27. Introduction to the cardiovascular system
27. Introduction to the cardiovascular system
- Gillian Pocock, Gillian PocockSenior Lecturer in Clinical Science, Canterbury Christ Church University, Canterbury, UK
- Christopher D. RichardsChristopher D. RichardsEmeritus Professor of Experimental Physiology, Division of Physiology, Pharmacology and Neuroscience, Faculty of Life Sciences, University College London, London, UK
- and David A. RichardsDavid A. RichardsAssociate Professor, Department of Basic Pharmaceutical Sciences, Husson University School of Pharmacy, Bangor, Maine, USA
Abstract
This chapter considers the exchange of nutrients and waste products between the cells and the environment of unicellular organisms and simple animals. Examples include sponges. These can be accomplished by simple diffusion across the cell membranes. The chapter cites diffusion as a random process in three dimensions, the time required for equilibration increases rapidly with increasing distance. In more complex animals, diffusion of nutrients by itself would not suffice to permit adequate exchange of nutrients and waste products, as most cells are separated from the external environment by a considerable distance. The chapter describes the organization of the circulation, its gross anatomy, the structure of the blood vessels, and their innervation. One of the primary functions of the circulatory system is to promote the carriage of oxygen and nutrients to the cells and remove the products of metabolism.
