Digestive System Flashcards
Components, Layers of the Gut & Worms
What is the role of the digestive system?
It’s responsible for chemically and physically digesting large insoluble molecules into smaller soluble molecules, which can be absorbed into the blood stream,
And used for bodily processes (e.g. respiration, protein synthesis).
Buccal Cavity-
Chemical Digestion
Amylase breaks down starch and glycogen into maltose
Buccal Cavity-
Saliva
Moistens food and maintains pH (for enzyme activity)
Buccal Cavity-
Mechanical Digestion
The tongue moves food to the cutting and grinding surfaces of the teeth
Tongue rolls food into a bolus which is swallowed
Bolus
a ball like mixture of food and saliva that forms during chewing (mechanical digestion) which is swallowed into the stomach
It’s the same colour as the food eaten, and saliva gives it an alkaline pH
Oesophagus
A long tube which extends from the buccal cavity to the stomach.
It’s responsible for pushing the bolus into the stomach using peristaltic waves of muscle contraction. It’s also lubricated with mucus.
Layers of the gut
Serosa (outermost)
Muscle Layers
Sub-mucosa
Mucosa
Lumen
Serosa
The outer most layer of the gut made of a thick tough connective tissue to provide protection.
Muscle Layers
The second outer most layer of the gut. Used to contract in waves and squeeze food down (peristalsis)
Sub mucosa
The second inner most layer of the gut. Contains connective tissue, nerves, blood & lymph capillaries
Mucosa
Inner most layer of the gut. This area secretes mucus and can secrete digestive juices.
In the ileum it’s covered with microvilli to increase SA
Stomach
A J shaped organ found at the end of the oesophagus which physically churns up food using muscles from the stomach wall
It also chemically breaks down food by releasing gastric juices
Mucus
Produced by goblet cells throughout the digestive system (e.g. stomach) to lubricate food and protect organ walls from self digestion via enzymes
Gastric Juice
A digestive fluid produced within the stomach lining with an acidic pH made up of mainly HCl, mucus, endopeptidase (pepsin), lipase
What produces gastric juice?
Gastric glands in the mucosa
Oxyntic Cells
Produce hydrochloric acid (HCl) in the stomach which kills bacteria and lowers pH down to 2 (for optimum pepsin enzyme activity)
Pepsinogen
The inactive form of endopeptidase (pepsin) which is activated by HCl to break down polypeptides into peptides
Liver
Produces Bile
Gall Bladder
Stores Bile and releases it to the duodenum from the bile duct
Bile
Emulsifies lipids to maximise the SA for lipase enzyme action & digestion/absorption
Alkaline in pH to neutralise stomach acid and form slightly alkaline (food)
Pancreas
Produces enzymes that are released into the duodenum via the pancreatic duct
Pancreatic Juice
The pancreatic enzymes produced by the pancreas and released into the duodenum by the pancreatic duct (slightly alkaline in pH)
What (pancreatic) enzymes does the pancreas produce?
Carbohydrase (pancreatic amylase)
Lipase
endo & exopeptidase
Duodenum
The start of the small intestine (connected to the stomach) where food is further digested on the epithelial cells of the villi
What enzymes are in the duodenum?
amylase
maltase
lactase
sucrase
endopeptidase
exopeptidase
dipeptidase
Amylase
A type of carbohydrase which hydrolyses starch into maltose
It is found in the mouth (from salivary glands) and duodenum (from pancreas)
Maltase
A type of disaccharidase which hydrolyses maltose into alpha glucose
Found membrane bound in the duodenum
Sucrase
A type of disaccharidase which hydrolyses sucrose into glucose and fructose
Found membrane bound in the duodenum
Lactase
A type of disaccharidase which hydrolyses lactose into glucose and galactose
Found membrane bound in the duodenum
(pancreatic) Lipase
Hydrolyses triglycerides into monoglycerides (and then eventually into fatty acid and glycerol)
Endopeptidase
A type of protease which hydrolyses non-terminal (central) peptide bonds to form smaller poly peptides
Found in the stomach and duodenum
Trypsinogen
The inactive form of Trypsin (a type of endopeptidase) which becomes activated by enterokinase
Exopeptidase
Type of protease which hydrolysis terminal (end) Peptide bonds to form dipeptides and amino acids
Found in the stomach and ileum
Dipeptidases
Type of protease which hydrolyses specifically peptide bonds on dipeptides to form amino acids
Found membrane bound in the duodenum
Absorbing Glucose
Na+ actively transported out of the ileum into the blood using sodium potassium pump. (Low concentration in ileum cells).
Na+ diffuses from lumen to epithelium by sodium glucose co transporter.
Glucose then diffuses out of the cell into the bloodstream through facilitated diffusion
Absorbing Amino Acids
Active transport using carrier proteins into villi cells and then facilitated diffusion into capillaries
Absorbing minerals
facilitated diffusion and active transport
Absorbing fats
Lipase breaks down lipids into monoglycerides & fatty acids
Bile & lipase act on the triglycerides to form a micelle made up of monoglycerides, fatty acids and bile salts
Break and move into the cell membrane, reform before moving to the ER or Golgi
Modified into chylomicrons, which allow them to move into the lacteal by exocytosis and then be drained into the blood
Ileum
The final part of the small intestine (connected to the duodenum) which mainly absorbs any left over nutrients/substances
Colon
The longest section of the large intestine, which is responsible for absorbing any excess water and some nutrients
Rectum and Anus
Rectum- lower part of the large intestine where faeces (waste products of digestion) are stored
Anus- the opening at the end of the rectum where faeces are released from
Tapeworm
A (parasite) disease caused by eating uncooked/ raw meat or by not washing hands
The heads attach to the inner walls of the small intestine and feed off food being digested
Identifying Tapeworms
Pieces of white, flat, rectangular worms in the faeces about the size of a grain of rice
Symptoms of Tapeworm
tummy pain
diarrhoea
nausea
vomiting
weight loss
change in appetite
Transmission of Tapeworm
raw/undercooked meat
faecel contaminated water
very close contact to those infected
Treating Tapeworm
Anti Worm medication
Reducing spread of Tapeworm
food well cooked
fruit & veg throughly washed
only drink clean water
Hands thoroughly washed before food, after toilet or after touching animals
