Diet and digestion

• Human nutrition involves balancing a diet to ensure all the necessary components are present in appropriate proportions.
• Energy requirements vary depending on the individual's age, activity levels, and gender.
• Females tend to have lower energy requirements than males due to their lower body mass and increased energy needs during pregnancy and breastfeeding.
• A balanced diet should include carbohydrates, lipids, proteins, vitamins, minerals, and dietary fibre.
• Malnutrition is a condition where certain nutrients of a balanced diet are missing, excessive, or taken in the wrong proportions.
• Starvation occurs when a person has a severe deficiency of energy, nutrient and vitamin intake for an extended period of time.
• Coronary heart disease can be caused by consuming too much saturated/animal fat in the diet, which can accumulate in the walls of arteries as plaque, causing blockage.
• Egestion is the process by which faeces pass out of the body through the anus.
• The remaining water and nutrients after absorption are known as faeces.
• Absorption is the process by which the body absorbs water and other nutrients from food.
• Faeces are stored in the rectum, the last part of the large intestine.
• Constipation occurs when there is infrequent bowel movements and faeces are not expelled.
• A person is considered obese if his/her body weight is 20% above the standard body weight, due to an over-abundance of calorie intake, increased dependence on fast food and sugary foods.
• Scurvy is caused by the lack of vitamin C in the diet, with symptoms including bleeding under the skin, swollen and bleeding gums, and poor healing of wounds.
• Carbohydrates, lipids, proteins, vitamins, minerals, and dietary fibre are classes of food.
• Vitamins are not digested or broken down for energy, are essential in small quantities for health, and are needed for chemical reactions in the cells, working in association with enzymes.
• Mineral ions are only needed in small amounts to maintain a healthy body, and a lack of the correct mineral ions in the diet also leads to deficiency symptoms.
• Dietary fibre is found in material that cannot be digested, particularly cellulose from plant cell walls, and is important because it provides bulk, which helps the walls of the intestine move food and faeces along the gut, and also absorbs toxins from our food.
• Water makes up about two-thirds of the human body, is found in the cytoplasm of our cells and in body fluids like blood.
• Nerves run through each tooth and periodontal ligament, making the teeth sensitive to a wide variety of stimuli.
• Dentine is located under the enamel and looks quite similar to bone, but is not as hard as enamel.
• The molar tooth is used for grinding or crushing food.
• Tooth decay, also known as dental caries, happens when the hard outer enamel of the tooth is damaged, which can happen when bacteria in the mouth respire sugars, converting them into acids that react with the enamel.
• Amylase, Protease, Lipase, and Maltase are major enzymes that break down starch, protein, fat, and maltose respectively, and are secreted and function in different parts of the alimentary canal.
• Trypsin is secreted by the pancreas in an inactive form, which is changed to an active enzyme in the duodenum and is responsible for breaking down proteins to peptides.
• Chemical digestion requires enzymes, which involve breaking down large insoluble molecules to small soluble molecules that can be absorbed through the epithelium of the alimentary canal, through the walls of the blood vessels and into the blood.
• Chewing is a mechanical digestion process performed by the teeth, where pieces of food are mixed with saliva and become smaller, easier to swallow and have a larger surface area.
• The stomach produces hydrochloric acid (HCl) which kills many harmful microorganisms (bacteria) that might have been swallowed along with the food, denaturing enzymes in the harmful bacteria and providing the optimum conditions for pepsin, an enzyme that works best in very acidic conditions and only breaks down proteins at an optimum pH of 2.
• Bile, after it has been in the stomach, travels to the small intestine.
• The crown of the tooth is the part that is visible above the gum line.
• The gum is a tissue that overlays the jaws.
• The root of the tooth is the rest of the teeth, embedded in the jaw bone.
• Cement is the layer of bone-like tissue covering the root of the tooth, not as hard as enamel.
• Pepsin is secreted in the stomach and acts on proteins, breaking them down into smaller compounds called peptides.
• The premolar tooth is used for grinding or crushing food.
• Enamel covers the tooth crown and is very hard, preventing the tooth from decaying.
• The incisor tooth is used for biting off and cutting pieces of food.
• The canine tooth is used for holding and ripping food.
• Pulp is found at the center of the tooth and contains blood vessels, nerves and soft tissues which deliver nutrients to the tooth.
• Infection, plant toxins, and digestive failure can also cause kwashiorkor.