Lecture 2 Block 2 Flashcards
(25 cards)
Name the 5 hollow organs of the GI tract for this block?
Mouth Esophagus Stomach Small Intestine Large Intestine
Name the 3 accessory organs of the GI tract for this block?
Salivary glands
Liver
Pancreas
What does the mouth and esophagus do for digestion and absorption of food purposes?
Mechanical disruption (size, surface area, consistency)
What do the salivary glands (and lingual) do for digestion and absorption of food purposes?
Initiate digestion of carbohydrates (alpha-amylase) and fats (lingual lipase)
Lubrication: via mucus (protein) and serous (watery) secretions
What does the stomach do for digestion and absorption of food purposes?
Continues mechanical disruption
Beings protein digestion (via secretion of ~2L/day of gastric juice rich in acid and pepsinogen/pepsin)
What do the small intestines do for digestion and absorption of food purposes?
Absorbs and secrete salt and water; the NET result is absorption of 9-10L/day
Finish digestion of proteins, carbohydrates, and lipids:
- pancreatic enzymes
- hepatic bile
- luminal disaccharidases and peptidases for final digestion
What does the liver do for digestion and absorption of food purposes?
Secretion of bile (emulsifies fat; stored in gall bladder, releasing ~0.5L/day into duodenum)
What does the pancreas do for digestion and absorption of food purposes?
Secretion of pancreatic juice (~1.5L/day, rich in HCO3- and enzymes
What does the large intestine do for digestion and absorption of food purposes?
Final absorption of salt and water (about 0.4-0.5L/day)
Modest role in regulation of K+ homeostasis
Compacting and storage of stool before expulsion
What is the Endocrine pancreas (overview)?
Endocrine glands secrete their products, hormones, directly into the blood rather than through a duct. It is the source of insulin and glucagon secreted directly into the blood
What is the Exocrine pancreas (overview)?
Exocrine glands secrete their products (including digestive enzymes, and some hormone chemical messengers) into ducts that lead directly to the external environment. Exocrine pancreas is a collection of lobules; each lobule is a collection of ducts which begins at an acinus.
What is the bicarbonate (HCO3-) in the pancreatic juice for?
Neutralizing the acid in gastric juice which facilitates that action of pancreatic enzymes
What is a general role of pancreatic enzymes?
Completing the intraluminal (within the tube of the small intestine) digestion of ingested carbohydrates, proteins, and fat.
What is the Acinus of an exocrine gland?
Is the site of formation of the primary secretion of the gland. It involves active secretion of salt and water and (in some cases) some specific secretory products - like digestive enzymes
What is the duct of an exocrine gland primarily for?
A site for “modification” of the primary secretory product of the acinar cells
What are some typical fluid volumes of the exocrine pancreas secretions?
1.2-1.5L/day of isotonic pancreatic juice (water and salts including sodium bicarbonate NaHCO3)
15-100 grams of protein (20 distinct enzymes)
What are zymogens and why are they secreted in this form?
Are a type of proenzyme - an inactive form of an enzyme. The pancreas secretes several digestive enzymes principally as zymogens to prevent them from digesting proteins in the cells in which they are synthesized.
What are the principal pancreatic enzymes secreted as inactive zymogens?
Trypsinogen (when activated is trypsin)
Chymotrypsinogen (when activate is chymotrypsin)
Procarboxypeptidase (when activated is carboxypeptidase)
Prolestase (when activated is elastase)
What are the principal pancreatic enzymes secreted as active enzymes?
Pancreatic alpha-amylase
Pancreatic lipase
Ribonuclease/deoxyribonuclease
How are zymogens activated?
Enteropeptidase (also called enterokinase) is an enzyme in the brush border of the small intestines that cleaves a peptide from trypsinogen, thereby forming the active digestive enzyme, trypsin. Trypsin then activates the other pancreatic zymogens
Which zymogen is activated first and then activates the other zymogens?
Trypsinogen has a peptide cleaved from it by enteropeptidase to form trypsin which then activates the other zymogens
What is the general structure of an exocrine gland?
A blind ended epithelial tube that secretes to the external environment
What digests:
- Carbohydrates
- Proteins
- Lipids
- Nucleaic Acids
Amylases digest carbohydrates
Proteases digest proteins
Lipases digest lipids
Nucleases digest nucleaic acids
(Clicker question) The acinus of an exocrine gland is a site for?
Active secretion of salt and water
