The Foot and Ankle of Australopithecus sediba Zipfel, Bernhard; DeSilva, Jeremy M.; Kidd, Robert S. ...
Science (American Association for the Advancement of Science),
09/2011, Letnik:
333, Številka:
6048
Journal Article
Recenzirano
Odprti dostop
A well-preserved and articulated partial foot and ankle of Australopithecus sediba, including an associated complete adult distal tibia, talus, and calcaneus, have been discovered at the Malapa site, ...South Africa, and reported in direct association with the female paratype Malapa Hominin 2. These fossils reveal a mosaic of primitive and derived features that are distinct from those seen in other hominins. The ankle (talocrural) joint is mostly humanlike in form and inferred function, and there is some evidence for a humanlike arch and Achilles tendon. However, Au. sediba is apelike in possessing a more gracile calcaneal body and a more robust medial malleolus than expected. These observations suggest, if present models of foot function are correct, that Au. sediba may have practiced a unique form of bipedalism and some degree of arboreality. Given the combination of features in the Au. sediba foot, as well as comparisons between Au. sediba and older hominins, homoplasy is implied in the acquisition of bipedal adaptations in the hominin foot.
The brainstem has an ectodermal origin and is composed of 4 parts: the diencephalon, mesencephalon, pons, and medulla oblongata. It serves as the connection between the cerebral hemispheres with the ...medulla and the cerebellum and is responsible for basic vital functions, such as breathing, heartbeat blood pressure, control of consciousness, and sleep. The brainstem contains both white and gray matter. The gray matter of the brainstem (neuronal cell bodies) is found in clumps and clusters throughout the brainstem to form the cranial nerve nuclei, the reticular formation, and pontine nuclei. The white matter consists of fiber tracts (axons of neuronal cells) passing down from the cerebral cortex—important for voluntary motor function—and up from peripheral nerves and the spinal cord—where somatosensory pathways travel—to the highest parts of the brain. The internal structure of brainstem, although complex, presents a systematical arrangement and is organized in 3 laminae (tectum, tegmentum, and basis), which extend its entire length. The motor pathway runs down through the basis, which is located at the most anterior part. The cranial nerve nuclei are settled into the middle layer (the tegmentum), just in front of the 4th ventricle and are placed, from medial to lateral, on the basis of their function: somatic motor, visceral motor, visceral sensory, and somatic sensory. All the somatosensory tracts run upward to the thalamus crossing the tegmentum in front of the cranial nerve nuclei. The tectum, formed by the quadrigeminal plate and the medullary velum, contains no cranial nuclei, no tracts and no reticular formation. The knowledge of precise anatomical localization of a lesion affecting the brainstem is crucial in neurological diagnosis and, on this basis, is essential to be familiar with the location of the mayor tracts and nuclei appropriately. Nowadays, current magnetic resonance imaging techniques, although still macroscopic, allow the fine internal structure of the brainstem to be viewed directly and make it possible to locate the main intrinsic structures that justify the symptoms of the patient. In this article we discuss the anatomy of the brainstem and highlight the features and landmarks that are important in interpreting magnetic resonance imaging.
Front cover:Cover image: Behold beyond barriers: Deciphering the incredible vision of Mantis shrimp. See Bhattacharjee and colleagues, ‘On the importance of integrating comparative anatomy and One ...Health perspectives in anatomy education’, this issue.
ABSTRACT
The origin and evolution of the vertebrate skull have been topics of intense study for more than two centuries. Whereas early theories of skull origin, such as the influential vertebral ...theory, have been largely refuted with respect to the anterior (pre‐otic) region of the skull, the posterior (post‐otic) region is known to be derived from the anteriormost paraxial segments, i.e. the somites. Here we review the morphology and development of the occiput in both living and extinct tetrapods, taking into account revised knowledge of skull development by augmenting historical accounts with recent data. When occipital composition is evaluated relative to its position along the neural axis, and specifically to the hypoglossal nerve complex, much of the apparent interspecific variation in the location of the skull–neck boundary stabilizes in a phylogenetically informative way. Based on this criterion, three distinct conditions are identified in (i) frogs, (ii) salamanders and caecilians, and (iii) amniotes. The position of the posteriormost occipital segment relative to the hypoglossal nerve is key to understanding the evolution of the posterior limit of the skull. By using cranial foramina as osteological proxies of the hypoglossal nerve, a survey of fossil taxa reveals the amniote condition to be present at the base of Tetrapoda. This result challenges traditional theories of cranial evolution, which posit translocation of the occiput to a more posterior location in amniotes relative to lissamphibians (frogs, salamanders, caecilians), and instead supports the largely overlooked hypothesis that the reduced occiput in lissamphibians is secondarily derived. Recent advances in our understanding of the genetic basis of axial patterning and its regulation in amniotes support the hypothesis that the lissamphibian occipital form may have arisen as the product of a homeotic shift in segment fate from an amniote‐like condition.
•Fresh organ dissection in young mice gives better results than fixing whole carcass.•Modified Davidson’s better than formalin or Bouin’s in fixation of juvenile brain.•The sequence of events during ...organ development is very similar in mice and rats.•Developmental milestones often achieved earlier in the mouse than in the rat.
There is a growing demand for wild type mice and mouse models of disease that may be more representative of human conditions but there is little information on neonatal and juvenile mouse anatomy. This project produces sound and comprehensive histology background data on the developing neonatal mouse at different time points from Day 0 until Day 28.
The work describes optimal methods for tissue harvesting, fixation and processing from the neonatal and juvenile mice which can be used in routine toxicology studies.
A review of the available literature revealed inconsistencies in the developmental milestones reported in the mouse. Although it is true that the sequence of events during the development is virtually the same in mice and rats, important developmental milestones in the mouse often happen earlier than in the rat, and these species should not be used interchangeably.
ABSTRACT Background Understanding the neural mechanisms of psychiatric disorders requires the use of rodent models; however, frontal-striatal homologies between rodents and primates are unclear. In ...contrast, within the striatum, the shell of the nucleus accumbens, the hippocampal projection zone, and the amygdala projection zone (referred to as the striatal emotion processing network EPN) are conserved across species. We used the relationship between the EPN and projections from the anterior cingulate cortex (ACC) and orbitofrontal cortex (OFC) to assess network similarities across rats and monkeys. Methods We first compared the location and extent of each major component of the EPN in rats and macaques. Next, we used anatomic cases with anterograde injections in ACC/OFC to determine the extent to which corticostriatal terminal fields overlapped with these components and with each other. Results The location and size of each component of the EPN were similar across species, containing projections primarily from infralimbic cortex in rats and area 25 in monkeys. Other ACC/OFC terminals overlapped extensively with infralimbic cortex/area 25 projections, supporting cross-species similarities in OFC topography. However, dorsal ACC had different connectivity profiles across species. These results were used to segment the monkey and rat striata according to ACC/OFC inputs. Conclusions Based on connectivity with the EPN, and consistent with prior literature, the infralimbic cortex and area 25 are likely homologues. We also see evidence of OFC homologies. Along with segmenting the striatum and identifying striatal hubs of overlapping inputs, these results help to translate findings between rodent models and human pathology.
The hand of Homo naledi Kivell, Tracy L; Deane, Andrew S; Tocheri, Matthew W ...
Nature communications,
10/2015, Letnik:
6, Številka:
1
Journal Article
Recenzirano
Odprti dostop
A nearly complete right hand of an adult hominin was recovered from the Rising Star cave system, South Africa. Based on associated hominin material, the bones of this hand are attributed to Homo ...naledi. This hand reveals a long, robust thumb and derived wrist morphology that is shared with Neandertals and modern humans, and considered adaptive for intensified manual manipulation. However, the finger bones are longer and more curved than in most australopiths, indicating frequent use of the hand during life for strong grasping during locomotor climbing and suspension. These markedly curved digits in combination with an otherwise human-like wrist and palm indicate a significant degree of climbing, despite the derived nature of many aspects of the hand and other regions of the postcranial skeleton in H. naledi.
Koalas are characterised by a highly unusual vocal anatomy, with a descended larynx and velar vocal folds, allowing them to produce calls at disproportionately low frequencies. Here we use advanced ...imaging techniques, histological data, classical macroscopic dissection and behavioural observations to provide the first detailed description and interpretation of male and female koala vocal anatomy. We show that both males and females have an elongated pharynx and soft palate, resulting in a permanently descended larynx. In addition, the hyoid apparatus has a human‐like configuration in which paired dorsal, resilient ligaments suspend the hyoid apparatus from the skull, while the ventral parts tightly connect to the descended larynx. We also show that koalas can retract the larynx down into the thoracic inlet, facilitated by a dramatic evolutionary transformation of the ventral neck muscles. First, the usual retractors of the larynx and the hyoid have their origins deep in the thorax. Secondly, three hyoid muscles have lost their connection to the hyoid skeleton. Thirdly, the genioglossus and geniohyoid muscles are greatly increased in length. Finally, the digastric, omohyoid and sternohyoid muscles, connected by a common tendinous intersection, form a guiding channel for the dynamic down‐and‐up movements of the ventral hyoid parts and the larynx. We suggest that these features evolved to accommodate the low resting position of the larynx and assist in its retraction during call production. We also confirm that the edges of the intra‐pharyngeal ostium have specialised to form the novel, extra‐laryngeal velar vocal folds, which are much larger than the true intra‐laryngeal vocal folds in both sexes, but more developed and specialised for low frequency sound production in males than in females. Our findings illustrate that strong selection pressures on acoustic signalling not only lead to the specialisation of existing vocal organs but can also result in the evolution of novel vocal structures in both sexes.
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