Ross & Wilson Anatomy and Physiology in Health and Illness (3 page)

The skin

Resistance and immunity

The musculoskeletal system

Introduction to genetics

The reproductive systems

Glossary

Normal values

Bibliography

Index

Section 1

The body and its constituents

CHAPTER 1

Introduction to the human body

Levels of structural complexity
4

The internal environment and homeostasis
4

Homeostasis
5

Homeostatic imbalance
7

Survival needs of the body
7

Communication
7

Internal communication
9

Intake of raw materials and elimination of waste
11

Protection and survival
12

Introduction to the study of illness
14

Aetiology
15

Pathogenesis
15

ANIMATIONS

1.1
Anatomy turntable
4

1.2
Cardiovascular (circulatory) system
8

1.3
Airflow through the lungs
11

1.4
The alimentary canal
11

1.5
Urine flow
12

The human body is rather like a highly technical and sophisticated machine. It operates as a single entity, but is made up of a number of systems that work interdependently. Each system is associated with a specific, and sometimes related, function that is normally essential for the well-being of the individual. Should one system fail, the consequences can extend to others, and may reduce the ability of the body to function normally. Integrated working of the body systems ensures survival. The human body is therefore complex in both structure and function, and this book aims to explain the fundamental structures and processes involved.

Anatomy
is the study of the structure of the body and the physical relationships between body systems.
Physiology
is the study of how the body systems work, and the ways in which their integrated activities maintain life and health of the individual.
Pathology
is the study of abnormalities and how they affect body functions, often causing illness. The final section of this chapter provides a framework for studying diseases, an outline of mechanisms that cause disease and some common disease processes. Building on the normal anatomy and physiology, relevant illnesses are considered at the end of the later chapters.

Levels of structural complexity

Learning outcome

After studying this section you should be able to:

describe the levels of structural complexity within the body.

Within the body are different levels of structural organisation and complexity. The most fundamental level is chemical.
Atoms
combine to form
molecules
, of which there are a vast range in the body. The structures, properties and functions of important biological molecules are considered in
Chapter 2
.
Cells
are the smallest independent units of living matter and there are trillions of them within the body. They are too small to be seen with the naked eye, but when magnified using a microscope different types can be distinguished by their size, shape and the dyes they absorb when stained in the laboratory. Each cell type has become
specialised
, and carries out a particular function that contributes to body needs.
Figure 1.1
shows some highly magnified nerve cells. In complex organisms such as the human body, cells with similar structures and functions are found together, forming
tissues
. The structure and functions of cells and tissues are explored in
Chapter 3
.

Figure 1.1 
Coloured scanning electron micrograph of some nerve cells (neurones).

Organs
are made up of a number of different types of tissue and have evolved to carry out a specific function.
Figure 1.2
shows that the stomach is lined by a layer of epithelial tissue and that its wall contains layers of smooth muscle tissue. Both tissues contribute to the functions of the stomach, but in different ways.

Figure 1.2 
The levels of structural complexity.

Systems
consist of a number of organs and tissues that together contribute to one or more survival needs of the body. For example the stomach is one of several organs of the digestive system, which has its own specific function. The human body has several systems, which work interdependently carrying out specific functions. All are required for health. The structure and functions of body systems are considered in later chapters.

The internal environment and homeostasis

Learning outcomes

After studying this section you should be able to:

define the terms internal environment and homeostasis