GI Secretion, Digestion & Absorption Flashcards
What are the main gastric secretions and their daily volume?
Acids, enzymes, hormones, and intrinsic factors; ~2L per day.
What are the key functions of gastric acid?
Activates pepsin, denatures proteins, kills bacteria, inactivates salivary amylase
What is the role of pepsin in digestion?
It is an enzyme that breaks down proteins into smaller peptides.
What is the function of somatostatin in the stomach?
It inhibits gastric acid secretion
Why is gastric acid important for protein digestion?
It denatures proteins, making them more accessible for enzymatic digestion.
How do NSAIDs and alcohol affect the gastric mucosa?
They destroy mucosal barriers, leading to gastric irritation and ulcers
What is the function of the proton pump in gastric acid secretion?
The H⁺/K⁺ ATPase pump secretes hydrogen ions, making the stomach acidic.
How does omeprazole work?
It irreversibly inhibits the H⁺/K⁺ ATPase proton pump, reducing gastric acid secretion
What are histamine H2 receptor antagonists?
Drugs that block histamine-stimulated gastric acid secretion, e.g., cimetidine and ranitidine.
Why was ranitidine discontinued in the UK?
Due to adverse drug reactions (ADRs)
What is Helicobacter pylori and its effect on the stomach?
A bacterium that causes gastric mucosal inflammation, leading to ulcers.
How is Helicobacter pylori treated?
With antibiotics to eliminate infection
What is the role of intrinsic factor in digestion?
It binds to vitamin B12, facilitating its absorption in the small intestine.
Why is vitamin B12 important?
It plays a crucial role in DNA synthesis and red blood cell (RBC) production.
What are intestinal secretions composed of?
Mucus, digestive enzymes, and hormones
What is the function of mucus in the duodenum?
Protects the duodenum from gastric acids and digestive juices.
Which enzymes digest carbohydrates in the intestine?
Sucrase, lactase, maltase, and amylase.
How are digested carbohydrates absorbed?
Through glucose transporters (SGLT, GLUTs)
What is the role of cholecystokinin (CCK)?
Stimulates gallbladder contraction, pancreatic enzyme secretion, and inhibits gastric emptying.
What does secretin do in digestion?
Stimulates bicarbonate secretion and inhibits gastric emptying.
What is the function of gastric inhibitory peptide (GIP)?
Inhibits gastric emptying and acid secretion.
How does glucagon-like peptide-1 (GLP-1) affect digestion?
It inhibits gastric emptying and promotes satiety.
What is bile and where is it produced?
A non-enzymatic digestive fluid produced by hepatocytes in the liver.
What are the components of bile?
Bile acids, bilirubin, cholesterol, and bile salts
How do bile salts aid digestion?
They emulsify fats, making them easier to digest and absorb
What enzyme digests fats?
Pancreatic lipase
How are fats absorbed in the intestine?
Monoglycerides (MGLs) break down into free fatty acids (FFA) and cholesterol, which diffuse into enterocytes
What happens to absorbed fats and cholesterol?
They form chylomicrons and are removed through the lymphatic system
What are the two types of pancreatic secretions?
Enzymatic (proenzymes from acinar cells) and bicarbonate (from duct cells).
What is the role of bicarbonate in pancreatic secretions?
Neutralizes acidic chyme from the stomach and activates digestive enzymes.
Which pancreatic enzyme digests fats?
Pancreatic lipase.
Which pancreatic enzymes digest proteins?
Trypsin, chymotrypsin, and other proteases.
Which pancreatic enzymes digest nucleic acids?
Nucleases.
What is the function of the acinar cells in the pancreas?
They secrete inactive proenzymes (chymotrypsinogen, procarboxypeptidase, procolipase, etc.).
What is the function of the duct cells in the pancreas?
They secrete bicarbonate to neutralize stomach acid.
How does pancreatic lipase work?
It breaks down triglycerides into monoglycerides and free fatty acids.
What is the primary function of the liver in digestion?
Produces bile, which helps in fat digestion
What is the role of chylomicrons in fat absorption?
They transport absorbed fats and cholesterol through the lymphatic system.
Which organ produces digestive enzymes for all macronutrients?
The pancreas
Which organ is responsible for the majority of nutrient absorption?
The small intestine.
How is the digestive function summarized?
The stomach digests proteins, the pancreas secretes enzymes, the liver produces bile, and the intestine absorbs nutrients.
