Gastrointestinal system Flashcards
where does the GI system begin and end
begins in the mouth, continues through the thoratic cavity and ends in the anus
what does the upper GI include
mouth, oesophagus, stomach and duodenum
what does the lower GI system include
small intestine, large intestines, rectum and anus
meaning of digestion
it is the chemical and mechanical breakdown of food
what are the three phases of digestion
cephalic phase
gastric phase
intestinal phase
what is the cephalic phase
starts with the external stimulus of food response from cerebral cortex, it leads to:
- increased saliva production and salivary amylase, lysozymes.
what is the gastric phase
deglutition reflex (swallowing) moves food to the stomach in order for the phase to occur.
- the release of hydochloric acid and pepsin for mechanic digestion (churning)
- starts in the stomach, fills in the stomach which causes the stomach receptors recognising this and increases the production of gastric acid for the breakdown
what is the intestinal phase
takes place in the small intestine.
- it feeds forward to promote digestion and absorption of nutrients
what is ingestion
food being taken into the mouth
what is secretion
the release, by cells within the GI tract of water, acid, buffers and enzymes
what is chemical digestion
series of catabolic reactions that break large carbohydrates, lipids, and protein food molecules into smaller molecules which can be used by body cells
which cells produce hydrochloric acid
parietal cells
what does the villi do in the small intestine
increase the surface area in the small intestines which increases the surface area for absorption
what are the three parts of the small intestine (in order)
- Duodenum
- Jejunum
- Heum
what happens in the large intestines during the food passage
excess water is absorbed, they also manufacture and absorb certain vitamins such as vitamin K which is needed for clotting
- a mixture of waste material, mucus and bacteria are then passed on to the rectum
what happens in the mouth during the food passage
the teeth chew the food (mechanical digestion) also while swallowing saliva which contains an enzyme called amylase
what is the scientific word for the food being broken down and being turned into a ball
bolus
what happens in the stomach during the food passage
it is churned into a thick liquid called chyme. HCL is excreted by the parietal cells which lowers the pH levels in the stomach which increases the effectiveness of pepsin (an enzyme that is used to digest proteins)
what happens in the small intestine during the food passage
bile is produced by the liver and is stored in the gallbladder which begins to breakdown of fat.
what does lipase break down into
fat molecules to fatty acids and glycerol
what does amylase break down into
maltose
what does the rectum do during the food passage
stores the waste material prior to excretion
