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Questions and Answers
What is the primary function of villi in the small intestine?
What is the primary function of villi in the small intestine?
- To increase surface area for nutrient absorption (correct)
- To absorb water from the food
- To produce digestive enzymes
- To transport waste materials
What structural feature characterizes villi?
What structural feature characterizes villi?
- Long and tubular form
- Spherical bladders
- Finger-like projections (correct)
- Flat and broad shape
Why are blood vessels important in the function of villi?
Why are blood vessels important in the function of villi?
- They remove toxins from the intestine
- They facilitate the digestion of proteins
- They help in the movement of food
- They enable the absorption of nutrients into the bloodstream (correct)
Where in the human body would you find villi?
Where in the human body would you find villi?
How do villi contribute to nutrient absorption?
How do villi contribute to nutrient absorption?
What is the primary mechanism by which the substance enters the epithelial cells?
What is the primary mechanism by which the substance enters the epithelial cells?
What is the difference between how the substance enters and leaves the epithelial cells?
What is the difference between how the substance enters and leaves the epithelial cells?
Which membrane is responsible for the substance's entry into epithelial cells?
Which membrane is responsible for the substance's entry into epithelial cells?
Which process requires energy to move the substance across the cell membrane?
Which process requires energy to move the substance across the cell membrane?
What is the final destination of the substance after it leaves the epithelial cells?
What is the final destination of the substance after it leaves the epithelial cells?
What ions are involved in the absorption process described within the intestine?
What ions are involved in the absorption process described within the intestine?
How many sodium ions are transported along with one glucose molecule?
How many sodium ions are transported along with one glucose molecule?
What type of carriers facilitate the transport of sodium ions and glucose in the intestine?
What type of carriers facilitate the transport of sodium ions and glucose in the intestine?
Where does the absorption of sodium ions and glucose take place in the body?
Where does the absorption of sodium ions and glucose take place in the body?
What is the primary role of sodium ions in the absorption of glucose?
What is the primary role of sodium ions in the absorption of glucose?
Which of the following substances is NOT known to inhibit iron absorption?
Which of the following substances is NOT known to inhibit iron absorption?
What is the most prevalent theory regarding the mechanism of iron absorption?
What is the most prevalent theory regarding the mechanism of iron absorption?
What is the primary source of phytic acid, known to inhibit iron absorption?
What is the primary source of phytic acid, known to inhibit iron absorption?
The text mentions two possible mechanisms for iron absorption. What are they?
The text mentions two possible mechanisms for iron absorption. What are they?
Which of the following is NOT a known inhibitor of iron absorption?
Which of the following is NOT a known inhibitor of iron absorption?
What happens to Na+ after it enters the cells?
What happens to Na+ after it enters the cells?
How is glucose transported out of the cells?
How is glucose transported out of the cells?
Which membrane is referred to as the basolateral membrane?
Which membrane is referred to as the basolateral membrane?
What process is used to move glucose from the cell into the bloodstream?
What process is used to move glucose from the cell into the bloodstream?
What role does the basolateral membrane play in nutrient absorption?
What role does the basolateral membrane play in nutrient absorption?
What is the primary role of the hormone mentioned in the colon?
What is the primary role of the hormone mentioned in the colon?
What does the absorption of Cl- primarily occur?
What does the absorption of Cl- primarily occur?
Why is the conservation of Na+ and water vital during dehydration?
Why is the conservation of Na+ and water vital during dehydration?
Which condition is primarily addressed by this hormone?
Which condition is primarily addressed by this hormone?
What component is mostly conserved by this hormone in the colon during periods of dehydration?
What component is mostly conserved by this hormone in the colon during periods of dehydration?
Flashcards
Villi
Villi
Finger-like projections in the small intestine that increase surface area for nutrient absorption.
What do villi absorb?
What do villi absorb?
Villi are covered in a thin layer of epithelial cells that help to absorb nutrients from digested food.
How do villi transport nutrients?
How do villi transport nutrients?
Villi are richly supplied with blood vessels, which transport absorbed nutrients throughout the body.
Why are villi important for absorption?
Why are villi important for absorption?
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What is the main role of villi in digestion?
What is the main role of villi in digestion?
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Absorption in the Small Intestine
Absorption in the Small Intestine
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Na+ Linked Carriers
Na+ Linked Carriers
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Lumen of the Intestine
Lumen of the Intestine
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Sodium-Glucose Co-transport
Sodium-Glucose Co-transport
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Sodium-Glucose Transporter
Sodium-Glucose Transporter
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Passive diffusion
Passive diffusion
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Active diffusion
Active diffusion
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Basolateral membrane
Basolateral membrane
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Luminal membrane
Luminal membrane
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Nutrient absorption
Nutrient absorption
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Sodium Ion Transport
Sodium Ion Transport
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Glucose Transport
Glucose Transport
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Facilitated Diffusion
Facilitated Diffusion
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Active Transport
Active Transport
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What hormone conserves water and sodium in the colon?
What hormone conserves water and sodium in the colon?
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Where is most chloride absorbed?
Where is most chloride absorbed?
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What is the lumen of the intestine?
What is the lumen of the intestine?
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What is nutrient absorption in the small intestine?
What is nutrient absorption in the small intestine?
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What are Na+ linked carriers?
What are Na+ linked carriers?
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What inhibits iron absorption?
What inhibits iron absorption?
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How does pancreatic juice affect iron absorption?
How does pancreatic juice affect iron absorption?
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How is iron possibly absorbed?
How is iron possibly absorbed?
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Is iron absorption an active process?
Is iron absorption an active process?
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What remains unknown about iron absorption?
What remains unknown about iron absorption?
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Study Notes
Digestion and Absorption
- Digestion breaks down carbohydrates, proteins, and lipids using enzymes.
- Absorption involves specialized epithelial cells.
- Most absorption occurs in the small intestine; some in the stomach, and none in the esophagus.
- The small intestine's structure (mucosal folds, villi, microvilli) increases surface area for absorption, about 600 folds.
- The colon absorbs water and electrolytes.
Carbohydrate Digestion and Absorption
- Carbohydrates are ingested as starch, sucrose, lactose, and cellulose.
- Cellulose is indigestible.
- Digestion starts in the mouth with salivary amylase (ptyalin), partially breaking down starch into smaller glucose polymers.
- Pancreatic amylase continues this process in the small intestine.
- Brush border enzymes (lactase, sucrase, maltase, and alpha-dextranase) further break down disaccharides into monosaccharides (glucose, fructose, and galactose).
- These monosaccharides are absorbed via active transport or facilitated diffusion.
Protein Digestion and Absorption
- Protein digestion starts in the stomach with pepsin and HCl, initially breaking down large proteins.
- Proteolytic enzymes (endopeptidases and exopeptidases) in the small intestine further break down peptides into smaller peptides and amino acids.
- Brush border enzymes (peptidases) in the small intestine break down peptides into amino acids.
- Amino acids are absorbed via active transport across the intestinal epithelial cells.
Lipid Digestion and Absorption
- Bile salts emulsify fats in the duodenum.
- Pancreatic lipase breaks down triglycerides into free fatty acids and monoglycerides.
- These products combine with bile salts, phospholipids, cholesterol, and form micelles.
- Free fatty acids, monoglycerides, and other components pass through the intestinal cell membrane via passive diffusion.
- Chylomicrons (combined lipids and proteins) are then formed and released from the cells.
- Cholesterol, glycerol, and fatty acids are absorbed through the bloodstream.
Water and Electrolyte Absorption
- Water passively follows the sodium gradient into epithelial cells.
- Electrolytes (sodium, chloride, potassium) are actively absorbed in the small intestine and colon, sometimes exchanged across the membrane for sodium.
- Sodium absorption can also be regulated by the hormone aldosterone.
Iron Absorption
- Iron absorption occurs primarily in the upper part of the small intestine.
- Ferrous iron (Fe++) is more readily absorbed than ferric iron (Fe+++).
- Factors like vitamin C increase iron absorption, while phosphates, oxalates, and phytic acid can inhibit absorption.
Vitamin Absorption
- Water-soluble vitamins are absorbed passively, except for vitamin C, B1, and B12.
- B12 requires intrinsic factor for absorption.
- Lipid-soluble vitamins are absorbed similarly to lipids (with micelles and chylomicrons).
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Description
This quiz explores the structure and function of villi in the small intestine. You'll learn about their role in nutrient absorption, the mechanisms involved, and the importance of blood vessels. Test your knowledge on how substances are transported across epithelial cells.
