Digestive system

What structures make up the digestive system?

The gastrointestinal tract: mouth, pharynx, esophagus, stomach, small intestine, large intestine, rectum, anus. Accessory organs: salivary glands, liver, gall bladder, pancreas.

What is the GI tract?

A continuous, hollow, muscular tube that runs from mouth to anus.

What is another name for the GI tract?

The alimentary canal.

What is the lumen?

The space inside the GI tube.

What are the main functions of the digestive system?

Ingestion, mechanical digestion, chemical/enzymatic digestion, absorption, and excretion.

What is ingestion?

Intake of food into the alimentary canal.

What is mechanical digestion?

Physical breakdown of food through chewing and mixing.

What is chemical/enzymatic digestion?

Breakdown of food using digestive enzymes, hormones, bile, acid, and mucus.

What is absorption?

Movement of nutrients and water into blood or lymph vessels.

What is excretion?

Elimination of undigested material as feces.

What structures are part of the alimentary canal?

Mouth, pharynx, esophagus, stomach, small intestine, large intestine, rectum, anus.

What are the functions of the oral cavity?

Ingestion, mechanical digestion, enzymatic digestion.

What structures are found in the oral cavity?

Hard and soft palates, uvula, lips/labia, gingiva, vestibule, teeth, tongue.

What is the function of teeth?

Bite and chew food; tear, grind, and break down food mechanically.

What are the types of teeth?

Incisors, canines, premolars, molars.

What are the functions of the tongue?

Mechanical digestion, taste, speech, secretion of lingual lipase, manipulation of food.

What is a muscular hydrostat?

A structure like the tongue that manipulates food using muscle fibers.

What are the regions of a tooth?

Crown, neck, root.

What covers dentin?

Enamel.

What is special about enamel?

It is the hardest biological substance on earth.

What lies beneath dentin?

The pulp cavity.

What anchors the root of the tooth?

Cementum.

What are the three salivary glands?

Parotid, submandibular, and sublingual glands.

What enzyme is found in saliva and what does it digest?

Salivary amylase; digests starch.

What enzyme does the tongue secrete and what does it digest?

Lingual lipase; digests lipids.

What is food called after chewing and chemical digestion in the mouth?

A bolus.

What are the two regions of the pharynx involved in digestion?

Oropharynx and laryngopharynx.

What prevents food from entering the trachea?

The epiglottis.

What is peristalsis?

Rhythmic contraction of smooth muscle that moves the bolus through the esophagus.

What are the functions of the stomach?

Food storage, enzymatic digestion, mechanical digestion.

What are the four regions of the stomach?

Cardia, fundus, body, pylorus.

How many muscle layers does the stomach have?

Three: outer longitudinal, inner circular, innermost oblique.

What is the lesser curvature?

The inner curvature of the stomach where the lesser omentum attaches.

What is the greater curvature?

The outer curvature of the stomach where the greater omentum hangs.

What are rugae?

Folds of tissue that expand to increase stomach volume.

What does the lower esophageal sphincter do?

Prevents backflow of stomach acid into the esophagus.

What does the pyloric sphincter do?

Controls when food passes into the small intestine.

What do parietal cells secrete?

Hydrochloric acid (HCl), which creates a low pH and activates pepsin.

What do chief cells secrete?

Pepsinogen, which becomes pepsin to digest proteins.

What do mucus cells secrete?

Mucus that protects the stomach lining from acid and prevents ulcers.

How long does it take for the stomach to release its contents into the small intestine?

About 2–6 hours.

What is food called once it leaves the stomach and enters the small intestine?

Chyme.

What are the functions of the small intestine?

Enzymatic digestion and absorption.

What are the three regions of the small intestine?

Duodenum, jejunum, ileum.

How long is the duodenum and what is its function?

About 1 foot long; secretes mucus to neutralize acidic chyme.

What is the primary function of the jejunum?

Most nutrient absorption occurs here.

How long is the ileum and what is its function?

About 11.5 feet long; contains many immune structures.

What are brush border enzymes?

Enzymes on the surface of the small intestine that break chyme into small subunits for absorption.

What is absorption in the small intestine?

Movement of nutrients from the lumen into the bloodstream.

What are villi?

Folds in the small intestine that increase surface area for absorption; abundant in the jejunum.

What are microvilli?

Projections on villi that further increase surface area.

What are Peyer’s patches?

Immune structures in the small intestine; abundant in the ileum.

What are lacteals?

Specialized lymphatic vessels that absorb large lipids.

What are the main functions of the large intestine?

Absorption of water and elimination of waste.

What are the regions of the large intestine?

Cecum, ascending colon, transverse colon, descending colon, sigmoid colon, rectum, anus.

What is the ileocecal valve?

A flap that separates the ileum from the cecum.

What is the function of the appendix?

Immunity.

What is the right colic flexure also called?

The hepatic flexure.

What is the left colic flexure also called?

The splenic flexure.

What is the sigmoid colon?

The S-shaped region of the large intestine.

What are accessory organs of the digestive system?

Organs that contribute to digestion but are not part of the alimentary canal.

What is the exocrine function of the pancreas?

Secretes digestive enzymes into the main pancreatic duct, which empties into the duodenum.

What enzymes do pancreatic acinar cells secrete?

Proteases (proteins), pancreatic amylase (carbohydrates), pancreatic lipase (lipids), pancreatic nucleases (nucleic acids).

Where do pancreatic enzymes enter the small intestine?

At the major duodenal papilla.

What is bile?

A detergent-like substance that emulsifies fats for absorption.

What organ synthesizes bile?

The liver.

What organ stores bile?

The gall bladder.

What triggers the release of bile from the gall bladder?

The hormone CCK, released in response to a fatty meal.

Where do the liver and gall bladder ducts merge?

The common bile duct.

What ducts drain the liver?

The right and left hepatic ducts.

What duct carries bile from the liver?

The common hepatic duct.

What duct carries bile from the gall bladder?

The cystic duct.

What duct delivers bile into the duodenum?

The common bile duct.

Where does the common bile duct empty?

The major duodenal papilla.