SEARCH · Search PubMed
Results for “Beak”
Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
[Beak fracture of the calcaneus].
Explore the source record for details and available documents.
[Rete mirabile of the intestine in beaked whales, Ziphidae (Cetacea)].
Explore the source record for details and available documents.
"Beak" triple arthrodesis for correction of severe cavus deformity.
Explore the source record for details and available documents.
[Perforating wound of the eye by owl's beak].
Explore the source record for details and available documents.
New syndrome associated with partial deletion of short arms of chromosome No. 4. Clinical manifestations of hypospadias, beaked nose, abnormal iris, hemangioma of forehead, seizures, and other anomalies.
Explore the source record for details and available documents.
[Flute-beak tracheal stenosis (apropos of 6 cases)].
Explore the source record for details and available documents.
[Diagnosis of the beaked pelvis].
Explore the source record for details and available documents.
The open beak extraction technique.
Explore the source record for details and available documents.
Prevention of parrot's beak deformity after reduction rhinoplasty.
Explore the source record for details and available documents.
Functional morphology of the cephalopod buccal mass: a novel joint type.
The arrangement of the musculature and connective tissues of the buccal mass of the coleoid cephalopods Octopus bimaculoides, Sepia officinalis, and Loliguncula brevis was examined using dissection and histology. Serial sections in three mutually perpendicular planes were used to identify the muscles and connective tissues responsible for beak movements and stability and to describe their morphology and fiber trajectories. Four major beak muscles were identified: the anterior, posterior, superior, and lateral mandibular muscles. The anterior, posterior, and superior mandibular muscles connect the upper beak and the lower beak. Although the lateral mandibular muscles originate on the upper beak, they do not connect to the lower beak and instead insert on a connective tissue sheath surrounding the buccal mass. Examination of the fibers of the lateral mandibular muscles reveals that they have the organization of a muscular hydrostat, with muscle fibers oriented in three mutually perpendicular orientations. Although the beaks are capable of complex opening, closing, and shearing movements, they do not contact one another and are instead connected only by the musculature of the buccal mass. Based on the morphological analysis and observations of freshly dissected beaks undergoing the stereotyped bite cycle, the functional role of the beak muscles is hypothesized. The anterior and superior mandibular muscles are likely responsible for beak closing and shearing movements. The posterior mandibular muscle is likely also involved in beak closing, but may act synergistically with the lateral mandibular muscles to open the beaks. The lateral mandibular muscles may use a muscular-hydrostatic mechanism to control the location of the pivot between the beaks and to generate the force required for beak opening. The lack of contact between the beaks and the morphology of the lateral mandibular muscles suggests that the buccal mass of coleoid cephalopods may represent a previously unexamined flexible joint mechanism. The term "muscle articulation" is proposed here to denote the importance of the musculature in the function of such a joint.
Mouth breathing in chickens under rebreathing conditions, cervical vagotomy of heat load.
By recording the lower beak movement, open-mouth breathing was monitored in adult hens restrained in a supine position with the cannulated trachea under rebreathing conditions, bilateral cervical vagotomy or heat load. Tidal volume and respiratory carbon-dioxide and oxygen contents were recorded simultaneously. The beak movement can be a significant indication of hypercapnia and/or increase in respiratory CO2 content, but not of hypoxia or decrease in respiratory O2 content. Vagotomy causes big oscillatory movements of the beak, which do not mainly depend on hypercapnic hypoxia induced by the vagotomy. If the dysfunction of the vagus is aggravated progressively, it will be unable for the pattern and amplitude of beak movement to be any differential indication of this dysfunction from hypercapnia and/or increase in respiratory CO2 content seen at respiratory failure. Two patterns of beak movement are noticed. One appears at an early stage of beak movement and at a certain direct level superimposed with or without small beak-oscillation. The other indicates a bigger oscillatory beak movement than the former. This oscillatory movement is synchronous with the inspiration after vagotomy and hypercapnia. This is the case with hyperthermia at a remarkably high breathing frequency. The amplitude of beak movement is not always proportional to the tidal volume. The onset and end of inspiration cannot precisely be indicated by those of a beak movement.
Quantitative analysis of the effect of retinoids on facial morphogenesis.
Retinoids have been applied to stage 20 chick embryos by using beads that act as controlled release carriers. With beads soaked in high concentrations of all-trans-retinoic acid, the face, in addition to the wing, is affected. Severe bilateral clefting of the primary palate results; the upper beak is completely missing, whereas the lower beak is unaffected. By using a scoring system that quantitates the severity of the upper beak defect, dose-response curves have been obtained. With beads soaked in progressively higher concentrations of retinoic acid, the upper beaks are increasingly truncated. The synthetic retinoid TTNPB also causes beak defects and is 30 times more potent than all-trans-retinoic acid. By removing beads soaked in retinoids at different times after implantation, the effect of varying the length of exposure of the developing face to retinoids has been examined. The production of beak defects is a two-step process and only a short exposure to retinoid is required to produce clefting. There are striking similarities in the dose-time relationships of retinoid treatments that are required to bring about beak defects and pattern changes in the limb. The outgrowth and development of spatially defined patterns of connective tissue within the upper beak appear analogous to processes involved in limb morphogenesis. We propose that retinoids may act by the same mechanisms in both systems. An unsolved puzzle is why retinoids specifically affect the development of the upper beak.
Kinematics of birdsong: functional correlation of cranial movements and acoustic features in sparrows.
The movements of the head and beak of songbirds may play a functional role in vocal production by influencing the acoustic properties of songs. We investigated this possibility by synchronously measuring the acoustic frequency and amplitude and the kinematics (beak gape and head angle) of singing behavior in the white-throated sparrow (Zonotrichia albicollis) and the swamp sparrow (Melospiza georgiana). These birds are closely related emberizine sparrows, but their songs differ radically in frequency and amplitude structure. We found that the acoustic frequencies of notes in a song have a consistent, positive correlation with beak gape in both species. Beak gape increased significantly with increasing frequency during the first two notes in Z. albicollis song, with a mean frequency for note 1 of 3 kHz corresponding to a gape of 0.4 cm (a 15 degrees gape angle) and a mean frequency for note 2 of 4 kHz corresponding to a gape of 0.7 cm (a 30 degrees gape angle). The relationship between gape and frequency for the upswept third note in Z. albicollis also was significant. In M. georgiana, low frequencies of 3 kHz corresponding to beak gapes of 0.2-0.3 cm (a 10-15 degrees break angle), whereas frequencies of 7-8 kHz were associated with flaring of the beak to over 1 cm (a beak angle greater than 50 degrees). Beak gape and song amplitude are poorly correlated in both species. We conclude that cranial kinematics, particularly beak movements, influence the resonance properties of the vocal tract by varying its physical dimensions and thus play an active role in the production of birdsong.
Mouth lesions in broiler chickens caused by scirpenol mycotoxins.
Dietary scirpentriol (STO), triacetoxyscirpenol (TAS), monoacetoxyscirpenol (MAS), and diacetoxyscirpenol (DAS), mycotoxins produced by Fusarium species, were compared for their ability to cause mouth lesions when graded dietary levels (0, 1, 2, 4, and 8 micrograms STO or TAS/g; 0, .5, 1, 2, and 4 micrograms MAS or DAS/g) were fed to male broiler chickens for 21 days after hatching. The mouth lesions provoked by each scirpenol were dose-related. The minimum effective doses (MED) were 4, 2, 1, and .5 micrograms/g for TAS, STO, DAS, and MAS, respectively, whether the number of affected birds or the number of affected mouth parts (angles, upper beak, lower beak, and tongue) was the measured response. Lesion sites in the mouth varied with the toxin. The rank orders from greatest to least affected sites were angles, upper beak, lower beak, and tongue for TAS and STO, upper beak, lower beak, angles, and tongue for MAS, and upper beak, lower beak, tongue, and angles for DAS. Mouth lesions were clearly visible with each toxin after feeding for 1 wk and the numbers of affected mouth parts almost tripled after 2 wk exposure. During Week 3 of exposure, only the increase caused by MAS was significant (P less than .05). The MED for growth inhibition were 2, 2, 2, and 8 micrograms/g for STO, MAS, DAS, and TAS, respectively. Thus, mouth lesions were of equal or greater sensitivity than growth inhibition as an indicator of scirpenol toxicity. It would appear that the discovery of mouth lesions in birds justifies a mold and mycotoxin control program.
Vocal tract filtering and sound radiation in a songbird.
Bird vocalizations resonate as they propagate through a relatively long trachea and radiate out from the oral cavity. Several studies have described the dynamics with which birds actively vary beak gape while singing and it has been hypothesized that birds vary beak gape as a mechanism for varying vocal tract resonances. Nevertheless, few studies have attempted to quantify the effects of beak gape on vocal tract resonances. We replaced eastern towhee, Pipilo erythrophthalmus L., syringes with a small speaker and obtained recordings of frequency sweeps while rotating each subject in a horizontal plane aligned with either the maxilla or mandible. We describe vocal tract resonances as well as how sound radiates as a function of beak gape. Results are inconsistent with the hypothesis that songbirds vary beak gape as a mechanism for 'tracking' fundamental frequencies in vocalizations. Instead, decreases in beak gape seem to attenuate resonances that occur between approximately 4 and 7.5 kHz. We propose that songbirds vary beak gape as a mechanism for excluding and/or concentrating energy within at least two distinct sound frequency channels.
The role of cranial kinesis in birds.
In birds, the ability to move the upper beak relative to the braincase has been the subject of many functional morphological investigations, but in many instances the adaptive significance of cranial kinesis remains unclear. Alternatively, cranial kinesis may be considered a consequence of the general design of the skull, rather than an adaptive trait as such. The present study reviews some results related to the mechanism and functional significance of cranial kinesis in birds. Quantitative three-dimensional X-ray has shown that in skulls morphologically as divers as paleognaths and neognaths the mechanism for elevation of the upper beak is very similar. One of the mechanisms proposed for avian jaw movement is a mechanical coupling of the upper and the lower jaw movement by the postorbital ligament. Such a mechanical coupling would necessitate upper beak elevation. However, independent control of upper and lower jaw has been shown to occur during beak movements in birds. Moreover, kinematic modeling and force measurements suggests that the maximum extensibility of collagen, in combination with the short distance of the insertion of the postorbital ligament to the quadrato-mandibular articulation do not constitute a block to lower jaw depression. The lower jaw ligaments serve to limit the maximal extension of the mandibula. It is suggested here that cranial kinesis in avian feeding may have evolved as a consequence of an increase in eye size. This increase in size led to a reduction of bony bars in the lateral aspect of the skull enabling the transfer of quadrate movement to the upper jaw. The selective forces favoring the development of a kinetic upper beak in birds may be subtle and act in different ecological contexts. Simultaneous movement of the upper and lower jaw not only increases the velocity of beak movements, but with elevated upper beak also less force is required to open the lower jaw. However, the penalty of increased mobility of elements in a lightweight skull and a large eye is potential instability of skull elements during biting, smaller bite forces and limitations on joint reaction forces. Such a lightly built, kinetic skull may have evolved in animals that feed on small plant material or insects. This type of food does not require the resistance of large external forces on the jaws as in carnivores eating large prey.
Patterns of respiration in diving penguins: is the last gasp an inspired tactic?
Humboldt penguins Spheniscus humboldti in captivity and free-living Magellanic penguins S. magellanicus were fitted with loggers to determine beak angles during breathing. The Humboldt penguins were also fitted with masks for determining rates of air flow during breathing. During periods of higher gas exchange requirement, Humboldt penguins opened their beaks during inspiration, where tidal volume was linearly correlated with both change in beak angle and maximum beak angle, closed them slightly during the final stages of inspiration and finally closed them during expiration. Substantial differences were apparent between individuals. Contrary to the condition proposed for most birds, our data suggest that expiration is passive during periods of high respiratory tidal volumes, and that the increased resistance of the respiratory pathway serves to slow air flow so as to maximize gas exchange in the lungs. During foraging, Magellanic penguins at the surface between dives showed similar breathing patterns but maximum beak angles were much higher and breath cycle time shorter, as would be expected for animals attempting to maximize gas exchange. Both maximum beak angle per breath and breath frequency changed systematically over the surface pause; both were initially high, then decreased to a low before rising again to a maximum just before diving. Based on known changes in tidal volume with beak angle derived from Humboldt penguins, a simple model is proposed to examine rates of gas exchange over the surface pause. This indicates that the observed patterns do not maximize the rate of transfer of oxygen over the whole of the surface pause but are rather concerned with an initial rapid accumulation of oxygen in the tissues followed by effective carbon dioxide release.