Anatomy Lecture Exam #3

What is the digestive tract (alimentary canal)?

A continuous tube that runs from the mouth to the anus

What makes the digestive system unique compared to other body systems?

It is the ONLY system open to the external environment at both ends.

What structures are included in the mouth?

Teeth, tongue, hard palate, soft palate.

Where is the mouth located?

Anterior to the pharynx

What is the function of the mouth?

It is the first site of digestion

What type of mechanical digestion occurs in the mouth?

Chewing (mastication)

What type of chemical digestion occurs in the mouth?

Saliva begins carbohydrate digestion

What enzyme is in saliva and what does it do?

Salivary amylase; it begins breaking down carbohydrates (starches)

What is the esophagus?

A long, muscular tube connecting the mouth to the stomach

What is a bolus?

A mass of chewed food

What is peristalsis?

Involuntary wave-like contractions of smooth muscle that move food.

What is a sphincter?

A circular muscle that opens (relaxes) and closes (contracts)

What is the function of the lower esophageal sphincter (LES)?

Prevents stomach acid from flowing backward

What causes when the LES weakens?

It causes heartburn

What is the function of the stomach?

Stores and digests food

What are rugae?

Gastric folds in the stomach

What are the functions of rugae?

Allow expansion, increase surface area, and aid in mechanical digestion

What do gastric glans in the stomach contain?

Parietal cells that release HCL

What type of mechanical digestion occurs in the stomach?

Churning

What type of chemical digestion occurs in the stomach?

Gastric juices

What is the HCl and what is its pH?

Hydrochloric acid; pH is about 2 (very acidic)

What additional function does HCl have?

Kills bacteria

What enzyme in the stomach breaks down proteins?

Pepsin

What is chyme?

A thick liquid formed from digested food

How long does it take for food to become chyme?

About 30-45 min after eating

What does the pyloric sphincter do?

Regulates emptying into small intestine

What is the primary function of the small intestine?

Digestion and absorption

What are the 3 parts of the small intestine?

Duodenum, Jejunum, ileum

What happens in the duodenum?

Major cite of chemical digestion

What does the duodenum receive?

Chyme, bile, and pancreatic enzymes

What is the function of the jejunum?

Main site of nutrient absorption

What is the function of ileum?

Final absorption

What valve connects the small intestine to the large intestine?

ileocecal valve

What is the function of the large intestine?

Absorbs water and forms/stores feces

What structures are included in the large intestine?

Cecum (with appendix) and colon

What are the four parts of the colon?

Ascending, transverse, descending, sigmoid

How is large intestine different from the small intestine structurally?

It is shorter but wider in diameter

What additional functions does the large intestine have?

Extracts remaining nutrients and absorbs electrolytes

What is the function of the rectum?

Stores feces

What is the difference between internal and external anal sphincters?

Internal = Involuntary, External = Voluntary

What are the accessory organs?

Organs that aid digestion but are not part of the digestive tract

What are the 6 accessory organs?

Liver, Gallbladder, Pancreas, Salivary glands, Teeth, Tongue

What does the liver produce?

Bile

What is bile and what does it do?

Alkaline substance that emulsifies fats

What does the gallbladder do?

Stores and concentrates bile and releases it into the small intestine

What does the pancreas release?

Digestive enzymes and bicarbonate

What is the function of bicarbonate?

Neutralizes stomach acid

What do salivary glands produce?

Saliva

What is the role of teeth?

Mechanical digestion

What is the role of the tongue?

Moves food, forms bolus, aids swallowing

What are the 6 phases of digestion?

Ingestion, propulsion, mechanical digestion, chemical digestion, absorption, defecation

What is ingestion?

Taking in food

What is propulsion?

Movement of food (swallowing + peristalsis)

What is mechanical digestion?

Physical breakdown of food

What is chemical digestion?

Enzymes breaking food into nutrients

What is absorption?

Nutrients entering the bloodstream

Where does absorption occur?

Small intestine

What is defecation?

Elimination of waste

What is the cephalic phase?

“Thinking about food” phase before eating

What triggers the cephalic phase?

Sight, smell, taste, or thought of food

What happens during the cephalic phase?

Brain signals stomach to release acid and enzymes

What is the gastric phase?

Begins when food enters the stomach

What happens during the gastric phase?

Stomach expands and releases more gastric juices

What is the intestinal phase?

Begins when cyme enters the small intestine

What happens during the intestinal phase?

Small intestine regulates chyme entry and slows stomach activity