236 OLIVE OILS AND HEALTH Cell differentiation is the process by which young, immature (non-specialised) cells progressively change in structure to become specialised for a specific function. The earliest human cells originate from the zygote (the first cell formed after the fusion of the sperm and the female egg during sexual reproduction) and they proliferate successively. At this early stage, they are capable of differentiating into any type of specialised cell, which is why they are referred to as totipotent cells (cells with the potential to give rise to all the cell types that make up the body). This differentiation process begins around the fourth day of development. As proliferation and differentiation progress, the cells gradually lose their ability to transform into other types. Eventually, the body’s various tissues develop, each with specialised cells adapted to their specific functions (brain, liver, kidney, skin, blood, etc.). In certain diseases such as cancer, abnormal and excessive cell proliferation occurs. Cancer cells may also undergo dedifferentiation, losing their resemblance to the normal cell from which they originated. The prognosis is generally worse for cancers that are both highly proliferative and poorly differentiated. CEREBROVASCULAR ACCIDENT -CVA- (See STROKE) CHLOROPHYLLS Green pigments found in leaves. Their molecules contain magnesium. Chlorophylls are essential for photosynthesis (also known as the chlorophyllic function), the process by which light energy is used to synthesise carbohydrates from carbon dioxide (CO₂) and water. CHOLESTEROL (See LIPIDS / Concepts) CHOLINE Choline is an organic base derived from the amino acid serine. It is synthesised in the body, mainly in the liver, but not in sufficient amounts to meet human needs, so it must also be obtained from the diet. It is therefore considered an essential nutrient, found in many foods, particularly beef liver, egg yolk, nuts, dairy products, and vegetables. Choline is important because it is a precursor of key substances. It is used in the synthesis of components of cell membranes (such as the phospholipid phosphatidylcholine, etc.). It is also the precursor of acetylcholine, a neurotransmitter involved in functions such as memory and muscle control. CIRCULAR ECONOMY (See PRODUCTIVE SYSTEMS) CIRRHOSIS Cirrhosis is a severe liver condition caused by scarring (fibrosis) of the liver following certain diseases. The liver becomes hardened and loses much of its functionality, and blood flow through the organ is impaired. In most cases, cirrhosis is the final stage of chronic liver damage resulting from long-standing liver disease. The main causes include chronic alcohol abuse, viral hepatitis B or C, and, less commonly, autoimmune or hereditary conditions, certain medications or toxins, and the accumulation of fat in the liver (steatohepatitis or fatty liver), particularly associated with obesity, type 2 diabetes, high blood lipid levels, and a sedentary lifestyle. (See also “Fatty liver”)
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