Page 212 - IGC BOOK

by the lungs’ defense mechanisms before they can travel down into the lungs; smaller particles are
not trapped by these defences and will travel deep into the lungs.

These two types of dust are called:

• Inhalable dust – particles of all sizes that can be inhaled into the nose and mouth.
• Respirable dust – particles less than 7 microns (7/1,000 mm) in diameter that can travel deep into
the lungs on inhaled breath.

The Human Body

Physiology & Anatomy
Physiology is the study of the function of the body, whereas anatomy is the study of the
structure of the body.

The body consists of millions of cells, which form ‘tissues’, e.g. muscular tissue and nervous
tissue, and organs, e.g. the heart, brain and kidneys.

Nerve cells have long fibres, which are capable of carrying electrical impulses; some cells in
the stomach wall produce hydrochloric acid to digest food and cells in the glands produce
chemicals, which influence other cells, such as the thyroid gland that produces adrenalin.

The work of each cell is controlled. If something affects the control of a cell, it may grow
rapidly or react in an unusual way. This sort of cell behaviour occurs in cancer when a group
of cells grow abnormally and invade adjacent tissues.

There are five main functional systems within the human body and each of these systems
comprises one or more organs. If one organ of the body is not functioning correctly then
others may also be affected and affect the health of the individual as a whole. The five
systems are the: respiratory system; digestive system; cardiovascular system; urinary
system; and skin.

The Respiratory System

The respiratory system consists of the respiratory tract
(nose, mouth, larynx, trachea and bronchi), and lungs
(bronchioles and alveoli).

The lungs are expanded by means of the diaphragm and
draw in air that reaches the tiny air sacs (alveoli). The wall
of the alveoli is so thin that air passes through it and
enters the fine blood vessels surrounding the alveoli. The Respiratory System.

ENSIGN| Unit IG2 – Element 7 – Chemical and Biological 7
Agents