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Encyclopedia > Bone
Gray's Anatomy illustration of a human femur.
Gray's Anatomy illustration of a human femur.

Bones are rigid organs that form part of the endoskeleton of vertebrates. They function to move, support, and protect the various organs of the body, produce red and white blood cells and store minerals. 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. Other types of tissue found in bones include marrow, endosteum and periosteum, nerves, blood vessels and cartilage. There are 206 bones in the adult body and about 300 bones in the infant body. Osseous tissue, or bone tissue is the major structural and supportive connective tissue of the body. ... Look up bone in Wiktionary, the free dictionary. ... Image File history File links File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Image File history File links File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... An illustration from the 1918 edition Henry Grays Anatomy of the Human Body (or Grays Anatomy as it has more commonly become known) is an anatomy textbook widely regarded as a classic work on human anatomy. ... The femur or thigh bone is the longest, most voluminous, and strongest bone of the mammalian bodies. ... This article is about the biological unit. ... Endoskeleton of a swordfish An endoskeleton is an internal support structure of an animal. ... This article does not cite any references or sources. ... “Red cell” redirects here. ... White Blood Cells redirects here. ... Osseous tissue, or bone tissue is the major structural and supportive connective tissue of the body. ... For the Dir en grey album, see The Marrow of a Bone. ... Endosteum is the inner lining of the bone. ... The periosteum is an envelope of fibrous connective tissue that is wrapped around the bone in all places except at joints (which are protected by cartilage). ... For other uses, see Nerve (disambiguation). ... f you all 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. ...

Contents

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.
  • 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.
  • Mineral storage — Bones act as reserves of minerals important for the body, most notably calcium and phosphorus.
  • 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. The interaction between bone and muscle is studied in biomechanics.
  • 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.[citation needed]
  • Sound transduction — Bones are important in the mechanical aspect of hearing.

For other uses of Skull, see Skull (disambiguation). ... For other uses, see Brain (disambiguation). ... The human rib cage. ... The heart and lungs, from an older edition of Grays Anatomy. ... The heart and lungs (from an older edition of Grays Anatomy) The lung is an organ belonging to the respiratory system and interfacing to the circulatory system of air-breathing vertebrates. ... For the Dir en grey album, see The Marrow of a Bone. ... The medullary cavity is the central cavity of bone shafts where yellow marrow (adipose tissue) is stored. ... Diagram that shows the development of different blood cells from hematopoietic stem cell to mature cells Haematopoiesis (from Ancient Greek: haima blood; poiesis to make) (or hematopoiesis in the United States; sometimes also haemopoiesis or hemopoiesis) is the formation of blood cellular components. ... For other uses, see Calcium (disambiguation). ... General Name, symbol, number phosphorus, P, 15 Chemical series nonmetals Group, period, block 15, 3, p Appearance waxy white/ red/ black/ colorless Standard atomic weight 30. ... A top-down view of skeletal muscle Skeletal muscle is a type of striated muscle, usually attached to the skeleton. ... A tendon or sinew is a tough band of fibrous connective tissue, attached on one end to a muscle and on the other to a bone. ... In anatomy, the term ligament is used to denote three different types of structures:[1] Fibrous tissue that connects bones to other bones. ... For other uses, see Joint (disambiguation). ... For other uses, see Biomechanical. ... For other uses, see Heavy metal (disambiguation). ... Hearing (or audition) is one of the traditional five senses, and refers to the ability to detect sound. ...

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). It has relatively high compressive strength but poor tensile strength, meaning it resists pushing forces well, but not pulling forces. While bone is essentially brittle, it does have a significant degree of elasticity, contributed chiefly by collagen. All bones consist of living cells embedded in the mineralized organic matrix that makes up the osseous tissue. Osseous tissue, or bone tissue is the major structural and supportive connective tissue of the body. ... The Rockwell scale characterizes the indentation hardness of materials through the depth of penetration of an indenter, loaded on a material sample and compared to the penetration in some reference material. ... A cloth of woven carbon fiber filaments, a common element in composite materials Composite materials (or composites for short) are engineered materials made from two or more constituent materials with significantly different physical or chemical properties and which remain separate and distinct on a macroscopic level within the finished structure. ... Calcium phosphate is the name given to a family of minerals containing calcium ions (Ca2+) together with orthophosphates (PO43-), metaphosphates or pyrophosphates (P2O74-) and occasionally hydrogen or hydroxide ions. ... Hydroxylapatite is a naturally occurring form of calcium apatite with the formula Ca5(PO4)3(OH), but is usually written Ca10(PO4)6(OH)2 to denote that the crystal unit cell comprises two molecules. ... Osseous tissue, or bone tissue is the major structural and supportive connective tissue of the body. ... Compressive strength is the capacity of a material to withstand axially directed pushing forces. ... Tensile strength isthe measures the force required to pull something such as rope, wire, or a structural beam to the point where it breaks. ... Elasticity is a branch of physics which studies the properties of elastic materials. ... Tropocollagen triple helix. ... Drawing of the structure of cork as it appeared under the microscope to Robert Hooke from Micrographia which is the origin of the word cell being used to describe the smallest unit of a living organism Cells in culture, stained for keratin (red) and DNA (green) The cell is the...


Masto-structure

Gross anatomy

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

The lesser pelvis (or true pelvis) is that part of the pelvic cavity which is situated below and behind the pelvic brim. ... The lesser pelvis (or true pelvis) is that part of the pelvic cavity which is situated below and behind the pelvic brim. ... The pelvis is divided by an oblique plane passing through the prominence of the sacrum, the arcuate and pectineal lines, and the upper margin of the symphysis pubis, into the greater pelvis and the lesser pelvis. ... The lower circumference of the lesser pelvis is very irregular; the space enclosed by it is named the inferior aperture or outlet (apertura pelvis [minoris] inferior), and is bounded behind by the point of the coccyx, and laterally by the ischial tuberosities. ... The greater pelvis (or false pelvis) is the expanded portion of the cavity situated above and in front of the pelvic brim. ...

Individual bones

Bone is not a uniformly solid material, but rather has some spaces between its hard elements.

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)
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)

Image File history File links Illu_compact_spongy_bone. ...

Compact bone

The hard outer layer of bones is composed of compact bone tissue, so-called due to its minimal gaps and spaces. 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. Cortical bone, also known as compact bone is one of two main types of osseous tissues. ...


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. Trabecular bone accounts for the remaining 20% of total bone mass, but has nearly ten times the surface area of compact bone. Cancellous bone (or trabecular bone, or spongy bone) is a spongy type of bone with a very high surface area, found at the ends 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%. The term porosity is used in multiple fields including manufacturing, earth sciences and construction. ...


Cellular structure

There are several types of cells constituting the bone;

  • Osteoblasts are mononucleate bone-forming cells which descend from osteoprogenitor cells. They are located on the surface of osteoid seams and make a protein mixture known as osteoid, which mineralizes to become bone. Osteoid is primarily composed of Type I collagen. Osteoblasts also manufacture hormones, such as prostaglandins, to act on the bone itself. They robustly produce alkaline phosphatase, an enzyme that has a role in the mineralisation of bone, as well as many matrix proteins. 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. 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). 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. 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.

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. ... Osteoid is a protein mixture which is secreted by osteoblasts. ... Tropocollagen triple helix. ... For other uses, see Hormone (disambiguation). ... E1 - Alprostadil I2 - Prostacyclin 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. ... Ball and stick model of alkaline phosphatase Alkaline phosphatase (ALP) (EC 3. ... Illustration depicting extracellular matrix (basement membrane and interstitial matrix) in relation to epithelium, endothelium and connective tissue In biology, the extracellular matrix (ECM) is the extracellular part of animal tissue that usually provides structural support to the cells in addition to performing various other important functions. ... An osteocyte, a star-shaped cell, is the most abundant cell found in bone. ... An osteoclast (from the Greek words for bone and broken) is a type of bone cell that removes bone tissue by removing the bones 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. ... Monocyte A monocyte is a leukocyte, part of the human bodys immune system that protects against blood-borne pathogens and moves quickly (aprox. ... Mouse embryonic stem cells with fluorescent marker. ... Macrophages (Greek: big eaters) are cells found in tissues that are responsible for phagocytosis of pathogens, dead cells and cellular debris. ... Tartrate resistant acid phosphatase is a glycosylated monomeric metalloenzyme expressed in mammals (1). ...

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. The matrix is initially laid down as unmineralized osteoid (manufactured by osteoblasts). Mineralisation involves osteoblasts secreting vesicles containing alkaline phosphatase. 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. Hydroxylapatite is a naturally occurring form of calcium apatite with the formula Ca5(PO4)3(OH), but is usually written Ca10(PO4)6(OH)2 to denote that the crystal unit cell comprises two molecules. ... In cell biology, a vesicle is a relatively small and enclosed compartment, separated from the cytosol by at least one lipid bilayer. ...


Organic

The organic part of matrix is mainly composed of Type I collagen. This is synthesised intracellularly as tropocollagen and then exported. It then associates into fibrils. 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. 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. Tropocollagen triple helix. ... Fibril is a fine fiber approximately 1 nm in diameter. ... Chondroitin sulfate Hyaluronan Glycosaminoglycans (GAGs) or mucopolysaccharides are long unbranched polysaccharides consisting of a repeating disaccharide unit. ... Osteocalcin is a protein found in bone and dentin; that plays a role in mineralization and calcium ion homeostasis ... Osteonectin is a glycoprotein in the bone that binds calcium. ... Bone sialo protein is also known as BSP, it is one of the proteins for gene expression of bone Categories: Biology stubs ...


Woven or lamellar

Collagen fibres of woven bone
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. 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. 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." Image File history File links Woven_bone_matrix. ... Image File history File links Woven_bone_matrix. ... // Mathmatics In mathematics, the term torsion has several meanings, mostly unrelated to each other. ... Cartilage is a type of dense connective tissue. ...


Five types of bones

There are five types of bones in the human body: long, short, flat, irregular and sesamoid. Image File history File links Illu_long_bone. ...

  • Short bones are roughly cube-shaped, and have only a thin layer of compact bone surrounding a spongy interior. The bones of the wrist and ankle are short bones, as are the sesamoid bones.
  • Flat bones are thin and generally curved, with two parallel layers of compact bones sandwiching a layer of spongy bone. Most of the bones of the skull are flat bones, as is the sternum.
  • Irregular bones do not fit into the above categories. 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. 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

The long bones are those that are longer than they are wide, and grow primarily by elongation of the diaphysis at an epiphysis at one end of the growing bone. ... The diaphysis is the main or mid section (shaft) of a long bone. ... Cortical bone, also known as compact bone is one of two main types of osseous tissues. ... For the Dir en grey album, see The Marrow of a Bone. ... The medullary cavity is the central cavity of bone shafts where yellow marrow (adipose tissue) is stored. ... Cancellous bone (or trabecular bone, or spongy bone) is a spongy type of bone with a very high surface area, found at the ends of long bones. ... The metacarpus is the intermediate part of the hand skeleton that is located between the fingers distally and the carpus which forms the connection to the forearm. ... The metatarsus consists of the five long bones of the foot, which are numbered from the medial side (ossa metatarsalia I.-V.); each presents for examination a body and two extremities. ... In human anatomy, the carpal bones are the bones of the human wrist. ... FIG. 268– Bones of the right foot. ... For other uses, see Patella (disambiguation). ... Where a part of the skeleton is intended for strength and compactness combined with limited movement, it is constructed of a number of short bones, as in the carpus and tarsus. ... In anatomy, a sesamoid bone is a bone embedded within a tendon. ... Flat Bones. ... For other uses of Skull, see Skull (disambiguation). ... The sternum (from Greek στέρνον, sternon, chest) or breastbone is a long, flat bone located in the center of the thorax (chest). ... The irregular bones are such as, from their peculiar form, cannot be grouped as long bone, short bone, or flat bone. ... In anatomy, a sesamoid bone is a bone embedded within a tendon. ... The pisiform bone (also called pisiform or pisiforme os or lentiform bone) is a small knobbly, pea-shaped wrist bone. ...

Formation

The formation of bone during the fetal stage of development occurs by two processes: intramembranous and endochondral ossification. Osteoblasts and osteoclasts on trabecula of lower jaw of calf embryo. ... Section of fetal bone of cat. ...


Intramembranous ossification mainly occurs during formation of the flat bones of the skull; the bone is formed from mesenchyme tissue. The steps in intramembranous ossification are: For other uses of Skull, see Skull (disambiguation). ... Mesenchyme (also known as embryonic connective tissue) is the mass of tissue that develops mainly from the mesoderm (the middle layer of the trilaminar germ disc) of an embryo. ...

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

Endochondral ossification

Endochondrial 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: Image File history File links Illu_bone_growth. ... Image File history File links Illu_bone_growth. ...

  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." 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). 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). The long bones are those that are longer than they are wide, and grow primarily by elongation of the diaphysis at an epiphysis at one end of the growing bone. ... The long bones are those that are longer than they are wide, and grow primarily by elongation of the diaphysis at an epiphysis at one end of the growing bone. ...


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. 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. For the Dir en grey album, see The Marrow of a Bone. ...


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 signalling is a form of signalling in which the target cell is close to the signal releasing cell, and the signal chemical is broken down too quickly to be carried to other parts of the body. ...


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.[1] The term Exercise can refer to: Physical exercise such as running or strength training Exercise (options), the financial term for enacting and terminating a contract Category: ... Wolffs law is a theory developed by the German Anatomist/Surgeon Julius Wolff (1835-1902) in the 19th century that states that bone in a healthy person or animal will adapt to the loads it is placed under. ... Piezoelectricity is the ability of some materials (notably crystals and certain ceramics) to generate an electric potential[1] in response to applied mechanical stress. ...


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. The cells also use paracrine signalling to control the activity of each other. 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 the bones mineralized matrix. ... Ribbon diagram of the enzyme TIM, surrounded by the space-filling model of the protein. ... Paracrine signaling is a form of cell signaling in which the target cell is close to (para = alongside of or next to, but this strict prefix definition is not meticulously followed here) 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 a protein mixture which is secreted by osteoblasts. ... HIV protease in a complex with the protease inhibitor ritonavir. ... 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). These hormones also promote increased secretion of osteoprotegerin.[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. 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. 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. Growth hormone (GH) or somatotropin (STH) is a protein hormone which stimulates growth and cell reproduction in humans and other animals. ... Located at the base of the skull, the pituitary gland is protected by a bony structure called the sella turcica. ... thyroxine (T4) triiodothyronine (T3) Thyroxine, T4 Triiodothyronine, T3 The thyroid hormones, thyroxine (T4) and triiodothyronine (T3), are tyrosine-based hormones produced by the thyroid gland. ... Estriol. ... 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 characteristics in vertebrates by binding to androgen receptors. ... Cytokines are a category of less-widely-known signalling proteins and glycoproteins that, like hormones and neurotransmitters, are used extensively in cellular communication. ... Vitamin D is a fat soluble vitamin that contributes to the maintenance of normal levels of calcium and phosphorus in the bloodstream. ... RNA expression pattern Orthologs Human Mouse Entrez Ensembl Uniprot na Refseq Location Pubmed search Parathyroid hormone (PTH), or parathormone, is secreted by the parathyroid glands as a polypeptide containing 84 amino acids. ... In chemistry, a ligand is an atom, ion, or molecule (see also: functional group) that generally donates one or more of its electrons through a coordinate covalent bond to, or shares its electrons through a covalent bond with, one or more central atoms or ions (these ligands act as a... Interleukin-6 (IL-6) is a pro-inflammatory cytokine secreted by T cells and macrophages to stimulate immune response to trauma, especially burns or other tissue damage leading to inflammation. ...


Osteoclast inhibition

The rate at which osteoclasts resorb bone is inhibited by calcitonin and osteoprotegerin. Calcitonin is produced by parafollicular cells in the thyroid gland, and can bind to receptors on osteoclasts to directly inhibit osteoclast activity. Osteoprotegerin is secreted by osteoblasts and is able to bind RANK-L, inhibiting osteoclast stimulation.[2] Calcitonin is a 32 amino acid polypeptide hormone that is produced in humans primarily by the parafollicular (also known as C) cells of the thyroid, and in many other animals in the ultimobranchial body. ... Parafollicular cells also called C cells, are cells in the thyroid which produce and secrete calcitonin. ... The thyroid gland and its relations In anatomy, the thyroid (IPA θaɪɹoɪd) is an endocrine gland. ...


Disorders

See also: List of skeletal disorders

There are many disorders of the skeleton. One of the more prominent is osteoporosis. This is a list of skeletal disorders, these affect the development and structure of the skeletal system. ... 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. 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. 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.[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). Osteoporosis is a disease of bone that leads to an increased risk of fracture. ... This article is about the medical term. ... Internal and external views of an arm with a compound fracture, both before and after surgery A bone fracture is a medical condition in which a bone has cracked or broken. ... A bone mineral density (BMD) test, also called a bone mass measurement, is used to measure bone density and determine fracture risk for osteoporosis. ... Tropocollagen triple helix. ... WHO redirects here. ... In probability and statistics, the standard deviation of a probability distribution, random variable, or population or multiset of values is a measure of statistical dispersion of its values. ... A scanner used to measure bone density with dual energy X-ray absorptiometry. ... A fragility fracture is one that occurs as a result of a fall from standing height or less. ... The word menopause literally means the permanent physiological, or natural, cessation of menstrual cycles, from the Greek roots meno (month) and pausis (a pause, a cessation). ... In medicine, a chronic disease is a disease that is long-lasting or recurrent. ... The cigarette is the most common method of smoking tobacco. ... A medication is a drug or substance taken to reduce symptoms or cure an illness or medical condition. ... Glucocorticoids are a class of steroid hormones characterised by an ability to bind with the cortisol receptor 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) is a class of drugs that inhibits the resorption of bone. ...


Other

Other disorders of bone include:

Internal and external views of an arm with a compound fracture, both before and after surgery A bone fracture is a medical condition in which a bone has cracked or broken. ... Osteomyelitis is an infection of bone, 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 where there is damage caused to the joints of the body. ...

Osteology

The study of bones and teeth is referred to as osteology. It is frequently used in anthropology, archeology and forensic science for a variety of tasks. 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. Osteology is the scientific study of bones. ... This article is about the social science. ... Archaeology or sometimes in American English archeology (from the Greek words αρχαίος = ancient and λόγος = word/speech) is the study of human cultures through the recovery, documentation and analysis of material remains, including architecture, artefacts, biofacts, human remains, and landscapes. ... The word forensic (from Latin: forensis - forum) refers to something of, pertaining to, or used in a court of law. ... 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 a clean skeleton. ...


Typically anthropologists and archeologists study bone tools made by Homo sapiens and Homo neanderthalensis. 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. Bone tools have been documented from the advent of Homo Sapiens and are also known from Homo Neanderthalis contexts. ... This article is about modern humans. ... For other uses, see Neanderthal (disambiguation). ...


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. This article is about evolution in biology. ...

An exoskeleton is an external anatomical feature that supports and protects an animals body, in contrast to the internal endoskeleton of, for example, a human. ... Various seashells Danielle A shell is the hard, rigid outer covering, or integument, allanimals. ... The term carapace refers to 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 in signal transduction pathways. ... The chemical compound silicon dioxide, also known as silica, is the oxide of silicon, chemical formula SiO2. ... Structure of the chitin molecule, showing two of the N-Acetylglucosamine units that repeat to form long chains in beta-1,4 linkage. ... Endoskeleton of a swordfish An endoskeleton is an internal support structure of an animal. ... Subphyla & Classes Homalozoa Gill & Caster, 1960 Homostelea Homoiostelea Stylophora † Ctenocystoidea Robison & Sprinkle, 1969 Crinozoa Crinoidea Paracrinoidea † Regnéll, 1945 Cystoidea †von Buch, 1846 Asterozoa Ophiuroidea Asteroidea Echinozoa Echinoidea Holothuroidea Ophiocistioidea Helicoplacoidea † Arkarua † Homalozoa † Pelmatozoa † Edrioasteroidea † Blastozoa † Blastoidea † Eocrinoidea †Jaekel, 1899 † = extinct Echinoderms (Phylum Echinodermata, from the Greek for spiny skin... The sponge, in the phylum Porifera, is a very primitive and specialized animal. ... Spicules Spicules are skeletal structures that occur in most sponges. ...

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

For the Poet Laureate of Milwaukee, see Antler (Poet). ... Binomial name (Newberry, 1873) Dunkleosteus (formerly known as Dinichthys) was a large Placoderm (armoured prehistoric fish) that lived in the late Devonian period, about 360 – 415 million years ago. ... Internal and external views of an arm with a compound fracture, both before and after surgery A bone fracture is a medical condition in which a bone has cracked or broken. ... The beak, bill or rostrum is an external anatomical structure of birds which, in addition to eating, is used for grooming, manipulating objects, killing prey, probing for food, courtship, and feeding their young. ... Not to be confused with kerogen or carotene. ...

Terminology

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

Bone feature Definition
articular process A projection that contacts an adjacent bone.
articulation The region where adjacent bones contact each other—a joint.
canal A long, tunnel-like foramen, usually a passage for notable nerves or blood vessels.
condyle A large, rounded articular process.
crest A prominent ridge.
eminence A relatively small projection or bump.
epicondyle A projection near to a condyle but not part of the joint.
facet A small, flattened articular surface.
foramen An opening through a bone.
fossa A broad, shallow depressed area.
fovea A small pit on the head of a bone.
labyrinth A cavity within a bone.
line A long, thin projection, often with a rough surface. Also known as a ridge.
malleolus One of two specific protuberances of bones in the ankle.
meatus A short canal.
process A relatively large projection or prominent bump.(gen.)
ramus An arm-like branch off the body of a bone.
sinus A cavity within a cranial bone.
spine A relatively long, thin projection or bump.
suture Articulation between cranial bones.
trochanter One of two specific tuberosities located on the femur.
tubercle A projection or bump with a roughened surface, generally smaller than a tuberosity.
tuberosity A projection or bump with a roughened surface.

Several terms are used to refer to specific features of long bones: For other uses, see Joint (disambiguation). ... For a review of anatomical terms, see Anatomical position and Anatomical terms of location. ... The femur or thigh bone is the longest, most voluminous, and strongest bone of the mammalian bodies. ...

Bone feature Definition
diaphysis The long, relatively straight main body of a long bone; region of primary ossification. Also known as the shaft.
epiphysis The end regions of a long bone; regions of secondary ossification.
epiphyseal plate Also known as the growth plate or physis. In a long bone it is a thin disc of hyaline cartilage that is positioned transversely between the epiphysis and metaphysis. In the long bones of humans, the epiphyseal plate disappears by twenty years of age.
head The proximal articular end of the bone.
metaphysis The region of a long bone lying between the epiphysis and diaphysis.
neck The region of bone between the head and the shaft.

See also

A typical adult human skeleton consists of the following 206 bones depending on age, though this number does vary owing to a variety of anatomical variations; for example, a small portion of the human population have an extra rib, or an extra lumbar vertebra. ... In zootomy, several terms are used to describe the location of organs and other structures in the body of bilateral animals. ... This fracture of the lower cervical vertebrae, known as a teardrop fracture is one of the conditions treated by orthopaedic surgeons. ... Chiropractic (from Greek chiros and praktikos meaning done by hand) is a health care profession whose purpose is to diagnose and treat mechanical disorders of the spine and musculoskeletal system with the intention of affecting the nervous system and improving health. ...

Footnotes

  1. ^ Netter, p. 187-189, A scholarly review.
  2. ^ a b Boulpaep, Emile L.; Boron, Walter F. (2005). Medical physiology: a cellular and molecular approach. Philadelphia: Saunders, p.1089-1091. ISBN 1416023283. 
  3. ^ WHO (1994). "Assessment of fracture risk and its application to screening for postmenopausal osteoporosis. Report of a WHO Study Group". World Health Organization technical report series 843: 1–129. PMID 7941614. 

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. 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. 

Dr. Frank H. Netter (25 April, 1906-17 September 1991) was an artist, physician, and most notably, a leading medical illustrator. ...

External links

The sphenoidal sinuses (or sphenoid) contained within the body of the sphenoid vary in size and shape; owing to the lateral displacement of the intervening septum they are rarely symmetrical. ... The greater wing of the sphenoid bone, or ali-sphenoid, is a bony process of the sphenoid bone; there is one on each side, extending from the side of the body of the sphenoid and curving upward, laterally, and backwards. ... At th anterior and medial part of the Sphenoid is a circular aperture, the foramen rotundum, for the transmission of the maxillary nerve. ... At the base of the skull the foramen ovale is a hole that transmits the mandibular nerve, the otic ganglion, the accessory meningeal artery, emissary veins (from the cavernous sinus to the pterygoid plexus) and the lesser superficial petrosal nerve. ... In the base of the skull, in the great wings of the sphenoid bone, medial to the foramen ovale, a small aperture, the sphenoidal emissary foramen, may occasionally be seen (it is often absent) opposite the root of the pterygoid process. ... The foramen spinosum is the foramen in the skull that permits the passage of the middle meningeal artery. ... The great wings, or ali-sphenoids, are two strong processes of bone, which arise from the sides of the body, and are curved upward, lateralward, and backward; the posterior part of each projects as a triangular process which fits into the angle between the squama and the petrous portion of... The lateral surface of the great wing is convex, and divided by a transverse ridge, the infratemporal crest, into two portions. ... The lesser wings of the sphenoid or orbito-sphenoids are two thin triangular plates, which arise from the upper and anterior parts of the body, and, projecting lateralward, end in sharp points [Fig. ... 1 Foramen ethmoidale, 2 Canalis opticus, 3 Fissura orbitalis superior, 4 Fossa sacci lacrimalis, 5 Sulcus infraorbitalis, 6 Fissura orbitalis inferior, 7 Foramen infraorbitale The superior orbital fissure is a foramen in the skull, although strictly it is more of a cleft, lying between the lesser and greater wings of... In the sphenoid bone, the posterior border, smooth and rounded, is received into the lateral fissure of the brain; the medial end of this border forms the anterior clinoid process, which gives attachment to the tentorium cerebelli; it is sometimes joined to the middle clinoid process by a spicule of... optical canal information ... The pterygoid processes of the sphenoid, one on either side, descend perpendicularly from the regions where the body and great wings unite. ... The Pterygoid fossa, or the sphenoid bone is wedged between several other bones in the front of the cranium. ... In the pterygoid processes of the sphenoid, above the pterygoid fossa is a small, oval, shallow depression, the scaphoid fossa, which gives origin to the Tensor veli palatini. ... The lateral pterygoid plate of the sphenoid (or lateral lamina of pterygoid process) is broad, thin, and everted; its lateral surface forms part of the medial wall of the infratemporal fossa, and gives attachment to the Pterygoideus externus; its medial surface forms part of the pterygoid fossa, and gives attachment... The medial pterygoid plate of the sphenoid is narrower and longer than the lateral pterygoid plate; it curves lateralward at its lower extremity into a hook-like process, the pterygoid hamulus, around which the tendon of the Tensor veli palatini glides. ... The pterygoid canal (also vidian canal) is a passage in the skull leading from just anterior to the foramen lacerum in the middle cranial fossa to the pterygopalatine fossa. ... The medial pterygoid plate of the sphenoid curves lateralward at its lower extremity into a hook-like process, the pterygoid hamulus, around which the tendon of the Tensor veli palatini glides. ... The body of the sphenoid bone, more or less cubical in shape, is hollowed out in its interior to form two large cavities, the sphenoidal air sinuses, which are separated from each other by a septum. ... The sphenoidal conchae (sphenoidal turbinated processes) are two thin, curved plates, situated at the anterior and lower part of the body of the sphenoid. ... Your skull is in your back (this is obviously not true, I was just testing the website to see if it really works) The ethmoid bone (os ethmoidale) is a bone in the skull that separates the nasal cavity from the brain. ... The cribriform plate of the ethmoid bone (horizontal lamina) [Fig. ... The crista galli (Latin: crest of the cock) is a median ridge of bone that projects from the cribriform plate of the ethmoid bone. ... Bones and cartilages of septum of nose. ... In the ethmoid bone, a curved lamina, the uncinate process, projects downward and backward from this part of the labyrinth; it forms a small part of the medial wall of the maxillary sinus, and articulates with the ethmoidal process of the inferior nasal concha. ... The back part of the medial surface of the labyrinth of ethmoid is subdivided by a narrow oblique fissure, the superior meatus of the nose, bounded above by a thin, curved plate, the superior nasal concha. ... The superior meatus, the smallest of the three meatuses of the nose, occupies the middle third of the lateral wall. ... The medial surface of the labyrinth of ethmoid consists of a thin lamella, which descends from the under surface of the cribriform plate, and ends below in a free, convoluted margin, the middle nasal concha. ... The middle meatus is situated between the middle and inferior conchæ, and extends from the anterior to the posterior end of the latter. ... The Labyrinth or Lateral Mass of the ethmoid bone consists of a number of thin-walled cellular cavities, the ethmoidal cells, arranged in three groups, anterior, middle, and posterior, and interposed between two vertical plates of bone; the lateral plate forms part of the orbit, the medial, part of the... ethmoidal sinuses can be divided into 3: a) anterior b) middle c) posterior except the posterior ethmoidal sinus, all the ethmoidal sinuses will drain into middle meateus. ... Lateral to either olfactory groove are the internal openings of the anterior and posterior ethmoidal foramina (or canals). ... Lateral to either olfactory groove are the internal openings of the anterior and posterior ethmoidal foramina (or canals). ...

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