Human Body Systems: Nutrition, Diets, and Waste Elimination

Posted on Jul 7, 2025 in Biology

Food: The set of processes that allows organisms to use and transform nutrients to stay alive.

Nutrition: The process by which nutrients are obtained from the external environment.

Energy Nutrients: Support the activity of all cells, warm the body, and fuel physical activity. Our body needs energy, thus requiring energy nutrients like carbohydrates and fats.
Structural Nutrients: Build our body tissues. Proteins primarily perform this function, but some lipids and mineral salts also contribute.
Functional and Regulatory Nutrients: These nutrients, such as vitamins and minerals, help properly carry out all life processes.

Carbohydrates: Energetic substances.
- Simple: Sweet, crystalline, and soluble in water. Examples include monosaccharides (directly used by cells) or disaccharides (two monosaccharides joined together).
- Complex: Neither sweet nor crystalline, consisting of many simple molecules. They often contain fiber.
Lipids: Insoluble in water, with an oily appearance.
- Fats: Provide energy. Classified by composition as saturated (animal) or unsaturated (vegetable, usually liquid).
- Components of Cell Membranes: Form the membranes of cells and cell organelles.
- With Regulatory Functions: Such as vitamins and protein hormones.
Proteins: Major structural molecules formed by 20 different amino acids. There are 8 essential amino acids.
Vitamins: Varied chemical composition, essential in very small quantities but can be destroyed by heat.
- Liposoluble: Soluble in lipids but not in water; accumulate in the liver.
- Water-Soluble: Soluble in water but not in lipids; do not accumulate.
Minerals: Inorganic substances. Some are part of bones, while others enable the proper functioning of bodily systems. They are found in all foods.
Water: The most abundant molecule in our body; acts as a solvent and is essential for life.

Mediterranean Diet: Traditional food of Southern European countries, including Spain. Considered one of the most balanced and healthy diets.
Hypocaloric Diet: Recommended for weight loss when it is excessive. These diets reduce calorie intake while maintaining nutritional balance.
Hypercaloric Diet: High energy food content, for people who are too thin and need to gain weight.
Low Cholesterol Diet: Recommended for people with high blood cholesterol levels, reducing the risk of cardiovascular diseases.
High-Fiber Diet: Includes many high-fiber foods for people with chronic constipation.
Soft Diet: Best for intestinal obstruction problems due to its low fiber content.

The excretory system eliminates waste substances from the blood and participates in the maintenance of the body’s vital signs.

Kidneys: Remove waste substances from the blood. They are two bean-shaped organs located at the back of the abdomen, on both sides of the vertebral spine. Each kidney is made up of over 1 million nephrons, which filter blood and produce urine that drains into collecting ducts and then into the renal pelvis. Kidneys also perform other physiological functions, including regulating the internal environment and secreting substances that stimulate the production of red blood cells or regulate blood pressure.
Urinary Tract: Conduits for the leakage of urine that connect the kidneys to the outside.
- Ureters: Narrow tubes that run from each kidney’s renal pelvis and flow into the urinary bladder.
- Urinary Bladder: An elastic bag that stores urine before it is expelled. When the bladder is full, nerve stimulation causes contraction, releasing urine into the urethra.
- Urethra: The tube that carries urine from the bladder to the outside. It has a sphincter that remains closed until the micturition reflex occurs.