Human Health and Disease Prevention

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Human Beings and Health

The World Health Organisation (WHO) defines health as 'the complete physical, mental and social well-being, not only the absence of disease'.

Factors that Influence Health

The environment: healthy surroundings should be free of biological, physical or chemical elements that are harmful to your health.
Personal characteristics: genetic factors, age and gender predispose people to suffer from certain types of illnesses.
Lifestyle: healthy habits and lifestyles are very important for staying healthy.
Healthcare: it is essential to have an efficient healthcare system to guarantee public health.

Vital Signs

Vital signs are physiological parameters that inform us of our state of health or the evolution of a disease.

Body temperatureHeart rate
Between 35.8 °C and 37.2 °C.Between 60 and 80 beats per minute in a state of rest.
Breathing rateBlood pressure
Between 12 and 18 breaths per minuteMaximum 100/140. Minimum 60/90

Development of a Disease

Cause -> organic alteration -> symptoms and signs -> cure

There are two types of treatments: curative and symptomatic. The first one is used to cure the patient and recover health, and the second one is applied to alleviate the symptoms of the disease.

Types of Disease

By origin:

Infectious: Pathogenic microorganisms and most are contagious. Measles.
Non-infectious: Different causes: degenerative, genetic or deficiency. They're not contagious. Anaemia.

By appearance and duration:

Acute: Manifest quickly and last a short time. Flu.
Chronic: Manifest slowly and last a long time. Arthritis.

By incidence in the population:

Epidemic: many people in a short period of time. Cholera.
Sporadic: Affect a few people in the population. Heart attack.
Pandemic: Affect many countries or even the entire planet. AIDS.
Endemic: common and exclusive to a specific region. Malaria

Infectious Disease

Virulence describes the capacity of an agent of infection to invade and damage our organism.

Bacteria: tuberculosis -> Lungs, cholera -> Intestine, diphtheria -> Respiratory airways, tetanus -> Muscles

Protozoa: Malaria -> Blood, sleeping sickness -> Nervous tissue

Fungi: Athlete's foot -> Skin, candidiasis -> Skin and mucous membranes

Viruses: Measles -> Skin, hepatitis -> Liver, rabies -> Nervous system, AIDS -> Immune system

How Infectious Diseases are Transmitted

By direct contact: the microorganism passes directly from an ill person to a healthy person, without an intermediary. For example, sexually transmitted diseases.
By touching inert objects: any object or substance, such as a handkerchief, a glass, a fork, saliva.
By drinking water: sometimes, water can be contaminated with pathogenic microorganisms, for example, those that cause cholera.
By eating contaminated food: food can also be a vehicle for pathogenic microorganisms. Salmonella bacteria.
By the air: sometimes microorganisms travel on dust particles or freely in the air. Tuberculosis.
By animals: some animals carry the pathogenic microorganism. Sleeping sickness, trypanosoma brucei, Malaria

Our Body's Defences Against Infection

We don't always become ill when pathogenic microorganisms enter our body. Due to the internal and external defence systems.

External Defences

Structural barriers are the skin and mucous membranes. To prevent microorganisms from entering.
Biochemical barriers are saliva, tears and gastric juices. Destroy pathogenic agents.
Mechanical barriers carry microorganisms that have entered our body and prevent them from attaching.
Ecological barriers are non-pathogenic microorganisms that exist on the external surface of our body. Competition is similar between two species in the same ecosystems.

Internal Defences: The Immune System

The immune system comprises very effective internal defences, based on the action of the leucocytes or white blood cells. These are found in the blood.
· Non-specific defences act against any type of microorganism or foreign particle. This action is carried out by phagocytes: white blood cells that trap and eliminate pathogenic microorganisms. This process is called phagocytosis.
· Specific defences act against specific microorganisms or foreign molecules. Other types of leucocytes, called lymphocytes, produce proteins called antibodies. Antibodies are specific for each microorganism and destroy or inactivate the invading agents.

An infectious disease develops in the following phases:
Incubation stage: is the time between the moment the pathogenic agents invade an organism until the appearance of the first symptoms. Microorganisms reproduce.
Manifestation stage: symptoms and signs of the disease appear as a result of the damage in the tissues.
Convalescence stage: once the pathogens are eliminated, the body repairs the damage caused by the infection.

Healthy Habits

Consume food and drink only in good condition. Pay attention to the expiry date.
Use disinfectants to clean areas of the house where microorganisms could grow and cause infections.
Keep pets clean and healthy and take them to the vet at least once a year.
Use antiseptics such as alcohol, hydrogen peroxide or iodine to disinfect wounds.


Vaccination is a very effective method to prevent some infectious diseases and has saved countless lives.
Vaccines contain dead or inactive microbes that cause a specific disease.

Curing Infectious Diseases

Serum Therapy

This treatment administers antibodies against a specific microbe to the infected organism. The antibodies are produced by another person or animal that has had the same disease. These antibodies, called serums.

Diseases Affecting Systems in the Body

Diseases of the circulatory system called cardiovascular diseases, diseases affecting the respiratory system affect the bones and joints
CancerWhen certain cells suffer a transformation and begin to divide very quickly and uncontrollably, it is called a tumour
Malnutrition DiseasesPoor nutrition that is lacking certain nutrients
Traumatic InjuriesCaused by accidents that can be at home, work, in traffic, playing sports or during leisure.
Endocrine and Metabolic DiseasesCaused by the excessive or deficient secretion of a hormone or by malfunctions in the metabolic reactions
Mental and Behavioural DisordersChanges in reasoning, behaviour or emotions physical or psychological problems
Genetic DiseasesDisorders that are caused, at least in part, by the genes of the affected person
Parasitic DiseasesParasites: organisms that live off of other organisms

Prevention of Non-Infectious Diseases

Healthy Habits

·Follow a balanced diet to prevent deficiency and metabolic diseases and even some types of cancer.
·Don't consume toxic substances (tobacco, alcohol and drugs). They're related to cancer and mental disorders, functional diseases and traumatic injuries.
·Exercise on a regular basis. This stimulates all the body systems and helps maintain good health.
·Avoid contaminated environments, as they favour the appearance of numerous diseases
·Respect road safety rules and work safety rules. Act with precaution in risky situations to avoid accidents that we are very often responsible for.

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