digestive system Flashcards
layers of GI tract
oesophagus to anal canal
1) serosa/adventitia
2) muscularis
3) submucosa
4) mucosa
the oral cavity’s accessory organs
teeth
tongue
salivary glands
salivary glands’s pairs
1) parotid
2) submandibular
3) sublingual
function of salivary glands
produces saliva –>
digestion
lubrication
protection of oral cavity
parotid
one of the pairs of the salivary glands
- largest, right in front the ears
- makes a watery saliva
–> containing salivary amylase (breaks down starchy stuff)
submandibular
one of the pairs of the salivary glands
-located under the jaw, under the lower teeth
—> produces a serous (watery) saliva and mucous saliva
–> makes up most of the saliva
sublingual glands
one of the pairs of the salivary glands
the smallest one
- found directly under the jaw, under the tongue
–> produces mucous saliva
lubricate the oral cavity and faciliates the swallowing
pharynx struc and func
struc : skeletal muscle
func : moves bolus to oesphogaus
oesophagus struc and func
struc : muscular tube
func : bolus to stomach
–> upper = sketeal
middle = mixed
lower = smooth
anatomy of the stomach
J shaped chamber,
4 main regions, cardia, fundus, body, pylorus
Rugae
Muscular vales (sphincter)
function of the stomach
holding reservoir
Mixing chamber = turns bolus into chyme
secretion of gastrin
secretion of gastric juice (HCl)
rugae
when stomach is empty, the rugae are folds that can stretch to increase volume of stomach
When the stomach is full, the rugae are flattened out - increase SA
(also acts a protective barrier from the underlying tissue to prevent harming the stomach)
Cardia
contains a cardiac sphincter to regulate the entry of food in the stomach
–> prevents food, stomach acid and digestive enzymes to go back up the oesophagus
Fundus
collects digestive gases, stores the food and releases it back slowly
–> Stores the food to regulate the rate of digestion and prevents the small intestine from having to digest a lot of food at a time
Body
releases pepsinogen and HCl, gastric juices == forms chyme
Pelsinogen is the inactive form of pepsin and is present in gastric juice: reacts with HCl to convert to pepsin
It’s made inactive and activated only in digestion so it doesn’t harm the cells that produce it
Pylorus
contains the pyloric sphincter and regulates the exit of chyme, connects to small intestine
mechanism of gastrin
gastrin(hormone) is released, binds to receptors on the parietal cells on the stomach
Triggers a series of signalling events involving enzumes and messengers on the stomach
stimulates H+/K+ ATPase which causes H+ to leave the cells, and be pumped into the stomach lumen, and H+ combines with Cl- to form HCL = gastric acid
small intestine anatomy
duodenum, jejunum and ileum
joins with the large intestine at the ileocecal sphincter
lined with villi + microvilli
small intestine function
receives pancreatic juice (via pancreatic duct) and bile (via common bile duct)
secretes intestinal juice
major site of digestion and absorption
lumen of small intestine
covered with villi with microvilli to increase SA of absorption back into the blood
duodenum
connects after the phylorus and recieves the digestive enzymes from the pancreas and bile from the liver = common bile duct
–> bile aid in the digestion/absorption of fats
Jejunum
complete digestion and absoprtion of nutrients, vitamins, BIG 3 (carbs, fats, proteins)
= broken down into smaller pieces, absorbed into blood stream through the jejunum wall
Ileum
complete absorption of nutrients, especially vitamin B12 and bile salts PLUS transport undigested materials and waste product from small –> large intestine for excretion
intestinal juice
lowers pH of the acidic chyme!
large intestine structure
caecum, colon, rectum and anal canal (anus)
internal (involuntary)/external anal sphincter (voluntary)
colon 4 regions
ascending, transverse, descending, sigmoid
large intestine function
absorption (water + electrolytes)
formation of faeces/excretion
some nutrients formed oooooo
nutrients in the gut
bacteria can ferment and breakdown undigested food to produce nutrients that can be absorbed by the body
