Human Digestive System Quiz

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

Which of the following is NOT a major subdivision of the digestive tract?

Large Intestine

Gallbladder (correct)

Stomach

Esophagus

What is the primary function of the salivary glands in the digestive system?

Mechanical processing of food

Absorption of nutrients

Storage of bile

Secretion of digestive enzymes (correct)

What is peristalsis?

The mechanical breakdown of food

The absorption of nutrients

The contraction of smooth muscle to propel food (correct)

The secretion of bile

Which function of the digestive system is responsible for the breakdown of food into smaller components?

Digestion (D) Signup and view all the answers

Which of the following neurotransmitters primarily excites gastrointestinal activity?

Acetylcholine (B) Signup and view all the answers

What is the role of the large intestine in the digestive system?

Absorption of water and electrolytes (C) Signup and view all the answers

Which of the following processes involves the movement of food through the alimentary tract?

Ingestion (D) Signup and view all the answers

Which organ is responsible for the storage of bile in the digestive system?

Gallbladder (D) Signup and view all the answers

What is primarily secreted by the mucous neck cells in the stomach?

Mucus (B) Signup and view all the answers

Which type of cell in the stomach secretes pepsinogen?

Peptic cells (A) Signup and view all the answers

What causes local epithelial stimulation in the gastrointestinal tract?

Tactile stimulation, chemical irritation, and distention (B) Signup and view all the answers

Which substance is NOT a characteristic of the gastric secretions?

Amylase (D) Signup and view all the answers

What is the role of hydrochloric acid in the stomach?

Activation of pepsinogen (C) Signup and view all the answers

Which glands are considered the principal salivary glands?

Parotid, submandibular, and sublingual glands (C) Signup and view all the answers

What is the primary function of esophageal secretions?

Lubrication for swallowing (C) Signup and view all the answers

What type of stimuli activates the enteric nervous system of the gut wall?

Mechanical presence of food (D) Signup and view all the answers

What forms do most proteins take when absorbed through intestinal epithelial cells?

Dipeptides, tripeptides, and some free amino acids (C) Signup and view all the answers

What mechanism provides energy for the absorption of most proteins?

Sodium co-transport mechanism (A) Signup and view all the answers

What percentage of fat is absorbed in the presence of bile micelles?

97 percent (B) Signup and view all the answers

What is a characteristic of the absorption of short- and medium-chain fatty acids?

They are absorbed directly into portal blood (D) Signup and view all the answers

What happens to fat absorption in the absence of bile micelles?

40 to 50 percent can be absorbed (D) Signup and view all the answers

What is the primary ion secreted by parietal cells to form hydrochloric acid?

Chloride ion (D) Signup and view all the answers

What is the approximate pH of the hydrochloric acid secreted by parietal cells?

0.8 (B) Signup and view all the answers

Which process allows hydrogen ions to replace potassium ions in the canaliculus?

Hydrogen-potassium ATPase activity (D) Signup and view all the answers

What role does carbonic anhydrase play in the secretion process of HCl?

It catalyzes the conversion of carbon dioxide and hydroxyl ions to bicarbonate. (C) Signup and view all the answers

What happens to pepsinogen when it comes in contact with hydrochloric acid?

It is activated to form pepsin. (D) Signup and view all the answers

What is the function of intrinsic factor secreted by parietal cells?

Assists in vitamin B12 absorption (C) Signup and view all the answers

What type of cells are primarily found in the pyloric glands?

Mucous cells (A) Signup and view all the answers

How is sodium reabsorbed by parietal cells during HCl secretion?

Active transport by a sodium pump (B) Signup and view all the answers

What role do peptidases play in digestion?

They split small peptides into amino acids. (B) Signup and view all the answers

Which enzymes are responsible for breaking down disaccharides?

Sucrase, maltase, isomaltase, and lactase. (C) Signup and view all the answers

What does cholesterol-ester-hydrolase specifically hydrolyze?

Cholesterol esters. (C) Signup and view all the answers

How much fluid is typically absorbed per day by the intestines?

8 to 9 liters. (C) Signup and view all the answers

Which secretion in the large intestine protects the intestinal wall?

Mucus. (A) Signup and view all the answers

What type of cells secrete mucins in the intestinal mucosa?

Goblet cells. (A) Signup and view all the answers

What is the purpose of the alkalinity of the large intestine's secretions?

To provide a barrier against fecal acids. (D) Signup and view all the answers

Which enzyme is involved in the hydrolysis of phospholipids?

Phospholipase A2. (C) Signup and view all the answers

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

Sodium co-transport mechanism (A) Signup and view all the answers

Which of the following statements about sodium absorption in the intestine is correct?

The body requires absorption of 25 to 35 grams of sodium daily. (D) Signup and view all the answers

What significantly enhances calcium absorption in the intestines?

Activated vitamin D (D) Signup and view all the answers

How does the structure of the small intestine enhance its absorptive capacity?

Villi and microvilli structures (C) Signup and view all the answers

Which ions are mostly actively absorbed in the small intestine?

Calcium and iron (B) Signup and view all the answers

Approximately what percentage of carbohydrate calories absorbed in the small intestine comes from glucose?

80% (C) Signup and view all the answers

What typically happens to sodium reserves during extreme diarrhea?

They may become depleted to lethal levels. (A) Signup and view all the answers

Which of the following monosaccharides is the least abundant in absorption?

Fructose (A) Signup and view all the answers

Study Notes

Digestive System, Digestion, and Absorption of Food

The alimentary tract delivers continual water, electrolytes, and nutrients to the body. This necessitates:
- Food movement through the tract.
- Digestive juice secretion and food digestion.
- Water and electrolyte absorption, along with digestive product absorption.
- Blood circulation carrying absorbed substances through gastrointestinal organs.
- Regulation of these functions by local, nervous, and hormonal systems.

Learning Objectives

Identify different parts of the digestive system and their roles in digestion.
Detail gastric secretion and HCl formation.
Describe different phases of digestion.
Explain digestion of food in the duodenum and small intestine.
Understand absorption of nutrients, ions, and water from the GI tract.

Components of the Digestive System

Digestive Tract:
- Oral Cavity (teeth, tongue, soft and hard palates)
- Pharynx
- Esophagus
- Stomach
- Small Intestine
- Large Intestine
Accessory Organs:
- Salivary Glands
- Liver
- Gallbladder
- Pancreas

Functions of the Digestive System

Ingestion
Mechanical processing
Digestion
Secretion
Absorption
Excretion

General Principles of Gastrointestinal Motility

Smooth muscle fibers in the GI tract are organized into bundles.
Longitudinal muscle bundles extend down the intestinal tract.
Peristalsis is smooth muscle contraction that moves food toward the rectum.

Digestive System and Digestion

The digestive system continually supplies the body with water, electrolytes, and nutrients.
Essential steps include movement of food, digestive juice secretion and digestion of food, absorption of water/electrolytes/digestion products, circulation of blood through organs to remove absorbed substances, and regulation by local, nervous, and hormonal systems.

Neurotransmitters/Neurohormones Secreted by Enteric Neurons

Acetylcholine, norepinephrine, adenosine triphosphate, serotonin, dopamine, cholecystokinin, substance P, vasoactive intestinal polypeptide, somatostatin, leuenkephalin, metenkephalin, and bombesin are secreted.
Acetylcholine typically stimulates GI activity.
Norepinephrine usually inhibits GI activity.

Mechanisms of Stimulation in Alimentary Tract Glands

Food mechanically stimulating a segment of the GI tract typically triggers gland secretions in that region, and sometimes adjacent regions.
Local mucosal stimulation also activates the enteric nervous system, responding to tactile stimulation, chemical irritation, and distension of the gut wall.

Daily Secretion of Intestinal Juices

Provides a table detailing the volume and pH of saliva, gastric secretion, pancreatic secretion, bile, small intestine secretion, Brunner's gland secretion, and large intestinal secretion.

Regulation of Glandular Secretion by Hormones

Gastrointestinal hormones are secreted from the gastrointestinal mucosa in response to food in the gut lumen.
These are typically polypeptides or polypeptide derivatives.

Salivary Glands and characteristics of saliva

There are parotid, submandibular, sublingual glands and small buccal glands.
Saliva has serous secretions containing ptyalin (a-amylase, a starch digesting enzyme) and mucus secretions containing mucin (acts for lubrication and surface protection).

Esophageal Secretion

Primarily mucous, this secretion lubricates for swallowing.
Simple mucous glands line the esophagus.

Gastric Secretion, Phases of Digestion, and Digestion in Duodenum and Small Intestine

Learning Objectives: To identify gastric secretion and HCl formation stages, stages of digestion, and duodenum/small intestine food digestion.

Gastric Secretions

Typical oxyntic glands comprise mucous neck cells (secrete mucus), peptic cells (secrete pepsinogen), and parietal cells (secreting HCl and intrinsic factor).
Secretion of hydrochloric acid is a complex mechanism involving potassium ions, sodium ions, and chloride ions.
HCl's concentration differs significantly from arterial blood during this process (much more acidic).

Basic Mechanism of Hydrochloric Acid Secretion

Parietal cells secrete a highly acidic solution (pH about 0.8) containing 160 millimoles of HCl per liter. This process involves active transport.

Secretion and Activation of Pepsinogen

Pepsinogen is the inactive form of pepsin.
Hydrochloric acid activates pepsinogen into the active protease pepsin.
Pepsin activity is optimal in highly acidic environments (pH 1.8-3.5).

Pyloric Glands

Mostly mucous cells.
Secrete some pepsinogen and substantial mucus.
Mucous lubricates food movement and protects the stomach wall from the digestive activity of gastric enzymes.
Pyloric glands also secrete gastrin (a hormone to control gastric secretion).

Phases of Gastric Secretion

Cephalic Phase: occurs before food enters, triggered by smell, taste, thought, or chewing of food.
Gastric Phase: stimulated by ingested food, involving long vagovagal reflexes, local enteric reflexes, and gastrin's action.

Pancreatic Secretion

Digestive enzymes are secreted by pancreatic acini.
Sodium bicarbonate and enzymes flow through a pancreatic duct that eventually connects with the hepatic duct.
Insulin is secreted by pancreatic islets of Langerhans directly into the bloodstream.

Pancreatic Digestive Enzymes

Trypsin and chymotrypsin break down proteins into peptides.
Carboxypolypeptidase breaks down peptides to amino acids.
Pancreatic amylase hydrolyzes starches, glycogen, most carbohydrates (except cellulose) to form mostly disaccharides.
Pancreatic lipase breaks down neutral fats into fatty acids and monoglycerides.
Cholesterol esterase hydrolyzes cholesterol esters.
Phospholipase splits fatty acids from phospholipids.

Digestion in the Small Intestine

Enterocytes in the mucosa, especially those covering villi, contain digestive enzymes.
Key enzymes are peptidases for small peptides to amino acids, sucrase, maltase, isomaltase, lactase for splitting disaccharides.
Intestinal lipase for splitting neutral fats into glycerol and fatty acids.

Digestion of Carbohydrates

Saliva and pancreatic amylase break down starches and glycogen.
Maltose and glucose polymers are partly digested.
Lactase and sucrase digest lactose and sucrose into glucose, galactose, and fructose respectively

Digestion of Proteins

Pepsin, trypsin, and chymotrypsin break down protein chains into peptides and free amino acids.
Carboxypeptidase further breaks down proteins into amino acids.

Digestion of Cholesterol Esters and Phospholipids

Cholesterol ester hydrolase and phospholipase A2 are enzymes that digest cholesterol esters and phospholipids.

Absorption of Water

Water is absorbed entirely by diffusion through the intestinal membrane.

Absorption of Ions

Sodium is secreted and absorbed in significant quantities through the intestinal secretions and daily diets.
Active transport mechanism is crucial for sodium absorption in the small intestine.
Adequate sodium absorption prevents net loss in the feces.
Excessive loss of intestinal secretions (e.g., diarrhea) can lead to sodium depletion.

Absorption of Bicarbonate Ions

Large quantities of bicarbonate ions must be reabsorbed from the small intestine due to high concentrations in pancreatic and bile secretions.

Absorption of Other Ions

Calcium ions are absorbed primarily in the duodenum via active transport mechanisms mediated by parathyroid hormone and vitamin D activation.
Iron, potassium, magnesium, phosphate, and other ions are also actively absorbed in the small intestine.

Absorption of Carbohydrates

Glucose is the most abundant absorbed monosaccharide (80% or more).
Glucose transport occurs via a sodium co-transport mechanism.
Galactose and fructose are primarily absorbed via facilitated diffusion.

Absorption of Proteins

Proteins, after digestion, are absorbed as di- and tri-peptides and amino acids through the intestinal mucosa using a sodium co-transport mechanism.

Absorption of Fats

Fatty acids, monoglycerides, and other breakdown products of fat digestion are mostly absorbed in the presence of bile micelles.
Short- and medium-chain fatty acids are absorbed directly into the portal blood, while long-chain fatty acids require conversion into triglycerides. Lymph channels absorb these triglycerides before they enter the bloodstream.

Secretions of the Large Intestine

Mucus is secreted by goblet cells within the large intestine lining to protect the intestinal wall from bacterial activity and acid in the feces. The alkaline nature of the mucus and sodium-bicarbonate acts as a barrier.

Anatomical Basis of Absorption

The total amount of fluid absorbed daily equals ingested fluids plus intestinal secretions (about 8-9 liters).
The small intestine absorbs most of the fluid, allowing only about 1.5 liters to move to the colon daily.

Absorptive Surface of the Small Intestinal Mucosa

Valvulae conniventes (folds of Kerckring) triple the surface area.
Villi and microvilli increase surface area 1000-fold, creating 250+ square meters for absorption in the small intestine.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Test your knowledge of the human digestive system with this quiz. From the major subdivisions of the digestive tract to the functions of various glands, this quiz covers essential concepts. Perfect for students studying biology or health sciences.