Abstract
Transport by diffusion is an efficient process on very short distances only. Any organism above a certain (small) size therefore requires some kind of circulatory system that can deliver nutrients to the tissues and can clear out waste products. The circulatory system has a diversity of designs in the animal kingdom. In most cases however, an exchange medium, i.e. the blood, is physically circulated and brought into contact with every part of every tissue in the body in order for the basic process of exchange between blood and tissue to proceed efficiently. This exchange process primarily takes place in the smallest vessels of the microcirculation, the capillaries. The density of these vessels in a given tissue reflects its basal metabolic activity such that high densities and, hence, potentially high exchange rates, are found in tissues with high metabolic activity, e.g. the kidneys and the heart. At the other extreme are avascular tissues such as the cartilage of the joints. Such tissues seem to rely on diffusion over long distances and they are characterized by very low metabolic activity. In a given tissue, capillarity may also change with long-term changes in average metabolic activity as it has been observed in endurance trained skeletal muscles [8].
| Original language | Danish |
|---|---|
| Title of host publication | Biosimulation in Biomedical Research, Health Care and Drug Development Biosimulation in Biomedical Research, Health Care and Drug Development |
| Editors | Erik Mosekilde, Olga Sosnovtseva, Amin Rostami-Hodjegan |
| Number of pages | 16 |
| Place of Publication | Wien |
| Publisher | Springer |
| Publication date | 1 Jan 2014 |
| Pages | 237-252 |
| Chapter | 11 |
| ISBN (Print) | 978-3-7091-0417-0 |
| DOIs | |
| Publication status | Published - 1 Jan 2014 |