U6 - Digestion system Flashcards
to shit
Difference between chemical and physical digestion?
physical - mechanical reduction and movement of the food molecules into absorbable units
chemical - organic polymers are broken down by hydrolytic enzymes
Proteins are broken down into absorbable components
short peptides ——> amino acids
Carbohydrates are broken down into absorbable components
disaccharide ——–> monosaccharides
Fats are broken down into absorbable components
glycerol + fatty acids
Nucleic acids are broken down into
nucleotides
Components of saliva
a. 99% water
b. also salivary amylase, an enzyme which
hydrolyses starch into maltose, and mucus
The process of swallowing
- tongue pushes food to the back of the
mouth - epiglottis contracts and folds down to close
the opening to the trachea - tongue pushes food further back into the
pharynx, and food enters esophagus
4, epiglottis relaxes and opens the trachea
Describe peristalsis
rhythmic contraction of muscles
propelling food through the digestive tract
components of gastric juice
hydrochloric acid – produces a pH of about
2, breaks down food, kills most bacteria
pepsinogen – in acid becomes pepsin,
enzyme which hydrolyses protein into shorter
polypeptides
Sphincters at entrance at exit of stomach
cardiac sphincter – allows food in from
esophagus, closes to prevent acidic stomach
contents from moving back up
pyloric sphincter – opens and closes to
control movement of food into the
duodenum, first part of the small intestine
Functions of the liver
- production of bile – bile emulsifies fat by
breaking it into smaller droplets, stored in
the gall bladder until needed - storage of nutrients – glycogen, fat-soluble
vitamins, and minerals - nutrient metabolism – metabolism of
carbohydrates, proteins, and lipids - detoxification of blood – drugs and toxins,
such as alcohol, are filtered out of the blood - production of blood protein – albumin
maintains the tonicity of blood plasma - removal of red blood cells – old or damaged
RBC’s are filtered out and the haemoglobin
in them is converted into bile pigments
Why are liver and pancreas called accessory organs?
because they produce
digestive secretions but never touch the
food
How is bile involved in digestion of lipids
bile emulsifies fat by
breaking it into smaller droplets, stored in
the gall bladder until needed
Components of pancreatic juice
lipase – enzyme hydrolyses lipids into glycerol
and fatty acids
pancreatic amylase – enzyme hydrolyses starch
into maltose
trypsin – enzyme hydrolyses protein into shorter
polypeptides
nuclease – enzyme hydrolyses nucleic acids
(DNA and RNA) into nucleotides
sodium bicarbonate – base to neutralise the
acid from gastric juice, produces a pH around 8
Components of intestinal juice
maltase – enzyme hydrolyses maltose into
glucose
peptidase – enzyme hydrolyses short
polypeptides into amino acids
mucus – lubricates and protects the intestinal
wall
How is Small Intestine specialized for digestion and absorption?
- secretes intestinal juice to finish chemical
digestion
three regions of small intestine?
duodenum – most chemical digestion
occurs here, receives secretions of liver
and pancreas
jejunum – longest region, most
absorption occurs here
ileum – finishes absorption
What is a villus
lol
What are microvilli
- cells lining the villus are covered with many
tiny extensions
how are monosaccharides and amino acids absorbed into the body?
- these are actively transported into the cells
lining the villus - they then pass by facilitated diffusion into the
the tissue fluid, and from there diffuse into the
villus capillaries that lead to the hepatic portal
vein
what happens to fatty acids and glycerol?
these diffuse into the cells of the villus, where
they are converted back into lipids
these are packaged into vesicles and
released via exocytosis
vesicles pass into the lacteal and are carried
through the lymphatic system to the liver
Blood vessel that takes monosaccharide sugars and amino acids to the liver?
Hepatic Portal Vein
- carries blood from the small intestine
to the liver, where it is processed - portal vessels have the anatomy of a vein,
even though they do not connect to the heart
Large and small intestine size and length
Large - 1.5 m in length, but big diameter
Small - small in diameter, long in length
Function of colon
the ileum of the small intestine connects to
the colon, the main part of the large intestine.
- prepares food for elimination
Function of rectum
- large intestine ends in a short, expandable
region called the rectum - food that has passed through the entire
digestive tract, now called feces, is stored
here until it can be eliminated
Function of appendix
Narrow pouch assets in maintenance of gut bacteria
Order of organs and structures of digestive system
mouth-pharynx-esophagus-stomach-duodenum-ljejunum-ileum-colom-rectu-anus
Hormone that comes from pancreas and maintains blood sugar levels?
in addition to digestive secretions, the
pancreas also secretes the hormone insulin
insulin is released when blood glucose levels
are high, usually after eating
insulin stimulates muscle and liver cells to
store glucose as glycogen
this causes glucose levels to decrease, an
example of negative feedback
function of e/coli bacteria in colon?
- colon is home to populations of anaerobic
bacteria, bacteria that live without oxygen - the metabolism of these bacteria produces
beneficial molecules, such as vitamins K and
B7, as well as flatulence and the odour of
feces
Proteases (pepsin, trypsin)
Source = pepsin – stomach, trypsin - pancreas
Site of action = pepsin – stomach, trypsin –
small intestine
Optimum pH = pepsin – acidic (2), trypsin –
basic (8)
Function = protein + H2O → polypeptides
Salivary amylase
Source = salivary glands
Site of action = mouth
Optimum pH = neutral (7)
Function = starch + H2O → maltose
Lipase
Source = pancreas
Site of action = small intestine
Optimum pH = basic (8)
Function = lipids + H2O → glycerol + fatty acids
Nuclease
Source = pancreas
Site of action = small intestine
Optimum pH = basic (8)
Function = nucleic acids + H2O → nucleotides
Pancreatic amylase
Source = pancreas
Site of action = small intestine
Optimum pH = basic (8)
Function = starch + H2O → maltose
Peptidase
Source = small intestine
Site of action = small intestine
Optimum pH = basic (8)
Function = polypeptides + H2O → amino acids
Maltase
Source = small intestine
Site of action = small intestine
Optimum pH = basic (8)
Function = maltose + H2O → glucose + glucose
steps of digestions
physical digestion: chewing, mixing, moving
chemical digestion: breaking down food
molecules into absorbable units
secretion: fluids, enzymes, hormones, bile,
mucus
absorption: through tract wall into blood or
lymph vessels
elimination: undigested material expelled
pharynx
- common passageway for air and food
behind the mouth - contains the epiglottis, a muscular flap
involved in swallowing
esophagus
carries food to stomach
trachea
air passage to lungs
esophagus
- long muscular tube connecting pharynx to
stomach - lined by mucus secreting cells that lubricate
the walls and assist the passage of food
liver, pancreas placement
two other digestive organs are connected by
narrow ducts to the duodenum:
liver – above and beside the stomach
pancreas – between the stomach and the
intestine
