Biological Sciences
Mass Transport in Animals
Mass transport in animals refers to the movement of substances such as oxygen, nutrients, and waste products throughout the body. This process is essential for maintaining homeostasis and providing cells with the necessary resources for survival. In animals, mass transport occurs through mechanisms such as the circulatory system, which utilizes the heart to pump blood and the blood vessels to distribute substances to various tissues and organs.
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3 Key excerpts on "Mass Transport in Animals"
eBook - PDF- Joseph D. Bronzino, Donald R. Peterson(Authors)
- 2018(Publication Date)
- CRC Press(Publisher)
8 -1 8.1 Introduction Transport phenomena, and particularly mass transfer and chemical reaction, govern a great variety of physiological and pathological processes, and they supplement in a nontrivial way genetic factors in both organism development and species evolution. For humans and other mammals, of primary interest here, the body may in fact be viewed as a complex and hierarchical transport/reaction system supplying the needs of genes and protecting them from the external environment. This is suggested in Figure 8.1 where four major organs are seen to interact directly with the external environment and, via an extremely complex series of mass transport processes, with other organs, all body cells, and ulti-mately their genes. These processes range from convective transport via blood and pulmonary gases to extremely complex forced diffusion mechanisms at the cellular and subcellular level. Our purpose here is to suggest effective bases for modeling and manipulating selected subsystems of living bodies, and it must be recognized at the outset that a complete description is impossible. Just a glance at an atlas of the human anatomy will make this clear. The body will always be what Malcolm Gladwell [26] calls a mystery: a problem for which no complete solution exists. Our approach is to suggest approximations simple enough to be soluble, testable, and hopefully of some utility: what Gladwell calls 8 Transport/Reaction Processes in Biology and Medicine E.N. Lightfoot University of Wisconsin 8.1 Introduction ...................................................................................... 8 -1 8.2 Macroscopic Approximations: Allometry .................................... 8 -2 8.3 Orders of Magnitude and Characteristic Time Constants ........ 8 -3 8.4 Time Constant Ratios ......................................................................
eBook - PDFBiosimulation
Simulation of Living Systems
- Daniel A. Beard(Author)
- 2012(Publication Date)
- Cambridge University Press(Publisher)
2 Transport and reaction of solutes in biological systems Overview Transport of mass, into, out of, and within biological systems (including single cells, multicellular organisms, and even ecological systems) is fundamental to their operation. The subject of transport phenomena is treated in great depth in classic texts [10], as well as in books focused on biological systems [62]. Here we explore a number of examples that allow us to see how fundamental transport phenomena are accounted for in a wide range of biological systems. Specifically, we develop and apply basic frameworks for simulating transport in the following sorts of systems: Well-mixed systems. 1 The defining characteristic of these systems is that they are fluid systems (often aqueous solutions in biological application) with the solutes of interest distributed homogeneously (i.e., well mixed) over the timescales of interest. An example of a well-mixed system is the aquarium studied in the previous chapter. Other examples are chemical reaction sys- tems inside cells or compartments within cells when spatial gradients of the intracellular reactants do not significantly influence the behaviors that are sim- ulated. Models of well-mixed systems (or models that adopt the well-mixed assumption) do not explicitly account for the spatial distribution of the vari- ables simulated. For biochemical systems this means that, at any given time, concentrations are constant throughout a compartment. The kinetics of such systems are typically described by ordinary differential equations, as in the examples of Section 2.1 of this chapter and in Chapter 3. Note that different physical mechanisms may justify the well-mixed assump- tion in different systems. In cells, molecular diffusion can effectively drive mixing on timescales on the order of seconds or less. In the previous chapter’s aquarium, mixing is driven by a mechanical pump that circulates the water.
- Gerald Miller(Author)
- 2022(Publication Date)
- Springer(Publisher)
1 C H A P T E R 1 Biomedical Mass Transport Mass transport within the human body is a vital process that affects how the lungs function in transferring air and its components to the bloodstream, how the capillaries function in transfer- ring nutrients and gases to surrounding body tissues, and how the kidneys function in transferring metabolic waste products and excess water from the blood into the urine. Mass transfer processes also occur in artificial devices such as artificial kidneys (dialysis), artificial ventilators, and respirators. Mass transfer in the body also affects transport across cell membranes, which controls processes in millions of cells affecting every area of the body. The majority of mass transfer occurs across small membranes of thin surfaces in order to shorten the distance over which substances must travel from point A to point B. This is true of cells in the body, which are quite thin as well as artificial devices whose components are manufactured to be very thin. 1.1 ANALYSIS OF RESPIRATION AND GAS TRANSPORT The human lungs control gas exchange from our environment into the bloodstream by means of pressure and concentration gradients. When breathing, air enters the lungs through a large entrance, the trachea, and eventually branches into smaller and smaller segments until reaching the smallest elements of the lungs, the alveoli. Each of these thin elements is in close proximity to blood in pulmonary capillaries, which are the smallest and thinnest of the blood vessels. With each of the alveoli in close proximity to a pulmonary capillary, the distance for gas exchange is very short, which thus shortens the time by which complete gas exchange occurs. A diagram of the lungs and its branching system is shown in Figure 1.1. The two human lungs contain approximately 300 to 500 million alveoli having a total surface area of about 75 m 2 in adults, the size of a tennis court.
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