Human Digestive System Quiz

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Questions and Answers

What initiates gastric emptying from the stomach into the small intestine?

Release of gastrin hormone

Peristalsis of smooth muscle contractions (correct)

Presence of fat in the stomach

High acidity in the stomach

Which group of cells in the stomach is responsible for releasing hydrochloric acid (HCl)?

Chief cells

G cells

Mucous cells

Parietal cells (correct)

What effect does high levels of fat in the small intestine have on gastric emptying?

Inhibits gastric emptying (correct)

Stimulates gastric emptying

Has no effect on gastric emptying

Delays gastric emptying temporarily

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

Chemical digestion Signup and view all the answers

Which of the following is NOT an exocrine cell type found in the gastric pits?

G cells Signup and view all the answers

Where does the majority of nutrient absorption occur in the small intestine?

Jejunum Signup and view all the answers

What is the primary role of chief cells in the stomach?

Releasing pepsinogen Signup and view all the answers

Which structure primarily functions to neutralize stomach acid entering the duodenum?

Brunner’s glands Signup and view all the answers

What is the role of Peyer's Patches found in the ileum?

Mucosal immunity Signup and view all the answers

What is segmentation in the context of the small intestine?

A mixing and propelling process Signup and view all the answers

What is the main function of saliva in the oral cavity?

It provides antibacterial protection. Signup and view all the answers

Which type of teeth is primarily responsible for tearing food?

Canine Signup and view all the answers

What is the primary enzyme found in saliva that aids in carbohydrate digestion?

Amylase Signup and view all the answers

What structural feature of the oral cavity helps in guiding and containing food during chewing?

Lips and cheeks Signup and view all the answers

What process is described as mechanical digestion in the oral cavity?

Mastication of food by teeth Signup and view all the answers

How many deciduous teeth does a human typically have?

20 Signup and view all the answers

Which component of saliva primarily helps to clean the mouth?

Lysozyme Signup and view all the answers

What is the role of the tongue in the oral cavity?

It helps in mechanical breakdown and bolus formation. Signup and view all the answers

What is the primary function of the pharynx?

To serve as a passageway for both air and food Signup and view all the answers

What type of muscle is present in the upper third of the esophagus?

Skeletal muscle Signup and view all the answers

During which phase of swallowing does the epiglottis fold to close off the windpipe?

Pharyngeal Phase Signup and view all the answers

What triggers the opening of the lower esophageal sphincter?

The arrival of the bolus Signup and view all the answers

What kind of muscle is found in the lower third of the esophagus?

Smooth muscle Signup and view all the answers

What is the duration of the swallowing process, from beginning to end?

Approx. 9 seconds Signup and view all the answers

Which phase of swallowing can be initiated voluntarily?

Buccal Phase Signup and view all the answers

What mechanism primarily moves the bolus toward the stomach during the esophageal phase?

Peristalsis Signup and view all the answers

What is the primary function of the intestinal phase during digestion?

To control the rate of gastric emptying Signup and view all the answers

Which hormones are released from the duodenum and inhibit gastric secretions?

CCK and secretin Signup and view all the answers

What triggers the activation of the pancreas to release bicarbonate in the intestinal phase?

Decreased stomach pH Signup and view all the answers

What is the role of stretch and chemoreceptors in the duodenum during the intestinal phase?

Inhibit gastric acid secretion Signup and view all the answers

Which reflex is responsible for increasing motility and secretion throughout the small intestine due to stomach distension?

Gastroenteric reflex Signup and view all the answers

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

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

What is the effect of the gastroileal reflex in the digestive process?

Facilitates the opening of the ileocecal valve Signup and view all the answers

What structural feature of the small intestine helps further increase the surface area for absorption beyond villi?

Microvilli Signup and view all the answers

What is the primary function of the cephalic phase of digestion?

Prepares the stomach to receive food Signup and view all the answers

What sensory triggers can initiate the cephalic phase?

Taste and sight of food Signup and view all the answers

Which nerve is primarily involved in the signaling of the cephalic phase?

Vagus nerve Signup and view all the answers

During the gastric phase, which of the following physiological changes occurs in the stomach?

Elevated pH levels Signup and view all the answers

Which receptors are stimulated during the gastric phase due to the distension of the stomach?

Stretch receptors Signup and view all the answers

What role does the myenteric plexus play during the gastric phase?

Stimulates smooth muscle contractions Signup and view all the answers

What type of cells in the stomach secrete hydrochloric acid (HCl)?

Parietal cells Signup and view all the answers

What is the primary consequence of the stimulation of secretory cells during both the cephalic and gastric phases?

Release of digestive enzymes and acid Signup and view all the answers

Study Notes

Digestive System - Part 2

The digestive system, Part 2, covers the oral cavity, pharynx, esophagus, stomach and small intestine.

Oral Cavity/Mouth

Structures: Hard palate, soft palate, teeth, tongue, salivary glands, uvula, palatine tonsil.
Functions: Mechanical breakdown (chewing), some chemical breakdown (enzymes begin digestion), no absorption.

Mechanical Digestion

Oral cavity: Lips, cheeks, and palate guide and contain food.
Mastication: Mechanical digestion by teeth.
Saliva: Produced by salivary glands and released into the mouth (99.5% water, electrolytes, mucus).
Salivary Amylase: Enzyme for carbohydrate digestion.
Lysozyme: Antibacterial enzyme.
Saliva also aids in motility, taste, cleaning the mouth, and speaking.

Tongue

Structure: Skeletal muscle.
Function: Mechanical breakdown; mixes food with saliva and compacts it into a bolus.

Teeth

Two sets: Deciduous (primary) teeth - 20, Permanent teeth - 32
There are different types of teeth (incisors, canines, premolars, molars).

Pharynx

Structure: Shared passageway for air and food.
Function: Food travels from the mouth through the oropharynx and laryngopharynx to the esophagus. It aids in swallowing.

Esophagus

Structure: Muscular tube from the pharynx to the stomach.
Layers: Upper 1/3 – skeletal muscle, middle 1/3 - mixed, lower 1/3 - smooth muscle
Path: Posterior to the trachea, travels through the diaphragm before entering the stomach.
Function: Aids in swallowing.

Swallowing (Deglutition)

Total time: ~9 seconds.
Phases: Buccal, pharyngeal, esophageal.
Each phase, with specific steps, is discussed in detail.

Esophageal Sphincters

Function: Regulate the flow of food/liquid and prevents backflow or air entering wrong pathways
Pharyngoesophageal sphincter: Between the pharynx and esophagus - Prevents air from entering when food is not being swallowed.
Gastroesophageal sphincter: Between the esophagus and stomach – Controls the entry of food and prevents stomach acid backflow.

Stomach Functions

Storage: Large volume (50ml empty; 1000ml full), Chyme = partially digested food.
Movement: Peristalsis.
Secretion: Gastric juices.
Digestion: Mostly proteins and some carbohydrates.
Absorption: Alcohol and Aspirin.

Anatomy of the Stomach

Curvatures: Lesser (medial concave), Greater (lateral convex).
Parts: Cardia, Fundus, Body, Pylorus.
Muscle layers: Longitudinal, circular, oblique
Rugae: Folds in the stomach lining that allow expansion.
Pyloric Region: Funnel-shaped, continuous with the small intestine via the pyloric sphincter

Peristalsis

Mechanism: Waves of smooth muscle contractions.
Role: Mechanically breaks down food, and moves food to the small intestines.
Regulation: Controlled by factors including food volume, fluidity, fat, acid; stress.

Gastric Juices: Gastric Pits & Glands

Gastric Pits: Extension of epithelium into the lamina propria
Gastric Glands: Contain 4 types of cells that make gastric juices.

Stomach Cells (in Gastric pits)

Exocrine cells: Mucous cells (protective mucus), Chief cells (pepsinogen), Parietal cells (HCl and intrinsic factor).
Endocrine cells: G cells (gastrin), ECL cells (histamine), D cells (somatostatin).

Stomach: HCI Functions

Main functions: Activates pepsin for protein digestion, breaks down tough fibers, denatures proteins, kills bacteria.

The Stomach Mucosa and the Gastric Glands (Table)

Tables provide detailed information on the type of secretory cell, product secreted, stimuli for secretion, and its functions.

Regulation of Gastric Activity

Controls: CNS & ENS; hormones.
Phases: Cephalic, gastric, intestinal.

Cephalic Phase

Duration: Short (2-10 minutes).
Stimuli: Sight, smell, taste, or thoughts of food.
Response: Increased gastric juice production (approximately 500ml/hour), preparation of stomach to receive food. The vagus nerve (N X) plays a key role.

Gastric Phase

Duration: 2-4 hours.
Stimuli: Arrival of food (stretch & pH) leads to increased gastric juice production and stomach motility.
Response: The submucosal and myenteric plexuses signal to secretory cells/smooth muscle to prepare digestion.

Intestinal Phase

Function: Controls the rate of gastric emptying.
Stimuli: Food entering the duodenum—especially its duodenal stretch and pH (chemoreceptors).
Response: Release of hormonal signals that inhibit gastric motility/secretion.

Small Intestine Anatomy

Structure: Plicae circulares (circular ridges), Villi (finger-like projections), Microvilli (tiny projections on epithelial cells), located between the stomach and large intestine.

Three Regions of Small Intestine

Parts: Duodenum (first part-10 inches), Jejunum (middle part - 8 feet), Ileum (last part - 12 feet).
Duodenum: Chemical digestion (enzymes from pancreas, bile), Brunner's glands—alkaline mucus (neutralizes stomach acid).
Jejunum: Primary site of nutrient absorption.
Ileum: Major site of vitamin B12 absorption, returns bile salts to the liver.
Peyer's patches: MALT (mucosa-associated lymphatic tissue).

Small Intestine: Movement by Segmentation

Mechanism: Ring-like contractions using circular muscle, mixes and propels chyme.
Cycles: 9-12 cycles per minute; moves food completely through in 3-5 hours.

Small Intestine: Secretions

Hormones: Enterogastrones (inhibit stomach secretions, motility).
Examples: Cholecystokinin (CCK), Secretin, Gastric Inhibitory Polypeptide (GIP).

Small Intestine: Absorption

Passive diffusion: Fatty acids and triglycerides (after micelles delivery), Vitamins.
Active transport: H+ and Na+ actively transported by sodium-hydrogen antiporter. Water follow Na+

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Description

Test your knowledge of the human digestive system with this quiz. Covering topics from gastric emptying to nutrient absorption, this quiz assesses your understanding of key functions and structures involved in digestion. Perfect for students studying biology or health sciences!