Gastrointestinal Flashcards
location of mechanical digestion
stomach; mainly in the antrum
location of chemical digestion
mainly small intestine
mechanical digestion
the physical breakdown of food material
chemical digestion
digestion involving enzymes that work at the surface of the food particles to break food down into into simplest elements
motility
the movement and manipulation of food using smooth muscle along the GI tract
function of receptors in walls of GI tract
stretch receptors - respond to the stretch that occurs in the lumen when food enters it
receptors in the lumen - notice chemical changes to contents of the lumen
effectors of the GI tract
smooth muscles cause contractions for motility and glands secrete substances; caused by reflexes
function of CNS in GI tract
can send neural signal across a long distance; activates the parasympathetic and sympathetic systems; modulates activity of ENS
function of parasympathetic system in GI system
stimulates motility and secretion
function of sympathetic system in GI system
inhibits motility and secretion
enteric nervous system
ENS; involved in peristalsis and segmentation; main regulator of GI system
submucosal plexus of ENS
regulates secretion
myenteric plexus of ENS
regulates motility
paracrine hormones
localised hormones that have a function in the GI tract itself
functions of motility
movement at a controlled rate, mechanical digestion, mixing, exposing absorptive surfaces
motility patterns
patterns of movement that can be recorded easily and usually stick to a similar pattern
fasting
period of time when we are not eating; continues for 4 hours after a meal; housekeeping of the intestines to clean it out when not eating
feeding
period of time when food is entering the GI tract; propulsion happens in the intestines, stomach, esophagus, retropulsion in the stomach and segmentation in the intestines; food stored in stomach and colon
during feeding, where does propulsion occur?
esophagus, stomach, intestines
retropulsion
mixing motility pattern that occurs in the stomach during feeding
peristalsis
the movement of food through the GI tract via smooth muscle contractions behind the food particle
segmentation
motility pattern where smooth muscle contractions cause different substances are mixed up to increase surface area and make absorption more efficient in the intestines
functions of chewing
reduces size of food, allows for taste
where in the stomach is food generally stored?
in the fundus and the body
smooth muscle that regulates delivery of food from the antrum of the stomach to duodenum
pyloric sphincter
stomach relaxation is controlled by the nervous system through the what system?
parasympathetic and vagus nerve
propulsion
contractions that happen to push food down GI tract
is there more intense contraction activity in the stomach within 60 minutes of a meal, or after that time?
the more intense activity in the stomach is 60-300 minutes after a meal
gastric emptying
the emptying of the contents of the stomach into the duodenum; regulated by pyloric sphincter
kinds of cells in the duodenum that detect if foods are too fatty and what this leads to?
endocrine cells; leads to the reduction of activity in the stomach, the intragastinal reflex activated in the ENS, reduces parasympathetic input to decrease stomach motility
small intestine function
to mix the secretions and food from all places, and to carry the food for absorbtion
large intestine function
to store poo; no segmentation; some absorption from recovering fluids and salts; moves about twice a day to initiate defecation
fluid in plasma each day
3L
amount of fluid we secrete each day
8L
three salivary glands
parotid, submandibular and sublingual glands
components of saliva
mucus, diluting solution, digestive enzymes: lipase and a-amylase
function of a-amylase
break down of starch
function of mucus
protection, lubrication and aids in mechanical digestion
xerostomia
a dry mouth from reduced or absent saliva leading to black teeth
gastric secretion includes
mucus, HCl (parietal cells) and pepsinogen –> pepsin (chief cells)
intrinsic factor in stomach function
break down of vitamin B and absorption
gastric acid functions
dilutes food, denatures proteins, low pH, protection
parietal cells
secrete acid into stomach lumen to aid chief cells.
cephalic phase
premeditating eating; via para sympathetic nervous system when stimulates the release of parietal cells and chief cells
oesophageal hiatus
hole in the diaphragm that the oesophagus passes through to reach the stomach
lower esophageal sphincter (LES)
the sphincter at the top of the stomach that prevents reflux from the stomach back up into the esophagus
parts of the stomach
cardia, fundus, body and pylorus
lesser omentum
connects the stomach to the liver
greater omentum
hangs like an apron connecting the stomach to the transverse colon and protects the peritoneum with adipose tissue
pyloric sphincter (PS)
sphincter in the pylorus of the stomach that regulates the passing of chyme into the duodenum of the SI and prevents reflux
fibres in the muscularis layer of the stomach and location in the stomach
longitudinal, circular and oblique; allows for many contractions for mechanical digestion; located in the body of the stomach
rugae in the stomach
temporary folds that flatten out when the stomach is full and fold when it is empty; have a submucosa core and mucosa layer containing gastric glands
gastric glands
glands in the stomach; goblet cells at the top producing mucus, G cells, parietal cells and chief cells in lower levels
G cells
produce gastrin and other endocrine hormones like ghrelin
chief cells
produce digestive enzymes in the stomach including pepsinogen which eventually breaks down proteins (pepsin)
parietal cells
in the stomach, produce acid for chemical digestion in the stomach
ghrelin
‘hunger hormone’ released by G cells
location of pancreas
posterior to stomach, next to SI, retroperitoneal
hepatopancreatic ampulla
junction where bile duct from liver joins with the pancreatic duct to flow into the duodenum
hepatopancreatic sphincter
the sphincter regulating the release of things from the pancreatic duct into the duodenum
acinar cells
secrete digestive enzymes and hydrochloric acid into the pancreas lumen
duct cells
secrete bicarbonate in the lumen of the pancreas
structure of acinar cells is similar to _____ cells in the stomach and ______ cells in the mouth
chief; salivary
epithelium in mouth/oral cavity and function
simple squamous; protection from abrasion
epithelium in the stomach, small intestine, and large intestine
simple columnar; secretion and absorption
epithelium in the anal canal
stratified squamous for protection
example of an unicellular gland
goblet cells
locations in GI tract for simple multicellular glands
stomach and small intestine
locations in GI tract for compound multicellular glands
salivary glands
four layers of the GI tract
mucosa, submucosa, muscularis, adventitia
components of the mucosa
epithelium, lamina propia (FCT) and muscularis mucosae
components of the submucosa
glands, blood vessels and nerves to regulate secretions (ENS system)
components of the muscularlis layer
inner circular smooth muscle fibres and outer longitudinal fibres and the myenteric plexus that lies in between muscle layers and regulates motility
myenteric plexus
in between the muscle layers in the muscularis layer, part of the ENS system and regulates motility
components of the adventitia
helps maintain structure of the tube and adheres the tube to surrounding structures; FCT
mesentery
a double layer of visceral peritoneum that connects the organ to the body wall
omenta
double layer of visceral peritoneum that connects an organ to another organ
fauces
holes at the back of the mouth where food passes through
epiglottis
ensures the food enters the oesophagus, not the trachea
features of esophagus
highly folded submucosa and mucosa; has skeletal muscle
villi
folds of the mucosa that increase SA, found in the SI and sits on plicae circulares
pilae circulares
folds in the submucosa
microvilli
sit on top of villi to increase the SA even more and make a brush border; covered with glycocalyx
glycocalyx
glycoproteins at the end of the microvilli brush border and allows for contact digestion
stem cells
make cells in the SI
paneth cells
secrete antibacterial lysosomes to prevent bacteria from colonising our guts
parts of the large intestine
cecum, colon and rectum
parts of the colon
ascending, transverse, descending and sigmoid
ileocecal valve
between the small and large intestine and regulates the passage of substances through to the cecum
appendix
extension out of the large intestine, the cecum; holds
teniae coli
bands of longitudinal smooth muscle that line the colon
haustra
series of pouches in the wall of the colon that helps move the fecal matter
omental appendices
sacs of fat around the colon
teniae coli
bands of longitudinal smooth muscle that surround the large intestine for defection
glands in the large intestine
intestinal glands
liver location
superior right quadrant of abdominopelvic cavity
main function of liver
to produce bile
blood supply to liver
from hepatic artery and is processed by hepatocytes which produce bile
hepatocytes
produce bile in the liver, arranged into lobules
portal triad
made up of the hepatic artery, hepatic portal vein and the bile duct
