Gastrointestinal System Quiz

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Questions and Answers

Which layer of smooth muscle in the gastrointestinal tract causes constriction of the lumen?

Mucosal layer

Thick inner circumferential layer (correct)

Myenteric plexus

Thin outer longitudinal layer

What is the primary role of the myenteric plexus in the gastrointestinal system?

Generating electrical impulses for voluntary muscle movement

Secreting digestive juices

Facilitating nutrient absorption

Regulating gastrointestinal tract functions (correct)

Which muscle type in the gastrointestinal tract is under involuntary control?

Both A and B

Skeletal muscle

Cardiac muscle

Smooth muscle (correct)

What is the function of serosa in the gastrointestinal tract?

Lubricates and prevents friction with surrounding organs Signup and view all the answers

Which type of contraction is responsible for moving contents forward through the digestive tract?

Peristaltic contractions Signup and view all the answers

What process involves the chemical and mechanical breakdown of food into absorbable units?

Digestion Signup and view all the answers

Which type of contraction facilitates both digestion and absorption by mixing food with digestive juices?

Segmental contraction Signup and view all the answers

What is the term for the process of eating food?

Ingestion Signup and view all the answers

What is the primary enzyme involved in triglyceride digestion?

Lipase Signup and view all the answers

Which process primarily occurs in the small intestine?

Absorption of nutrients Signup and view all the answers

What role do bile salts play in fat digestion?

They emulsify fats into smaller micelles Signup and view all the answers

Which of the following is not a type of lipase involved in fat digestion?

Carboxypeptidase Signup and view all the answers

Defecation refers to which of the following processes?

Elimination of indigestible substances Signup and view all the answers

What is the primary function of trypsin and chymotrypsin in digestion?

Digest proteins Signup and view all the answers

Which of the following statements about absorption is correct?

Most absorption occurs in the small intestine. Signup and view all the answers

Which enzyme is known for specifically breaking down protein molecules?

Pepsin Signup and view all the answers

What is the primary function of the villi in the small intestine?

To increase the surface area for absorption Signup and view all the answers

Which component of the gastrointestinal system is responsible for nutrient absorption?

Mucosa Signup and view all the answers

What role do the microvilli play in the small intestine?

They increase surface area and have digestive enzymes Signup and view all the answers

What function does the large intestine primarily serve?

Formation of feces for elimination Signup and view all the answers

What is the main consequence of dysbiosis in individuals?

Development of certain diseases like diabetes and obesity Signup and view all the answers

How often do the epithelial cells lining the villi renew themselves?

Every 2-3 days Signup and view all the answers

What is the primary composition of the submucosa layer of the gastrointestinal tract?

Loose connective tissue Signup and view all the answers

What beneficial substance does the bacteria in the large intestine help produce?

Vitamin K Signup and view all the answers

What is the primary role of saliva in the digestive process?

Facilitating taste and digestion Signup and view all the answers

Which of the following glands secretes hydrochloric acid (HCl)?

Chief cell Signup and view all the answers

What component of gastric secretions combines with vitamin B12 to make it absorbable?

Intrinsic factor Signup and view all the answers

Which enzyme in saliva is responsible for starch digestion?

Amylase Signup and view all the answers

Which type of cell in the gastric glands secretes gastrin?

G cell Signup and view all the answers

What is the main function of the mucous neck cells in the gastric glands?

Secreting protective mucus Signup and view all the answers

Which component of saliva helps to neutralize acids in food?

Water and ions Signup and view all the answers

What is one of the primary functions of saliva aside from aiding digestion?

Moistening the oral cavity for easier swallowing Signup and view all the answers

Which hormone is produced in the stomach and duodenum and stimulates acid secretion?

Gastrin Signup and view all the answers

What action does Cholecystokinin primarily have?

Stimulates pancreatic enzyme secretion Signup and view all the answers

Which hormone is released in response to fats and proteins and inhibits food intake?

Gastric inhibitory polypeptide Signup and view all the answers

What stimulates the release of Secretin?

Fat, protein, and acid Signup and view all the answers

Which hormone is responsible for stimulating motility in the gastrointestinal tract?

Motilin Signup and view all the answers

Where is Gastric inhibitory polypeptide produced?

Duodenum and jejunum Signup and view all the answers

Which hormone is released primarily in response to acetylcholine?

Motilin Signup and view all the answers

What effect does Secretin have on gastric secretion?

Inhibits gastric secretion Signup and view all the answers

What role do bile salts and phospholipids play in fat digestion?

They emulsify large fat globules into smaller, accessible pieces. Signup and view all the answers

How do monoglycerides and fatty acids enter absorptive cells?

By simple diffusion or by forming micelles. Signup and view all the answers

What happens to the sphincter of Oddi when fat is present in the duodenal lumen?

It relaxes, allowing bile to enter the duodenum. Signup and view all the answers

What is the primary function of the gallbladder regarding bile secretion?

To store and concentrate bile. Signup and view all the answers

What type of digestion is primarily involved in breaking down food into absorbable units?

Chemical digestion facilitated by enzymes. Signup and view all the answers

What does the secretion from the small intestine mainly consist of?

Water, salt, and mucus. Signup and view all the answers

What is the role of mechanical digestion in the digestive system?

To prepare food for subsequent chemical digestion. Signup and view all the answers

What triggers the secretion of cholecystokinin (CCK) in the digestive process?

Fat in the duodenal lumen. Signup and view all the answers

Study Notes

Physiology (0603302)

Course name: Physiology
Chapter: Gastrointestinal system
Semester: Summer 2023/2024
Instructor: Dr. Mohammad A. Abedal-Majed
Institution: The University of Jordan, School of Agriculture

The Digestive System

The gastrointestinal (GI) system is responsible for providing the body with nutrients and electrolytes from outside the body to maintain homeostasis.

Structure of the Gastrointestinal System

The digestive system consists of two main parts:
- GI tract (mouth, pharynx, esophagus, stomach, small intestine, large intestine, rectum, and anus)
- Accessory glandular organs (salivary glands, liver, gallbladder, exocrine and endocrine glands)

Mouth

Contains muscles for mechanical digestion
Salivary glands secrete saliva for lubrication, food degradation, and carbohydrate digestion
- Carbohydrate digestion begins in the mouth with salivary amylase.
Food passes through the pharynx, a passageway for food and connecting the GI and respiratory system.
The esophagus carries food rapidly.
Minimal absorption occurs except for some drugs.

Stomach

Contains a special lining that secretes digestive juices (pepsinogen and HCl acid) for protein digestion.
Digestive enzymes originate within gastric pits.
Gastric pits contain cells that secrete HCL and pepsinogen.
Strong muscular walls mix food and digestive juices.
Food moves from the stomach to the small intestine through the pylorus sphincter.

Small Intestine

Contains enzymes from the pancreas and small intestine for further food digestion.
Villi and microvilli increase surface area for absorption and digestion.
Cells lining villi and microvilli (enterocytes) help with carbohydrate and protein digestion.
Villi cells renew every 2-3 days from stem cells in the crypts.
Microvilli (brush border) contain enzymes that aid in carbohydrate and protein digestion.

Large Intestine

Absorbs a small amount of water and electrolytes.
Contains beneficial bacteria for vitamin K production and lipid molecule processing.
Patients with issues in beneficial bacteria may develop health problems like diabetes and obesity.
Compacts and forms feces for elimination.
Fiber in the diet aids in movement for constipation prevention.

Structure of the Gastrointestinal System (Layers)

Mucosa: The innermost layer of the GI tract, composed of epithelial cells lining the tract, which plays a protective role, and is responsible for secretion and absorption.
Submucosa: The layer below the mucosa, containing connective tissue and a network of neurons called the submucosal plexus, enabling the tract to expand and contract.

Muscle Layer

Two perpendicular smooth muscle layers:
- Inner, thick circumferential layer for constricting and narrowing the lumen.
- Outer longitudinal layer for shortening the lumen.
The GI tract is largely under involuntary control, but the mouth and end of the rectum are under voluntary control.
The enteric nervous system (network of neurons) regulates the GI tract functions.
Serosa: The outermost layer, a thin layer of connective tissue that lubricates and prevents friction with neighboring structures.

Processing of Food (General)

Ingestion: The process of eating.
Digestion: Chemical and mechanical breakdown of food.
Motility: Muscular contractions in the digestive tract for mixing food and propelling it through the digestive tract (peristalsis.)
Phasic contractions: Short, alternating contractions that propel food (e.g., peristalsis.)
Segmental contractions: Move food back and forth for mixing with digestive juices.
Tonic contractions: Long, sustained contractions found at sphincters.

Processing of Food and Secretion

Secretion: Glands release substances like water, electrolytes, enzymes, bile salts, and mucus into the digestive tract.
- It's an energy-dependent process mediated by neural or hormonal stimulation.
- Specific examples of fluid and volume secretion include saliva, gastric, bile, and pancreatic secretions.

Gastric Gland Cells

Exocrine cells
- Parietal cells secrete HCl acid and intrinsic factor.
- Chief cells secrete pepsinogen (converted to pepsin by HCl) for protein digestion.
- Mucous neck cells secrete mucus for protection.
Pyloric gland contains G cells that secrete gastrin (stimulates parietal cell activity), and mucus.
Cardiac glands secrete alkaline mucus.
Endocrine cells include G and D cells.

Stomach Acid (HCl) Secretion

Parietal cells actively transport H+ (hydrogen ions) into the gastric lumen.
Cl- (chloride ions) are transported and actively join H+ in the lumen.
Carbonic anhydrase regulates this process.

HCl Functions

Activates digestive enzymes.
Breaks down connective tissue.
Denatures proteins.
Kills ingested microorganisms.

Pepsinogen Secretion

Present in chief cells, is released by regulated exocytosis.
Pepsinogen is inactive; HCl converts it to the active pepsin enzyme used in protein digestion.
Autocatalysis: Pepsin also cleaves pepsinogen, forming more active pepsin.

Intrinsic Factor

Secreted by parietal cells.
Forms a complex with vitamin B12, enabling its absorption in the intestines.

Gastric Mucosal Barrier

Luminal membranes of gastric cells are impermeable to H+.
Tight junctions prevent HCL from passing between cells.
Mucus coating provides a physical barrier.
HCO3- rich mucus serves as a chemical barrier by neutralizing acid near epithelial cells.

Pancreatic Secretion

Endocrine part secretes insulin and glucagon (blood sugar control.)
Exocrine part secretes digestive enzymes and bicarbonate.
- Secretion is stimulated and regulated by hormones like secretin and cholecystokinin.

Bile Secretion (Liver)

Bile salts and phospholipids emulsify fats into smaller pieces, aiding in lipase access and digestion.
Bile is produced by the liver and stored in the gallbladder.
The Sphincter of Oddi controls bile entry into the duodenum.
95% of bile salts are recycled via enterohepatic circulation.

Small Intestine Secretion

Aids in lubrication and facilitates enzymatic digestion.
Doesn't secrete digestive enzymes, but the enterocytes (cells lining the villi and microvilli) contain digestive enzymes assisting with the absorption of digested nutrients from the lumen into the blood or lymphatic system.

Digestion (Overview

Mechanical digestion: Chewing, mixing, churning in the stomach
Chemical Digestion: Actions by enzymes in digestive juices.

Digestion: Overview (Table)

Table summarizes the digestion processes for carbohydrates, proteins, and fats.

Carbohydrate Digestion

Breaks down complex carbohydrates into monosaccharides (glucose, galactose, and fructose) for absorption.
Salivary amylase and pancreatic amylase are involved in the initial breakdown.
Intestinal enzymes (sucrase, maltase, and lactase) further break down disaccharides to monosaccharides.

Protein Digestion

Breaks down proteins into amino acids for absorption.
Pepsin acts in the stomach, breaking down protein.
Pancreatic enzymes (trypsin, chymotrypsin, carboxypeptidase) and intestinal aminopeptidases and carboxypeptidases continue the breakdown in the small intestines.

Fat Digestion

Bile salts emulsify fat globules, increasing surface area for lipase action.
Lipase breaks down triglycerides into fatty acids and monoglycerides for absorption.

Absorption

The passage of digested nutrients into the bloodstream (or lymph) for the body to use.
Most occurs in the small intestine (specialized villi and crypts.)

Defecation

Elimination of indigestible food substances.

Regulation of Gastrointestinal Tract Functions

Intrinsic (intrinsic nervous system and endocrine cells in digestive tract walls) and extrinsic (nervous system and endocrine systems outside digestive tract) controls.
Hormones like secretin and gastrin regulate various digestive functions.

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Description

Test your knowledge on the anatomy and physiology of the gastrointestinal tract. This quiz covers smooth muscle functions, neural controls like the myenteric plexus, and processes involved in digestion and absorption. Perfect for students studying human biology or medical professionals wanting a refresher.