Digestive System Quiz - Small Intestine Functions

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Questions and Answers

What is the primary function of the duodenal glands?

Store residues temporarily and eliminate them as feces

Absorb most of the remaining water from indigestible food residues

Secrete enzymes for final digestion of chyme

Secrete mucus to neutralize acidic chyme (correct)

What type of muscular contraction primarily occurs in the small intestine after a meal?

Peristalsis

Migrating motor complex (MMC)

Reverse peristalsis

Segmentation (correct)

What initiates the migrating motor complex (MMC) in the small intestine?

Distension of the mucosa

Increase in the hormone motilin (correct)

Neural reflexes from the stomach

Presence of undigested fats in the intestine

What is the primary function of the ileocecal valve?

Regulate the flow of chyme from the small intestine into the large intestine (D) Signup and view all the answers

Which of the following is NOT a feature unique to the large intestine?

Villi (D) Signup and view all the answers

Which of the following is NOT a role of the large intestine in digestion?

Final digestion of carbohydrates and proteins (D) Signup and view all the answers

What is the key stimulus for the secretion of intestinal juice?

Distension or irritation of the mucosa (D) Signup and view all the answers

Which of the following is NOT a factor that regulates the movement of food into the duodenum?

Gastric motility (A) Signup and view all the answers

Where are brush border enzymes primarily located?

Plasma membrane of absorptive cells (B) Signup and view all the answers

What is the primary role of the teniae coli in the large intestine?

Create the haustra (D) Signup and view all the answers

Which type of cell in the small intestine is primarily responsible for nutrient and electrolyte absorption?

Enterocytes (D) Signup and view all the answers

What is the primary function of Paneth cells in the small intestine?

Secreting antimicrobial agents (A) Signup and view all the answers

Which component of the mucosa protects the intestine against microorganisms?

Peyer’s patches (B) Signup and view all the answers

Which cell type produces intestinal juice in the small intestine?

Enterocytes (D) Signup and view all the answers

Why are the numbers of lymphoid follicles and Peyer’s patches increased in the distal part of the small intestine?

To provide greater immune protection (C) Signup and view all the answers

What type of muscle composes the internal anal sphincter?

Smooth muscle (C) Signup and view all the answers

Which parts of the colon are classified as retroperitoneal?

Ascending and descending parts (A) Signup and view all the answers

What type of epithelium lines the anal canal?

Stratified squamous epithelium (A) Signup and view all the answers

Which feature is absent in the large intestine compared to the small intestine?

Circular folds (A) Signup and view all the answers

What is the primary function of the mucus-producing goblet cells in the large intestine?

Protection (A) Signup and view all the answers

What is the primary function of enzymatic hydrolysis in digestion?

To break down macromolecules into absorbable monomers (C) Signup and view all the answers

Which enzymes are primarily responsible for the breakdown of starch into oligosaccharides?

Salivary amylase and pancreatic amylase (A) Signup and view all the answers

Which of the following statements about nutrient absorption is accurate?

Polar molecules require active transport for absorption (A) Signup and view all the answers

What initiates carbohydrate digestion in the human body?

Salivary amylase (A) Signup and view all the answers

Which of the following types of carbohydrates can be absorbed directly by the intestine?

Monosaccharides (C) Signup and view all the answers

Where does digestion of carbohydrates primarily continue after the mouth?

In the small intestine with pancreatic enzymes (A) Signup and view all the answers

Which substance enters the bloodstream after absorption from the intestinal lumen?

Monosaccharides (B) Signup and view all the answers

What role do tight junctions play in the absorption process?

They enable selective absorption by controlling passage through cells. (B) Signup and view all the answers

What role do pancreatic proteases play in digestion?

They break down proteins into smaller peptides and amino acids. (C) Signup and view all the answers

Which enzyme is responsible for removing one amino acid at a time from the end of a protein chain?

Carboxypeptidase (C) Signup and view all the answers

How are amino acids absorbed across the apical membrane of absorptive epithelial cells?

Via secondary active transport carriers. (A) Signup and view all the answers

What is the primary function of bile salts in lipid digestion?

To emulsify large fat globules into smaller droplets. (C) Signup and view all the answers

What is contained in a chylomicron?

Triglycerides, phospholipids, cholesterol, and proteins. (C) Signup and view all the answers

What is the fate of chylomicrons after exiting the basolateral membrane?

They enter lymphatic vessels called lacteals. (B) Signup and view all the answers

Which enzymes found on the brush border further digest oligopeptides and dipeptides?

Carboxypeptidases and dipeptidases. (B) Signup and view all the answers

How do lipid digestion products reach the intestinal epithelial cells?

From micelles through diffusion. (C) Signup and view all the answers

What type of proteins help break down nucleic acids into nucleotide monomers?

Pancreatic nucleases (D) Signup and view all the answers

Which vitamins are absorbed in the small intestine via diffusion or passive/active transporters?

Water-soluble vitamins (B) Signup and view all the answers

How is sodium ion absorption coupled in the gastrointestinal tract?

With the active absorption of glucose and amino acids (A) Signup and view all the answers

What regulates calcium ion absorption in the body?

Vitamin D and parathyroid hormone (B) Signup and view all the answers

What is the primary mechanism for water absorption in the small intestine?

Osmosis (C) Signup and view all the answers

Which nutrient's absorption is notably linked to the body's need rather than a fixed amount?

Iron (D) Signup and view all the answers

Where in the gastrointestinal tract is most of the water absorption accomplished?

Small intestine (A) Signup and view all the answers

What happens to potassium ions during the absorption process?

They are absorbed through simple diffusion in response to osmotic gradients. (A) Signup and view all the answers

Which enzyme is responsible for breaking nucleotides down into free nitrogenous bases, pentose sugars, and phosphate ions?

Nucleosidases and brush border enzymes (D) Signup and view all the answers

What is the remaining amount of water in feces after absorption in the intestines?

100 ml (C) Signup and view all the answers

Study Notes

Digestive System Overview

The digestive system is responsible for processing food, extracting nutrients, and eliminating waste.
It comprises organs like the oral cavity, esophagus, stomach, small intestine, large intestine, and accessory organs.

Digestive System Part II

The digestive system's structures are the oral cavity, salivary glands, esophagus, stomach, pancreas, gallbladder, large intestine, and small intestine.
Chapter 23, sections 23.1-23.11, cover the information.
The specific page numbers are from 874 to 924.
Accessory organs aid small intestine digestion: the liver, gallbladder, and pancreas.

The Liver

The liver is the largest gland in the body (~3 lbs).
It consists of four lobes: right, left, caudate, and quadrate.
The gallbladder lies on the inferior surface of the right lobe.
The falciform ligament separates the larger right lobe from the smaller left lobe and suspends the liver from the diaphragm and anterior abdominal wall.
The lesser omentum anchors the liver to the stomach.
The hepatic artery proper and hepatic portal vein enter the liver at the porta hepatis.
Bile leaves via the left and right hepatic ducts, fusing into a common hepatic duct.
The cystic duct connects with the gallbladder.
The bile duct forms from the union of the common hepatic and cystic ducts.
Liver lobules are structural and functional units with hexagonal shapes.
Hepatocytes (liver cells) are in plates that filter and process nutrient-rich blood.
The central vein is located along the longitudinal axis of the lobule.
Liver sinusoids are leaky capillaries between hepatic plates, lined with stellate macrophages.
Hepatocytes produce 900 ml of bile daily.
The liver also processes bloodborne nutrients (storing glucose as glycogen, making plasma proteins), stores fat-soluble vitamins, performs detoxification (converting ammonia to urea), and excretes bilirubin and phagocytoses old red blood cells, leukocytes, and bacteria, and synthesizes most clotting factors.
Bile is a yellow-green alkaline solution with bile salts, bilirubin (main bile pigment from hemoglobin), cholesterol, triglycerides, phospholipids, and electrolytes.
The enterohepatic circulation recycles bile salts.
Reabsorption in the ileum and return via the hepatic portal vein accounts for 95% of secreted bile salts.

The Gallbladder

The gallbladder is a thin-walled muscular sac on the inferior surface of the liver.
It stores and concentrates bile by absorbing water and ions.
Honeycomb folds allow the gallbladder to expand as it fills
Muscular contraction releases bile into the cystic duct and then into the common bile duct.
The gallbladder stores and concentrates bile.

The Pancreas

The pancreas is mostly retroperitoneal, with its head encircled by the duodenum and its tail abutting the spleen.
It has endocrine and exocrine functions.
Endocrine function is the secretion of insulin and glucagon by pancreatic islet cells.
The pancreas secretes pancreatic juice
Acini are clusters of secretory cells
They produce zymogen granules containing proenzymes.
Ducts secrete to the duodenum via the main pancreatic duct; smaller ducts produce water and bicarbonate.
Pancreatic juice contains water, bicarbonate (neutralizes acidic chyme), and digestive enzymes (inactive forms requiring activation).
Example enzymes are proteases (for proteins), amylase (for carbohydrates), lipases (for lipids), and nucleases (for nucleic acids).

The Small Intestine

The small intestine is the major organ of digestion and absorption, extending from the pyloric sphincter to the ileocecal valve (~7-13 ft during life; ~20 ft in a cadaver).
It has a small diameter of 2.5-4 cm (1.0-1.6 inches).
The subdivisions are the duodenum (retroperitoneal), jejunum (~2.5 m or 8 ft), and ileum (~3.6 m or 12 ft).
The jejunum has the most features.
Modifications for absorption include: circular folds, villi, and microvilli, increasing the surface area significantly for absorption.
The superior mesenteric artery supplies oxygenated blood, and veins drain nutrient-rich blood into the superior mesenteric veins, then the hepatic portal vein, and finally into the liver.
The small intestine's nerve supply includes parasympathetic innervation (via the vagus nerve) and sympathetic innervation (from thoracic splanchnic nerves).
The small intestine's mucosa contains enterocytes (absorptive cells), goblet cells, enteroendocrine cells, and Paneth cells.

The Large Intestine

The large intestine frames the small intestine on three sides, extending from the ileocecal valve to the anus.
It has a much shorter length than the small intestine (1.5 m vs. 6 m), but larger diameter (~7 cm).
Its major functions include absorbing water from indigestible food residues, absorbing metabolites produced by bacteria, storing residues temporarily, and eliminating them as feces.
The large intestine is divided into the cecum, appendix, ascending colon, transverse colon, descending colon, sigmoid colon, rectum, and anal canal. Different parts of the colon have specialized functions.
The wall has the same basic architecture as other GI sections but includes modifications for function, like the lack of circular folds and villi, abundant deep crypts, and mucus-producing goblet cells.
The anal canal has an internal anal sphincter (smooth muscle) and an external anal sphincter (skeletal muscle).
The colon is retroperitoneal (except transverse and sigmoid parts), anchored to the posterior abdominal wall by mesocolons.
Mucus is produced, and the mucus protects and assists in passage.
The large intestine's nerve supply includes parasympathetic and sympathetic components.
Haustral contractions, • Slow segmenting movements in the ascending and transverse colon. • Mass movements, powerful contraction, ~3-4 times a day.
Gastrocolic reflex triggers mass movements during/after meals.
Defecation reflex is triggered by distension in the rectum, involves relaxation of internal anal sphincter, and can be voluntarily controlled by the external anal sphincter.
Bacterial microbiota in the large intestine has metabolic functions (fermentation of indigestible sugars / produce short-chain fatty acids; some vitamins), keep pathogenic bacteria in check (preventing harmful bacteria from crossing gut epithelium; immune system functions; dendritic cells).

Regulation of Hormone and Nerve Control in Digestion

Hormonal controls involve cholecystokinin (CCK) release by duodenal enteroendocrine cells in response to proteins & fats, and secretin release in response to acidic chyme. • Stimulates pancreatic acinar cells for enzyme-rich pancreatic juice which causes contraction of the gallbladder and relaxation of the hepatopancreatic sphincter to release bile into duodenum. • Stimulates duct cells in pancreas for bicarbonate-rich pancreatic juice.
Neural pathways include long reflexes (vagus nerve) and short reflexes that weakly stimulate gallbladder contraction and pancreatic secretion during cephalic and gastric phases.

Processing of Nutrients

Different digestive enzymes break down different food molecules: proteins, carbohydrates, lipids, and nucleic acids.
The breakdown products are absorbed into the bloodstream and transported to the liver and cells.
Specific processes are detailed per nutrient (carbohydrates, proteins, lipids, and nucleic acids).

Absorption of Vitamins, Electrolytes and Water

Water-soluble and fat-soluble vitamins are absorbed and transported in specific ways.
Electrolytes (primarily Na⁺, Cl⁻, K⁺, HCO₃⁻, and Ca²⁺) are actively absorbed, often coupled with the absorption of other nutrients.
Water absorption is primarily through osmosis based on solute concentration gradients generated by active transport of substances in the intestines.

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Description

Test your knowledge on the functions and processes of the small intestine. This quiz covers key concepts such as the roles of glands, muscular contractions, and enzyme functions. Dive deeper into the anatomy and physiology of digestion with targeted questions.