Human Diseases: Classification, Types, Causes and Preventions (2023)

Human Diseases

• Disease is a state when the functioning of one or more organs of human's body is adversely affected, characterized by the various signs and symptoms.
• The diseases which are caused by the intrinsic sources like cardiac failure, kidney failure, diabetes, allergies, cancer etc. are known as the organic or metabolic diseases and the diseases which are caused by the extrinsic factors are Kwashiorkor, obesity, Night blindness, scurvy etc.

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Infectious and Non- Infectious Diseases

Infectious Disease

Infectious Diseases are those diseases that can easily be transmitted from one person to another person. These diseases are also known as communicable/contagious diseases. Some examples of infectious diseases are common cold, ringworm, tuberculosis, malaria etc

Some of the common infectious diseases are listed below:

• Bacterial Diseases: Typhoid- Typhoid affects a very large number of people and spreads by contaminated food or water. It infects the small intestine of the human body. Typhoid mainly causes high fever, stomach ache, headache, loss of appetite, and constipation.

• Pneumonia - Pneumonia is spread by the droplets which are emitted by the infected people. Pneumonia is caused by the Streptococcus pneumoniae and Haemophilus influenzae. In the event of pneumonia, the mainly alveoli become infected. Pneumonia causes chills, fever, headache etc. In severe cases, lips and nails turn greyish in color.

• Viral Diseases: The main viral disease is common cold. It is a pathogen borne disease. It's basically the same as a virus. In the case of a common cold, the nose and respiratory passages are affected. The common cold spreads via droplets which are released as a result of coughing or sneezing, or even from contaminated objects. The common cold causes discharge and nasal congestion, cough, sore throat, headache and tiredness.

• Protozoan Diseases: The protozoan diseases include organisms classified in Amoebozoa, Excavate, and Chromalveolata. The infections of protozoan diseases are parasitic diseases which are typically caused by the organisms formerly classified in the Kingdom Protozoa.Some of the examples of Protozoan Diseases are Entamoeba histolytica, Plasmodium (some of which cause malaria), and Giardia lamblia.
• Fungal Diseases: Fungi are common in the environment, and people breathe in or come in contact with the fungal spores every day without getting sick. A fungal infection is also called mycosis. Although most fungi are completely harmless to human beings, some of them are capable of causing diseases under specific conditions.

• Helminthic Diseases: The helminthic disease ascariasis is caused by an intestinal endoparasite of human, Ascaris lumbricoides commonly called roundworm. This infection occurs as the eggs of parasites are excreted along with the faces of infected persons, which contaminate water, soil, plants, etc.

Non - Infectious Disease

Non-infectious diseases are those diseases that are not transmitted from one person to another person. They are also known as non-communicable diseases. These diseases are caused either due to genetic disorders or due to external factors such as unhealthy diets, consumption of drugs, alcohol etc., or due to the lack of physical activities.

• Emphysema: Emphysema is a very serious lung disease that follows destruction of the elastic and connective tissue fibers which are supporting the lungs. It is linked with the advancing age, though certain forms of emphysema are inherited.

• Pulmonary Edema: Because of the physiologic relationship between heart and the respiratory system, they are often linked in disease. Acute pulmonary edema results when fluid quickly accumulates in the lungs and fills it with the alveoli. The fluid buildup is caused by the heart trouble that, in turn, produces back pressure in the pulmonary veins and the left atrium of the heart to which they carry oxygen-rich blood from the lungs.
• Occupational Lung Diseases: Miners and some of the industrial workers are extremely vulnerable to developing the respiratory disease because of the conditions in which they work. Pneumoconiosis, which is also known as “dust disease,” is the name which is given to this family of disorder.

• Respiratory Distress Syndrome: Respiratory Distress Syndrome formerly called hyaline membrane disease; it is an often-fatal disorder of some prematurely born infants. A protein material lines alveoli of the lungs in the afflicted babies and also limits the amount of oxygen the blood can receive.

Congenital and Acquired Diseases

1. Congenital Diseases: A disease that is present at birth. It may be due to hereditary factors, prenatal infection, injury, or the effect of a drug the mother took during the time of pregnancy. Defects in the chromosomes and genes are passed down from one generation to another generation and can affect the baby.
2. Acquired Diseases: An acquired disease is a medical condition which develops post-fatally; in contrast with a congenital disorder, which is present at birth. A congenital disorder might be antecedent to an acquired disorder (such as Eisenmenger's syndrome).

Allergies and Deficiencies

1. Allergies: Allergies are typically the reaction of the human body to a normally harmless substance like pollen, molds, animal dander, latex, certain foods, insect stings and others. The symptoms of allergies range from the mild – rash or hives, itchiness, runny nose, watery/red eyes – to the life-threatening.
2. Deficiencies: The group of diseases produced by the deficiency of nutrients, vitamins, minerals, and hormones are collectively known as the deficiency diseases. Kwashiorkor, night blindness, goiter, anemia, diabetes, scurvy are some of the examples of deficiency diseases.

Things to Remember based on Human Diseases

• A human disease is an interruption or adjustment of a person's normal state that interrupts or modifies vital functions.
• Immunodeficiency disorders disrupt the ability of the body of a human being to defend itself against diseases like bacteria, viruses, and parasites.
• Diseases may be of two types: acute or chronic, it completely depends on the duration of the disease course and the rapidity of intensification and disappearance of the symptoms.
• Infectious diseases are the third leading cause of death in the United States, accounting for over 170,000 deaths per year, nearly doubling since the early 1980s.

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Important Questions based on Human Diseases

Ques: What are Noncommunicable diseases? ( 1 Mark)

Ans. Noncommunicable diseases are also referred to as chronic diseases, which are long-lasting and are caused by inherited genetic abnormalities.

Ques: How would the immune system of a person be affected when there is the absence of a thymus gland? ( 2 Marks)

Ans. T-Lymphocytes in our body mature in the thymus gland. If the thymus gland is removed from the human body, T-Lymphocytes will fail to mature causing the immune system to not develop. Thus, the individual becomes susceptible to most of the diseases.

Ques: List the preventive barriers that can protect the body of a person against microbial bacteria by entering the gut through the food consumed by a person. ( 2 Marks)

Ans. Following are the barriers:

• Lysozyme present in the saliva
• Presence of acid (HCl) in stomach

Ques: What are Deficiency Diseases? ( 2 Marks)

Ans. The group of diseases produced by the deficiency of nutrients, vitamins, minerals, and hormones are collectively called deficiency diseases. Kwashiorkor, night blindness, goiter, anemia, diabetes, scurvy are a few examples of deficiency diseases.

Ques: Which types of smoking are more dangerous: active smoking or passive smoking? State why. ( 2 Marks)

Ans. The active and passive smoking can equally be dangerous for a person, as passive smoking exposes one to the same harmful effects as active smoking. Once the smoke is inhaled by a person, it induces cough, prolonged exposure can cause emphysema, bronchitis and infections of the respiratory tract thereby causing lung cancer eventually.

Ques: How are diseases classified in the human body? ( 2 Marks)

Ans. The body of a human being tends to suffer from many kinds of infections and diseases and that might be because of genetic defects or an unhealthy lifestyle. These diseases can be typically classified into two different categories.

Ques: What are the different types of acquired diseases? ( 2 Marks)

Ans. Acquired diseases are the kinds of diseases that have been acquired during the lifetime of an individual. The acquired diseases are of two types, Infectious or communicable disease, non-communicable disease.

Ques: Why are diseases like cholera, typhoid, dysentery etc., more common in overcrowded places? ( 2 Marks)

Ans. It is because they are infectious diseases and can be communicated from one person to another person. Water gets mixed with the excreta of the infected people thereby contaminating it. Such water, if consumed by a person then it causes the infection to spread to non-infected people.

Ques. How did the study of biology help people to control infectious or non-communicable diseases? ( 3 Marks)

Ans. The science that makes a study of the different diseases is called pathology, though in a broad sense it includes diagnostic, prophylactic and curative measures as well.

Pathology is the study of diseases of all kinds though we will confine ourselves to the diseases caused by the pathogenic organisms, the reaction of the host as shown in the form of symptoms, the diagnosis made through the study of their symptoms, etiology of the pathogenic organism and finally steps undertaken to cure the host of the diseases caused by it, by eradicating and if it is not possible, by controlling the pathogen. This is how the study of biology helped people to control infectious diseases.