bone conduction

conduction /con·duc·tion/ (-shun) conveyance of energy, as of heat, sound, or electricity.conduc´tive

---

aberrant conduction  cardiac conduction through pathways not normally conducting cardiac impulses, particularly through ventricular tissue.

aerotympanal conduction  conduction of sound waves to the ear through the air and the tympanum.

air conduction  conduction of sound waves to the inner ear through the external auditory canal and middle ear.

anterograde conduction  transmission of a cardiac impulse in the normal direction, from the sinus node to the ventricles, particularly forward conduction through the atrioventricular node.

Diagrammatic view of the conducting system of the heart, showing anterograde conduction of the cardiac impulse.

bone conduction  conduction of sound waves to the inner ear through the bones of the skull.

concealed conduction  incomplete penetration of a propagating impulse through the cardiac conducting system such that electrocardiograms reveal no evidence of transmission but the behavior of one or more subsequent impulses is somehow affected.

concealed retrograde conduction  retrograde conduction blocked in the atrioventricular node; it does not produce an extra P wave but leaves the node refractory to the next normal sinus beat.

decremental conduction  delay or failure of propagation of an impulse in the atrioventricular node resulting from progressive decrease in the rate of the rise and amplitude of the action potential as it spreads through the node.

retrograde conduction  transmission of a cardiac impulse backward in the ventricular to atrial direction, particularly conduction from the atrioventricular node into the atria.

saltatory conduction  the passage of a potential from node to node of a nerve fiber, rather than along the membrane.

---

bone conduction

n.

The process by which sound waves are transmitted to the inner ear by the cranial bones without traveling through the air in the ear canal.

---

conduction [kon-duk´shun]

conveyance of energy, as of heat, sound, or electricity.

aberrant ventricular conduction the temporary abnormal intraventricular conduction of supraventricular impulses; called also ventricular aberration.

aerial conduction (air conduction) conduction of sound waves to the organ of hearing in the inner ear through the air.

anterograde conduction

1. forward conduction of impulses through a nerve.

2. in the heart, conduction of impulses from atria to ventricles.

atrioventricular conduction (AV conduction) the conduction of atrial impulses through the atrioventricular node and the His-Purkinje system to the ventricles.

bone conduction conduction of sound waves to the inner ear through the bones of the skull.

concealed conduction conduction that is not seen on the surface electrocardiogram but may be detected by its effect on subsequent impulses; common examples are the incomplete penetration of the AV junction during atrial fibrillation, the Wenckebach type penetration during atrial flutter, and the retrograde incomplete penetration following ventricular ectopic beats.

decremental conduction a gradual decrease in the stimuli and response along a pathway of conduction; it occurs in nerve fibers with reduced membrane potentials.

retrograde conduction transmission of a cardiac impulse backward in the ventricular to atrial direction; particularly, conduction from the atrioventricular node into the atria.

saltatory conduction the rapid passage of an electric potential between the nodes of ranvier in myelinated nerve fibers, rather than along the full length of the membrane.

---

bone,

n 1. the material of the skeletons of the tissue composing bones.
n 2. dense, hard, and slightly elastic connective tissue in which the fibers are impregnated with a form of calcium phosphate similar to hydroxyapatite.
3. the bones of the human skeleton.
n 4. a single element of the skeleton such as a rib or femur.

bone, alveolar

n the specialized bone structure that contains the alveoli or sockets of the teeth and supports the teeth.

bone, alveolar, architecture,

n the structural pattern of the alveolar bone and its subjacent latticework of supporting bone. The alveolar bone is thin and compact adjacent to the periodontal ligament. The trabecular bone connects and reinforces the individual alveoli. The architecture of a bone is the result of functional stimuli to that bone; the stimuli vary according to type, intensity, and duration.

bone, alveolar, metabolism,

n the metabolic activity occurring within alveolar bone, which is generally slower than that occurring within metaphyseal bone but more rapid than that of diaphyseal bone.

bone apposition,

n See bone deposition.

bone augmentation,

n a procedure used to build or enhance bone. It refers to either bone grafting or bone growing. Bone augmentation materials are classified as osseous, in which bone or bony substitutes are used to form new bone, or osseous conductive, in which these materials provide a platform for regeneration without taking part in actual bone formation.

bone, basal,

n the part of the mandible and maxilla from which the alveolar process develops.

bone, bundle,

n the bone forming the immediate bone attachment of the numerous bundles of collagen fibers of the periodontal ligament that have been incorporated into the bone.

bone bur,

n a drill designed to cut into bone.

bone, cadaver,

n bone that has been donated for medical purposes from one person to another; used especially in bone grafting procedures. See also allogenic and allografts.

bone calcium content,

n the amount of calcium stored in bone tissue. Plasma calcium is in constant exchange with the calcium of the extracellular fluid and bones. The parathyroid gland maintains the constancy of the calcium concentration in the plasma. The bones serve as a reservoir of calcium and phosphate to provide for the other needs of the body and supply minerals for deposition in the skeleton.

bone, cancellous (spongy bone, supporting bone, trabecular bone),

n the bone that forms a trabecular network, surrounds marrow spaces that may contain either fatty or hematopoietic tissue, lies subjacent to the cortical bone, and makes up the main portion of a bone.

bone, cancellous, atrophy of disuse

n the wasting of bone tissue occurring with loss of function of a part (e.g., a tooth). The supporting bone assumes an osteoporotic nature, and the marrow remains fatty or hematopoietic.

bone cells,

n.pl the group includes osteoblasts, osteocytes, osteoclasts, and osteoprogenitor cells.

bone changes, mechanical factors,

n.pl the pressure and tension forces that play an important role in determining bone structure. Improperly controlled appliances can resorb bone faster than deposition can occur, causing mobile teeth and traumatic occlusion. Poor vascularity is a concomitant cause of undue pressure and tension and may inhibit repair and cause necrosis.

bone chips,

n.pl the small pieces of cancellous bone generally used to fill in bony defects and precipitate recalcification.

bone, compact,

n the hard, dense bone composing the outer cortical layer and consisting of periosteal bone, endosteal bone, and haversian systems.

bone conduction,

n See conduction, bone.

bone crest,

n the most coronal portion of alveolar bone.

bone cyst,

n 1. a vascular cyst eccentrically placed within a bone.
n 2. ostitis fibrosa cystica, a parathyroid disorder characterized by cyst formation and the replacement of bone tissue with fibrous connective tissue.

bone defects, angular,

n.pl the usually localized anomalies that occur in the crestal bone as the result of both periodontal inflammation and occlusive trauma.

bone density,

n the compactness of bone tissue. The demonstration of bone density by means of radiographs directly depends on the quantity of inorganic salts contained in the bone tissue.

bone deposition,

n the apposition or formation of new bone as a normal physiologic process.

bone development,

n B See bone, endochondral, formation; bone formation; and bone, intramembranous, formation.

bone, effect of external radiation to,

n damage to the bones of adults is most often seen after heavy and localized radiation treatment.

bone, endochondral

n a bone that is developed in relation to antecedent cartilages (e.g., long bones, mandible). See also bone, intramembranous.

bone, endochondral, formation,

n a replacement of previously formed embryonic cartilage with an adult bony structure. The actual replacement of cartilage by bone is only part of the process, however; much of the bone is laid down directly external to the embryonic cartilage. See also bone, membrane, formation.

bone formation,

n the deposition of an organic mucopolysaccharide matrix (osteoid) that is subsequently mineralized with calcium salts. See also bone apposition and bone deposition.

bone graft, autogenous

n See graft, autogenous bone.

bone graft, donor site,

n See donor site.

bone graft, onlay,

n See graft, onlay bone.

bone graft, recipient site,

n See recipient site.

bone groove,

n an osteotomy into or near the crest of the alveolar ridge for placement of an endosteal blade type of implant.

bone groove, canted,

n an osteotomy sloped to avoid the mandibular canal or keep the implant infrastructure within the medullary confines.

bone, horizontal loss of,

n a resorption of bone caused by periodontal inflammation in which the bone crest remains even with the cementoenamel junctions of two adjoining teeth. The condition may be localized or generalized.

Horizontal bone loss.

bone, internal reconstruction of,

n the formation of bone on the tensional side of the periodontal ligament with concurrent resorption from the marrow space; contralaterally, resorption of alveolar bone with apposition from the endosteum in the marrow space.

bone, interproximal,

n the bone that forms the septa between the teeth; consists primarily of a spongy supporting bone covered by a layer of cortical bone. See also septum, interdental.

bone, intramembranous,

n a bone developed within a membrane but having no associated cartilage (e.g., parietal, frontal, bones of upper face). See also bone, endochondral.

bone, intramembranous, formation,

n membrane bone forms directly from the mesenchyme, first as a thin, flattened, irregular bony plate or membrane in the dermis and gradually expanding at its margins and becoming thickened by the deposition of successive layers of additional bone on the inner and outer surfaces. See also bone, endochondral, formation.

bone involvement,

n changes in the alveolar and supporting bone occurring as a sequel to or accompanying inflammatory or dystrophic disease; usually of a resorptive nature.

n the small, fragile, paired facial bone that helps form a part of the orbital wall and also a small part of the nasal cavity. The bone has four borders and two surfaces that articulate with four other facial bones.

bone lamella,

n bone having the appearance of layers of thin leaves or plates. This appearance is produced by lines representing periods of inactivity of bone formation.

bone, malar (zygomatic bone), frontal process of,

n a prominence on the zygomatic bone (cheekbone) that forms the anterior lateral orbital wall.

n a prominence on the zygomatic bone (cheekbone) that forms part of the inferior rim of the orbit and a small part of the orbital wall.

n a prominence on the inferior aspect of the zygomatic bone (cheekbone) that articulates with the zygomatic process of temporal bone to form the zygomatic arch.

bone, marble,

n See osteopetrosis.

bone marrow,

n the soft vascular tissue that fills bone cavities and cancellous bone spaces and consists primarily of fat cells, hematopoietic cells, and osteogenetic reticular cells.

bone marrow transplant,

n the transplantation of bone marrow from healthy donors to stimulate production of formed blood cells. It is used in treatment of hematopoietic or lymphoreticular diseases such as aplastic anemia, leukemia, immune deficiency syndromes, and acute radiation syndrome.

bone membranes,

n.pl the membrane structures associated with the growth, development, and repair of bone. They include the periosteum, a connective tissue layer adjacent to bone surfaces; periodontal ligament, a modified periosteum associated with tooth structure; and endosteum, a thin layer of connective tissue lining the walls of the bone marrow spaces.

bone, microscopic appearance of,

n the composition of bone tissue as viewed under a microscope. Microscopically, bone is composed of osteocytes embedded within lacunae in a calcified intercellular matrix. Extending from the lacunae are small canals called canaliculi, which communicate with canaliculi of adjacent lacunae. Through this system of canals, nutrient material reaches the osteocytes and provides avenues for the removal of waste products of metabolism. It is deposited in incremental layers (lamellae) around haversian canals, the lamellae toward the surface of the bone being more or less parallel to it.

bone mineral content, chemistry of,

n the hardness of bone results from its mineral content in the organic matrix. The minerals (commonly designated as bone salts) and the organic matrix make up the interstitial substance of bone. The bone salts consist essentially of hydroxyapatite (Ca₁₀[PO₄]₆[OH₂]), carbon dioxide, and water, with small amounts of other ions.

bone morphogenetic protein (BMP),

n See protein, bone morphogenetic (BMP).

bone, normal level of,

n the distance from the interdental bone crest to the cementoenamel junction in healthy teeth, usually 1 to 1.5 mm.

n the saucer-shaped cranial bone that forms the most posterior part of the skull; the spinal cord passes through the foramen magnum, an opening at its base.

bone onlay,

n See graft, onlay bone.

bone, perichondrial

n bone that is deposited in concentric layers around the long shaft of the bone in a manner similar to that of the growth of endochondral bone.

bone, physical properties of,

n a compact bone has the following physical characteristics: specific gravity, 1.92 to 1.99; tensile strength, 13,000 to 17,000 psi; compressive strength, 18,000 to 24,000 psi; compressive strength parallel to the long axis, 7150 psi; compressive strength at right angles to the long axis, 10,800 psi. These physical characteristics make bone particularly suitable for carrying out its functions of weight bearing, leverage, and protection of vulnerable viscera.

bone rarefaction

n a decreased density of bone such as a decrease in weight per unit of volume.

bone recession,

n See recession, bone.

bone, resorption and repair of,

n an adaptive physiologic mechanism occurring as long as the individual retains the natural dentition. See also resorption of bone.

bone, resting lines in,

n.pl the regular lines created by alternating periods of bone formation and rest, giving a tierlike appearance to lamellar bone.

bone, reversal lines in,

n.pl the irregular lines containing concavities directed away from the bundle bone and serving as histologic indications that resorption has taken place up to that line from the marrow side.

bone sequestrum,

n See sequestrum.

bone, spongy,

n See bone, cancellous.

bone support,

n the amount of alveolar and trabecular bone adjacent to a tooth that can provide attachment, investment, and support for the tooth.

bone, supporting,

n See bone, cancellous.

bone, supporting, atrophy of disuse,

n See bone, cancellous, atrophy of disuse.

bone surgery,

n See surgery, osseous.

bone, thickened margin of,

n the widening of the crest of the alveolus, primarily on the buccal and lingual aspects, varying from a thick ledge to a “beading” of the bone margin; results in a more or less bulbous contour of the gingival tissue overlying it.

bone, trabecular

n See bone, cancellous.

bone, vertical loss of,

n a resorption of bone caused by periodontal inflammation and occlusal trauma in which the bone crest is below the cementoenamel junctions of two adjoining teeth. It can be localized (mainly) or generalized.

bone, vertical plates of the palatine,

n the thin, oblong-shaped bone with two surfaces and four borders. It helps to form the floor of the orbit, the outer wall of the nasal cavity, and several adjoining structures.

bone volume (mass), age-affecting,

n decreases that occur in human body bone mass after age 40. Diet and exercise may be contributing factors.

bone wax,

n See wax, bone.

bone, woven,

n a character and pattern of bone resulting from the interweaving of broad bands of bone.

bone(s), cranial,

n the eight bones that make up the skull and protect the brain and include the ethmoid, frontal, occipital, sphenoid, two parietal, and two temporal bones.

bone(s), facial,

n the 14 bones that include the mandible, maxilla, frontal bones, nasal bones, and zygoma. With the exception of the mandible, maxilla, and vomer bones, the bones of the face occur in pairs, thus accounting for facial symmetry. They provide the framework for the face, serve as entry points for the digestive and respiratory systems, and provide the attachments for the muscles controlling facial expression.

bone(s), horizontal plates of palatine,

n the bones that form the posterior part of the hard palate and consist of four borders and two surfaces.

---

conduction,

n the carrying of sound waves, heat, light, nerve impulses, and electricity.

conduction, air,

n the process of transmitting sound waves to the cochlea by way of the outer and middle ear. In normal hearing, practically all sounds are transmitted in this way, except those of the hearer's own voice, which are transmitted partly by bone conduction.

conduction, bone,

n the transmission of sound waves or vibrations to the cochlea by way of the bones of the cranium.

conduction, impulse,

n the conduction of an impulse along the nerve fiber, accompanied by an alteration of the electrical potential of the fiber tissue and an exchange of electrolytes across the nerve fiber membrane.

---

conduction, conductive

conveyance of energy, as of heat, sound or electricity.

---

accessory tract atrioventricular conduction

permits a sinus impulse from the atria to ventricles to precede that carried by the normal atrioventricular conduction system. Arrhythmia results, the particular electrocardiographic characteristics depending on the pathway(s) involved. See also wolff-parkinson-white syndrome.

aerial conduction, air conduction

conduction of sound waves to the organ of hearing through the air.

conduction anesthesia

local anesthesia produced by the injection of an anesthetic agent close to a nerve in order to prevent transmission of nerve impulses along it.

bone conduction

conduction of sound waves to the inner ear through the bones of the skull.

conduction disorder

abnormalities in the conduction pathways of the heart.

James accessory conduction

see james fibers.

conduction system

the system comprises the sinoatrial and atrioventricular nodes, atrioventricular bundle and Purkinje fibers.

Conduction system of the heart. By permission from Cunningham JG, Textbook of Veterinary Physiology, Saunders, 2002

conduction time

an indicator of a peripheral nerve's ability to carry an impulse; measured during electromyography. A nerve that has undergone Wallerian degeneration is unable to carry an impulse. Severe loss of myelin results in a prolonged conduction time.