Lesson Notes By Weeks and Term v4 - SHS 3
DISEASES AND DISORDERS
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DISEASES AND DISORDERS
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Subject: Biomedical Science
Class: SHS 3
Term: 2nd Term
Week: 15
Grade code: 3.2.2.LI.3
Strand code: 2
Sub-strand code: 2
Content standard code: 3.2.2.CS.1
Indicator code: 3.2.2.LI.3
Theme: HUMAN BODY SYSTEMS
Subtheme: DISEASES AND DISORDERS
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This lesson explores the critical role of cholesterol and its transporters, Low-Density Lipoprotein (LDL) and High-Density Lipoprotein (HDL), in our health. In Ghana, as lifestyles change, we are seeing a rise in non-communicable diseases like hypertension, stroke, and heart attacks. Understanding how the "good" and "bad" cholesterol in our blood affects our arteries is the first step in preventing these life-threatening conditions. We will investigate what LDL and HDL are, how they work, and how their levels directly impact our risk of developing cardiovascular disease. This knowledge empowers us to make healthier dietary and lifestyle choices for ourselves and our families.
A. What is Cholesterol? Cholesterol is a waxy, fat-like substance that is found in all the cells in your body. Your body needs some cholesterol to make important things like: Hormones: (e.g., estrogen, testosterone) Vitamin D: Essential for bone health. Cell Membranes: It provides structure and stability to the outer layer of your cells.
Your liver produces all the cholesterol your body needs. However, you also get cholesterol from the food you eat, especially animal products like meat, eggs, and dairy. B. The Transport Problem: Why Lipoproteins? Think about mixing oil and water. They don't mix! Blood is mostly water, and cholesterol is a lipid (fat). For cholesterol to travel through your watery bloodstream to reach the cells that need it, it must be packaged into special carriers called lipoproteins. A lipoprotein is a particle made of fat (lipid) on the inside and protein on the outside. The protein coating allows the entire package to dissolve in the blood and be transported.
The two most important lipoproteins we will discuss are LDL and HDL. C. Low-Density Lipoprotein (LDL) - The "Bad" Cholesterol Function: LDL's job is to be the primary delivery truck. It transports cholesterol from the liver to cells throughout the body. Why it's "Bad": When you have too much LDL in your blood, it's like having too many delivery trucks on a small road. They start to crash and spill their cargo. Excess LDL particles can deposit their cholesterol into the walls of your arteries. The Process of Atherosclerosis (Hardening of Arteries): This is the dangerous consequence of high LDL levels. Damage & Invasion: The inner lining of an artery (the endothelium) can get damaged (e.g., by high blood pressure or smoking). Excess LDL particles in the blood then enter the artery wall at this site of injury. Oxidation: Once inside the artery wall, the LDL cholesterol gets chemically changed (oxidized), which triggers an inflammatory response. Foam Cell Formation: The body's immune cells (macrophages) rush to the site to "clean up" the oxidized LDL. They engulf so much of it that they become swollen and look foamy. These are now called "foam cells". Plaque Formation: These foam cells, along with other lipids and cell debris, accumulate in the artery wall, forming a deposit called a plaque. Narrowing of Arteries: Over time, this plaque grows, making the artery wall thicker and harder, and narrowing the space for blood to flow through. This condition is atherosclerosis. Blockage and Rupture: If the artery becomes too narrow, blood flow to the heart muscle (if it's a coronary artery) or brain can be severely restricted, causing chest pain (angina). Worse, the plaque can suddenly rupture or crack. The body tries to heal this rupture by forming a blood clot (thrombus). This clot can completely block the already narrowed artery, cutting off all blood supply. Result: A blocked coronary artery causes a heart attack. A blocked artery leading to the brain causes an ischemic stroke. D. High-Density Lipoprotein (HDL) - The "Good" Cholesterol Function: HDL acts as the "garbage collector" or "recycling truck". Its job is to scavenge for excess cholesterol in your tissues and from the walls of your arteries (even from existing plaques) and transport it *back* to the liver. The liver then processes this cholesterol for removal from the body. Why it's "Good": By removing excess cholesterol from the artery walls, HDL helps to prevent or even reverse the buildup of plaque. A high level of HDL is protective against heart disease. Therefore, having low levels of HDL is a significant risk factor, as it means there aren't enough "garbage collectors" to clean up the arteries. E. Measuring Cholesterol: The Lipid Profile A doctor uses a simple blood test called a lipid profile or lipid panel to measure your cholesterol levels. The results are usually given in milligrams per decilitre (mg/dL).
| Component | Desirable Level | Borderline High | High Risk | | :--- | :--- | :--- | :--- | | Total Cholesterol | Less than 200 mg/dL | 200–239 mg/dL | 240 mg/dL and above | | LDL Cholesterol | Less than 100 mg/dL | 130–159 mg/dL | 160 mg/dL and above | | HDL Cholesterol | 60 mg/dL and above (Protective) | 40–59 mg/dL | Less than 40 mg/dL (Major Risk Factor) |