M. Ashraf Aziz

The Human Cadaver in the Age of Biomedical Informatics

Major national and international critiques of the medical curriculum in the 1980s noted the following significant flaws: (1) over‐reliance on learning by rote memory, (2) insufficient exercise in analysis and synthesis/conceptualization, and (3) failure to connect the basic and clinical aspects of training. It was argued that the invention of computers and related imaging techniques called to question the traditional instruction based on the faculty‐centered didactic lecture. In the ensuing reform, which adopted case‐based, small group, problem‐based learning, time allotted to anatomical instruction was severely truncated. Many programs replaced dissection with prosections and computer‐based learning. We argue that cadaver dissection is still necessary for (1) establishing the primacy of the patient, (2) apprehension of the multidimensional body, (3) touch‐mediated perception of the cadaver/patient, (4) anatomical variability, (5) learning the basic language of medicine, (6) competence in diagnostic imaging, (7) cadaver/patient‐centered computer‐assisted learning, (8) peer group learning, (9) training for the medical specialties. Cadaver‐based anatomical education is a prerequisite of optimal training for the use of biomedical informatics. When connected to dissection, medical informatics can expedite and enhance preparation for a patient‐based medical profession. Actual dissection is equally necessary for acquisition of scientific skills and for a communicative, moral, ethical, and humanistic approach to patient care. Anat Rec (New Anat) 269:20–32, 2002.

Comparative anatomical study of the forearm extensor muscles of Cebus libidinosus (Rylands et al., 2000; Primates, Cebidae), modern humans, and other primates, with comments on primate evolution, phylogeny, and manipulatory behavior.

Despite its abundance in Latin America, and its remarkable ability to use tools, there are only a few myological studies on the capuchin monkey, Cebus libidinosus. In the present study, we dissected the forearm extensor muscles of six adult males and two adult females of this species. We describe these muscles and compare them with those of other primates dissected by us and by other authors. The forearm extensor muscles of Cebus monkeys are, in general, more similar to those of other platyrrhines than to distantly related taxa that use tools, such as chimpanzees and modern humans, with three main exceptions: contrary to most other platyrrhines, (1) in Cebus, chimpanzees and modern humans the extensor pollicis longus usually inserts onto Digit I, and not onto Digits I and II; (2) in Cebus the abductor pollicis longus has two separate tendons, as is the case in chimpanzees, and in modern humans (where one of these tendons is associated with a distinct belly, forming the muscle extensor pollicis brevis); (3) in Cebus, and in modern humans and chimpanzees, the extensor pollicis longus is not deeply blended with the extensor indicis. Therefore, the Cebus monkeys provide an illustrative example of how phylogenetic constrains and ecological adaptations have been combined to develop a specific myological configuration that, associated with their sophisticated neurological organization, allow them to easily navigate in their arboreal habitats and, at the same time, to finely manipulate objects in order to search for food and to prepare this food for ingestion. Anat Rec, 2010.

The human extensor digitorum profundus muscle with comments on the evolution of the primate hand

Forelimb dissections on 14 genera of anthropoids including humans and 17 cases of human aneuploids has revealed a high incidence of “atavistic” musculature (Barash et al., 1970;Aziz, 1981a) in the aneuploids. The phenotypic specificity of this aneuploid musculature clearly manifests developmental retardation and instability (Shapiro, 1983) revealing not only the likely course of embryonic myogenesis in chromosomally normal humans (Cihak, 1972, 1977) but also information relevant to ontogenetic and evolutionary changes. The extensor digitorum profundus proprius complex is particularly illustrative of these characteristics of aneuploid musculature. Our examination of the variation of this muscle complex in human aneuploids and between primate genera reveals how normal ontogeny may proceed, as well as the morphological basis for the evolutionary changes in hand structure and function amongst Primates. We also consider the phylogenetic and functional significance of changes in the extensor digitorum profundus proprius with reference to the divergent locomotory and manipulative capabilities and behavior of Primates.

“Pollical palmar interosseous muscle” (musculus adductor pollicis accessorius): Attachments, innervation, variations, phylogeny, and implications for human evolution and medicine

Most atlases and textbooks dealing with human anatomy do not refer to the “pollical palmar interosseous” (PPI) muscle of Henle. In order to undertake a fresh and detailed study of this muscle and to thus better understand human comparative anatomy and evolution, we: 1) analyze the frequency of the PPI in a large sample of human hands; 2) describe the attachments, innervation and varieties of the PPI in these hands; 3) compare the data obtained with the information available in the literature; and 4) discuss the phylogenetic origin of the PPI and the implications of our observations and comparisons for medicine and for the understanding of human evolutionary history. Within the 72 hands dissected by us, the PPI is present in 67 hands (93%), commonly having a single muscular branch, originating from the medial side of the base of metacarpal I only, inserting onto the medial side of the base of the pollical proximal phalanx and/or surrounding structures (e.g., ulnar sesamoid bone, wing tendon of extensor apparatus), and passing at least partially, and usually mainly, medial to the princeps pollicis artery. A careful study of the human PPI, as well as a detailed comparison with other mammals, strongly suggest that the muscle is evolutionarily derived from the adductor pollicis, and namely from its oblique head. Therefore, we propose that PPI should be designated by the name musculus adductor pollicis accessorius, which indicates that the muscle is most likely a de novo structure derived from the adductor pollicis. J. Morphol., 2013.

Muscular anomalies caused by delayed development in human aneuploidy

Comprehensive dissections of three infants with trisomy‐13 and three with trisomy‐18 have revealed several muscles which appear to be “abnormal” at the time of birth and shortly thereafter. Careful observations show that the peculiar morphology of these muscles results from delayed development rather than from anatomical malformation. The observations are compared with physiological, pathological and in vitro experimental studies of delayed embryonic development in human aneuploidy.

Anatomical variations of the deep head of Cruveilhier of the flexor pollicis brevis and its significance for the evolution of the precision grip

Cruveilhier described in 1834 the human flexor pollicis brevis (FPB), a muscle of the thenar compartment, as having a superficial and a deep head, respectively, inserted onto the radial and ulnar sesamoids of the thumb. Since then, Cruveilhier’s deep head has been controversially discussed. Often this deep head is confused with Henle’s “interosseous palmaris volaris” or said to be a slip of the oblique adductor pollicis. In the 1960s, Day and Napier described anatomical variations of the insertions of Cruveilhier’s deep head, including its absence, and hypothesized, that the shift of the deep head’s insertion from ulnar to radial facilitated “true opposability” in anthropoids. Their general thesis for muscular arrangements underlying the power and precision grip is sound, but they did not delineate their deep head from Henle’s muscle or the adductor pollicis, and their description of the attachments of Cruveilhier’s deep head were too vague and not supported by a significant portion of the anatomical literature. Here, we reinvestigated Cruveilhier’s deep head to resolve the controversy about it and because many newer anatomy textbooks do not describe this muscle, while it is often an obvious functionally (writing, texting, precision grip) and clinically significant thenar muscle. For the first time, we empirically delineated Cruveilhier’s deep head from neighboring muscles with which it was previously confused. We observed 100% occurrence of the uncontested deep head in 80 human hands, displaying a similar variability of insertions as Day and Napier, but in significantly different numbers. Furthermore, we found variability in the origin and included as important landmarks the trapezoid and the ligamentum carpi radiatum. We tested the assertion regarding the evolutionary morphology and its role in the improvements in thumb movements during various precision grips. Our overall conclusions differ with respect to the developmental and evolutionary origin of the FPB heads.

En Bloc Removal of the Mandible, the Masticatory Muscles and the Mandibular Nerve in the Chimpanzee (Pan troglodytes, Blumenbach 1799), with a Review and Critique of the Methods Used to Expose the Trigeminal Musculature in Derived Primates

The detailed protocol of the en bloc removal of the mandible, the muscles supplied by the mandibular nerve tree and the maxillary artery is described in the chimpanzee (Pan troglodytes). This new method allows integrated observations of the masticatory muscles, their ontogenetic associates and the specific branches of the mandibular nerve that supply them. The topographic relationships of the muscles, including their subparts, are seen in light of the specific nerve branches that supply and interconnect them. Previous methods that examine parts of the trigeminal musculature and the mandibular nerve in a fragmented manner are described and critiqued. The present method allows us to arrive at a sounder classification of the trigeminal muscles based on the integrated observation of their nerve supply; this approach was first proposed by Toldt and more recently used by Tomo. The anatomical, functional, clinical, ontogenetic and phylogenetic aspects of the new approach are discussed.