digestion Flashcards
where does digestion of carbohydrates occur
stomach and small intestine
what enzyme digests carbohydrates
salivary and pancreatic amylase
where does the digestion of disaccharides (maltose, sucrose, lactose) occur
in the epithelial cells of the ileum
where is glucose absorbed
ileum
which comes first - ileum or duodenum
duodenum then ileum
how is glucose absorbed in digestion and what is it used for
secondary active transport and its used for production of ATP for aerobic respiration
how is excess glucose stored in the body
stored as glycogen in the liver and muscles
where are proteins digested
stomach and small intestine
in the stomach, what enzyme digests proteins
pepsinogen –> pepsin
what is pepsinogen secreted by
chief cells
what is the inactive form of pepsin (pepsinogen) activated by – what is it secreted by
HCl (oxyntic cells)
is pepsinogen an endopeptidase or exopeptidase
endopeptidase
in the duodenum, what endopeptidase enzyme digests proteins
trypsinogen –> trypsin
where is trypsinogen secreted from
the pancreas
what is trypsinogen activated by
enterokinase
in the duodenum, what else is there to digest proteins (apart from endopeptidases)
exopeptidases
where are the exopeptidases secreted from and what do they do
secreted from the pancreas, breaks down proteins into dipeptides then into amino acids
how are amino acids reabsorbed
active transport
what are amino acids used for
protein synthesis
what happens if there is an excess of amino acids
they are deaminated in the liver (converted to urea) - more than what the liver can deal with = converted to fat
where are lipids digested
duodenum
what are lipids digested by (enzyme)
lipases (secreted from the pancreas)
what are lipids digested into
3 fatty acids and a glycerol
how are fatty acids and glycerol absorbed
diffuse into the villus cells of the ileum, lacteal in the middle of the villi, transported around the lymphatic system until absorbed into the blood system
what are lipids used for
electrical insulation, making hormones, forming cell membranes, excess stored as fat
what type of digestion occurs in the buccal cavity (mouth)
mechanical and chemical
give 3 features of the tongue, lips and teeth
- move food around the mouth
- cut, grind and chew food into smaller pieces
- forms food into a bolus to make swallowing easier
what does salivary amylase convert starch into
starch –> maltose
what process does the oesophagus carry out
peristalsis
what is peristalsis
contraction of muscles in the gut wall to push the food forward through the whole gut
whats the function of the epiglottis
prevent food and liquid from entering the trachea/ vise versa
what does the epiglottis do when you begin to swallow
closes - to prevent food from entering the trachea and lungs
what type of digestion does the stomach carry out
chemical and mechanical
how is mechanical digestion carried out in the stomach
muscles in the stomach contracting and relaxing to mix food with gastric juice and to further breakdown large particles of food into smaller particles with a larger surface area for chemical digestion
what is the end result of digestion in the stomach called
chyme (pronounced kyme)
what do goblet cells secrete and why is this good
mucus - forms a barrier between the stomach lining and the gastric juice; protects the stomach wall and glands from self-digestion by pepsin and HCl
what are the names of the rings of muscle on either end of the stomach
pyloric (connects duodenum and stomach) and cardiac (connects oesophagus and stomach)
what are two secretions in the duodenum
bile from the liver, pancreatic juice from the pancreas
why does the small intestine have villi
increase the surface area for digestion and absorption
where are the crypts of lieberkuhn and what’s their function
found at the base of the villi IN THE DUODENUM, they release enterokinase
where are the Brunner’s glands found and what’s their function
in the duodenum, secretes alkaline fluid (containing sodium hydrogencarbonate) and mucus to neutralise the acid chyme from the stomach
why does increasing the length of the ileum make it the main site of absorption of digestion
food takes a relatively long time to pass through the ileum, thus increasing the time available for digestion and absorption
what increases the surface area in the ileum
villi, also has a rich blood supply to remove the products of digestion
where is most of the water in our food absorbed
in the ileum
what’s the first part of the large intestine called
the caecum
what’s the function of the caecum in humans and some animals
no role in the human digestive system, in some animals, this is the site of cellulose digestion
how would you describe the appendix and what’s it’s function in humans
blind-ended sac which opens from the caecum, no known role in digestion for humans
where is the undigested food and remaining water and minerals passed onto after the appendix/caecum
the colon
in the colon, what is absorbed
the rest of the water and mineral salts
whats absorbed by the colon
water, mineral salts and vitamins produced by microorganisms
what is the faeces made up of
semi-solid mass of undigested food, dead intestinal cells and bacteria
how would you describe the rectum
muscular tube that temporarily stores the faeces before they are eliminated from the body
what is the anus made from
sphincter muscles that control when defaecation occurs
name 3 functions of the liver
- excess glucose is stored as glycogen
- amino groups are removed from amino acids (de-amination) and converted into urea
- many vitamins are stored in the liver
name 2 functions of the pancreas
- ENDOCRINE: secretes the hormones insulin and glucagon for control of blood glucose levels, blood carries secretions to the site of action
- EXOCRINE: secretes pancreatic juice (mixture of enzymes and sodium hydrogencarbonate)
how and where is bile produced (where is it secreted)
liver produces bile by breaking down haemoglobin, stored in gall bladder and secreted into the duodenum through the bile duct
name the layers of the gut wall from outside to inside
serosa, longitudinal muscle, circular muscle, submucosa, mucosa (lumen)
what is the serosa
a layer of connective tissue carrying blood vessels, lymphatic vessels and nerves
what’s the function of the muscularis externa (longitudinal and circular muscles)
responsible for peristalsis
name the adaptations of villi
- rich capillary network to absorb and remove products of digestions and maintain a concentration gradient
- lacteals to absorb the products of fat digestion and maintain a concentration gradient
- thin to reduce diffusion distance
- microvilli increase surface area
- epithelial cells contain large numbers of mitochondria to provide the ATP for active transport
