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SPRING 2015 cranium oesophagus striated muscles thoracic duct diaphragm phalanges THE Y D O B N A M U H ISSUE metatarsals Spring 2015 uman h e h t o t e m We l c o GNIS! I f o e u s s i y bod to help this edition in t n te n o c t of d There is a lo dy works an o b r u o y w o rasp h main you better g ll about the a rn a e L . it behind nction the biology d how they fu n a y d o b e muscle systems of th Learn about . re a u o y o wh u to make you help keep yo s ll e c d o lo b hite ne types, how w your endocri t a h w , is ' h t 'lymp blood. healthy, wha tly is in your c a x e t a h w d e at the system is an ur knowledg o y t s te to iz ed to There is a qu have manag u o y h c u m how rs. e n d a n d see brain of you le ib d re c in t store in tha es , ments, queri m o c y n a e v you ha ow at As always, if ns, let us kn o ti s e u q r o s contribution suk.org lu n@potentialp e r d il h c g in z ama I n t h is is s u e : Editor: Freyja Taylor-Law Design and art direction: Max Plathan Address: Potential Plus UK, Suite 1.6, Challenge House, Sherwood Drive, Bletchley, Milton Keynes, MK3 6DP Tel: 01908 646433 Email: [email protected] Copyright 2015 Potential Plus UK. All rights reserved. IGNIS is published by Potential Plus UK (operating name for The National Association For Gifted Children). Should you wish to use articles or other material from IGNIS we are happy to consider requests and will require full source acknowledgement. 2 IGNIS 14–15 the lymphatic and immune systems the digestive system 4–5 systems of the body 6–7 the skeletal system 16–17 8–9 the muscular system 18–19 the urinary system 10-11 the circulatory system 12 the respiratory system 13 the nervous system 20 the endocrine system 21 the human body quiz 22 cool websites and quiz solution LIBROPHILIA The Concise Human Body Book: An Illustrated Guide to Its Structure, Function and Disorders By Dorling Kindersley and Medi-Mation Take an interactive tour of your body with this compact guide, amazing 3D images reveal all your major systems in molecular detail. Discover how the nervous system works, the intricate construction of skeleton and muscles, and how your body protects itself when you are under threat. Put yourself under the microscope to see the body’s processes in action from a nerve impulse to blood surging through an artery. Journey inside and examine what can go wrong with the human machine: explore the causes for and symptoms of diseases and ailments. An unmissable in-your-body adventure, perfect for students and families. The Complete Human Body By Alice Roberts and Medi-Mation Get under your skin with this access-all-areas guide to the human body. Discover a breathtaking portrait of the human body as it’s never been seen before, using the latest medical and microscopic imaging. The Complete Human Body covers the development, form, function and disorders of the human body, all brought to life by incredible state-of-the-art 3D computer-generated artworks. Take a detailed look at how your respiratory system works, discover the anatomy up-close and learn about over 200 diseases and how they afflict the human body. Perfect for students and families. Body: An amazing tour of human anatomy by Robert Winston A jaw-dropping tour of the anatomy from Robert Winston, awardwinning author and TV presenter. From how your blood flows through the heart to how your food is digested, take a trip through your very own body and be astounded by its inner workings. A free interactive CD shows the body and it’s movements in 3D detail and acetate pages fold back to reveal how our most important organs work. An irresistibly graphic, top-to-toe body atlas. IGNIS 3 Systems of the Body Your body has various systems that perform different functions and they all work together. These functions range from creating a new human being to absorbing nutrients and getting rid of waste. The Skeletal System This solid structure of bones is supported by cartilage and ligaments. It supports the body and gives it its shape. This system also protects the internal organs and allows us to move. Red blood cells (erythrocytes) are also generated by the skeletal system. The Muscular System The main function of the muscular system is to produce movement and to help to hold the shape of the body. The muscular system is made up of muscles, organs made of fleshy tissue and contractile cells. There are two main types of muscle; smooth and striated. Smooth muscles are controlled by the brain, but their movement is not voluntary. Striated muscles on the other hand control voluntary movement and they are attached to bones. Finally, there is the muscle tissue of the heart, called myocardium, which is entirely unique and its own separate class. The Circulatory System Blood is carried to and from the heart by the circulatory system, as well as to the organs and all of the cells in every part of the body. The heart pushes blood though the arteries and collects it back via the veins. 4 IGNIS The Respiratory System We need oxygen from the air in the outside world and the respiratory system brings air into our body through the upper airways and then the lungs absorb the oxygen and expel the carbon dioxide. This oxygenated blood is sent to all of the cells in the body by the circulatory system, and blood that needs purifying returns to the lungs. The Nervous System The brain and the spinal cord make up the central nervous system. There is a peripheral nervous system made up of spinal nerves and cranial nerves. These two systems send sensations (from both inside the body and outside) to the brain where they get processed and responded to. The Lymphatic System This system has two main jobs – to defend the body against foreign organisms and to transport interstitial fluid and substances from the digestive system into the bloodstream through the lymphatic drainage system. The Digestive System The digestive system is the path your food takes from your mouth to your rectum and anus. It includes the pharynx, oesophagus, stomach, small intestine and large intestine. The liver and pancreas help process the ingested food to extract chemical components. These can be welcome nutrients, which are used by the body whilst others are discarded. Urinary System This system keeps the body’s internal systems in equilibrium, or homeostasis. It regulates the amount of water in the body, discarding any substances that are toxic or in surplus. The main organs are the bladder and kidneys, with the ureters transporting the urine from the kidneys to the bladder, and the urethra carrying the urine out of the body. Endocrine System This system is made up of the glands in your body. It produces the body’s messengers – hormones – which are secreted into the bloodstream so they can head to the organ they are sent to excite, stimulate or influence. Reproductive System Female The internal organs of a woman's reproductive system are the vagina, uterus, ovaries and fallopian tubes. The function of these organs is to produce ova and facilitate the fertilisation of ovum by a spermatozoon and once this has occurred a pregnancy results. Male The male reproductive organs contribute one of the two cells needed for creating a new human being. Two testicles and a penis are the main organs. IGNIS 5 The Skeletal System This strong, resistant structure is made up of bones and supporting cartilage and ligaments. Our form and structure comes from our skeletal system, and it protects our internal organs. We are also able to move because of our skeletal system, in conjunction with our muscular system. The bone marrow within the centre of bones also produces blood cells. There are several types of bones, which are generally classified into the following groups: Clavicle Humerus Long bones These are bones such as the femur. They are longer than they are wide, and are the main bones in the limbs. These bones grow more in childhood than the other types and are responsible for most of our height. They tend to have a central section which lies between two end points called the epiphyses. Radius Ulna Short bones These are bones such as the heel bones which are about as long as they are wide and can often be round or cubed in shape. Flat bones Femur The ribs, hips and most bones of the cranium are flat bones. They range in size and shape but they are all very thin in one direction. Irregular bones These take various shapes that don't fit the pattern of long, short or flat bones. For example the coccyx and wedge-like sphenoid bones in the skull are irregular bones. Fibula Tibia Sesamoid bones These bones are small and round. These form after birth to protect tendons from stress and strain at the joint. The patella is a sesamoid bone. Cuneiforms Metatarsals Phalanges 6 IGNIS Cranium Parts of Bone s periosteum bone marrow Ribs compact bone Vertebrae Pelvis cancellous (spongy) bone Carpal bones Metacarpal bones Phalanges At birth, every long bone is made of three individual bones separated by cartilage. Each end of the bone is called an epiphysis and the middle bone is called a diaphysis. These bones grow towards each other and eventually fuse. Patella Calcaneus (heel bone) Talus There are several layers that make up a bone. The outer layer of periosteum is dense, connective tissue. Inside the periosteum is the compact bone which is one of the hardest materials in the body. It is made of a matrix of hard mineral salts, reinforced with tough collagen fibres. Beneath the compact bones is the spongy bone. This is a network in the form of a honeycomb. The bone tissue grows in columns called trabeculae. There are spaces for bone marrow in between these columns. Long bones also have a hollow medullary cavity in the middle of the diaphysis where red bone marrow is contained in childhood, turning into yellow bone marrow in maturity. IGNIS 7 The Muscular System Your muscular system is responsible for the movement in your body. You have three main types of muscle in your body – striated, visceral and cardiac. Striated Muscles Striated muscles are the muscles attached to your skeletal system and there are around 650 named muscles that fall into this category, which make up almost half of your body weight! They are the only voluntary muscles in your body, which means they are controlled consciously. Every action you choose to perform, such as walking, running, speaking, sitting is controlled by these striated muscles. The fibres in striated muscle are very strong and they contract rapidly. The purpose of these muscles is to contract in order to move parts of the body closer to the bone that the muscle attaches to. Most are attached to two bones by a tendon, 8 IGNIS across a joint, and the muscle brings these two bones closer - think of your arms or legs bending. A tendon is a tough band of dense connective tissue which attaches the muscle to the bone firmly. Striated muscles often do not work alone. They tend to work in pairs or groups to produce the movement your body requires. For example, your upper arm muscles are called your biceps and triceps. When your biceps (on the front of the arm) are contracted, your triceps (on the back of your arm) are relaxed – this lifts your forearm up. When you wish to put your forearm down, your triceps contract and your biceps relax. Visceral Muscles Visceral, or smooth muscle, is found on the inside of organs such as your blood vessels, stomach and intestines. Visceral muscles contract to move substances through the organ – such as food, waste and blood. It is the weakest type of muscle tissue, and it is controlled by the unconscious part of your brain – you can't control what it does just by thinking about it! This muscle type is often referred to as 'smooth' as it appears smooth when looked at with a microscope, which is very different to the banded appearance of skeletal and cardiac muscle. Cardiac Muscle Cardiac muscle is also striated, like skeletal muscle – they have dark and light stripes when looked at under a microscope. This tells us that the muscle is extremely strong (like skeletal muscles), unlike the visceral muscles in our organs. Cardiac muscle is found exclusively in the heart and its job is to pump blood throughout our whole body. Again, these muscles are involuntary – we cannot control them just by thinking about it. Although there are hormones in your body and signals from your brain that tell your cardiac muscle to change the rate at which it is contracting, your cardiac muscle tells itself when to contract. You have a 'pacemaker' in your heart, which tells the other cardiac muscles when to contract. This pacemaker is also made of cardiac muscle tissue. Because the muscle tissue can tell itself to contract, it is considered to be 'autorhythmic'. IGNIS 9 The Circulatory System The function of your circulatory system is to carry your blood to and from all of the organs in your body. It consists of your heart, blood vessels and all of the blood in your body (around 5 litres). By transporting the blood around your body, it is ensuring that oxygen, nutrients, hormones and waste products are transported throughout the body to the correct places. The circulatory system is powered by your body’s hardest working organ – your heart – this is your body’s engine. Blood Vessels Blood vessels are your body's transport systems – they allow blood to flow quickly from the heart to every area of your body and back again. The amount of blood flow that passes through the vessel will determine the size of the blood vessel. All blood vessels contain a hollow area through the middle where the blood is able to flow – this is called the lumen. Surrounding the lumen is the wall of the vessel, which can be thin or thick, depending on the function of the vessel. The Heart The muscula r pumping o rgan, located between you r lungs in the middle of yo chest is your ur heart. The ve ry bottom tip of your heart is called its a pex, and this turned to th is e left, meanin g that about tw thirds of you o r heart is loca ted on your side, with th left e other third on your righ heart has fo t. Your ur main cham bers – the le right atriums, ft and which are on the top half your heart, a of nd the left a nd right ven which are on tricles, the bottom h alf of your h eart. TO YOUR BO DY right atrium NGS left atrium FROM LUNG S FROM YOUR There are three main types of blood vessel: TO YOUR LU BODY right ventricle the septum left ventricle ARTERIES AND ARTERIOLES Arteries are muscular elastic blood vessels that bring oxygenated blood from the heart to all of the cells of the body. The blood is usually highly oxygenated. Blood is pushed into the arteries with great force, and arteries need to be able to withstand this. Therefore, artery walls are much thicker, more elastic and more muscular than other vessels. There are smaller arteries that are more muscular in their walls as they contract and expand in order to regulate blood flow to different parts of the body depending on circumstances. Arterioles are even narrower arteries that branch off from arteries and carry the blood into capillaries. The blood pressure in arterioles is lower than in arteries, as there are more of them, less blood flowing through them, and they are further from the heart. These arterioles are also capable of controlling the blood flow through them, regulating blood flow and pressure. 10 IGNIS VEINS AND VENULES Veins are the conduits that transport deoxygenated blood back to the heart after it has travelled to different areas of the body. They are the blood counterparts of arteries. Because it is the arteries, then the arterioles, then the capillaries that absorb the force of the heart's contractions, by the time blood gets to veins and venules, there is very little blood pressure. This means veins can have thinner walls with less elasticity. Some veins have one-way valves which prevent blood from flowing back away from the heart, forcing the blood to travel in only one direction. As skeletal muscles in your body contract and move, they squeeze veins and help push the blood through those valves and back to your heart. Venules are similar to arterioles in that they are small vessels, but instead of connecting to arteries they connect to veins. CAPILLARIES These are the branchin are the smallest and th and also the most comm in your body has capilla it. Capillaries connect to and venules on the oth crucial to the exchange waste and so they mus to the cells of the tissue exchange. Blood Did you know that your body contains around 5 litres of blood? Your blood is technically a liquid connective tissue – it transports many substances through your body and helps to maintain homeostasis - the control of your internal conditions such as nutrient, water, waste and gas levels. Your blood is made up of red blood cells, white blood cells, platelets and liquid plasma (which is actually yellow!) red blood cells white blood cells platelets Fo r ev ery cu bi c m ill ili tre of bl oo d A ro un d 4-6 m ill 4,5 0 0 -11,0 0 0 15 0,0 0 0 - 4 0 0 , 0 0 0 pl atel ets O n an av erag e da plasma Red blood cells are biconcave – they are like discs with a curve on both sides into the middle, so that the centre is the thinnest part. This means they can bend and take on a bell shape to pass through the thinnest blood vessels. It also gives them a high surface area to volume ratio. Immature red blood cells begin ngs of the arterioles. They with a nucleus, but this is pushed hinnest blood vessels mon. Nearly every tissue out of the cell when it is fully aries running through mature, to make it as flexible as o arterioles on one end it is and give it its shape. This her. These capillaries are does however mean that they e of oxygen, nutrients and carry no DNA, meaning that they st carry blood very close es in order to make this cannot repair themselves when they become damaged. io n re d bl oo d ce lls w hi te bl oo d ce lls y yo u prod uc e: 20 0, 0 0 0 m ill io 10,0 0 0 m ill io n w hi 4 0 0, 0 0 0 m ill Red Blood Cells Red blood cells are also known as erythrocytes, and are the most common type of blood cell and make up around 45% of your blood. They are known as phantom cells as all that they contain is a large amount of haemoglobin – a protein that has a great affinity for combining with oxygen. Red blood cells cannot reproduce themselves, and must be replaced by new blood cells that are produced inside of red bone marrow from stem cells at the amazing rate of about 2 million cells every second! yo u have : n re d bl oo d ce lls te bl oo d ce lls io n pl atel ets White Blood Cells White blood cells are also known as leukocytes. These make up only a small percentage of the total number of cells in your blood stream. However, white blood cells are extremely important to your body's immune system. There are two major classes of white blood cells: Granular leukocytes There are three types of granular leukocytes; neutrophils, eosinophils and basophils. Neutrophils contain digestive enzymes that neutralise bacteria invading the body, eosinophils contain enzymes that digest viruses that antibodies in the blood have bound to and basophils release histamine in order to intensify allergic reactions, protecting the body from any parasites. Agranular leukocytes There are two main types of agranular leukocytes – monocytes and lymphocytes. Monocytes develop into microphages and engulf and ingest pathogens from infections and wounds. Lymphocytes include B cells that produce antibodies to fight of infections by pathogens and T cells that fight off viral infections. IGNIS 11 The Respiratory System The main function of the respiratory system is to supply your blood with oxygen so that the blood can deliver this oxygen to all parts of the body. We do this through breathing - we inhale oxygen and exhale carbon dioxide, both of which are usually involuntary and automatic. This exchange of gases is the respiratory system’s way of getting oxygen to the blood. When you breathe in, the air enters in through your nasal cavity or mouth. It is then warmed and cleaned. From there it heads through the pharynx, where your tonsils intercept any harmful organisms and destroy them. From here, the air then passes through your larynx. The epiglottis, the upper part of the larynx, stops food from going through into the larynx when you are swallowing. The air then follows into the oesophagus. As it goes down the air reaches the trachea, also known as the windpipe, which is a tube lined with cilia that transports the air in and out of the lungs. The trachea has rings of cartilage all the way along it that prevent it from being squashed or crushed. Cilia are special hairs that prevent dust or dirt getting into the lungs. They move back and forth, carrying mucus up and out. Mucus, which is a sticky fluid, collects the dust and we expel it when we sneeze, cough, spit or swallow. The trachea branches out into two main bronchi, and each of these is divided into smaller branches, called bronchioles, and then into pulmonary alveoli, which are like little sacks where the gases are exchanged. The oxygen passes into the blood at the alveoli and then is transported to the tissues all over the body. The carbon dioxide passes back from the bloodstream into the alveoli to travel back up and be exhaled. 12 IGNIS Your diaphragm is a sheet of muscles that lies across the chest cavity – it helps to push the carbon dioxide out and pulls the oxygen in. As the diaphragm contracts and relaxes, breathing takes place. When the diaphragm contracts, oxygen is pulled into the lungs. When the diaphragm relaxes, carbon dioxide is pumped out of the lungs. Why do we yawn? When you are too tired, your lungs do not take in enough oxygen from the air you inhale. This means you do not have enough oxygen coming into your body, and when your brain senses this shortage, it sends a message that causes you to take a big long breath, or a yawn! Why do we sneeze? Sneezing is a bit similar to a cough, it helps to remove something that is irritating the mucous membranes of the nose. What are hiccups? This is when your diaphragm suddenly moves, and this is involuntary. This can happen if your diaphragm gets irritated, you eat too quickly or many other things. When you breathe in, the air enters in through your nasal cavity or mouth. It is then warmed and cleaned. From there it heads through the pharynx, where your tonsils intercept any harmful organisms and destroy them. The Nervous System Your nervous system is the most complex system in your body – much of which is still a mystery to us. Your nervous system is what controls your whole body and also manages all of your intellectual activities such as memory, choice and emotions. The nervous system consists of the brain, spinal cord, sensory organs and all of the nerves which connect to the rest of the body. The central nervous system consists of the brain and spinal cord and the peripheral nervous system consists of the sense organs and sensory nerves. The Central Nervous System (CNS) The Peripheral Nervous System (PNS) Your brain consists of a cerebrum, cerebellum and spinal bulb. Your spinal cord along with your brain receives information from your sense organs and sends out instructions to all of your muscles and other organs. The central nervous system is also responsible for processing and coordinating nervous signals that are transmitted from the peripheral nervous system. The peripheral nervous system provides information to the central nervous system and also coordinates your movement. It informs your CNS about external changes detected by your senses and internal changes such as having a full bladder. It sends instructions for your conscious movement such as walking, sitting, running and also controls the functioning of your internal organs. Neurons Cells of the nervous system are called neurons. They transmit impulses in the form of electrical signals and carry information to the brain. Your brain has around 100 billion neurons that come in many different shapes and sizes. Each neuron in your brain can be connected with several thousand other neurons and can receive up to 100,000 signals a second. They are similar to other cells in your body in many ways, but they are also very different. Neurons have special cell parts called dendrites and axons. Dendrites are the branches through which a neuron receives signals from other neurons. There can be around 200 dendrites per neuron, but this varies. The axon is the nerve fibre that transmits impulses. There are three main types of neurons, based on how complicated their axons and dendrites are: 1. Unipolar These have two branches of the same axon that extend from one cell body 2. Bipolar These neurons have two completely separate axons that extend from each end of a cell body 3. Multipolar These have one axon with a number of dendrites extending from a cell body. IGNIS 13 The Lymphatic and Immune Systems The lymphatic and immune systems, although technically two different systems, are very closely related. The immune system is our defence system – it defends us against foreign organisms, bacteria, fungi and parasitic animals. The lymphatic system is a system of nodes, capillaries and vessels, along with other organs, that transport a fluid called ‘lymph’ from the tissues as it returns to the bloodstream. The lymphatic tissue in these organs filters and cleans the lymph of debris and pathogens. The lymph also contains cells called lymphocytes and macrophages which are part of your immune system. Invaders The types of invaders your immune system and lymphatic system are trying to fight off are: Protozoa There are also living organisms that normally live in the soil or water. They can produce a range of diseases including malaria and diarrhoea. Bacteria Bacteria are life forms found in billions everywhere you look. Not all bacteria are harmful but bacteria known as germs are pathogenic and release poisonous substances called toxins. Viruses Viruses are not living things, they are more like chemical packages. They are made up of genetic material and when they enter the body they invade a cell and then reproduce and spread. 14 IGNIS Immune Response Your lymphatic system generates cells called lymphocytes, which are also found in your blood, as well as macrophages. These are what make up your immune system. B lymphocytes learn information from the surface of invading bacteria that they use to recognise other similar bacteria and Macrophages engulf and ingest invading bacteria. When a pathogen is recognised, B lymphocytes are activated and begin dividing themselves into memory cells and plasmatic cells. Memory cells hold on to the antigen information and when there is a new invasion they begin dividing rapidly in order to deal with it. The plasmatic cells secrete thousands of special antibody molecules per second, which the blood then carries to wherever the infection is. The antibodies are also known as immunoglobin and they are special protein molecules that are the shape of a Y. Each Y's arms are unique to a particular type of antibody, and each specific antibody attaches with these arms to a specific antigen. These antibodies are there to mark out invaders so that macrophages can destroy them. Lymphatic Network As your blood passes through the tissues in your body, it enters capillaries to transfer nutrients, gases and waste. Blood plasma also diffuses through the capillary walls and enters the spaces between cells in the tissue. Although some of this plasma diffuses back into the blood, some of the fluid becomes embedded. To prevent the build up of these excess fluids, small vessels called lymphatic capillaries also extend into these tissues to absorb these fluids and return them back to circulation around the body. This liquid left in the tissues is called lymph. Lymph is very similar to plasma – it is mostly water and contains proteins, cellular waste and hormones. It also contains bacterial cells that are picked up from diseased tissues in the body, as well as the white blood cells that are fighting these pathogens. The vessels that transport this lymph (lymphatic capillaries) are similar to veins. They have thin walls and valves to help move fluid under low pressure. The skeletal muscles also help to push lymph back through the capillaries in the same way as veins. Lymph Nodes and Ducts These are small, round glands about 1 centimetre in diameter. They are distributed throughout the body – in your neck, armpits, groin and behind your knees, as well as around your thorax and abdomen. These lymph nodes work like filters for the lymph that arrives at them from several lymph vessels. There are special fibres inside the lymph nodes that act like a net to catch any cells or debris that are in the lymph. Macrophages and lymphocytes in the lymph node attack and kill microbes that get caught inside. The filtered lymph is then carried out of the node towards lymph ducts. There are two main lymph ducts – the Thoracic duct and the Right Lymphatic Duct. These return lymph back to the blood supply so that it can be recirculated as plasma. Other External Defences As well as your lymphatic and immune system, you also have some natural external defences that aim to prevent infections before they get inside your body. Your skin is your first defensive barrier that is there to protect you. You also have various glands that secrete mucus, tears, saliva and sebum which trap, move and can kill bacteria. Your stomach acid also kills microbes found on food. IGNIS 15 Six ma take pl The Digestive System 1. inges 2. secre 3. mixin 4 . diges 5. absor 6. excre Your digestive system is a group of organs that work together to transform food into fuel for your entire body. You begin by ingesting food through the mouth and oesophagus, continue digestion in your stomach, small intestine and large intestine, and then your faeces are evacuated through your rectum and anus. 1 YOUR MOUTH 1 This is where your food first arrives – the oral cavity. Your tongue, teeth and salivary glands all aid in the digestion of your food. The tongue and teeth are the very first specialists that your food encounters. Your tongue tastes and positions the food, which is then cut and ground by your 32 (adult) teeth. Your saliva moistens the food, and also begins digesting the carbohydrates, while the palate prevents food from passing up into your nose. The tongue then pushes the chewed food (or bolus) to the back of your oral cavity and into the pharynx. 2 YOUR THROAT Your throat, also known as your pharynx, is a funnel shaped tube that connects from your mouth to your oesophagus. It passes the chewed food to your oesophagus, but also contains a flap of tissue called your epiglottis, which acts as a switch to send food to the oesophagus and air to the larynx. 3 OESOPHAGUS This thick muscular tube is part of the upper gastrointestinal tract. It carries the food down into the stomach using peristalsis – a wave like muscular motion. It has a sphincter muscle at the bottom, which is a muscular ring, which prevents food coming up from the stomach. 16 IGNIS 3 7 6 5 ajor function s lace: stion etion ng and movem ent stion rption etion 2 4 STOMACH 5 SMALL INTESTINE 6 THE LIVER 7 THE GALLBLADDER & PANCREAS 8 THE LARGE INTESTINE This is the first section of the digestive system that is located in the abdomen. It is the shape of an empty bag, curved like a bagpipe. In a normal person, your stomach is about the size of two of your own fists alongside one another. It is a storage tank for food so that your body can digest it properly. Gastric juices and enzymes subject the swallowed food to intense chemical reactions whilst also mixing it completely. Peristalsis moves the food from the stomach to the duodenum, which is the initial section of the small intestine. This is a long, thin tube, around 10 feet long and an inch in diameter. This is where the lower gastrointestinal tract begins. It is all coiled up like a garden hose and its interior surface is covered in millions of hairlike structures called villi. Each has a lymphatic vessel and a network of vessels delivering nutrients to it. The villi absorb nutrients and help to increase the surface area of the small intestine – increasing the absorption of nutrients. Your liver is roughly triangular which is located to the right of your stomach. It is the largest gland in the human body and the second largest organ. The liver's main function with regards to digestion is to produce bile and secrete it into the small intestine. Bile helps with the digestion of fats. The liver also regulates glucose levels, regulates the metabolism of proteins and is a large blood filter, storing vitamins A, D, E and K. 4 8 The gallbladder is pear-shaped, small organ that stores and recycles excess bile so that it can be reused. The pancreas is a large gland that secretes digestive enzymes into the small intestine that breaks down fats, proteins and carbohydrates. This long, thick tube (about 2 ½ inches in diameter) is about 5 feet long. It absorbs water and contains bacteria that help break down waste so that it can extract small amounts of nutrients. The faeces then leave the large intestine through the anal canal. IGNIS 17 The Urinary System The basic organs of the urinary system are the kidneys, ureters, bladder and urethra. The function of the urinary system is to regulate homeostasis – keeping the equilibrium between chemicals in the body and water. The kidneys produce and secrete urine, which is eliminated from the body. It is harmless and sterile and composed mostly of water and salts, and around 2% urea. Ureters carry the urine through the body to where it is stored in the bladder, from which it is passed to the urethra, from which it will be expelled from the body. The Kidneys These bean shaped organs regulate the amount of water and minerals in the blood. They produce urine that carries away the waste that the kidneys discard. It is their job to ensure that the composition of the bodily fluids is constant. They also regulate the pressure of the arteries. Around 1,750 litres of blood is processed by the kidneys every day and around 1.5 litres of urine is produced by them. Although they only account for 1% of your total body weight, they consume 25% of your energy! Each kidney contains around 1 million individual nephrons – these are the microscopic functional units that filter the blood. Arterioles in the kidneys deliver blood to a bundle of capillaries surrounded by a capsule, which is called a glomerulus. When blood flows through the glomerulus, lots of the blood's plasma is pushed out of the capillaries and into the capsule. The blood cells and a small amount of plasma are left to flow through the capillaries, and the liquid pushed through into the glomerulus flows through several tubules lined with filtering cells, surrounded by capillaries. The cells absorb some water and substances and return it to the blood in the capillaries, and then the waste products in the blood are secreted into the fluid in the capsule. At the end of the process, the filtrate in the tubule is urine, containing just water and waste, and the blood exiting via the capillaries has reabsorbed nutrients and most of the water. 18 IGNIS Ureters This pair of tubes carry urine from the kidneys to the urinary bladder. They are around 11 inches long and run on the left and right side of your body, parallel to your spine. Urinary Bladder This is another sac-like organ that is hollow in the middle, where it stores urine. As the hollow space fills, the elastic walls of the bladder are stretched to accommodate anything from 600-800ml of urine. Urethra The tube through which your urine passes out of your body from the bladder is called the urethra. This is different in males and females. In females, it is only around 2 inches long, and it ends just above the vaginal opening. In males, the urethra is around 9 inches long, and ends at the tip of their penis. In the case of males, the urethra is also part of the reproductive system as it also carries sperm out of the body. There are two sphincter muscles that control the flow of urine through the urethra. The internal sphincter is made of smooth muscle and opens involuntarily whenever the bladder reaches a certain level – this is what tells us we need to urinate. The external sphincter is made of skeletal muscle and we can open it to allow urine out or hold it closed to delay urination. IGNIS 19 The Endocrine System The endocrine system consists of all of the glands inside the body that secrete around 50 hormones into the blood. The glands are controlled by the nervous system as well as by chemical receptors in the blood and other hormones secreted from other glands! These hormones activate and stimulate different organs and control metabolism, reproduction and development. The chemicals control lots of the body’s processes. The Hypothalamus Adrenal Glands The hypothalamus is part of the brain and it serves many functions in the nervous system, as well as controlling the endocrine system through the pituitary gland. It has special cells called neurosecretory cells which are neurons that secrete hormones. The hormones it releases affect the pituitary gland. The hormone adrenaline is what wakes your body up when you feel at risk or before you kiss someone. This is produced by your adrenal glands, which are found by your kidneys. It increases your cardiac rhythm, the pressure in your arteries and the flow of blood to your muscles. The Pituitary Gland The pituitary gland is also known as the master gland as it controls the rest of the endocrine glands. It has an anterior lobe and a posterior lobe. It is a small pea-sized lump of tissue connected to the hypothalamus. There are lots of blood vessels surrounding it to carry the hormones that it releases through the body. Your pituitary gland is also associated with psychological behaviours such as affection. The Pineal Gland This is a small mass of glandular tissue found below the brain. It helps to regulate our sleep-wake cycle, known as the circadian rhythm, by producing melatonin. The pineal gland is told not to release melatonin when the photoreceptors in your retina are stimulated – when they receive light. When you are in low light or darkness, the pineal gland produces melatonin, causing you to feel drowsy. 20 IGNIS The Pancreas The pancreas increases the glucose level in your blood before you kiss someone. It is in charge of the two hormones that control your blood sugar level – glycogen and insulin. Glycogen increases the blood sugar levels in the bloodstream and insulin lowers blood glucose levels after a meal. Pheromones These are chemical substances released by the glands in your skin that are related to sexual attraction. They transmit sensations of excitation, attraction and also, unfortunately, rejection. Oxytocin Oxytocin is the hormone that influences basic body functions – birth, breast-feeding and being in love. It is commonly associated with affection and tenderness, and it stimulates the formation of bonds of affection. Quiz solutions o n the back p age Click a question to jump to the page where you can find out the answer! Q1. What are the three types of muscle? Q11. What are arteries? Q2. What function does the epiglottis have? two types of muscle are Q12. What striated? Q3. Which of these three groups are not living things - Viruses, bacteria and protozoa? Q4. What vitamins does the liver mainly store? Q5. What is the function of a ureter? is the very bottom tip of Q13. What your heart called? how many litres of Q14. Roughly blood are in your body? is the technical name for Q15. What platelets? What are epiphyses? how much of plasma Q16. Roughly is water? Q7. What percentage of your blood do red blood cells make up? how many red blood Q17. Roughly cells are made every second? Q8. What is the technical name for red blood cells? shape are red blood Q18. What cells? Q9. What are white blood cells also known as? Q6. are the two major classes Q10. What of white blood cells? Q19. What are pheromones? are the two hormones Q20. What that control blood sugar level? IGNIS 21 ! s e t i s b e Cool w Healthline – Body Maps www.healthline.com/human-body-maps BodyMaps is an interactive visual search tool that allows users to explore the human body in 3-D. With easy-to-use navigation, users can search multiple layers of the human anatomy, view systems and organs down to their smallest parts, and understand in detail how the human body works. Visible Body www.visiblebody.com/index.html This site holds a 'learn anatomy site', has free anatomy e-books and anatomy apps to download. Visible Body's 3D anatomical models of the human body are the foundation of their content. Their award-winning and best-selling apps cover gross anatomy and microanatomy, as well as physiological processes and pathologies. National Geographic – Explore the Human Body www.science.nationalgeographic.com/science/healthand-human-body/human-body/ The National Geographic human body site has videos, articles, news, interactives, quizzes and photos. There really is a lot here to investigate and satisfy your enquiring mind! QUIZ SOLUTION: 1. Cardiac, visceral (or smooth) and skeletal (or striated) 2. The epiglottis stops food from going into the larynx 3. Viruses 4. A, D, E and K 5. The ureters are tubes that transfer urine from the kidneys to the urinary bladder 6. Epiphyses are the two end points of a long bone 7. 45% 8. Erythrocytes 9. Leukocytes 10. Granular leukocytes and agranular leukocytes 11. Arteries are muscular elastic blood vessels that bring oxygenated blood from the heart to all of the cells of the body. 12. Cardiac and striated/skeletal. 13. It’s apex. 14. 5 15. Thrombocytes 16. 90% 17. 2 million cells every second! 18. Biconcave 19. These are chemical substances released by the glands in your skin that are related to sexual attraction. 20. Glycogen and insulin.