Human Respiratory and Digestive Systems & Illnesses
Human Respiratory and Digestive Systems
The respiratory system exchanges gases with the external environment. It takes oxygen (O₂) from the air and transfers it to the bloodstream, while taking carbon dioxide (CO₂) from the blood and expelling it from the body.
The Respiratory System
Components of the Respiratory Tract
- Nasal passages
- Pharynx
- Larynx
- Trachea
- Bronchi
- Bronchioles
These tubes carry air from outside the body into the lungs and vice versa.
The Lungs
Spongy organs located in the rib cage and separated from the abdomen by a muscle called the diaphragm. They are surrounded by a double membrane, called pleura, which contains pleural fluid.
How the Respiratory System Works
There are three stages to breathing:
- Inhalation: The diaphragm contracts and the lungs expand. Air enters through the mouth or nasal passages, where it is heated before travelling through the respiratory tract to the alveoli.
- Gas Exchange: Gases diffuse naturally, passing through cell membranes, moving from where they are most concentrated to where there is lower concentration. For this reason, O₂ (highly concentrated in the alveoli) passes through the walls of these alveoli into the incoming blood (which is low in O₂), and the abundant CO₂ in this blood from the cells diffuses into the inside of the alveoli (where there is little CO₂) and is then expelled.
- Exhalation: The diaphragm relaxes and the lungs decrease in volume. The air rich in CO₂ is expelled through the respiratory tract.
Digestive Illnesses
Causes of Digestive Illnesses
- Unhealthy diet
- Viral or bacterial infections
Illnesses by Affected Part
- Mouth Illnesses:
- Dental cavities (tooth decay): Tooth enamel is destroyed.
- Gingivitis: Inflammation of the gums that can lead to tooth loss.
- Stomach Illnesses:
- Gastritis: Inflammation of the mucous lining the stomach.
- Ulcers: Wounds usually found in the stomach or the duodenum.
- Liver Illnesses:
- Hepatitis: Inflammation of the liver caused by viruses, excessive alcohol consumption, or certain medications.
- Intestinal Illnesses:
- Gastroenteritis: Caused by bacteria found in contaminated water or food.
- Constipation: Condition associated with hardened faeces.
- Salmonellosis: Caused by eating food contaminated with Salmonella bacteria.
- Appendicitis: The appendix becomes inflamed and painful.
Food-Borne Illnesses
Some digestive illnesses can be caused by different pathogens (bacteria, fungi, parasites, viruses) present in contaminated food or water.
- Salmonellosis: Caused by food contaminated with Salmonella bacteria found in contaminated water, in poorly preserved foods made with egg like mayonnaise and cream sauces, and in meat. Symptoms include headache, vomiting, and diarrhoea.
- Botulism: Caused by food contaminated with Clostridium botulinum bacteria that produces botulinum toxin, a potentially lethal toxin that causes neurological disorders. Contamination occurs when consuming inadequately preserved foods.
- Trichinosis: Associated with eating raw meat (pork) infested with the larvae of a nematode called Trichinella. It causes abdominal pain, vomiting, diarrhoea, and fever.
- Anisakiasis: Caused by eating raw or undercooked fish containing the larvae of the Anisakis worm. Symptoms include abdominal pain, vomiting, and diarrhoea.
Food-borne illnesses result from eating spoiled food or food that has been contaminated. Raw foods such as fruit and vegetables and undercooked meat or fish may be contaminated by some of these pathogens.
Respiratory Illnesses
Causes of Respiratory Illnesses
- Smoking or long-term exposure to air pollution
- Viral or bacterial infections
- Allergies
Common Respiratory Illnesses
- Chronic bronchitis: Irritation of the bronchi caused by smoking or exposure to pollutants in the air.
- Asthma: Inflammation of the bronchi caused by smoking or exposure to pollution, but also by allergies.
- Influenza (or flu): Caused by the influenza virus. Can be serious, especially for elderly people and high-risk groups.
- Lung and throat cancer: Most commonly affect smokers.