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Biomedical subjects

M R Kean

Publications and source records attributed to M R Kean.

10 recordsLinked to original sources
PubMed1990

Polynesian face and dentition: functional perspective.

Widely dispersed throughout the Pacific, Polynesians are a biologically distinctive people in form and size of both body and head. Large-bodied and well-muscled, their body phenotype is suited to life in a thermolabile oceanic environment. Their craniofacial skeleton is large and robust, with mandibular size and form (the "rocker" mandible) being especially characteristic. In this paper the Polynesian variants of body form, and of facial size (including dentition) and form, are interpreted from a functional perspective.

Anthropometry↗
PubMed1989

Ultrasonic investigation of the circumoral musculature.

Real-time ultrasound with a high frequency probe is used to image the circumoral musculature with the lips relaxed and contracted. The ultrasonic images show that muscle tissue makes up only a part of the total thickness of the lip, and varies among individuals in shape, transonicity (clearness) and thickness. The muscle layer in the upper lip is sandwiched between layers of facial and lingual connective tissue, while the muscle image in the lower lip lies close to the lingual surface. In a relaxed state the muscle layer in the lower lip is significantly thicker than that in the upper lip, and a mean difference also occurs in contraction, but to a considerably lesser degree. Thus the upper lip muscle appears to increase in thickness during contraction relatively more than does that of the lower lip. Furthermore, the contraction in the upper lip seems to occur fairly uniformly along the lip from left to right. The muscular changes in the lower lip are more complex, even though embryologically complexity is ascribed properly to the upper lip. In the lower lip contraction seems to occur in the lateral parts and in the mentalis muscle, but in the midline the orbicularis oris muscle remains quite inactive. More complex arrangements are essential merely to ensure support of the lower lip against gravity.

Adult↗
PubMed1987

The role of function in the development of human craniofacial form--a perspective.

As an anatomical region the head combines great diversity of function with close integration of structure. Consequently no structural component has autonomy of form. There is a sequence of maturation of functions and their related structural components, and in this sequence the nervous system and its supportive structures mature first. The nasal airway matures next in response to increasing body mass, and the masticatory system constitutes the last major functional system to reach maturity. The later the maturation of the function, the greater is the requirement for its related morphology to adapt to preceding skeletal templates. These matters of developmental sequence, and extrinsic as well as intrinsic craniofacial functions, are paramount considerations in interpreting the form of any component of head anatomy.

Face↗
PubMed1982

The Polynesian head: growth and form.

We consider the cranial base to be the primordial determinant of the head form and mandibular shape so common amongst (but not exclusive to) adult Polynesians. The flatness of the cranial base manifests its full influence only when growth of the upper facial skeleton is complete in early adulthood. We argue that during growth and maturation the upper facial skeleton and the maxillary occlusal plane are required to adjust in position to a major extent according to the template set out by the flat cranial base, with consequent obligatory and extreme adjustment in shape and position of the mandible in order that occlusion be maintained. The base is constrained from adjusting its own shape significantly by virtue of its intimate relationship with the brain and the emerging cranial nerves. The structural consequences of these adaptations are seen in the bony profile, which is vertically disposed and orthognathic, and in the large nasopharynx, while functionally the relative inefficiency of the mandible as a lever requires extensive compensatory development of masticatory musculature which influences the shape of the face and vault.

Adolescent↗