Digestive system 2 Flashcards
3 parts of the pancreas
head, body and tail
pancreas - 2 major ducts that secrete into the small intestine
the pancreatic duct (duct of Wirsung)
the accessory duct (duct of Santorini)
composition of pancreatic juice?
Pancreatic juice is a clear, colourless liquid that contains water, some salts, sodium bicarbonate and several enzymes.
1.2–1.5L of pancreatic juice are produced every day
what converts the stomach acid contents to a slightly alkaline pH (7.1–8.2), halting stomach pepsin activity and promoting activity of pancreatic enzymes?
the bicarbonate in pancreatic juice
enzymes found in pancreatic juice?
Pancreatic amylase — digests starch
Pancreatic lipase — digests triglycerides
Proteases — digests proteins
- Trypsinogen — activated by enterokinase (a brush border enzyme)
- Chymotrypsinogen — activated by trypsin
- Procarboxypeptidase — activated by trypsin
- Proelastase — activated by trypsin
- Trypsin inhibitor — combines with any trypsin produced inside the pancreas
Ribonuclease and deoxyribonuclease — digests RNA and DNA
what hormones secreted by the small intestine regulate pancreatic secretions?
Secretin
-Stimulates secretion of pancreatic juice that is rich in bicarbonate ions, promotes normal growth and maintenance of pancreas, enhances effects of CCK.
Glucose-dependent insulinotropic peptide (GIP)
-Stimulates pancreatic beta cells to release insulin.
Cholecystokinin (CCK)
-Stimulates secretion of pancreatic juice rich in digestive enzymes, promotes normal growth and maintenance of pancreas, enhances effects of secretin
Key components of the liver
Right and left lobes Falciform ligament Quadrate lobe Caudate lobe Ligamentum teres (round ligament) Right and left coronary ligaments
3 parts of the gallbladder
fundus, body and neck
describe the differences in the hepatic artery and the hepatic portal vein?
The hepatic artery supplies oxygenated blood from the branch of the aorta, and the hepatic portal vein provides nutrient rich blood from the stomach, spleen and intestines. All blood eventually leaves the liver via the hepatic vein.
decribe the blood flow to and from the liver, starting at the liver and finishing in the heart
Oxygenated blood from the hepatic artery OR nutrient-rich blood from the hepatic portal vein
Liver sinusoids
Central vein
Hepatic vein
Inferior vena cava
Right atrium of the heart
where are CCK and secretin made?
in the small intestine
components of bile
Water, cholesterol and several ions
A phospholipid called lecithin
Bile salts (Na and K salts of bile acids are a digestive product. These play a role in emulsification, the breakdown of large lipid globules into a suspension of small lipid globules. They also aid in the absorption of lipids following their digestion.)
Bile pigments (bilirubin from haemoglobin: excretory product)
composition and function of bile
Bile is a yellow, brownish, or olive-green liquid secreted by hepatocytes at a rate of 800–1000 ml day. The pH of bile is 7.6-8.6.
Bile is transported by a duct system to the gallbladder for concentration and temporary storage. The excretory product contains components of worn-out red blood cells. This is digestive secretion.
sequence of bile production
right and left hepatic ducts common hepatic duct from liver cystic duct from GB (some may be stored here) common bile duct pancreatic duct from pancreas duodenum
regulation of bile secretion
Parasympathetic impulses and vagus nerves
Cholecystokin (CCK): causes the gallbladder to contract and release stored bile
Secretin: causes the liver to increase its output of bile
3 mechanisms through which carbohydrate metabolism maintains normal blood glucose levels
Glycogenolysis — breaks down glycogen to glucose and releases the glucose into the bloodstream.
Gluconeogenesis — converts certain amino acids, triglycerides and lactic acid to glucose.
Glycogenesis — converts glucose to glycogen and triglycerides for storage.
lipid metabolism
Storage — hepatocytes store some triglycerides.
Lipolysis — breaks down fatty acids to generate ATP.
Lipogenesis — synthesises lipoproteins, which transport fatty acids, triglycerides, and cholesterol to and from body cells.
Cholesterol synthesis.
Synthesises bile salts from cholesterol.
which organ stores and activates vitamin D?
the liver
functions of the small intestine
Mix chyme with digestive juices and bring food into contact with mucosa for absorption
Completes digestion of carbohydrates, proteins, and lipids; begins and completes digestion of nucleic acids.
Absorbs about 90% of nutrients and water that pass through digestive system.
3 anatomical subdivisions of the small intestine
Duodenum
Jejunum
Ileum
The duodenum is retroperitoneal and the shortest of the regions. It starts at the pyloric sphincter of the stomach and is in the form of a c-shaped tube that extends about 25cm until it merges with the jejunum. Duodenum means “12” and this region got its name from being about as long as the width of 12 fingers.
The jejunum is about 1m long and extends to the ileum. Jejunum means “empty,” which is how it is found at death.
The ileum is the final and longest region of the small intestine at about 2m. It joins the large intestine at a smooth muscle sphincter called the ileocecal sphincter (valve).
brush border enzymes (microvilli of small intestine)..?
Carbohydrate digesting enzymes — ɑ-dextrinase, maltase, sucrase, and lactase.
Protein-digesting enzymes — peptidases (aminopeptidase and dipeptidase).
Nucleotide-digesting enzymes — nucleosidases and phosphatases.
They provide:
Digestion at brush-border.
Digestion in the lumen of the small intestine.
what is segmentation (in small int)?
localised mixing contractions that occur in portions of the intestine distended by a large volume of chyme. Thi brings food particles in contact with the mucosa for absorption.
what is migrating motility complex (MMC)?
the type of peristalsis that occurs in the small intestine when distension of the small intestinal wall lessens. This propels chyme forward along short stretches of intestine at a time.
what are enteric reflexes?
Enteric reflexes are reflexes that respond to the presence of chyme and work to increase intestinal motility (sympathetic impulses, on the other hand, decrease motility). There are two types of enteric reflexes — vasoactive intestinal polypeptide and segmentation.
VIP (vasoactive intestinal polypeptide) stimulates the production of intestinal juice.
Segmentation depends on distention which sends impulses to the enteric plexus and CNS.
distention produces more vigorous peristalsis.
10 cm per second.
