Introduction to the human body shoulders. The skeletal system provides the bony frame- end in alveoli, millions of tiny air sacs in each lung. They work of the body( Ch. 16), and movement takes place at are surrounded by a network of illaries and are joints between bones. Skeletal muscles which move the the sites where the vital process of gas exchange between bones lie between them and the skin. They are stimulated the lungs and the blood takes place( Fig. 1.11) by the part of the nervous system under conscious Nitrogen, which makes up about 80% of atmospheric (voluntary) control. Some non-verbal communication, air, is breathed in and out but, in this gaseous form, it e.g. changes in facial expression, may not involve the cannot be used by the body. The nitrogen needed by the movement of bones body is present in protein-containing foods, mainly meat Intake of raw materials and Dietary intake elimination of waste Nutrition is considered in Chapter 11, A balanced diet is This section considers the substances that must be taken important for health and provides nutrients, substances into and excreted from the body Oxygen, water and food that are absorbed, often following digestion, and pro- are the substances the body needs to take in, and carbon mote body function. Nutrients include water, carbohy dioxide, urine and faeces are those excreted drates, proteins, fats, vitamins and mineral salts. They are required for: Intake of oxygen maintaining water balance within the body Oxygen is a gas that makes up about 21% of atmospheric energy production, mainly carbohydrates and fats air. a continuous supply is essential for human life synthesis of large and complex molecules, using because most chemical activities that take place in the mineral salts, proteins, fats, carbohydrates and in its prese needed in the series of chemical reactions that result in cell building, growth and repair, especially proteins the release of energy from nutrient The respiratory system carries air between the noe. Digestion nd the lungs during breathing(Ch. 10). Air passes gestive system 11 through a system of passages consisting of the pharynx eaten is chemically complex and seldom in a form the (also part of the alimentary canal), the larynx(voice box), body cells can use Its function is to break down or digest the trachea, two bronchi(one bronchus to each lung food so that it can be absorbed into the circulation and a large number of bronchial passages(Fig. 1. 10). Th then used by body cells. The digestive system consists of the alimentary tract and accessory glands(Fig. 1. 12) Nasal cavity Alimentary canal. This is a tube that begins at the Oral cavity mouth and continues through the pharynx, oesophagus, Trachea stomach, small and large intestines, rectum and anus Glands. The accessory organs situated outside the ali- mentary canal with ducts leading into it are the salivary Respiratory bronchiole - Capillaries Figure 1.10 The respiratory system Figure 1.11 Alveoli: the site of gas exchange
Introduction to the human body shoulders. The skeletal system provides the bony framework of the body (Ch. 16), and movement takes place at joints between bones. Skeletal muscles which move the bones lie between them and the skin. They are stimulated by the part of the nervous system under conscious (voluntary) control. Some non-verbal communication, e.g. changes in facial expression, may not involve the movement of bones. Intake of raw materials and elimination of waste This section considers the substances that must be taken into and excreted from the body. Oxygen, water and food are the substances the body needs to take in, and carbon dioxide, urine and faeces are those excreted. Intake of oxygen Oxygen is a gas that makes up about 21 % of atmospheric air. A continuous supply is essential for human life because most chemical activities that take place in the body cells can occur only in its presence. Oxygen is needed in the series of chemical reactions that result in the release of energy from nutrients. The respiratory system carries air between the nose and the lungs during breathing (Ch. 10). Air passes through a system of passages consisting of the pharynx (also part of the alimentary canal), the larynx (voice box), the trachea, two bronchi (one bronchus to each lung) and a large number of bronchial passages (Fig. 1.10). These end in alveoli, millions of tiny air sacs in each lung. They are surrounded by a network of tiny capillaries and are the sites where the vital process of gas exchange between the lungs and the blood takes place (Fig. 1.11). Nitrogen, which makes up about 80% of atmospheric air, is breathed in and out but, in this gaseous form, it cannot be used by the body. The nitrogen needed by the body is present in protein-containing foods, mainly meat and fish. Dietary intake Nutrition is considered in Chapter 11. A balanced diet is important for health and provides nutrients, substances that are absorbed, often following digestion, and promote body function. Nutrients include water, carbohydrates, proteins, fats, vitamins and mineral salts. They are required for: • maintaining water balance within the body • energy production, mainly carbohydrates and fats • synthesis of large and complex molecules, using mineral salts, proteins, fats, carbohydrates and vitamins • cell building, growth and repair, especially proteins. Digestion The digestive system has developed because the food eaten is chemically complex and seldom in a form the body cells can use. Its function is to break down or digest food so that it can be absorbed into the circulation and then used by body cells. The digestive system consists of the alimentary tract and accessory glands (Fig. 1.12). Alimentary canal. This is a tube that begins at the mouth and continues through the pharynx, oesophagus, stomach, small and large intestines, rectum and anus. Glands. The accessory organs situated outside the alimentary canal with ducts leading into it are the salivary 11 Figure 1.10 The respiratory system. Figure 1.11 Alveoli: the site of gas exchange
he body and its constituents Salivary gland Liver Stomach Figure 1. 12 The digestive system Figure 1. 13 The urinary system glands, the pancreas and the liver. There are also many ly waste products mainly of protein breakdown,e.gurea small glands situated in the walls of the alimentary canal. Under the influence of hormones from the endocrine sys- Most of these glands synthesise digestive enzymes that are tem the kidneys regulate water balance within the body. involved in the chemical breakdown of food They also play a role in maintaining blood pH within the normal range. The bladder stores urine until it is excreted Metabolism during micturition. The process of micturition (passing This is the sum total of the chemical activity in the body. urine)also involves the nervous system It consists of two groups of processes Faeces m anabolism, building or synthesising large and complex The waste materials from the digestive system are a catabolism, breaking down substances to provide excreted as faeces containing energy and raw materials for anabolism, and a indigestible food residue that remains in the substances for excretion as waste alimentary canal because it cannot be absorbed The sources of energy are mainly the carbohydrates an a bile from the liver, which contains the waste products from the breakdown of red blood cells fats provided by the diet. If these are in short supply, large numbers of microbes proteins are used Elimination of faeces (defecation) als Elimination of waste nervous system Carbon dioxide This is continually excreted by the respiratory system, as Protection and survival described above. Carbon dioxide is a waste product In this section relevant activities will be outlined under of cellular metabolism. It dissolves in water to form an the following headings: protection against the external acid that must be excreted in appropriate amounts to environment, resistance and immunity, movement and maintain the pH (acidity or alkalinity)of the blood in its reproduction normal range Urine Protection against the external environment he kidneys, which are part of the uri- On the body surface, the skin(Ch. 14)mainly provides nary system( Ch 13). The organs of the urinary system this. It consists of two layers: the epidermis and the are shown in Figure 1.13. Urine consists of water and dermis
The body and its constituents 12 Figure 1.12 The digestive system. glands, the pancreas and the liver. There are also many small glands situated in the walls of the alimentary canal. Most of these glands synthesise digestive enzymes that are involved in the chemical breakdown of food. Metabolism This is the sum total of the chemical activity in the body. It consists of two groups of processes: • anabolism, building or synthesising large and complex substances • catabolism, breaking down substances to provide energy and raw materials for anabolism, and substances for excretion as waste. The sources of energy are mainly the carbohydrates and fats provided by the diet. If these are in short supply, proteins are used. Elimination of waste Carbon dioxide This is continually excreted by the respiratory system, as described above. Carbon dioxide is a waste product of cellular metabolism. It dissolves in water to form an acid that must be excreted in appropriate amounts to maintain the pH (acidity or alkalinity) of the blood in its normal range. Urine This is formed by the kidneys, which are part of the urinary system (Ch. 13). The organs of the urinary system are shown in Figure 1.13. Urine consists of water and Figure 1.13 The urinary system. waste products mainly of protein breakdown, e.g. urea. Under the influence of hormones from the endocrine system the kidneys regulate water balance within the body. They also play a role in maintaining blood pH within the normal range. The bladder stores urine until it is excreted during micturition. The process of micturition (passing urine) also involves the nervous system. Faeces The waste materials from the digestive system are excreted as faeces containing: • indigestible food residue that remains in the alimentary canal because it cannot be absorbed • bile from the liver, which contains the waste products from the breakdown of red blood cells • large numbers of microbes. Elimination of faeces (defecation) also involves the nervous system. Protection and survival In this section relevant activities will be outlined under the following headings: protection against the external environment, resistance and immunity, movement and reproduction. Protection against the external environment On the body surface, the skin (Ch. 14) mainly provides this. It consists of two layers: the epidermis and the derrnis
Introduction to the human body The epidermis lies superficially and is composed of sev- Following exposure to an antigen, lifelong immunity eral layers of cells that grow towards the surface from its against further invasion by the same antigen usually deepest layer. The surface layer consists of dead cells that develops Over a lifetime, an individual gradually builds are constantly being rubbed off and replaced from below up immunity to millions of antigens, Allergic reactions The epidermis constitutes the barrier between the moist are abnormally powerful immune responses to an anti- nvironment of the living cells of the body and the dry gen that usually poses no threat to the body atmosphere of the external environment The dermis contains tiny sweat glands that have little canals or ducts, leading to the surface. Hairs grow from Movement follicles in the dermis. The layers of the skin form a barrier Movement of the whole body or parts of it are essential avoiding injury ■ dehydration ■ reproduction Sensory nerve endings present in the dermis are Most body movement is under conscious (voluntar stimulated by pain, temperature and touch. If the control. The exceptions include protective movements finger touches a very hot plate, it is removed immedi- which are carried out before the individual is aware of ately. This cycle of events is called a reflex action and is a them, e.g. the reflex action of removing the finger from a very rapid motor response(contraction of muscles)to a very hot surface sensory stimulus(stimulation of sensory nerve endings The skeleton provides the bony framework of the in the skin). This type of reflex action is an important body and movement takes place at joints between two or protective mechanism that is mediated by the nervous more bones. Skeletal muscles(Fig. 1.14)move the joints and they are stimulated to contract by the nervous sys- The skin also plays an important role in the regulation tem. a brief description of the skeleton is given in of body temperature Chapter 3, and a more detailed account of bones, muscles and joints is presented in Chapters 16, 17 and 18 Resistance and immunity The body has many means of self-protection from invaders( Ch. 15). They are divided into two categories specific and nonspecific defence mechanisms. Nonspecific defence mechanisms These are effective against any invaders. The protection provided by the skin is outlined above. In addition there are other protective features at body surfaces, e.g. mucus Skeletal muscles secreted by mucous membranes traps microbes and other foreign materials on its sticky surface. Some body fluids contain antimicrobial substances, e. g. gastric juice ntains hydrochloric acid, which kills most ingested Tendon microbes. Following successful invasion other non- specific processes may occur including the inflammatory response, which is also involved in tissue healing Specific defence mechanisms The body generates a specific(immune)response against any substance it identifies as foreign. Such substances are bacteria and other microbes cancer cells or transplanted tissue cells pollen from flowers and plants Figure 1.14 The skeletal muscles
Introduction to the human body The epidermis lies superficially and is composed of several layers of cells that grow towards the surface from its deepest layer. The surface layer consists of dead cells that are constantly being rubbed off and replaced from below. The epidermis constitutes the barrier between the moist environment of the living cells of the body and the dry atmosphere of the external environment. The dermis contains tiny sweat glands that have little canals or ducts, leading to the surface. Hairs grow from follicles in the dermis. The layers of the skin form a barrier against: • invasion by microbes • chemicals • dehydration. Sensory nerve endings present in the dermis are stimulated by pain, temperature and touch. If the finger touches a very hot plate, it is removed immediately. This cycle of events is called a reflex action and is a very rapid motor response (contraction of muscles) to a sensory stimulus (stimulation of sensory nerve endings in the skin). This type of reflex action is an important protective mechanism that is mediated by the nervous system. The skin also plays an important role in the regulation of body temperature. Resistance and immunity The body has many means of self-protection from invaders (Ch. 15). They are divided into two categories: specific and nonspecific defence mechanisms. Nonspecific defence mechanisms These are effective against any invaders. The protection provided by the skin is outlined above. In addition there are other protective features at body surfaces, e.g. mucus secreted by mucous membranes traps microbes and other foreign materials on its sticky surface. Some body fluids contain antimicrobial substances, e.g. gastric juice contains hydrochloric acid, which kills most ingested microbes. Following successful invasion other nonspecific processes may occur including the inflammatory response, which is also involved in tissue healing. Specific defence mechanisms The body generates a specific (immune) response against any substance it identifies as foreign. Such substances are called antigens and include: • bacteria and other microbes • cancer cells or transplanted tissue cells • pollen from flowers and plants. Following exposure to an antigen, lifelong immunity against further invasion by the same antigen usually develops. Over a lifetime, an individual gradually builds up immunity to millions of antigens. Allergic reactions are abnormally powerful immune responses to an antigen that usually poses no threat to the body. Movement Movement of the whole body or parts of it are essential for: • obtaining food • avoiding injury • reproduction. Most body movement is under conscious (voluntary) control. The exceptions include protective movements which are carried out before the individual is aware of them, e.g. the reflex action of removing the finger from a very hot surface. The skeleton provides the bony framework of the body and movement takes place at joints between two or more bones. Skeletal muscles (Fig. 1.14) move the joints and they are stimulated to contract by the nervous system. A brief description of the skeleton is given in Chapter 3, and a more detailed account of bones, muscles and joints is presented in Chapters 16,17 and 18. 13 Figure 1.14 The skeletal muscles
The body and its constituents Reproduction( Ch. 19) When the ovum is not fertilised it passes out of the uterus Successful reproduction is essential in order to ensure th accompanied by bleeding, called menstruation. The cycle in the female, called the menstrual cycle, has phases ontinuation of a species from one generation to the next. ciated with changes in the concentration of hormones Bisexual reproduction results from the fertilisation of a involving the endocrine system. There is no similar cycle female egg cell or ovum by a male sperm cell or spermato- in the male but hormones similar to those of the female zoon. Ova are produced by twe ovaries situated in the are involved in the production and maturation of the female pelvis(Fig. 1. 15). Usually only one ovum released at a time and it travels towards the uterus in the spermatozoa. uterine tube. The spermatozoa are produced in large num- bers by the two testes, situated in the scrotum. From each testis spermatozoa pass through a duct called the deferent INTRODUCTION TO THE STUDY duct (vas deferens) to the urethra. During sexual inter course (coitus) the spermatozoa are deposite OF ILLNESS They then pass upwards through the uterus and fer ilise the ovum in the uterine tube. The fertilised ovum zygote) then passes into the uterus, embeds itself in the Learning outcomes terine wall and grows to maturity during pregnancy After studying this section you should be able to gestation, in about 40 weeks. The newborn baby is entirely dependent on others for food and protection tha a list factors that commonly cause disease was provided by the mother's body before birth. a define the following terms: aetiology, pathogenesis One ovum is produced about every 28 days during the child-bearing years between puberty and the menopause m name some common disease processes that can affect many of the body systems 14 In order to understand the specific diseases described in later chapters, a knowledge of the relevant anatomy and physiology is necessary, as well as familiarity with the pathological processes outlined below known, and these vary from ut often very some conditions, to the very serious. The study of abnor malities can be made much easier when a systemati approach is adopted. In order to achieve this in later chap- ters where specific diseases are explained, the headings Deferent duct Uterine tube shown in Box 1. 3 will be used as a guide. Causes(aetiology are outlined first when there are clear links between them Prostate gland Ovary Utery and the effects of the abnormality (pathogenesis) Penis Vagina Box 1.3 Suggested framework for understanding diseases Aetiology: cause of the disease Pathogenesis: the nature of the disease process and its effect on normal body functioning Complications: other consequences which might arise if the disease progresses Prognosis: the likely outcome Figure 1.15 The reproductive systems: male and female
The body and its constituents 14 Reproduction (Ch. 19) Successful reproduction is essential in order to ensure the continuation of a species from one generation to the next. Bisexual reproduction results from the fertilisation of a female egg cell or ovum by a male sperm cell or spermatozoon. Ova are produced by two ovaries situated in the female pelvis (Fig. 1.15). Usually only one ovum is released at a time and it travels towards the uterus in the uterine tube. The spermatozoa are produced in large numbers by the two testes, situated in the scrotum. From each testis spermatozoa pass through a duct called the deferent duct (vas deferens) to the urethra. During sexual intercourse (coitus) the spermatozoa are deposited in the female vagina. They then pass upwards through the uterus and fertilise the ovum in the uterine tube. The fertilised ovum (zygote] then passes into the uterus, embeds itself in the uterine wall and grows to maturity during pregnancy or gestation, in about 40 weeks. The newborn baby is entirely dependent on others for food and protection that was provided by the mother's body before birth. One ovum is produced about every 28 days during the child-bearing years between puberty and the menopause. When the ovum is not fertilised it passes out of the uterus accompanied by bleeding, called menstruation. The cycle in the female, called the menstrual cycle, has phases associated with changes in the concentration of hormones involving the endocrine system. There is no similar cycle in the male but hormones similar to those of the female are involved in the production and maturation of the spermatozoa. INTRODUCTION TO THE STUDY OF ILLNESS Learning outcomes After studying this section you should be able to: • list factors that commonly cause disease • define the following terms: aetiology, pathogenesis and prognosis • name some common disease processes that can affect many of the body systems. In order to understand the specific diseases described in later chapters, a knowledge of the relevant anatomy and physiology is necessary, as well as familiarity with the pathological processes outlined below. Many different illnesses, disorders and diseases are known, and these vary from minor, but often very troublesome conditions, to the very serious. The study of abnormalities can be made much easier when a systematic approach is adopted. In order to achieve this in later chapters where specific diseases are explained, the headings shown in Box 1.3 will be used as a guide. Causes (aetiology) are outlined first when there are clear links between them and the effects of the abnormality (pathogenesis}. Figure 1.15 The reproductive systems: male and female. Box 1.3 Suggested framework for understanding diseases Aetiology: cause of the disease Pathogenesis: the nature of the disease process and its effect on normal body functioning Complications: other consequences which might arise if the disease progresses Progenosis: the likely outcomeBox
Introduction to the human body Aetiology a Abnormal immune mechanisms(p. 383)-these are a response of the normally protective immune system ed by one or more of a limited that causes undesirable effects number of factors including a Thrombosis, embolism and infarction(p. 117)-these are genetic abnormalities, either inherited or acquire the effects and consequences of abnormal changes in infection by microbes or parasites, e.g. viruses, the blood and/or blood vessel walls bacteria or worms m Degeneration-this is often associated with normal ■ chemical ageing but also arises prematurely when structures ionising radiation deteriorate causing impaired function physic a Metabolic abnormalities-cause undesirable effects (e. g degeneration, e. g. excessive use or ageing henylketonuria(p, 185)) u Genetic abnormalities-may be either inherited or In some diseases more than one of the aetiological factors caused by environmental factors such as exposure to listed above is involved, while in others, no specific cause as been identified and these may be described as essen tial, idiopathic or spontaneous. For some diseases of which Box 1. 4 is a glossary of disease-associated terminology the precise cause is unknown, links may have been estab- lished with predisposing factors, or risk factors. jatrogeni conditions are those that result from harm caused by Box 1. 4 Glossary of terminology associated with disease members of the caring professions Acute: a disease with sudden onset often requiring Pathogenesis Acquired: a disorder which develops any time after The main processes causing illness or disease are as follows Chronic: a long-standing disorder which cannot a Inflammation(p. 375)this is a tissue response to usually be cured(compare with acute damage by, e.g. trauma, invasion of microbes Congenital: a disorder which one is born with nflammatory conditions are recognised by the suffix (compare with acquired -itis, e. g appendicitis Sign: an abnormality seen or measured by people a Tumours(p. 53)-these arise when the rate of cell other than the patient production exceeds that of normal cell destruction causing a mass to develop Tumours are recognised Symptom: an abnormality described by the patient by the suffix-oma, e. g carcinoma Syndrome: a collection of signs and symptoms which tend to occur together "The term microbe, used throughout the text, includes all types of organisms that can only be seen by using a microscop Specific microbes are named where appropriate
Introduction to the human body Aetiology Disease is usually caused by one or more of a limited number of factors including: • genetic abnormalities, either inherited or acquired • infection by microbes or parasites, e.g. viruses, bacteria or worms • chemicals • ionising radiation • physical trauma • degeneration, e.g. excessive use or ageing. In some diseases more than one of the aetiological factors listed above is involved, while in others, no specific cause has been identified and these may be described as essential, idiopathic or spontaneous. For some diseases of which the precise cause is unknown, links may have been established with predisposing factors, or risk factors. latrogenic conditions are those that result from harm caused by members of the caring professions. Pathogenesis The main processes causing illness or disease are as follows. • Inflammation (p. 375) — this is a tissuhe response to damage by, e.g. trauma, invasion of microbes*. Inflammatory conditions are recognised by the suffix -itis, e.g. appendicitis. • Tumours (p. 53) — these arise when the rate of cell production exceeds that of normal cell destruction causing a mass to develop. Tumours are recognised by the suffix -oma, e.g. carcinoma. Abnormal immune mechanisms (p. 383) —these are a response of the normally protective immune system that causes undesirable effects. Thrombosis, embolism and infarction (p. 117) —these are the effects and consequences of abnormal changes in the blood and/or blood vessel walls. Degeneration — this is often associated with normal ageing but also arises prematurely when structures deteriorate causing impaired function. Metabolic abnormalities —cause undesirable effects (e.g. phenylketonuria (p. 185)). Genetic abnormalities — may be either inherited or caused by environmental factors such as exposure to ionising radiation. Box 1.4 is a glossary of disease-associated terminology. 15 *The term microbe, used throughout the text, includes all types of organisms that can only be seen by using a microscope. Specific microbes are named where appropriate. Box 1.4 Glossary of terminology associated with disease Acute: a disease with sudden onset often requiring urgent treatment (compare with chronic). Acquired: a disorder which develops any time after birth (compare with congenital). Chronic: a long-standing disorder which cannot usually be cured (compare with acute). Congenital: a disorder which one is born with (compare with acquired). Sign: an abnormality seen or measured by people other than the patient Symptom: an abnormality described by the patient. Syndrome: a collection of signs and symptoms which tend to occur together