Gastrointestinal system Flashcards
Rebecca
what is the primary function of the GI tract
absorption of dietary nutrients maximised by secretions added to convert large molecules to smaller ones
what are the other GI functions
storage and secretion
what is the mucosa made up of and where is it found
epithelium, lamina propria, muscularis mucosa
nearest the lumen, inside
what is lamina propria
CT , has nerves, blood and lymph vessels
what is the muscularis mucosa
thin layer of smooth muscle
what is the submucosa layer and where
thicker layer with similar composition to lamina propria (CT)
contains submucosal plexus
middle
what is the muscularis externa
circular muscle, myenteric plexus and longitudinal muscle
what does the ENS do
coordinates contractions to mix and move contents between compartments
what is the serosa layer
outmost layer of CT and squamous cells
some tract sections dont have this layer
what 3 divisions of the ANS regulate the Gi function
parasympthetic
sympathetic
enteric
what does the PNS do
signals stimulate GI secretions and motility facilitating digestion and absorption of nutrients
what does the SNS do
decreases GI secretions and motility
how does the ENS work
can operate independenly and is involved with reflexes and majority of GI functions
what are the main plexuses in the ENS
myenteric
submucosal
what does the myenteric plexus do
motility
regulates intestinal smooth muscle , contractions of muscles
what is motility
coordinated contraction and relaxtion of muscles in the Gi tract
what does the submucosal plexus do
secretions, regulates secretions and local absoptive environment
what do reflexes in the ENS do
If one thing is going onn in one place then it can influence whats happening in another part
how do they reflexes in the ENS communicate?
they are neural circuits with mechanoreceptors or chemoreceptors that then causes nerves to signal to regulate endocrine or secretory cells
what are some GI neurotransmitter examples
enkephalins (contrict circular muscle around sphincters), ACh, serotonin
what are some GI hormones (endocrine)
gastrin, cholecystokinnin, motilin, secretin
what are paracrines
hormones released that act locally
examples of paracrines
histamine, prostaglandins , somastostatin
what are the 3 digestive phases
cephalic phase, gastric phase and intestinal phase
what is the cephalic phase
triggered by thought of food , primarily neural, stimulates secretion
what is the gastric phase
begins when food and oral secretions enter the stomach, coincides with distension (expansion of stomach). hormonal, neural and paracrine
what is the intestinal phase
when stomach contents recah the duodenum
primarily hormonal but also other 2
what is the role of the upper GI tract
minimal role in nutrient absorptionm transports and prepares food to be absorbed
parts of the upper GI tract
mouth, salivary glands, oesophagus,stomach
what does the mouth do
reduces food to optimal size, mixes food with secretions from 3 salivary glands (submandibular, parotid, sublingual)
what is mastication
chewing
swallowing (oesophagus)
- intiated voluntarily, involuntary after
- parasympathetic
- from mouth to upper oesophageal sphincter
peristalsis in the oesophagus
series of coordinated muscle contraction/relaxtion
commences after upper oesopheageal sphincter
functions of the stomach
3 primary motility functions
mixing via slow wave-intiated contractions, retropulsion and gastric emptying
accept and store food
mix food with secretions
digest food
deleiver food to small intestine
stomach secretions
dervived from gastric invaginations (pits) which contain multiple cell types to secrete different secretions
how do salivary secretions get produced
controlled by sympathetic and parasympathetic
cl, na and water are transported to duct lumen
ductal cells modify by reabsorbing na and cl and secreting K and HCO3 -
examples of gastric secretions
ions and water, mucus from mucous neck cells, pepsinogen from cheif cells , H+ from parietal cells
what are the sections of the small intestine
duodenum
jejunum
illeum
what is the role of the small intestine
most macronutrient , vitamin and mineral absorption occurs (big SA)
what are the parts of the large intestine
caecum, ascending, transverse, descending and sigmoid colon
rectum
anus
role of large intestine
significant water and ion absoprtion
motility of contents :mixing and propulsion
waht does motility in the small intestine involve
mixing via segementation and propulsion via peristalsis
what does motility in the large intestine involve
segementation, peristalsis and mass movement and reflexes that control sphincter contraction and relxation
what does the ileocecal sphincter regulate
amount of chyme entering the large intestine
