GI Part 2 Flashcards
Liver
Contributes ____ _____ to digestion
Important for _____ digestion and absorption
Two types of cells make up liver (2)
bile salts
fat
Hepatocytes
Kupffer Cells
Bile Composition
1) Aqeuous _____ fluid
2) Organic compounds - bile ____, ch_____, l____, bi_____
Play a major role in aiding fat digestion through Fat ______
Secreted into the ______
1) Aqueous Alkaline fluid
2) Bile salts, cholesterol, lecithin, bilirubin
Emulsification
duodenum
Action of Bile
=
Amphipathic Structure =
When bile salt interacts with fat they create lipid emulsion droplets through the process of intestinal mixing, large droplets of fat get broken up into smaller droplets (large bc they accumulate together when in an aqueous solution and try to exclude water bc its hydrophobic like salad dressing)
One end is lipohilic (lipid soluble) and one end is water soluble
Emulsification Through Bile Salts
Taking large droplets of fat and creating small droplets prevents any ______ bc once the bile salts surround the individual droplets and bury their _______ ends into the oil and point their _____ soluble ends to the solution
- Important effects: gives ____ enzyme better ______ to fat by increasing surface area
- Having very little bile doesn’t mean you can’t break down fat, but it _____ the amount of fat you can digest
recombining, hydrophibic ends in oil, water solube ends towards solution
- Lipase, access
- limits
Bile Formation and Transport
Bile is produced by the ______
Bile salts are converted from _____ and added aqueous solution leaves through the liver through the (1)
-
(1) sphincter between bile duct and duodenum
- When we are not actively digesting fat, sphincter is tightly _____ -> so bile that’s produced by the liver tends to back up into the (1) and is ____ there
Liver
cholesterol, Common bile duct
-
Sphincter of Oddi
- closed, gallbladder, stored
Hormones Secreted When we Eat Fat
(2)
CCK
Secretin
Actions of CCK and Secretin
CCK (3)
Secretin (1)
- Stimulates liver to produce bile
- Relaxes and opens up sphincter of Oddi
- Contracts the gallbladder
- Stimulates liver to produce bile
Positive Feedback Loop of Bile
__% of bile is reabsorbed at the terminal portions of the ____ ____ and goes back to the liver
- When bile salts come back to liver -> very strong signal for liver to? -> more bile enters duodenum -> more gets reabsorbed, etc
- What shuts off this loop?
50%, small intestine
- strong signal for liver to make even more bile
- When fat digestion is complete, CCK and Secretin no longer released, sphincter of Oddi constricts, gallbladder relaxes and bile no longer enters duodenum and gets reabsorbed, and any bile produced by liver in the interim gets stored in the gallbladder
Micelle
______ core
______ shell
Surrounds free fatty acids and monoglycerides
-
Bile Salt
- Water soluble _____ points towards _____
- Lipid soluble _____ points towards _____
-
Lecithin
- Water soluble _____ points towards ______
- Lipid soluble _____ points towards ______
Hydrophobic core
Hydrophillic shell
-
Bile Salt
- Tail towards outside
- Head towards center
-
Lecithin
- Head towards outside
- Tail towards center
Small Intestine Segments
(3)
Small intestine is where all _____ and _____ of food is going to be completed
Majority of w_____, e_____, and m_____ asborption happens in the small intestine
Small intestine uses (1) as both mixing and propulsion movements
Duodenum
Jejunum
Ileum
digestion, absorption
water, electrolytes, minerals
segmentation contractions
Motility in the Small Intestine
Small Intestine uses ________ as both mixing and propulsion movements
In addition to mixing, segmentation enhances ___ that food comes in contact with intestinal wall to enhance ______
Segmentation
SA, absorption
Segmentation
Smooth muscle contraction depends upon stimulation from ______ cells
Intensity of contraction depends on:
- degree of _______
- presence of ______
- _____ ____ activity (ie ____ input)
How does it propel food? Ans: ______ of segmentation ______ down the length of the Small Intestine
pacesetter
- distension
- gastrin
- extrinsic nerve (vagal)
Frequency declines down length of intestine (creates slow movement forward)
Digestion and Absorption
____anatomy - Adaptations for digesetive and absorptive functions
Membrane-bound ______
_____ ______ membrane contains three categories of membrane bound digestive enzymes
- (1)
- (1)
- (1)
Microanatomy
enzymes
Brush Border
- Enterokinases
- Disaccharidases
- Aminopeptidases
Membrane Bound Digestive Enzymes (Notes)
Aminopeptidase = ______ enzyme
Enterokinase = ______ enzyme -converts _____ into _____
Disaccharidases = breaks down disaccharides into ______ (3)
Proteolytic
Proteolytic, trypsinogen -> trypsin
monosaccharides (maltose, sucrose, lactose)
Membrane Adapted for Absorption
(1) Folds of mucosa that enhances the absorptive surface area
(1) Each individual cell along the vili has these on their apical surface which is termed the (1)
Villi and Microvilli increases _____ _____ available for digestion by ____ times
Note: Anything that compromises our absorptive surface area can greatly affect n____ and hy____
Villus
Microvilli - Brush Border Membrane
surface area 600x
nutrition and hydration
Interior Structure of Vili
Highly adapted to take up food, water, electrolytes, etc
- Capillaries =
- Central Lacteal =
- Where amino acids and monosaccharides are first absorbed
- Lymphatic vessel where fat that has been absorbed by small intestine initially enters then drains into veins that feed into liver
Brush Border Enzymes
Disaccharidases (3)
Disaccharides they digest (3)
Broken down into which monosaccharides (3)
Maltase -> Maltose -> 2 Glucose
Sucrase -> Sucrose -> Glucose and Fructose
Lactase -> Lactose -> Glucose and Galactose
Brush Border Enzymes
(1) The prominent brush border enzyme that’s going to break down (1) fragments into individual (1) that are then absorbed
Which then activates _____, _____, and _____ (from last lecture)
Aminopeptidase -> Polypeptide Fragments -> Amino Acids
Trypsin, Chymotrypsin, Carboxypeptidase
Fat digestion
Introduction of bile salts and pancreatic lipase in Duodenum
- Production of Lipid _____ - combination of triglycerides and bile salts
- Pancreatic Lipase breaks down triglycerides to from the (1) which represents what?*
- Micelles cross the brush border enzyme and once it does, monoglycerides and fatty acids reform triglycerides bc for it to eventually enter bloodstream has to be packaged into a thing called a (1) (LDL, HDL) in this case first one that is formed is the (1) lipoprotein that enters the (1) and make its way to the circulation
- Lipid Emulsification
- MICELLES REPRESENT THE ABSORBABLE FORM OF DIGESTIVE FAT
- Lipoprotein, Chylomicron, Central Lacteal
Large Intestine
By the time we reach the large intestine, should have digested and absorbed all of the food -> if not bacteria are going to thrive off it
-
(1) waste that is left
- However before feces leaves the body we want to ____ a certain amount of water, electrolytes, and minerals
- Moves from terminal portions of the ileum through ______ valve into the _____ -> ______ colon -> ______ colon -> _____ colon -> ______ colon -> _______ -> ____ sphincters
-
Feces
- absorb
- Ileocecal valve -> cecum -> ascending -> transverse -> descending -> sigmoid -> rectum -> anal sphincters
Large Intestine Structure
- Internal Anal Sphincter = ______ muscle through autonomic and enteric nervous system, is it voluntary?
- External Anal Sphincter = ______ muscle, is it voluntary?
- (1) band of connective tissue that runs down length of colon
- (1) Circular compartments - indentatations are bands of muscle
- smooth muscle, not voluntary
- skeletal muscle, voluntary so we can choose when to relax and defecate
- Taenia coli
- Haustra
Motility in the Large Intestine
2 forms of Motility
- Motility through (1) AKA (1) - desiged to _____ feces and enhance _____ with colon wall to enhance absorption
- (1) AKA (1)
- Segmentation Contraction (Haustral Contractions), MIXING MOVEMENT, enhance contact
- Peristalsis (Mass Movements)
Haustral Contractions
- ____ and _____ movement
- Result of autonomous ______ of colonic smooth muscle
- Frequency ___-___ /hour
- ______ movement*
- Controlled by local _____ via intrinsic nerve plexuses
- Slow and Nonpropulsive
- rhythmicity
- 2-3/hr
- Mixing
- reflexes
Mass Movements
- _______ Movement*
- Occurs __-__ times per day - usually after
- Drives feces __-___ length of colon in a few ____
- Stimulation - ______ reflex - via ______
- Propulsive Movement
- 3-4
- 1 - 3/4, seconds
- Gastrocolic reflex - Gastrin
- Very strong and can drive feces down entire colon within seconds*
- We have about 3-4 mass movements per day, usually after meals, strongly stimulated by gastrin*
The Defecation Reflex
- Stimulated by ______ on ____ wall
- Stretch receptors in the rectal wall cause _______ of the (1)
- (1) - when voluntarily relaxed allows defecation
- Distension, rectal
- relaxation, Internal Anal Sphincter
- External Anal Sphincter
Consequence of Delayed Defecation
- If defecation is delayed too long, mass movements ____ down, internal sphincter _____ so feces can move ____ out of the _____ and decrease ______, can lose _____ to defecate
- Consequence =
- slow, contracts, back out of rectum, decrease distension, lose desire to defecate
- As long as feces stays in the colon, more and more water is absorbed, feces becomes hard -> risk of CONSTIPATION
What’s so great about fiber?
- Aids in ______ in a few ways
- Adds ______ to chyme and eventually feces
- Increases the ______ of chyme
- Too much of a good thing =
- Digestion
- Volume
- Osmolarity
- Osmotic diarrhea - osmolarity too high
Diarrhea
Causes
- Rapid Colonic motility - no time to absorb water like with bacterial _____ ( want to get it out)
- Osmotic Diarrhea: undigested material through _____ deficiencies (ie (1), (1) is something we don’t digest and raises the osmolarity of stool) -> retain too much ____ and cause osmotic bacteria
- Toxins
- enzyme deficiencies ie lactose intolerance, fiber, water
