Organs are groups of tissues with similar functions. Plant and animal life relies on many organs. Organs are composed of main tissue, "sporadic" tissues, stroma; the main tissue is that, unique for the specific organ, such as the myocardium, the main tissue of the heart, while sporadic tissues include the nerves, blood vessels, connective tissues. The main tissues that make up an organ tend to have common embryologic origins, such as arising from the same germ layer. Functionally-related organs cooperate to form whole organ systems. Organs exist in most multicellular organisms. In single-celled organisms such as bacteria, the functional analogue of an organ is known as an organelle. In plants there are three main organs. A hollow organ is an internal organ that forms a hollow tube, or pouch such as the stomach, intestine, or bladder. In the study of anatomy, the term viscus is used to refer to an internal organ, viscera is the plural form. 79 organs have been identified in the human body. In biology, tissue is a cellular organizational level between complete organs.
A tissue is an ensemble of similar cells and their extracellular matrix from the same origin that together carry out a specific function. Organs are formed by the functional grouping together of multiple tissues; the study of human and animal tissues is known as histology or, in connection with disease, histopathology. For plants, the discipline is called plant morphology. Classical tools for studying tissues include the paraffin block in which tissue is embedded and sectioned, the histological stain, the optical microscope. In the last couple of decades, developments in electron microscopy, immunofluorescence, the use of frozen tissue sections have enhanced the detail that can be observed in tissues. With these tools, the classical appearances of tissues can be examined in health and disease, enabling considerable refinement of medical diagnosis and prognosis. Two or more organs working together in the execution of a specific body function form an organ system called a biological system or body system.
The functions of organ systems share significant overlap. For instance, the nervous and endocrine system both operate via the hypothalamus. For this reason, the two systems are studied as the neuroendocrine system; the same is true for the musculoskeletal system because of the relationship between the muscular and skeletal systems. Common organ system designations in plants includes the differentiation of root. All parts of the plant above ground, including the functionally distinct leaf and flower organs, may be classified together as the shoot organ system. Animals such as humans have a variety of organ systems; these specific systems are widely studied in human anatomy. Cardiovascular system: pumping and channeling blood to and from the body and lungs with heart and blood vessels. Digestive system: digestion and processing food with salivary glands, stomach, gallbladder, intestines, colon and anus. Endocrine system: communication within the body using hormones made by endocrine glands such as the hypothalamus, pituitary gland, pineal body or pineal gland, thyroid and adrenals, i.e. adrenal glands.
Excretory system: kidneys, ureters and urethra involved in fluid balance, electrolyte balance and excretion of urine. Lymphatic system: structures involved in the transfer of lymph between tissues and the blood stream, the lymph and the nodes and vessels that transport it including the Immune system: defending against disease-causing agents with leukocytes, adenoids and spleen. Integumentary system: skin and nails of mammals. Scales of fish and birds, feathers of birds. Muscular system: movement with muscles. Nervous system: collecting and processing information with brain, spinal cord and nerves. Reproductive system: the sex organs, such as ovaries, fallopian tubes, vulva, testes, vas deferens, seminal vesicles and penis. Respiratory system: the organs used for breathing, the pharynx, trachea, bronchi and diaphragm. Skeletal system: structural support and protection with bones, cartilage and tendons; the study of plant organs is referred to as plant morphology, rather than anatomy – as in animal systems.
Organs of plants can be divided into reproductive. Vegetative plant organs include roots and leaves; the reproductive organs are variable. In flowering plants, they are represented by the flower and fruit. In conifers, the organ that bears the reproductive structures is called a cone. In other divisions of plants, the reproductive organs are called strobili, in Lycopodiophyta, or gametophores in mosses; the vegetative organs are essential for maintaining the life of a plant. While there can be 11 organ systems in animals, there are far fewer in plants, where some perform the vital functions, such as photosynthesis, while the reproductive organs are essential in reproduction. However, if there is asexual vegetative reproduction, the vegetative organs are those that create the new generation of plants. Many societies have a system for organ donation, in which a living or deceased donor's organ is transplanted into a person with a failing organ; the transplantation of larger solid organs requires immunosuppression to prevent organ rejection or graft-versus-host disease.
There is considerable interest throughout the world in creating laboratory-grown or artificial organs. The English word "organ" dates back in reference to any musical instrument. By the late 14th
Emergency medicine known as accident and emergency medicine, is the medical specialty concerned with the care of illnesses or injuries requiring immediate medical attention. Emergency physicians care for undifferentiated patients of all ages; as first-line providers, their primary responsibility is to initiate resuscitation and stabilization and to start investigations and interventions to diagnose and treat illnesses in the acute phase. Emergency physicians practice in hospital emergency departments, pre-hospital settings via emergency medical services, intensive care units, but may work in primary care settings such as urgent care clinics. Sub-specializations of emergency medicine include disaster medicine, medical toxicology, critical care medicine, hyperbaric medicine, sports medicine, palliative care, or aerospace medicine. Different models for emergency medicine exist internationally. In countries following the Anglo-American model, emergency medicine was the domain of surgeons, general practitioners, other generalist physicians, but in recent decades it has become recognised as a speciality in its own right with its own training programmes and academic posts, the specialty is now a popular choice among medical students and newly qualified medical practitioners.
By contrast, in countries following the Franco-German model, the speciality does not exist and emergency medical care is instead provided directly by anesthesiologists, specialists in internal medicine, cardiologists or neurologists as appropriate. In developing countries, emergency medicine is still evolving and international emergency medicine programs offer hope of improving basic emergency care where resources are limited. Emergency Medicine is a medical specialty—a field of practice based on the knowledge and skills required for the prevention and management of acute and urgent aspects of illness and injury affecting patients of all age groups with a full spectrum of undifferentiated physical and behavioral disorders, it further encompasses an understanding of the development of pre-hospital and in-hospital emergency medical systems and the skills necessary for this development. The field of emergency medicine encompasses care involving the acute care of internal medical and surgical conditions.
In many modern emergency departments, emergency physicians are tasked with seeing a large number of patients, treating their illnesses and arranging for disposition—either admitting them to the hospital or releasing them after treatment as necessary. They provide episodic primary care to patients during off hours and for those who do not have primary care providers. Most patients present to emergency departments with low-acuity conditions, but a small proportion will be critically ill or injured. Therefore, the emergency physician requires a broad field of knowledge and procedural skills including surgical procedures, trauma resuscitation, advanced cardiac life support and advanced airway management, they must have some of the core skills from many medical specialities—the ability to resuscitate a patient, manage a difficult airway, suture a complex laceration, set a fractured bone or dislocated joint, treat a heart attack, manage strokes, work-up a pregnant patient with vaginal bleeding, control a patient with mania, stop a severe nosebleed, place a chest tube, conduct and interpret x-rays and ultrasounds.
This generalist approach can obviate barrier-to-care issues seen in systems without specialists in emergency medicine, where patients requiring immediate attention are instead managed from the outset by speciality doctors such as surgeons or internal physicians. However, this may lead to barriers through acute and critical care specialties disconnecting from emergency care. Emergency medicine can be distinguished from urgent care, which refers to immediate healthcare for less emergent medical issues, but there is obvious overlap and many emergency physicians work in urgent care settings. Emergency medicine includes many aspects of acute primary care, shares with family medicine the uniqueness of seeing all patients regardless of age, gender or organ system; the emergency physician workforce includes many competent physicians who trained in other specialties. Physicians specializing in emergency medicine can enter fellowships to receive credentials in subspecialties such as palliative care, critical-care medicine, medical toxicology, wilderness medicine, pediatric emergency medicine, sports medicine, disaster medicine, tactical medicine, pain medicine, pre-hospital emergency medicine, or undersea and hyperbaric medicine.
The practice of emergency medicine is quite different in rural areas where there are far fewer other specialties and healthcare resources. In these areas, family physicians with additional skills in emergency medicine staff emergency departments. Rural emergency physicians may be the only health care providers in the community, require skills that include primary care and obstetrics. Patterns vary by region. In the United States, the employment arrangement of emergency physician practices are either private, corporate, or governmental
Internal bleeding is a loss of blood from a blood vessel that collects inside the body. Internal bleeding is not visible from the outside, it is a serious medical emergency but the extent of severity depends on bleeding rate and location of the bleeding. Severe internal bleeding into the chest, retroperitoneal space and thighs can cause hemorrhagic shock or death if proper medical treatment is not received quickly. Internal bleeding is a medical emergency and should be treated by medical professionals; the most common cause of death in trauma is bleeding. Death from trauma accounts for 1.5 million of the 1.9 million deaths per year due to bleeding. There are two types of trauma: penetrating trauma and blunt trauma. Penetrating trauma can result in internal bleeding, it can occur after a ballistic stab wound. If penetrating trauma occurs in blood vessels close to the heart, it can lead to hemorrhagic or hypovolemic shock and death. Blunt trauma is another cause of vascular injury, it can occur after a high speed deceleration in an automobile accident.
A number of pathological conditions and diseases can lead to internal bleeding. These include: Blood vessel rupture as a result of high blood pressure, esophageal varices, peptic ulcers, or ectopic pregnancy. Other diseases linked to internal bleeding include cancer, hematologic disease, Vitamin K deficiency, rare viral hemorrhagic fevers, such as the Ebola, Dengue or Marburg viruses. Internal bleeding could be caused by medical error as a result of complications after surgical operations or medical treatment; some medication effects may lead to internal bleeding, such as the use of anticoagulant drugs or antiplatelet drugs in the treatment of coronary artery disease. At first, there may be no symptoms of internal bleeding. If an organ is damaged and it bleeds, it can be painful. Over time, internal bleeding can cause low blood pressure, increased heart rate, increased breathing rate, confusion and loss of consciousness. A patient may lose more than 30% of their blood volume before there are changes in their vital signs or level of consciousness.
This is called hemorrhagic or hypovolemic shock, a type of shock that occurs when there is not enough blood to reach organs in the body. Early symptoms include anxiety, increased breathing rate, weak peripheral pulses, cold skin on the arms and legs. If internal bleeding is not treated, the heart and breathing rate will continue to increase while blood pressure and mental status decrease. Internal bleeding can result in death by blood loss; the median time from the onset of hemorrhagic shock to death by exsanguination is 2 hours. Internal bleeding can occur anywhere in the body; some symptoms of internal bleeding depend on the location of the bleed. Some examples of types of internal bleeding include: Head: Intracranial hemorrhage, cerebral hemorrhage, subarachnoid hemorrhage, subdural hematoma, epidural hematoma Torso: cardiac tamponade, pulmonary hemorrhage, aortic aneurysm, gastrointestinal bleeding, blunt kidney trauma, splenic injury retroperitoneal bleeding, postpartum bleeding, ectopic pregnancy Extremities: bone fracture, hemarthrosis Blood loss can be estimated based on heart rate, blood pressure, respiratory rate, mental status.
Advanced trauma life support by the American College of Surgeons separates hemorrhagic shock into four categories. Assessing circulation occurs after breathing. If internal bleeding is suspected, a patient’s circulatory system is assessed through palpation of pulses and doppler ultrasonography, it is important to examine the patient for visible signs that may suggest internal bleeding: a wound bruising blood collection abnormal skin sensation signs of compartment syndromeIt is important to look for the source of the internal bleeding. If internal bleeding is suspected after trauma, a FAST exam may be performed to look for bleeding in the abdomen. If the patient has stable vital signs, they may undergo diagnostic imaging such as a CT scan. If the patient has unstable vital signs, they may not undergo diagnostic imaging and instead may receive immediate medical or surgical treatment. Management of internal bleeding depends on the severity of the bleed. Internal bleeding is a medical emergency and should be treated by medical professionals.
If a patient has low blood pressure, intravenous fluids can be used until they can receive a blood transfusion. In order to replace blood loss and with large amounts of IV fluids or blood, patients may need a central venous catheter. Patients with severe bleeding need to receive large quantities of replacement blood via a blood transfusion; as soon as the clinician recognizes that the patient may have a severe, continuing hemorrhage requiring more than 4 units in 1 hour or 10 units in 6 hours, they should initiate a massive transfusion protocol. The massive transfusion protocol replaces red blood cells and platelets in varying ratios based on the cause of the bleeding, it is important to stop bleeding after identifying the cause of internal bleeding. Studies have shown that taking longer to achieve hemostasis in patients with traumatic causes and non-traumatic causes is associated with an increased death rate.. Un
Muscle contraction is the activation of tension-generating sites within muscle fibers. In physiology, muscle contraction does not mean muscle shortening because muscle tension can be produced without changes in muscle length such as holding a heavy book or a dumbbell at the same position; the termination of muscle contraction is followed by muscle relaxation, a return of the muscle fibers to their low tension-generating state. Muscle contractions can be described based on two variables: tension. A muscle contraction is described as isometric if the muscle tension changes but the muscle length remains the same. In contrast, a muscle contraction is isotonic if muscle tension remains the same throughout the contraction. If the muscle length shortens, the contraction is concentric. In natural movements that underlie locomotor activity, muscle contractions are multifaceted as they are able to produce changes in length and tension in a time-varying manner. Therefore, neither length nor tension is to remain the same in muscles that contract during locomotor activity.
In vertebrates, skeletal muscle contractions are neurogenic as they require synaptic input from motor neurons to produce muscle contractions. A single motor neuron is able to innervate multiple muscle fibers, thereby causing the fibers to contract at the same time. Once innervated, the protein filaments within each skeletal muscle fiber slide past each other to produce a contraction, explained by the sliding filament theory; the contraction produced can be described as a twitch, summation, or tetanus, depending on the frequency of action potentials. In skeletal muscles, muscle tension is at its greatest when the muscle is stretched to an intermediate length as described by the length-tension relationship. Unlike skeletal muscle, the contractions of smooth and cardiac muscles are myogenic, although they can be modulated by stimuli from the autonomic nervous system; the mechanisms of contraction in these muscle tissues are similar to those in skeletal muscle tissues. Muscle contractions can be described based on two variables: length.
Force itself can be differentiated as either load. Muscle tension is the force exerted by the muscle on an object whereas a load is the force exerted by an object on the muscle; when muscle tension changes without any corresponding changes in muscle length, the muscle contraction is described as isometric. If the muscle length changes while muscle tension remains the same the muscle contraction is isotonic. In an isotonic contraction, the muscle length can either shorten to produce a concentric contraction or lengthen to produce an eccentric contraction. In natural movements that underlie locomotor activity, muscle contractions are multifaceted as they are able to produce changes in length and tension in a time-varying manner. Therefore, neither length nor tension is to remain constant when the muscle is active during locomotor activity. An isometric contraction of a muscle generates tension without changing length. An example can be found when the muscles of the forearm grip an object. In isotonic contraction, the tension in the muscle remains constant despite a change in muscle length.
This occurs. In concentric contraction, muscle tension is sufficient to overcome the load, the muscle shortens as it contracts; this occurs. During a concentric contraction, a muscle is stimulated to contract according to the sliding filament theory; this occurs throughout the length of the muscle, generating a force at the origin and insertion, causing the muscle to shorten and changing the angle of the joint. In relation to the elbow, a concentric contraction of the biceps would cause the arm to bend at the elbow as the hand moved from the leg to the shoulder. A concentric contraction of the triceps would change the angle of the joint in the opposite direction, straightening the arm and moving the hand towards the leg. In eccentric contraction, the tension generated while isometric is insufficient to overcome the external load on the muscle and the muscle fibers lengthen as they contract. Rather than working to pull a joint in the direction of the muscle contraction, the muscle acts to decelerate the joint at the end of a movement or otherwise control the repositioning of a load.
This can occur voluntarily. Over the short-term, strength training involving both eccentric and concentric contractions appear to increase muscular strength more than training with concentric contractions alone. However, exercise-induced muscle damage is greater during lengthening contractions. During an eccentric contraction of the biceps muscle, the elbow starts the movement while bent and straightens as the hand moves away from the shoulder. During an eccentric contraction of the triceps muscle, the elbow starts the movement straight and bends as the hand moves towards the shoulder. Desmin and other z-line proteins are involved in eccentric contractions, but their mechanism is poorly understood in comparison to crossbridge cycling in concentric contractions. Though the muscle is doing a negative amount of mechanical work, (work is being d
Action sports, adventure sports or extreme sports are activities perceived as involving a high degree of risk. These activities involve speed, height, a high level of physical exertion and specialized gear; the definition of extreme sports is not exact and the origin of the terms is unclear, but it gained popularity in the 1990s when it was picked up by marketing companies to promote the X Games and when the Extreme Sports Channel and the Extreme Sports Company launched. More the used definition from research is "a competitive activity within which the participant is subjected to natural or unusual physical and mental challenges such as speed, depth or natural forces and where fast and accurate cognitive perceptual processing may be required for a successful outcome" by Dr. Rhonda Cohen. While use of the term "extreme sport" has spread everywhere to describe a multitude of different activities which sports are considered'extreme' is debatable. There are, several characteristics common to most extreme sports.
While they are not the exclusive domain of youth, extreme sports tend to have a younger-than-average target demographic. Extreme sports are rarely sanctioned by schools for their physical education curriculum. Extreme sports tend to be more solitary than many of the popular traditional sports. Activities categorized by media as extreme sports differ from traditional sports due to the higher number of inherently uncontrollable variables; these environmental variables are weather and terrain related, including wind, snow and mountains. Because these natural phenomena cannot be controlled, they affect the outcome of the given activity or event. In a traditional sporting event, athletes compete against each other under controlled circumstances. While it is possible to create a controlled sporting event such as X Games, there are environmental variables that cannot be held constant for all athletes. Examples include changing snow conditions for snowboarders and ice quality for climbers, wave height and shape for surfers.
Whilst traditional sporting judgment criteria may be adopted when assessing performance, extreme sports performers are evaluated on more subjective and aesthetic criteria. This results in a tendency to reject unified judging methods, with different sports employing their own ideals and indeed having the ability to evolve their assessment standards with new trends or developments in the sports. While the exact definition and what is included as extreme sport is debatable, some attempted to make classification for extreme sports. One argument is. A passenger in a canyon jet boat ride will not fulfill the requirements, as the skill required pertains to the pilot, not the passengers. "Thrill seeking" might in these cases be a more suitable qualification than "extreme sport". Extreme sports may be subdivided into: These sports require the use of snow, ice or water sports and rolling sports. Another subdivision can be made along motorized and non motorized vehicle sports, resulting in the following matrix.
The phrase is. The implication of the phrase was that the word "sport" defined an activity in which one might be killed; the other activities being termed "games". The phrase may have been invented by either writer Barnaby Conrad or automotive author Ken Purdy; the Dangerous Sports Club of Oxford University, England was founded by David Kirke, Chris Baker, Ed Hulton and Alan Weston. They first came to wide public attention by inventing modern day bungee jumping, by making the first modern jumps on 1 April 1979, from the Clifton Suspension Bridge, England, they followed the Clifton Bridge effort with a jump from the Golden Gate Bridge in San Francisco and with a televised leap from the Royal Gorge Suspension Bridge in Colorado, sponsored by and televised on the popular American television program That's Incredible! Bungee jumping was treated as a novelty for a few years became a craze for young people, is now an established industry for thrill seekers; the Club pioneered a surrealist form of skiing, holding three events at St. Moritz, Switzerland, in which competitors were required to devise a sculpture mounted on skis and ride it down a mountain.
The event reached its limits when the Club arrived in St. Moritz with a London double-decker bus, wanting to send it down the ski slopes, the Swiss resort managers refused. Other Club activities included. In recent decades the term extreme sport was further promoted after the Extreme S
A capillary is a small blood vessel from 5 to 10 micrometres in diameter, having a wall one endothelial cell thick. They are the smallest blood vessels in the body: they convey blood between the arterioles and venules; these microvessels are the site of exchange of many substances with the interstitial fluid surrounding them. Substances which exit include water and glucose. Lymph capillaries connect with larger lymph vessels to drain lymphatic fluid collected in the microcirculation. During early embryonic development new capillaries are formed through vasculogenesis, the process of blood vessel formation that occurs through a de novo production of endothelial cells which form vascular tubes; the term angiogenesis denotes the formation of new capillaries from pre-existing blood vessels and present endothelium which divides. Blood flows from the heart through arteries, which branch and narrow into arterioles, branch further into capillaries where nutrients and wastes are exchanged; the capillaries join and widen to become venules, which in turn widen and converge to become veins, which return blood back to the heart through the venae cavae.
Individual capillaries are part of the capillary bed, an interweaving network of capillaries supplying tissues and organs. The more metabolically active a tissue is, the more capillaries are required to supply nutrients and carry away waste products. There are two types of capillaries: true capillaries, which branch from arterioles and provide exchange between tissue and the capillary blood, metarterioles, found only in the mesenteric circulation, they are short vessels that directly connect the arterioles and venules at opposite ends of the beds. Metarterioles are found in the mesenteric microcirculation; the physiological mechanisms underlying precapillary resistance is no longer considered to be a result of precapillary sphincters outside of the mesentery organ. Lymphatic capillaries are larger in diameter than blood capillaries, have closed ends; this structure permits interstitial fluid to flow into them but not out. Lymph capillaries have a greater internal oncotic pressure than blood capillaries, due to the greater concentration of plasma proteins in the lymph.
There are three types of blood capillaries: Continuous capillaries are continuous in the sense that the endothelial cells provide an uninterrupted lining, they only allow smaller molecules, such as water and ions to pass through their intercellular clefts. Lipid-soluble molecules can passively diffuse through the endothelial cell membranes along concentration gradients. Continuous capillaries can be further divided into two subtypes: Those with numerous transport vesicles, which are found in skeletal muscles, fingers and skin; those with few vesicles, which are found in the central nervous system. These capillaries are a constituent of the blood–brain barrier. Fenestrated capillaries have pores in the endothelial cells that are spanned by a diaphragm of radially oriented fibrils and allow small molecules and limited amounts of protein to diffuse. In the renal glomerulus there are cells with no diaphragms, called podocyte foot processes or pedicels, which have slit pores with a function analogous to the diaphragm of the capillaries.
Both of these types of blood vessels have continuous basal laminae and are located in the endocrine glands, intestines and the glomeruli of the kidney. Sinusoid capillaries are a special type of open-pore capillary, that have larger openings in the endothelium; these types of blood vessels allow red and white blood cells and various serum proteins to pass, aided by a discontinuous basal lamina. These capillaries lack pinocytotic vesicles, therefore utilize gaps present in cell junctions to permit transfer between endothelial cells, hence across the membrane. Sinusoid blood vessels are located in the bone marrow, lymph nodes, adrenal glands; some sinusoids are distinctive in. They are called discontinuous sinusoidal capillaries, are present in the liver and spleen, where greater movement of cells and materials is necessary. A capillary wall is simple squamous epithelium; the capillary wall performs an important function by allowing nutrients and waste substances to pass across it. Molecules larger than 3 nm such as albumin and other large proteins pass through transcellular transport carried inside vesicles, a process which requires them to go through the cells that form the wall.
Molecules smaller than 3 nm such as water and gases cross the capillary wall through the space between cells in a process known as paracellular transport. These transport mechanisms allow bidirectional exchange of substances depending on osmotic gradients and can be further quantified by the Starling equation. Capillaries that form part of the blood–brain barrier however only allow for transcellular transport as tight junctions between endothelial cells seal the paracellular space. Capillary beds may control their blood flow via autoregulation; this allows an organ to maintain constant flow despite a change in central blood pressure. This is achieved by myogenic response, in the kidney by tubuloglomerular feedback; when blood pressure increases, arterioles are stretched and subsequently constrict to counteract the
Neisseria meningitidis referred to as meningococcus, is a Gram-negative bacterium that can cause meningitis and other forms of meningococcal disease such as meningococcemia, a life-threatening sepsis. It has been reported to be transmitted through oral sex and cause urethritis in men; the bacterium is referred to as a coccus because it is round, more diplococcus because of its tendency to form pairs. About 10% of adults are carriers of the bacteria in their nasopharynx; as an human pathogen it is the main cause of bacterial meningitis in children and young adults, causing developmental impairment and death in about 10% of cases. It causes the only form of bacterial meningitis known to occur epidemically Africa and Asia, it occurs worldwide in endemic form. N. Meningitidis is spread through saliva and respiratory secretions during coughing, kissing, chewing on toys and through sharing a source of fresh water, it infects its host cells by sticking to them with long thin extensions called pili and the surface-exposed proteins Opa and Opc and has several virulence factors.
Meningococcus can cause other forms of meningococcal disease. It produces general symptoms like fatigue and headache and can progress to neck stiffness and death in 10% of cases. Symptoms of meningococcal meningitis are confused with those caused by other bacteria, such as Haemophilus influenzae and Streptococcus pneumoniae. Suspicion of meningitis is a medical emergency and immediate medical assessment is recommended. Current guidance in the United Kingdom is that if a case of meningococcal meningitis or septicaemia is suspected intravenous antibiotics should be given and the ill person admitted to the hospital; this means that laboratory tests may be less to confirm the presence of Neisseria meningitidis as the antibiotics will lower the number of bacteria in the body. The UK guidance is based on the idea that the reduced ability to identify the bacteria is outweighed by reduced chance of death. Septicaemia caused by Neisseria meningitidis has received much less public attention than meningococcal meningitis though septicaemia has been linked to infant deaths.
Meningococcal septicaemia causes a purpuric rash, that does not lose its color when pressed with a glass and does not cause the classical symptoms of meningitis. This means. Septicaemia carries an approximate 50% mortality rate over a few hours from initial onset. Other severe complications include Waterhouse–Friderichsen syndrome, a massive bilateral, hemorrhage into the adrenal glands caused by fulminant meningococcemia, adrenal insufficiency, disseminated intravascular coagulation. Not all instances of a purpura-like rash are due to meningococcal septicaemia. N. meningitidis is a Gram-negative diplococcus since it has an outer and inner membranes with a thin layer of peptidoglycan in between. It is 0.6–1.0 micrometers in size. It tests positive for the enzyme cytochrome c oxidase. N. meningitidis is a part of the normal nonpathogenic flora in the nasopharynx of up to 5–15% of adults. It colonizes and infects only humans, has never been isolated from other animals; this is thought to stem from the bacterium's inability to get iron from sources other than human transferrin and lactoferrin.
Disease-causing strains are classified according to the antigenic structure of their polysaccharide capsule. Serotype distribution varies markedly around the world. Among the 13 identified capsular types of N. meningitidis, six account for most disease cases worldwide. Type A has been the most prevalent in Africa and Asia, but is rare/practically absent in North America. In the United States, serogroup B is the predominant cause of disease and mortality, followed by serogroup C; the multiple subtypes have hindered development of a universal vaccine for meningococcal disease. Lipooligosaccharide is a component of the outer membrane of N. meningitidis. This acts as an endotoxin and is responsible for septic shock and hemorrhage due to the destruction of red blood cells. Other virulence factors include a polysaccharide capsule which prevents host phagocytosis and aids in evasion of the host immune response, it infects the cell by sticking to it with long thin extensions called pili and the surface-exposed proteins Opa and Opc.
Meningococci produce an IgA protease, an enzyme that cleaves IgA class antibodies and thus allows the bacteria to evade a subclass of the humoral immune system. A hypervirulent strain was discovered in China, its impact is yet to be determined. Factor H binding protein, exhibited in N. meningitidis and some commensal species is the main inhibitor of the alternative complement pathway. FHbp protects meningococci from complement-mediated death in human serum experiments, but has been shown to protect meningococci from antimicrobial peptides in vitro. Factor H binding protein is key to the pathogenesis of N. meningitidis, is, important as a potential vaccine candidate. Porins are an important factor for complement inhibition for both pathogenic and commensal species. Porins are important for nutrient acquisition. Porins are recognized by TLR2, they bind complement factors. Cooperation with pili for CR3-mediated internalization is another function of porins. A