco Smoking is the inhalation of smoke from burned dried or cured leaves of the Tobacco plant most often in the form of a Cigarette. Medication, also referred to as medicine, can be loosely defined as any substance intended for use in the diagnosis cure mitigation treatment or prevention of disease Glucocorticoids (GC are a class of Steroid hormones characterised by an ability to bind with the glucocorticoid receptor ( GR) and trigger similar effects

Osteoporosis can be prevented with lifestyle advice and medication, and preventing falls in people with known or suspected osteoporosis is an established way to prevent fractures. Osteoporosis can be treated with bisphosphonates and various other medical treatments. In Pharmacology, bisphosphonates (also called diphosphonates) are a class of drugs that inhibit Osteoclast action and the resorption of bone

Other

Other disorders of bone include:

• Bone fracture
• Osteomyelitis
• Osteoporosis
• Osteosarcoma
• Osteogenesis imperfecta
• Arthritis

Osteology

The study of bones and teeth is referred to as osteology. A bone fracture (sometimes abbreviated # or Fx or Fx) is a medical condition in which a Bone is cracked or broken Osteomyelitis is an Infection of Bone or Bone marrow, usually caused by Pyogenic Bacteria or Mycobacteria. Osteoporosis is a Disease of Bone that leads to an increased risk of fracture. Osteosarcoma is the most common type of malignant Bone cancer, accounting for 35% of primary bone malignancies Osteogenesis imperfecta ( OI and sometimes known as Brittle Bone Disease) is a genetic bone disorder Arthritis (from Greek arthro-, joint + -itis, inflammation plural arthritides is a group of conditions involving damage to the Joints of the body Osteology is the scientific study of Bones. A Subdiscipline of Anthropology and Archeology, osteology is a detailed study It is frequently used in anthropology, archeology and forensic science for a variety of tasks. Anthropology (/ˌænθɹəˈpɒlədʒi/ from Greek grc ἄνθρωπος anthrōpos, "human" -λογία -logia) is the study of Archaeology, archeology, or archæology (from Greek grc ἀρχαιολογία archaiologia – grc ἀρχαῖος archaīos This can include determining the nutritional, health, age or injury status of the individual the bones were taken from. Preparing fleshed bones for these types of studies can involve maceration - boiling fleshed bones to remove large particles, then hand-cleaning. Maceration is a bone preparation technique whereby parts of a Vertebrate corpse are left to Rot inside a closed container at near-constant temperature to get

Typically anthropologists and archeologists study bone tools made by Homo sapiens and Homo neanderthalensis. Bone tools have been documented from the advent of Homo Sapiens and are also known from Homo Neanderthalis contexts Human beings, humans or man (Origin 1590–1600 L homō man OL hemō the earthly one (see Humus The Neanderthal (neɪˈændərtɑːl also with /niː-/ and /-θɔːl/ or Neandertal, is an extinct member of the Homo genus that is known from Bones can serve a number of uses such as projectile points or artistic pigments, and can be made from endoskeletal or external bones such as antler or tusk.

Alternatives to bony endoskeletons

There are several evolutionary alternatives to mammilary bone; though they have some similar functions, they are not completely functionally analogous to bone. eVolution is the third Album by eLDee, it was due to be released in 2008

• Exoskeletons offer support, protection and levers for movement similar to endoskeletal bone. An exoskeleton is an external Skeleton that supports and protects an animal's body in contrast to the internal Endoskeleton of for example a Human. Different types of exoskeletons include shells, carapaces (consisting of calcium compounds or silica) and chitinous exoskeletons. A carapace is a dorsal section of an Exoskeleton or shell in a number of animal groups Calcium (Ca2+ plays a vital role in the Anatomy, Physiology and Biochemistry of Organisms and of the cell, particularly The Chemical compound silicon dioxide, also known as silica or silox (from the Latin " Silex " is an Oxide Chitin ( C 8 H 13 O 5 N)n (ˈkaɪtən is a long-chain Polymer of a N-acetylglucosamine
• A true endoskeleton (that is, protective tissue derived from mesoderm) is also present in Echinoderms. An endoskeleton is an internal support structure of an Animal. Echinoderms (Phylum Echinodermata) are a phylum of marine Animals (including Sea stars) Porifera (sponges) possess simple endoskeletons that consist of calcareous or siliceous spicules and a spongin fiber network. The sponges or poriferans (from Latin porus "pore" and ferre "to bear" are Animals This article is about the skeletal structure See also Spicule (solar physics and Spicule (glass manufacture.

Exposed bone

Bone penetrating the skin and being exposed to the outside can be both a natural process in some animals, and due to injury:

• A deer's antlers are composed of bone
• Instead of teeth, The extinct predatory fish Dunkleosteus had sharp edges of hard exposed bone along its jaws
• A compound fracture occurs when the edges of a broken bone puncture the skin
• Though not strictly speaking exposed, a bird's beak is primarily bone covered in a layer of keratin

Terminology

Several terms are used to refer to features and components of bones throughout the body:

Several terms are used to refer to specific features of long bones:

See also

• List of bones of the human skeleton
• Terms for anatomical location
• Orthopaedics
• Chiropractic

Footnotes

References

• Katja Hoehn; Marieb, Elaine Nicpon. Human Anatomy & Physiology (7th Edition). San Francisco: Benjamin Cummings. ISBN 0805359095.  
• Netter, Frank H. (1987), Musculoskeletal system: anatomy, physiology, and metabolic disorders. Frank H Netter ( 25 April, 1906- 17 September, 1991) was an Artist, Physician, and most notably a leading Medical illustrator Summit, New Jersey: Ciba-Geigy Corporation ISBN 0914168886
• Bryan H. Derrickson; Tortora, Gerard J. (2005). Principles of anatomy and physiology. New York: Wiley. ISBN 0471689343.  

External links

• Review (including references) of piezoelectricity and bone remodelling
• A good basic overview of bone biology from the Science Creative Quarterly
• Bone Health at Got Bones?
• Osteopathic physicians