premaxillary bone

bone (bōn)

1. the hard, rigid form of connective tissue constituting most of the skeleton of vertebrates, composed chiefly of calcium salts.

2. any distinct piece of the skeleton of the body.

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ankle bone  talus.

basiotic bone  a small bone in the fetus between the basilar process and the basisphenoid.

brittle bones  osteogenesis imperfecta.

cancellous bone  see lamellar b.

capitate bone  the bone in the distal row of carpal bones lying between the trapezoid and hamate bones.

carpal bones  the eight bones of the wrist (carpus), including the capitate, hamate, lunate, pisiform, scaphoid, trapezoid, and triquetral bones and the trapezium.

cartilage bone  bone developing within cartilage, ossification taking place within a cartilage model.

cheek bone  zygomatic b.

collar bone  clavicle.

compact bone  see lamellar b.

cortical bone  the compact bone of the shaft of a bone that surrounds the marrow cavity.

cuboid bone  a bone on the lateral side of the tarsus between the calcaneus and the fourth and fifth metatarsal bones.

cuneiform bone, intermediate  the intermediate and smallest of the three wedge-shaped tarsal bones located medial to the cuboid and between the navicular and the first three metatarsal bones.

cuneiform bone, lateral  the most lateral of the three wedge-shaped tarsal bones located medial to the cuboid and between the navicular and the first three metatarsal bones.

cuneiform bone, medial  the medial and largest of the three wedge-shaped tarsal bones located medial to the cuboid and between the navicular and the first three metatarsal bones.

ethmoid bone  the cubical bone located between the orbits and consisting of the lamina cribrosa, the lamina perpendicularis, and the paired lateral masses.

flat bone  one whose thickness is slight, sometimes consisting of only a thin layer of compact bone, or of two layers with intervening cancellous bone and marrow; usually curved rather than flat.

frontal bone  a single bone that closes the anterior part of the cranial cavity and forms the skeleton of the forehead; it is developed from two halves, the line of separation (the frontal suture) sometimes persisting in adult life.

funny bone  the region of the median condyle of the humerus where it is crossed by the ulnar nerve.

hamate bone  the medial bone in the distal row of carpal bones.

heel bone  calcaneus.

hip bone  the large bone in the hip, consisting of the ilium, the ischium, and the pubic bone.

hyoid bone  a horseshoe-shaped bone at the base of the tongue, just superior to the thyroid cartilage.

incisive bone  the portion of the maxilla bearing the incisors; developmentally, it is the premaxilla, which in humans later fuses with the maxilla, but in most other vertebrates persists as a separate bone.

innominate bone  hip b.

jaw bone  the mandible or maxilla, especially the mandible.

jugal bone  zygomatic b.

lacrimal bone  a thin scalelike bone at the anterior part of the medial wall of the orbit, articulating with the frontal and ethmoid bones and the maxilla and inferior nasal concha.

lamellar bone  the normal type of adult bone, organized in layers (lamellae), which may be parallel (cancellous b.) or concentrically arranged (compact b.).

lingual bone  hyoid b.

long bone  a bone that has a longitudinal axis of considerable length, consisting of a body or shaft (the diaphysis) and an expanded portion (the epiphysis) at each end that is usually articular; typically found in the limbs.

lunate bone  the bone in the proximal row of carpal bones lying between the scaphoid and triquetral bones.

malar bone  zygomatic b.

marble bones  osteopetrosis.

mastoid bone  mastoid part of temporal bone; see under part.

metacarpal bones  the five cylindrical bones of the hand (metacarpals), which articulate proximally with the bones of the wrist and distally with the proximal phalanges of the fingers; numbered from that articulating with the phalanx of the thumb to that articulating with the phalanx of the little finger.

metatarsal bones  the five bones (metatarsals) extending from the ankle to the phalanges of the toes; numbered from the most medial articulating with the phalanx of the big toe to the most lateral articulating with the phalanx of the little toe.

nasal bone  either of the two small, oblong bones that together form the bridge of the nose.

navicular bone  the oval-shaped tarsal bone found between the talus and the three cuneiform bones.

occipital bone  a single trapezoid-shaped bone at the posterior inferior part of the cranium, articulating with the two parietal and two temporal bones, the sphenoid bone, and the atlas; it contains a large opening, the foramen magnum.

palatine bone  the irregularly shaped bone forming the posterior part of the hard palate, the lateral wall of the nasal fossa between the medial pterygoid plate and the maxilla, and the posterior part of the floor of the orbit.

parietal bone  either of the two quadrilateral bones forming part of the superior and lateral surfaces of the skull, and joining each other in the midline at the sagittal suture.

pelvic bone  hip b.

petrous bone  petrous part of temporal bone; see under part.

pisiform bone  the medial bone of the proximal row of carpal bones.

pneumatic bone  bone that contains air-filled spaces.

premaxillary bone  premaxilla.

pterygoid bone  see under process.

pubic bone  the anterior inferior part of the hip bone on either side, articulating with its fellow in the anterior midline at the pubic symphysis; it is a separate bone in early life.

rider's bone  localized ossification of the inner aspect of the lower end of the tendon of the adductor muscle of the thigh; sometimes seen in horseback riders.

semilunar bone  lunate b.

sesamoid bones  numerous ovoid nodular bones, often small, usually found embedded within a tendon or joint capsule, principally in the hands and feet; two sesamoid bones, the fabella and patella, are associated with the knee.

shin bone  tibia.

sphenoid bone  a single irregular, wedge-shaped bone at the base of the skull, forming part of the floor of the anterior, middle, and posterior cranial fossae.

squamous bone  squamous part of temporal bone; see under part.

sutural bone  variable and irregularly shaped bones in the sutures between the bones of the skull.

tail bone  coccyx.

tarsal bones  the seven bones of the ankle (tarsus), including the calcaneus, the cuboid bone, the navicular bone, the talus, and the intermediate, lateral, and medial cuneiform bones.

temporal bone  either of the two irregular bones forming part of the lateral surfaces and base of the skull, and containing the organs of hearing. It is divided anatomically into four parts: the mastoid, petrous, squamous, and tympanic parts.

thigh bone  femur.

trapezoid bone  the bone in the distal row of carpal bones lying between the trapezium and the capitate bone.

triquetral bone  the bone in the proximal row of carpal bones lying between the lunate and pisiform bones.

turbinate bone  any of the nasal conchae.

tympanic bone  tympanic part of temporal bone; see under part.

unciform bone , uncinate bone hamate b.

wormian bone  sutural bone.

zygomatic bone  the quadrangular bone of the cheek, articulating with the frontal bone, the maxilla, the zygomatic process of the temporal bone, and the greater wing of the sphenoid bone.

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pre·max·il·lar·y bone (pr-mks-lr)

n.

See incisive bone.

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bone [bōn]

1. the hard, rigid form of connective tissue constituting most of the skeleton of vertebrates, composed chiefly of calcium salts.

2. any distinct piece of the skeleton of the body. See anatomic Table of Bones in the Appendices for regional and alphabetical listings of bones, and see color plates 1 and 2. Called also os. adj., adj bo´ny.

There are 206 separate bones in the human body. Collectively they form the skeletal system, a structure bound together by ligaments at the joints and set in motion by the muscles, which are secured to the bones by means of tendons. Bones, ligaments, muscles, and tendons are the tissues of the body responsible for supporting and moving the body.

Some bones have a chiefly protective function. An example is the skull, which encloses the brain, the back of the eyeball, and the inner ear. Some, such as the pelvis, are mainly supporting structures. Other bones, such as the jaw and the bones of the fingers, are concerned chiefly with movement. The bone marrow in the center manufactures blood cells. The bones themselves act as a storehouse of calcium, which must be maintained at a certain level in the blood for the body's normal chemical functioning.

Structure and Composition. Bone is not uniform in structure but is composed of several layers of different materials. The outermost layer, the periosteum, is a thin, tough membrane of fibrous tissue. It gives support to the tendons that secure the muscle to the bone and also serves as a protective sheath. This membrane encloses all bones completely except at the joints where there is a layer of cartilage. Beneath the periosteum lie the dense, hard layers of bone tissue called compact bone. Its composition is fibrous rather than solid and it gives bone its resiliency. Encased within these layers is the tissue that makes up most of the volume of bone, called cancellous or spongy bone because it contains little hollows like those of a sponge. The innermost portion of the bone is a hollow cavity containing marrow. Blood vessels course through every layer of bone, carrying nutritive elements, oxygen, and other products. Bone tissue also contains a large number of nerves. The basic chemical in bone, which gives bone its hardness and strength, is calcium phosphate.

Development. Cartilage forms the major part of bone in the very young; this accounts for the great flexibility and resiliency of the infant skeleton. Gradually, calcium phosphate collects in the cartilage, and it becomes harder and more brittle. Some of the cartilage cells break loose, so that channels develop in the bone shaft. Blood vessels enter the channels, bearing with them small cells of connective tissue, some of which become osteoblasts, cells that form true bone. The osteoblasts enter the hardened cartilage, forming layers of hard, firm bone. Other cells, called osteoclasts, work to tear down old or excess bone structure, allowing the osteoblasts to rebuild with new bone. This renewal continues throughout life, although it slows down with age.

Cartilage formation and the subsequent replacement of cartilage by hard material is the mechanism by which bones grow in size. During the period of bone growth, cartilage grows over the hardened portion of bone. In time, this layer of cartilage hardens as calcium phosphate is added, and a fresh layer grows over it, and it too hardens. The process continues until the body reaches full growth. Long bones grow in length because of special cross-sectional layers of cartilage located near the flared ends of the bone. These harden and new cartilage is produced by the same process as previously described.

Bone Disorders. fracture, a break in the bone, is the most common injury to the bone; it may be closed, with no break in the skin, or open, with penetration of the skin and exposure of portions of the broken bone. osteoporosis is excessive brittleness and porosity of bone in the aged. osteomyelitis is a bone infection similar to a boil on the skin, but much more serious because blood supply to bone is less exquisite than that to other body organs and bone metabolizes more slowly, so that the infection can destroy the bone and invade other body tissues. osteomalacia is the term used for rickets when it occurs in adults. In these diseases there is softening of the bones, due to inadequate concentration of calcium or phosphorus in the body. The usual cause is deficiency of vitamin D, which is required for utilization of calcium and phosphorus by the body. In osteitis fibrosa cystica, bone is replaced by fibrous tissue because of abnormal calcium metabolism. The condition usually is due to overactivity of the parathyroid glands. osteoma refers to abnormal new growth, either benign or malignant, of the tissue of the bones. Although it is not common, it may occur in any of the bones of the body, and at any age.

alveolar bone the thin layer of bone making up the bony processes of the maxilla and mandible, surrounding and containing the teeth; it is pierced by many small blood vessels, lymphatic vessels, and nerves.

ankle bone talus.

brittle b's osteogenesis imperfecta.

bundle bone lamina dura.

cancellated bone (cancellous bone) bone composed of thin intersecting lamellae, usually found internal to compact bone.

cartilage bone bone developing within cartilage, ossification taking place within a cartilage model, as opposed to membranous bone.

cheek bone zygomatic bone.

collar bone clavicle.

compact bone bone substance that is dense and hard.

cortical bone the compact bone of the shaft of a bone that surrounds the marrow cavity.

cranial b's the bones that constitute the cranium, including the occipital, sphenoid, temporal, parietal, frontal, ethmoid, lacrimal, and nasal bones, the inferior nasal concha, and the vomer. Some authorities also include the maxilla, zygomatic bone, and palatine bone. See anatomic Table of Bones in the Appendices.

ethmoid bone the sievelike bone that forms a roof for the nasal fossae and part of the floor of the anterior cranial fossa. See anatomic Table of Bones in the Appendices.

facial b's the bones that form the skeleton of the face, including the hyoid, palatine, and zygomatic bones, the mandible, and the maxilla. Some authorities include the lacrimal bones, nasal bones, inferior nasal concha, and vomer and exclude the hyoid bone. See anatomic Table of Bones in the Appendices.

flat bone one whose thickness is slight, sometimes consisting of only a thin layer of compact bone, or of two layers with intervening cancellous bone and marrow; usually curved rather than flat.

frontal bone the bone at the anterior part of the skull. See anatomic Table of Bones in the Appendices.

heel bone calcaneus.

hip bone the ilium, ischium, and pubis as a unit. See anatomic Table of Bones in the Appendices.

hyoid bone a horseshoe-shaped bone at the base of the tongue. See anatomic Table of Bones in the Appendices. Called also lingual bone.

incisive bone the portion of the maxilla bearing the incisors; developmentally, it is the premaxilla, which in humans later fuses with the maxilla, but in most other vertebrates persists as a separate bone.

innominate bone hip bone.

jaw bone either the mandible (lower jaw) or the maxilla (upper jaw). See anatomic Table of Bones in the Appendices.

jugal bone zygomatic bone.

lingual bone hyoid bone.

long bone one whose length far exceeds its breadth and thickness.

malar bone zygomatic bone.

marble b's osteopetrosis.

mastoid bone mastoid part of temporal bone.

membrane bone (membranous bone) bone that develops within a connective tissue membrane, in contrast to cartilage bone.

occipital bone the bone constituting the back and part of the base of the skull. See anatomic Table of Bones in the Appendices.

parietal bone one of two bones forming the sides and roof of the cranium. See anatomic Table of Bones in the Appendices.

pelvic bone hip bone.

petrous bone petrous part of temporal bone.

pneumatic bone bone that contains air-filled spaces.

premaxillary bone premaxilla.

pterygoid bone pterygoid process.

rider's bone localized ossification sometimes seen on the inner aspect of the lower end of the tendon of the adductor muscle of the thigh in horseback riders.

shin bone tibia.

short bone one of approximately equal length, width, and thickness.

solid bone compact bone.

spongy bone cancellous bone.

squamous bone squamous part of temporal bone.

sutural bone any of the variable and irregularly shaped bones in the sutures between the bones of the skull. Called also wormian bone.

temporal bone one of two bones forming part of the lateral and inferior surfaces of the skull and containing the organs of hearing. See anatomic Table of Bones in the Appendices.

thigh bone femur.

turbinate bone a nasal concha.

tympanic bone tympanic part of temporal bone.

wormian bone sutural bone.

zygomatic bone the quadrilateral bone that forms a cheek. See anatomic Table of Bones in the Appendices.

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bone

1. the hard, rigid form of connective tissue constituting most of the skeleton of most vertebrates, composed chiefly of an organic component of collagenous matrix and cells and a mineral component of calcium phosphate and other salts.

2. any distinct piece of the skeleton of the body. For a named list of bones see Table 10.

3. describes conformation, substance, thickness and quality of bone structure in an animal, e.g. an animal with good bone. See also osseous.

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bone ash

analysis of the degree of mineralization of bone is done by an ash analysis in which the bone is heated at 600°C until there is no further weight loss.

bone atrophy

see osteoporosis.

brittle b's

see osteogenesis imperfecta.

bone callus

see callus (2).

cancellated bone, cancellous bone

bone composed of thin intersecting lamellae, usually found internal to compact bone. Called also spongy bone.

cartilage bone

bone developing within cartilage, ossification taking place within a cartilage model. Called also endochondral ossification.

bone cells

see osteocyte, osteoclast, osteoblast.

cheek bone

see zygomatic bone.

chevron bone

see hemal arch.

chondroid bone

has histological characteristics of both cartilage and bone; may develop in response to tensions from frequently changing directions.

bone clamp

strongly built, handheld, tong-like instrument with outcurving blades making a circle when closed for grasping a piece of bone shaft. The handles are ratcheted to give a firm grasp, and the faces of the blades have deep, crossways grooves.

compact bone

bone substance that is dense and noncancellous.

cortical bone

the compact bone of the shaft of a bone that surrounds the marrow cavity.

bone cyst

a discrete, grossly visible cavity, filled with fluid and often lined by a membrane. It may be located under cartilage (subchondral), be a single cavity (unicameral), filled with blood (aneurysmal) or contain epidermal cells (epidermoid).

Aneurysmal bone cyst. By permission from Slatter D, Textbook of Small Animal Surgery, Saunders, 2002

decalcified bone

a material for bone grafting. Prepared by treatment with hydrochloric acid, bone morphogenic protein is retained.

bone density

the degree of mineralization, usually demonstrable in radiographs.

bone discoloration

continuous intake of tetracycline colors bone of growing animals yellow; inherited or acquired porphyria discolors bone red-brown.

ectopic bone

bone which develops in abnormal sites. Needs to be differentiated from ectopic ossification and ectopic mineralization.

endochondral bone

bone formed by the ossification of cartilage. The means of lengthening of long bones. See also enchondral ossification.

entoglossal bone

the bone in a bird's tongue.

bone file, bone rasp

see bone rasp.

flat bone

one whose thickness is slight, sometimes consisting of only a thin layer of compact bone, or of two layers with intervening cancellated bone and marrow; usually curved rather than flat.

bone flour

finely ground bone used as a mineral supplement in animal feed to supply additional calcium and phosphorus. Needs to be properly sterilized.

bone fragility

the ease with which bone fractures depends to a large extent on the density of its compact bone, that is its degree of mineralization, which in turn depends on a number of factors including age, nutritional adequacy, state of pregnancy and lactation and exposure to weight bearing.

bone G1a protein

see osteocalcin.

bone infection

see osteitis, osteomyelitis, osteoarthritis.

intramembranous bone

bone formed within membrane or under the periosteum.

jugal bone

see zygomatic bone.

lamellar bone

mature bone in which the collagen fibers are in an orderly layered arrangement producing lamellae.

laminar bone

the formation of bone by the periosteum in layers, sometimes more than one layer at a time, to supplement the diaphyseal expansion of the bone. Is marked in farm animals and large dogs, and serves to accommodate the skeleton to the very rapid growth of the musculature.

lingual bone

see hyoid bone.

long bone

one whose length usually exceeds its breadth and thickness and which usually bears epiphyses at each extremity during growth.

Structure of typical long bone. By permission from Aspinall V, O'Reilly M, Introduction to Veterinary Anatomy and Physiology, Butterworth Heinemann, 2004

malar bone

see zygomatic bone.

marble b's

see osteopetrosis.

mastoid bone

the posterior part of the petrous temporal bone; the mastoid process.

bone matrix

the intercellular component of bone. It includes collagen and amorphous ground substance consisting mostly of mucopolysaccharides (chondroitin sulfate).

bone meal

a product made from meatless bones which are crushed and sterilized. The bones are derived from boning plants and retail outlets. The bonemeal is used as stock feed, fertilizer and in a number of industries. Care is needed in its preparation and in the selection of the bones because of the high risk of transmitting diseases including anthrax, salmonellosis, tuberculosis. A coarse grade of bone flour (see above). Prohibited from being used as a feed in many countries as part of programs to control or prevent bovine spongiform encephalopathy.

membrane bone

bone that develops within a connective tissue membrane.

metaplastic bone

bone formed by connective tissue by redifferentiation of mesenchymal cells.

bone mineral

principally calcium and phosphorus but includes also magnesium and, to a lesser extent, potassium and fluorine. Consisting mainly of hydrated calcium phosphate (apatite) and calcium carbonate.

bone modeling

the sum of the activities of the endosteum and periosteum of bone to produce bone forms.

bone neoplasm

includes fibroma, fibrosarcoma, chondroma, osteochondroma, chondrosarcoma, osteoma, osteosarcoma.

pelvic bone

hip bone.

perilacunar bone

low density bone around the lacunae of bone which contains much amorphous mineral. In this form the mineral is labile and therefore important in the maintenance of calcium homeostasis.

periosteal bone

bone deposition by the periosteum in successive laminae; the bone formation in new bone and in a callus, beginning as fibrocellular tissue forming from the endosteum and periosteum, followed by calcification and bone formation.

bone pinning

see pinning.

pneumatic bone

bone that contains air-filled spaces.

premaxillary bone

see premaxilla.

pterygoid bone

a small skull bone that articulates with the sphenoid.

bone remodeling unit

osteoclasts, osteoblasts and their progenitors, the basal metabolic unit of bone.

bone sand

remnants of bone trabeculae destroyed in osteomyelitis and sequestered in pus.

bone sealant

a composition of beeswax and isopropylpalmitate used to seal the cut end of bone and stop the oozing of blood.

shin bone

see tibia and cannon bone.

short bone

one of approximately equal length, width and thickness, usually without epiphyses.

solid bone

compact bone.

spongy bone

cancellous bone.

bone structural unit

see basic multicell unit.

sutural b's

variable and irregularly shaped bones in the sutures between the bones of the skull.

bone tumor

includes cartilage-forming tumors (chondroma, osteochondroma, chondrosarcoma, multilobular tumor) and bone-forming tumors (osteoma, osteosarcoma).

tympanic bone

the part of the temporal bone surrounding the middle ear.

bone wax

see bone sealant (above).

wormian b's

sutural bones.

woven bone

primitive bone with coarse collagen bundles arranged in a disorderly fashion and replaced subsequently by lamellar bone.