Mara 2008 - PLENARY PAPER

The 'Sable Systems' - MARA 2008
PLENARY SPEAKER
J.N. Maina
BVM, PhD, DVSc
Professor and Head School of the School of Anatomical Sciences, University of Witwatersrand, Johannesburg, South Africa.

Brief Curriculum Vitae - J.N. Maina, BVM, PhD, DVSc

Trained as a veterinary surgeon at the University of Nairobi and did doctoral work at the University of Liverpool. Awarded a DVSc of the University of Liverpool (1999) on thesis entitled “Comparative functional morphology of the gas exchangers”. Taught at the Department of Veterinary Anatomy, University of Nairobi between 1982-1996 before joining the then Department of Human Anatomy and Cell Biology at the University of the Witwatersrand Johannesburg, South Africa as Professor. Presently Professor and Head School of the School of Anatomical Sciences, University of Witwatersrand. Published over 100 research and review papers in international journals and written several books in the area of comparative pulmonary functional morphology. Twice awarded Fulbright Senior Research Fellowships taken at the University of California (Davis), Royal Society Senior Research Fellowship at the University of Liverpool, and nominated a Hooker Distinguished Visiting Professor at McMaster University. Has been appointed Visiting Professor/Senior Research Fellow at the University of California (San Diego and Davis), University of Liverpool, University of Wyoming, and University of Tokyo (not taken).

Perspectives on the comparative functional morphologies of the gas exchangers

John N. Maina
School of Anatomical Sciences, University of the Witwatersrand,
7 York Road, Parktown 2193, Johannesburg, South Africa

The acquisition of molecular oxygen from the external environment is the foremost purpose of respiration. Organisms/animals occupy different environments and manifest different metabolic capacities. Gas exchangers are designed to meet particular demands for molecular oxygen. Outcomes of a long evolutionary process, the ultimate designs of the modern gas exchangers have been prescribed by factors such as the respiratory medium utilized, the phylogenetic level of development, body mass, lifestyle, and habitat occupied. Cost-benefit analyses that have entailed trade-offs and compromises have shaped the present forms: ‘user-specific’ gas exchangers have developed. Structural-functional correlations and convergences have occurred between and within taxa. For an inclusive and important process like respiration, whether by default or by design, morphological plasticity is important. It has allowed animals at different phylogenetic levels, i.e., those with different infrastructural resources, to adapt and subsist in same and different habitats. Albeit the many forms that exist, fundamentally, the structure and function of the gas exchangers have been remarkably conserved. There are no tissues or cells that are ubiquitous to the respiratory organs. The plain cell membrane is the most elementary and practical gas exchanger. For gas exchange to occur between physical compartments, all that is necessary is an effectively thin tissue barrier and an adequate partial pressure gradient.
The structural and functional match between the respiratory organs has been compelled by the facts that only two respiratory fluid media, air and water, are utilized and common immutable laws of physics govern the movement of the respiratory gases. These aspects will be discussed from a comparative point of view.

Maina JN (2002). Structure, function and evolution of the gas exchangers: comparative perspectives. J. Anat. 201, 281-304.
Maina JN (2000). Comparative respiratory morphology: themes and principles in the design and construction of the gas exchangers. Anat. Rec.261, 25-44.

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