Digestive System Structures and Functions

Comprehensive vocabulary flashcards covering the anatomy, secretions, and physiological processes of the human digestive system as detailed in the lesson transcript.

Alimentary Canal

A long muscular open tube, also called the digestive (Gastrointestinal) tract, that consists of a mouth at one end and an anus at the other.

Herbivore Digestive Tract

A longer digestive tract required because the cellulose in an animal's plant diet is harder to digest and requires more time.

Accessory Glands

Organs that secrete digestive juices through ducts into the canal, including the salivary glands, pancreas, liver, and gallbladder.

Peristalsis

Alternating waves of contraction and relaxation in the smooth muscles lining the canal that push food along, beginning in the throat and continuing through the esophagus, stomach, and intestines.

Sphincters

Ring-like valves formed by smooth muscle that close off the tract to regulate the passage of materials between compartments and prevent backflow.

Mechanical Digestion (Mouth)

The process where teeth cut ($incisors$, $canines$), smash, and grind ($molars$) food to increase surface area.

Salivary Amylase

An enzyme in saliva that helps break down starch (Amylose), a polysaccharide, into the disaccharide maltose by adding $H_2O$.

Bolus

A softened food mass created in the mouth that the tongue moves to the back of the pharynx for swallowing.

Uvula

A part of the soft palate that moves up and pushes against the back wall of the pharynx to seal off the nasal cavity during swallowing.

Epiglottis

A valve that closes the opening of the trachea (windpipe) during swallowing to prevent food from entering the lungs.

Lower Esophageal Sphincter

Also known as the Cardiac Sphincter, this ring of muscle at the entrance of the stomach normally stays closed to prevent acidic contents from backing up into the esophagus.

Rugae

Folds in the walls of the stomach that allow it to expand after a meal.

Gastric Juice

A secretion from gastric glands containing hydrochloric acid ($HCl$), salts, enzymes, water, and mucus.

Chyme

A liquid mixture created in the stomach when food is churned and mixed with gastric juices.

Pyloric Sphincter

A valve at the end of the stomach that controls the release of chyme into the small intestine.

Pepsin

An active enzyme that hydrolyzes proteins into smaller polypeptide chains; it is only activated when hydrochloric acid ($HCl$) is present.

Pepsinogen

The inactive form of the protein-digesting enzyme pepsin.

Parietal Cells

Cells lining the stomach that secrete hydrochloric acid ($HCl$).

Chief Cells

Cells lining the stomach that secrete pepsinogen.

Duodenum

The first region of the small intestine after the stomach which receives secretions from the pancreas and the gallbladder.

Villi

Tiny, finger-like projections on the folds of the small intestine, each covered with brush-like microvilli, to increase surface area for nutrient absorption.

Jejunum

The second region of the small intestine ($2.5\,m$) containing the most folds; it chemically breaks down nutrients so products can be absorbed into the bloodstream.

Ileum

The third region of the small intestine ($3\,m$) with fewer villi, responsible for absorbing nutrients and pushing undigested material into the large intestine.

Pancreatic Fluid

A secretion containing enzymes to digest macromolecules and bicarbonate, which changes the chyme pH from $1$ to a weakly basic $pH$ of $8$.

Bile

A greenish-yellow fluid mixture made by the liver containing bile pigments (waste) and bile salts (essential for fat digestion).

Bile Salts

Components of bile that act like detergent to physically break fat droplets into smaller droplets, increasing the surface area for enzymes to chemically break them down.