Audrey Supan Main OrgansThe human body systems work together which performs essentially to maintain health. Most parts of the human body rely on each other to make sure they all function properly to remain stable. Some organs may be part of more than one body system, if they serve more than one function. All body systems are important for life to be sustained.There are 15 main organs in the body that helps in everything a human does on a day-to-day basis. These are the skin, heart, lungs, stomach, bladder, brain, eyes, ears, pancreas, intestines, liver, ovaries, kidneys, testes and uterus.  The SkinThe skin is the outer layer that protects everything else internally and it is made up of different types of tissues. Its role is to help external stimulation, fights against damage or infection, prevents drying out, helps with the regulation of body temperature, excretes waste such as sweat, stores fat and makes Vitamin D*. It holds many tiny structures, each with different function. The whole skin which includes tissue layers and structures is called the integumentary system.The three types of layers of the skin are the epidermis, dermis and the subcutaneous layer. The epidermis is the thinner layer of the skin which forms epithelium (a thin tissue that forms the outer layer of the body’s surface and lining the alimentary canal and other hollow structures). Whereas, the dermis is the thick layer of the connective tissue under the epidermis and it contains many capillaries that supplies food and oxygen. And lastly, the subcutaneous layer is a layer of fatty tissues which is found below the dermis which stores larger blood vessels and nerves. It acts as an insulator and maintains a balanced body temperature.There are 8 structures in the skin and these are Meissner’s corpuscles, sebaceous glands, Arrector Pili Muscle (hair erector muscles), hair follicles, pain receptors, hair plexuses, sweat glands and Pacinian corpuscles.Meissner’s corpuscles are a type of nerve ending in the skin which is mostly responsible for sensitivity to light touch. This can be found mainly on the fingertips and palms. Its role is to send impulses to the brain when the skin comes in contact with an object.Sebaceous glands are tiny glands in the skin which opens into hair follicles and produces oil called sebum which waterproofs the hairs and epidermis, keeping them supple. As dead outer cells are difficult for microbes to penetrate, the oils from the sebum help kill microbes.Arrector Pili muscle is a small muscle that connects to each of every hair follicles and the skin of the body. When you get cold, your blood vessels constrict which straightens the hairs so that it can trap warm air and improve insulation; this also cause goosebumps. However, when we get too hot, our blood vessels dilate so that it allows more warm blood to flow near the surface of the skin, where the heat can be lost to the air and this causes us to sweat which also help cool us down.The hair follicles are long, narrow tubes and all contains hairs. This grows new cells which add to its base from the cell lining the follicle. The older cells die as keratin and are formed inside the hairs.Pain receptors are found in nerve fibre endings in the tissue of most inner organs and also in the skin. They are receptors that send impulses to the brain when any stimulation becomes excessive such as pressure, heat or touch. This is what causes a sensation of pain.Hair plexuses is a special group of nerve fibre endings and each form a connection around the hair follicle which is a receptor that sends nervous impulses to the brain, in this case when our hair moves.Sweat glands excrete sweat and each has a narrow tube called the sweat duct going to the surface. Sweat consists of water, salts and urea which enter the gland from the cells and capillaries.Pacinian corpuscles are formed around single nerve fibre endings which lie in the lower skin layers and in the walls of inner organs. It is a pressure receptor that sends impulses to the brain when tissues receive deep pressure than light touch.The HeartThe heart is a muscular organ which pumps blood around the blood vessels other known as the cardiovascular system. The heart is mostly hollow and it is composed of cardiac muscles called myogenic and connective tissues.There are four valves in the heart which stops blood from going the wrong way and they are placed between the right atrium and ventricle, between the left atrium and ventricle, at the entrance to the pulmonary artery and at the entrance to the aorta.The atria are the two upper chambers; the left side receives oxygenated blood from our lungs through the pulmonary veins. Whereas, the right atrium receives the deoxygenated blood from the rest of the body.The ventricles are the lower chambers; the left ventricle receives blood from the left atrium which pumps into the aorta. Whereas, the right ventricle receives blood from the right atrium which pumps through the pulmonary trunk to the lungs. The ventricles contracts which forces blood to come out.The aorta is the largest artery in the body; its purpose is to carry blood with fresh oxygen out of the left ventricle to start the process round the body. The pulmonary trunk is an artery that carries blood needing fresh oxygen out of the right ventricle. When it has left the heart, it separates both ways in the pulmonary arteries, one going to each lung. Whereas, the four Pulmonary veins carry fresh oxygen from the blood to the left atrium. The right pulmonary veins come from the right lung whereas, the two pulmonary veins come from the left lung.The muscular wall of the left ventricle is thicker than the right side as it has to pump blood around the body. The right ventricle is thinner as it only needs to pump blood through the lungs. The heart has its own blood supply which comes from the coronary arteries.Heart is the most vital organ which locates in the centre of the chest with a slight tilt to the left. With rhythmic muscle contractions, it helps circulate blood through the veins and arteries that supplies tissues with oxygenated blood and get rid of waste.The cardiac cycle is the process of making up one complete pumping action of the heart other known as heartbeats which is about 70x a minute. The first process is when the two atria contracts and pumps blood into the ventricles which relax in order for it to receive it. When the atria have relaxed, it takes in the blood, which the ventricles pump out by contraction. The different valves open and closes during the cycle just so blood loss won’t occur.Respiratory SystemThe respiratory system covers three processes in ventilation, external and internal respiration. Ventilation is all about taking in oxygen and expelling carbon dioxide, external respiration is the exchange of gases between the lungs and the blood. Lastly, the internal respiration is the breaking down of food, using oxygen and producing carbon dioxide.Both lungs are sponge like, air- filled organs which are located on either side of the thorax. Each lung is split into lobes, the right has three and the other only has two therefore allows more space to accommodate the heart. The tissue in the lungs is almost as 40 times bigger than the body’s outer surface which makes the lungs one of the largest organ in the body. The lungs are one of the most hard-working organs in the body. TheyExpand and contract up to 20x a minute so they can supply oxygen to be distributed to tissues all over the body and expel carbon dioxide that has been created throughout the body.Breathing is an automic which stems from the brain and it is situated in diencephalon. This is made up of inhalation and exhalation, both actions are automatic which is often controlled by nerves from the respiratory centre in the medulla which is found in the brain that controls many unconscious actions. This act when it detects too high a level of carbon dioxide in the blood.Inhalation is the act of breathing in which causes the diaphragm contracts and flattens, lengthening the chest cavity. The muscles between the ribs also contracts, pulling the ribs up and outwards which help widen the cavity. This is so the expansion can lower the air pressure in the lungs, and then the air rushes to fill in the lungs.Exhalation is the act of breathing out which causes the diaphragm and intercostal muscles to relax so that the air can be forced out of the lungs as the chest cavity decreases in size.Carbon dioxide exitsOxygen in Intercostal muscles relaxes, ribs move down and inwardsIntercostal muscles contract, pulling ribs out and outwardsDiaphragm relaxesDiaphragm flattensTrachea is the main tube in which is responsible for passing air on its way to and from the lungs. The lungs are the two main breathing organs which gases are exchanged and they contain a lot of tubes and air sacs called the alveoli. Alveoli’s role is to allow oxygen to dissolve in its moist surface and this has a thin lining for an easier diffusion of gases. It also got a dense channel of blood capillaries for easy gas exchange and a large                                                     The Digestive SystemAfter the food has been ingested, it goes through the digestive system; this then breaks down into soluble substances by a process called digestion. The substances will then get absorbed into the blood vessels around the system then transported to the body cells. The pancreas and liver play a vital role in digestionThe stomach is a J-shaped, elastic, hollowed organ which is located just inferior to the diaphragm in the left part of the abdominal cavity. It is located between the oesophagus and the duodenum, the stomach is like a roughly crescent-shaped enlargement of the gastrointestinal tract.The oesophagus or a gullet is the tube which food travels down to the stomach. The duodenum is the first part of the small intestine immediately beyond the stomach, leading to the jejunum. There are two types of sphincter which are cardiac and pyloric. Cardiac sphincter is a muscular ring between the oesphagus and stomach; this relaxes so that food can go through. The pyloric sphincter however is a muscular ring between the stomach and the small intestine; this relaxes once after a change have occurred so that food can go through.The inner layer of the stomach is full of wrinkles known as rugae which allow the stomach to stretch in order to take in larger meals and help grip and move the food during digestion. The size of the stomach may come differently depending on the person, but on average it can comfortably contain 1-2 litres of food and liquid during a meal. When this stretch, it can hold up to 3-4 litres when we overeat or have larger meals.Through the process of digestion, the stomach produces hydrochloric acid. This helps kill off many harmful microorganisms that might have been swallowed along with the food. This is important as enzymes in the stomach work better in acidic condition at a low ph. The stomach can store a meal for about 1-2 hours. During this period, the stomach continues the digestive process that started in the mouth and lets the intestines, pancreas, gallbladder, and liver to prepare to complete the digestive process.The food goes through four processes once masticated. Firstly, it is ingested which is the process of putting all nutrients in your system. Secondly, it gets digested, which is the mechanical and chemical of breaking down of food then this goes through the process of absorption which is when all digested food gets absorbed making it to waste. Lastly, it gets eliminated which gets rid of all unneeded materials through excretion.The Urinary SystemThis is the main system of body parts which involves in excretion; this is the expulsion of unneeded substances. The lungs and skin are also involved in excretion which expels carbon dioxide and sweat respectively. The bladder is a sac that holds up urine. Its lining has many folds which is called rugae, this flattens out as it fills up, making it bigger. This is located in the lower abdominal area near the pelvic bonesThe bladder, like the stomach, is an expandable saclike organ that contracts when it is empty. The two muscular rings, the internal and external urinary sphincter controls the opening from the bladder into the urethra. When liquid reaches up to a certain level, nerves will start to stimulate the internal sphincter to open while the external sphincter stays under conscious control and be closed for longer period of time.The urethra is the tube carrying urine from the bladder out of the body. This process is called urination. The urine is the liquid which exits the kidneys. Its main components are excess water, urea which is a nitrogen- containing waste material which help with process of breaking down excess amino acids in the liver. It travels through the blood to the kidneys, along with smaller amounts of similar substances.The BrainThis is an organ which controls most of the body’s activities. It is the only body organ that is able to produce intelligent action based on stored information, this includes present events and future plans. It is made up of vast amounts of neurons, arranged in sensory association and motor areas. The sensory areas receive the information from all body parts whereas the association areas analyses impulses and make decisions. The motor areas send impulses to the muscles or glands. These impulses are carried by the fibres of 43 pairs of nerves in the spinal cord.The human brain is the largest brain of all vertebrate’s relative to body size, it weighs about 3.3 lbs. and it makes up about 2% of a human’s body weight. The cerebrum makes up 85% of the brain’s weight and contains about 86 billion nerve cells called the “grey matter”. It contains billions of nerve fibres which are axons and dendrites; “white matter”. These neurons are connected by trillions of connections, or synapses.The Cerebrum, being the largest area is made up of two halves. The right half controls the left side of the body and the left side controls the right. Each half splits into four lobes which controls different functions like the thinking, memory, behavior, personality, learning, hearing, sight, language and touch. The cerebellum is the area which co-ordinates muscle movements and balance, the two things under the overall control of the cerebrum. This is located at the back of the brain. The brain stem controls vital functions such as breathing and heart rate and the pituitary gland is at the base of the brain which controls hormone production in the body.The EyesThe eyes are the organs for living organisms to be able to see, this sends nervous impulses to the brain when stimulated by light rays from external objects. The brain interprets the impulses to produce images. Each eye consists of a hollow, spherical capsule which known as the eyeball. This is made up of different layers and structures. It is placed into a socket in the skull and it is protected by the eyelids and eyelashes. The eyes have several major components which are the cornea, pupil, lens, iris, retina and sclera. These organs all work together to capture an image and transmit it directly to the brain’s occipital lobe through the optic nerve. Eyes are approximately one inch in diameter. Pads of fat and the surrounding bones of the skull protect them.Our eyes can only see in two dimensions, we are able to determine distances and depth in our three-dimensional world. This is so the brain can interpret the two slightly different images our left and right eyes visualise as one. This is called stereoscopic vision. Other visual cues like shadows, how objects are blocking each other, and our knowledge about the sizes of different objects also help us determine depth and distance.When a person looks at an object, the light that reflects from it enters the eyes and then refracted or bend so that it can create a focused, upside down image of the object which the brain could interpret and turn to a right direction. In the actual eye are photoreceptors which create nerve impulses when struck by light. These are two types: cones make colour vision possible, and rods specialize in black and white images.The EarsThe two ears are the organs of hearing and balance, but this depends on specialised receptors called hair cells. Each one is split into three parts, one being the outer ear, second being the middle ear and the third the inner ear.The outer ear is the shell of the skin and cartilage, together with a short tube and this tube lining has its own special sebaceous glands which secrete ear wax. The middle ear is an air- filled cavity that contains a chain of three tiny bones called the malleus and stape. Lastly, the inner ear is a connected series of cavities in the skull, with tubes and sac inside them.Through the process of hearing, the eardrum vibrates when soundwaves enter the ear canal. Ossicles are the three tiny bones that are found in the ear which also includes the stapes, being the smallest bone in the body. Vibrations pass to the oval window, which is a membrane at the entrance of the inner ear. Sound waves enter through the outer ear, and then it travels down to the middle ear till it reaches the inner ear and its intricate network of nerves, bones, canals and cells.The inner ear and hearing consists of cochlea and cochlear duct. A cochlea is a spiral tube cavity which is part of the inner ear and this contains perilymph (fluid between the membranous labyrinth of the ear and the bone which encloses it) in two channels and with the third channel. A cochlea is a spiral tube within the cochlea, connects to the saccule and this contains endolymph and a long body called Corti. This has special hair cells which projects itself into the endolymph and touch a shelf-like tissue layer. These cells are attached to nerve fibres.Balance on the other side, is achieved through both of the sensory organ in the inner ear, visual input and the information received from receptors in the body, especially around joints. These information gets processed in the cerebellum and cerebral cortex of the brain which then allows the body to cope with any changes in speed and the direction of the head.The PancreasPancreas is a large gland which is both a digestive gland and an endocrine gland. It produces pancreatic juices which secretes along the pancreatic duct and this help break down food in the small intestine, along with other components such as bile and other fluids that helps metabolism of fats and proteins. This also consists of group of cells called the islets of Langerhans which make up the endocrine parts of the organ and produce hormones such as insulin and glucagon.The pancreas is located below and behind the stomach, in the curve of the duodenum, which is part of the small intestine. This is a glandular organ that produces a vast number of hormones into the body and this form an integral part of the digestive system. This is an essential organ as it regulates glucose levels in the blood so if the pancreas stops producing insulin, it can lead to conditions like diabetes and a number of health issues.The large intestinesThis is also known as a colon and is a thick tube that receives waste from the small intestine. It contains the caecum, colon, rectum and anal canal. It also consists of bacteria, which helps in breaking down any remaining food and provide more vitamins needed for the body. The colon contains four parts which are the descending colon, ascending colon, transverse colon and sigmoid colon.The descending colon is the part of the large intestine which passes downwards on the left side of the abdomen towards the rectum whereas the ascending colon comes in the main part of the large intestine, which passes from the caecum on the right side of the abdomen. Transverse colon is in the middle part of the large intestine which passes across the abdomen from right to left below the stomach. Lastly, the sigmoid colon is the S-shaped which comes at the last part of the large intestine, leading into the rectum.The water in the food we consume passes through the colon walls into nearby blood vessels. This plays in a much smaller role such as storing waste, reclaiming water, maintain water balance and absorb certain vitamins. As a result, it creates waste (faeces) which the body pushes out through the rectum, anal canal and anus (a hole surrounded by a muscular ring). The colon’s role in the body is to get rid of water, some nutrients and electrolytes from the digested food. The colon is the area that exchanges liquid to solids and then transported to the rectum.The small intestinesThe small intestine has the main role in digestion which looks like a coiled tube with three parts- duodenum, jejunum and ileum. This also links up with the oesphagus, large intestine, and the stomach which forms the gastrointestinal tract. The internal walls of the small intestine consist of many tiny finger-like tissues called villi which all contains capillaries in which most of all the food gets absorbed. Each and every one of the villi is covered in even smaller finger-like structures called microvilli in which both villi and microvilli help increase surface area for the absorption of nutrients A lymph vessel called a lacteal absorbs recombined fat particles. Any remaining semi-liquid waste mixture passes into the large intestines.The liverThis is the largest organ which is located in the upper right portion of the abdominal cavity, under the diaphragm and to the right of the stomach, the liver contains four lobes. The average adult liver weighs about three pounds.One of the many roles this organ plays in consists of being a digestive gland which secretes bile along the hepatic duct. One other role is it converts and store newly- digested food matter which comes from the hepatic portal vein. Overall, this help regulates the level of blood glucose and in destroying old red blood cells. Also, stores vitamins and iron and creates important blood proteins.This is a vital organ as it supports nearly every organ in the body so without this, humans won’t be able to survive. It is known as a gland because it secretes chemicals such as bile- a substance which digest fats. Bile’s has salts which breaks down fat into smaller pieces so it is easier to get absorbed in the small intestine.In addition to the production of bile, comes the liver. This detoxifies the blood by getting rid of harmful substances such as alcohol and drugs. And also, breaks down hemoglobin as well as insulin and other hormones. It converts ammonia to urea which is vital in metabolism.The ovariesThis is a ductless reproductive gland in which the female reproductive cells are produced. It is held in place in the lower abdomen by ligaments. These helps attach them to the pelvic walls. The female sex cells called ova are being produced regularly in the ovaries right after puberty. An ovary is normally firm and smooth and is about the size of an almond.The female reproductive systems consist of a vulva, ovarian follicles uterus and the vagina. The vulva comes in the outer parts of the female reproductive system including the labia and the clitoris. The labia are two folds of skin which surrounds the openings of the vagina and the urethra. The clitoris is the most sensitive part and like the penis, it is made of erectile tissue which has many receptors. The ovarian follicles are areas of tissue which appears regularly in the ovaries after puberty hits. Each has a maturing ovum and the follicles gradually increase in size which then secretes hormones. The uterus consists of the making of the baby. Lastly, the vagina is a muscular canal leading from the uterus out of the body. It carries the ova and endometrium during menstruation. It has a lining of mucous membrane covering a muscular wall with a vast number of blood vessels.The kidneysThese are two bean-shaped organs that extract any waste from blood; balances body fluids, form urine and help other important functions of the body. They are located against the back muscles in the upper abdominal cavity and sit opposite each other on either side of the spine. The right kidney sits a little bit lower than the left to accommodate the liver.The urinary system is the main system of body parts involved in excretion, which gets rid of unwanted substances. Kidneys are the main two organs in excretion filter out unwanted substances from the blood and regulate the level of body fluids. Blood enters through the renal artery and leaves it in renal vein. Furthermore, there are many things the body doesn’t need inside which the kidneys filter out such as excess salts, and urea, a nitrogen- based waste created by cell metabolism. Urea is synthesised in the liver which transfers through the blood to the kidneys to get removed.More on the core actions of the kidneys include in balancing the level of water. As kidney’s role is to break down chemicals from urine, they react to any changes in the body’s water level throughout the day. When the water level decreases, the kidneys adjust accordingly and leave water in the body instead of helping excrete it. This also regulates the blood pressure because kidneys need constant pressure in order to filter the blood so when it drops too low, the kidneys increase the pressure. A way it does this is by producing a blood vessel constricting protein which signals the body to retain sodium and water. Both constriction and retention help restore normal blood pressure.The kidneys also help regulate red blood cells so when the kidneys have a lack of oxygen, it sends a message in the form of erythropoietin, a hormone that stimulates the bone marrow to produce more oxygen-carrying red blood cells. Lastly, it regulates acid so as cells metabolises, it produces acids. The food that we consume can either increase the acid in our body or neutralises it. The body needs a stable balance of chemicals in order for it to function properly which the kidneys also do.They are endocrine glands which produce a vast number of hormones including adrenaline and the steroids aldosterone and cortisol.A part of the kidney where ultrafiltration occursNnnnnnnnnnnn It is the innermost part of the kidneyThe two tubes which carries urine from the kidneys to the bladderIt carries blood from the heart to the kidneysThey are veins that drain the kidney and also carry filtered bloodThe testesThey are the most vital organs of the male reproductive system. They are glands where sperm and testosterone are produced. The testes lie in a sac which is located below the abdomen. They are contained in the scrotum and have a vast variety of dense connective tissue which contains around three hundred internal compartments called lobules. Each of these lobules contain a number of colled, tiny tubules where the sperm are produced. Testosterone is produced in cells located in between the lobules.The penis is the organ through which sperm are ejected during sexual intercourse. It is made of soft, sponge-like erectile tissue, which has many spaces, blood vessels and nerve fibre endings. When a man gets sexually excited, the sinuses and blood vessels fill with blood making it stiff and erect.The UterusThis is a hollow organ which is located inside, between the bladder and the rectum, in the pelvic area. Its role is to help develop the foetus and nourish it prior to birth. During menstruation, women releases eggs that travels through the fallopian tubes to the uterus. If fertilised, the eggs will bind themselves to the wall of the uterus in which the foetus can be developed. The uterus help nourishes and protect the foetus until birth.                        The Circulatory SystemThe circulatory system is a network of blood vessels, of which there are three main parts which are the arteries, veins and capillaries. Endothelium is a thin tissue layer which lines the arteries and veins and is the only layer of capillary walls. Blood continuously flow one way which is by the pumping of the heart, by muscles in artery and vein walls and by a decrease in pressure through the system.The heart, blood vessels and blood itself are the three most vital components our body needs to survive. The system consists of two circuits in which blood can travel through and these are pulmonary and systemic. Activities such as exercises can affect the systems which cause the heart to pump blood faster around the body which as a result you can exercise for longer.The circulatory system carries blood and of any dissolved substances to and from different places in the body. The heart has a role of pumping these things around the body and it pumps blood and substances through tubes called blood vessels. The heart and blood vessels work together which makes up the circulatory system.The system is a double circulatory system which means it has two parts. The pulmonary circuit carries blood to the lungs to get renewed (oxygenated) and then back to the heart. In the lungs, carbon dioxide gets removed out of the blood and exchanges it into oxygen by the haemoglobin which is found in red blood cells. However, the systemic circuit carries blood around the body to deliver oxygen and gives back de-oxygenated blood to the heart. Blood can also carry nutrients and waste.The heart contains veins which brings blood from the body but the lungs. The arteries in the heart carry blood away from the arteries whereas the coronary arteries supply its own blood. The heart is a muscular pumps so when it beats, it pumps the blood to the lungs and around the body.The heart has four chambers which consist of two atria and two ventricles. Blood enters the heart through the two atria and exits through the two ventricles. There are valves which prevent the blood from flowing in the wrong direction and the septum separates the two sides of the heart.There are three types of blood vessels in the body which are the arteries, veins and capillaries. The arteries carry blood away from the heart, have a thick muscular wall and have a small passageway for blood which also contains blood under high pressure. The veins can carry blood to the heart, have thing walls, contain blood under low pressure and have valves to prevent blood flowing backwards. The capillaries are found in the lungs and muscles, are microscopic and very low blood pressure. This is also where gas exchange takes place so when oxygen passes through the capillary wall and into the tissues, carbon dioxide passes from the tissues into the blood.Our blood is essential for the body which consists of four key components which are plasma, red and white blood cells and platelets. An average adult can hold up about 5.5 litres which travels around in the circulatory system. The blood distributes heat and carries many more important components in its plasma. The old blood gets replaced by new ones through the process called haemopoiesis.Plasmas are pale liquid which contains the red blood cells and it carries dissolved food for the body cells, waste matter and carbon dioxide are secreted by them, antibodies which combat infection and enzymes and hormones help with the body process. Red corpuscles other known as red blood cells are a red, disc-shaped without a nucleus. They are created in the bone marrow which also contains haemoglobin which gives it its dark red colour. When this is mixed with oxygen in the lungs, it forms oxyhaemoglobin which makes the blood darker. The red cells pass the oxygen to body cells by diffusion and then return back to the lungs with haemoglobin. The white blood cells are large and are an important part of the immune system which produces antibodies and kill of any harmful microorganisms. Platelets are very small disc-shaped bodies which are also made in the bone marrow. These clumps together to form clot and protect the body by stopping blood lost. It transports nutrients and waste, delivers oxygen to the working muscles and removes heat.The respiratory SystemThe human respiratory system is split into two parts, one being the lower and the other being the upper respiratory tract. When you breathe in, the air is already filtered through natural lines of defense which protects the respiratory tract from any illnesses or irritation. Nasal hairs in nose are there to protect any large particles of dust that might get inhaled the respiratory and so are the rest of the system is lined with mucous membrane which secretes mucous. The mucous help trap any small particles such as pollen or smoke. Cilia are like hairs and these lines the mucous membrane and move the particles that were trapped in the mucus out of t