basic principles of nutrition and healthy eating Flashcards
digestion definition
the process by which foods are broken down into smaller molecules or nutrients
absorption
the uptake of nutrients and how the body utilises these nutrients to perform a wide range of bodily functions
Excretion
the means by which the body removes unwanted, unnecessary or harmful substances from the body once it has extracted what it needs
the body’s two mechanisms for breaking down food consumed
mechanical
chemical
mechanical digestion
chewing/mastication
also involves rolling of tongue to create small balls of mixed food = ‘bolus’
not limited to mouth - continues throughout digestive system using ‘peristalsis’
the smooth muscle tissue of the walls of digestive organs involuntarily contract to push foods along. cylindrical shape of digestive tract is optimal for this process.
chemical digestion
how the body breaks down foods into simpler nutrients using enzymes
enzymes are protein molecules that accelerate specific chemical reactions
speed up rate of digestion - would be too slow to sustain life without them
the digestive tract
also known as alimentary tract, alimentary canal, gastrointestinal tract
mouth to anus
transit time = time for food to pass through the tract
for healthy adult transit time 24-72 hours
av tract is 9meters long
3 functions saliva
1) moistens food so tongue can form ‘bolus’
2) starts carbohydrate digestion - contains amylase which breaks it down into glucose
3) be present in food consumed
pharynx
has both digestive and respiratory functions
forms passageway connecting the mouth and nose to oesophagus and larynx
3 diff muscles
primary structure for swallowing ~ a reflex ~ 1-3 seconds
oesophagus
approx 10 inches in length
connects throat to stomach
runs parallel to trachea
protected by cartilage called ‘epiglottis’ ~ seals the trachea so food is transported to stomach and not lungs
with medium bolus take about 5-8 seconds for food to get to stomach
stomach
J shaped
can expand 8 times the size
located just left to centre of chest - below sternum
3 layers of tissue
gastric juices with food creates chyme
hydrochloric acid kills invading bacteria - so corrosive that stomach lined with mucus to prevent digesting itself
pepsin - breaks down protein - can only work in vv acidic conditions
emptying of stomach takes 3-4 hours depending on food consumed, hydration and physical activity levels
moves onto small intestine
alcohol is only substance that is directly absorbed into stomach
functions of pancreas
producing and releasing enzymes for digestion (trypsin, amylase, digest
creating and releasing blood regulating hormones (insulin and glucagon)
produces bicarbonate - neutralises acidity
Gall Bladder and Bile Duct
below liver
gallbladder stores bile produced by liver and delivers to small intestine via bile ducts
the liver
storage of carbs in form of glycogen hormone production blending and emulsification of fats excretion of old blood cells production of bile storage in the gall bladder production of cholesterol filters and neutralises toxins storage of some vitamins and iron
small intestine
longest of intestinal tracts - 5-6 metres first section (10 inches) is the duodenum second section (3-4 metres) is the jejunum = most nutrient absorption takes place final section (3-4 cm) is the ileum = remaining nutrients absorbed inside the small intestine are cilia - hair like structures that provide large surface area to increase rate of absorption - they have a rich blood supply food absorbed goes to liver which is good for nourishing it but bad when has to detoxify from substances like alcohol to prevent cellular damage. takes bout 3-4 hours for food to pass through SI - but varies according to different factors
