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Elijah Davis
Elijah Davis

Ginglymoid Joint

A hinge joint (ginglymus or ginglymoid) is a bone joint in which the articular surfaces are molded to each other in such a manner as to permit motion only in one plane. According to one classification system they are said to be uniaxial (having one degree of freedom).[1] The direction which the distal bone takes in this motion is seldom in the same plane as that of the axis of the proximal bone; there is usually a certain amount of deviation from the straight line during flexion.

ginglymoid joint

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The best examples of ginglymoid joints are the Interphalangeal joints of the hand and those of the foot and the joint between the humerus and ulna. The knee joints and ankle joints are less typical, as they allow a slight degree of rotation or of side-to-side movement in certain positions of the limb. The knee is the largest hinge joint in the human body.

(joynt) [Fr. jointe, fr. L. junctio, a joining] The place where two or more bones meet. Some joints are fixed or immobile attachments of bones; other joints allow the bones to move along each other. A joint usually has a thin, smooth articular cartilage on each bony surface and is enclosed by a joint capsule of fibrous connective tissue. A joint is classified as immovable (synarthrodial), slightly movable (amphiarthrodial), or freely movable (diarthrodial). A synarthrodial joint is one in which the two bones are separated only by an intervening membrane, such as the cranial sutures. An amphiarthrodial joint is one having a fibrocartilaginous disk between the bony surfaces (symphysis), such as the symphysis pubis; or one with a ligament uniting the two bones (syndesmosis), such as the tibiofibular articulation. A diarthrodial joint is one in which the adjoining bone ends are covered with a thin cartilaginous sheet and joined by a joint capsule lined by a synovial membrane, which secretes synovial fluid. SYN: SEE: arthrosis (1)TYPES OF JOINTS MOVEMENTJoints are also grouped according to their motion: ball-and-socket (enarthrodial); hinge (ginglymoid); condyloid; pivot (trochoid); gliding (arthrodial); and saddle.Joints can move in four ways: gliding, in which one bony surface glides on another without angular or rotatory movement; angulation, occurring only between long bones, increasing or decreasing the angle between the bones; circumduction, occurring in joints composed of the head of a bone and an articular cavity, the long bone describing a series of circles, the whole forming a cone; and rotation, in which a bone moves about a central axis without moving from this axis. Angular movement, if it occurs forward, is called flexion; if backward, extension; if away from the body, abduction; and toward the median plane of the body, adduction.Because of their location and constant use, joints are prone to stress, injury, and inflammation. The main diseases affecting the joints are rheumatic fever, rheumatoid arthritis, osteoarthritis, and gout. Injuries comprise contusions, sprains, dislocations, and penetrating wounds.

A joint that permits rotation of a bone, the joint being formed by a pivot-like process that turns within a ring, or by a ringlike structure that turns on a pivot. SYN: SEE: rotary joint; SEE: trochoid joint

Either of the encapsulated double synovial joints between the condylar processes of the mandible and the temporal bones of the cranium. These joints are separated by an articular disk and function as an upper gliding joint and a lower modified hinge or ginglymoid joint.

SUMMARY: This article focuses on important morphofunctional features of the temporomandibular joint, particularly those related to the ultrastructure and anterosuperior attachment of the joint capsule and condylar position at the end of the mouth-opening movement.

Some features of the TMJ are not common in skeletal joints. The TMJ is a double bilateral synovial joint to a single bone, which is only observed in two other synovial articulations: the atlanto-occipital and the sacroiliac joints; the latter is considered by many authors as a synchondrosis. Besides, the bone surfaces of the TMJ are covered by fibrous, not cartilaginous tissue as is the case in the acromioclavicular and sternoclavicular joints (Ten Cate, 1998).

Despite the difficulty in classifying the TMJ from a morphofunctional point of view, it is best described as a synovial ginglymoid and sliding joint of complex biaxial movements, because it performs rotation, translation, right and left lateral excursion, protrusion and retrusion. This characterization is more directly related to the morphofunctionality of the TMJ, and it is worth stressing its capacity to perform one of the greatest sliding movements of synovial joints, which allows large mouth opening.

Heffez et al. (1995), however, called attention to the fact that less contrast could be injected in the superior joint space in cadavers (average of 1.2 ml) than in vivo (only 0.4 to 0.5 ml). This fact seems to create an observation bias in evaluation of the insertion of the TMJ capsule by means of intra-articular injection of contrast agent.

Thus, one can see that the anterior superior insertion of the TMJ capsule and the amplitude of condyle translation remain controversial. There is no doubt, however, that capsule insertions determine the amplitude of the movements of the bone components in any joint.

Johansson, A. S. & Isberg, A. The anterosuperior insertion of the temporomandibular joint capsule and condylar mobility in joints with and without internal derangement. J. Oral Maxillofac. Surg., 49(11):1142-8, 1991.

Morphology of keratinised toe pads and foot scales, hinging of foot joints and claw shape and size all inform the grasping ability, cursoriality and feeding mode of living birds. Presented here is morphological evidence from the fossil feet of early theropod flyers. Foot soft tissues and joint articulations are qualitatively assessed using laser-stimulated fluorescence. Pedal claw shape and size are quantitatively analysed using traditional morphometrics. We interpret these foot data among existing evidence to better understand the evolutionary ecology of early theropod flyers. Jurassic flyers like Anchiornis and Archaeopteryx show adaptations suggestive of relatively ground-dwelling lifestyles. Early Cretaceous flyers then diversify into more aerial lifestyles, including generalists like Confuciusornis and specialists like the climbing Fortunguavis. Some early birds, like the Late Jurassic Berlin Archaeopteryx and Early Cretaceous Sapeornis, show complex ecologies seemingly unique among sampled modern birds. As a non-bird flyer, finding affinities of Microraptor to a more specialised raptorial lifestyle is unexpected. Its hawk-like characteristics are rare among known theropod flyers of the time suggesting that some non-bird flyers perform specialised roles filled by birds today. We demonstrate diverse ecological profiles among early theropod flyers, changing as flight developed, and some non-bird flyers have more complex ecological roles.

The ecology of early theropod flyers has been revealed in part by prior studies involving their anatomy, diet, locomotor abilities and habitats1,2,3,4,5,6,7,8. The foot anatomy of living birds varies greatly due to the diverse ecological roles they perform9,10,11,12. These ecological roles include leg-based launch in flying birds, perching, wading and swimming, as well as prey capture and dismemberment13,14. In the context of existing ecological data1,2,3,4,5,6,7,8, we refine the ecological profiles of early theropod flyers by comparing their toe pads, foot scales, claws and joints with living birds. In particular, we combine soft tissue and joint details visible in the best-preserved specimens and under laser-stimulated fluorescence (LSF)15, along with quantitative analysis of claw shape and size using traditional morphometrics.

Two main types of toe pad arrangement are typically present in modern birds18,19. The arthral condition, in which the toe pad is aligned with the interphalangeal joint (Fig. 1), is characteristic of the raptorial species. The mesarthral condition, in which the toe pad is aligned with the phalanx itself (Fig. 1), is found in non-raptorial forms. These two conditions do not include pads that cover more than one entire phalanx, although the latter are also widespread among extant birds20. Toe pad position (i.e., mesarthral vs. arthral) in modern birds appears to be driven by prey choice and feeding behaviour rather than common ancestry10, although there is also considerable variation within species and even individuals20. Arthral toe pads are found in a range of non-avialan theropods that are mostly associated with a carnivory-dominated diet (e.g., carcharodontosaurians, tyrannosauroids and dromaeosaurids21,22). However, since carnivory is the ancestral condition of theropods23,24,25 and arthral pads have been recently identified in the ornithischian Psittacosaurus26, common ancestry cannot be ruled out as a driver of their toe pad position.

Modern birds with an arthral and mesarthral arrangement both activate the tendon-locking mechanism (TLM) during grasping27. The TLM maintains digit flexion during perching or prey capture without additional muscular requirements, and is found in nearly all modern birds (excluding palaeognaths, e.g., emus, rheas)27. The pad-over-joint arthral arrangement activates the TLM more efficiently than the pad-over-phalanx mesarthral arrangement, suggesting it is a grasping adaption10,27. However, it is unknown if the observed modern relationship between the TLM and toe pad alignment was also present in early flyers because the TLM is not found in palaeognaths and its fossil record is poor. Thus, arthral arrangement of the toe pads is not considered a specialised grasping adaptation in our fossil analysis. 041b061a72


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