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JUST THE FACTS HUMAN BODY A fact-by-fact look at the human body, from the skin deep to the vital organs that keep us alive. • Information on each part of the body. • Charts and diagrams. • Full-color photographs and illustrations. The most up-to-date information available, presented in a unique easy-reference system of lists, fact boxes, tables, and charts. Find the fact you need in seconds with JUST THE FACTS! INFORMATION AT YOUR FINGERTIPS INFORMATION AT YOUR FINGERTIPS INFORMATION AT YOUR FINGERTIPS Visit our Web site at: US $9.95 CAN $15.95 www.SchoolSpecialtyPublishing.com ISBN 0-7696-4255-1 UPC EAN INFORMATION AT YOUR FINGERTIPS INFORMATION AT YOUR FINGERTIPS INFORMATION AT YOUR FINGERTIPS School Specialty Publishing ® INFORMATION AT YOUR FINGERTIPS HUMAN BODY This edition published in the United States in 2006 by School Specialty Publishing, a member of the School Specialty Family. Copyright © ticktock Entertainment Ltd 2005 First published in Great Britain in 2005 by ticktock Media Ltd. Printed in China. All rights reserved. No part of this book may be reproduced, stored in a central retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, withouth the prior written permission of the publisher. Written by Steve Parker. Library of Congress-in-Publication Data is on file with the publisher. Send all inquiries to: School Specialty Publishing 8720 Orion Place Columbus, OH 43240-2111 ISBN 0-7696- 4255-1 1 2 3 4 5 6 7 8 9 10 TTM 11 10 09 08 07 06 2 CONTENTS HOW TO USE THIS BOOK ....................................................................................4 BODY SYSTEMS ................................................................................................................6 • Integumentary • Muscular • Skeletal • Nervous • Sensory • Respiratory • Circulatory • Digestive • Urinary • Reproductive • Hormonal • Lymphatic • Immune THE SKIN ..................................................................................................................................8 • Sense of touch • Fingertips • Sweat • Layers of the skin • Microsensors • Shed skin • Skin thickness • Main tasks of the skin • Size of the skin HAIR AND NAILS ....................................................................................10 • Nail parts • Growth of nails • Hair thickness • Structure of a hair • Eyebrows • Eyelashes • Growth of hair • Hair life cycle • Why have hair? • Why have nails? MUSCLES & MOVEMENT ...................................................................................12 • Types of muscle • Muscle used for facial expressions • Inside a muscle • Power of muscles • How muscles work • Muscle records THE SKELETON ...............................................................................................................14 • Size and variation • The coccyx • Cartilage • Bone strength • Tasks of the skeleton • Number of bones BONES AND JOINTS ...............................................................................................16 • Parts of a bone • What a bone contains • Bone records • Ligaments • Synovial fluid • The knee joint • Different types of joint • Head movements THE NERVOUS SYSTEM ......................................................................................18 • Parts of the nervous system • Nerve cells • Nerve signals • Spinal cord • Nerve lengths THE BRAIN..........................................................................................................................20 • The cortex • Energy requirements • Blood supply to the brain • Brain parts • Size of the brain • Sleep • Left and right • Brain development through life CIRCULATORY SYSTEM .......................................................................................34 • Veins and arteries • Using oxygen • Types of blood vessels • Size and length of blood vessels • Journey times of blood • Blood pressure in blood vessels BLOOD .....................................................................................................................................36 • Blood flow • Amount of blood in the body • Blood types • Red blood cells • What is in blood? DIGESTION..........................................................................................................................38 • The digestive tract • Digestive juices • Length of food’s journey • Faeces • Stomach • Appendix • Small intestine • Large intestine FOOD AND NUTRIENTS ......................................................................................40 • Food groups • Daily needs • Carbohydrates • Fats and oils • Proteins • Fiber • Fruit and vegetables • Vitamins • Minerals LIVER AND PANCREAS ........................................................................................42 • Tasks of the liver • Gall bladder • Bile • Blood supply to the liver • Liver of young children • Jaundice • Shape of the liver • Shape of the pancreas KIDNEYS AND URINARY SYSTEM .........................................................44 • Size and shape of kidneys • Parts of the kidney • Nephrons • Urinary parts • Size of the bladder • Male and female systems • Filtering the blood GENES .......................................................................................................................................46 • DNA • Chromosomes • Genes • Inherited characteristics • Genetic fingerprinting • Clones REPRODUCTION ..................................................................48 • Size and shape of female reproductive parts • Female parts • Egg release cycle • Eggs and sperm • Male parts • Size and shape of male reproductive parts STAGES OF LIFE .....................................................50 EYES AND SIGHT ........................................................................................................22 • Parts of the eye • How the eye sees • Cones • Blind spot • Moving the eye • Blinking • Growth rates • How an egg is fertilized • Embryo • Fetus • New baby • Puberty • Aging EARS AND HEARING ..............................................................................................24 • How we hear • Sections of the ear • Bones in the ear • Pitch • Sense of balance • Stereo hearing • Ear measurements • The loudness of sounds HORMONES ............................................................52 • Thyroid • Parathyroid • Pituitary • Pancreas • Thymus • Adrenals • Adrenaline • Other hormone making parts NOSE AND TONGUE ................................................................................................26 • How we smell • Parts of the nose • Parts of the tongue • How we taste • Other tasks of the tongue TEETH AND JAW ..........................................................................................................28 • Numbers of teeth • Parts of a tooth • Plaque • When teeth grow • Chewing • Roof of the mouth • Saliva LUNGS AND BREATHING ..................................................................................30 • Size and shape of the lungs • Gases used • Breathing rates • Parts of the lungs • The voicebox • Speech THE HEART .........................................................................................................................32 • Parts of the heart • Heart’s blood supply • Heart’s job • The pulse • Changing pulse rate through life • How the heart works • Size and shape • Typical day LYMPH AND IMMUNE SYSTEMS ................................................................54 • Lymph nodes • Lymph fluid • Lymphocytes • How the immune system works • Types of immunity DISEASES AND MEDICINES .......................56 • Types of medicines • Medical drugs • Causes of illness and disease • Bacteria • Viruses • Protists • Microfungi • Medical specialists GLOSSARY ....................................................................58 INDEX .................................................................................60 3 HOW TO USE THIS BOOK J UST THE FACTS, HUMAN BODY is a quick and easy-to-use way to look up facts about the systems that control how our bodies work. Every page is packed with cut-away diagrams, charts, scientific terms and key pieces of information. For fast access to just the facts, follow the tips on these pages. WHERE IN THE BODY? An at-a-glance look at where the part of the body can be found. TWO QUICK WAYS TO FIND A FACT: 1 Y our body can’t digest food with just its digestive tract (passageway) – mouth, gullet, stomach and intestines. Also needed are two parts called the liver and pancreas. These are next to the stomach and they are digestive glands, which means they make powerful substances to break down food in the intestines. Together with the digestive tract, the liver and pancreas make up the whole digestive system. FOOD & NUTRIENTS ....................................................................................40-41 • Food groups • Daily needs • Carbohydrates • Fats and oils • Proteins • Fibre • Fruit and vegetables • Vitamins • Minerals CONTENTS HOW TO USE THIS BOOK ............................................................................4–5 THE SKIN ...........................................................................................................................8–9 • Sense of touch • Fingertips • Sweat • Layers of the skin • Microsensors • Shed skin • Skin thickness • Main tasks of the skin • Size of the skin HAIR AND NAILS ...........................................................................10–11 • Nail parts • Growth of nails • Hair thickness • Structure of a hair • Eyebrows • Eyelashes • Growth of hair • Hair life cycle • Why have hair? • Why have nails? MUSCLES & MOVEMENT ........................................................................12-13 • Types of muscle • Muscle used for facial expressions • Inside a muscle • Power of muscles • How muscles work • Muscle records THE SKELETON .....................................................................................................14-15 • Size and variation • The coccyx • Cartilage • Bone strength • Tasks of the skeleton • Number of bones BONES AND JOINTS .....................................................................................16-17 • Parts of a bone • What a bone contains • Bone records • Ligaments • Synovial fluid • The knee joint • Different types of joint • Head movements THE NERVOUS SYSTEM ............................................................................18-19 • Parts of the nervous system • Nerve cells • Nerve signals • Spinal cord • Nerve lengths THE BRAIN ...............................................................................................................20-21 • The cortex • Energy requirements • Blood supply to the brain • Brain parts • Size of the brain • Sleep • Left and right • Brain development through life CIRCULATORY SYSTEM .............................................................................34-35 • Veins and arteries • Using oxygen • Types of blood vessels • Size and length of blood vessels • Journey times of blood • Blood pressure in blood vessels DIGESTION ...............................................................................................................38-39 • The digestive tract • Digestive juices • Length of food’s journey • Faeces • Stomach • Appendix • Small intestine • Large intestine FOOD & NUTRIENTS ....................................................................................40-41 • Food groups • Daily needs • Carbohydrates • Fats and oils • Proteins • Fibre • Fruit and vegetables • Vitamins • Minerals KIDNEYS & URINARY SYSTEM .......................................................44-45 • Size and shape of kidneys • Parts of the kidney • Nephrons • Urinary parts • Size of the bladder • Male and female systems • Filtering the blood STAGES OF LIFE...........................................50-51 • Growth rates • How an egg is fertilized • Embryo • Fetus • New baby • Puberty • Ageing HORMONES ..................................................52-53 • Thyroid • Parathyroid • Pituitary • Pancreas • Thymus • Adrenals • Adrenaline • Other hormone making parts LUNGS & BREATHING ...............................................................................30–31 • Size and shape of the lungs • Gases used • Breathing rates • Parts of the lungs • The voicebox • Speech THE HEART ..............................................................................................................32–33 • Parts of the heart • Heart’s blood supply • Heart’s job • The pulse • Changing pulse rate through life • How the heart works • Size and shape • Typical day KIDNEYS & URINARY SYSTEM .......................................................44-45 • Size and shape of kidneys • Parts of the kidney • Nephrons • Urinary parts • Size of the bladder • Male and female systems • Filtering the blood GENETICS ...................................................................................................................46-47 • DNA • Chromosomes • Genes • Inherited characteristics • Genetic fingerprinting • Clones EARS & HEARING ............................................................................................24-25 • How we hear • Sections of the ear • Bones in the ear • Pitch • Sense of balance • Stereo hearing • Ear measurements • The loudness of sounds TEETH & JAW ........................................................................................................28-29 • Numbers of teeth • Parts of a tooth • Plaque • When teeth grow • Chewing • Roof of the mouth • Saliva The liver is in the upper abdomen, behind the lower right ribs. The pancreas is in the upper left abdomen, behind the stomach. LIVER AND PANCREAS ..............................................................................42-43 • Tasks of the liver • Gall bladder • Bile • Blood supply to the liver • Liver of young children • Jaundice • Shape of the liver • Shape of the pancreas EYES AND SIGHT ..............................................................................................22-23 • Parts of the eye • How the eye sees • Cones • Blind spot • Moving the eye • Blinking NOSE & TONGUE ..............................................................................................26-27 • How we smell • Parts of the nose • Parts of the tongue • How we taste • Other tasks of the tongue WARM LIVER LIVER AND PANCREAS ..............................................................................42-43 • Tasks of the liver • Gall bladder • Bile • Blood supply to the liver • Liver of young children • Jaundice • Shape of the liver • Shape of the pancreas BLOOD ...........................................................................................................................36-37 • Blood flow • Amount of blood in the body • Blood groups • Red blood cells • What is in blood? REPRODUCTION .......................................................48-49 • Size and shape of female reproductive parts • Female parts • Egg release cycle • Eggs and sperm • Male parts • Size and shape of male reproductive parts LYMPH & IMMUNE SYSTEMS ......................................................54-55 • Lymph nodes • Lymph fluid • Lymphocytes • How the immune system works • Types of immunity DISEASES & MEDICINES ...................56–57 • Types of medicines • Medical drugs • Causes of illness and disease • Bacteria • Viruses • Protists • Micro-fungi • Medical specialists GLOSSARY ..........................................................58-59 INDEX ......................................................................60–64 GENETICS ...................................................................................................................46-47 • DNA • Chromosomes • Genes • Inherited characteristics • Genetic fingerprinting • Clones REPRODUCTION .......................................................48-49 3 • Size and shape of female reproductive parts • Female parts • Egg release cycle • Eggs and sperm • Male parts • Size and shape of male reproductive parts The liver has more than 500 known tasks in the body – and probably more that haven’t yet been discovered. Some of the main ones are: Turn to the INDEX that starts on page 60 and search for key words relating to your research. • The index will direct you to the correct page, and where on the page to find the fact you need. 60 4 C) 40b, 41d asthma 56b astigmatism 23c atlas vertebra 16c-d atria, heart 33a-c, 33d atriopeptin 53a-c auditory nerve 25a-c auricle (pinna) 24a auricularis muscle 12a-d autoimmune problems 56c-d autonomic nerve system 18b axillary hair 10b-d axis 16c-d axons 18c-d, 19a-b, 19c, 20b-c B babies 14b-c, 15a-b, 50-1 bacilli 57a backbone 15d bacteria 6-7c, 45a-c, 55ab, 55c, 56b, 57a bacterial infections 57a balance 6-7c, 24a-d ball-and-socket joint 17d beta-blocker 56a bile 42a-c, 42d, 43a bladder 44b-d, 45a-c blastocyst 50b-d blinking 23c blood 15a-c, 16a, 34b-d, 36-7, 40a, 45d clotting 6-7b, 36c-d, 37d, 40a, 56a, 56b blood groups 36c-d blood pressure 21a-c, 35ac, 40c-d, 53a-c, 56a blood sugar (glucose) 12a, 20a, 30b-d, 37d, 40c-d, 42a-c, 53 blood transfusions 36c-d blood vessels 34a, 34b-d, 36b-d, 53d, 56a body salts 37d, 53a-c body systems 6-7 see also named systems bone marrow 15a-c, 16a, 37a-c bones 6-7a, 16-17, 40a, 41a see also named bones bowel motions 6-7c, 39b-c Bowman’s capsule 44a-d brain 6-7a, 18a, 18b-d, 20-1, 24c-d, 37a-b, 52b-d breastbone 15d breathing 21a-c, 30-1, 40c-d, 53d bronchi 31a-c bronchioles 31a-c, 56a bronchodilator 56a buccinator muscle 12a-d The letters a, b, c, d, following the page number indicate the column (lettering from left to right) in which the information may be found on that page. C caecum 39d calcaneal (Achilles) tendon 13d calciferol (Vitamin D) 9d, 41d calcitonin 52a calcium 15a-c, 16b-d, 40a, 40b, 41c, 52a, 52b calcium carbonate 16b-d calcium phosphate 16b-d cancers 56c-d capillaries 35a-c, 35d, 36a carbohydrates 40, 43a carbon dioxide 6-7a, 31a-c, 37d carbonate 16b-d cardiac muscle (myocardium) 12b-d, 32c-d, 33a-c cardiologist 57d cardiovascular system 6-7b, 34-5 carotene (Vitamin A) 41d carotid artery 20a cartilage 15a-b, 17a-c, 17d cells 6-7a, 40, 49a-c, 50b-d see also named types of cell cellulose 40b-d cerebellum 21a-c cerebral cortex 20b-c, 21a-c cerebral vessels 35a-c cerebrospinal fluid (CSF) 19a-b, 21a-b cerebrum 21a-c cervical vertebrae 15d, 16c-d cervix 48b, 48c-d chemosenses 26b-d chemotherapy 56a chewing 29d chloride 40b A abdomen 43b-c accidents 56c-d Achilles (calcaneal) tendon 13d acids 39a-c acquired immunity 55d actin 13a-c active immunity 55d GALL BLADDER AND BILE liver • The heat from the liver isn’t wasted. The blood spreads out the heat all around the body. See pages 34-35 for information on the circulatory system. ‘Adam’s apple’ 31d adenine 46a adenoids (pharyngeal tonsils) 54a, 54c-d adrenal glands 53c, 53d adrenaline (epinephrine) 36b, 52b-d, 53c, 53d ageing 51d alcohol 21d, 42a-c aldosterone 53c alleles 47a-c allergies 56b, 56c-d alveoli 31a-c amino acids 41a ammonia 44a-d amniotic fluid 50a-d anaesthetics 56a, 57d anaesthetist 57d • If levels of blood sugar (glucose) are too high, hormones from the pancreas tell the liver to change the glucose into glycogen and store it. • If levels of blood sugar (glucose) are too low, hormones from the pancreas tell the liver to release the glycogen it has stored. • Breaking down nutrients and other substances from digestion, brought direct to the liver from the small intestine. IND INDEX ‘Adam’s apple’ 31d adenine 46a adenoids (pharyngeal tonsils) 54a, 54c-d adrenal glands 53c, 53d adrenaline (epinephrine) 36b, 52b-d, 53c, 53d ageing 51d alcohol 21d, 42a-c aldosterone 53c alleles 47a-c allergies 56b, 56c-d alveoli 31a-c amino acids 41a ammonia 44a-d amniotic fluid 50a-d anaesthetics 56a, 57d anaesthetist 57d analgesics 56a ankles 15d anti-emetics 56b anti-inflammatories 56b antibiotic drugs 56b, 57a antibodies 37d, 54b, 55a-c, 55d anticoagluants 56b anticonvulsants 56b antidepressants 56b antidiuretic hormone (ADH) 52c-d antifungal 56b antigens 55a-c, 55d antihistamine 56b antipyretic 56b antiseptic 56b antitoxin 56b antiviral 56b anus 6-7c, 38a, 39a-c anvil bone (incus) 24a aorta 33d, 34a-b, 34c-d aortic valve 33a-c, 33d appendix 38a, 39d aqueous humour 23a-c arms 15d arteries 20a, 33a-c, 34, 35, 36a, 43b-c, 44b-d arterioles 35a-c, 35d, 36b artificial acquired immunity 55d ascorbic acid (Vitamin • When the body is at rest and the muscles are still, the liver makes up to one-fifth of the body’s total warmth. pancreas 2 The letters a, b, c, d, following the page number indicate the column (lettering from left to right) in which the information may be found on that page. The liver is so busy with chemical processes and tasks that it makes lots of heat. THE LIVER’S TASKS Turn to the relevant page and use the BOX HEADINGS to find the information box you need. A abdomen 43b-c accidents 56c-d Achilles (calcaneal) tendon 13d acids 39a-c acquired immunity 55d actin 13a-c active immunity 55d LIVER & PANCREAS WHERE IN THE BODY? Look at the detailed CONTENTS list on page 3 to find your • The digestive tract • Digestive juices • Length of food’s journey • Faeces • Stomach topic of interest. • Appendix • Small intestine • Large intestine BODY SYSTEMS ........................................................................................................6–7 • Integumentary • Skeletal • Muscular • Nervous • Sensory Respiratory • Circulatory • Digestive • Urinary • Reproductive Hormonal • Lymphatic • Immune INTRODUCTION TO TOPIC a a a a a a a a a gall bladder The gall bladder is a small storage bag under the liver. • Storing vitamins for times when they may be lacking in food. • It is 8 cm long and 3 cm wide. • Making bile, a digestive juice. • Some of the bile fluid made in the liver is stored in the gall bladder. • Breaking apart old, dead, wornout red blood cells. • The gall bladder can hold up to 50 millilitres of bile. • Breaking down toxins or possibly harmful substances, like alcohol and poisons. • After a meal, bile pours from the liver along the main bile duct (tube), and from the gall bladder along the cystic duct, into the small intestine. • Helping to control the amount of water in blood and body tissues. Alcohol is a toxin which the liver breaks down and makes harmless. Too much alcohol can overload the liver and cause a serious disease called cirrhosis. a ax ax ax • Bile helps to break apart or digest the fats and oils in foods. • The liver makes up to one litre of bile each day. 42 BOX HEADINGS JUST THE FACTS Look for heading words linked to your research to guide you to the right fact box. Each topic box presents the facts you need in short, quick-to-read bullet points. GLOSSARY BODY SYSTEMS INTEGUMENTARY SYSTEM • Skin, hair and nails. • Protect soft inner parts from physical wear and knocks, dirt, water, sun’s rays and other harm. • Skin keeps in essential body fluids, salts and minerals. • Helps to control body temperature by sweating and flushing to lose heat, or going pale with ‘goosebumps’ to retain heat. • Provides sense of touch (see Sensory system). • Gets rid of small amounts of waste substances, in sweat. T he body is often divided into body systems, each one of which performs a certain job. Body systems are made from microscopic ‘building blocks’ called cells. A typical cell is only 0.03 mm across, and there are about 50 million million cells in the body. There are many different kinds of cells, like nerve cells, muscle cells and so on. Many cells of the same kind form a tissue, such as nerve tissue or fat tissue. Different kinds of tissue make up a main part of the body, known as an organ, like the brain, stomach or kidney. Several organs working together to carry out one major task or function, like digesting food, are known as a body system. About a dozen major systems make up the whole human body. MUSCULAR SYSTEM • About 640 skeletal muscles all over the body, mostly attached to bones (skeletal or voluntary muscle). • Muscle layers in the walls of inner parts like the stomach and intestines (visceral or involuntary muscle). • Muscle in the walls of the heart (heart muscle or myocardium). • Muscles get shorter or contract to produce all forms of bodily movement. • Sometimes combined with bones and joints as the musculoskeletal system. SKELETAL SYSTEM • 208 bones and the various kinds of joints between them. • Gives physical support to hold up the body’s soft, floppy parts. • Gives protection to certain body parts like the brain, eyes, heart, lungs. • Pulled by muscles, to allow movement. • Acts as a store or reservoir of valuable minerals like calcium, in case these are in short supply in food. • Sometimes combined with muscles as the musculoskeletal system. SENSORY SYSTEM RESPIRATORY SYSTEM • Eyes, ears, nose, tongue and skin make up the five main sets of sense organs. • Also sensors inside the body for temperature, blood pressure, oxygen levels, positions of joints, amount of stretch in muscles and many other changes. • Gravity and motion sensors in the inner ear contribute to the process of balance. • Sometimes included as part of the nervous system, since the main sense organs are in effect the specialized endings of sensory nerves. • Nose, windpipe, main chest airways and lungs. • Obtains essential oxygen from the air around, and passes it to the blood for distribution. • Gets rid of waste carbon dioxide, which would be poisonous if it built up in the blood. • Useful ‘extra function’ is the ability to make vocal sounds and speech. CIRCULATORY (CARDIOVASCULAR) SYSTEM DIGESTIVE SYSTEM • Mouth, teeth, throat, gullet, stomach, intestines, rectum and anus make up the digestive passageway or tract. • Liver, gall bladder and pancreas plus the tract make up the whole digestive system. • Breaks down or digests food into nutrients tiny enough to take into the body. • Gets rid of leftovers as solid wastes (bowel motions, faeces). • Nutrients provide energy for all life processes and raw materials for growth, maintenance and repairing everyday wearand-tear. NERVOUS SYSTEM Artery A blood vessel (tube) which conveys blood away from the heart. Axon The very long, thin part of a nerve cell or neuron, also called a nerve fibre. URINARY SYSTEM Bladder Bag-like sac or container for storing fluids. The body has several, including the urinary bladder (often just called ‘the bladder’) and gall bladder. Blood sugar Also called glucose, the body’s main energy source, used by all its microscopic cells to carry out their life processes and functions. Fovea The small area in the retina of the eye where vision is most detailed and clearest, due to the great number of cone cells. Cardiac To do with the heart. Cranium The upper domed part of the skull or ‘brain case’, which covers and protects the brain. Gastric To do with the stomach. Cartilage Tough, light, slightly bendy and compressible body substance, often called ‘gristle’, which forms parts of the skeleton such as the ears and nose, and also covers the ends of bones in joints. Cell The basic microscopic ‘building block’ of the body, a single living unit, with most cells being 0.01-0.05 mm across. The body contains over 50 million million cells. Central nervous system The brain and spinal cord. Cilium Microscopic hair, usually sticking out from the surface of a cell, which can wave or bend, and perhaps sense substances as in the olfactory epithelium of the nose and in the taste buds on the tongue. (Plural: cilia.) • Defends the body against invading dangers such as bacteria, viruses and other microbes. • Gets rid of debris in tissues from normal wear-and-tear. • Helps recovery from disease and illness. • Helps repair of injury and normal wear-and-tear. • Keeps watch for problems and disease processes arising inside the body, such as malignant (cancerous) cells. 6 Cortex The outer part or layer of a body part, such as the renal cortex of the kidney, or the cerebral cortex of the brain. Cerebrospinal fluid Liquid surrounding the brain and spinal cord, to protect and cushion them as well as help provide nourishment and take away wastes. IMMUNE SYSTEM • Lymph vessels, lymph nodes (‘glands’), lymph ducts and lymph fluid. • Gathers general body fluids from between cells and tissues. • One-way flow channels fluid through lymph network of nodes and vessels. • Helps to distribute nutrients and collect wastes. • Lymph fluid empties into blood system. • Closely linked with immune system. Capillary The smallest type of blood vessels, usually less than one millimetre long and too thin to see except through a microscope. Cerebral To do with the cerebrum, the largest part of the brain which forms its wrinkled domed shape. HORMONAL (ENDOCRINE) SYSTEM • About 10 main parts called endocrine or hormonemaking glands. • Some organs with other main tasks, like the stomach and heart, also make hormones. • Hormones spread around the body in blood. • Closely linked to nervous system for coordinated control of inner body processes. • Closely linked with reproductive system and controls it by sex hormones. LYMPHATIC SYSTEM • Brain, spinal cord and peripheral nerves. • Controls and coordinates all body processes, from breathing and heartbeat to making movements. • Allows mental processes such as thoughts, recalling memories and making decisions. • Sensory nerves bring information from the sense organs and other sensors. • Motor nerves carry instructions to muscles about movement, and to glands about releasing their products. • Works along with the hormonal system. Abdomen The lower part of the main body or torso, below the chest, which contains mainly digestive and excretory (waste-disposal) parts, and in females, reproductive parts. • Kidneys, ureters, bladder and urethra. • Filters blood to get rid of unwanted substances and wastes. • Forms unwanted substances and wastes into liquid waste or urine. • Stores urine, then releases it to the outside. • Controls amount and concentration of blood and body fluids, ‘water balance’, by adjusting amount of water lost in urine. REPRODUCTIVE SYSTEM • Only system which differs significantly in females and males. • Only system which is not working at birth, but starts to function at puberty. • Male system produces sperm cells continually, millions per day. • Female system produces ripe egg cells, about one every 28 days, during menstrual cycle. • If egg cell joins sperm cell to form an embryo, female system nourishes this as it grows into a baby inside the womb. GLOSSARY • Heart, blood vessels and blood. • Heart provides pumping power to send blood all around the body. • Blood spreads vital oxygen, nutrients, hormones and many other substances to all body parts. • Blood collects wastes and unwanted substances from all body parts. • Blood clots to seal wounds and cuts. • Closely involved with the immune system in selfdefence and fighting disease. 7 Cermis The inner layer of skin, under the epidermis (see below), which contains the touch sensors, hair follicles and sweat glands. DNA De-oxyribonucleic acid, the chemical substance that forms the genetic information or genes. Embryo The name for a developing human body, from fertilization as a single cell, to eight weeks later. Endocrine To do with hormones and the hormonal system (see hormone). Enzymes Substances which alter the speed of a chemical change or reaction, usually speeding it up, but which remain unchanged themselves at the end of the reaction. Epidermis The protective outer layer of skin, which is always being worn away but continually replacing itself. Excretory To do with removing waste substances from the body. The main excretory system is made up of the kidneys, bladder and their linking tubes. Gland A body part that makes a substance or product which it then releases, such as the tear glands which make tear fluid for the eyes, and the sweat glands in the skin. Glucose See blood sugar. Gustatory To do with the tongue and taste. Hepatic To do with the liver. Hormone A natural ‘chemical messengers’ that circulates in the blood and affects how certain body parts work, helping the nervous system to control and coordinate all body processes. Humour Old word used to describe various body fluids, still used in some cases, for example, to describe the fluids inside the eye, the vitreous (‘glassy’) humour and aqueous (‘watery’) humour. Immunity Protection or resistance to microbial germs and other harmful substances. Integumentary Concerning the skin and other coverings, including nails and hair. Clone A living thing with exactly the same genes as another living thing. Fertilization When an egg cell joins a sperm cell to start the development of a new human body. Ligament A stretchy, straplike part that joins the bones around a joint, so the bones do not move too far apart. Collagen Tiny, tough, strong fibres found in body parts such as skin and bones. Fetus A developing human body from eight weeks after fertilization until birth. Medulla The inner or central region of a body part, such as the renal transfers oxygen from the air around to the blood. medulla of the kidney, or the adrenal medulla of the adrenal gland. Neuron A nerve cell, the basic unit of the nervous system. Meninges Three thin layers covering the brain and spinal cord, and also making and containing cerebrospinal fluid. They are known as the dura mater, arachnoid and pia mater. Olfactory To do with the nose and smell. Optic To do with the eye, especially the optic nerve carrying messages from the eye to the brain. Thoracic To do with the chest, which is also called the thorax. Meiosis Part of special type of cell division, when the chromosomes are not copied and only one set (not a double-set) moves into each resulting cell. Papillae Small lumps, bumps or ‘pimples’ on a body part such as the tongue. Thrombosis The process of blood going lumpy to form a clot, which is also known as a thrombus. Peripheral nerves The bodywide network of nerves, excluding the central nervous system of brain and spinal cord. Tissue A group of very similar cells all doing the same job, such as muscle tissue, adipose or fat tissue, epithelial (covering or lining) tissue, connective tissue (joining and filling in gaps between other parts). Metabolism All of the body’s thousands of chemical processes, changes and reactions, such as breaking apart blood sugar to release energy, and building up amino acids into proteins. Mineral A simple chemical substance, usually a metal such as iron or calcium, or a salt-type chemical such as phosphate, which the body needs in small quantities in food to stay healthy. Mitosis Part of normal cell division, when the chromosomes have been copied and one full doubleset moves into each resulting cell. Motor nerve A nerve that carries messages from the brain to a muscle, telling it when to contract, or to a gland, telling it when to release its content. Mucus Thickish, sticky, slimy substance made by many body parts, often for protection and lubrication, such as inside the nose and within the stomach. Myo- To do with muscles, such as myocardium or heart muscle. Nephron Microscopic filtering unit in the kidney for cleaning the blood. Peristalsis Wave-like contractions of muscles in the wall of a body tube, such as the small intestine, ureter (from kidney to bladder) or oviduct (from ovary to womb). Tendon The string, fibrous, rope-like end of a muscle, where it tapers and joins to a bone. Valve A flap, pocket or similar part which allows a substance to pass one way but not the other. Vein A blood vessel (tube) which conveys blood towards the heart. Vertebra A single bone of the row of bones called the backbone, spine or vertebral column. Villi Tiny finger-like projects from the microscopic cells in various body parts, including the inner lining of the small intestine. Visceral To do with the main parts or organs inside the abdomen (the lower part of the main body or torso), mainly the stomach and intestines, kidneys and bladder, and in females, reproductive parts. Vitamin Substance needed in fairly small amounts in food for the body to work well and stay healthy. Pulmonary To do with the lungs. Renal To do with the kidneys. Sebum Natural waxy-oily substance made in sebaceous glands associated with hair follicles that keeps skin supple and fairly waterproof. Sensory nerve A nerve that carries messages to the brain from a sense organ or part, such as the eye, the ear, the tiny stretch sensors in muscles and joints, and the blood pressure sensors in main arteries. Skeletal To do with the skeleton, the 206 bones that form the body’s supporting inner framework. System In the body, a set of major parts or organs that all work together to fulfil one main task, such as the respiratory system, which 58 6–7 Body Systems 59 58–59 Glossary EXTRA INFORMATION HOW THE PANCREAS WORKS UNUSUAL SUPPLY W H AT I S T H E LIVER? The black box on the right hand side of the page explains a new aspect of the main topic. liver liver Fatty foods, such as chips, are broken apart by enzymes made in the pancreas. The liver is the largest single part or organ inside the body. • Pancreas has two main jobs. • One is to make hormones. • The other is to make digestive chemicals called pancreatic juices. • These juices contain about 15 powerful enzymes that break apart many substances in foods, including proteins, carbohydrates and fats. • Pancreas makes about 1.5 litres of digestive juices daily. • During a meal these pass along the pancreatic duct tubes into the small intestine, to attack and digest foods there. One of the liver’s main functions is to break down nutrients for the body. This means the liver has a unique blood supply. • Most body parts are supplied with blood flowing along one or a few main arteries. • The liver has a main artery, the hepatic artery. • The liver also has a second and much greater blood supply. • The hepatic portal vein is the only main vein that does not take blood straight back to the heart. • Typical weight 1.5 kg. • Depth at widest part on right side 15 cm. • Has a larger right lobe and smaller left lobe. • Lobes separated by a strong layer, the falciform ligament. • It runs from the intestines to the liver, bringing blood full of nutrients from digestion. • This comes along a vessel called the hepatic portal vein. • Wedge-shaped, dark red in colour. W H A T I S T H E PANCREAS? A yellowish tinge to the skin and eyes is known as jaundice, and it is often a sign of liver trouble. Usually the liver breaks down old red blood cells and gets rid of the colouring substance in bile fluid. If something goes wrong the colouring substance builds up in blood and skin and causes jaundice. Hepatitis, an infection of the liver, can cause jaundice. • See pages 36–37 for information on the blood. CUTAWAY DIAGRAMS Most babies and young children have big tummies (abdomens). This is partly because their liver is much larger, in proportion to the body’s overall size, than the liver of an adult. WHEN THINGS GO WRONG Look for the purple links throughout the book. Each link gives details of other pages where related or additional facts can be found. • See pages 36-37 for information on the blood. BABY LIVER • See page 52 for information on hormones. LINKS • An adult liver is usually of total body weight. 1 • A baby’s liver is nearer of total body weight. 1 ⁄40th ⁄20th By the time a baby becomes a toddler, their liver isn’t such a large proportion of their total body weight. Clear, accurate diagrams show how the parts of the body fit together. pancreas The pancreas is a long, slim, wedge- or triangularshaped part. • It is soft, greyish-pink in colour. • Typical weight 0.1 kg. • Typical length 15 cm. • Has three main parts: head (wide end), body (middle) and tail (tapering end). 43 GLOSSARY • A GLOSSARY of words and terms used in this book begins on page 58. • The glossary words provide additional information to supplement the facts on the main pages. PICTURE CAPTIONS Captions explain what is in the pictures. 5 BODY SYSTEMS INTEGUMENTARY SYSTEM • The skin, hair, and nails. • Protects internal organs from physical wear, dirt, water, sun’s rays, and harm. • Skin keeps in essential body fluids, salts and minerals. • Helps to control body temperature by sweating and flushing to lose heat, or going pale with goosebumps to retain heat. • Provides sense of touch (see Sensory System). • Gets rid of small amounts of waste substances in sweat. T he body is often divided into body systems. Each system, though performing specific jobs, works together with the other systems. Body systems are made from microscopic building blocks, called cells. A typical cell is only 0.011 inches across. There are about 10 trillion cells in the body. There are many different kinds of cells, such as nerve cells and muscle cells. Many cells of the same kind form tissue, such as nerve and muscle tissue. Two or more different kinds of tissue create an organ, like the brain, stomach, or kidney. Several organs working together to carry out one major function, such as digesting food, are known as a body system. MUSCULAR SYSTEM • About 640 skeletal muscles all over the body, mostly attached to bones (skeletal or voluntary muscle). • Muscle layers in the walls of inner parts like the stomach and intestines (visceral or involuntary muscle). • Muscle in the walls of the heart (heart muscle or myocardium). • Muscles contract to produce all forms of bodily movement. • Sometimes combined with bones and joints as the musculoskeletal system. SKELETAL SYSTEM • 208 bones and the various kinds of joints between them. • Gives physical support to hold up the body’s soft, floppy parts. • Gives protection to certain body parts like the brain, eyes, heart, lungs. • Pulled by muscles, to allow movement. • Acts as a store or reservoir of valuable minerals like calcium, in case these are in short supply in food. • Sometimes combined with muscles as the musculoskeletal system. NERVOUS SYSTEM • The brain, spinal cord, and peripheral nerves. • Controls and coordinates all body processes, from breathing and heartbeat, to making movements. • Allows mental processes, such as thoughts, recalling memories, and making decisions. • Sensory nerves bring information from the sense organs and other sensors. • Motor nerves carry instructions to muscles about movement and to glands about releasing their products. • Works with the hormonal system. 6 SENSORY SYSTEM RESPIRATORY SYSTEM • The eyes, ears, nose, tongue, and skin make up the five main sets of sensory organs. • Sensors inside the body monitor for temperature, blood pressure, oxygen levels, positions of joints, amount of stretch in muscles, and many other changes. • Gravity and motion sensors in the inner ear contribute to the process of balance. • Sometimes included as part of the nervous system, since the main sense organs are in effect the specialized endings of sensory nerves. • Includes the nose, windpipe, main chest airways, and lungs. • Obtains essential oxygen from the air around and passes it to the blood for distribution. • Gets rid of waste carbon dioxide, which would be poisonous if it built up in the blood. • Also provides the ability to make vocal sounds and speech. DIGESTIVE SYSTEM • Mouth, teeth, throat, esophagus, stomach, intestines, rectum, and anus make up the digestive passageway or tract. • Liver, gall bladder, and pancreas are also part of the digestive system. • Digests food into nutrients tiny enough to take into the body. • Gets rid of leftovers as solid wastes. • Nutrients provide energy for all life processes and raw materials for growth, maintenance, and repairing everyday use. REPRODUCTIVE SYSTEM • The only system which differs significantly in females and males. • The only system which is not working at birth, but starts to function at puberty. • The male system produces sperm cells continually, millions per day. • The female system produces egg cells, about one every 28 days, during the menstrual cycle. • If an egg cell joins a sperm cell to form an embryo, the female system nourishes this as the egg grows into a baby inside the womb. LYMPHATIC SYSTEM • The lymph vessels, lymph nodes (glands), lymph ducts, and lymph fluid. • Gathers general body fluids from between cells and tissues. • One-way flow channels fluid through the lymph network of nodes and vessels. • Helps to distribute nutrients and collect wastes. • Lymph fluid empties into blood system. • Closely linked with to immune system. CIRCULATORY (CARDIOVASCULAR) SYSTEM • The heart, blood vessels, and blood. • The heart provides pumping power to send blood all around the body. • Blood spreads vital oxygen, nutrients, hormones, and other substances to all body parts. • Blood collects wastes and unwanted substances from all body parts. • Blood clots seal wounds and cuts. • Closely involved with the immune system for fighting disease. URINARY SYSTEM • The kidneys, ureters, bladder, and urethra. • Filters blood to get rid of unwanted substances and wastes. • Forms unwanted substances and wastes into liquid waste or urine. • Stores and releases urine. • Controls amount and concentration of blood and body fluids, called water balance, by adjusting amount of water lost in urine. HORMONAL (ENDOCRINE) SYSTEM • About ten main parts called endocrine or hormonemaking glands. • Some organs with other main tasks, like the stomach and heart, also make hormones. • Hormones spread around the body in blood. • Closely linked to the nervous system for coordinated control of inner-body processes. • Closely linked with reproductive system.. IMMUNE SYSTEM • Defends the body against invading dangers such as bacteria, viruses and other microbes. • Gets rid of debris in tissues from normal use. • Helps the body recover from disease and illness. • Helps repair injuries and normal use. • Keeps watch for problems and disease processes arising inside the body, such as malignant (cancerous) cells. 7 THE SKIN WHERE IN THE BODY? W hen you look at yourself in the mirror, most of what you see—skin, hair and nails—is not living. Just underneath this dead surface, however, skin is very much alive, and very busy, too—as you know if you’re unlucky enough to scratch or cut yourself. Skin is the body’s largest single organ. It has at least ten main tasks, which include providing your sense of touch. It wears away every month—but it replaces itself every month, too. The skin is a tough but flexible layer that covers the entire body. It helps to control temperature and protects internal organs from damage. SKIN MICROPARTS An average patch of skin 0.15 sq. in. (the size of a fingernail) contains: • 5 million microscopic cells of at least 12 main kinds. • 100 tiny holes, called pores, for releasing sweat. • 1,000 micro-sensors of about six main shapes for detecting various features of touch. TOUCH Your sense of touch or feeling is more complicated than it seems. It is not just a single sense, detecting physical contact. It is a multi-sense detecting: • Light contact, such as a brush from a feather. • Heavy pressure, such as being pushed or squeezed hard. • Cold, like an ice-cube. • Heat, such a hot water. • Movement, including tiny, fast vibrations. Your fingertip skin can detect vibrations that are too small for your eyes to see. • more than 100 hairs. • Surface texture, such as rough wood or smooth plastic. • About 3.2 ft. of blood vessels. • Moisture content, from dry sand to wet mud. Wearing warm clothes in winter helps protect our skin from feeling the cold. • About 20 in. of micronerves. • About 100 of the tiny glands that make sebum, a natural waxy-oily substance that keeps skin supple and fairly waterproof. DANGEROUS SWEAT A person can lose 10.5–15 pints of sweat before the body suffers from the loss of important salts and minerals. SWEAT FACTS Total number of sweat glands 3–5 million Total length of tubes in all sweat glands stretched out straight and joined end-to-end 31 miles Amount of sweat on average day 10–17 fl. oz. Amount of sweat on a cold day 2.3 fl. oz. 8 EXTRA SENSITIVE • Skin on the fingertips has more than 465 microsensors per square inch, to give the most sensitive touch. • It has more sweat glands that make a thin layer of sweat on the skin that helps you to grip better. • It also has tiny ridges or swirls to give even better grip. These form the pattern of your fingerprints. • Every set of fingerprints for every person around the world is different—even between identical twins. A thin layer of sweat on the fingertips helps you grip objects better.