Week 1 Study Guide: Upper Digestive System

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Questions and Answers

What is the primary role of salivary amylase in the digestive system?

To aid in the churning motion of the stomach

To facilitate nutrient absorption in the intestines

To break down starch into simpler sugars (correct)

To break down dietary fats

Which layer of the gastrointestinal tract is primarily responsible for absorption and digestion?

Submucosa

Mucosa (correct)

Muscularis Externa

Serosa

Which of the following is NOT a function of the digestive system?

Digestion

Hormonal regulation (correct)

Ingestion

Absorption

What mechanism is responsible for the mixing waves observed in the stomach?

Churning Signup and view all the answers

Which accessory organ is primarily involved in the production of digestive enzymes?

Pancreas Signup and view all the answers

What type of digestion involves the physical breakdown of food without chemical change?

Mechanical digestion Signup and view all the answers

What is the main purpose of the submucosa layer in the gastrointestinal tract?

To provide support and contain blood vessels Signup and view all the answers

Which of the following digestive processes primarily occurs in the mouth?

Mechanical digestion Signup and view all the answers

What is the primary function of bile in digestion?

Emulsifies fats Signup and view all the answers

Where does bile flow directly after being stored in the gallbladder?

Cystic duct Signup and view all the answers

What is the main role of the duodenum in the digestive process?

Chemical digestion and neutralization Signup and view all the answers

Which of the following statements about the small intestine is true?

The ileum absorbs vitamin B12 and bile salts. Signup and view all the answers

What happens to pepsin in the duodenum?

It is inactivated. Signup and view all the answers

Which structure connects the ileum to the large intestine?

Ileocecal junction Signup and view all the answers

What type of epithelium is primarily found in the mucosa of the small intestine?

Simple columnar Signup and view all the answers

Which part of the digestive system does bile not enter?

Pancreatic duct Signup and view all the answers

What is the primary function of the stomach's mucosa layer?

Secretion of gastric juices and hormones Signup and view all the answers

Which of the following best describes the process of hydrochloric acid production in the stomach?

Carbon dioxide and water form carbonic acid, dissociating into hydrogen and bicarbonate ions. Signup and view all the answers

What role does the oblique muscle play in the stomach?

It helps turn the bolus into chyme. Signup and view all the answers

Which accessory organ is primarily responsible for hormone production such as glucagon and insulin?

Pancreas Signup and view all the answers

What is the correct sequence of the biliary tree flow?

Liver → R/L Hepatic ducts → Common hepatic duct → Cystic duct → Common bile duct → Small intestine Signup and view all the answers

What is the main function of the liver?

Production of bile Signup and view all the answers

Which nervous system is often referred to as the 'brain of the gut'?

Enteric nervous system Signup and view all the answers

What does the myenteric plexus primarily control?

Motility of the gastrointestinal muscles Signup and view all the answers

What stimulates the closure of the pyloric and ileocecal sphincters?

Parasympathetic innervation Signup and view all the answers

Which phase of gastric secretion begins with the thought, smell, or sight of food?

Cephalic phase Signup and view all the answers

What action does secretin primarily promote in response to acidic chyme?

Bile and pancreatic juice secretion Signup and view all the answers

Which hormone is known to stimulate hunger during the cephalic phase?

Ghrelin Signup and view all the answers

Which neurotransmitter is involved in long reflexes modulating GI tract motility?

Vagus nerve signals Signup and view all the answers

What triggers the intestinal phase of gastric secretion?

Food entering the small intestine Signup and view all the answers

The activation of which receptors stimulates local contractions of the muscularis layers in the digestive tract?

Chemoreceptors Signup and view all the answers

What does cholecystokinin (CCK) primarily stimulate?

Pancreatic enzyme secretion and bile ejection Signup and view all the answers

Which phase of deglutition is characterized by voluntary control?

Oral (Voluntary) Phase Signup and view all the answers

What is the primary secretion of mucous cells in the stomach?

Mucus Signup and view all the answers

Which cell type in the stomach is responsible for the secretion of hydrochloric acid (HCl)?

Parietal Cells Signup and view all the answers

What is the main function of bile?

Emulsification of fats Signup and view all the answers

During which phase of deglutition does the epiglottis cover the larynx?

Pharyngeal Phase Signup and view all the answers

What hormone is secreted by G cells in the stomach?

Gastrin Signup and view all the answers

What drives the bolus toward the stomach during the esophageal phase?

Peristalsis Signup and view all the answers

Which of the following statements about intrinsic factor is true?

It is essential for the absorption of vitamin B12. Signup and view all the answers

Study Notes

Upper Digestive System Overview

Gastrointestinal Tract: Muscular tube ~16 feet long, comprised of the mouth, pharynx, esophagus, stomach, small intestine, large intestine, and rectum.
Accessory Organs: Includes teeth, tongue, salivary glands, liver, gallbladder, pancreas, which assist in digestion but are not part of the GI tract.

Major Functions of the Digestive System

Ingestion: Intake of food.
Secretion: Release of enzymes and glandular products, such as saliva.
Propulsion/Motility: Movement and mixing of food (including peristalsis).
Digestion: Mechanically and chemically breaking down food.
Absorption: Uptake of nutrients and water into cells, blood, or lymph.
Compaction/Defecation: Formation and elimination of fecal waste.

Types of Digestion

Mechanical Digestion: Physical breakdown through actions like chewing in the mouth and churning in the stomach.
Chemical Digestion: Involves enzymes from salivary glands, stomach, pancreas, and small intestine that catalyze the breakdown of macromolecules.
Key Enzymes:
- Salivary amylase breaks down starch into simple sugars.
- Lingual lipase digests dietary fats in the mouth and stomach.

Layers of the Gastrointestinal Tract

Mucosa: Inner lining composed of epithelium, lamina propria, and muscularis mucosae; critical for digestion and absorption.
Submucosa: Contains blood vessels, lymphatics, and nerve plexus; supports absorption and detects stimuli.
Muscularis Externa: Consists of longitudinal and circular muscle layers, with an extra oblique layer in the stomach for mixing.
Serosa: Outer layer providing support to the GI tract.

Propulsion and Motility

Peristalsis: Coordinated muscle contractions that move contents through the GI tract.
Mixing Waves: Occur in the stomach to transform food into chyme.
Segmentation: Mixes food contents to enhance absorption.

Neural Innervation of the Gut

Enteric Nervous System: Also known as the “brain of the gut”, governs local control of digestion and motility.
Autonomic Nervous System:
- Parasympathetic (rest-digest) stimulates digestion.
- Sympathetic (fight-flight) inhibits digestive processes.

Deglutition (Swallowing) Phases

Oral Phase: Voluntary control; includes mastication and bolus formation.
Pharyngeal Phase: Involuntary; soft palate and epiglottis prevent nasopharyngeal entry and block airflow.
Esophageal Phase: Peristalsis moves the bolus to the stomach through the cardiac sphincter.

Gastric Glands and Cell Types in the Stomach

Mucous Cells: Secrete mucus to protect the stomach lining.
Parietal Cells: Produce hydrochloric acid (HCl) for protein breakdown, intrinsic factor for vitamin B12 absorption, and ghrelin for appetite stimulation.
Chief Cells: Secrete gastric lipase for lipid digestion and pepsinogen, an inactive precursor to pepsin for protein digestion.
G Cells: Release gastrin to increase gastric acid secretion and enhance intestinal motility.

Bile Production, Transport, and Function

Bile Role: Emulsifies fats, facilitating digestion and absorption.
Production: Synthesized by liver hepatocytes; transported through the biliary tree: liver → hepatic ducts → common hepatic duct → gallbladder.
Release: Bile is expelled from gallbladder into the duodenum to aid fat digestion.

Small Intestine Overview

Parts:
- Duodenum: Begins at the pyloric sphincter; neutralizes stomach acid and mixes digestive juices.
- Jejunum: Primary site for digestion and nutrient absorption.
- Ileum: Absorbs vitamin B12 and bile salts; connects to large intestine at ileocecal junction.

Small Intestine Functions

Mixes chyme, continues digestion of nutrients, absorbs ~90% of nutrients and water.

Histology and Microanatomy of the Small Intestine

Mucosa: Simple columnar epithelium specialized for nutrient absorption.
Muscularis: Inner circular and outer longitudinal muscle layers enhance motility.

Digestive Reflexes

Short Reflexes: Local contractions triggered by stretch or chemical signals.
Long Reflexes: Involve central nervous system; modulate motility via vagal and sacral nerve signals.

Phases of Gastric Secretion

Cephalic Phase: Triggered by thoughts/smells of food, stimulates gastric secretion pre-ingestion.
Gastric Phase: Initiated by food in the stomach; enhances gastric secretion and motility.
Intestinal Phase: Begins when food enters the small intestine; regulates gastric activity and promotes pancreatic and bile secretion.

Hormones of the Digestive System

Stomach Hormones:
- Gastrin: Secretion triggered by stomach distension; enhances gastric activities.
- Ghrelin: Stimulates appetite during the cephalic phase.
Small Intestine Hormones:
- Secretin: Released in response to acidic chyme; promotes bile and pancreatic secretions.
- Cholecystokinin (CCK): Induces pancreatic enzyme secretion and bile release upon fat/protein intake.
- Gastric Inhibitory Peptide (GIP): Secreted in response to lipids; inhibits gastric activities.

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Description

This quiz covers the organs and functions of the upper digestive system, including the gastrointestinal tract and accessory organs. Test your knowledge on the structure and components of the digestive system and their roles in digestion.