L21 - gi system: structure & function Flashcards
what is the gastrointestinal system?
network of organs and specialised cells that allows food to be converted to energy and nutrients needed for life
what does the gi tract consist of?
- mouth
- oesophagus
- stomach
- small intestine
- large intestine
- rectum
- anus
what does the gi system consist of?
accessory organs - help function of gi system but not apart of it
- salivary organs
- liver
- gallbladder
- pancreas
mesentery
- membranes tissue in stomach
- surrounds organs in go tract
- holds intestines in place
- provides blood vessels & lymphatics
what does mouth in gi system consist of?
- teeth
- tongue
- mucous membranes
how does mouth play part in eating?
- main function is to chew
- food passed to pharynx and epiglottis
- prevents food travelling to lungs
bolus in oesophagus
- tube like structure
- involuntary movement of food bolus
- transports bolus to stomach
stomach
- mixing
- muscular organ
- protein digestion
- HCl, pepsin
- fat emulsion
3 parts of stomach wall
- mucosa = mucus layer (top)
- submucosa = glands and blood vessels
- muscularis = smooth muscle
cells present in stomach wall
- mucous neck cell
- parietal cell
- enterochromaffin like cell
- chief cells
- d cells
- g cells
mucous neck cells in stomach wall
produce mucus and bicarbonate
parietal cells in stomach wall
produces gastric acid and intrinsic factor
enterochromaffin like cells
involved in enteric nervous system
chief cells
produce enzymes (pepsin, gastric lipase)
d cells in stomach wall
produce peptide hormone somatostatin to inhibit acid
g cells
produce gastrin to stimulate acid
small intestine structure
- longest part of gi tract
- main sight of absorption
- 3 sections (duodenum, jejunum, illeum)
what does the SI do?
- site of breakdown of carbs, proteins, fats
- primary site of absorption
the villi in the SI
- increase SA
- allow for better absorption
crypts of lieberkuhn in SI (glands)
- paneth cells play role in defence and produce antimicrobial enzymes
- stem cells for regeneration
- goblet cells for mucus
what is the large intestine for?
- water and ion conservation
- bulk movement of faeces
- storage
- defaection
salivary glands
- lubrication via mucus
- protection
- digestion (amylase & lipase)
liver
- bile production
- excretion
gallbladders
- concentrating reservoir for bile (bile emulsifies fats)
- bile contains bilirubin (used to make hb)
- delivers bile to duodenum (SI) in response to meals
pancreas
- makes enzymes to digest proteins, fats, carbs
- makes hormones insulin + glucagon
6 functions of GI system
- ingestion
- secretion
- movement
- digestion
- absorption
- excretion
what is ingestion?
process of eating food / having a drink through mouth
what is secretion?
release of substances that contribute to digestion
movement in the gi system
- segmentation
- peristalsis
segmentation
contraction of circular muscles in gi tract (the one that’s really circular) (forwards backwards movement)
peristalsis
wave like movement. main way
what is digestion?
breakdown of food into smaller components that can be absorbed into the bloodstream
mechanical digestion
physically breaking food with mouth / stomach movements
- mastication
- peristalsis
- gastric acids
chemical digestion
enzymes breakdown food
- fats to fatty acids / monoglycerides
- nucleic acids to nucleotides
- polysaccharides / carbs to monosaccs
- proteins to a.a
- these enzymes are usually secreted by accessory organs
what is absorption?
process through which nutrients, water, electrolytes enter blood
what is excretion?
metabolic waste eliminated from body
immune function
- first line of defence against pathogens
- diverse microbiome contributes to immune regulation
- microbiome prevents overgrowth of bad bacteria
- cells secrete mucus and antimicrobial peptides
- gut resident immune cells
what is the sphincter?
muscular ring that prevents stomach juices from going back into the oesophagus
stomach acid
HCl, allows pepsin to work best & kills bacteria
chyme
thin watery material left behind when digestion is complete
