Lesson Notes By Weeks and Term v4 - SHS 3
BIOSAFETY
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BIOSAFETY
Download the Lessonotes Mobile Ghana app for faster lesson access on Android and iPhone.
Subject: Biomedical Science
Class: SHS 3
Term: 1st Term
Week: 3
Grade code: 1.1.2.LI.2
Strand code: 1
Sub-strand code: 2
Content standard code: 1.1.2.CS.1
Indicator code: 1.1.2.LI.2
Theme: BIOMEDICAL SCIENCE IN SOCIETY
Subtheme: BIOSAFETY
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This lesson explores the critical topic of biosafety, focusing on how harmful microorganisms, or pathogens, find their way into our bodies. Understanding these "routes of exposure" is not just an academic exercise; it is essential for our personal health and the well-being of our communities in Ghana. From preventing common illnesses like malaria and cholera to understanding how to protect ourselves during global pandemics like COVID-19, this knowledge empowers us to make informed decisions to stay safe.
This section breaks down the core content needed to understand the routes of pathogen exposure. A. Fundamental Definitions Pathogen: A pathogen is any microorganism that can cause disease. Think of them as tiny invaders. The main types are: Bacteria (e.g., *Vibrio cholerae* which causes cholera, *Salmonella typhi* which causes typhoid fever) Viruses (e.g., Human Immunodeficiency Virus (HIV), Influenza virus, SARS-CoV-2 which causes COVID-19) Fungi (e.g., *Trichophyton* which causes ringworm or "kuronya") Protozoa (e.g., *Plasmodium* species which cause malaria) Route of Exposure: This is the specific pathway a pathogen takes to enter the human body and cause an infection. It is the "doorway" for the invader. B. The Four Main Routes of Exposure
There are four primary ways pathogens can enter our bodies. Direct Contact This involves the transfer of a pathogen through physical touch, either with an infected person or with their bodily fluids. Mechanism: Skin-to-Skin Contact: Touching, shaking hands, hugging an infected person. Contact with Bodily Fluids: Coming into contact with infected blood, saliva, semen, or wound secretions. Ghanaian Examples: Handshakes: The common and respected practice of shaking hands can easily spread viruses like the common cold or bacteria if hands are not washed. This was a major concern during the Ebola and COVID-19 outbreaks. Ringworm ("kuronya"): This fungal infection is often spread among children in schools through direct skin contact during play. Conjunctivitis ("Apollo"): This eye infection spreads rapidly when an infected person touches their eye and then touches another person or a surface like a doorknob. Inhalation (Airborne/Droplet) This occurs when a person breathes in pathogens suspended in the air. Mechanism: Droplets: An infected person coughs or sneezes, releasing large droplets containing pathogens. These droplets travel a short distance (about 1-2 meters) and can be inhaled by someone nearby or land on their mouth, nose, or eyes. Aerosols (Airborne): An infected person talks, breathes, or coughs, releasing very fine particles that can remain suspended in the air for hours and travel long distances. Ghanaian Examples: Tuberculosis (TB): The bacteria that cause TB are spread through the air when an infected person coughs or sneezes in a poorly ventilated space, such as a crowded room or tro-tro. COVID-19 / Influenza: These viruses spread easily through both droplets and aerosols in places like churches, mosques, markets, and classrooms. Meningitis: Outbreaks in the northern parts of Ghana are often linked to airborne transmission of the bacteria in hot, dusty conditions. Ingestion This route involves consuming food or water contaminated with pathogens. Mechanism: Faecal-Oral Route: Pathogens from the faeces of an infected person contaminate water sources, food, or hands, and are then ingested by another person. This is very common where sanitation is poor. Ghanaian Examples: Cholera: A classic example. Drinking sachet water or municipal water contaminated with *Vibrio cholerae* bacteria leads to severe diarrhoea and dehydration. Typhoid Fever: Eating food, like waakye or kenkey, prepared by a food vendor who has the *Salmonella typhi* bacteria and did not wash their hands properly after using the toilet. Food Poisoning: Consuming food left uncovered and contaminated by flies, or food that has not been cooked or stored properly. Inoculation (Injection/Penetration) This involves a pathogen being introduced directly into the body through a break in the skin. Mechanism: Breaks in the Skin: Entering through cuts, wounds, or sores. Vector-borne Transmission: An insect (vector) bites a person and injects the pathogen directly into their bloodstream. Puncture Wounds: Being pricked by a contaminated object like a needle or a rusty nail. Ghanaian Examples: Malaria: The most common example in Ghana. An infected female *Anopheles* mosquito bites a person and injects the *Plasmodium* parasite directly into their blood. Tetanus: Stepping on a rusty nail can introduce *Clostridium tetani* bacteria deep into the tissue, causing tetanus ("lockjaw"). HIV/Hepatitis B: Sharing contaminated needles or sharp instruments (e.g., for drug use, traditional tattooing or scarification) can inject the virus directly into the bloodstream.
Summary Table
| Route of Exposure | Mechanism | Ghanaian Example Disease(s) | | :---------------- | :---------------------------------------------------------- | :------------------------ | | Direct Contact | Touching an infected person or their bodily fluids. | Ringworm, "Apollo", Ebola | | Inhalation | Breathing in airborne droplets or aerosols. | Tuberculosis, COVID-19 | | Ingestion | Eating or drinking contaminated food or water. | Cholera, Typhoid Fever | | Inoculation | Pathogen enters through a break in the skin (bite, cut, needle). | Malaria, Tetanus, HIV |