Oral Cavity and Esophagus Overview
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Questions and Answers

What is the primary function of the stomach?

  • Storage of food
  • Production of hormones
  • Absorption of nutrients
  • Digestion of food (correct)

The stomach is responsible for the majority of nutrient absorption in the digestive system.

False (B)

What is chyme?

A semi-liquid mixture of partially digested food.

Hydrochloric acid (HCl) in the stomach helps to _____ proteins and kill pathogens.

<p>denature</p> Signup and view all the answers

Match the digestive secretions with their functions:

<p>Hydrochloric acid (HCl) = Kills pathogens and denatures proteins Pepsin = Breaks proteins into smaller peptides Mucus = Protects the stomach lining Gastric lipase = Begins digestion of fats</p> Signup and view all the answers

What is the primary function of the tongue in the oral cavity?

<p>Moving food and forming a bolus (A)</p> Signup and view all the answers

The esophagus is composed entirely of smooth muscle.

<p>False (B)</p> Signup and view all the answers

What are the three main pairs of salivary glands?

<p>Sublingual, submandibular, parotid</p> Signup and view all the answers

The extbf{______} closes the windpipe during swallowing.

<p>epiglottis</p> Signup and view all the answers

How much saliva do the salivary glands produce in a day?

<p>1.5 liters (A)</p> Signup and view all the answers

Match each type of salivary gland to its secretion characteristics:

<p>Parotid glands = Watery solution of enzymes Sublingual glands = Mucus-rich saliva Submandibular glands = Mixed saliva with mucus and enzymes</p> Signup and view all the answers

Peristalsis is the voluntary contraction of esophageal muscles.

<p>False (B)</p> Signup and view all the answers

What is the role of the lower esophageal sphincter?

<p>To allow food to pass into the stomach and prevent backflow</p> Signup and view all the answers

What is the main function of the migrating motor complex?

<p>Sweet food remnants and bacteria out of the GI tract (D)</p> Signup and view all the answers

Peristalsis involves contractions that move food in a retrograde direction.

<p>False (B)</p> Signup and view all the answers

What role does gastrin play in the stomach?

<p>Gastrin promotes acid release from parietal cells.</p> Signup and view all the answers

The stomach produces two enzymes: pepsin and __________.

<p>gastric lipase</p> Signup and view all the answers

Match the following gastric secretions to their functions:

<p>Gastrin = Stimulates acid secretion Pepsin = Begins protein digestion Intrinsic factor = Facilitates vitamin B12 absorption Somatostatin = Inhibits gastric secretion</p> Signup and view all the answers

What is one of the primary actions of gastric acid?

<p>Activation of pepsin (B)</p> Signup and view all the answers

Acid secretion can create a luminal pH as high as 7 in the stomach.

<p>False (B)</p> Signup and view all the answers

What are the two muscle types involved in segmental contractions?

<p>Circular muscles and longitudinal muscles.</p> Signup and view all the answers

The __________ is responsible for short-distance propulsion of intestinal contents.

<p>segmental contraction</p> Signup and view all the answers

Match the following ducts with their functions:

<p>Gastric pits = Lead to gastric glands Gastric glands = Produce gastric acid and enzymes Parietal cells = Secrete hydrochloric acid Chief cells = Secretes pepsinogen</p> Signup and view all the answers

What is the pH of the cytoplasm in parietal cells?

<p>7.2 (C)</p> Signup and view all the answers

Pepsinogen is the active form of the enzyme pepsin.

<p>False (B)</p> Signup and view all the answers

What is the alkaline tide?

<p>The increase in blood pH due to bicarbonate absorption during acid secretion.</p> Signup and view all the answers

The stomach contributes to food transformation by digesting it into a mixture called __________.

<p>chyme</p> Signup and view all the answers

What is the primary function of salivary amylase?

<p>To initiate carbohydrate breakdown (C)</p> Signup and view all the answers

Saliva only serves one function in the mouth.

<p>False (B)</p> Signup and view all the answers

What is the term for the softened, moistened mass of food that is created during chewing?

<p>bolus</p> Signup and view all the answers

The muscularis ____________ is a thin layer of smooth muscle that alters the effective surface area for absorption.

<p>mucosae</p> Signup and view all the answers

Match the part of the gastrointestinal tract with its description:

<p>Mucosa = Inner lining with three layers Submucosa = Middle layer with blood and nerve vessels Muscularis Externa = Outer wall with two muscle layers Serosa = Outer covering of the digestive tract</p> Signup and view all the answers

Which of the following components is NOT found in saliva?

<p>Lipids (B)</p> Signup and view all the answers

Saliva helps wash the teeth and keep the tongue free of food particles.

<p>True (A)</p> Signup and view all the answers

What are the two main layers of the muscularis externa in the gastrointestinal tract?

<p>Inner circular layer and outer longitudinal layer</p> Signup and view all the answers

The ___________ moves food through the gastrointestinal tract from the mouth to the anus.

<p>motility</p> Signup and view all the answers

What is one of the protective functions of saliva?

<p>Prevention of dental decay (A)</p> Signup and view all the answers

The myenteric plexus controls motor activity in the muscularis mucosae.

<p>False (B)</p> Signup and view all the answers

What is the role of the submucosal plexus?

<p>To innervate epithelial cells and smooth muscle of the muscularis mucosae</p> Signup and view all the answers

Food is mechanically broken down in the gastrointestinal tract primarily through __________.

<p>chewing</p> Signup and view all the answers

Which of the following is a function of the mucosal epithelium?

<p>Absorbs nutrients into blood (A)</p> Signup and view all the answers

Flashcards

Chyme definition

Semi-liquid mixture of digested food in the stomach

Stomach's digestion method

Mechanical and chemical; muscles churn, secretions break down

Hydrochloric acid (HCl) function

Creates acidic environment for protein denaturation and kills pathogens

Stomach's primary function

Digestion, not absorption

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Stomach absorption examples

Limited absorption of water, alcohol, drugs, and some ions.

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Esophagus function

A muscular tube that moves food from the throat to the stomach using peristalsis.

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Esophageal Muscle Types

The upper two-thirds of the esophagus is composed of skeletal muscle, while the lower one-third is smooth muscle.

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Saliva Production

Three pairs of salivary glands (parotid, submandibular, and sublingual) produce 1.5 liters of saliva daily.

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Salivary Gland Types

Parotid (mostly enzymes), submandibular (mix of mucus and enzymes), and sublingual (mostly mucus).

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Mechanical Digestion

Chewing breaks down food into smaller pieces using the jaws, teeth, and tongue.

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Bolus Formation

The tongue forms a mass of food and saliva ready for swallowing.

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Epiglottis Function

A flap of tissue that prevents food from entering the windpipe during swallowing.

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Lower Esophageal Sphincter

A ring-like muscle that relaxes to allow food into the stomach and prevents backflow.

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Migrating Motor Complex

A digestive process that sweeps food remnants and bacteria from the upper GI tract to the large intestine.

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Peristalsis

Progressive waves of contractions that move food through the GI tract.

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Segmental contractions

Short segments of intestine alternately contract and relax, mixing the intestinal contents.

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Chyme

Soupy mixture of uniformly small particles created in the stomach after chemical and mechanical digestion.

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Gastrin

A hormone that promotes acid release in the stomach.

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Parietal cells

Stomach cells that secrete gastric acid (HCl).

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Gastric acid (HCl)

Acid that activates pepsin, denatures proteins, kills bacteria, and inactivates amylase.

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Pepsin

Enzyme that digests proteins; activated by acid in the stomach.

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Pepsinogen

Inactive form of pepsin, produced by chief cells.

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Gastric lipase

Enzyme that breaks down triglycerides.

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Intrinsic factor

Protein that binds vitamin B12, enabling absorption in the intestine.

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Somatostatin

Negative feedback signal that inhibits gastric acid secretion.

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Histamine

Paracrine signal that stimulates acid secretion.

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Cephalic phase

Part of the gastric phase triggered by the thought, smell, or sight of food.

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Saliva Function

Saliva moistens and lubricates food for easier swallowing, begins starch digestion, dissolves food for taste, and provides defense against bacteria and viruses.

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Amylase Function

An enzyme in saliva that breaks down starch into maltose.

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Chemical Digestion

The breakdown of food into simpler molecules by enzymes.

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Mucosa Layers

The inner lining of the GI tract has three layers: epithelium, lamina propria, and muscularis mucosae.

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Lamina Propria Function

Connective tissue layer containing blood/lymph vessels and immune cells for nutrient absorption and defense.

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Muscularis Mucosae Function

Thin muscle layer that alters the surface area for absorption by moving villi.

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Submucosa Function

Connective tissue layer with large blood/lymph vessels and a nerve plexus (Meissner's plexus), controlling secretions.

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Muscularis Externa Layers

Two layers of smooth muscle (circular and longitudinal) that move food along the GI tract.

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Myenteric Plexus

Nerve network controlling the motor activity of the GI tract's muscularis externa.

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GI Tract Motility Patterns

Contractions that move and mix food, maximizing exposure to enzymes.

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Serosa Function

Connective tissue membrane covering the GI tract, a continuation of the peritoneal membrane.

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GI Tract Functions

Protection, secretion, resorption which is prevalent in specific areas of the GI tract.

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Lingual Lipase

Enzyme in saliva that initiates fat breakdown.

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Study Notes

Oral Cavity and Esophagus (Cephalic Phase)

  • Anatomy: Mouth contains jaws (maxilla and mandible), teeth (20 primary, 32 adult), tongue (with papillae), epiglottis, and esophagus (initial skeletal muscle, transitioning to smooth muscle).
  • Salivary Glands: Three pairs (sublingual, submandibular, parotid) produce saliva (up to 1.5 liters daily). Saliva composition varies, with parotid producing watery enzyme solution, sublingual producing mucus-rich, and submandibular producing a mixture.
  • Movement: Ingestion, mechanical digestion (chewing), swallowing (tongue pushes bolus, epiglottis directs to esophagus), peristalsis (esophageal muscle contractions), lower esophageal sphincter (relaxes to let food enter stomach, prevents backflow).
  • Secretions: Saliva (water, mucus, enzymes like amylase for starch breakdown, electrolytes).
  • Food Transformation: Mechanical (chewing creates bolus), chemical (amylase breaks down starch, lingual lipase breaks down fats).
  • Absorption: Tongue's underside absorbs some nutrients. Taste papillae stimulate digestion processes.

Stomach (Gastric Phase)

  • Function: Intermediary between eating and intestinal digestion, regulating chyme entrance to prevent overload.
  • Secretions:
    • Gastrin: Secreted by G cells, stimulated by amino acids/peptides, stomach distension, and neural reflexes. Promotes acid release.
    • Gastric Acid (HCl): Secreted by parietal cells, creates very low pH environment (1-3).
      • Functions include protein denaturation, pepsin activation, killing microorganisms, and inactivating salivary amylase.
    • Pepsin: Secreted by chief cells as pepsinogen, then activated by acid to digest proteins (crucially collagen, facilitating meat digestion).
    • Gastric Lipase: Co-secreted with pepsin, aids fat digestion (less than one-third of fat digestion occurs here).
    • Paracrine Secretions: Histamine (from ECL cells, stimulates acid secretion), somatostatin (from D cells, negative feedback signal to inhibit acid release), intrinsic factor (with parietal cells, complexes with vitamin B12 for absorption).
  • Food Transformation: Mechanical churning and mixing with acid and enzymes create chyme (semi-liquid).
  • Absorption: Limited absorption of water, alcohol, specific drugs (e.g., aspirin), some ions, but most in small intestine.

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Description

Explore the anatomy, function, and processes of the oral cavity and esophagus in the cephalic phase of digestion. This quiz covers the structure of the mouth, movements involved in ingestion, and the roles of salivary glands and secretions in food transformation. Test your knowledge on the mechanisms of swallowing and the importance of saliva.

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