Human health and disease 

      Health doesn't merely mean 'absence of disease' or good shape. In fact, it's difficult to with competence outline health. consistent with the World Health Organization, health is outlined because the state of complete physical, mental and social well- being and not simply the absence of unwellness or frailness. In short, health is birth right of humans. Health additionally reflects the metabolic and functional potency of living organisms. Hygiene may be a science of rules of health. Toachieve healthiness, it's so, necessary that we've got hygienical diet, clean drink, personal and community hygiene, regular workout, data regarding diseases and their impact on body, correct disposal of waste and management of vectors.

Everyday we have a tendency to area unit exposed to varied foreign bodies, as well as infectious agents like microorganism, viruses, etc. Despite constant exposure to type of pathogens, most folks stay healthy. this is often because of incontrovertible fact that the form has ability to resist most sort of these foreign bodies. The system that protects United States of America from varied infectious agents, is termed system. Resistance is that the ability to forestall the injury or unwellness, through our defense.

 Immunity:

 The term 'immunity has traditionally  referred to because the resistance exhibited by the Their product, However, protection against Infectious diseases is only one of the many 

consequences of immune reactions , that is entirely involved with the reaction of the body against any foreign substance

 Immunity is really the "freedom "exempt". The construct of immunity is believed to be started by Edward Jenner in European nation. He developed cowfox  vaccine immunizing agent for the protection against the attack of tiny pox (virus). medical specialty may be a branch of science that deals with the study of system,  immune responses to foreign substances and their role in resisting infection by pathogens

 the foremost necessary characteristic of system is that it distinguishes self (body's own cells) and non-self (foreign molecules or offensive cells). So, the system differentiates between the body cells and also the invaders. Any foreign substance offensive body associate degreed capable of stimulating an immune reaction, is termed associate degree substance. The protecting chemicals created by immune cells in response to antigens area unit referred to as antibodies

    

A. kinds of immunity:

 There area unit two  kinds of immunity as Innate or Inborn (inherited) immunity and purchased or adaptive  immunity.

 i. natural immunity or Inborn immunity: 

natural immunity is that the resistance to infections that a private possesses by virtue of his or her genetic make-up. it's the natural (inborn) implements of war of the body, it's not suffering from previous contact with microorganisms or immunisation. it's nonspecific, once it indicates a degree of resistance to infection explicit infective agent cares. One sort of barriers that stop entry of forcign ogents normally, or specific wherever resistance to a natural immunity includes the varied kinds of into the body

a. Animal tissue surface :

 The intact skin and secretion covering the body, defend it significantly against invasion by microorganism(s). 

The healthy skin possesses germicidal activity because of the presence of high concentrations of salt in drying sweat. oleaginous secretions and long chain of fatty acids have bactericidal and agent properties. The tissue layer of the tract has many innate mechanisms of defense. The nose prevents entry of microorganisms to an oversized extent, the inhaled  particles being inactive through hair at or close to the nasal orifices. those who pass on the far side area unit control by mucous secretion lining the animal tissue and area unit swept wing bock beer to tubular cavity wherever they have an inclination to engulfed or coughed out.

 The cough reflex is a very important defense of tract. The mouth is consistently bathed in secretion that has repressing impact on microorganisms. The acidity of stomachal secretions within the abdomen destroys microorganisms. The flushing action of excretory product climinates microorganism from the duct. Spermine and metal gift in liquid body substance area unit antibacterial drug. 

    b.  Antimicrobial substances in blood and tissues: 

The complement system contains quite thirty bodily fluid proteins, current within the blood in associate degree inactive state. The presence of microorganism pathogens activates the 'Complement cascade to eliminate pathogens. The interferons area unit a category of cytokines (soluble proteins) discharged by virally cells infected with viruses and sure white blood cells to stimulate alternative cells to shield themselves from infection. blood and tissues by microorganisms

c. Cellular factors in innate immunity:

 Natural defence against the invasion of alternative foreign particles, is mediate to an oversized extent by phagocytes cells that ingest and destroy them. Phagocytes cells (discovered by Elie Metchnikoff in 1882) area unit sorted as macrophages and macrophages. They take away foreign particles that enter the body. a category of lymphocytes referred to as Natural killer (NK) cells is very important in nonspecific defence against infectious agent infections and tumors.

d. Fever 

Increase within the blood heat following the infection may be a natural defense. It helps to accelerate the physiological processes to destroy the offensive pathogens. Fever stimulates the assembly of antiviral drug and helps in recovery from infectious agent infections.

 e. Acute part proteins (APPs): 

Infection on injury results in a increment in concentration of sure plasma proteins, together referred to as acute part proteins. These embrace C Reactiye supermolecule (CRP), Mannose binding supermolecule, Alpha-l- acid conjugated protein, bodily fluid Amyloid P, etc. APPS area unit believed to boost host resistance, stop tissue injury and promote repair of inflammatory lesions.

ii. non heritable or acquired immunity: 

The resistance that a personal acquires throughout life is understood as "Acquired immunity". it's additionally referred to as adaptive or Specific immunity". It involves the formation of antibodies within the body, that neutralize the antigens. nonheritable or adaptive immunity has the subsequent distinctive options.

a. Specificity: 

It will manufacture specific protein or T-lymphocyte against a selected antigen/pathogen

. b. Diversity:

 It will acknowledge a massive selection one of numerous pathogens or foreign molecules production 

 c. Discrimination between self and non- self: 

It differentiates between own body cells (self) and foreign (non-self) molecules. 

d. Memory: 

once the system encounters a selected spy for the primary time, it generates Associate in Nursing immunologic response and eliminates the trespasser. this is often known as initial encounter. The system retains the memory of the primary encounter. As a result, a second encounter with same infective agent brings regarding faster and stronger immunologic response.

B. Cells of Immune System:

 There area unit 2 main forms of cells concerned within the operating of system. they're (a) Lymphocytes and (b) matter Presenting cells

 a. Lymphocytes:

 Lymphocytes area unit the most cells of the system. They, just like the different blood corpuscles, arise from the stem cells, the haemocytoblasts, gift in liver of the fetus and within the bone marrow in adult. a number of them endure differentiation within the gut associated sac body fluid tissues (Tonsils, Peyer's patches) and area unit known as bursal 

 B-lymphocytes:

others area unit differentiated within the thymus and area unit termed as T-lymphocytes. The mature lymphocytes pass into body fluids (blood and lymph) and flow into within the body.

Many of them keep within the bodily fluid nodes. The B-lymphocytes and T-lymphocytes type body substance or antibody-mediated system (AMIS) and cell-mediated system (CMIS) severally. each the immune systems want antigens to return into action, however they respond in numerous ways that.

C. Vaccination:

 Administration of vaccinum (i.e. inactivated infective agent or matter protection of specific infective agent) to safeguard against a selected pathogen, is termed vaccination.

 The body's system helps to safeguard against pathogens that cause infection. lt's Associate in Nursing economical system, most of the time,, It either keeps microorganisms out or tracks them down and gets eliminate them. However, some pathogens will overwhelm the system. once this happens, it will cause serious health problem. The pathogens presumably to cause issues, area unit those the body does not acknowledge.

Vaccination may be a thanks to "teach" the system on the way to acknowledge and eliminate unhealthful organism. That way, body is usually ready if you're ever exposed.

 Vaccination is a very important kind of primary bar, that may defend individuals from obtaining sick. Vaccination has allowed us to regulate diseases like , polio, tetanus and pertussis that when vulnerable several lives. it is important that as many folks as doable get immunised. Vaccinations do not simply defend people, once enough individuals area unit immunised. It additionally helps to safeguard the society.