Podcast
Questions and Answers
What is the first step in the digestion of dietary fat?
What is the first step in the digestion of dietary fat?
What enzyme is responsible for hydrolyzing triglycerides into monoglycerides and free fatty acids?
What enzyme is responsible for hydrolyzing triglycerides into monoglycerides and free fatty acids?
What are micelles primarily formed from?
What are micelles primarily formed from?
What process allows monoglycerides and free fatty acids to cross the luminal plasma membrane?
What process allows monoglycerides and free fatty acids to cross the luminal plasma membrane?
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After absorption, what happens to monoglycerides and free fatty acids in the epithelial cells?
After absorption, what happens to monoglycerides and free fatty acids in the epithelial cells?
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What type of absorption mechanism is involved in the movement of fatty acids and monoglycerides into epithelial cells?
What type of absorption mechanism is involved in the movement of fatty acids and monoglycerides into epithelial cells?
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Where do the absorbed triglycerides enter after being re-esterified in the epithelial cells?
Where do the absorbed triglycerides enter after being re-esterified in the epithelial cells?
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What is the main role of bile salts in fat digestion and absorption?
What is the main role of bile salts in fat digestion and absorption?
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Which of the following statements about fatty acid absorption is incorrect?
Which of the following statements about fatty acid absorption is incorrect?
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What effect does the PNS have on intestinal smooth muscle contraction?
What effect does the PNS have on intestinal smooth muscle contraction?
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Which neurotransmitter is released by the PNS to aid in gastrointestinal motility?
Which neurotransmitter is released by the PNS to aid in gastrointestinal motility?
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During fasting, which substance is secreted from the upper duodenum to increase GI motility?
During fasting, which substance is secreted from the upper duodenum to increase GI motility?
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What is the primary function of pancreatic amylase in carbohydrate digestion?
What is the primary function of pancreatic amylase in carbohydrate digestion?
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How are monosaccharides absorbed in the small intestine?
How are monosaccharides absorbed in the small intestine?
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Which disaccharide is broken down by the enzyme lactase?
Which disaccharide is broken down by the enzyme lactase?
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What effect does SNS innervation have on intestinal smooth muscle contraction?
What effect does SNS innervation have on intestinal smooth muscle contraction?
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Which of the following enzymes is responsible for breaking down sucrose?
Which of the following enzymes is responsible for breaking down sucrose?
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Which carbohydrate makes up approximately 50% of a typical US diet?
Which carbohydrate makes up approximately 50% of a typical US diet?
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What happens to salivary amylase in the stomach?
What happens to salivary amylase in the stomach?
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What initiates the segmentation contractions in the small intestine?
What initiates the segmentation contractions in the small intestine?
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Which reflex is associated with the ileum segment of the small intestine?
Which reflex is associated with the ileum segment of the small intestine?
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Which factor influences the rate of segmentation contractions in the small intestine?
Which factor influences the rate of segmentation contractions in the small intestine?
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What is the main function of segmentation in the small intestine?
What is the main function of segmentation in the small intestine?
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What occurs during the migrating motility complex (MMC)?
What occurs during the migrating motility complex (MMC)?
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How long does it typically take for contents to pass through the small intestine?
How long does it typically take for contents to pass through the small intestine?
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What stimulates the release of gastrin in the gastrointestinal tract?
What stimulates the release of gastrin in the gastrointestinal tract?
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What happens to segmentation contractions when most of the meal has been absorbed?
What happens to segmentation contractions when most of the meal has been absorbed?
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What characterizes the contractions in the small intestine segments?
What characterizes the contractions in the small intestine segments?
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Which part of the small intestine demonstrates a higher rate of segmentation contractions?
Which part of the small intestine demonstrates a higher rate of segmentation contractions?
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Which statement about the effects of PNS and SNS on SI contractions is true?
Which statement about the effects of PNS and SNS on SI contractions is true?
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What is the segmentation rate in the duodenum compared to the ileum?
What is the segmentation rate in the duodenum compared to the ileum?
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Why does the ileocecal sphincter contract more with pressure on the cecal side?
Why does the ileocecal sphincter contract more with pressure on the cecal side?
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Where are dietary disaccharides primarily broken down?
Where are dietary disaccharides primarily broken down?
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Which enzymes are responsible for digesting polysaccharides?
Which enzymes are responsible for digesting polysaccharides?
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What transport method is required for the absorption of single amino acids?
What transport method is required for the absorption of single amino acids?
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What is another name for enterokinase?
What is another name for enterokinase?
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Which pancreatic enzyme is activated by enterokinase?
Which pancreatic enzyme is activated by enterokinase?
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What is the primary function of aminopeptidases in protein digestion?
What is the primary function of aminopeptidases in protein digestion?
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Which type of transport is utilized for the absorption of amino acids?
Which type of transport is utilized for the absorption of amino acids?
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How are di- and tripeptides absorbed in the intestinal epithelium?
How are di- and tripeptides absorbed in the intestinal epithelium?
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What role do brush border membrane enzymes (BBE) play in protein absorption?
What role do brush border membrane enzymes (BBE) play in protein absorption?
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In protein absorption, which process is associated with facilitated diffusion?
In protein absorption, which process is associated with facilitated diffusion?
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Which enzymes are responsible for the initial digestion of proteins in the duodenum?
Which enzymes are responsible for the initial digestion of proteins in the duodenum?
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What type of peptide requires digestion by brush border enzymes before absorption?
What type of peptide requires digestion by brush border enzymes before absorption?
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Which of the following is not a product of trypsinogen activation?
Which of the following is not a product of trypsinogen activation?
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Study Notes
Fat Digestion and Absorption
- Fats are emulsified by bile salts in the lumen of the small intestine
- Lipase hydrolyzes triglycerides into monoglycerides (MG) and free fatty acids (FFA)
- These water-insoluble products are carried by water-soluble micelles
- MG and FFA diffuse from the micelles and through the luminal membrane
- They are re-esterified to form triglycerides inside the epithelial cell
- These aggregates are coated with lipoprotein which aids absorption
- Short or medium chain fatty acids are passively absorbed
Segmentation
- The primary means of motility in the small intestine
- It is initiated by pacesetter cells in the intestinal wall
- Segmentation contractions occur in the duodenum due to local distension
- Gastrin initiates ileum segmentation, via the gastroileal reflex
- Gastrin is released by the presence of chyme in the stomach
- It takes 3-5 hours for chyme to travel through the small intestine
- Segmentation contractions in the duodenum are faster than those in the ileum, proximal to distal
Migrating Motility Complex (MMC)
- MMC occurs after the absorption of a meal
- This is an in-between-meal motility pattern
- It involves repeated peristaltic waves that occur every 1.5 hours
- The MMC is a clean-up type motility
- It helps to clear the intestine after the meal
Innervation of the Small Intestine
- The Parasympathetic Nervous System (PNS) increases intestinal smooth muscle contraction
- The PNS releases Acetylcholine (Ach) and motilin
- Motilin is secreted from the upper duodenum during fasting and increases GI motility
- The Sympathetic Nervous System (SNS) decreases intestinal smooth muscle contraction
Carbohydrate Digestion
- The small intestine absorbs dietary carbohydrates, which make up around 50% of a typical US diet
- Digestion of carbohydrates in the mouth is facilitated by salivary amylase which breaks down starch
- Salivary amylase is inactivated in the stomach
- Pancreatic amylase further digests starch into disaccharides
- Disaccharides are broken down into monosaccharides by brush border enzymes (BBE) at the brush border membrane. These include Lactase, Maltase, and Sucrase.
- The monosaccharides are absorbed at the small intestine BBM
- Glucose and galactose are transported by active transport.
- Glucose and Fructose are transported by facilitated diffusion
Brush Border Membranes
- Enterokinase, also known as enteropeptidase, activates pancreatic enzyme trypsinogen
- This produces trypsin, chymotrypsin, and carboxypeptidase
- Aminopeptidases complete protein digestion by breaking down smaller peptide fragments into amino acids.
Protein Digestion and Absorption
- The small intestine houses brush border enzymes that further digest proteins
- Trypsin, chymotrypsin, and carboxypeptidase digest the proteins.
- Amino acids are passively absorbed through the basal membrane (BLM) via the Na+ and amino acid co-transporters
- Di and tripeptides are transported through the BLM in an H+ dependent manner via H+-dependent cotransporters.
- Oligopeptides require further digestion via BBE before absorption
- Facilitated diffusion is used to transport amino acids through the basolateral membrane
True or False
- The PNS increases and the SNS decreases contraction of the small intestine. True
- The rate of duodenum and ileum segmentation is the same. False
- The ileocecal sphincter contracts more with pressure on the cecal side to prevent bacterial-laden LI contents from entering the small intestine. True
- Dietary disaccharides are broken down at the BBM by BBEs. True
- Salivary amylase is the only enzyme that digests polysaccharides. False
- Single amino acid absorption requires dependent active transport, di and tri peptides H+ dependent active transport. True
- Within SI epithelial cells, MGs and FFAs re-esterify to form a TG. True
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Description
This quiz covers the processes of fat digestion and absorption, emphasizing the role of bile salts, lipase, and the formation of micelles. It also explores the motility of the small intestine, particularly segmentation contractions and their regulatory mechanisms. Test your understanding of these essential digestive processes!
