digestive system Flashcards
what is digestion?
the process of breaking down large nutrient molecules into smaller molecules which can be absorbed into the blood and cells
what is mechanical digestion?
physical breakdown of food into smaller pieces to increase surface area
what is mechanical digestion?
what are the 3 location where mechanical digestion occurs?
mouth = teeth cut, tear and grind food
stomach = churning action breaks down food further
bile = emulsifies fates (breaking fat down into smaller droplets)
how does mechanical digestion help speed up absorption of nutrients?
increase surface area allows more effective chemical digestion as the chemicals can access more food
what is chemical digestion?
uses enzymes to break bonds of large complex molecules into smaller, simpler ones.
what digestive enzymes are involed in chemical digestion of nutrients?
amylase = breaks down starch into maltose. maltase breaks down maltose into glucose
pepsin = breaks down proteins into peptides and amino acids
lipase = breaks down lipids into fatty acids and glycerol
nucleic acids = are split into nucleotides
what is the alimentary canal?
continuous tube that runs from the mouth to the anus, including all digestive organs
how does food get chemically and physically digested in the mouth?
mechanical - teeth, chewing
chemical - as food is chewed it is mixed with saliva which contains amylase which begins chemical digestion of starch into maltose
tongue shapes food into a bolus. it moves up and back pushing bolus to the pharynx which leads to the oesophagus
what is peristalisis?
Involuntary waves of muscle contraction that keep food moving along in one direction
what is the structure of the oesophages?
- tube that connects pharynx to stomach (23-25cm).
- wall has a double layer of muscle - circular and longitudinal muscle
describe the structure of the stomach
enlarged section of the alimentary canal.
food undergoes chemical and mechanical digestion
nutrients are not absorbed into the bloodstream through the stomach because the internal surface is covered by a thick layer of mucus.
folds unfold to accommodate what you’re eating.
describe mechanical digestion in the stomach
mechanical - waves of muscular contraction. has oblique, circular and longitudinal muscle so stomach can contract in many ways, churning the food and mixing it with gastric juice.
describe chemical digestion in the stomach
chemical - enzymes (pepsin/gastric protease) in the gastric juice. breaks the bonds between certain amino acids breaking proteins into shorter polypeptide chains.
what is the function of the thick mucus in the stomach?
protects stomach lining and prevents it from digesting itself
what is the pyloric sphincter?
- between the stomach and duodenum.
- regulates flow of material from stomach into the duodenum
what is gastric juice?
- contains HCl, mucus and digestive enzymes (pepsin)
- stomach lining is specialised for secretion of gastric juice
what is a bolus?
food after it has been chewed and mixed with saliva
what is chyme?
Partially digested, semiliquid food mixed with digestive enzymes and acids in the stomach.
what is the small intestine?
- 6-7m long.
- receives material pushed through pyloric sphincter from the stomach.
what are the 3 regions of the small intestine?
duodenum, jejunum, ileum
what is the duodenum and its function?
- first part of the small intestine.
- receives acidic food from stomach and secretes alkaline juice.
- most chemical digestion occurs here before chyme moves further
what is the jejunum and its function?
- middle section.
- its lining allow effective absorption of carbs and proteins - not fats
what is the ileum and its function?
- final part.
- B12, bile salts and any remaining productions of digestion are absorbed
what is bile and how does it help in digestion?
- enters duodenum through the common bile duct.
- contains no digestive enzymes, but has bile salts which emulsify fats.
- break the fat into tiny droplets
how does pancreatic juice help with digestion?
- produced by pancreas which contains many enzymes.
= pancreatic amylase - helps break down starch
= pancreatic protease - breaks down proteins into small chains of amino acids
= ribonuclease and deoxyribonuclease - digest RNA and DNA
= pancreatic lipases - break down fats into fatty acids and glycerol
how does intestinal juice help with digestion?
pancreatic protease - breaks down proteins into small chains of amino acids
ribonuclease and deoxyribonuclease - digest RNA and DNA
pancreatic lipases - break down fats into fatty acids and glycerol
how does absoption occur in the small intestine?
- products of digestion, vitamins, minerals and water are absorbed through the wall of the small intestine into the blood.
- the lining has folds to maximise the absorption of nutrients
how does absorption occur in the small intestine
what are villi?
finger like projections that increase the SA for absorption
how are amino acids and simple sugars absorbed in the small intestine?
absorbed by active transport into the blood capillaries to the liver
what is the structure of the large intestine?
- 1.5m long.
includes caecum, colon, rectum, anus, appendix - no villi, no digestive juices secreted.
what is the functin of the large intestine?
lining secretes lots of mucus
most of the remaining water is absorbed so the contents become more solid
what is the colon?
longest part of large intestine. has an inverted u shape
what is the caecum?
- pouch
- 6cm long
- where small intestine joins large intestine
what is the appendix?
small tube attached to the caecum
what is the anus?
external opening at the end of the rectum
what is the rectum?
- last part of large intestine.
- material left in colon after water absorption is pushed into rectum by peristalsis.
what does faeces contain?
water, undigested food, cellulose, bacteria, bile pigments.
- remains of cells that have broken away from the internal lining of canal
what is the gall bladder?
pouch near liver that stores bile produced in the liver.
what is bile?
contains bile salts which break up fats so lipases can act on a larger SA.
- neutralises acidity of food coming from stomach, enabling lipase its optimal high pH.
- contains no enzymes
what is the pancreas?
produces pancreatic juices containing enzymes and neutralise acids from the stomach
what are salivary glands?
secrete saliva containing amylase and mucus that lubricates, dissolves food and holds food in lump
what is the role of the liver
produces bile
what lifestyle choices have an effect of digestion?
activity level, drugs, diet
- cause conditions like constipation, diarrhoea, bowel cancer and coeliac disease
what are the causes and symptoms of constipation?
- caused by lack of cellulose and fibre in diet, lack of exercise, emotional problems.
- leads to excess water reabsorbed as the food remains in large intestine too long
- painful and infrequent defection
what are the treatment options for constipation?
- Drinking more fluids
- eating more high-fibre foods
- getting regular exercise
what are the causes and symptoms of diarrhoea?
- caused by bacteria, virus or parasite
- results in quicker peristalsis so not enough water is absorbed and irritation of intestines
- watery and frequent faeces
what are the causes and symptoms of bowel cancer?
- uncontrolled growth of cells in the walls of the large intestine
- caused by diet high in processed meat and low in fibre, high alcohol consumption and smoking
- pain in abdomen, blood in stool, change in bowel habits,
what are causes of coeliac disease?
caused by abnormal immune reaction to gluten.
what are the treament for coeliac disease?
strict gluten free diet
what are the treament for coeliac disease?
strict gluten free diet
