GI 4A - Gastrointestinal System Flashcards
How long and where is the duodenum?
10-12 inches, first part of the small intestines
Where does the duodenum begin, travel, and end?
It begins at the pyloric valve, arcs around the head of the pancreas and passes to the left, and ends at a sharp bend called the duodenojejunal flexure (Junction)
How long is the jejunum?
8 Feet long and extends from the duodenum to the ileum
How long is the ileum and where does it join with the large intestines?
12 feet long and joins the large intestine at the ileocecal valve
Maximal surface area is accomplished through_____, ______, and _______.
Plicae circulares, villi, and microvilli
Enterocytes have microvilli, a bunch of make a villus, and a bunch of villus makes a plicae circulares.
What characteristics do surface absorptive cells possess?
possess a layer of closely packed microvilli, enzymes (brush boarded ie enterokinase), and transporters
What characteristics do goblet cells possess?
mucous producers
What characteristics do enteroendocrine cells possess?
Secrete CCK, secretin, GIP (DNES and APUD cells)
What characteristics do regenerative cells possess?
Divide to replace themselves and the other types of epithelial cells
What characteristics do paneth cells possess?
secrete the antibacterial enzyme lysozyme and other antibacterial agents
What are the most common examples of polysaccharides?
Glycogen, starch, cellulose
What does pancreatic amylase do in the duodenum?
degrades polysaccharides into disaccharides and “oligosaccharides”
What is the family of enzymes that break down the disaccharides? And what are their specific names?
Disarrharidases Maltase for maltose Sucrase for sucrose Lactase for lactose a-dextrinase for a-dextrins but only does a little break downthe rest is crapped out
Glucose + fructose =
Sucrose
lactose = _____ + _______
galactose and glucose
glucose + glucose =
Maltose
How are Glucose and Galactose absorbed into the enterocyte?
via secondary active transport through a Na+ dependent cotransporter known as SGLT1. High luminal concentration of Na facilitates absorption of these sugars against their gradients.
How is fructose absorbed into the enterocyte?
Facilitated diffusion via glucose transporter 5 (GLUT 5)
*doesn’t require Na+
How are all monosaccharides transported out of enterocyte into capillaries?
GLUT 2 (facilitated diffusion)
Whats the deal with Lactose intolerance?
No lactase to break down lactose = stink butt
Where are the majority of amino acids cleaved off?
occurs mainly at the brush border with aminopeptidases and with active pancreatic enzymes
What are the aminopeptidases?
Amino-oligopeptidase and dipeptidyl - aminopeptidase
and little ceaz one-peptidase
What are the active pancreatic enzymes?
Typsin, chymotripsin, carboxypeptidases A/B, elastase
How are amino acids transported?
Most aa or small peptides are transported via the same co-transport mechanism utilized by glucose. Some aa do not require Na co-transport instead they are transported in the same way fructose is moved, facilitated diffusion.
