The cardiovascular system, also called the circulatory system, pumps blood around the body. The right side of the heart pumps deoxygenated blood to the lungs where oxygen diffuses into the blood, it then returns to the heart where it is pumped around the body. It also allows nutrients, hormones, oxygen and carbon dioxide to be transported around the body.
Heart:
The heart is made up of three layers: * Pericardium – the outer layer of the heart made of two fibrous sacs with fluid between them. It is there to protect the heart and prevent friction between the different beats as well as preventing distension of the heart. * Myocardium – is a specialist cardiac muscle and does not have control over itself. It contains a network of fibres that transmit the hearts electrical signals causing the heart to contract. The myocardium at its thickest at the apex of the heart and it thins towards the base in accordance to the workload that the heart undertakes. There is fibrous tissue running through it providing support as well as the specialist fibres that conduct the electrical signals. * Endocardium – the endocardium is a smooth epithelial tissue that allows a rapid movement of blood, it extends through all the vessels in the circulatory system.
The heart is made up of four chambers. The septum divides the two sides of the heart and on each side of the heart there is an atrium – where blood goes into – and a ventricle – where blood is pumped out of. The superior vena cava transports blood from the head and the inferior vena cava transports blood from the rest of the body. The pulmonary artery carries blood away from the heart and the pulmonary vein carries blood in to the heart. The tricuspid three flaps and prevents blood from flowing back the wrong way. The tendons that are attached prevents the valve from opening upwards. The bicuspid valve does the same job as the tricuspid valve but is only made of three flaps.
The right side of the heart collect de-oxygenated blood in the right atrium, it then trickles down into the right ventricle and is pumped into the lungs. Carbon dioxide then diffuses into the lungs and is exhaled while oxygen is diffused into the blood, this process is gaseous exchange.
The left side of the heart collects the oxygenated blood from the lungs. It is pumped around the body to the cells in order for them to respire.
Blood vessels:
Blood is used to transport materials around the body as well as protecting the body against infection. The blood is made up of four different components * Plasma – is 90%, 10% proteins, minerals, hormones, food, waste and a small amount of carbon dioxide. * Red blood cells – containing haemoglobin which transports oxygen and carbon dioxide. * White blood cells * Red blood cells
There are three main types of vessels that blood flows through * Arteries * Veins * Capillaries
Arteries carry the oxygen-rich blood away from the heart to the cells in body tissues. They have relatively thick walls as they have a high amount of blood running through them.
Veins have thinner walls than arteries. They transport blood from the body to the heart at a low pressure. Like the heart, veins have valves to stop the backflow of blood.
Capillaries have very thin walls (one cell thick) to allow the diffusion that takes place in gaseous exchange to occur. A capillary bed is found in the lungs so that more diffusion can take place.
Respiratory
Respiration:
Oxygen + Glucose Energy + Carbon Dioxide
Respiration is the process where energy is released, the energy is produced by eating food and taking in oxygen.
Gas Exchange:
The delivery of oxygen from the lungs into the bloodstream and the removal of carbon dioxide.
The process of respiration includes the inhalation of oxygen, the oxygen has to go through many different components for gas exchange to take place:
Nose and Mouth
Pharynx
Larynx
Trachea
Bronchi
Bronchioles
Alveoli
Nose, mouth, nasal cavity:
This part of the system has the function to take in, warm, filter and moisten the incoming air.
Pharynx:
The throat divides into the trachea -windpipe, and the oesophagus -food pipe. There is a small flap over the top of the trachea made of cartilage called the epiglottis, this prevents any food from entering the same pipe that air travels down.
Larynx:
The larynx is also known as the voice box as it the same place that sound is generated. It helps protect the trachea by creating a cough reflex to prevent any solid objects from passing the epiglottis.
Trachea:
The trachea has an inner membrane that is covered in cilia to catch any infections that are trying to get into the body which are then removed by coughing. It is supported by c-shaped rings of cartilage that hold it upright and open allowing air to travel down into the bronchi.
Bronchi:
This is another pipe that air passes through to reach the lungs.
Bronchioles:
This is where the bronchi divide into two and get smaller. There is no cartilage in this stage of the system as this is where air passes through into the alveolar sacs.
Alveoli:
The alveoli are the individual hollow cavities in the alveolar sacs. They have very thin walls (one cell thick) so that gaseous exchange can occur easily. They are surrounded by many capillaries, again aiding gaseous exchange.
Diaphragm and intercostal muscles:
The diaphragm is a wide band of muscle under the lung, attached to the lower ribs, sternum and lumbar spine. The intercostal muscles are muscles that run in between the ribs. They are both there to support the lungs and ribs when breathing in and out. The diaphragm moves down and the ribs move up and out when inhaling in order to lower the pressure in the thorax so that air moves in to the lungs. When exhaling the diaphragm moves up and the ribs and intercostal muscles move in and down in order to make the pressure higher in the thorax so that air is forced out of the lungs.
Lungs:
The lungs allow for respiration to occur by facilitating oxygen entering into the bloodstream so that all living cells in the body can respire. The lungs are a large pair of spongy organs that are optimised for gaseous exchange by being filled with many alveoli as they are the site where oxygen diffuses into the blood and carbon diffuses out of the bloodstream. The lungs are surrounded by a double-membrane which includes a cavity that allows the lungs to expand during inhalation. The membrane is lubricated to prevent the lungs from becoming irritated during the act of breathing.
The lungs occupy the majority of the thoracic cavity, the base of the them being concave to fit the shape of the diaphragm. As 2/3 of the heart is situated on the left side of the body the left lung is slightly smaller than the right, it also contains a slight indentation where the apex of the heart sits. Each lung contains lobes that are separated by fissure tissues.
Running through the lungs there is a high concentration of oxygen in the blood from the heart so that there is a high concentration gradient forcing diffusion of oxygen into the blood going round the body. There is also a high concentration of carbon dioxide in blood from the body so that diffusion is forced and carbon dioxide diffuses into the lungs to be forced out.
Digestive
The organs in the digestive system work together to turn food into nutrients for the body to use. The breaking up of food begins in the mouth where the saliva contains enzymes to help break food down into smaller, more manageable pieces. It then enters the oesophagus and makes its way through the body, the nutrients that the body being drawn out and entering the bloodstream and waste product leaving the body.
Oesophagus:
The oesophagus is a long thin tube made of muscle that connects the throat to the stomach. It forms part of the gastrointestinal tract and is allows food swallowed to move from the throat into the stomach. The upper oesophagus sphincter only opens when swallowing food, the lower oesophagus sphincter then opens to allow food to pass through to the stomach. The lower sphincter prevents and acid from the stomach from entering and damaging the oesophagus, when the sphincter is weakened acid may enter the oesophagus and cause an acid reflux.
The oesophagus is made of four different layers of tissue: * The outer layer covers loose connective tissue around the oesophagus and loosely connects it to surrounding organs. * The next layer in is the muscularis layer, this is what allows the oesophagus to contract and expand to push food down into the stomach. In the superior part of the oesophagus skeletal muscle is found to aid in the swallowing of food where as smooth muscle is found in the inferior (lower) region of the oesophagus as it aids in the wave-like contractions that pushes substances down the oesophagus into the stomach. * The submucosa layer is the second layer into the oesophagus. This contains connective tissues and provides a network of nerves as well as blood to the tissue layers. * The innermost layer is the mucosa. This is the only layer of tissue that comes in to contact with the substances that are passing through the oesophagus. The majority of the mucosa layer is made of squamous epithelial cells that protect the oesophagus from any rough pieces of food as well as any acid that may enter the tube. The oesophagus is lubricated by the mucus produced by some cells in the inner layer; this mucus also aids the protection of the oesophagus from any acid from the stomach that may happen to pass the lower sphincter.
As well as the important function of swallowing food and allowing it to pass to the stomach the oesophagus is involved in the vomiting reflex. Vomiting occurs to void the body of any toxins or pathogens that enter the body through food and happen to be in the stomach. When this happens the wave-like contractions that push food down the oesophagus are reversed and push the toxins back up the tube and into the mouth to be expelled.
Stomach:
The stomach is used as a main ‘storage’ site for food that enters the body. The stomach has a large capacity allowing us to eat regularly. The stomach contains digestive enzymes that further breaks down food particles. The acid in the stomach also helps kill any bacteria and pathogens that are in the food.
The stomach is a large round cavity that can be separated into four different regions: * The oesophagus connects to the stomach at the cardia, this is a small narrow pipe that opens into the wider part of the stomach. The top of the cardia contains the lower oesophagus sphincter, this expands to allow food into the stomach and contracts to hold the food in. * The body of the stomach is where the cardia empties food into. This is the largest part of the stomach. * The fundus is a dome shaped part of the stomach. The cells in this region of the stomach secrete the enzymes that break down food further as well as contracting to aid the further break down of the food particles. * The pylorus is a funnel shaped region of the stomach that contains a pyloric sphincter, controlling the flow of partially digested food from the stomach into the duodenum.
Like the oesophagus the stomach is surrounded by four layers of tissue. * The outermost layer is a thin membrane made of simple epithelial and areolar cells. It has a smooth surface that secretes a watery liquid to prevent the stomach from getting irritated by friction when it expands and contracts. * The next layer in is the muscularis layer. This makes up a lot of the mass of the stomach being made up of three layers of smooth muscle with a network of fibres. This layer allows the stomach to expand and contract to aid in the breaking down of food particles as well as pushing food down the digestive tract. * The submucosa layer is the next layer in and is made up of nerves, connective tissue and blood vessels. The connective tissues support the tissues and the blood vessels allow nutrients to be supplied to the stomach wall. The nervous tissue monitors the stomach content and controls the smooth muscle contractions and the secretions of digestive substances. * The inner layer is mucosa layer, it contains folds in the membrane to increase the surface area that is in contact with the food in the stomach. The cells in this layer secrete digestive enzymes that break the food particles down. The mucosa in the stomach is much thicker than that in other organs in the digestive system as it contains pits that secrete the digestive substances.
To help break food particles down there are two types of digestion that occurs in the stomach: * Chemical digestion – the stomach secretes several important substances to help the breakdown of food. This includes hydrochloric acid and digestive enzymes; this works together with the mechanical digestion to breakdown large food particles into smaller soluble units. This prepares the particles for further digestion in the intestines where chemical digestion is complete. Different substances secreted by the stomach are used to breakdown different types of food: * Gastric lipase breaks down fatty acids and triglycerides into smaller subunits of diglyceride. * Pepsin breaks down proteins into soluble amino acids. * Gastric lipase breaks down fatty acids and triglycerides into smaller subunits of diglyceride. * Pepsin breaks down proteins into soluble amino acids.
* Mechanical digestion – the smooth wall in the stomach contracts and expands in mixing waves to mix food with the substances that the stomach secretes so that they work together to break food particles into smaller soluble units.
Liver:
The liver is roughly triangular and extends across the abdominal cavity. It contains bile ducts that carry bile through the liver to the gallbladder. The bile that the liver produces is stored in the gallbladder and then secreted into the small intestine when it is needed to emulsify fats.
As well as being responsible for the production of bile the liver also takes away any unwanted particles that are in the bloodstream when passing through the liver. The liver acts a chemical plant within the body, it takes the raw nutrients that are absorbed in the small intestine and processes them into the chemicals that the body requires.
The liver is made of soft tissues that are encapsulated by a layer of connective tissue, this is then protected by the peritoneum of the abdominal cavity which connects the liver in the coronary ligament, falciform ligament and left and right triangular ligament; these are not true connections but are there to support the liver.
Pancreas:
The pancreas produces insulin which is secreted straight into the bloodstream, this is used in the body for stabilising sugar levels by metabolising sugar. As well as the production of insulin the pancreas also secretes digestive substances into the small intestine to breakdown fats, proteins and carbohydrates.
The exocrine part of the pancreas plays a major role in the digestion of food as it secretes many of the digestive enzymes that are used to break down food in the duodenum. Each enzyme that the pancreas secretes is specialised to break down a particular type of food: * Amylase breaks down polysaccharides into smaller sugars. Some of these sugars are then broken down more into monosaccharides that can be absorbed by the body. * Trypsin, carboxypeptidase and chymotrypsin are enzymes that digest proteins, breaking them down into their subunits that the small intestine can absorb. * Pancreatic lipase breaks large triglycerides into smaller fatty acids and monoglycerides. The breaking down of these fats is aided by the bile that is produced by the liver as it emulsifies them, increasing their surface area meaning there is a higher amount of contact with the enzymes. * Ribonuclease and deoxyribonuclease breaks down RNA into the sugar ribose and the nitrogenous bases.
The pancreas is made up of glandular tissue making it a lose structure. The tissue surrounds small ducts all over the pancreas that drain into the pancreatic duct that carries digestive enzymes into the duodenum.
Duodenum
The duodenum is the first section of the small intestine, it plays a vital role in the final stage of chemical digestion, breaking down the partially digested food in order for the small intestine to absorb the nutrients. It is a small hollow tube attached to the pyloric sphincter of the stomach.
Digestive secretions are delivered to the duodenum from the stomach, pancreas and gallbladder where they are then broken down further before entering the small intestine.
The four layers of tissue around the duodenum are consistent with that of the stomach. The Brunner’s gland in the mucosa secretes an alkaline mucus that neutralises the partially digested food after sitting in the hydrochloric acid in the stomach for thirty to sixty minutes. This protects the walls of the duodenum meaning it can break down the food particles in the same way as other organs before they enter the small intestine.
Small intestine:
The small intestine is made up of three regions: * Duodenum – where chime (partially digested food) is broken up in preparation for absorption in the small intestine. * Jejunum – the primary site of nutrient absorption. * Ileum – completes the absorption that the jejunum misses and empties into the large intestine.
The small intestine has the same four layers of tissue as the stomach. Once nutrients are absorbed they are then passed into blood and lymphatic vessels and taken to the liver where they are processed into chemicals for use in the body. Fatty acids only enter the lymphatic vessels and are carried back into the blood supply.
Colon/large intestine:
The colon plays an important role in absorbing vitamins and water and converting waste into faeces.
The four tissue layers are again consistent with those of the stomach but are much thicker and have many folds making the surface area of the colon very large.
When digested food enters the colon water is reclaimed as well as any vitamins, this then enables waste to be produced. The absorption of water allows faeces to be solidified and condensed ready for being expelled by the body. This also allows the body to retain the water for use in other chemical reactions.
Anus:
The final part of the gastrointestinal duct. It is a short tube that allows faeces to pass out of the body. The tissues lining changes to stratified squamous epithelial cells. There are two sphincters, the inside and exterior, these surround the anus to control the passing of faeces. It plays an important role in controlling the expelling of solid waste. The sphincters prevent defecation by holding faeces in the rectum, when pressure is put onto the rectal walls signals are sent to the brain which causes signals to be sent to the internal anus sphincter, faeces are held until voluntary signals are sent to relax the sphincters during the defecation reflex.
Renal System:
The renal system is responsible for producing, storing, secreting and eliminating urine, the waste product produced by the kidneys. It also works with the skin, lungs and intestines to maintain the balance of chemicals and water in the body.
Kidneys:
The kidneys are located just below the ribcage in the middle of the back. They remove the waste product that’s formed by the breakdown of proteins, the urea is forced with the blood through nephrons – a bunch of capillaries and a small renal tubule. Urea, along with other waste substances and water forms urine as it passes through the nephrons and down the tubules. Urine travels from the kidneys down to the bladder in ureters which are thin tubes about 8-10 inches’ long. The muscles in the ureter walls tighten and relax to force the urine way from the kidneys. Small amounts of urine are emptied from the ureters into the bladder around every 10-15 seconds.
The kidneys are a bean-shaped pair of organs, one side of each kidney is concave, the indentation is there to provide space for the renal veins and arteries. There is a thin layer of connective tissue around each of the kidneys to provide support in keeping the soft organ’s shape. There are around one million nephrons in each kidney, these are responsible for filtering the blood to produce urine.
Bladder:
The bladder is a balloon shaped, hollow organ located in the pelvis. It stores urine until it is signalled by the brain that it needs to be emptied. There are external and internal sphincters that hold the urine in place until sent signals to relax and let the urine pass, via the urethra.
The bladder is made up of several layers of tissue: * The outermost layer is the visceral muscles. These allow the bladder to expand and contract. It also forms the internal urethral sphincter which relaxes during the passing of urine. * The middle layer is the submucosa, a layer full of connective tissues and nerves providing support and controlling the other tissues. * Mucosa is the innermost layer, unlike other organs in the bladder the mucosa is lined with transitional epithelial tissue providing protection and giving the bladder the ability to stretch and expand to accommodate a large volume of urine.
Nervous system:
The nervous system is a diverse network of nerves and specialised cells (neurones) that transmit signals between different parts of the body. It consists of: * The central nervous system (CNS) – the brain and the spinal cord * The peripheral nervous system – nerve cells that carry information to and from the CNS
Brain:
The cells in the brain can be divided into two different groups: * Neurons – nerve cells. Sensory neurons that enter the brain deliver information from the peripheral nervous system. The interneurons are responsible for the processing of information delivered to the brain by sensory neurons. Motor neurons deliver signals sent by the interneurons to the muscles and glands. * Neuroglia - act as the brain’s ‘helper’ cells. They support and protect the neurons.
The brainstem connects the brain to the spinal cord. Large volumes of blood must be sent to the brain in order for it to maintain a proper working function.
The brain receives information about the body’s surroundings and condition, the brain then sends signals to react to these stimuli’s. Some reactions are reflexes and do not require to go through the whole process of beings sent to the spinal cord then to the brain, back to the spinal cord and into the body as they need to happen urgently, for example if a person put their hands over a flame they move their hand away as a reflex in order not to get burnt.
The brain controls all bodily movements, sending signals to muscles to contract and relax, allowing us to move. These signals are subconscious – we do not think about them as our brain does the work automatically. Spinal cord:
The spinal cord forms the fundamental link between the brain and the body. It is divided into 31 segments: * 8 cervical segments in the neck * 12 thoracic segments * 5 lumber segments in the lower part of the back * 5 segments in the pelvis * 1 segment making up the tailbone
Each segment of the spinal cord contains a pair of nerves that exit the spinal cord at the intervertebral foramina and go into the body. This is where signals from the brain are sent into the body.
Endocrine
The endocrine system is responsible for the production and secretion of hormones in the body. It is made up of glands as well as organs.
Pituitary gland:
The pituitary gland is a very small gland located in the centre of the skull. It is surrounded by blood vessels that transport the hormones it produces and secretes to the relevant place in the body. It responsible for producing several major hormones: * Human growth hormone * Thyroid stimulating hormone * Follicle stimulating hormone * Luteinising hormone * Prolactin * Adrenocorticotropic hormone * Melanocyte stimulating hormone
Thyroid gland:
The thyroid gland is a small butterfly shaped gland that covers a part of the pharynx in the neck. This controls the rate at which the body uses nutrients for energy by secreting hormones that regulate energy and emotional balance. The main hormones that the gland produces are triiodothyronine and thyroxine, the amount of these hormones that are secreted are controlled by the thyroid stimulating hormone that is secreted by the pituitary gland.
Testes:
A circular pair of glands that are mainly used in the male reproductive system. They are responsible for releasing testosterone as well as releasing sperm.
Ovaries:
The ovaries are a small gland in the female pelvic cavity. They play a central role in the female reproductive system as they produce oestrogen and progesterone. These hormones control the releasing of an egg from the ovaries as well as controlling the lining of the uterus.
Hypothalamus:
The hypothalamus us made up of a cluster of cells just above the pituitary gland. It sends messages to the body from the brain and is used to link the nervous system to the endocrine system using the pituitary gland.
Pancreas:
The pancreas is a glandular organ that sits in the upper abdomen. It produces and secretes many enzymes that aid the chemical digestion of food: * Pancreatic amylase – breaks down polysaccharides into smaller monosaccharide sugars that the small intestine can absorb. * Trypsin, chymotrypsin, and carboxypeptidase – breaks down proteins into smaller amino acid units that the small intestine can directly absorb. * Pancreatic lipase – breaks down triglyceride fats into smaller fatty acids and monoglycerides, these are emulsified by bile so that they can be broken down further. * Ribonuclease and deoxyribonuclease – digest nucleic acids into their nitrogenous bases.
As well as these enzymes the pancreas is also responsible for maintaining the levels of glucose in the bloodstream; this is regulated by the hormone insulin that that the pancreas produces and secretes.
The pancreas is made up of glandular tissue, giving it a loose structure. Tissue surrounds many ducts that drain into the main pancreatic duct that carries digestive enzymes to the duodenum.
Adrenal:
Adrenal glands are situated in the top portion of each kidney. They release hormones that are fundamental to the body functioning: * Cortisol – regulates blood pressure, cardiovascular and the way that foods are broken down. * Corticosterone – works with cortisol to regulate the immune system and supressing inflammation.
Both hormones also contribute to the way that the body responds and copes with stress.
The adrenal gland releases the hormones directly into the bloodstream. They can be divided into different regions: * The adrenal cortex – the outer layer of the gland that releases hormones into the body. * The adrenal medulla – the inner region that is part of a sympathetic nervous system, the first line of defence on stress (both emotional and physical).
Reproductive
The reproductive system differs in male and female anatomy. The two different reproductive systems both produce the hormones that are required for the reproduction process. For an embryo to be formed an egg from the female system needs to be fertilised by sperm that’s produced in the male reproductive system.
Female
Ovaries:
The ovaries are a small pair of glands in the pelvic cavity. They are repsonible for the production of oestrogen and progesterone, controlling the releasing of an egg and the lining of the uterus.
Uterus:
Aso known as the womb, is a muscular organ that carries the embryo during pregnancy. It is responsible for the devlopment of the embryo throughout the pregnancy. It contracts during birth to help push the embryo down the birth canal and out through the vagina. A fertilised egg has to implant itself on to the lining of the uterus to allow it to develop.
Female
Ovaries:
The ovaries are a small pair of glands in the pelvic cavity. They are repsonible for the production of oestrogen and progesterone, controlling the releasing of an egg and the lining of the uterus.
Uterus:
Aso known as the womb, is a muscular organ that carries the embryo during pregnancy. It is responsible for the devlopment of the embryo throughout the pregnancy. It contracts during birth to help push the embryo down the birth canal and out through the vagina. A fertilised egg has to implant itself on to the lining of the uterus to allow it to develop.
Male
Testes:
Also known as testicles, the testes are a pair of glandular organs that are responsible for the production of sperm. They are located in the hollow scrotum. The scrotum regulates the temperature meaning that sperm are allowed to mature for seventy-two days. They are located outside the body as it is too hot inside the body for sperm to be effective. Male
Testes:
Also known as testicles, the testes are a pair of glandular organs that are responsible for the production of sperm. They are located in the hollow scrotum. The scrotum regulates the temperature meaning that sperm are allowed to mature for seventy-two days. They are located outside the body as it is too hot inside the body for sperm to be effective.
Lymphatic:
The lymphatic system is made up of three components: * Lymph fluid – a clear-white fluid made up of white blood cells, lymphocytes, the cells that make protect from the body from pathogens in the bloodstream. It also contains molecules of proteins and fats. * Lymphatics – a vessel that transports lymph fluid around the body. * Structures and organs
The functions of the lymphatic system are: * To return tissue fluid back into the bloodstream * Detect and attack any pathogens that enter the body * Carry fats from the digestive system to the bloodstream
Spleen:
The spleen is the largest lymphatic organ situated between the stomach and diaphragm. It regulates the amount of red blood cells present in the body. When the spleen detects a potential threat to the body it creates lymphocytes which produce antibodies to kill the infection. The spleen also filters and stores blood ready to send out white blood cells when a harmful substance enters the bloodstream.
The spongy inner tissue of the spleen is packed with blood vessels and hollow gaps that hold blood. A robust connective tissue surrounds the soft tissue inside the spleen. The ribs protect the spleen.
Thymus:
The thymus us situated above the heart in the chest. It stores the immature lymphocytes and prepares them to become active t-cells, used in fighting infection. T-cells that are produced by the bone marrow are then stored in the cortex where they come into contact with epithelial cells that present antigens, the immature t-cells then react to the corresponding to the foreign cells, mature and migrate to the medulla while the weaker t-cells die and are removed by macrophages.
The thymus is a soft triangular-shaped organ. It contains two lobes that are surrounded by a tough fibrous layer. The two lobes are identical to each other; they have a soft tissue cortex surrounded by the medulla. Both regions of the lobes contain epithelial tissues and lymphatic tissues.
During puberty the thymus gland as its largest size but decreases when puberty has taken place and an individual reaches full maturation.
Tonsils:
Tonsils are several groups of large lymphatic nodules that sit at the back of the throat in mucous membrane of the oral and pharyngeal cavities: * Palatine tonsils – tonsils situated in the lateral posterior walls of the pharynx behind the mouth. * Pharyngeal tonsils – tonsils located in the later walls in the pharynx behind the nasal passages. * Lingual tonsils – tonsils located at the base of the tongue.
The tonsils act as a first line of defence against bacteria entering the body through the mouth and nose. They trap pathogens and produce antibodies to destroy them to prevent the body from becoming infected.
Tonsils have the structure of other lymph nodes, an outer cortex that produces lymphocytes and an inner medulla that contain many medullary cords. Lymph fluid enters the nodes, flows through sinuses and exits through a lymphatic vessel.
Muscular-skeletal
The muscular skeletal system is made up of 206 bones and over 600 muscles. The function of the system is to keep the body supported and upright and also to allow the body to move. If there weren’t muscles in the body, there would be no movement at all and the body would be stiff and rigid. The bones and muscles in the body to stand and be upright.
Bones:
The bones support the body and protect the soft organs of the body, they move at joints due to the skeletal muscles that are attached. Bones also act as a storage place for minerals and fats as well as producing blood cells. There are two basic types of bone: * Compact bone – makes up around 80% of the bone in the body * Spongy bone – small needle-like pieces of bone that have many open spaces.
Bones meet at joints; most joints are moveable. An oily synovial fluid lies between the bones in a joint. Bones are held to the joint by ligaments. When bones are joined to muscles they are joined by tendons.
Muscles:
It is due to the relaxing and contracting of muscles that the body is able to move. They are also responsible for maintaining the body’s posture.
Most of the muscles are in the body are attached to two bones by tendons, when the muscle contracts another bone is pulled towards the other, this could be the bending of an arm or leg for example. Most of the time these muscles work in groups, for example in the arm there are two muscles in the upper arm and two in the forearm that all work together at a precise moment to make the arm bend.
There are three types of muscle: * Visceral – a muscle found in structures like the stomach, blood vessels and small intestines. This muscle tissue causes organs to contract to move substances through them. It is often described as smooth muscle and is the weakest of the three types of muscle tissue. * Cardiac – only found in the heart. It is responsible for the pumping of blood around the body. It is an involuntary movement as it is not controlled by the brain. * Skeletal – the only voluntary muscle in the body. The function of skeletal muscle is to contract and relax when a person consciously thinks about moving.
Immune system
The immune system is made up of a system of cells, tissues and organs that work in conjunction with each other to protect the body against any potentially dangerous invasions (pathogens, virus, bacteria, etc.). One of the most important cells is white blood cells which locate and destroy a disease causing organism.
Skin:
The skin is the first line of defence, not allowing any disease causing organisms in to the body. If there are any cuts in the skin, it compromises the defence system as it allows a threat into the bloodstream. As well as the physical barrier that the skin provides there are also specialised cells throughout the layers in the skin. Some of these cells detect the disease causing organism and others have the function to destroy and remove it.
When a disease causing substance comes into contact with a cell from the immune system the cell produces a protein called an antibody that has a specific shape to the antigen on the substance, the antibody then locks onto the pathogen and stops it from invading any cells of the body or from reproducing. A chemical signal is also sent to the macrophages that come and remove the harmful substance.
Thymus:
The thymus us situated above the heart in the chest. It stores the immature lymphocytes and prepares them to become active t-cells, used in fighting infection. T-cells that are produced by the bone marrow are then stored in the cortex where they come into contact with epithelial cells that present antigens, the immature t-cells then react to the corresponding to the foreign cells, mature and migrate to the medulla while the weaker t-cells die and are removed by macrophages.
The thymus is a soft triangular-shaped organ. It contains two lobes that are surrounded by a tough fibrous layer. The two lobes are identical to each other; they have a soft tissue cortex surrounded by the medulla. Both regions of the lobes contain epithelial tissues and lymphatic tissues.
During puberty the thymus gland as its largest size but decreases when puberty has taken place and an individual reaches full maturation.
