Gut mucosa in health and disease Flashcards
what are the functions of the git
ingestion and digestion of food
absorption of nutrients
elimination of waste products
seceretion (saliva, hormones, enzymes, mucous)
what does the upper git consist of
oral cavity
oesophagus
stomach
what does the lower git consist of
small intestine
large intestine
list the general structure of the git
epithelium
lamina propria
muscularis mucosa
submucosa
muscularis propria
adventitia/serosa
what is the epithelium supported by
lamina propria which is loose connective tissue
what is the muscularis mucosa made up of
smooth muscle
what is the sub mucosa made up of
loose connective tissue that has blood, lymph and nerva supply to the git
what 2 types of muscle is the musuclaris propria made up of
external longitudinal muscle layer
internal circular muscle layer
what is the adventitia
connective tissue that seperates the gut and peritoneal membrane
what is the adventitia called when it is covered by a single layer of epithelium
what is this single layer called and made up of
serosa
mesothelium-simple squamous epithelial layer
what are the main 3 types of mucosa in the git
protective
secretory
absorptive
what is protective mucosa charcterised by
where is it found
stratified squamous epithelium
oral cavity, pharnyx, oesophagus and anal canal
what is the difference between the stratified squmaous epithelium found in the oesphagus, pharnyx and anal canal compared to that found in some places of oral cavity
first is non-keratinised and oral cavity is keratinised (in some places)
the cells in the secretory mucosa are responsible for what
where is secretory mucosa found
secretion of digestive enzymes and acids
stomach
what is absorptive mucosa responsible for in the small intestine
absorbing digested nutrients
what is absorptive mucosa responsible for in the large intestine
water absorption and electrolyte balance
why is the epithelial coverage of the oesophagus non-keratinised stratified squamous
has to act as mechanical protective barrier from rough food bolus
what are the 2 types of tissue in the musucularis propria
inner circular
outer longitudinal
list general structure of oesophagus
muscosa
submucosa
muscularis externae
esophageal glands proper
why do some parts of the muscularis externae in the oesophagus contain skeletal muscle
to help swallowing of the food bolus
what is the distinguishing feature of the stomach compared to the git
glandular structure in stomach musoca
what is the role of the cardiac sphincter
closes to prevent food coming back up
junctions in the stomach can change from what type of epithelial coverage to what other type
stratified squamous to secretory (which is simple columnar)
what are rugae
folds of mucosa of the stomach around the lumen
what is the stomach entirely made of
glands
how many gastric glands are there in the stomach
15 mill
what are the opening of gastric glands in to the lumen called
gastric pits
how many gastric pits in stomach
3.5 mill
therefore every 3/4 glands share one opening
list general structure of stomach
mucosa
submucosa
muscularis
serosa
what is the role of gastric pits
allows transports of secretion from glands to lumen
what are gastric pits lined with
columnar epithelium
what is 4 parts is the gastric gland made up of
pit, neck, body and base
where are mucous neck cells in the gland
neck
what do mucous neck cells secrete
mucus
bicarbonate
what is the purpose of the mucus that is secreted by the mucous neck cells
form a mucosal blanket (gel-like layer) on surface of epithelial cells as a protective barrier against stomach acid and proteolytic enzymes
what does mucus secreted contain
glycoproteins called mucins
what do parietal cells secrete
gastric acid (hcl)
intrinsic factor (Ca++ absorption)
what is the role of the intrinsic factor secreted by the parietal cells
binds vitamin b12 (important for blood cell formation or fast-growing cells like bone)
what do enterochromaffin-like cells secrete
what is the purpose of this secretion
histamine
stimulates secretion of stomach acid
what do the cheif cells secrete
pepsin(ogen)
gastric lipase
what is the role of gastric lipase
helps digestion of lipids in stomach
what is pepsinogen
a precursor of pepsin
what is pepsin
proteolytic enzyme that breaks down the proteins in food
when is pepsinogen converted to pepsin
when stomach secretes acid and pH drops
what do D cells secrete
what is the role of the secretion
somatostatin
inhibits stomach acid formation
what do G cells secrete
what is the role of secretion
gastrin
stimulates acid production
D and G cells are what type of cells
endocrine cells (secrete hormones not enzymes)
what are goblet cells
mucus secreting cells
what is the distinguishing feature of the small intenstine
macroscopic folding of the mucosa in to villi and microvilli
what is at the bottom of each villi
crypts (valleys of the villi) that invaginate into the lamina propria
the absorptive epithelium is made of columnar cells, what are these columnar cells called
enterocytes
what is the role of the mucosal folding (villi)
increase sa to increase the rate of nutrient absorption
what are the 3 parts of the small inestine
duodenum
jejunum
ileum
what changes happen as you move down the small intestine
lumen widens
microvilli get shorter
what is a special histological feature of the duodenum
brunner’s glands/mucosal glands
what is a special histological feature of the ileum
Payer’s patches
(collections and follicles of lymphocytes)
mucosal glands and payers patchers are found where in the small intestine
submucosa
what is the role of paneth cells in the small intestine
what do they secrete
anti-microbial (kill bacteri and prevent infection in small intestine)
defensin (self defense peptides)
lysozymes
what are the main cells that form the epithelium of the mucosa of the SI called
enterocytes
what is the brush border
border of enterocytes
folding in cell membrane which projects in to the lumen
what does the brush border harbour and why
enzymes
to aid with the digestion of disaccharides into monosaccharides
what type of cells are lymphocytes and plasma cells
where are they present
immune cells
in submucosa of SI
what are k cells called
where are they found
enteroendocrine cells
SI
what are the 4 types of endocrine cells in the git
G
D
K
L
Where are G and D cells found
stomach
what do k cells secrete and why
incretins (hormones that change function of insulin)- helps lower blood sugar levels and help in glucose homeostasis
gastric inhibitory peptide- inhibits secretion of gastric acids
what type of cell is an L cell
wher are they found
enteroendocrine cell
large intestine
what do L cells secrete
why
glucagon-like peptides (number 1 and 2)
help increase satiety, aid in weight loss and act like glucagon therefore lowering blood sugar levels in body (have a function in glucose homeostais)
what is the distinctive feature of the large intestine
crypts but no villi
what are crypts
invaginations in to the lamina propria
what are crypts made up of
columnar cells with goblet cells
why is there a large number of goblet cells in the large intestine
for lots of mucosal secretion, to protect surface epithelium from dehydrated food/material
what does the colon end with
appendix (small tubular structure)
why is the lumen smaller in the appendix
bc its full of lymphoid follicles/lymphatic tissue
what is the liver formed of
lobules
what are lobules formed of
hepatocytes and a central vein
what is there in each corner of a lobule
portal triad
what is the portal triad made up of
bile duct
hepatic portal vein
hepatic artery proper
what 2 types of glands is the pancreas made up of
exocrine serous acini
endocrine (formed of alpha and beta cells)
what is the role of the exocrine srous acini in the pancreas
secrete digestive enzymes through the bile duct to the small intestine
what is the role of the alpha cells in the endocrine part of the pancreas
form and secrete glucagon
what is the role of the beta cells in the endocrine part of the pancreas
form and secrete insulin
what is the role of insulin
helps cells take up glucose from the blood therefore lowering blood glucose levels
what is the role of glucagon
inhibits the insulin effect and allows the glucose to be released from glycogen in the liver, into the blood
what is the endocrine organ called
Islets of langerhans
what is the difference between metaplasia and dysplasia
metaplasia- change of one form of cells to another
dysplasia-presence of abnormal cells within tissue/organ
what is the normal epithelium type of the oesophagus
non-keratinised stratified squamous epithelium
what is Barrett’s oesophagus
GORD leading to metaplasia
Pathogenesis that can happen in oesophagus due to laxation of gastroesophageal sphincter
what is barrett’s oesophagus caused by
obesity, bulimia, use of non-steroidal anti-inflammatory
what does continual reflux lead to
metaplasia from the stratified squmaous protective type into columnar secretory type
what does barrett’s oesophagus type epithelium contain lots of and why
goblet cells
to wall of acidity by secreting mucus and bicarbonate
what can barrett’s oesophagus lead to
cancer
what is an ulcer
loss of surface epithelium exposing the connective tissue in lamina propria underneath (but can go as deep as submucosa)
what are damaging factors of the upper git
name 2 types in normal git
factors that erode epithelial coverage
gastric acidity
peptic/proteolytic enzymes
what are the 3 protective factors in the stomach against damaging factors
mechanical barriers
regenerative barriers
chemical barriers
name 2 types of mechanical barriers in the stomach
epithelial coverage
mucosal blanket
what is a regenerative barrier in the stomach
stem cells that divide and differentiate into new cells that replace any damaged cells from the epithelial surface
name 2 chemical barriers in the stomach
secretion of mucus and bicarbonate (lower the pH)
prostaglandis (inflammatory cytokines secreted in response to hyperacidity in stomach, also inhibits secretion of acids to protect mucosal lining)
name other factors which can cause injury of the stomach
- increasing gastric acidity
- H. pylori infection (makes stomach prone to ulceration)
- use of non-steoridal anti-inflammatory drugs (e.g aspirin and ibuprofen)- they counteract effect to prostaglandis and will stimulate acid secretion
- duodenal gastric reflux
- tobacco and alcohol (stimulates acid secretion leading to gastric hyperacidity)
what does the submucosa in the stomach form in response to ulcers
fibrous and granulous tisse to wall off damage (will lead to scarring)
what happens if an ulcer reaches a capillary
issue with this?
can lead to microleakage of blood and minimal internal bleeding
cant be detected and so can lead to anaemia
what happens if an ulcer perforates a bigger blood vessel
hematemesis (vomiting of blood)
severe bleeding
cancer (if multiple or bigger ulcers)
death
why can an ulcer cause pernicious anaemia
because of loss of parietal cells
leads to loss of intrinsic factors
leads to malabsorption/ no absorption of vitamin b12
what is malabsorption syndrome
failure to absorb nutrinets from the diet due to a disease of small intestine resulting in a combo of diarrhoea, steatorrhoea, malnutrition, weight loss and anaemia
what are the 2 causes of malabsorption syndrome
maldigestion- partial or total gastrectomy leading to lack of mechanical mixing or insufficiency of digestive mediators
mural/mucosal causes- loss or damage of mucosa of small intestine
what is steatorrhoea
fatty diarrhoea
what causes mucosal causes leading to malabsorption syndrome
trauma
surgery
what is gluten sensitive enterothapy/coeliac disease
exaggerated immune response to eating gluten
what is autoimmune enteropathy
autoimmune reaction to body cells themselves (i.e. intestinal enterocytes)
what is intestinal lymphangiectasia
overdilation of lympathtic vessels
what is crohns disease
wide spread ulceration of git
where does ulcerative colitis occur
small and large intestines
what is acrodermatitis enteropathica
genetic disease causing blunting of villi
what does immune deficiency HIV/AIDS-related enteropathy lead to
why isnt it easily treated
loss of epithelium due to high infection rate
due to low immunity
what are microbial causes
what are they caused by
disturbance or chnages in microbiota
immune supression, irresponsible use of antibiotics, chemotherapy, trauma to intestine and parisitic/bacterial infection
what is mural disease
scleroderma
why does coeliac disease lead to malabsorption
due to loss of structure of mucosa of small intestine in form of losing villi structure
what is marsh 1
marsh 2
marsh 3
preliminary stage
moderate progression of disease
late stage of disease
describe marsh 1
villi still present but lots of inflammatory cells in lamina propria and submucosa
describe marsh 2
flattening of villi and increase in inflammatory cells leading to tissue damage (inflmmation and inflammatory cytokines secreted lead to tissue damage)
describe marsh 3
microvilli structure lost entirely and huge invasion of inflammatory cells in tissues
what vitamins arent taken up due to malabsorption
vitamin b
vitamin k
vitamin c
what can lack of vitamin b lead to
anaemia
loss of hair
oral ulcers
