314 results in Bioengineering
11 - The sub-seafloor biosphere and sulphate-reducing prokaryotes: their presence and significance
- Edited by Larry L. Barton, University of New Mexico, W. Allan Hamilton, University of Aberdeen
-
- Book:
- Sulphate-Reducing Bacteria
- Published online:
- 22 August 2009
- Print publication:
- 31 May 2007, pp 329-358
-
- Chapter
- Export citation
-
Summary
GENERAL INTRODUCTION
Approximately 70% of the Earth's environment is marine, which includes substantial sediment deposits, some of which can be greater than 10 km in depth (Fowler, 1990). Although these sediments contain the largest global organic carbon reservoir (∼15 000 × 1018 g C, Hedges and Keil, 1995), apart from shallow margin sediments (to 200 m water depth), they have been considered to be relatively biogeochemically inactive. For example, Jørgensen (1983) calculated that margin sediments accounted for 83% of global marine sediment oxygen uptake whilst only representing 8.6% of global sediment area. In contrast, deeper sediments (200 to >4000 m water depths), despite being ∼91% of marine sediment area, accounted for only 17% of global oxygen uptake. The situation was considered even more extreme for rates of sulphate reduction, with this being responsible for, respectively, 50% and 0% of all organic matter being degraded in margin and deep water sediments (>4000 m water depths) (Jørgensen, 1983). This low activity was consistent with results demonstrating the limited depth distribution of prokaryotic populations in deep sediments. Morita and ZoBell (1955) concluded that the marine biosphere ended at 7.47 m deep, based on their inability to culture bacteria at this or greater depths. Reports of prokaryotes being isolated from deeper sediments were considered to be contaminants introduced during sampling, or dormant organisms being re-activated (ZoBell, 1938).
7 - Biochemical, genetic and genomic characterization of anaerobic electron transport pathways in sulphate-reducing Delta proteobacteria
- Edited by Larry L. Barton, University of New Mexico, W. Allan Hamilton, University of Aberdeen
-
- Book:
- Sulphate-Reducing Bacteria
- Published online:
- 22 August 2009
- Print publication:
- 31 May 2007, pp 215-240
-
- Chapter
- Export citation
-
Summary
INTRODUCTION
Sulphate-reducing bacteria (SRB) derive energy for growth by coupling the oxidation of hydrogen or organic compounds to the reduction of sulphate to sulphide. The bioenergetics and the global topology of energy-conserving reactions have already been discussed in Chapter 1. Understanding the bioenergetics of the coupling of hydrogen oxidation and sulphate reduction is simple, in principle. Four H2 are oxidized by periplasmic hydrogenases and the eight protons and electrons are transferred to the cytoplasm through ATP synthase and transmembrane-electron-transfer complexes for sulphate reduction. This produces approximately three adenosine triphosphates (ATPs), of which two are needed to activate sulphate. Hence a net yield of one ATP is produced per sulphate reduced. Energy conservation by coupling the reduction of sulphate to the incomplete oxidation of lactate is more complex because the primary oxidation reactions are now also cytoplasmic. Because these yield two ATPs by substrate level phosphorylation, the same number as required for the activation of sulphate, a net energetic benefit can only be obtained by hydrogen cycling as proposed by Odom and Peck (Odom and Peck, 1981), cycling of formate or CO (Heidelberg et al., 2004; Voordouw, 2002) or by electrogenic proton translocation associated with the electron transport chain for reduction of sulphate. The components that participate in these anaerobic electron transport pathways will be considered in detail here. Harry Peck and Jean LeGall, the pioneers of the biochemistry of SRB, contributed greatly by purifying and characterizing many of the redox proteins present in these organisms.
List of Contributors
- Edited by Larry L. Barton, University of New Mexico, W. Allan Hamilton, University of Aberdeen
-
- Book:
- Sulphate-Reducing Bacteria
- Published online:
- 22 August 2009
- Print publication:
- 31 May 2007, pp vii-xvi
-
- Chapter
- Export citation
13 - Bioprocess engineering of sulphate reduction for environmental technology
- Edited by Larry L. Barton, University of New Mexico, W. Allan Hamilton, University of Aberdeen
-
- Book:
- Sulphate-Reducing Bacteria
- Published online:
- 22 August 2009
- Print publication:
- 31 May 2007, pp 383-404
-
- Chapter
- Export citation
-
Summary
INTRODUCTION
The microbiota present in the sulphur cycle have been studied since the end of the nineteenth century when the pioneering work of the famous microbiologists Winogradsky and Beijerinck took place. Sulphur conversions involve the metabolism of several different specific groups of bacteria, e.g. sulphate-reducing bacteria (SRB), phototrophic sulphur bacteria and thiobacilli, specialized to use these sulphur compounds in their different redox states (Lens and Kuenen, 2001). Many of these microorganisms possess unique metabolic and ecophysiological features, and to date there are still regular reports of novel microorganisms with extraordinary properties. Several of the microbial conversions of the sulphur cycle can be implemented for pollution control (Table 13.1). This chapter overviews the applications in environmental technology, which utilize the metabolism of SRB as the key process.
Technological utilization of SRB sounds at first somewhat controversial, as sulphate reduction has been considered unwanted for many years in anaerobic wastewater treatment (Hulshoff Pol et al., 1998). Emphasis of the research in the 1970s–1980s was mainly on the prevention or minimalization of sulphate reduction during methanogenic wastewater treatment (Colleran et al., 1995). From the 1990s onwards, interest has grown in applying sulphate reduction for the treatment of specific wastestreams, e.g. inorganic sulphate-rich wastewaters such as acid mine drainage, metal polluted groundwater and flue-gas scrubbing waters. Nowadays, sulphur-cycle-based technologies are not solely considered as “end-of-pipe” applications, but their potential for pollution prevention as well as for sulphur, metal or water recovery and re-use are now fully recognized.
2 - Molecular strategies for studies of natural populations of sulphate-reducing microorganisms
- Edited by Larry L. Barton, University of New Mexico, W. Allan Hamilton, University of Aberdeen
-
- Book:
- Sulphate-Reducing Bacteria
- Published online:
- 22 August 2009
- Print publication:
- 31 May 2007, pp 39-116
-
- Chapter
- Export citation
-
Summary
INTRODUCTION
An early focus on the use of molecular techniques to characterize natural populations of sulphate-reducing microorganisms (SRM) derived from the close relationship between their phylogenetic affiliation and their capability to anaerobically respire with sulphate. In other words, all so-far characterized SRM associate with lineages in the tree of life that predominantly consist of sulphate reducers. Known SRM are affiliated with two divisions (phyla) within the Archaea (the euryarchaeotal genus Archaeoglobus species and the crenarchaeotal genera Caldivirga and Thermocladium, affiliated with the Thermoproteales) and five divisions within the Bacteria (the Deltaproteobacteria, endospore-forming Desulfotomaculum, Desulfosporosinus, and Desulfosporomusa species within the Firmicutes division, Thermodesulfovibrio species within the Nitrospira division, and two divisions represented by Thermodesulfobacterium species and the recently isolated Thermodesulfobium narugense, the exact phylogenetic position of the latter is still ambiguous). Most described SRM are either Gram-positive bacteria with a low G+C content or Gram-negative Deltaproteobacteria. However, it is important to note that almost all major physiological properties of cultured and uncultured SRM, such as substrate usage patterns, the ability to completely oxidize a substrate to CO2, and alternative ways of anaerobic energy generation cannot be unambiguously determined from comparative analysis of their 16S rRNA genes.
The generally tight association between phylogenetic affiliation and sulphate-reducing physiology offered a foundation to directly associate the population structure determined by 16S rRNA sequence type and process. These studies have now been complemented by the use of highly conserved genes in the pathway for sulphate respiration.
Contents
- Edited by Larry L. Barton, University of New Mexico, W. Allan Hamilton, University of Aberdeen
-
- Book:
- Sulphate-Reducing Bacteria
- Published online:
- 22 August 2009
- Print publication:
- 31 May 2007, pp v-vi
-
- Chapter
- Export citation
16 - Sulphate-reducing bacteria and their role in corrosion of ferrous materials
- Edited by Larry L. Barton, University of New Mexico, W. Allan Hamilton, University of Aberdeen
-
- Book:
- Sulphate-Reducing Bacteria
- Published online:
- 22 August 2009
- Print publication:
- 31 May 2007, pp 459-482
-
- Chapter
- Export citation
-
Summary
INTRODUCTION
In both natural environments and human-made systems, a phylogenetically diverse and heterogeneous group of anaerobic sulphate-reducing bacteria (SRB) (Barton, 1985; Odom and Singelton, 1993; Postgate, 1984) thrive as members of complex microbial communities, living on surfaces of particles, minerals and manufactured materials, i.e. within biofilms (Characklis and Marshall, 1990; Dar et al., 2005 and references therein).
The presence of biofilms often results in deterioration of colonized substrata. In the case of metallic materials, undesirable change in their properties resulting from material loss under biological influence is termed microbially-influenced corrosion (MIC) or biocorrosion. A number of reviews have been published describing fundamental and practical aspects of MIC (Geesey et al., 2000; Hamilton, 2000; Beech and Coutinho, 2003; Beech and Sunner, 2004).
The annual direct and derived costs of corrosion are estimated to be around 4% of the GNP of developed countries, of which 10–20% are related to biocorrosion (Geesey et al., 2000). In the oil and gas industry, biocorrosion accounts for 15–30% of the corrosion cases, resulting in financial losses in a range of 100 M $ per annum in the USA alone, excluding costs of lost revenues and often necessary remediation treatments. In some cases, for example in the Gulf of Guinea, extremely high rates of pitting-corrosion related to biocorrosion have reduced the life of oil subsea lines to one year (J.-L. Crolet, personal communication).
Sulphate-Reducing Bacteria
- Environmental and Engineered Systems
- Edited by Larry L. Barton, W. Allan Hamilton
-
- Published online:
- 22 August 2009
- Print publication:
- 31 May 2007
-
The sulphate-reducing bacteria (SRB) are a large group of anaerobic organisms that play an important role in many biogeochemical processes. Not only are they of early origins in the development of the biosphere, but their mechanisms of energy metabolism shed light on the limits of life processes in the absence of oxygen. They are widely distributed in nature, and are regular components of engineered systems including, for example, petroleum reservoirs and oil production facilities. SRB are currently subject to extensive genomic studies, which are yielding fresh understanding of their basic biochemical mechanisms, and aiding in the development of novel techniques for the analyses of their environmental roles. This volume provides a timely update on these important microorganisms, from basic science to applications, and will therefore serve as a valuable resource for researchers and graduate students in the fields of microbial ecology, microbial physiology, bioengineering, biogeochemistry and related areas of environmental science.
Plate section
- Edited by Larry L. Barton, University of New Mexico, W. Allan Hamilton, University of Aberdeen
-
- Book:
- Sulphate-Reducing Bacteria
- Published online:
- 22 August 2009
- Print publication:
- 31 May 2007, pp -
-
- Chapter
- Export citation
Preface
-
- By W. Allan Hamilton, University of Aberdeen, Larry L. Barton, University of New Mexico
- Edited by Larry L. Barton, University of New Mexico, W. Allan Hamilton, University of Aberdeen
-
- Book:
- Sulphate-Reducing Bacteria
- Published online:
- 22 August 2009
- Print publication:
- 31 May 2007, pp xvii-xviii
-
- Chapter
- Export citation
-
Summary
Recognition of the biological nature of sulphate reduction in natural environments, and identification of the bacterial species involved dates to the latter part of the nineteenth century, and the seminal work of such giants of the early days of microbiology as Beijerinck and Winogradsky. The central role of environmental studies in highlighting the issues to be addressed and the problems to be solved, has remained to this day a constant theme in microbiological analyses of the sulphate reducers.
The modern era of such analyses, however, can be said to date from the period around 1960 when the demonstrations by Postgate and Peck, respectively, of the presence of cytochromes and of phosphorylation linked to anaerobic respiration in sulphate-reducing bacteria (SRB), fundamentally altered our view of the biochemical nature of these organisms and, in particular, of their mechanisms of energy conservation.
There then followed a period of intense activity centred on: elucidation of the metabolic pathways of substrate utilisation and the mechanisms of energy generation; cultural techniques and the identification of an ever-increasing number of new species; and the appreciation of their significant role in maintaining, or disrupting, the biological balance of many natural and man-made ecosystems.
These themes of biochemistry and cell physiology, phylogeny, and ecology remain central to the understanding of SRB themselves, and of their interactions with other components of the biosphere. In recent years, however, their study has undergone a further paradigm shift with the introduction of the many powerful experimental techniques and analytical approaches of molecular biology.
15 - Enzymatic and genomic studies on the reduction of mercury and selected metallic oxyanions by sulphate-reducing bacteria
- Edited by Larry L. Barton, University of New Mexico, W. Allan Hamilton, University of Aberdeen
-
- Book:
- Sulphate-Reducing Bacteria
- Published online:
- 22 August 2009
- Print publication:
- 31 May 2007, pp 435-458
-
- Chapter
- Export citation
-
Summary
INTRODUCTION
Toxic heavy metals and metalloids constitute an international pollution problem that not only impacts public health but also is of environmental and economic importance. Prokaryotes with the physiological activity of sulphate reduction are found in a number of environmental sites containing toxic metals and these microorganisms have developed several different strategies for resistance to toxic elements. Some bacteria have developed detoxification strategies that are potentially useful for bioremediation. Since sulphate-reducing bacteria (SRB) are found in a large number of contaminated sites containing toxic metals, it is apparent that these organisms have a functional defence system that enables them to persist and even grow under metal stress. The enzymatic metal reduction by SRB offers an alternative to chemical processes to remediate environments containing redox-active toxic metals and metalloids. While Hockin and Gadd discuss in Chapter 14 the bioremediation activities of sulphate-reducing bacteria, this chapter focuses on the enzymatic processes associated with metal reduction. We review results obtained with isolated proteins and discuss the potential of sulphate-reducers by reviewing putative proteins found in their genomes. Reference is made to putative genes present in Desulfovibrio (D.) vulgaris strain Hildenborough (Heidelberg et al., 2004), D. desulfuricans strain G20 (http://www.jgi.doe.gov), Desulfotalea (Des.) psychrophila (Rabus et al., 2004) and Archaeoglobus (A.) fulgidus (Klenk et al., 1997).
ENZYMATIC ACTIVITIES INVOLVING REDOX-ACTIVE ELEMENTS
The detoxification of an environment arising from SRB reductions is considered by many as an important event for bioremediation of various polluted environments In addition to precipitation of metals by biogenic hydrogen sulfide, the SRB are highly capable of reducing many soluble redox-active elements.
3 - Functional genomics of sulphate-reducing prokaryotes
- Edited by Larry L. Barton, University of New Mexico, W. Allan Hamilton, University of Aberdeen
-
- Book:
- Sulphate-Reducing Bacteria
- Published online:
- 22 August 2009
- Print publication:
- 31 May 2007, pp 117-140
-
- Chapter
- Export citation
-
Summary
INTRODUCTION
Besides their challenging and ancient energy metabolism, and applied relevance, much of the interest in sulphate-reducing bacteria arises from their ecophysiological significance in marine environments (Widdel, 1998). In the biologically highly active shelf sediments they contribute to more than 50% of organic carbon remineralization (Jørgensen, 1982), which can only be explained by complete substrate oxidation (Fenchel and Jørgensen, 1977). While this capacity is not present among the frequently isolated and intensively studied Desulfovibrio spp., it could be demonstrated with e.g. the newly isolated Desulfobacter postgatei (Widdel and Pfennig, 1981) and Desulfobacterium autotrophicum (Brysch et al., 1987). The latter employs the C1/CO-dehydrogenase pathway for complete oxidation of acetate to CO2 as well as for CO2-fixation (Schauder et al., 1989). Most of the known sulphate-reducing bacteria can be grouped into the two deltaproteobacterial families Desulfovibrionaceae (Devereux et al., 1990) or Desulfobacteriaceae (Widdel and Bak, 1992). This phylogenetic distinction is to a large extent paralleled by the capacities for incomplete (to acetate) and complete (to CO2) oxidation of organic substrates, respectively.
At present, more than 450 prokaryotic genomes have been completely sequenced and about 1000 further prokaryotic genomes are in progress (http://www.genomesonline.org). While most genome projects primarily reflect biotechnological or biomedical research interests, environmentally relevant microorganisms have been selected for genome sequencing projects only during the last few years. This chapter provides an overview of the technologies involved and of the current status of genomic research with sulphate-reducing prokaryotes.
5 - Response of sulphate-reducing bacteria to oxygen
- Edited by Larry L. Barton, University of New Mexico, W. Allan Hamilton, University of Aberdeen
-
- Book:
- Sulphate-Reducing Bacteria
- Published online:
- 22 August 2009
- Print publication:
- 31 May 2007, pp 167-184
-
- Chapter
- Export citation
-
Summary
PRESENCE OF SULPHATE-REDUCING BACTERIA IN OXIDISED HABITATS
During the second half of the nineteenth century the formation of sulphide from sulphate was recognised as a biogenic process (Meyer, 1864). While it was initially suggested that algae were the catalysing organisms (Cohn, 1867), Hoppe-Seyler demonstrated in 1886 that the process required anoxic conditions and was chemotrophic, requiring external electron donors. In 1895, Beijerinck proved that sulphate reduction is catalysed by bacteria and described the first pure culture, Spirillum desulfuricans. This organism was described as strictly anaerobic and was irreversibly inhibited by oxygen.
The view that sulphate-reducing bacteria (SRB) are extremely sensitive to oxygen started to change in the late 1970s when sulphate reduction was demonstrated to occur also in oxidised sediment layers which showed no traces of FeS and were considered oxic (Jørgensen, 1977). Similarly, cultivation-based studies revealed the presence of viable sulphate reducers within these layers (Laanbroek and Pfennig, 1981; Battersby et al., 1985; Jørgensen and Bak, 1991). However, it was found that oxygen did not penetrate as deep into sediments as previously assumed and that large parts of the oxidised, hence FeS-free layers, were in fact anoxic. In sediment layers that contain oxidised manganese or iron species, sulphide can be chemically reoxidised to elemental sulphur (Aller and Rude, 1988), or, in the case of manganese oxide, even to thiosulphate (Schippers and Jørgensen, 2001).
6 - Biochemical, proteomic and genetic characterization of oxygen survival mechanisms in sulphate-reducing bacteria of the genus Desulfovibrio
- Edited by Larry L. Barton, University of New Mexico, W. Allan Hamilton, University of Aberdeen
-
- Book:
- Sulphate-Reducing Bacteria
- Published online:
- 22 August 2009
- Print publication:
- 31 May 2007, pp 185-214
-
- Chapter
- Export citation
-
Summary
INTRODUCTION
Sulphate-reducing bacteria (SRB) are anaerobes, which derive energy for growth from anaerobic metabolism, coupling the oxidation of organic substrates with the dissimilatory reduction of sulphate to hydrogen sulphide (sulphate respiration). Although generally considered as strict anaerobes, more and more data indicate a higher abundance and metabolic activity in oxic zones of biotopes, such as marine and freshwater sediments, than in neighbouring anoxic zones (Ravenschlag et al., 2000; Sass et al., 1997; 1998). A well-documented example of sulphate reduction under oxic conditions is also provided by cyanobacterial mats. Here a zone of photosynthetic oxygen synthesis overlaps with a zone of sulphide production by SRB and a zone of oxygen-dependent microbial sulphide oxidation, creating steep, opposing gradients of oxygen and sulphide, which fluctuate with the rhythm of day and night (Canfield and des Marais, 1991; Teske et al., 1998; Caumette et al., 1994). In cyanobacterial mats from the saline evaporation pond in Baja California, Desulfobacter and Desulfobacterium are restricted to greater depths while the Desulfococcus and Desulfovibrio groups are predominant in the upper part of the photo-oxic zone (Risatti et al., 1994). The high numbers of SRB found in these oxic environments indicate that these organisms are able to deal with temporal exposures to oxygen concentrations as high as 1.5 mM (Sigalevich and Cohen, 2000).
In these oxygen-exposed systems SRB of the genus Desulfovibrio are among the most oxygen-tolerant, e.g. Desulfovibrio oxyclinae was isolated from Solar Lake microbial mats (Krekeler et al., 1997) and Desulfovibrio desulfuricans strain DvO1 was isolated from activated sludge aerated to atmospheric oxygen saturation (Kjeldsen et al., 2005).
Preface
- C. Ross Ethier, University of Toronto, Craig A. Simmons, University of Toronto
-
- Book:
- Introductory Biomechanics
- Published online:
- 05 June 2012
- Print publication:
- 12 March 2007, pp xv-xvi
-
- Chapter
- Export citation
-
Summary
For some years, we have taught an introductory course in biomechanics within the Department of Mechanical and Industrial Engineering at the University of Toronto. We have been unable to find a textbook suitable for the purpose of introducing engineers and others having a “hard science” background to the field of biomechanics. That is not to say that excellent books on biomechanics do not exist; in fact, there are many. However, they are typically at a level that is too advanced for an introductory course, or they cover too limited a subset of topics for purposes of an introductory course.
This book represents an attempt to fill this void. It is not meant to be an extensive treatise on any particular branch of biomechanics, but rather to be an introduction to a wide selection of biomechanics-related topics. Our hope is that it will aid the student in his or her introduction to the fascinating world of bioengineering, and will lead some to pursue the topic in greater detail.
In writing this book, we have assumed that the reader has a background in engineering and mathematics, which includes introductory courses in dynamics, statics, fluid mechanics, thermodynamics, and solid mechanics. No prior knowledge of biology, anatomy, or physiology is assumed, and in fact every section begins with a review of the relevant biological background. Each chapter then emphasizes identification and description of the essential aspects of the related biomechanics problems.
Appendix: The electrocardiogram
- C. Ross Ethier, University of Toronto, Craig A. Simmons, University of Toronto
-
- Book:
- Introductory Biomechanics
- Published online:
- 05 June 2012
- Print publication:
- 12 March 2007, pp 489-497
-
- Chapter
- Export citation
-
Summary
The electrocardiogram (ECG) is important for several reasons. First and foremost, it provides information about the activity of the heart muscle, and it is therefore an essential non-invasive clinical tool used to diagnose certain cardiac abnormalities. From the biomechanical viewpoint, it provides a convenient reference signal for time-varying quantities in the vascular tree, specifically pulsatile flow, pressure, and arterial pulsation. Here we briefly describe the main features of the ECG.
The contraction of cardiac muscle is controlled by an intrinsically generated electrical signal. In other words, the heart is responsible for its own stimulation, although the rate of stimulation can be modulated by external factors. In order to understand the behavior of this pacemaker system, we must first study several basic facts about the propagation of electric signals in excitable cells, a category that includes nerve and muscle cells. The general aspects of the description that follows are true for all excitable cells; however, the details are specific to cardiac muscle cells.
Normally, the cell's interior is held at a negative electrical potential measured with respect to the surrounding extracellular fluid. This small potential difference (the resting potential, equal to approximately −90 mV) exists because of a difference in ionic composition across the cell's membrane (Table A.1). This difference in composition is actively maintained by pumps residing in the cell's membrane that transport ions against their concentration gradient.
3 - Hemodynamics
- C. Ross Ethier, University of Toronto, Craig A. Simmons, University of Toronto
-
- Book:
- Introductory Biomechanics
- Published online:
- 05 June 2012
- Print publication:
- 12 March 2007, pp 119-163
-
- Chapter
- Export citation
-
Summary
The term hemodynamics comes from the Greek words haima (blood) and dunamis (power) and refers to the movement and deformation (i.e., flow) of blood, and the forces that produce that flow. In this chapter we will examine this fascinating (and complex) topic.
Everyone is familiar with blood's role as a transport medium: it carries oxygen and nutrients to metabolically active tissues, returns carbon dioxide to the lungs, delivers metabolic end-products to the kidneys, etc. However, the reader should be aware that blood does much more than simply deliver substances to target tissues. For example, it:
provides a buffering reservoir to control the pH of bodily fluids
serves as an important locus of the immune system
transports heat, usually from centrally located tissues to distal ones, in order to help maintain a suitable temperature distribution throughout the body.
Unfortunately, in this book we will not be able to examine all of these roles, and to a large extent we will simply view blood as a passive carrier, a fluid that transports physiologically important compounds within the body. However, within this context, it will soon become clear that something so “simple” as an analysis of blood flow as a transport mechanism is non-trivial. We begin by examining blood rheology.
Blood rheology
Rheology is the study of how materials deform and/or flow in response to applied forces. The applied forces are quantified by a quantity known as the stress, defined as the applied force per unit area.
4 - The circulatory system
- C. Ross Ethier, University of Toronto, Craig A. Simmons, University of Toronto
-
- Book:
- Introductory Biomechanics
- Published online:
- 05 June 2012
- Print publication:
- 12 March 2007, pp 164-239
-
- Chapter
- Export citation
-
Summary
We now turn our attention to the system that transports the blood: the heart and blood vessels. From an engineering viewpoint, the circulatory system consists of a remarkably complex branching network of tubes that convey the blood (the vasculature; Fig. 4.1), and two pulsatile pumps in series to force the blood through the tubes (the heart). The vasculature consists of arteries, arterioles, capillaries, venules, and veins. On average, no cell in the body is more than approximately 40 μm away from a capillary, and almost every tissue is thoroughly invested with a capillary network. A typical human contains approximately 5 liters of blood, and at rest the heart pumps approximately 6l/min; consequently, on average, blood circulates throughout the body about once per minute. In this chapter, we emphasize the operation of the components of the circulatory system, how they interact with one another, and how they work in concert to deliver blood to target tissues.
Anatomy of the vasculature
For reasons to be described below, it is conventional to divide the vasculature into two parts: the pulmonary and systemic circulations. The loop from the right heart, through the lungs, and back to the left heart is known as the pulmonary circulation; the loop from the left heart to the body and back to the right heart is the systemic circulation. Both the pulmonary and systemic vasculature have a similar topology.
7 - The respiratory system
- C. Ross Ethier, University of Toronto, Craig A. Simmons, University of Toronto
-
- Book:
- Introductory Biomechanics
- Published online:
- 05 June 2012
- Print publication:
- 12 March 2007, pp 282-331
-
- Chapter
- Export citation
-
Summary
The function of the respiratory system is to exchange O2 and CO2 with the blood. To understand this system from a bioengineering viewpoint, we will first discuss the gross anatomy of the lungs and their associated structures, and then discuss the mechanics of breathing.
Gross anatomy
We divide the respiratory system into two subsystems: the conducting airways and the associated structures.
The conducting airways and pulmonary vasculature
The conducting airways form a fantastically complex branching tree designed to transport air efficiently into the alveoli, the smallest air-filled structures in the lung where blood/gas exchange takes place. Air enters through the mouth or nose then passes through (in order): the pharynx (the throat), the larynx (the voice box), and the trachea (the large tube passing down the neck). The trachea splits to form two bronchi (singular: bronchus), each of which feed air to one of the lungs (Fig. 7.1, color plate).
Each bronchus splits to form bronchioles, which, in turn, split to form smaller bronchioles, and so on (Fig. 7.2). After about 16 levels of branching, we reach the terminal bronchioles, which are the smallest structures that have a purely air-conducting function, that is, in which essentially no blood/gas exchange takes place (Fig. 7.3). In adult lungs, the structures distal to the terminal bronchioles consist of several generations of respiratory bronchioles, alveolar ducts and alveolar sacs, which collectively are known as the acinus; this is where the gas exchange occurs (Fig. 7.4).
8 - Muscles and movement
- C. Ross Ethier, University of Toronto, Craig A. Simmons, University of Toronto
-
- Book:
- Introductory Biomechanics
- Published online:
- 05 June 2012
- Print publication:
- 12 March 2007, pp 332-378
-
- Chapter
- Export citation
-
Summary
Together, muscles and bones confer structure and the capacity for motion to the body. Any analysis of locomotion (Ch. 10) must therefore have as a basis an understanding of muscle and bone mechanics.
There are three types of muscle, each having particular characteristics.
Skeletal muscle. Skeletal muscles comprise 40 to 45% of total body weight. They are usually attached to bones via tendons, are responsible for locomotion and body motion, and are usually under voluntary control.
Smooth muscle. Smooth muscle is typically found surrounding the lumen of “tubes” within the body, such as blood vessels, the urinary tract, and the gastrointestinal tract. Smooth muscle is responsible for controlling the caliber (size) of the lumen and also for generating peristaltic waves (e.g., in the gastrointestinal tract). Control of smooth muscle is largely involuntary.
Cardiac muscle. Cardiac muscle makes up the major bulk of the heart mass and is sufficiently unique to be considered a different muscle type. It is under involuntary control.
In this chapter we will concentrate on skeletal muscle only.
There are three types of skeletal muscle, classified according to how the muscles produce ATP, which is used during the contraction process. The two basic ATP-production strategies are:
Aerobic. In aerobic respiration, ATP is produced by the breakdown of precursors in the presence of O2. This is a high efficiency pathway but cannot proceed if O2 is not present.
Anaerobic. In anaerobic respiration (also known as glycolysis), ATP is produced without O2 present. This pathway is less efficient than aerobic respiration and produces the undesirable by-product lactic acid. Accumulation of lactic acid in muscle tissue produces the characteristic ache that follows too strenuous a workout.