zygomatic bone (redirected from Cheek 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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zygomatic bone

n.

A quadrilateral bone that forms the cheek prominence and articulates with the frontal, sphenoid, temporal, and maxillary bones. Also called cheekbone, jugal bone, malar bone, zygoma.

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zygomatic bone

Etymology: Gk, zygon + AS, ban

one of the pair of bones that forms the prominence of the cheek, the lower part of the orbit of the eye, and parts of the temporal and infratemporal fossae.

Zygomatic 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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zygomatic

pertaining to zygomatic bone.

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zygomatic arch

the arch formed by the processes of the zygomatic and temporal bones.

zygomatic bone

the bone forming the hard part of the cheek and the lower, lateral portion of the rim of the orbit. See also Table 10.

zygomatic gland

a salivary gland, formerly known as the orbital or upper molar gland, best developed in carnivores; located above the zygomatic arch and below the eye. Enlargement or mucocele of the gland causes exophthalmos.

zygomatic mucocoele

accumulation of salivary secretions from the zygomatic gland. It appears as a protruding mass under the conjunctiva of the lower eyelid.

zygomatic process

a projection from the frontal or temporal bone, or from the maxilla, by which they articulate with the zygomatic bone.

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orbit 

A rigid bony cavity in the skull which contains an eyeball, orbital fat, the extraocular muscles, the optic nerve, nerves and blood vessels, lacrimal system and fibrous tissue of various kinds. This packing serves to keep the eyeball reasonably well fixed in place as it rotates. The orbital cavity has the approximate form of a pyramid. The walls of the orbital cavity are formed by seven bones. The medial wall of the orbit consists of: (1) the frontal process of the maxilla (maxillary); (2) the lacrimal bone; (3) the lamina papyracea of the ethmoid; and (4) a small part of the body of the sphenoid. The floor of the orbit consists of: (1) the orbital plate of the maxilla; (2) the orbital surface of the zygomatic (malar) bone and (3) the orbital process of the palatine bone. The lateral wall of the orbit consists of (1) the orbital surface of the greater wing of the sphenoid, and (2) the orbital surface of the zygomatic. The roof of the orbit is made up mainly by the frontal bone and behind this by the lesser wing of the sphenoid. The orbit is lined with a membrane of tissue called the periorbita (or orbital periosteum) which extends to the orbital margin (anterior rim of the orbit) where it becomes continuous with the periosteum covering the facial bones. The periorbita is loosely attached to the bones except at sutures, foramina and the orbital margin where it is firmly attached. The bones are much thicker at the margin (rim) than they are along the walls of the orbital cavity. There are many apertures and gaps in the orbit through which blood vessels and nerves pass (see Table O4). See orbital axis; optic canal; inferior orbital fissure; superior orbital fissure; orbital fracture; cavernous haemangioma; lamina papyracea.

Table O3 Bones forming the walls of the orbit
roof	medial wall
1. frontal	1. maxilla
2. lesser wing of sphenoid	2. lacrimal
	3. ethmoid
	4. sphenoid
floor	lateral wall
1. maxilla	1. greater wing of sphenoid
2. zygomatic
3. palatine	2. zygomatic

Table O4 Orbital apertures
aperture	location	contents
optic canal	at the apex (in lesser sphenoid)	optic nerve ophthalmic artery sympathetic nerve fibres
superior orbital fissure	at the apex (gap between greater and lesser sphenoid)	III, IV, V, VI nerves sympathetic nerve fibres ophthalmic vein recurrent lacrimal artery
inferior orbital fissure	between lateral wall and posterior part of the floor	infraorbital nerve zygomatic nerve branch of inferior ophthalmic vein nerve fibres from the pterygopalatine (sphenopalatine) ganglion to orbital periosteum
ethmoidal foramina (anterior and post.)	medial wall (frontal/ethmoidal suture)	ethmoidal vessels ethmoidal nerve/external nasal nerve
zygomatic foramen	lateral wall	zygomatic nerve and vessels
nasolacrimal canal	medial wall (maxilla/lacrimal)	nasolacrimal duct