Arch Movement Research Articles

The windlass mechanism during normal walking and passive first metatarsalphalangeal joint extension

Objective. To assess the relationship between passive first metatarsophalangeal extension and rearfoot motion during walking on the windlass mechanism. Design. An in vivo study of the windlass mechanism during passive extension of the first metatarsophalangeal joint and walking. Background. Despite theoretical work regarding the windlass mechanism in cadavers, there is little research concerning its in vivo role. Methods. The amount of first metatarsophalangeal extension and medial longitudinal arch movement of the right foot in 20 subjects between the age of 22 and 55 years was recorded as they sat with their right hip, knee and ankle in 90 ° and their great toe passively extended. In addition, movement of the rearfoot was recorded while they walked. Results. The results of this study showed that the windlass mechanism is active during passive extension of the great toe. In addition, subjects could be divided into two groups ( immediate and delayed) based upon the timing of when the windlass mechanism began relative to passive extension of their first metatarsophalangeal joint. During walking, the delayed group was more inverted at heel strike and had a greater magnitude of rearfoot eversion. Conclusions. Two distinct subpopulations of individuals can be identified by when the windlass mechanism is initiated relative to passive first metatarsalphalangeal extension.

IMPLICATIONS OF GILL ARCH MOVEMENTS FOR FILTER-FEEDING: AN X-RAY CINEMATOGRAPHICAL STUDY OF FILTER-FEEDING WHITE BREAM (BLICCA BJOERKNA) AND COMMON BREAM (ABRAMIS BRAMA)

Previous research shows that the reducible-channel model of filter-feeding can probably be applied to common bream, but not to white bream. According to this model, zooplankton are retained in the channels between the medial gill rakers; the mesh size of the sieve can be reduced by lowering the lateral rakers of the neighbouring gill arch into these channels. Gill arch movements may well disturb this mechanism; the depressed lateral gill rakers will move in and out of the medial channels and also shift out of their centre. We have quantified these disturbances by measuring the gill arch movements during filter-feeding in white bream and common bream, using dorsal X-ray films. In both species, the lateral rakers are long enough to bridge the gill slits. It was expected that common bream, which can reduce their channels, would have considerably less shift out of the channel centre than white bream, which cannot reduce their channels. However, the predicted shift is 40­50 % of the channel width in white bream and 75 % in common bream. A new, dynamic retention mechanism is proposed for common bream. According to this hypothesis, once a particle is trapped in a reduced channel, the channel walls release mucus and the particle becomes sticky. Hence, particles need to be retained mechanically only during part of the gulping cycle. According to the hypothesis, this is achieved by sideways rotation of the lateral rakers in combination with their tapering shape. Retention mechanisms with interdigitating rakers are expected chiefly in facultative filter-feeders, because such mechanisms are easily disturbed by gill arch movements.

Origin of arches in the northwestern Gulf of Mexico basin

The San Marcos and Sabine arches are prominent north-to northwest-trending basement uplifts in the northwestern Gulf of Mexico basin that may be late Mesozoic to Cenozoic foreland or intraplate folds rather than domes over plutons or buoyant basement blocks. These arches are subparallel to and contemporaneous with orogenic episodes in the northwest-trending fold-thrust belt of Mexico. Arch movement was also contemporaneous with rapid convergence between the North American and Pacific plates. Arch development in the gulf as a result of tectonic compression is plausible in view of increasing recognition of wide zones of foreland and intraplate deformation in continents. Current tectonic models of the development of the gulf inaccurately predict gradual, decelerating subsidence when these arches were most active.

X‐ray measurements of gill‐arch movements in filter‐feeding bream, Abramis brama (Cyprinidae)

The technique of X‐ray cinematography was used to study pharyngeal movements in Abramis brama (L.). The theoretical and practical problems in X‐ray cinematography of feeding fish are discussed, as well as criteria for the selection of images suited for detailed measurements.Respiration and filter‐feeding on Daphnia pulex (length c. 1 mm) show different gill arch movement patterns in bream. Slits between gill‐arches are kept smaller during filter‐feeding. In addition, during filter‐feeding, this inter‐arch distance decreases considerably in a posterior direction. The hypothesis that particle retention occurs on the slits formed between adjacent gillarches and their gill‐rakers is not supported by the present results.

Gill arch movements and the function of the dorsal gill arch muscles in the carp

The activity coordination of the dorsal gill arch muscles in a teleost, the carp, is described and the effect of their contraction in combination with the respiratory pump movements is analysed. Based on their origin and insertion the dorsal branchial arch muscles can be divided into three groups: the expternal branchial arch levators, connecting the branchial arches to the neurocranium, the internal branchial arch levators, connecting the pharyngobranchials to the neurocranium and the dorsal oblique muscles, interconnecting the branchial arches and pharyngobranchials. Functionally, however, there are only two categories with the following properties. The first, which consists of the external branchial arch levators alone, is active during every respiratory cycle, including the cough. These muscles expand the branchial basket through gill arch abduction and, in combination with hyomandibular pumping movements, lower the floor of the buccal cavity. The results of these combined movements are: 1. (a) The gill arches remain evenly distributed within the expanding branchial cavities during inspiration, so that continuity of the gill curtain is maintained. Water flow resistance is reduced also. 2. (b) The volume of water flowing into the buccal cavity during inspiration is increased. The second category, comprising the internal branchial arch levators and the dorsal oblique muscles, contracts only during the cough and else is completely inactive. Contraction of these muscles reinforces the dorsal suspension of the gill arches by firmly anchoring the pharyngobranchials and epibranchials to the base of the skull. In this way strong, caudally directed forces which develop during the intermediate expansion of the cough can be prevented from dislocating the branchial basket.

The principles and art of retention

The principles and art of retention