chapter 9 Flashcards
what happens to food after you’ve chewed it in your mouth?
your tongue forms the food into a rounded lump> tongue moves up & back to push it into the pharynx which connects to the oesophagus
-when you swallow the epiglottis (flap at back) closes so the food doesn’t go down your trachea.
What does the oesophagus do?
- it’s made up of circular and longitudinal muscle
- the bolus enters>circular muscle behind it contracts while muscle around and infront relaxes>pushes food down
- mucus is secreted to lubricate movement of food
- wave of contraction is called peristalsis
explain mechanical digestion in the stomach
- waves of muscular contraction of the oblique, circular and longitudianl muscle
- churn food and mix it with gastric juice
- converts to chyme>thick/soupy liquid
explain chemical digestion in the stomach
- gastric pits have gastric glands>secrete gastric juice>contains hydrochloric acid, mucus & digestive enzymes
- enzyme pepsin breaks amino acids into polypeptides> also kills bacteria
what regulates the flow of material in the stomach?
-pyloric sphincter, after 2-8 hours the contents is pushed into the duodenum
what gives the small intestine its large surface area?
- its very long (about 6m)
- inner lining, mucosa, has folds that extend into interior
- mucosa has small projections called villi which are covered in microvilli
explain digestion in the small intestine
intestinal juice=secreted by glands in the lining and contains enzymes that complete the digestion of carbohydrates, proteins and lipids
pancreatic juice=secreted by pancreas and helps neutralise acid that comes with stomach material, contains enzymes that complete the digestion of starch, proteins, DNA/RNA and lipids
bile=secreted by liver, stored in gall bladder and doesn’t contain digestive enzymes. bile salts break fat into tiny droplets to increases surface area so lipases can act (mechanical)
explain absorption in the small intestine
diffusion=high conc. gradient of nutrients in small intestine than villi cells
e.g. fatty acids & glycerol, water & vitamins
active transport=cells of villi use energy to take in nutrients against conc. gradient
e.g. amino acids, simple sugars
how does the digestion system work in the mouth?
mechanical=teeth/jaws break food into smaller pieces to increase surface area (biting>tearing>crushing)
chemical=salivary glands secrete saliva which contains mucus & salivary amylase to digest starch>breaking it down to smaller molecules
what is the large intestine and what happens in it?
- large in diameter
- no villi, no digestive juices
- large amount of mucus is secreted
- slow movement, 18-24 hrs, water is absorbed and bacteria breaks down organic compounds (vitamins produced and absorbed into blood)
whats the difference between elimination and excretion? which one is defecation?
elimination=removal of indigestible material
excretion=removal of metabolic wastes
defecation=elimination!
what’s the alimentary canal and what happens in it?
- tube that runs from mouth to anus
- together with organs it makes up the digestive system
- lining is where nutrients are absorbed
how does the diet affect absorption
e.g. meal size, protein/fat, alcohol/caffeine
large meal-greater stretching of stomach, material pushed into small intestine more quickly-more absorbed
high protein/fat-slows stomach movement from stomach to small intestine-more absorbed
alcohol/caffeine-stimulates movement-less absorbed
what is the importance of soluble fibre and where is it found?
- found in plant foods-fruit,veg,oat bran
- lowers cholesterol levels, risk of heart disease
- traps fats in intestines
what happens to make a person constipated?
- movements of large intestine are reduced and contents remains there for a long time
- water is absorbed-faeces become dry/hard
- caused by lack of roughage in diet, excerise, emotional issues
