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70-634: The site was discovered in 1986, when a cultural layer of unearthed animal bones , charcoal , and stone tools was discovered. The layer was 180 centimeters below the ground, which is covered with lake deposits such as thick black and gray silt clay. Three archeological excavations have been carried out so far by institutions such as the Department of Archaeology in Peking University , the Department of History in Hebei University ,

140-456: A building or structure in China is a stub . You can help Misplaced Pages by expanding it . Bone A bone is a rigid organ that constitutes part of the skeleton in most vertebrate animals. Bones protect the various other organs of the body, produce red and white blood cells , store minerals , provide structure and support for the body, and enable mobility . Bones come in

210-440: A bone experiences within long bones such as the femur . As far as short bones are concerned, trabecular alignment has been studied in the vertebral pedicle . Thin formations of osteoblasts covered in endosteum create an irregular network of spaces, known as trabeculae. Within these spaces are bone marrow and hematopoietic stem cells that give rise to platelets , red blood cells and white blood cells . Trabecular marrow

280-479: A long bone are separated by a growing zone of cartilage (the epiphyseal plate ). At 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). In the upper limbs, only the diaphyses of the long bones and scapula are ossified. The epiphyses, carpal bones, coracoid process, medial border of the scapula, and acromion are still cartilaginous. The following steps are followed in

350-509: A mineralized organic matrix. The primary inorganic component of human bone is hydroxyapatite , the dominant bone mineral , having the nominal composition of Ca 10 (PO 4 ) 6 (OH) 2 . The organic components of this matrix consist mainly of type I collagen —"organic" referring to materials produced as a result of the human body—and inorganic components, which alongside the dominant hydroxyapatite phase, include other compounds of calcium and phosphate including salts. Approximately 30% of

420-419: A more fulfilling and healthier lifestyle. Bone is constantly being created and replaced in a process known as remodeling . This ongoing turnover of bone is a process of resorption followed by replacement of bone with little change in shape. This is accomplished through osteoblasts and osteoclasts. Cells are stimulated by a variety of signals , and together referred to as a remodeling unit. Approximately 10% of

490-457: A number of anatomical terms to describe the appearance, shape and function of bones. Other anatomical terms are also used to describe the location of bones . Like other anatomical terms, many of these derive from Latin and Greek . Some anatomists still use Latin to refer to bones. The term "osseous", and the prefix "osteo-", referring to things related to bone, are still used commonly today. Some examples of terms used to describe bones include

560-422: A number of chemical enzymes that either promote or inhibit the activity of the bone remodeling 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. For example, the rate at which osteoclasts resorb bone is inhibited by calcitonin and osteoprotegerin . Calcitonin is produced by parafollicular cells in

630-529: A positive correlation between the adaptations of resistance training and bone density. While nutritional and pharmacological approaches may also improve bone health, the strength and balance adaptations from resistance training are a substantial added benefit. Weight-bearing exercise may assist in osteoblast (bone-forming cells) formation and help to increase bone mineral content. High-impact sports, which involve quick changes in direction, jumping, and running, are particularly effective with stimulating bone growth in

700-419: A recent study, there was a strong correlation between calcium intake and BMD across a variety of diverse populations of children and adolescence ultimately coming to the conclusion that fundamentally, achieving optimal bone health is necessary for providing our youth with the ability to undergo hormonal changes as well. They found in a study of over 10,000 children ages 8-19 that in females, African Americans, and

770-466: A shaft (tubular diaphysis), but since they're smaller than typical long bones, they're called “miniature, small or short" long bones. Nevertheless, others consider the patellae and other sesamoid bones, the vertebral bodies , the bones of the skull base and even the phalanges to be short bones. The carpus and tarsus consist of cancellous tissue covered by a thin crust of compact substance . Short bones are specialized to provide support in areas of

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840-408: A smaller number of randomly oriented collagen fibers, but forms quickly; it is for this appearance of the fibrous matrix that the bone is termed woven . It is soon replaced by lamellar bone, which is highly organized in concentric sheets with a much lower proportion of osteocytes to surrounding tissue. Lamellar bone, which makes its first appearance in humans in the fetus during the third trimester,

910-401: A strong nutritional plan with adequate amounts of Calcium sources can lead to strong bones but also can be a worth-while strategy into preventing further damage or degradation of bone stores as we age. The connection between Calcium intake & BMD and its effects on youth as a whole is a very world-wide issue and has been shown to affect different ethnicities in a variety of differing ways. In

980-577: A variety of doctors, including rheumatologists for joints, and orthopedic surgeons, who may conduct surgery to fix broken bones. Other doctors, such as rehabilitation specialists may be involved in recovery, radiologists in interpreting the findings on imaging, and pathologists in investigating the cause of the disease, and family doctors may play a role in preventing complications of bone disease such as osteoporosis. Short bone Short bones are designated as those bones that are more or less equal in length, width, and thickness. They include

1050-416: A variety of shapes and sizes and have complex internal and external structures. They are lightweight yet strong and hard and serve multiple functions . Bone tissue (osseous tissue), which is also called bone in the uncountable sense of that word, is hard tissue , a type of specialised connective tissue . It has a honeycomb -like matrix internally, which helps to give the bone rigidity. Bone tissue

1120-456: A very low shear stress strength (51.6 MPa). This means that bone resists pushing (compressional) stress well, resist pulling (tensional) stress less well, but only poorly resists shear stress (such as due to torsional loads). While bone is essentially brittle , bone does have a significant degree of elasticity , contributed chiefly by collagen . Mechanically, bones also have a special role in hearing . The ossicles are three small bones in

1190-441: Is mineralized tissue of two types, cortical bone and cancellous bone . Other types of tissue found in bones include bone marrow , endosteum , periosteum , nerves , blood vessels and cartilage . In the human body at birth, approximately 300 bones are present. Many of these fuse together during development, leaving a total of 206 separate bones in the adult, not counting numerous small sesamoid bones . The largest bone in

1260-474: Is called "osteoid". Around and inside collagen fibrils calcium and phosphate eventually precipitate within days to weeks becoming then fully mineralized bone with an overall carbonate substituted hydroxyapatite inorganic phase. In order to mineralise the bone, the osteoblasts secrete alkaline phosphatase, some of which is carried by vesicles . This cleaves the inhibitory pyrophosphate and simultaneously generates free phosphate ions for mineralization, acting as

1330-418: Is composed of a network of rod- and plate-like elements that make the overall organ lighter and allow 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. The words cancellous and trabecular refer to the tiny lattice-shaped units (trabeculae) that form the tissue. It was first illustrated accurately in

1400-589: Is less common to see, the necessity for a healthy routine especially when it comes to bone development is essential in our youth. Children that naturally have lower bone mineral density have a lower quality of life and therefore lead a life that is less fulfilling and uncomfortable. Factors such as increases in Calcium intake has been shown to increase BMD stores. Studies have shown that increasing calcium stores whether that be through supplementation or intake via foods and beverages such as leafy greens and milk have pushed

1470-492: Is made up of different types of bone cells . Osteoblasts and osteocytes are involved in the formation and mineralisation of bone; osteoclasts are involved in the resorption of bone tissue. Modified (flattened) osteoblasts become the lining cells that form a protective layer on the bone surface. The mineralised matrix of bone tissue has an organic component of mainly collagen called ossein and an inorganic component of bone mineral made up of various salts. Bone tissue

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1540-518: Is mostly found in the bone marrow of the femur, the ribs, the vertebrae and pelvic bones . Bone receives about 10% of cardiac output. Blood enters the endosteum , flows through the marrow, and exits through small vessels in the cortex. In humans, blood oxygen tension in bone marrow is about 6.6%, compared to about 12% in arterial blood, and 5% in venous and capillary blood. Bone is metabolically active tissue composed of several types of cells. These cells include osteoblasts , which are involved in

1610-527: Is necessary during our childhood as these factors lead to a supportive and healthy lifestyle/bone health. Up till the age of 30, the bone stores that we have will ultimately start to decrease as we surpass this age. Influencing factors that can help us have larger stores and higher amounts of BMD will allow us to see less harmful results as we reach older adulthood. The issue of having fragile bones during our childhood leads to an increase in certain disorders and conditions such as juvenile osteoporosis , though it

1680-455: Is not fully known. Two types of bone can be identified microscopically according to the arrangement of collagen: woven and lamellar. Woven bone is produced when osteoblasts produce osteoid rapidly, which occurs initially in all fetal bones, but is later replaced by more resilient lamellar bone. In adults, woven bone is created after fractures or in Paget's disease . Woven bone is weaker, with

1750-403: Is not uniformly solid, but consists of a flexible matrix (about 30%) and bound minerals (about 70%), which are intricately woven and continuously remodeled by a group of specialized bone cells. Their unique composition and design allows bones to be relatively hard and strong, while remaining lightweight. Bone matrix is 90 to 95% composed of elastic collagen fibers, also known as ossein, and

1820-730: 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. Osteoblasts can also be induced to secrete a number of cytokines that promote reabsorption 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 reabsorption of bone by osteoclasts. These same compounds also increase secretion of macrophage colony-stimulating factor by osteoblasts, which promotes

1890-561: Is stronger and filled with many collagen fibers parallel to other fibers in the same layer (these parallel columns are called osteons). In cross-section , the fibers run in opposite directions in alternating layers, much like in plywood , assisting in the bone's ability to resist torsion forces. After a fracture, woven bone forms initially and is gradually replaced by lamellar bone during a process known as "bony substitution". Compared to woven bone, lamellar bone formation takes place more slowly. The orderly deposition of collagen fibers restricts

1960-448: Is the osteon . Cancellous bone or spongy bone , also known as trabecular bone , is the internal tissue of the skeletal bone and is an open cell porous network that follows the material properties of biofoams . Cancellous bone has a higher surface-area-to-volume ratio than cortical bone and it is less dense . This makes it weaker and more flexible. The greater surface area also makes it suitable for metabolic activities such as

2030-492: Is very minimal. Being able to consistently meet calcium needs while also engaging in weight-bearing exercise is essential for building a strong initial bone foundation at which to build upon. Being able to reach our daily value of 1300mg for ages 9-18 is becoming more and more necessary and as we progress in health, the chance that osteoporosis and other factors such as bone fragility or potential for stunted growth can be greatly reduced through these resources, ultimately leading to

2100-724: The middle ear which are involved in sound transduction. The cancellous part of bones contain bone marrow . Bone marrow produces blood cells in a process called hematopoiesis . Blood cells that are created in bone marrow include red blood cells , platelets and white blood cells . Progenitor cells such as the hematopoietic stem cell divide in a process called mitosis to produce precursor cells. These include precursors which eventually give rise to white blood cells , and erythroblasts which give rise to red blood cells. Unlike red and white blood cells, created by mitosis, platelets are shed from very large cells called megakaryocytes . This process of progressive differentiation occurs within

2170-479: The osteonic canal . Volkmann's canals at right angles connect the osteons together. The columns are metabolically active, and as bone is reabsorbed and created the nature and location of the cells within the osteon will change. Cortical bone is covered by a periosteum on its outer surface, and an endosteum on its inner surface. The endosteum is the boundary between the cortical bone and the cancellous bone. The primary anatomical and functional unit of cortical bone

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2240-496: The tarsals in the ankle and the carpals in the wrist. They are one of five types of bones : short, long , flat , irregular and sesamoid . Most short bones are named according to their shape as they exhibit a variety of complex morphological features (They can be cuboid , lenticular , trapezoidal , etc.) Some authors state that short bones are only located in the carpals and tarsals. The metacarpals , metatarsals and phalanges are considered long bones as they have

2310-420: 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. Osteoblasts can also be stimulated to increase bone mass through increased secretion of osteoid and by inhibiting the ability of osteoclasts to break down osseous tissue . Increased secretion of osteoid

2380-448: The 12-15 adolescent groups that at 2.6-2.8g/kg of body weight, they began to see a decrease in BMD. They elaborate on this by determining that this is strongly influenced by a lower baseline in calcium intake throughout puberty. Genetic factors have also been shown to influence lower acceptance of calcium stores. Ultimately, the window that youth have for accruing and building resilient bones

2450-517: The Hebei Provincial Institute of Cultural Relics, and other cultural institutions in the city and county level. The Early Neolithic period (7,000 BC–5,000 BC) succeeds Nanzhuangtou, and is characterized by the rise of farming villages across the alluvial plains of China, as seen in the site of Peiligang . 39°07′N 115°39′E  /  39.117°N 115.650°E  / 39.117; 115.650 This article about

2520-420: The acellular component of bone consists of organic matter, while roughly 70% by mass is attributed to the inorganic phase. The collagen fibers give bone its tensile strength , and the interspersed crystals of hydroxyapatite give bone its compressive strength . These effects are synergistic . The exact composition of the matrix may be subject to change over time due to nutrition and biomineralization , with

2590-479: The body is the femur or thigh-bone, and the smallest is the stapes in the middle ear . The Greek word for bone is ὀστέον (" osteon "), hence the many terms that use it as a prefix—such as osteopathy . In anatomical terminology , including the Terminologia Anatomica international standard, the word for a bone is os (for example, os breve , os longum , os sesamoideum ). Bone

2660-416: The bone marrow. After the cells are matured, they enter the circulation . Every day, over 2.5 billion red blood cells and platelets, and 50–100 billion granulocytes are produced in this way. As well as creating cells, bone marrow is also one of the major sites where defective or aged red blood cells are destroyed. Determined by the species, age, and the type of bone, bone cells make up to 15 percent of

2730-548: The bone matrix. The release of these growth factors from the bone matrix could cause the proliferation of osteoblast precursors. Essentially, bone growth factors may act as potential determinants of local bone formation. Cancellous bone volume in postmenopausal osteoporosis may be determined by the relationship between the total bone forming surface and the percent of surface resorption. A number of diseases can affect bone, including arthritis, fractures, infections, osteoporosis and tumors. Conditions relating to bone can be managed by

2800-654: The bone, except for the articular surfaces, is covered by the periosteum . Short bones have no clear diaphysis (bone shaft) and metaphysis and have poor vascular supply. Both short and long bones undergo endochondral ossification during development. In this process, bone is formed from an initial cartilaginous model and this model is then gradually replaced by bone. Despite sharing a common cellular origin, short and long bones have different structural features. Long bones have epiphyseal growth plates , where chondrocytes , stacked on top of each other, form longitudinal columns that are responsible for longitudinal growth of

2870-429: The bone. Growth factor storage—mineralized bone matrix stores important growth factors such as insulin -like growth factors, transforming growth factor, bone morphogenetic proteins and others. Strong bones during our youth is essential for preventing osteoporosis and bone fragility as we age. The importance of insuring factors that could influence increases in BMD while lowering our risks for further bone degradation

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2940-479: The bone. Long bones also have secondary ossification centers , in which cell columns are arranged in a radial pattern from the center like spokes on a wheel and cartilage-to-bone replacement starts in the center and extends centrifugally outwards. Contrary to long bones, the carpals and tarsals typically lack epiphyseal growth plates, hence lacking longitudinal growth and they undergo ossification radially, similar to secondary ossification centers in long bones. As

3010-426: The breakdown of bones by the process of bone resorption . New bone is then formed by the osteoblasts. Bone is constantly remodeled by the resorption of osteoclasts and created by osteoblasts. Osteoclasts are large cells with multiple nuclei located on bone surfaces in what are called Howship's lacunae (or resorption pits ). These lacunae are the result of surrounding bone tissue that has been reabsorbed. Because

3080-458: 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

3150-447: The conversion of cartilage to bone: Bone development in youth is extremely important in preventing future complications of the skeletal system. Regular exercise during childhood and adolescence can help improve bone architecture, making bones more resilient and less prone to fractures in adulthood. Physical activity, specifically resistance training, stimulates growth of bones by increasing both bone density and strength. Studies have shown

3220-567: The creation and mineralization of bone tissue, osteocytes , and osteoclasts , which are involved in the reabsorption of bone tissue. Osteoblasts and osteocytes are derived from osteoprogenitor cells, but osteoclasts are derived from the same cells that differentiate to form macrophages and monocytes . Within the marrow of the bone there are also hematopoietic stem cells . These cells give rise to other cells, including white blood cells , red blood cells , and platelets . Osteoblasts are mononucleate bone-forming cells. They are located on

3290-641: The differentiation of progenitor cells into osteoclasts, and decrease secretion of osteoprotegerin. Bone volume is determined by the rates of bone formation and bone resorption. Certain growth factors may work to locally alter bone formation by increasing osteoblast activity. Numerous bone-derived growth factors have been isolated and classified via bone cultures. These factors include insulin-like growth factors I and II, transforming growth factor-beta, fibroblast growth factor, platelet-derived growth factor, and bone morphogenetic proteins. Evidence suggests that bone cells produce growth factors for extracellular storage in

3360-453: The engravings of Crisóstomo Martinez . Bone marrow , also known as myeloid tissue in 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 or hematopoietic marrow, but as the child ages the hematopoietic fraction decreases in quantity and the fatty/ yellow fraction called marrow adipose tissue (MAT) increases in quantity. In adults, red marrow

3430-429: The exchange of calcium ions. Cancellous bone is typically found at the ends of long bones, near joints, and in the interior of vertebrae. Cancellous bone is highly vascular and often contains red bone marrow where hematopoiesis , the production of blood cells, occurs. The primary anatomical and functional unit of cancellous bone is the trabecula . The trabeculae are aligned towards the mechanical load distribution that

3500-410: The foci for calcium and phosphate deposition. Vesicles may initiate some of the early mineralization events by rupturing and acting as a centre for crystals to grow on. Bone mineral may be formed from globular and plate structures, and via initially amorphous phases. Five types of bones are found in the human body: long, short, flat, irregular, and sesamoid. In the study of anatomy , anatomists use

3570-410: The formation of bone from cartilage . Intramembranous ossification mainly occurs during formation of the flat bones of the skull but also the mandible, maxilla, and clavicles; the bone is formed from connective tissue such as mesenchyme tissue rather than from cartilage. The process includes: the development of the ossification center , calcification , trabeculae formation and the development of

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3640-590: The formation of osteoid to about 1 to 2  μm per day. Lamellar bone also requires a relatively flat surface to lay the collagen fibers in parallel or concentric layers. The extracellular matrix of bone is laid down by osteoblasts , which secrete both collagen and ground substance. These cells synthesise collagen alpha polypetpide chains and then secrete collagen molecules. The collagen molecules associate with their neighbors and crosslink via lysyl oxidase to form collagen fibrils. At this stage, they are not yet mineralized, and this zone of unmineralized collagen fibrils

3710-475: The groundwork for bone health later in life, reducing the risk of bone-related conditions such as osteoporosis. Bones have a variety of functions: Bones serve a variety of mechanical functions. Together the bones in the body form the skeleton . They provide a frame to keep the body supported, and an attachment point for skeletal muscles , tendons , ligaments and joints , which function together to generate and transfer forces so that individual body parts or

3780-487: The notion that prepuberty or even early pubertal children will see increases in BMD with the addition of increase Calcium intake. Another research study goes on to show that long-term calcium intake has been proven to significantly contribute to overall BMD in children without certain conditions or disorders. This data shows that ensuring adequate calcium intake in children reinforces the structure and rate at which bones will begin to densify. Further detailing how structuring

3850-478: The osteoblast puts up collagen fibers. These collagen fibers are used as a framework for the osteoblasts' work. The osteoblast then deposits calcium phosphate which is hardened by hydroxide and bicarbonate ions. The brand-new bone created by the osteoblast is called osteoid . Once the osteoblast is finished working it is actually trapped inside the bone once it hardens. When the osteoblast becomes trapped, it becomes known as an osteocyte. Other osteoblasts remain on

3920-502: The osteoclasts are derived from a monocyte stem-cell lineage, they are equipped with phagocytic -like mechanisms 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. The reabsorption of bone by osteoclasts also plays a role in calcium homeostasis . Bones consist of living cells (osteoblasts and osteocytes) embedded in

3990-456: The osteocyte cell processes occupy channels called canaliculi. The many processes of osteocytes reach out to meet osteoblasts, osteoclasts, bone lining cells, and other osteocytes probably for the purposes of communication. Osteocytes remain in contact with other osteocytes in the bone through gap junctions—coupled cell processes which pass through the canalicular channels. Osteoclasts are very large multinucleate cells that are responsible for

4060-427: The periosteum. Endochondral ossification occurs in long bones and most other bones in the body; it involves the development of bone from cartilage. This process includes the development of a cartilage model, its growth and development, development of the primary and secondary ossification centers , and the formation of articular cartilage and the epiphyseal plates . Endochondral ossification begins with points in

4130-684: The ratio of calcium to phosphate varying between 1.3 and 2.0 (per weight), and trace minerals such as magnesium , sodium , potassium and carbonate also be found. Type I collagen composes 90–95% of the organic matrix, with the remainder of the matrix being a homogenous liquid called ground substance consisting of proteoglycans such as hyaluronic acid and chondroitin sulfate , as well as non-collagenous proteins such as osteocalcin , osteopontin or bone sialoprotein . Collagen consists of strands of repeating units, which give bone tensile strength, and are arranged in an overlapping fashion that prevents shear stress. The function of ground substance

4200-462: The remainder is ground substance . The elasticity of collagen improves fracture resistance. The matrix is hardened by the binding of inorganic mineral salt, calcium phosphate , in a chemical arrangement known as bone mineral , a form of calcium apatite . It is the mineralization that gives bones rigidity. Bone is actively constructed and remodeled throughout life by special bone cells known as osteoblasts and osteoclasts. Within any single bone,

4270-578: The skeletal mass of an adult is remodelled each year. The purpose of remodeling is to regulate calcium homeostasis , repair microdamaged bones from everyday stress, and to shape the skeleton during growth. 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. The action of osteoblasts and osteoclasts are controlled by

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4340-401: The skeleton that are subjected to high forces or need to be very compact and where strength and stability are more important than range of motion. Short bones are characterized by their multiple articular surfaces and their tendency to form movable joints with adjacent bones. The articular surfaces of short bones are covered with hyaline cartilage , similar to long bones. The outer surface of

4410-469: The surface of osteon seams and make a protein mixture known as osteoid , which mineralizes to become bone. The osteoid seam is a narrow region of a newly formed organic matrix, not yet mineralized, located on the surface of a bone. Osteoid is primarily composed of Type I collagen . Osteoblasts also manufacture hormones , such as prostaglandins , to act on the bone itself. The osteoblast creates and repairs new bone by actually building around itself. First,

4480-450: The term "foramen" to describe a hole through which something passes, and a "canal" or "meatus" to describe a tunnel-like structure. A protrusion from a bone can be called a number of terms, including a "condyle", "crest", "spine", "eminence", "tubercle" or "tuberosity", depending on the protrusion's shape and location. In general, long bones are said to have a "head", "neck", and "body". When two bones join, they are said to "articulate". If

4550-419: The tissue is woven into two main patterns, known as cortical and cancellous bone, each with a different appearance and characteristics. The hard outer layer of bones is composed of cortical bone , which is also called compact bone as it is much denser than cancellous bone. It forms the hard exterior (cortex) of bones. The cortical bone gives bone its smooth, white, and solid appearance, and accounts for 80% of

4620-417: The top of the new bone and are used to protect the underlying bone, these become known as bone lining cells. Osteocytes are cells of mesenchymal origin and originate from osteoblasts that have migrated into and become trapped and surrounded by a bone matrix that they themselves produced. The spaces the cell body of osteocytes occupy within the mineralized collagen type I matrix are known as lacunae , while

4690-412: The total bone mass of an adult human skeleton . It facilitates bone's main functions—to support the whole body, to protect organs, to provide levers for movement, and to store and release chemical elements, mainly calcium. It consists of multiple microscopic columns, each called an osteon or Haversian system. Each column is multiple layers of osteoblasts and osteocytes around a central canal called

4760-418: The two bones have a fibrous connection and are relatively immobile, then the joint is called a "suture". The formation of bone is called ossification . During the fetal stage of development this occurs by two processes: intramembranous ossification and endochondral ossification . Intramembranous ossification involves the formation of bone from connective tissue whereas endochondral ossification involves

4830-430: The whole body can be manipulated in three-dimensional space (the interaction between bone and muscle is studied in biomechanics ). Bones protect internal organs, such as the skull protecting the brain or the ribs protecting the heart and lungs . Because of the way that bone is formed, bone has a high compressive strength of about 170  MPa (1,700  kgf/cm ), poor tensile strength of 104–121 MPa, and

4900-421: The youth. Sports such as soccer, basketball, and tennis have shown to have positive effects on bone mineral density as well as bone mineral content in teenagers. Engaging in physical activity during childhood years, particularly in these high-impact osteogenic sports, can help to positively influence bone mineral density in adulthood. Children and adolescents who participate in regular physical activity will place

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