Bone is living mineralized connective tissue forming major parts of the vertebrate endoskeleton. Its extracellular matrix combines organic material with mineral, supporting both toughness and stiffness. Cells continually remodel it, so a bone is a regulated tissue rather than an inert stone.
The patella is a sesamoid bone within the knee-extension apparatus. It receives the quadriceps tendon proximally and connects through the patellar ligament distally. By changing the geometry of this force-transmission path, it influences the leverage of knee extension.
An epiphysis is the end region of a developing long bone, associated with a secondary ossification center. During growth, the growth-plate region separates it from the shaft-side region. The developmental term should be distinguished from the unrelated historical use for the pineal organ.
The mineral-rich residue left after combustion of bone organic material. It contains calcium phosphates and should not automatically be treated as pure tricalcium phosphate.
An osteophyte is a bony outgrowth, commonly at a joint margin in a remodeling or degenerative process. Its presence is a structural finding rather than a direct measure of pain or functional impairment. Location and relation to adjacent structures affect its significance.
The zygomatic bone forms part of the cheek prominence and lateral orbital boundary. Its connections with neighboring bones help transmit forces through the face. Its external prominence and contribution to the orbit are different aspects of one structural element.
The lacrimal bone is a small bone in the medial orbital wall associated with the lacrimal drainage region. Its position contributes to the space around the lacrimal sac. It is structurally distinct from the secretory lacrimal gland despite the shared name.
The ethmoid bone contributes to the skull base, nasal cavity and medial orbital walls. Its perforated superior region permits passage of olfactory nerve fibers. One bone therefore participates in several anatomical boundaries and in a sensory pathway.
The sphenoid bone is a central skull-base bone with contributions to the orbit and middle cranial region. Its openings and processes relate to multiple nerves, vessels and muscular attachments. That central position makes it important for understanding neighboring skull compartments.
Bone marrow is tissue within the internal spaces of bones. Hematopoietic regions produce blood cells, while adipose-rich regions have a different composition. Marrow is therefore not simply an empty bone cavity or the mineralized bone matrix itself.
A parietal bone forms much of the superior and lateral cranial vault. The paired bones meet near the midline and join other skull bones through sutures. Their broad surfaces contribute protection while the junctions have distinct developmental relationships.
The frontal bone forms the forehead and contributes to the orbital roofs and anterior cranial floor. Its internal and external surfaces relate respectively to intracranial and facial structures. A surface landmark therefore does not reveal every deeper boundary made by the same bone.
Formation of bone. Dermal, perichondral and endochondral modes should be distinguished from mineral deposition in cartilage.
A skull-roof bone formed by integration of frontal and parietal components, characteristic of frogs and some other vertebrates.
A skeletal element associated with the vertebral axis. Reduction of free ribs is part of the characteristic frog body organization.
The maxilla is a major upper-jaw bone contributing to the upper dental arch, hard palate, nasal region and orbit. Its several processes connect these regions structurally. The term refers to the bone, rather than all soft tissues of the upper jaw.
The premaxilla is the anterior upper-jaw skeletal element that carries or is associated with the front tooth-bearing region in many vertebrates. Its adult separation or fusion varies among lineages. Comparative identity cannot therefore be inferred solely from whether a visible suture persists.
bone deposited during replacement of a cartilaginous skeletal template. It should be distinguished from calcified cartilage and a superficial perichondral bone layer.
bone forming within dermal or related connective tissues rather than replacing a cartilaginous template. Large skull-roof bones and small surface odontodes are distinct anatomical organizations.
A dermal skeleton organized into relatively large plates or bones, contrasting with a covering dominated by small separate scales or odontodes.
The dorsal component of the pelvic girdle. Its anterior elongation is an important feature of the frog-lineage locomotor apparatus.
A vertebra is an individual element of the vertebral column. Its body, arch and processes have different supporting, protective and attachment roles, with regional variation. A sequence of vertebrae combines local motion at joints with protection of the neural axis.
A vertebra anterior to the sacrum. Counts depend on identifying the sacral articulation, not just numbering visible centra.
A bone of the jaw suspension in many nonmammalian vertebrates; its mobility contributes to avian cranial kinesis.
Bone tissue associated with rapid deposition. Rapid growth alone does not uniquely establish sustained endothermy.
A phalanx is a bone of an anatomical digit. Human fingers and toes have serially arranged phalanges, with counts differing among digits. The term identifies a segment within a digit rather than a whole finger or toe.
A metacarpal is a bone of the hand between the carpal region and a digit’s proximal phalanx. The series forms much of the palm’s skeletal framework. Different mobility at its proximal connections contributes to the distinct roles of the thumb and other fingers.
The principal proximal bone of the lower limb and the corresponding pelvic appendage in relevant comparisons.
One of the principal forearm bones, paired with the radius bone.
One of the two principal forearm bones; movement relative to the ulna contributes to forearm rotation.
The single proximal element of the upper limb and the corresponding pectoral appendage in relevant fossil comparisons.
