Exam 1 - SI Flashcards
first two pages of Small/Large Intestine Mod 3A is on deck of Upper GI. try to move them here. this deck starts on page 3 of mod 3a.
first two pages of Small/Large Intestine Mod 3A is on deck of Upper GI. try to move them here. this deck starts on page 3 of mod 3a.
Where does the Jejunum and Ileum begin and end?
Begin at Ligament of Treitz and end at Ileocecal Valve
What is the function of Jejunum and Ileum?
Continued digestion and absorption. Secretion of brush border enzymes to help in digestion and absorption.
What assists with digestion and absorption in the Jejunum and Ileum?
Secretion of brush border enzymes to help in digestion and absorption.
What five things does the Jejunum have a major role in absorping?
Fat, carbs, protein, water, electrolytes
Which vitamin and other three things does the Ileum have a major role in absorping?
VitB12, bile salts, remaining digested nutrients, and water
What is the function unit of the Small Intestine?
Villi
What happens at the Villi?
Site of absorption and secretion in the SI
What do the Villi cover?
Musocal folds which physically slow passage of food
What is the role of the Mucosal Folds in the Jejunum and Ileum? What covers the folds?
Physically slows down passage of food in Jejunum and Ileum. Covered by Villi.
What two cells make up the Villi?
Goblet Cells and Absorptive Columnar Cells
What do the Goblet Cells in the Villi secrete?
Mucus
What happens at the Absorptive Columnar Cells of the Villi?
Site of actual absorption
What are located on each end of the Absorptive Columnar Cells of the Vili?
Microvili
What do Microvili form?
Forms brush border of mucosal surface
What forms the Brush Border of the mucosal surace?
Microvili
What is found along surface of brush border?
Thin layer of fluid
What is the function of the brush border’s thin layer of fluid?
Facilitates absorption of all substances except water/electrolytes
What “extends” into each layer?
Lamina Propria Layer
What are the names of the two arterioles contained in the Lamina Propria Layer, a part of the Villi?
Lacteal and Central Arteriole
What is the function of the Central Arteriole? What does it carry?
(Part of the Lamina Propria Layer of the Villi).
Capillary transport of substances directly to liver via hepatic portal vein. Carries carbs, proteins, and some fats (glycerol and FFA) to liver.
What is the function of the Lacteal Arteriole?
(Part of the Lamina Propria Layer of the Villi).
Transport fat molecules/substances to systemic circulation via Thoracic Duct
What is found at the base of the Villi?
Crypts of Lieburkuhn
What are three cells which made up the Crypts of Lieburkuhn?
Precursor Cells, Paneth Cells, Secretory Cells
What is the function of the Precursor Cells of the Crypts of Lieburkuhn?
Turn over intestinal cells over 4-7 days
What is the function of the Paneth Cells of the Crypts of Lieburkuhn?
Immune function, secretes antibiotic peptides
What is the function of the Secretory Cells of Crypts of Lieburkuhn?
Secrete brush border digestive enzymes
What is the average transit time for the Small Intestine?
1-3 hours, but wide range
Which hormones stimulate the Small Intestine?
Secretin, CCK, intestinal gastrin, motilin
What are the three motility patterns of the SI?
Segmentation, Peristalsis, MMC
When does Segmentation of the Small Intestine occur and what occurs? What is the function of Segmentation?
Frequent small contraction of circular muscle. Occurs during feeding. More frequent than peristalsis.
Function: Mixed chyme to contact brush border
When does Peristalsis of the Small Intestine occur and what occurs? What is the function of Peristalsis?
Function: Move chyme to LI.
Occurs during feeding, coordinated waves of longitudional muscle to allow for digestion and absorption.
When does MMC of the Small Intestine occur and what occurs? What is the function of MMC?
Function: House cleaning, sweeps out stomach/SI of chyme and bacteria.
Occurs during fasting. Motilin is a stimulus.
What are the three Intestinal Motility Reflexes?
Ileogastric Reflex, Ileointestinal Reflex, Gastroileal Reflex
What is the stimulus and action of the Ileogastric Reflex?
Stimulated by Ileum being distended.
Action to inhibit gastric motility, slowing down ileum to allow more chyme to enter and terminal ileum to empty into LI.
What is the stimulus and action of the Intestinointestinal Reflex?
Stimulated by section of SI becoming distended.
Action is to relax distal small intestine, allowing chyme to move to LI.
What is the stimulus and action of the Gastroileal Reflex?
Stimulus is increased stomach/gastric motility and secretion.
Action is to valve relaxation of terminal ileum to empty SI in order to receive more chyme from stomach.
What is the normal position of the Ileocecal Valve and what is its regulation?
Intrinsic regulation. Normally closed.
What is the stimulus and action to open the Ileocecal Valve?
Stimulus is approaching peristaltic wave from ileum.
Action is to relax Ileocecal Sphincter.
What is the stimulus and action to close the Ileocecal Valve?
Stimulus is distention of the cecum/LI.
Action is constriction of Ileocecal Valve.
Where are digestive enzymes and bile salts secreted?
Proximal Duodenum
Where are the majority of carbs, fats, and proteins digested? (2 places)
Distal Duodenum, Jejunum
Where is VitB12 absorbed? Only place.
Terminal Ileum
What two things do the Gastric Parietal Cells secrete?
Intrinsic Factor, HCl
What does VitB12 allow the proper formation of?
RBCs
What is the name of the dz of insufficient VitB12?
Pernicious Anemia
Where is VitB12 stored for years? 2 organs.
Liver and kidneys
Poorly formed RBCs due to insufficient VitB12 is called Pernicious Anemia and what else?
Macrocytic Anemia
Where are Bile Salts secreted into, what are they required for, and where are they recycled back into via?
Secreted into duodenum.
Required for fat digestion/absorption.
Recycled back to liver via re-absorption in terminal ileum.
Where are carbohydrates digested? (two places)
Mouth and Small Intestine
What enzyme in the mouth starts carb digestion?
Salivary Amylase. Breaks starches into small molecules (dextin and oligosaccharides).
Enzymes for digesting carbs in the Small Intestine from from which two organs/parts? Which enzymes and what they convert carbs into.
- Pancreas=Pancreatic Amylase. Convert olgiosaccharides into Lactose, Maltose, and Sucrose
- Brush Border=Emzymes Lactase, Maltase, Sucrase, breaks into Galactose, Glucose, Fructose
What are the three Brush Border enzymes and their products used in breaking down carbs? Where are they secreted from?
Secreted from Lactase, Maltase, Sucrase breaks into Galactose, Glucose, Fructose.
Secreted by secretory cells of base of Villi (Crypts of Lieburkuhn).
Where are the Brush Border enzymes in the Small Intestine secreted from?
Secreted by secretory cells of base of Villi (Crypts of Lieburkuhn)
What are the three final products of carbohydrate digestion in the Small Intestine?
Monosaccharides: Galactose, Glucose, Fructose. (Brokendown by Brush Border enzymes.)
Where are digested carbs absorbed and where are they transported to?
Absorbed by Brush Border of Villi capillaries. Transported directly to liver via hepatic portal vein.
(Monosaccharides: Galactose, Glucose, Fructose.)
Is insulin required for intestinal uptake of glucose?
NO!!!
What are the two sites of protein digestion?
- Stomach
2. Small Intestine - Primary site of protein digestion. Stomach isn’t necessary.
Is the stomach is necessary part of protein digestion? Which two parts of the SI are majorly involved in protein enzymes?
No. The Small Intestine can handle it entirely. Pancreatic enzymes, Brush Border enzymes.
What enzyme in the stomach begins protein digestion? What does it convert protein into?
Enzyme is Pepsin. Converts protein into small protein molecules (peptone, proteoses).
What cell secretes Pepsin into the stomach, in what form, and how is it activated?
Chief Cells secrete Pepsinogen which is converted to Pepsin by gastric acids (HCl).
Three Enzymes which breakdown proteins secreted by the ____ into the ____. Action?
Secreted by Pancreas into Duodenum.
Trypsin, Chymotripsin, Carboxpeptidase.
Breakdown proteins into smaller proteins (polypeptides, dipeptides) for Brush Border to digest and absorb.
Where are Brush Border enzymes are secreted from and their action?
Secreted from secretory cells at base of Villi (Crypts of Lieburkuhn).
Convert smaller peptides (polypeptides, dipeptides) into Amino Acids which can be absorbed by Villi.
Where are amino acids absorbed and transported to the ___ via which vein?
By Villi in SI. Transported to liver via hepatic portal vein.
What are the two locations that fat digestion occurs? Which is the major location?
Stomach and SI.
SI is major location of fat digestion.
What do fats require for digestion that proteins and carbs do not?
Bile Salts, which are emulsifying agents
What do Bile Salts do to fats? (Be specific.)
Emulsify fats. Surround fats and prevent reformation into large fat droplet by reducing surface tension that separates fat molecules.
What is the enzyme and action of stomach of fats?
Gastric Lipase. Initiates breakdown of fats.
What three things/steps does the SI do to fats?
- Emulsifies with bile acids to keep small fat droplets
- Lipolysis by pancreatic enzymes to break down fat droplets into monoglycerides and Fatty Acids
- Form micelles (monoglycerides or FAs linked with bile salts and phospholipids)
What and where is a micelle?
In SI, part of fat digestion. Absorbable form of fat.
Monoglycerides or FAs linked with bile salts and phospholipids which are water soluable.
What can a Micelle do and contact in the SI?
Can penetrate the aqueous brush border and contact surface of epithelial cell.
What parts of a micelle are absorbed into epithelial cells and which parts are not?
Absorbed: Fat contents (Long Chain Fatty Acids and Glycerol) are absorbed by epithelial cell.
Bile salts not absorbed by epithelial cell, but are absorbed by distal ileum.
What happens in the Epithelial Cell to Long Chain Fatty Acids and Glycerol molecules? What are they called?
Synthesized into triglycerides and phospholipids. Called chylomicrons.
Chylomicrons exit the epithelial cell via _____ and go to the ____ or ______ _______.
Exit via exocytosis. Go to heart of systemic circulation.
Glycerol and Short Chain Fatty Acids are absorbed directly into the…?
Capillary System
