GI Theme 1 Flashcards
what are the main functions of the gut
digestion & absorption
excretion
defence
commuication
what are the 2 main groups of organs of the digestive system
alimentary canal- tract itself
accessory digetsive organs/glands
what are the layers of the GI tract
mucosa
submucosa
muscularis externa
serosa
what layers make up the mucosa
(Top to bottom)
- epithelium
- lamina propria
- muscularis mucosa
in which layer are most of the glands present
mucosal
only some in submucosal
what is gastrointestinal epithelium
tissue covering the external surfaces of teh body and lining hollow structures (except blood and lymphatic vessels which are lined by endothelial cells
where is epithelium derived from
embryonic endoderm (innermost of three layers formed at gastrulation)
what are the types of epithelia
stratified squamous epithelium
columnar epithelium
what are the features of stratified squamous epithelium & where is located
flat and scale-like
can be several cells thick
protective
located in oesophagus
what are the features of columnar epithelium
absorptive
single layer of cells
may have brush border
secretory (mucous & enzymes)
which epithelia is the major cell type in the gut epithelium and endocrine pancreas
columnar
what is the function of the oesophagus
conducts food by peristalsis
slow rhythmic squeezing
passageway for food only (respiration system branches of after the pharynx)
what are layers of the oesophagus
stratified squamous non- keratinised epithelium
submucosa
muscularised externa (does not contract unless stimulated)
mesothelium (simple squamous)
in the oesophagus where are most glands located and what is there function
submucosa
secrete mucous and serous to lubricate the lumen of the oesophagus
what is the function of the stomach
food enters at cardioesophageal sphincter storage tank for food site of food breakdown chemical breakdown of protein begins delivers chyme to SI
what are the layers of the stomach
gastric glands
gastric pits- contain secretory glands
what do the parietal cells of the gastric glands do
generation of HCL and KCL (gastric acid)
secretion of intrinsic factor
what are the other main cell types in gastric glands (apart from parietal cells)
mucous secreting cells
chief cells
enteroendocrine APUD cells
what is the function of the chief cells of the gastric glands
secrete pepsinogen which (breaks down polypeptides), renin, lipase
what do enteroendocrine APUD cells of the gastric glands secrete
polypeptide hormones
outline the differences between the cell types in the oesophagus and stomach
oesophagus epithelium is stratified squamous not simple columnar
no gastric glands is oesophagus mucosa
oesophagus has submucosal sermucous glands
stomach more muscular
where are the glands located in the stomach, how is this different from their location in the oesophagus
intermucosal layer
submucosa in oesophagus
what is the function of the small intestine
digestive organ
site of nutrient absorption into blood
muscular tube extending from pyloric sphincter to ileocecal valve
suspended from posterior abdominal wall by the mesentery
what are the 3 parts of the small intestine
duodenum
jejunum
ileum (connects SI to LI)
what are the layers of the duodenum
villi (no villi stomach)
crypts in mucosa- mucosal glands maintain lubrication
brunners glands- submucosal glands which neutralise HCL from stomacg(not in stomach)
myenteric plexus- gangli & nerves
what structure is a landmark of the small intestine
villi
where are most glands located in the small intestine
mucosal layer- lamina propira
what is the function of goblet cells
secrete mucous
- covers epithelial surfaces
- defence
where are goblet cells most abundant
colon
also in salivary glands
in which disease does goblet cell hyperplasia occur
cystic fibrosis
what are the paneth cells located
at the base of intestinal crypts
what is the function of paneth cells
like neutrophils secrete alpha defensins secrete lysozyme and phospholipase A2 may protect whole crypt long lived (20 days)
what is the function of the enterocytes of SI
digestion and absorption
columnar epithelial
what are the sections of the large intestine
caecum
appendix
colon- ascending, transverse, descending, sigmoid
rectum
function of LI
water, fat & salts absorption
faeces production
goblet cells produce mucous for lubricant
are there villi in the LI
no
what are the layers of the LI
mucosa- crypts submucosa muscularis mucosa muscularis externa- myenteric plexus serosa
what are the accessory digestive organs
teeth salivary glands pancreas liver gall bladder
what are accessory glands made up from
epithelial tissue connected through ducts
what are the classifications of accessory glands
uni cellular
multicellular
what are unicellular cells
give examples
individual cells within an epithelium
e.g. type II alveolar cells in the lungs
goblet cells
where are goblet cells found
intestinal epithelium
what are multicellular glands
tubular glands- lie along ducts
acinar glands- in sac at end of duct (simple & compound)
compound tubulo-acinar- submandibular glands
where are simple tubular glands found
intestinal & sweat glands
where are compound tubular glands found
gastric glands
what are sebaceous glands
simple acinar
branched acinar glands which generate an oily compound b merocrine secretion
where are compound acinar glands found
parotid & pancreas
serous content
where are tubulo-acinar glands found & how are they formed
submandibular
formed when simple layer of acinar cells fuse together
what secretions are from the parotid gland
serous- watery, leaky
where does the parotid duct (stensens duct) open
runs around masseter and opens into the oral cavity
which gland produces up to 70% of saliva
submandibular
what secretions are from the submandibular gland
Mixed:
mainly serous
also mucous
where does the submandibular duct (wharton’s duct) open
runs forwards above mylohyoid & opens into oral cavity beneath the tongue
what are the secretions from sublingual glands
mixed
mainly mucous
what glands does the lingual br of the facial innervate
sublingual and submandibular
where do the small ducts of the sublingual glands open
into oral cavity along sublingual fold
where are most minor salivary glands located
small aggregates in sub mucosa the oral cavity (not gingiva and hard palate
what do the minor salivary glands secrete
mixed secretions
mainly mucous
which glands in the oral cavity is only serous
von Ebner’s glands
what are myoepithelial cells
They sit on top of the acinar cells. Their contraction stimulates ejection of saliva.
what are the main structural features of minor salivary glands
acinar & myoepothelial
mucous tubular
intercalated ducts
striated ducts
what happens to saliva as it travels down the striated duct
ionic modification- saliva is isotonic but Na+ and Cl- are reabsorbed so the resultant saliva is become hypertonic
what is the main excretory duct
oral cavity
what do intercalated ducts do
connect acini with striated ducts which carry the content to excretory ducts then the main ducts
what are acini
groups of secretory cells that share a lumen (bunch of grapes)
what type of epithelium is found in excretory ducts
pseudostratified columnar
what type of epithelium is found in striated ducts
simple columnar
what type of epithelium is found in intercalated ducts
simple cuboidal
which duct has the largest diameter
excretory
what are the 2 types of secretory end pieces
serous acinus
mucous alveolus
what are landmarks for serous acinus
intercellular canaliculi
which secretory end piece has a larger lumen
mucous alveolus
which secretory end piece has a larger nucleus
serous acinus
what are serous demilunes
cellular formations in the shape of a half moon on some salivary glands
which glands are demilunes found on
mixed glands
mainly submandibular
what is the function of myothelial cells
support saliva secretion
maintain cell polarity & structural integrity of acinus
tumour suppressor activity
what is the function of saliva
helps form bolus
moisten, lubricate
initiate digestion of food
what is contained in saliva
proteins, glycoproteins, glycosaminoglycans, electrolytes and water
what is the main enzyme in saliva
amylase
what can be used for parotid saliva collection
lashley cannula
curby cup
what can be used for submandibular/sublingual saliva collection
schneyer’s apparatus
what are some systemic diseases causing saliva hypofucntion
sjogren syndrome graft-versus-host disease cystic fibrosis granulomatous diseases uncontrolled diabetes mellitus thyroid disorders hepatic disease neurological diseases HIV
what are other causes of salivary gland hypofunction
radiation
chemotherapy
depression
ageing
factors affecting saliva composition
flow rate - resting vs stimulated -cardiac rhythms relative contribution of glands diet individual variation
what is the function of myoepithelium
increases rate of saliva production
