The digestive system Flashcards
what are the for types of tissues in animals
muscle tissue, nervous tissue, connective tissue and epithelial tissue
what is the purpose of the digestive system
cells of an organism require nutrients and for vertebrates digestion of food is the first important step that must occur. some nutrients can dissolve in water and redily enter cells but some are too large and must be broken down into smaller units
definition of digestion
the chemical process of breaking down large organic molecules into a size that can pass across plasma membranes and around the body
what are the four main specialised functions in the digestive system
ingestion, digestion, absorption and egestion
function of ingestion
the taking in of nutrients
the function of digestion
the breakdown of complex organic molecules into smaller components by mechanical and chemical means
the function of absorption
the taking up of digested molecules into the cells of the digestive tract through the cell membrane
the function of egestion
the removal of waste food materials (unabsorbed food) from the body
what is mechanical or physical digestion
when large pieces of food are broken down into smaller pieces of the same food, chemically the food stays the exact same
when does mechanical/physical digestion occur
chewing, the cutting up of food. peristalsis, the muscular contractions of the stomach and bile which is produced in the liver and emulsifiers lipids, breaking up fatty masses into smaller droplets
what is the aim of mechanical/physical digestion
to increase surface area of the food so chemical digestion can happen at a faster rate
what is chemical digestion
when enzymes break down complex structures into their simplest forms, they go from polymers to monomers
what is the alimentary tract
the tube from the top to the bottom of the digestive system
what does the alimentary tract include
the mouth, oesophagus, stomach, small intestine, large intestine, rectum and anus
what are the accessory glands of the digestive system
salivary glands, gall bladder, liver and pancreas and others which contribute vital subtstancea to the functions of the system
what happens in the mouth
teeth mechanically break down food, saliva contains amylase which digests starch into maltose, saliva lubricates food which makes it easier to swallow. the epiglottis closes off the trachea so food bolus goes down the oesophagus
what is peristalsis
undirectional muscular contractions which allow fod to move along the digestive system and break it down further
what happens in the stomach
mechanical digestion occurs as the muscles of the stomach wall relax and contract (peristalsis), the food is now called chyme. gastric juice is secreted from the cells lining the stomach walls.
what is pepsinogen and its purpose
it is converted into the active enzyme pepsin where it then acts on the peptide bonds between amino acids, breaking down the long protein chains into smaller amino acids
what are the three regions of the small intestine
the duodenum, jejunum and ileum
what are the two functions of the small intestine
digestion - further and final digestion of all organic molecules including carbohydrates, proteins and lipids. absorption - of digested molecules into the bloodstream
what happens in the small intestine
pancreatic enzymes and intestinal enzymes enter the duodenum at the top of the small intestine which contain enzymes
what is pancreatic juice
contains a mixture of amylase, trypsin, lipase and bicarbonate. the bicarbonate neutralises the acidity of the digested food which stops the action of pepsin
what is bile, where is it produced and stored?
its produced in the liver and passes down the bile duct and into the duodenum but is stored in the gall bladder if there is no food to digest. its involved in the mechanical digestion of fats by emulsifing them into smaller pieces
what do lipases do
they are enzymes that are produced in the pancreas and chemically break down fat into fatty acids and glycerol
what happens to amino acids, simple sugars, vitamins and minerals digestive system
they are absorbed into the blood capillaries via active transport
what happens to fatty acids and glycerol
they are lipid soluble so can easily diffuse through the membranes of the intestinal walls
what happens to water once it reaches the intestines
90-95% of water is absorbed by osmosis, the rest is disposed of
what happens to carbs, starch, proteins and lipids in the digestive system
if they are too large of a molecule to directly cross the plasma membrane, the are broken down into their simplest forms by enzymes
how to enzymes break down food molecules
by the process of hydrolysis - where a molecule of water breaks down one or more chemical bonds
what enzyme breaks down and what is the smallest unit of carbs
carbohydrase, smallest unit is monosaccharides
what enzyme breaks down and what is the smallest unit of starch
amylase and peptidase, smallest unit is maltose
what enzyme breaks down and what is the smallest unit of protein
protease, smallest unit is amino acids
what enzyme breaks down and what is the smallest unit lipids
lipase, smallest unit is fatty acids and glycerol
what is the main function of the large intestine
compact undigested food and to absorb water and some salts back into the body
what are the two non-primary functions of the large intestine
bacteria in the colon act on undigested matter, producing vitamin a and k. and peristalsis including in the rectum
what is in gastric juice
this substance contains, mucus,water, hydrochloric acid and pepsinogen
