144-492: Antlers are extensions of an animal's skull found in members of the Cervidae (deer) family . Antlers are a single structure composed of bone , cartilage , fibrous tissue , skin , nerves , and blood vessels . They are generally found only on males, with the exception of reindeer/caribou . Antlers are shed and regrown each year and function primarily as objects of sexual attraction and as weapons . Antler comes from
288-492: A cable-backed bow . Several Indigenous American tribes also used antler to make bows, gluing tendons to the bow instead of tying them as cables. An antler bow, made in the early 19th century, is on display at Brooklyn Museum . Its manufacture is attributed to the Yankton Sioux . Through history large deer antler from a suitable species (e.g. red deer ) were often cut down to its shaft and its lowest tine and used as
432-440: 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
576-994: A cranial capacity about 10 percent less than that of the male. However, later studies show that women's skulls are slightly thicker and thus men may be more susceptible to head injury than women. However, other studies shows that men's skulls are slightly thicker in certain areas. Some studies show that females are more susceptible to concussion than males. Men's skulls have also been shown to maintain density with age, which may aid in preventing head injury, while women's skull density slightly decreases with age. Male skulls can all have more prominent supraorbital ridges , glabella , and temporal lines . Female skulls generally have rounder orbits and narrower jaws. Male skulls on average have larger, broader palates , squarer orbits, larger mastoid processes , larger sinuses , and larger occipital condyles than those of females. Male mandibles typically have squarer chins and thicker, rougher muscle attachments than female mandibles. The cephalic index
720-604: A heavy encumbrance and to give him more time to regrow a larger new pair. Yet antlers are commonly retained through the winter and into the spring, suggesting that they have another use. Wolves in Yellowstone National Park are 3.6 times more likely to attack individual male elk without antlers, or groups of elk in which at least one male is without antlers. Half of all male elk killed by wolves lack antlers, at times in which only one quarter of all males have shed antlers. These findings suggest that antlers have
864-509: A large amount of tension on the "obstetrical hinge", which is where the squamous and lateral parts of the occipital bone meet. A possible complication of this tension is rupture of the great cerebral vein . As growth and ossification progress, the connective tissue of the fontanelles is invaded and replaced by bone creating sutures . The five sutures are the two squamous sutures , one coronal , one lambdoid , and one sagittal suture . The posterior fontanelle usually closes by eight weeks, but
1008-479: 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
1152-509: 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
1296-419: 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
1440-457: 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
1584-422: 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
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#17327654827041728-563: A one-pointed pickax . Antler headdresses were worn by shamans and other spiritual figures in various cultures, and for dances; 21 antler "frontlets" apparently for wearing on the head, and over 10,000 years old, have been excavated at the English Mesolithic site of Starr Carr . Antlers are still worn in traditional dances such as Yaqui deer dances and carried in the Abbots Bromley Horn Dance . In
1872-529: 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
2016-424: A publication now in the public domain : Chambers, Ephraim , ed. (1728). "antler" . Cyclopædia, or an Universal Dictionary of Arts and Sciences . Vol. 1 (1st ed.). James and John Knapton, et al. p. 113. Skull The skull , or cranium , is typically a bony enclosure around the brain of a vertebrate . In some fish , and amphibians , the skull is of cartilage . The skull
2160-419: 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
2304-489: A secondary function in deterring predation. Reindeer ( Rangifer tarandus) are the only cervid species that inhabit the Arctic and subarctic regions of the globe, yet their most striking distinction is the presence of pedicles after birth and antlers in both males and females. One possible reason that females of this species evolved antlers is to clear away snow so they can eat the vegetation underneath. Another possible reason
2448-403: A series of only loosely connected bones. Lampreys and sharks only possess a cartilaginous endocranium, with both the upper jaw and the lower jaws being separate elements. Bony fishes have additional dermal bone , forming a more or less coherent skull roof in lungfish and holost fish. The lower jaw defines the chin. The simpler structure is found in jawless fish , in which the cranium
2592-464: A shed trap to collect the loose antlers in the late winter/early spring. In most US states, the possession of or trade in parts of game animals is subject to some degree of regulation, but the trade in antlers is widely permitted. In the national parks of Canada, the removal of shed antlers is an offense punishable by a maximum fine of C$ 25,000, as the Canadian government considers antlers to belong to
2736-408: 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,
2880-467: A source of calcium, phosphorus and other minerals and are often gnawed upon by small animals, including squirrels, porcupines, rabbits and mice. This is more common among animals inhabiting regions where the soil is deficient in these minerals. Antlers shed in oak forest inhabited by squirrels are rapidly chewed to pieces by them. Antlered heads are prized as trophies with larger sets being more highly prized. The first organization to keep records of sizes
3024-401: 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
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#17327654827043168-399: A study of trophy antlers with an artificial ear confirmed that the large flattened (palmate) antler behaves like a parabolic reflector. The diversification of antlers, body size and tusks has been strongly influenced by changes in habitat and behavior (fighting and mating). Antlers originated once in the cervid lineage. The earliest fossil remains of antlers that have been found are dated to
3312-416: 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
3456-456: 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
3600-441: 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
3744-444: Is a phenomenon wherein intense intracranial pressure disfigures the internal surface of the skull. The name comes from the fact that the inner skull has the appearance of having been beaten with a ball-peen hammer , such as is often used by coppersmiths . The condition is most common in children. Injuries to the brain can be life-threatening. Normally the skull protects the brain from damage through its high resistance to deformation;
3888-735: Is an organization for those who take part in this activity. In the United States in 2017 sheds fetch around US$ 10 per pound, with larger specimens in good condition attracting higher prices. The most desirable antlers have been found soon after being shed. The value is reduced if they have been damaged by weathering or being gnawed by small animals. A matched pair from the same animal is a very desirable find but often antlers are shed separately and may be separated by several miles. Some enthusiasts for shed hunting use trained dogs to assist them. Most hunters will follow 'game trails' (trails where deer frequently run) to find these sheds or they will build
4032-813: Is annual, and is controlled by the length of daylight. Although the antlers are regrown each year, their size varies with the age of the animal in many species, increasing annually over several years before reaching maximum size. In tropical species, antlers may be shed at any time of year, and in some species such as the sambar , antlers are shed at different times in the year depending on multiple factors. Some equatorial deer never shed their antlers. A 2019 study published in Science identified eight genes active in antler formation that are normally associated with bone cancer , particularly osteosarcoma . Additional tumor-suppressing and tumor-growth-inhibiting genes were determined to be responsible for regulating antler growth. This
4176-487: Is at the head end of the vertebrate. In the human the skull comprises two prominent parts: the neurocranium , and the facial skeleton . which evolved from the first pharyngeal arch . The skull forms the frontmost portion of the axial skeleton and is a product of cephalization and vesicular enlargement of the brain, with several special senses structures such as the eyes , ears , nose , tongue and in fish specialized tactile organs such as barbels near
4320-474: 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
4464-407: Is characterized as being made up of primarily collagen and a mineral phase . In antlers, the mineral content is considerably lower than other examples of bone tissue, while having a high volume of collagen. This leads antlers to having lower yield strength and stiffness , but higher fracture toughness when compared to human cortical bone. Mineral content differs among species and also depends on
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4608-418: 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
4752-490: Is for female competition during winter foraging. Espmark (1964) observed that the presence of antlers on females is related to the hierarchy rank and is a result of the harsh winter conditions and the female dominated parental investment. Males shed their antlers prior to winter, while female antlers are retained throughout winter. Also, female antler size plateaus at the onset of puberty, around age three, while males' antler size increases during their lifetime. This likely reflects
4896-589: 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
5040-492: 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
5184-518: 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
5328-527: 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
5472-405: Is no space for the brain to expand; this can result in significant brain damage or death unless an urgent operation is performed to relieve the pressure. This is why patients with concussion must be watched extremely carefully. Repeated concussions can activate the structure of skull bones as the brain's protective covering. Dating back to Neolithic times, a skull operation called trepanning
5616-414: Is normally represented by a trough-like basket of cartilaginous elements only partially enclosing the brain, and associated with the capsules for the inner ears and the single nostril. Distinctively, these fish have no jaws. Cartilaginous fish , such as sharks and rays, have also simple, and presumably primitive, skull structures. The cranium is a single structure forming a case around the brain, enclosing
5760-455: 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
5904-403: 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
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6048-423: Is one seventh of the size of the calvaria . (In the adult it is half the size). The base of the skull is short and narrow, though the inner ear is almost adult size. Craniosynostosis is a condition in which one or more of the fibrous sutures in an infant skull prematurely fuses, and changes the growth pattern of the skull. Because the skull cannot expand perpendicular to the fused suture, it grows more in
6192-473: Is sexual selection, which operates via two mechanisms: male-to-male competition (behaviorally, physiologically) and female mate choice . Male-male competition can take place in two forms. First, they can compete behaviorally where males use their antlers as weapons to compete for access to mates; second, they can compete physiologically where males present their antlers to display their strength and fertility competitiveness to compete for access to mates. Males with
6336-730: 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
6480-561: 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
6624-405: Is that the costs of having larger antlers (resource use, and mobility detriments, for instance) exert enough selective pressure to offset the benefit of attracting mates; thereby stabilizing antler size in the population. If antlers functioned only in male–male competition for mates, the best evolutionary strategy would be to shed them immediately after the rutting season, both to free the male from
6768-442: Is the foramen magnum , where the brainstem goes through to join the spinal cord . In human anatomy , the neurocranium (or braincase), is further divided into the calvarium and the endocranium , together forming a cranial cavity that houses the brain. The interior periosteum forms part of the dura mater , the facial skeleton and splanchnocranium with the mandible being its largest bone. The mandible articulates with
6912-448: 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
7056-452: Is the bone structure that forms the head in the human skeleton . It supports the structures of the face and forms a cavity for the brain . Like the skulls of other vertebrates, it protects the brain from injury. The skull consists of three parts, of different embryological origin—the neurocranium , the sutures , and the facial skeleton . The neurocranium (or braincase ) forms the protective cranial cavity that surrounds and houses
7200-431: Is the ratio of the width of the head, multiplied by 100 and divided by its length (front to back). The index is also used to categorize animals, especially dogs and cats. The width is usually measured just below the parietal eminence , and the length from the glabella to the occipital point. Humans may be: The vertical cephalic index refers to the ratio between the height of the head multiplied by 100 and divided by
7344-492: 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
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#17327654827047488-600: The Old French antoillier (see present French : "Andouiller", from ant-, meaning before, oeil, meaning eye and -ier , a suffix indicating an action or state of being) possibly from some form of an unattested Latin word *anteocularis , "before the eye" (and applied to the word for "branch" or " horn "). Antlers are unique to cervids . The ancestors of deer had tusks (long upper canine teeth ). In most species, antlers appear to replace tusks. However, one modern species (the water deer ) has tusks and no antlers and
7632-403: The facial skeleton (14) are the vomer , two inferior nasal conchae , two nasal bones , two maxilla , the mandible, two palatine bones , two zygomatic bones , and two lacrimal bones . Some sources count a paired bone as one, or the maxilla as having two bones (as its parts); some sources include the hyoid bone or the three ossicles of the middle ear , the malleus, incus, and stapes, but
7776-405: The frontal bone ). The bones of the roof of the skull are initially separated by regions of dense connective tissue called fontanelles . There are six fontanelles: one anterior (or frontal), one posterior (or occipital), two sphenoid (or anterolateral), and two mastoid (or posterolateral). At birth, these regions are fibrous and moveable, necessary for birth and later growth. This growth can put
7920-724: 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
8064-591: The muntjacs have small antlers and tusks. The musk deer , which are not true cervids, also bear tusks in place of antlers. In contrast to antlers, horns —found on pronghorns and bovids , such as sheep, goats, bison and cattle—are two-part structures that usually do not shed. A horn's interior of bone is covered by an exterior sheath made of keratin (the same material as human fingernails and toenails). Antlers are usually found only on males. Only reindeer (known as caribou in North America) have antlers on
8208-479: 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
8352-400: The public domain from page 128 of the 20th edition of Gray's Anatomy (1918) 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
8496-421: The skull base and its fossae , the anterior , middle and posterior cranial fossae changes rapidly. The anterior cranial fossa changes especially during the first trimester of pregnancy and skull defects can often develop during this time. At birth, the human skull is made up of 44 separate bony elements. During development, many of these bony elements gradually fuse together into solid bone (for example,
8640-619: The temporal bones of the neurocranium at the paired temporomandibular joints . The skull itself articulates with the spinal column at the atlanto-occipital joint . Functions of the skull include physical protection for the brain, providing attachments for neck muscles , facial muscles and muscles of mastication , providing fixed eye sockets and outer ears ( ear canals and auricles ) to enable stereoscopic vision and sound localisation , forming nasal and oral cavities that allow better olfaction , taste and digestion , and contributing to phonation by acoustic resonance within
8784-420: 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
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#17327654827048928-888: The velvet antler stage, antlers of elk and deer have been used in Asia as a dietary supplement or alternative medicinal substance for more than 2,000 years. Recently, deer antler extract has become popular among Western athletes and body builders because the extract, with its trace amounts of IGF-1 , is believed to help build and repair muscle tissue ; however, one double-blind study did not find evidence of intended effects. Elk, deer, and moose antlers have also become popular forms of dog chews that owners purchase for their pet canines. Dogs are sometimes used to find shed antlers. The North American Shed Hunting Dog Association (NASHDA) has resources for people who want to train their dogs to find shed antlers and hold shed dog hunting events. [REDACTED] This article incorporates text from
9072-404: The zygomatic processes . The fenestrae (from Latin, meaning windows ) are openings in the skull. The jugal is a skull bone that found in most of the reptiles, amphibians and birds. In mammals, the jugal is often called the zygomatic bone or malar bone. The prefrontal bone is a bone that separates the lacrimal and frontal bones in many tetrapod skulls. The skull of fish is formed from
9216-448: 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
9360-630: The U.S., researchers replaced a large percentage of a patient's skull with a precision, 3D-printed polymer implant . About 9 months later, the first complete cranium replacement with a 3D-printed plastic insert was performed on a Dutch woman. She had been suffering from hyperostosis , which increased the thickness of her skull and compressed her brain. A study conducted in 2018 by the researchers of Harvard Medical School in Boston, funded by National Institutes of Health (NIH), suggested that instead of travelling via blood , there are "tiny channels" in
9504-626: The Viking Age and medieval period, it formed an important raw material in the craft of comb-making. In later periods, antler—used as a cheap substitute for ivory —was a material especially associated with equipment for hunting , such as saddles and horse harness, guns and daggers, powder flasks , as well as buttons and the like. The decorative display of wall-mounted pairs of antlers has been popular since medieval times at least. The Netsilik , an Inuit group, made bows and arrows using antler, reinforced with strands of animal tendons braided to form
9648-420: 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
9792-428: The anterior fontanel can remain open up to eighteen months. The anterior fontanelle is located at the junction of the frontal and parietal bones; it is a "soft spot" on a baby's forehead. Careful observation will show that you can count a baby's heart rate by observing the pulse pulsing softly through the anterior fontanelle. The skull in the neonate is large in proportion to other parts of the body. The facial skeleton
9936-553: The antler has achieved its full size, the velvet is lost and the antler's bone dies. This dead bone structure is the mature antler. In most cases, the bone at the base is destroyed by osteoclasts and the antlers fall off at some point. As a result of their fast growth rate, antlers are considered a handicap since there is an immense nutritional demand on deer to re-grow antlers annually, and thus can be honest signals of metabolic efficiency and food gathering capability. In most Arctic and temperate-zone species, antler growth and shedding
10080-479: 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
10224-416: 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
10368-548: 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
10512-429: 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
10656-466: The bones either absent or wholly or partly replaced by cartilage. In mammals and birds, in particular, modifications of the skull occurred to allow for the expansion of the brain. The fusion between the various bones is especially notable in birds, in which the individual structures may be difficult to identify. The skull is a complex structure; its bones are formed both by intramembranous and endochondral ossification . The skull roof bones, comprising
10800-416: The bones of the facial skeleton and the sides and roof of the neurocranium, are dermal bones formed by intramembranous ossification, though the temporal bones are formed by endochondral ossification. The endocranium , the bones supporting the brain (the occipital, sphenoid , and ethmoid ) are largely formed by endochondral ossification. Thus frontal and parietal bones are purely membranous. The geometry of
10944-462: The brain and brainstem . The upper areas of the cranial bones form the calvaria (skullcap). The facial skeleton (membranous viscerocranium) is formed by the bones supporting the face, and includes the mandible . The bones of the skull are joined by fibrous joints known as sutures— synarthrodial (immovable) joints formed by bony ossification , with Sharpey's fibres permitting some flexibility. Sometimes there can be extra bone pieces within
11088-426: 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
11232-458: 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
11376-566: The cavities and sinuses. In some animals such as ungulates and elephants , the skull also has a function in anti-predator defense and sexual selection by providing the foundation for horns , antlers and tusks . The English word skull is probably derived from Old Norse skulle , while the Latin word cranium comes from the Greek root κρανίον ( kranion ). The human skull fully develops two years after birth. The human skull
11520-447: 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
11664-567: 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
11808-438: The desired sex. These procedures can be an important part of the treatment of transgender people for gender dysphoria . Artificial cranial deformation is a largely historical practice of some cultures. Cords and wooden boards would be used to apply pressure to an infant's skull and alter its shape, sometimes quite significantly. This procedure would begin just after birth and would be carried on for several years. Like
11952-641: 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
12096-658: The differing life history strategies of the two sexes, where females are resource limited in their reproduction and cannot afford costly antlers, while male reproductive success depends on the size of their antlers because they are under directional sexual selection. In other species of deer, the presence of antlers in females indicates some degree of intersex condition, the frequency of which has been seen to vary from 1.5% to 0.02%. In moose , antlers may act as large hearing aids. Equipped with large, highly adjustable external ears, moose have highly sensitive hearing. Moose with antlers have more sensitive hearing than moose without, and
12240-466: The early Miocene, about 17 million years ago. These early antlers were small and had just two forks. As antlers evolved, they lengthened and gained many branches, or tines, becoming more complex. The homology of tines has been discussed since the 1900s and has provided great insight into the evolutionary history of the Cervidae family. Recently, a new method to describe the branching structure of antlers
12384-406: The elastic modulus for dry samples was 17.1 GPa, 7.5 GPa for wet samples, and 17.7 GPa for bovine femur. This difference in elastic modulus is due to the difference in function of a bovine femur versus an antler. Bovine femurs must withstand greater stresses, holding up the body of the animal, whereas an antler is used for sexual selection and competition. The principal means of evolution of antlers
12528-453: 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
12672-429: 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
12816-531: The face, the skull and teeth can also indicate a person's life history and origin. Forensic scientists and archaeologists use quantitative and qualitative traits to estimate what the bearer of the skull looked like. When a significant amount of bones are found, such as at Spitalfields in the UK and Jōmon shell mounds in Japan, osteologists can use traits, such as the proportions of length, height and width, to know
12960-448: The females, and these are normally smaller than those of the males. Nevertheless, fertile does from other species of deer have the capacity to produce antlers on occasion, usually due to increased testosterone levels. The "horns" of a pronghorn (which is not a cervid but a antilocaprid ) meet some of the criteria of antlers, but are not considered true antlers because they contain keratin . Each antler grows from an attachment point on
13104-410: 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
13248-552: The food availability. In recent studies, increase in mineral content has been linked to the increase in stiffness with a decrease in fracture toughness. Further, bones are highly anisotropic due to their hierarchical structure. Thus, mechanical properties are highly dependent on testing conditions and directions. Due to their cylindrical shape, antlers can be tested using bending along three different orientations . Bend testing in these orientations have resulted in different mechanical properties. In samples from antler bone taken in
13392-418: The foramen magnum lies immediately above a single condyle , articulating with the first vertebra . There are, in addition, at various points throughout the cranium, smaller foramina for the cranial nerves. The jaws consist of separate hoops of cartilage, almost always distinct from the cranium proper. In ray-finned fish , there has also been considerable modification from the primitive pattern. The roof of
13536-410: 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
13680-590: 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
13824-438: The frontal (top of head), parietal (back of head), premaxillary and nasal (top beak), and the mandible (bottom beak). The skull of a normal bird usually weighs about 1% of the bird's total bodyweight. The eye occupies a considerable amount of the skull and is surrounded by a sclerotic eye-ring, a ring of tiny bones. This characteristic is also seen in reptiles. Living amphibians typically have greatly reduced skulls, with many of
13968-475: 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
14112-411: The lack of response could be explained by the relationship between heterozygosity and antler size, which states that males heterozygous at multiple loci, including MHC loci, have larger antlers. The evolutionary response of traits that depend on heterozygosity is slower than traits that are dependent on additive genetic components and thus the evolutionary change is slower than expected. A third possibility
14256-576: The large antlers produced there. This is due to the high levels of chalk in Yorkshire. The chalk is high in calcium which is ingested by the deer and helps growth in the antlers. Gathering shed antlers or "sheds" attracts dedicated practitioners who refer to it colloquially as shed hunting , or bone picking . In the United States, the middle of December to the middle of February is considered shed hunting season, when deer, elk , and moose begin to shed. The North American Shed Hunting Club, founded in 1991,
14400-425: The largest antlers are more likely to obtain mates and achieve the highest fertilization success due to their competitiveness, dominance and high phenotypic quality. Whether this is a result of male-male fighting or display, or of female choosiness differs depending on the species as the shape, size, and function of antlers vary between species. There is evidence to support that antler size influences mate selection in
14544-484: The length of the head. Humans may be: Trepanning , a practice in which a hole is created in the skull, has been described as the oldest surgical procedure for which there is archaeological evidence, found in the forms of cave paintings and human remains. At one burial site in France dated to 6500 BCE, 40 out of 120 prehistoric skulls found had trepanation holes. [REDACTED] This article incorporates text in
14688-418: The lessening of the weight of the skull, the aiding of resonance to the voice and the warming and moistening of the air drawn into the nasal cavity . The foramina are openings in the skull. The largest of these is the foramen magnum , of the occipital bone, that allows the passage of the spinal cord as well as nerves and blood vessels . The many processes of the skull include the mastoid process and
14832-568: The longitudinal and radial directions' values of 46.91-48.55 and 41.75-43.67 MPa. Tensile testing of antler bones has also been conducted to compare to bovine femur results. The antler samples were tested in dry and wet conditions as done in other studies. The wetness of a sample resulted in a difference in mean maximum strain : 1.46% and 2.2%, dry and wet respectively. Further, the ultimate tensile strength of wet, dry and bovine difference showed differences as well: 188 MPa, 108 MPa, and 99.2 MPa for dry, wet and bovine samples respectively. Similarly,
14976-453: The lower jaw is composed of multiple bones, only the most anterior of which (the dentary) is homologous with the mammalian mandible. In living tetrapods, a great many of the original bones have either disappeared or fused into one another in various arrangements. Birds have a diapsid skull, as in reptiles, with a prelacrimal fossa (present in some reptiles). The skull has a single occipital condyle. The skull consists of five major bones:
15120-406: The lower surface and the sides, but always at least partially open at the top as a large fontanelle . The most anterior part of the cranium includes a forward plate of cartilage, the rostrum , and capsules to enclose the olfactory organs. Behind these are the orbits, and then an additional pair of capsules enclosing the structure of the inner ear . Finally, the skull tapers towards the rear, where
15264-441: The mid-nineteenth century, anthropologists found it crucial to distinguish between male and female skulls. An anthropologist of the time, James McGrigor Allan , argued that the female brain was similar to that of an animal. This allowed anthropologists to declare that women were in fact more emotional and less rational than men. McGrigor then concluded that women's brains were more analogous to infants, thus deeming them inferior at
15408-407: The mouth. The skull is composed of three types of bone : cranial bones, facial bones and ossicles , which is made up of a number of fused flat and irregular bones . The cranial bones are joined at firm fibrous junctions called sutures and contains many foramina , fossae , processes , and sinuses . In zoology , the openings in the skull are called fenestrae , the most prominent of which
15552-487: 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
15696-478: 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
15840-502: 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
15984-456: 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
16128-442: The overall general consensus of the number of bones in the human skull is the stated twenty-two. Some of these bones—the occipital, parietal, frontal, in the neurocranium, and the nasal, lacrimal, and vomer, in the facial skeleton are flat bones . The skull also contains sinuses , air-filled cavities known as paranasal sinuses , and numerous foramina . The sinuses are lined with respiratory epithelium . Their known functions are
16272-493: The parallel direction. Sometimes the resulting growth pattern provides the necessary space for the growing brain, but results in an abnormal head shape and abnormal facial features. In cases in which the compensation does not effectively provide enough space for the growing brain, craniosynostosis results in increased intracranial pressure leading possibly to visual impairment, sleeping impairment, eating difficulties, or an impairment of mental development. A copper beaten skull
16416-638: The people of Canada and part of the ecosystems in which they are discarded. Antler has been used through history as a material to make tools, weapons, ornaments, and toys. It was an especially important material in the European Late Paleolithic , used by the Magdalenian culture to make carvings and engraved designs on objects such as the so-called Bâton de commandements and the Bison Licking Insect Bite . In
16560-774: The periodic casting and regrowth of antlers might have evolved as a way to ensure the availability of complete antler sets to display each year. Antler regeneration in male deer ensures that every mating season begins on a clean slate, as an increase in branching size and complexity happens each regeneration cycle in an individual. Bones typically serve a structural purpose, with load bearing abilities that are greater than any other part of an animals body. Bones typically differ in shape and properties to better fit their overall function. Antlers are not structural and typically have different properties when compared to structural bones like femurs. While antlers are classified as bone, they differ in some ways from human bones and bovine bones. Bone
16704-427: 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
16848-684: 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
16992-428: The red deer, and has a heritable component. Despite this, a 30-year study showed no shift in the median size of antlers in a population of red deer. The lack of response could be explained by environmental covariance, meaning that lifetime breeding success is determined by an unmeasured trait which is phenotypically correlated with antler size but for which there is no genetic correlation of antler growth. Alternatively,
17136-399: The relationships of the population of the study with other living or extinct populations. The German physician Franz Joseph Gall in around 1800 formulated the theory of phrenology , which attempted to show that specific features of the skull are associated with certain personality traits or intellectual capabilities of its owner. His theory is now considered to be pseudoscientific . In
17280-462: 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,
17424-470: The size of the antlers. Hunters have developed terms for antler parts: beam, palm, brow, bez or bay, trez or tray, royal, and surroyal. These are the main shaft, flattened center, first tine , second tine, third tine, fourth tine, and fifth or higher tines, respectively. The second branch is also called an advancer. In Yorkshire in the United Kingdom roe deer hunting is especially popular due to
17568-578: 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
17712-428: The skull called a pedicle. While an antler is growing, it is covered with highly vascular skin called velvet , which supplies oxygen and nutrients to the growing bone. Antlers are considered one of the most exaggerated cases of male secondary sexual traits in the animal kingdom, and grow faster than any other mammal bone. Growth occurs at the tip, and is initially cartilage , which is later replaced by bone tissue. Once
17856-474: The skull is formed from cartilage , and its overall structure is reduced. The skulls of the earliest tetrapods closely resembled those of their ancestors amongst the lobe-finned fishes . The skull roof is formed of a series of plate-like bones, including the maxilla, frontals , parietals , and lacrimals , among others. It is overlaying the endocranium , corresponding to the cartilaginous skull in sharks and rays . The various separate bones that compose
18000-455: The skull is generally well formed, and although the exact relationship of its bones to those of tetrapods is unclear, they are usually given similar names for convenience. Other elements of the skull, however, may be reduced; there is little cheek region behind the enlarged orbits, and little, if any bone in between them. The upper jaw is often formed largely from the premaxilla , with the maxilla itself located further back, and an additional bone,
18144-409: The skull is one of the least deformable structures found in nature, needing the force of about 1 ton to reduce its diameter by 1 cm. In some cases of head injury , however, there can be raised intracranial pressure through mechanisms such as a subdural haematoma . In these cases, the raised intracranial pressure can cause herniation of the brain out of the foramen magnum ("coning") because there
18288-459: The skull through which the immune cells combined with the bone marrow reach the areas of inflammation after an injury to the brain tissues. Surgical alteration of sexually dimorphic skull features may be carried out as a part of facial feminization surgery or facial masculinization surgery , these reconstructive surgical procedures that can alter sexually dimorphic facial features to bring them closer in shape and size to facial features of
18432-469: 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,
18576-404: The suture known as Wormian bones or sutural bones . Most commonly these are found in the course of the lambdoid suture . The human skull is generally considered to consist of 22 bones—eight cranial bones and fourteen facial skeleton bones. In the neurocranium these are the occipital bone , two temporal bones , two parietal bones , the sphenoid , ethmoid and frontal bones . The bones of
18720-457: The symplectic, linking the jaw to the rest of the cranium. Although the skulls of fossil lobe-finned fish resemble those of the early tetrapods, the same cannot be said of those of the living lungfishes . The skull roof is not fully formed, and consists of multiple, somewhat irregularly shaped bones with no direct relationship to those of tetrapods. The upper jaw is formed from the pterygoids and vomers alone, all of which bear teeth. Much of
18864-413: The temporal bone of humans are also part of the skull roof series. A further plate composed of four pairs of bones forms the roof of the mouth; these include the vomer and palatine bones . The base of the cranium is formed from a ring of bones surrounding the foramen magnum and a median bone lying further forward; these are homologous with the occipital bone and parts of the sphenoid in mammals. Finally,
19008-450: 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
19152-554: The time. To further these claims of female inferiority and silence the feminists of the time, other anthropologists joined in on the studies of the female skull. These cranial measurements are the basis of what is known as craniology . These cranial measurements were also used to draw a connection between women and black people. Research has shown that while in early life there is little difference between male and female skulls, in adulthood male skulls tend to be larger and more robust than female skulls, which are lighter and smaller, with
19296-419: 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
19440-417: 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
19584-412: 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
19728-428: The transverse direction, an elastic modulus of 8.92-10.02 GPa was reported. For the longitudinal and radial orientations, the elastic modulus was 7.19-8.23 and 4.01-4.27 GPa respectively. The transverse direction was overall found to be the stronger orientation with higher mechanical properties. The ultimate tensile strength of 262.96-274.38 MPa in the transverse direction was statistically significant when compared to
19872-418: 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
20016-430: 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
20160-421: 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
20304-565: Was Rowland Ward Ltd., a London taxidermy firm, in the early 20th century. For a time only total length or spread was recorded. In the middle of the century, the Boone and Crockett Club and the Safari Club International developed complex scoring systems based on various dimensions and the number of tines or points, and they keep extensive records of high-scoring antlers. Deer bred for hunting on farms are selected based on
20448-461: Was developed. It is by using antler grooves, which are formed on the surface of antlers by growth, projecting the branching structure on the burr circumference, and making diagrams. Comparing the positional order among species on the diagram, the tine on the same position is homologous. The study revealed that three-pointed structures of Capreolinae and Cervini are homoplasious, and their subclades gained synapomorphous tines. Discarded antlers represent
20592-400: Was sometimes performed. This involved drilling a burr hole in the cranium. Examination of skulls from this period reveals that the patients sometimes survived for many years afterward. It seems likely that trepanning was also performed purely for ritualistic or religious reasons. Nowadays this procedure is still used but is normally called a craniectomy . In March 2013, for the first time in
20736-411: Was taken to indicate that antler formation is more similar to a highly controlled form of cancer growth than to normal bone development. Antlers function as both weapons in male-male competition and as displays of sexual ornaments for females. Because mature antlers are no longer living during combat, antler fractures are incapable of being repaired following competition. A study in 2019 hypothesized that
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