Human Nutrition Flashcards
Rickets
Rickets is a condition in children characterised by poor bone development
Symtpoms include:
Bone pain
Lack of bone growth
Soft, weak bones (sometimes causing deformities)
Rickets is caused by a severe lack of vitamin D
Vitamin D is required for the absorption of calcium into the body
Calcium is a key component of bones and teeth
Vitamin D mostly comes from exposure to sunlight but it can also be found in some foods (fish, eggs and butter)
The treatment for rickets is to increase consumption of foods containing calcium and vitamin D
Alternatively vitamin D supplements can be prescribed
Scurvy
Scurvy is the name for a severe vitamin C deficiency
It is caused by a lack of vitamin C in the diet for over 3 months
Its symptoms include:
Anemia
Exhaustion
Spontaneous bleeding
Pain in the limbs
Swelling
Gum ulcerations
Tooth loss
Stages of food breakdown
Ingestion - the taking of substances, e.g. food and drink, into the body through the mouth
Mechanical digestion - the breakdown of food into smaller pieces without chemical change to the food molecules
Chemical digestion - the breakdown of large, insoluble molecules into small, soluble molecules
Absorption - the movement of small food molecules and ions through the wall of the intestine into the blood
Assimilation - the movement of digested food molecules into the cells of the body where they are used, becoming part of the cells
Egestion - the passing out of food that has not been digested or absorbed, as faeces, through the anus
Physical Digestion
Physical digestion (sometimes referred to as mechanical digestion) is the breakdown of food into smaller pieces without chemical change to the food molecules
The processes that take place during physical digestion help to increase the surface area of food for the action of enzymes during chemical digestion
It is mainly carried out by the chewing action of the teeth, the churning action of the stomach and the emulsification of fats by bile in the duodenum
Types of Human Teeth
Mechanical digestion is the breakdown of food into smaller pieces without chemical change to the food molecules
It is mainly carried out by the chewing action of the teeth, the churning action of the stomach and the emulsification of fats by bile in the duodenum
Teeth are held firmly in the bone of the jaw
They are used for chewing to increase the surface area of the food so that it can be exposed to saliva and other digestive juices and broken down more quickly
The differing shapes and sizes of teeth enable them to perform slightly different functions:
Incisors - chisel-shaped for biting and cutting
Canines - pointed for tearing, holding and biting
Premolars and molars - larger, flat surfaces with ridges at the edges for chewing and grinding up food
Emulsification of Fats & Oils
Cells in the liver produce bile which is then stored in the gallbladder
Bile has two main roles:
It is alkaline to neutralise the hydrochloric acid which comes from the stomach
The enzymes in the small intestine have a higher (more alkaline) optimum pH than those in the stomach
It breaks down large drops of fat into smaller ones. This is known as emulsification. The larger surface area allows lipase to chemically break down the lipid into glycerol and fatty acids faster
How is a low pH helpful in the stomach?
The low pH kills bacteria in food that we have ingested as it denatures the enzymes in their cells, meaning they cannot carry out any cell reactions to maintain life
Pepsin, produced in the stomach, is an example of an enzyme which has a very low optimum pH - around pH 2
The hydrochloric acid produced in the stomach ensures that conditions in the stomach remain within the optimum range for pepsin to work at its fastest rate
Digestion of Starch
Amylases are produced in the mouth and the pancreas (secreted into the duodenum)
Amylases digest starch into smaller sugars
Amylase is secreted into the alimentary canal in the mouth and the duodenum (from the pancreas) and digests starch to maltose (a disaccharide)
Maltose is digested by the enzyme maltase into glucose on the membranes of the epithelium lining of the small intestine
Digestion of Protein
Proteases are a group of enzymes that break down proteins into amino acids in the stomach and small intestine (with the enzymes in the small intestine having been produced in the pancreas)
Protein digestion takes place in the stomach and duodenum with two main enzymes produced:
Pepsin is produced in the stomach and breaks down protein in acidic conditions
Trypsin is produced in the pancreas and secreted into the duodenum where is breaks down protein in alkaline conditions
Bile
Cells in the liver produce bile which is then stored Bile has two main roles:
It is alkaline to neutralise the hydrochloric acid which comes from the stomach
The enzymes in the small intestine have a higher (more alkaline) optimum pH than those in the stomach
It breaks down large drops of fat into smaller ones. This is known as emulsification. The larger surface area allows lipase to chemically break down the lipid into glycerol and fatty acids fasterin the gallbladder
Adaptations of the Small Intestine
The ileum is adapted for absorption as it is very long and has a highly folded surface with millions of villi (tiny, finger like projections)
These adaptations massively increase the surface area of the ileum, allowing absorption to take place faster and more efficiently
Microvilli on the surface of the villus further increase surface area for faster absorption of nutrients
Wall of the villus is one cell thick meaning that there is only a short distance for absorption to happen by diffusion and active transport
Well supplied with a network of blood capillaries that transport glucose and amino acids away from the small intestine in the blood
Lacteal runs through the centre of the villus to transport fatty acids and glycerol away from the small intestine in the lymph
