Digestion 2- Pancreas and beyond Flashcards
How many islets of lagerhans are there and what organ are they located in?
1-2 million cells dispersed in the exocrine pancreas.
3 types of cells that make up the islets of langerhans
- Alpha cells secrete glucagon
- Beta cells secrete insulin
- Delta cells secrete somatostatin (fewest, inhibitory, located between alpha and beta cells)
What type of junctions do the islets of langerhans have?
Gap junctions activated by calcium transfer.
Tight junctions and desmosomes (cell to cell contact)
Glucagon is derived from
Preprohormone
Glucagon stimulates the release of
Stimulates hepatic (liver) release of glucose by glycogenolutic or gluconeogenic actions during fasting, exercise, or neonatal.
Glucagon targets what?
Targets the liver and adipose cells to release glucose. Glucagon interacts with liver and adipose cells through a G protein coupled receptor. The secondary messenger is PKA.
What stimulates glucagon to be released from alpha cells?
Amino acids, acetyl choline, epi, NE, VIP from the gut and CCK from the gut.
What inhibits glucagon to be released from the alpha cells?
Glucose, insulin, somatostatin (inhibitory), ketones, Free fatty acids, glucose lipid 1 and glucose inhibition protein.
Insulin peptide looks like what
A chain with 21 amino acids linked to B chain with 30 amino acids. Linked by disulfide bond.
How is insulin synthesized?
As pro-insulin
Insulin receptor has how many domains?
2 alpha domains that bind to insulin and 2 beta domains that has tyrosine kinase domains. Once bound, phosphorylation occurs and it can internalize the insulin that is bound.
What activates insulin release from beta cells?
Glucose, amino acids, ketones, Free fatty acids, glucagon, acetylcholine.
Growth hormone and cortisol.
What activates insulin release from beta cells?
Somatostatin, epinephrine, and NE.
How are insulin and glucagon release related?
They are oppositely related. What activates glucagon release, inhibits insulin release.
Normal blood glucose levels
80-100 mg/DL
How does glucose, glucagon, and insulin levels change throughout the day?
Glucose- Increases when you eat, then returns to normal. Fluctuates throughout the day.
Glucagon- Pretty stable throughout the day. Not much change.
Insulin- Bounces around WRT glucose levels. As glucose levels increase, so do insulin levels.
What are insulin levels like at night?
Stable. Low. Same with glucose levels.
What does the A1C measure? What is a normal level?
How good the patient is at stabilizing their blood glucose levels.
Normal level is 7.
Somatostatin is increased by __ and decreased by ___
increased by NE and decreased with Ach
What is the function of somatostatin?
Regulates growth hormone, increases in the blood after a fat or protein rich meal. Allows for what is currently in the intestine to be reabsorbed.
Decreases acid secretion in the stomach.
Decreases intestinal motility.
Slows rate of absorption.
Why is pancreatic cancer so hard to diagnose?
Variety of symptoms since it plays so many roles in the body.
Once nutrients are absorbed in the small intestine, where do they go?
In the small intestine, they are absorbed into the villus, and eventually the central lacteal within the villus. The lymphatic vessel meets the thoracic duct, which dumps into the left subclavian vein.
What is a villus? What does it contain and where is it located?
Absorb nutrients in the small intestine. Contains a vein, artery, capillary, and central lacteal (lymphatics, fat transfer)
If there are a lot of fatty acids in the small intestine, CCK is secreted. What does it do?
If CCK is secreted by the small intestine, then it will increase in the plasma as well.
This causes the gall bladder to contract to release bile into the common bile duct.
Also relaxes the sphincter of oddi, which allows bile to flow into the duodenum
hemoglobin is broken down into
Bilirubin
What helps break down bilirubin?
Bacteria
Before bilirubin can be released from the body as feces or urine, it most be converted into?
Urobilinogen.
Pancreatic lipase converts triglyceride into
2 Monoglyceride and a free fatty acid.
What do you need in order to break down primary bile salts into secondary bile salts? (need secondary in order to properly break down fats)
Bacteria!
4 cells of the intestinal glands from superficial to deep
Superficial
1. Absorptive cell- Digests and absorbs nutrients.
2. Goblet cell- Secretes mucous
3. Enteroendocrine cell- Secretes secretin and CCk. They are concentrated at the sphincter of oddi.
4. Paneth cell. Secretes lysozyme and is capable of phagocytosis. Deep in crypts.
Deep
** Also have stem cells.
Newer cells are deep, they mature and die as they move superficially.
Glycocalyx of the intestine contains
Mucin, enzymes, and transport carriers.
How do amino acids travel from lumen to inside intestinal cell and then to interstitial fluid(blood)?
Lumen–> Cell by syntransport with Na+. (a form of secondary active transport)
Cell –> intestinal fluid by amino acid transporters.
Glucose polymers such as __ and __ are broken down by ___ into which 3 disaccharides?
Glucose polymers such as starch and glycogen are broken down by amylase into:
maltose (glucose + glucose)
sucrose (glucose + fructose)
lactose (glucose + galactose)
How do carbohydrates travel from lumen to inside intestinal cell and then to interstitial fluid(blood)?
Lumen –> cell
Fructose travels by a glucose transporter. Glucose and galactose use symport (a form of secondary active transport) with Na+
Cell –> Intestinal fluid (blood) by GLUT. Glucose transporter by facilitated diffusion.
Ileum is in what quadrant of the abdomen?
The lower right quadrant. It is the terminal part of the small intestine. Attaches to the cecum of the large intestine.
The appendix. What is it attached to?
Located in the lower right quadrant, attached to the cecum.
Vestigeal organ.
If ruptures, will release harmful bacteria into abdominal cavity.
Histology of large intestine
Do not see villus (micivili on cells) because only SOME water absorption occurs here. Not nearly as much absorption as the small intestine.
Instead, it has many pores in the mucosa made of simple columnar epithelium that absorb water/goblet cells that secret mucus. Lots of lymphatic nodules.
9 liters of fluid dumped into the GI tract each day. How does it get reabsorbed/released?
Small intestine reabsorbs 8 liters.
Large intestine absorbs 90% of the 1 remaining liter.
What reflex moves feces into the rectum?
Gastrocolic reflex. Neuronal reflex. Stretch receptors signal sacral spinal cord
Control of the internal and external anal sphincter?
Internal- parasympathetic nerves control. Smooth muscle.
External- Sympathetic. Skeletal muscle control. Voluntary.
