Organised disassembly and absorption Flashcards
function of the oesophagus
transit
function of the stomach
storage
grinding food - milling
acid/peptic digestion
function of the small intestine
carbohydrate, fat, protein digestion and absorption
water and electrolyte transport
bile salt transport
function of the large intestine
storage
water reabsorption
function of the rectum and anus
defecation
what are the four digestive processes
motility
secretion
digestion
absorption
what occurs in the motility process
physically pass food through tract
what occurs in the secretion process
secrete digestive juices into digestive tract
what occurs in the digestion process
what you secrete will take the larger macromolecules and convert them into smaller molecules
what occurs in the absorption process
absorb efficiently and rapidly
what is apprehension
teeth, lips and tongue move food into the mouth
lips retain food in mouth
what is mastication
rhythmic action to break food to smaller pieces = increases SA
what is salivation
moistens food to make it easier to swallow
what is deglutition
swallowing, series of muscles facilitate pushing food to back of mouth
when is the somatic motor act initiated
by willed decision to start chewing
becomes automatic
what is the purpose of chewing food
grinds and breaks up food
mixes with saliva
stimulates taste buds = release chemicals
what hormone is released as a result of chewing and what is the effect this causes
gastrointestinal hormones
initial neurological activation
tell rest of gut food coming
whole process is controlled neurologically and hormonally
what are the three glands where saliva is secreted
parotids
sublinguals
submaxillary
what is secreted at the parotid gland
thin watery fluid
what is secreted at the sublinguals gland
fluid of intermediate viscosity
what is secreted at the submaxillary gland
thick, mucus-rich fluid
how is the saliva formed
all the secretions join to form enzyme and mucus-rich solution
what are the constituents of saliva
water 99.5% (solvent)
ions (sodium, chloride, bicarbonate-buffer)
mucus (lubricant-solvent)
alpha-amylase (enzyme attach starch-digestion)
lysozymes (destroy bacteria-first point of protection, antibacterial action)
what are the functions of saliva
aids speech - facilitate tongue movement
oral hygiene - flush food residues
buffering - bicarbonate buffers neutralise acids
how many litres of saliva is secreted in a day
1-2
what controls saliva production
spontaneous
parasympathetic nerve endings
in response to a stimulus how much saliva can be produced
5ml per minute
which receptors respond to food in the mouth
chemoreceptors
pressure receptors
what happens at the salivary gland
- neurological stimulus received via parasympathetic nerves
- vasodilation of capillary = increase blood flow into capillary, more difficult for blood to flow continuously so increase pressure cause hyperfiltration of plasma
filtrate of plasma passes between cells and enters lumen (acinus) - amylase vesicles move an fuse to the apical membrane, release enzyme contents
same time bicarbonate is added from the acinar cells into fluid - NaCl ions removed from plasma in ductule so left with of watery fluid to pass down ductule
how many skeletal muscles are use in deglutition and what happens
25
propel bolus into oesophagus
what is the name of movement along the oesophagus
active peristalsis
what is receptive relaxation
stomach expands to accepts food
what is the function of the stomach
acts as a storage vessel
what happens to food in the stomach
ingested material in strongly acidic medium (pH 2) weakens food structure
digests protein with pepsin (optimum pH2)
what is the second wave of defence in boy
pH2 stomach acidic
how is chyme formed, what is chyme where does it go
in stomach during digestion
turns the material into thin, acidic, slurry
to be released into duodenum
what are the three layers of muscle in the stomach
oblique
circular
longitudinal
what is the function of the layers of muscle in the stomach
layers mean the bag can contract
what is the stomach lining like
mucosa is ridged - covered in ugae
further breaks the food
what is the gastic juice composed of
water HCl pepsinogen intrinsic factor mucous
what is the water for in the gastric juice
solvent
what is the HCl for in the gastric juice
chemical attack on food
antiseptic
what is the pepsinogen for in the gastric juice
pepsin secreted as pepsinogen (inactive precurser)
stomach acid activates pepsin
what is the intrinsic factor for in the gastric juice
essential for absorption of vitamin B12
what is the mucus for in the gastric juice
protects cells for further digestion
what cells make up the gastric gland
mucus
parietal
enteroendocrine
chief
what is the function of the mucus secreting cells in the gastric gland
protect underlying cells
what is the function of the parietal cells in the gastric gland
secrete acid and intrinsic factor (need for vitamin B12 absorption in small intestine) only fundus and body
what is the function of the enteroendocrine cells in the gastric gland
secrete hormones into blood
what is the function of the chief cells in the gastric gland
secrete protein pepsinogen
how does the capillary link to the gastric gland
capillary diameter changed so plasma ultrafiltered out
produce fluid to enter gastric pit, in fluid the pepsinogen, acid and intrinsic factor mix into plasma
when are the enteroendocrine cells activated
when food enter stomach and stimulates gastric juice production
what can diffuse through an inactive parietal cell
chloride ions
what happens to the parietal cell when they are activated
they extend apical surface to long cannaliculi
when does carbonic acid form in parietal cell and how
when parietal cell activate
water and carbon dioxide diffuse IN to the cell from the capillary to form carbonic acid
what aids the formation of carbonic acid
carbonic anhydrase
what decreases the amount of acid made after digestion
inhibitors
what happens to carbonic acid produced in parietal cell
carbonic acid separates = hydrogen protons + bicarbonate
proton pumps in apical membrane remove hydrogen protons into lumen of gastric pit using ATP
bicarbonate diffuses OUT of cell back into circulation
what causes basic level of gastric secretion
what mechanisms is working
sight smell oral stimuli signals pass down vagal nerves, causes acetylcholine released signals to gastric pit neurological mechanism
what causes full wave of gastric secretion
when food enters stomach, hormonal mechanism
which are the hormones involved in gastric secretion
what types of hormones are they
gastrin (endocrine hormone)
histamine (paracrine hormone)
where is gastrin released from and to
gastrin released from G-cells secreted into blood, (non-localised = endocrine) round body and picked up by gastric pits
where is histamine released from and to
released from H-cells (very localised = paracrine) to gastric gland
further amplify gastric juice secretion
what differs between neural and hormonal signals
neural - rapid but short lived
hormonal - slow but persistent
what pH is chyme
2
why cant chyme be absorbed
polysaccharide and protein broken into small chains (large SA:V for subsequent digestion), need to be monomers
what is secreted into the chyme
pepsin intrinsic factor (for later B12 absorption)
when does the stomach usually emptry
2-4hrs after meal
what regulates the rate of stomach emptying
inhibitory signals from small intestine:
- enterogastric reflex
- secretin
- cholecystokinin
what is the enterogastric reflex
reflex between stomach and intestines
when is secretin released
response to acid
when is cholecystokinin released
response to fat