Digestive System

Describe the difference between mechanical and chemical digestion.

Mechanical digestion uses physical processes like chewing and stomach churning; chemical digestion uses enzymes to break food into building blocks.

What does ingestion mean?

Taking food and nutrients into the body.

What does excretion mean?

Elimination of feces.

List the organs of the digestive tract in order.

Mouth → Pharynx → Esophagus → Stomach → Small intestine → Large intestine → Anal canal.

List the accessory organs of digestion.

Teeth/tongue; Salivary glands; Liver; Gallbladder; Pancreas.

When is the term bolus used?

When food is swallowed and enters the esophagus.

When is the term chyme used?

When partially digested food mixes with gastric juices in the stomach.

When is the term feces used?

When waste enters the large intestine and exits the body.

Which body cavity contains most digestive organs?

Peritoneal (abdominal) cavity.

What are mesenteries?

Sheets of peritoneal membrane that stabilize digestive organs.

What does the lesser omentum stabilize?

Stomach.

Where is the greater omentum located?

Hangs across the anterior abdomen.

What are the four layers of the digestive tract?

Mucosa, submucosa, muscularis externa, serosa.

Which layer is closest to the lumen?

Mucosa.

What is the lamina propria?

Areolar connective tissue of the mucosa.

What is the muscularis mucosae?

Smooth muscle layer within mucosa.

Which layer contains glands, blood vessels, lymph vessels?

Submucosa.

Where is the submucosal plexus located?

Submucosa.

Where is the myenteric plexus located?

Muscularis externa.

What does the serosa secrete?

Serous fluid.

What epithelium is in the esophagus?

Stratified squamous.

What epithelium is in the stomach and small intestine?

Simple columnar.

What epithelial change occurs in the large intestine?

Simple columnar with many goblet cells.

Which layer has no major modifications along the tract?

Submucosa.

How is the muscularis externa modified in the esophagus?

Skeletal → smooth muscle.

How is the muscularis externa modified in the stomach?

Has an extra oblique layer.

Which layer is absent in the esophagus?

Serosa.

What movement propels food?

Peristalsis.

What movement mixes food?

Segmentation and churning.

Does the tongue perform mechanical or chemical digestion?

Both.

What enzyme does the tongue produce?

Lingual lipase.

What nutrient does lingual lipase digest?

Lipids.

What is the function of the hard palate?

Helps compress food.

What is the function of the uvula?

Prevents premature swallowing.

Which salivary glands produce amylase?

Parotid and submandibular.

What does salivary amylase digest?

Carbohydrates.

Which salivary gland produces the least saliva?

Sublingual (mostly mucus).

Which salivary gland produces the most saliva?

Submandibular (50/50 mix).

Which salivary gland is largest?

Parotid.

Do teeth perform mechanical or chemical digestion?

Mechanical.

What do incisors do?

Cut food.

What do cuspids do?

Tear food.

What do molars and premolars do?

Grind food.

True or false: Food and air pass through the pharynx.

True.

What is the function of the esophageal sphincter?

Prevents acid reflux.

Which swallowing phase is voluntary?

Buccal.

Which phase triggers the reflex?

Pharyngeal.

Which phase uses peristalsis?

Esophageal.

What is the function of rugae?

Allow stomach expansion.

What extra muscle layer does the stomach have?

Oblique; helps churning.

Which cell secretes pepsinogen?

Chief cells.

What is pepsinogen?

Inactive form of pepsin.

Which cell secretes mucus?

Mucous cells.

Which cell secretes gastrin?

G cells.

What is gastrin's function?

Stimulates gastric activity.

Which cell secretes intrinsic factor?

Parietal cells.

What is intrinsic factor’s function?

Allows vitamin B12 absorption.

Which cell secretes HCl?

Parietal cells.

What is HCl’s function?

Activates pepsinogen and provides acidity.

What % of nutrients are absorbed in the small intestine?

90%.

Which part is the "mixing bowl"?

Duodenum.

Where does most digestion and absorption occur?

Jejunum.

What is the last part of the small intestine?

Ileum.

What structures increase surface area?

Plicae and villi.

What is the lymphatic vessel in villi?

Lacteal.

What do intestinal glands produce?

Brush-border enzymes.

Endocrine pancreas cells and what they produce?

Pancreatic islets → insulin and glucagon.

Exocrine pancreas cells and what they produce?

Acinar cells → pancreatic juice.

True/false: Pancreatic juice digests all nutrients.

True.

What is the basic unit of the liver?

Liver lobule.

What are liver cells?

Hepatocytes.

What are liver capillaries?

Sinusoids.

What 3 structures are in the portal triad?

Branch of hepatic artery, portal vein, and bile duct.

What is the function of the gallbladder?

Stores bile.

Functions of large intestine?

Absorb water/vitamins; form feces; store feces.

How is ileum attached to cecum?

Ileocecal valve.

List the three sections of the large intestine.

Cecum, colon, rectum.

Which section contains appendix?

Cecum.

Which section contains anus?

Rectum → anal canal → anus.

Which section contains haustra and taeniae coli?

Colon.

List the four sections of the colon.

Ascending, transverse, descending, sigmoid.

What are mass movements?

Strong peristaltic waves.

Which anal sphincter is voluntary?

External.

Which sphincter is involuntary?

Internal.

What do carbs break into?

Monosaccharides.

What do proteins break into?

Amino acids.

What do lipids break into?

Fatty acids.

What provides mechanical digestion in the mouth?

Mastication.

What provides mechanical digestion in the stomach?

Churning.

What provides mechanical digestion in the intestine?

Segmentation.

What enzyme digests carbs in the mouth?

Salivary amylase.

What enzyme digests lipids in the mouth?

Lingual lipase.

What happens to salivary amylase in the stomach?

Inactivated.

What happens to lingual lipase in the stomach?

Remains active.

How is pepsinogen activated?

HCl converts it to pepsin.

What does pepsin digest?

Proteins.

Two carb-digesting enzymes in small intestine?

Pancreatic amylase + brush-border enzymes.

Two lipid-digesting agents?

Pancreatic lipase + bile.

Two protein-digesting enzymes?

Pancreatic proteases + brush-border enzymes.

Why must lipids be emulsified?

Increases surface area.