Gut Mucosa Flashcards
What are the 6 Layers of the Gut?
epithelium
lamina propria
muscular mucosa
submucosa
muscular propria
adventitia
What 3 Types of Mucosa are there?
Protective Mucosa
Secretory Mucosa
Absorptive Mucosa
Describe Protective Mucosa
Protective
- characterised by stratified squamous epithelium
- found in oral cavity, pharynx, oesophagus and anal canal
= non keratinised
Describe Secretory Mucosa
secretory
- contain cells responsible for secretion of digestion enzymes and acid
- found in stomach
Describe Absorptive Mucosa
Absorptive
- absorb digested nutrients
- found in small intenstine
- water absorption and electrolyte balance
- found in large intestine
Describe the Oesophagus
- epithelial = unkeratinised stratified squamous
= protective mucosa
What is the Function of the Stomach?
digestion and churning food
What is the Cardiac Sphincter, where is it found?
prevents food coming back up, located between oesophagus and stomach
Structure of the Stomach
beginning: fundus
body
end: pylorus - meets the duodenum and meets the pyloric sphincter
What Mucosa is the Stomach? What are 2 other Features?
secretory epithelium - columnar epithelium
the mucosa folds around the lumen = reggae
contains gastric pits - 3/4 glands open into one pit
What do Glands Secrete in the Stomach?
secrete gel like glycoprotein mucous
function = form protective barrier against stomach acids and proteolytic enzymes
What 4 Cells Line Each Gland in the Stomach, and their Function?
Parietal Cells:
- secrete HCL (gastric acid) and intrinsic acid
function: binds Vitamin B12
- transport binding to liver
Enterochromaffin-like Cell:
- secrete histamine
function: stimulate acid secretion
Chief Cells:
- secrete pepsinogen - precursor for pepsin (breakdown protein)
- secrete gastic lipase
Endocrine Cells of GIT: enteroendocrines
- regulatory functions and secrete hormones
D cells: secrete somatostatin - inhibits acid formation
G cells: secrete gastin - stimulate acid secretion
What Mucosa is the Small Intestine?
Absorptive Epithelium
What is the Main Feature of the Small Intestine?
villi
- increase surface area
Structure of the Small InDesJIne
Duodenum
Jejenum
Ileum
- lumen gets wider and microvilli shorter
Where is the Duodenum and Describe one of the Glands.
in the small intestine
Brunner’s glands in the submucosa
What Features does the Ileum have?
in the small intestine
collections of lymphocytes = Payer’s Patches
Which 5 Cells are found in the Small Intestine?
Enterocytes - harbours brush border enzymes
Goblet Cells - secrete mucous
Paneth Cells - antimicrobial role, secrete defensives and lysozymes
Immune Cells
Enteroendrocrine cells - K cells
- secrete incretins - augment function of insulin and lower blood sugar levels
- secrete gastric inhibitory peptide
What Endocrine Cells are Found in the GIT?
- Stomach has two types of endocrine cells which secrete hormones.
- G cells – secrete gastric which stimulate HCL or other acid secretions
- D cells – stimulate somatastin which inhibits gastric juices and inhibits acid secretions
- Small intestine
- K cells – secrete incretins which augment function of insulin, help lower blood sugar levels. Also secrete gastric inhibitory peptide which inhibits secretion of gastric acids.
- Large intestine
- L cells – secrete peptides such as glucagon like peptides 1 and 2. Help increase satiating and aid in weight loss. Act like glucagon and lower sugar levels. Weight loss meds contain something similar to GLP-1 secreted by L cells to improve body weight. Suppress apatite.
What is the Structure of the Large Intestine/Colon?
Cecum
Ascending Colon
Transverse Colon
Descending Colon
Sigmoid Colon
3 Functions of the Large Intestine
reabsorb water
dehydrate food waste
compact to form faeces
What are the Features of the Large Intestine
- Crypts of Lieberkuhn
= no villi but epithelium invaginate into lamina propria
Large no. of Goblet Cells
- protect surface from material
Describe the Livers Features?
formed of hepatic lobules
- hepatocytes and a central vein
at each corner = portal triad
= portal vein, hepatic artery and a bile duct
Describe the Two Types of Glands Found in the Pancreas.
Type 1:
exocrine serous acini
- secrete digestive enzymes through bile duct to small intestine
Type 2:
endocrine: alpha and beta cells
- alpha = secrete glucagon
What Condition can you have in the Oesophagus?
Barrett’s Oesophagus (GORD/GERD)
- due to laxation of gastro-oesophageal sphincter
- causes: hyper-acidity from obesity or bulimia
- what happens?
- stratified squamous cells change into columnar secretive format
Why may you Get Ulcers in the GIT?
gastric acids and peptide enzymes damage epithelium coverage
What Protection is there against Ulcers in the GIT?
innate protective mechanisms
mechanical:
mucosal blankets, blood vessels
chemical:
- secrete mucous and bicarbonate of a higher pH
- prostaglandins - inflam cytokines = inhibit secretion of acid
regenerative factors:
- stem cells replace damaged cells
What Effect does H.Pylori have on the Stomach, how do you reduce it?
more prone to ulceration
- use non-steroidal anti-inflam drugs
= aspirin, ibuprofen
- counteract the effect of prostaglandins
= enhance hyperacidity
- stimulates regurgitation of food and gastric acids into the stomach
Explain the Steps of How Peptic Ulcers cause Severe Bleeding.
- Injury or damage to epithelial cells
- expose connective tissue in lamina propria or further down
- fibrous tissue and granulation tissue forms
- scarring
IF IT KEEPS HAPPENING
- further and further into tissue
- reaches capillary
- microleakge of blood = anaemia
- bigger blood vessel = haematemesis or vomiting of blood and severe bleeding = death
How can Peptic Ulcers lead to Pernicious Anaemia?
if there is a loss of parietal cells
= no secretion of intrinsic factors
= no absorption of B12
How can Peptic Ulcers lead to Cancer?
if it is long standing
prone to cancerous transformation
Describe Malabsorption Syndrome
prevents absorption of nutrients from diet in the small intestine and results in diarrhoea, malnutrition, weight loss and anaemia
What are possible causes of Malabsorption Syndrome?
trauma
response to eating gluten
autoimmune
genetics
AIDS
change in microbiota - chemo, irresponsible antibiotics
Crohn’s
Intestinal Lymphangiectasia (Waldman’s Disease)
- rare disease after carcinoma, over dilation of lymph vessels
What is GSE?
Gluten sensitive enteropathy
What Happens in GSE?
- damage to mucosa in small intestine
- loss of villi
- malabsorption
- inflammatory cells within lamina propria and submucsoa
- inflam cells lead to tissue damage
- lose microvilli completely
- malabsorption of B12
