Digestion Final

What is digestion?

The process by which food substances are broken down into forms that can be absorbed through cell membranes.

What are the six processes of digestion?

Ingestion, propulsion, mechanical breakdown, chemical digestion, absorption, and defecation.

What is ingestion?

Taking food into the mouth.

What is propulsion?

Movement of food through the alimentary canal by swallowing and peristalsis.

What is mechanical breakdown?

Physical breakdown of food into smaller particles.

What is chemical digestion?

Chemical breakdown of food by enzymes and other chemicals.

What is absorption?

Movement of digestive products through cell membranes into the body.

What is defecation?

Elimination of indigestible materials.

What are the two major components of the digestive system?

The alimentary canal and accessory organs.

What is the alimentary canal?

A continuous tube extending from the mouth to the anus.

What are accessory digestive organs?

Organs that release secretions into the alimentary canal.

What is the approximate length of the alimentary canal?

Approximately 9 meters.

What structure accounts for most of the length of the alimentary canal?

The small intestine.

What are the four layers of the alimentary canal wall?

Mucosa, submucosa, muscularis, and serosa.

What is the innermost layer of the alimentary canal?

Mucosa

What are the functions of the mucosa?

Secretion and absorption.

Why does the mucosa contain folds?

To increase surface area for absorption.

What type of structures may be found in the mucosa?

Glands and tubular invaginations.

What is the submucosa?

A connective tissue layer containing blood vessels, lymphatic vessels, glands, and nerves.

What is the function of the submucosa?

Provides nourishment and carries away absorbed materials.

What is the muscularis?

A layer of smooth muscle responsible for movement of food through the digestive tract.

What are the two muscle layers of the muscularis?

Inner circular layer and outer longitudinal layer.

What happens when the inner circular muscle contracts?

The diameter of the lumen decreases.

What happens when the outer longitudinal muscle contracts?

The tube shortens.

How many muscle layers does the stomach muscularis contain?

Three layers: oblique, circular, and longitudinal.

What is the serosa?

An outer serous membrane that produces lubricating fluid.

What is the function of serous fluid?

Allows digestive organs to slide freely against each other.

What is the serosa called in the abdominal cavity?

Visceral peritoneum.

What is the outer layer of the esophagus called?

Adventitia.

What are the two major movements of the digestive tube?

Mixing and propulsion.

What is mixing?

Contractions of small sections of smooth muscle that mix food with digestive juices.

What is another name for mixing movements?

Segmentation.

What is propulsion?

Movement of food through the digestive tract by peristalsis.

What is peristalsis?

A wave-like contraction of smooth muscle that pushes food forward.

What happens during peristalsis?

A ring of contraction moves food into a relaxed area of the digestive tract.

What are the accessory organs of digestion?

Salivary glands, liver, gallbladder, and pancreas.

What are the functions of the mouth in digestion?

Receives food, begins mechanical digestion, and mixes food with saliva.

What are the associated structures of the mouth?

Cheeks, lips, tongue, palate, and teeth.

What is the function of the lips?

Sense food temperature.

What is the function of the cheeks?

Hold food and assist chewing.

What is the function of the tongue?

Mixes food with saliva and moves food toward the oropharynx.

What do tongue papillae contain?

Taste buds and structures that provide friction for handling food.

What is the function of the palate?

Forms the roof of the oral cavity.

What happens to the soft palate and uvula during swallowing?

They rise upward to block the nasal passage.

What is the function of teeth?

Mechanical breakdown of food.

What are the two sets of teeth?

Primary (deciduous) and secondary (permanent).

What do salivary glands secrete?

Saliva and mucus.

What enzyme is found in saliva?

Salivary amylase.

What does salivary amylase digest?

Starch into simple sugars.

Where does carbohydrate digestion begin?

The mouth.

What antibacterial enzyme is found in saliva?

Lysozyme.

What is the function of mucus in saliva?

Binds food together and lubricates it.

What are the three major pairs of salivary glands?

Parotid, submandibular, and sublingual glands.

Which salivary gland is mostly made of serous cells?

Parotid gland.

Which salivary gland contains both serous and mucous cells?

Submandibular gland.

Which salivary gland is mostly made of mucous cells?

Sublingual gland.

What nervous system division stimulates salivation?

Parasympathetic nervous system.

Why does thinking about food increase saliva production?

Parasympathetic impulses stimulate salivary glands.

What are the three regions of the pharynx?

Nasopharynx, oropharynx, and laryngopharynx.

What passes through the nasopharynx?

Air only.

What type of epithelium lines the nasopharynx?

Pseudostratified ciliated columnar epithelium.

What passes through the oropharynx?

Food and air.

What type of epithelium lines the oropharynx?

Stratified squamous epithelium.

What tonsils are located in the oropharynx?

Palatine and lingual tonsils.

What passes through the laryngopharynx?

Food and air.

What type of epithelium lines the laryngopharynx?

Stratified squamous epithelium.

What is swallowing also called?

Deglutition.

What are the two stages of swallowing?

Buccal phase and pharyngeal-esophageal stage.

Is the buccal phase voluntary or involuntary?

Voluntary

What happens during the buccal phase?

Food is chewed, mixed with saliva, formed into a bolus, and pushed into the oropharynx.

Is the pharyngeal-esophageal stage voluntary or involuntary?

Involuntary.

What triggers the swallow reflex?

Receptors detecting food in the pharyngeal opening.

What happens to the soft palate and uvula during swallowing?

They rise to prevent food from entering the nasal cavity.

What happens to the epiglottis during swallowing?

It folds downward to block the respiratory pathway.

What happens to the esophagus during swallowing?

It opens and receives the food bolus.

How does food move through the esophagus?

By peristaltic waves.

What is the esophagus?

A muscular tube connecting the laryngopharynx to the stomach.

What is the length of the esophagus?

Approximately 25 cm.

What type of epithelium lines the esophagus?

Stratified squamous epithelium.

Why does the esophagus contain mucus glands?

To lubricate food movement.

What is the esophageal hiatus?

The opening in the diaphragm where the esophagus passes through.

What is a hiatal hernia?

A condition where part of the stomach protrudes through the esophageal hiatus.

What is the gastroesophageal sphincter?

A circular smooth muscle valve between the esophagus and stomach.

What is the function of the gastroesophageal sphincter?

Prevents backflow of stomach contents into the esophagus.

What is the shape and location of the stomach?

The stomach is a J-shaped pouch-like organ located in the upper left portion of the abdominal cavity.

What are the functions of the stomach?

Receives food, mixes food with gastric juice, begins protein digestion, performs limited absorption, and sends food to the duodenum.

What are the four regions of the stomach?

Cardiac region, fundic region, body, and pyloric region.

What is the function of the pyloric sphincter?

Prevents backflow of material from the duodenum into the stomach.

What are rugae?

Folds of the stomach mucosa and submucosa that increase surface area and allow expansion.

What are gastric glands?

Secretory glands in the stomach that produce digestive substances.

What are the four types of secretory cells in gastric glands?

Mucous cells, parietal cells, chief cells, and enteroendocrine cells.

What do mucous cells in the stomach secrete?

Thin acidic mucus.

Where are mucous cells located in gastric glands?

The neck of the gastric gland.

What do parietal cells secrete?

Hydrochloric acid (HCl) and intrinsic factor.

What is the pH of stomach acid?

Approximately pH 2.

What is the function of hydrochloric acid in the stomach?

Activates pepsinogen into pepsin and creates an acidic environment for digestion.

What is the function of intrinsic factor?

Allows absorption of vitamin B12.

What do chief cells secrete?

Pepsinogen.

What does pepsin digest?

Proteins

Where does protein digestion begin?

The stomach.