Introduction

1 Introduction



Learning objectives


After reading this chapter you should understand:


• the characteristics of living matter

• the terms used in anatomy


The characteristics of living matter


Organic matter is that which is living or has been alive, e.g. wood or coal. Inorganic matter is that which is not living and has never been alive, e.g. water or iron. Inorganic substances can be built up into organic compounds by living organisms.


All living matter is composed of small units called cells. Some organisms, such as bacteria, consist of one single cell; others, like human beings, consist of many hundreds of millions of cells, all functioning together to make a complete whole. All living cells, however simple, have certain characteristics which are always present. These characteristics are:


• activity

• respiration

• digestion and absorption of food

• excretion

• growth and repair

• reproduction

• irritability.


Activity


This is the most striking characteristic of living matter. It is more apparent in the animal world than in the vegetable world, as the animal must move about in search of food, but even in plants the buds can be seen to break out in the spring, and with a microscope, activity becomes as obvious in the plant as in the animal. There can never be any activity without energy. Cars are driven by energy derived from petrol, trains are generally moved by electrical energy, and in living matter the energy is also obtained by burning fuel. The fuel for the human body is the food eaten, particularly carbohydrates and fats. Oxygen is also necessary for the combustion of fuel, and living things obtain their oxygen from the air or water where they live. Combustion of fuel produces waste products, such as carbon dioxide and water, which must be disposed of.


The combustion of fuel in living matter produces some energy for work and some energy in the form of heat. The body is economical in that it produces more work energy and less heat for each unit of food consumed, but the heat produced by combustion is not altogether wasted for some heat is needed. The body can remain healthy only within a narrow temperature range of 36–37.5°C and any heat produced in excess of this must be eliminated if life is to continue.



Respiration


All living matter requires oxygen and gives off carbon dioxide. The oxygen is required for combustion, or oxidation, of food, and carbon dioxide is the waste product of combustion. This process of taking in oxygen and giving off carbon dioxide is called respiration and it is continuous throughout life. The amount of oxygen required and the quantity of carbon dioxide given off vary with the amount of activity taking place.


During sleep the human body requires comparatively little oxygen but it requires much more during strenuous exercise.



Digestion and absorption of food


All living matter requires food. Some food can be absorbed as it is but most of it must be broken down into substances which have smaller and simpler molecules before it can be absorbed. The process of breaking down complex foods into smaller substances is termed digestion. It is brought about by enzymes, which are themselves protein substances and which act upon the food, preparing it for absorption.

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Jul 18, 2016 | Posted by in NURSING | Comments Off on Introduction

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