Digestive System 4 Flashcards
(34 cards)
What is Segmentation in the Small Intestine?
Alternating areas of contraction and relaxation that creates a Backward/forward motion (“massaging chyme”)
What does segmentation allow for in the Small Intestine? (4)
- Mechanical Digestion - Physical Breakdown
- Assists in mixing chyme with Chemical Digestive Enzymes, promoting chemical digestion
- Brings the chyme in contact with the Absorptive Surfaces of the digestive tract, enhancing the Absorption of nutrients
- Propulsive Motility - The strength of segmentation is often greater in the early segments of the small intestine compared to the later segment
What is the Rate and Regulation of segmentation (number per minute)?
Parasympathetic and Gastrin: Parasympathetic stimulation and the hormone gastrin increase the rate of segmentation.
Sympathetic:
Sympathetic stimulation decreases the rate of segmentation.
What is Intestinal juice?
Collective name for:
- Accessory contributions – added at duodenum from pancreas, liver, gallbladder.
- Gastric emptying – stomach into duodenum.
- Intestinal secretions along small intestine – water and mucus
Small intestine:
- Final digestion to absorbable size.
- 90% of absorption (10% in large intestine and stomach).
- Typically ~3 – 5 hours in small intestine
What Breaks down Disaccharides to monosaccharides? (glucose, galactose, fructose)
brush border enzymes on apical membrane
What Breaks Down Sucrose?
Sucrose is broken into glucose and fructose by sucrase
What Breaks down Lactose?
Lactose is broken down to glucose and galactose by lactase
(lactase limited – lactose intolerance)
What Breaks down Maltose?
Maltose is broken down to glucose and glucose by maltase
How do Monosaccarhides Cross the Apical Membrane and the Basolateral Membrane?
- Facilitated diffusion glucose transporter or GLUT (fructose).
- Secondary active transporter involving sodium (glucose or galactose).
- All cross basolateral membrane by facilitated diffusion GLUTs
What is Transported through the Apical Membrane by Primary Active Transport? (ignore)
Fructose via GLUT
glucose transporter
What is Transported through the Apical Membrane by Secondary Active Transport?
Glucose and Galactose cotransported with Sodium (Na+)
What Happenes to CHO in the Small Intestine?
Most CHO digested/absorbed within proximal 20% of small intestine.
Some CHO indigestible – soluble and insoluble fiber.
How many different Glucose Transporters are in Humans?
14 different GLUT in humans.
How are small peptides broken to individual AAs?
small peptides (made up of 2 – 3 amino acids; AAs) are broken down by brush border enzymes on apical membrane
How do Small Peptides and Amino Acids Cross the Apical Membrane?
Small peptides (ones not broken down by brush border enzymes) cross by Secondary Active Transporter involving H+.
Individual AAs by Secondary Active Transporter involving sodium.
both cotransprort into intestinal epithilial cell
What happens to Small Peptides and Amino Acids once they cross the Apical Membrane and are now in the Intestinal Epithalial Cell?
- Small peptides that crossed apical membrane intact are broken down to individual AAs by peptidases inside cell.
- All cross basolateral by facilitated diffusion amino acid transporters.
How many Amino Acids and Amino Acid Transporters in Humans?
20 AAs with different amino acid transporters (~10 in humans)
What needs to happen to fats before they can be absorbed?
“Pre-treatment” or emulsification
- Pieces of triglycerides from globule are coated in bile
salts and phospholipids converting large fat globules
into smaller emulsification droplets
Nature of Bile Salts and Phospholipids:
Bile salts and phospholipids have a unique structure with a polar (hydrophilic or water-loving) side and a nonpolar (hydrophobic or fat-loving) side
How do the Bile Salts and Tryglycerides arrange themselves during Emulsification? Why?
Bile salts and phospholipids surround triglyceride molecules with their polar sides facing outward.
This arrangement makes the triglycerides more water-soluble. The polar side interacts with water, while the nonpolar side interacts with the fat
The polar surface of the emulsified triglyceride droplets faces outward, creating a repulsion between droplets. This prevents them from coalescing back into larger fat globules.
Why is Emulsification considered a One-Way process?
Emulsification is considered a one-way process, as it prevents the reaggregation of fat molecules into larger masses.
How does Emulsification help Pancreatic Lipase?
The emulsification process exposes a greater surface area of the triglyceride droplets.
This increased surface area facilitates the action of pancreatic lipase, an enzyme that breaks down triglycerides into monoglycerides (glycerol bound to one fatty acid) and two separate fatty acids
What breaks down triglycerides into monoglyceride?
pancreatic lipase
