NutritionIntroduction to the Gastrointestinal System and Digestion

Vocabulary flashcards covering the body organization, digestive hormones, GI tract anatomy, digestive enzymes, accessory organs, and cellular energy production based on the lecture transcript.

Atom

The smallest unit of matter.

Molecule

A group of atoms bonded in specific configurations, such as $H_2O$.

Cell

The smallest unit of life, encased within a cell membrane.

Cell membrane

The outer layer of a cell composed of two layers of phospholipids, featuring hydrophilic heads and hydrophobic tails.

Tissue

A group of cells that work together to perform a particular function.

Organ

A sophisticated organization of tissue that comes together for a particular function in the body.

Organ system

A group of organs that work together for a common purpose, such as the gastrointestinal system.

Cephalic phase of digestion

The earliest phase of digestion in which the brain signals digestive organs to prepare the body to take in food.

Hormones

Specialized chemical messengers produced in specific glands and secreted into the bloodstream to target organs throughout the body.

Hypothalamus

The region at the center of the brain that prompts an individual to seek food.

Ghrelin

A hormone that sends signals to the brain to stimulate hunger.

Cholecystokinin (CCK)

A hormone that produces a feeling of satiety, signaling to the brain that food intake is sufficient.

Leptin

A satiety hormone that signals to the brain that the stomach is full or approaching fullness.

Satiety

The feeling of fullness after eating.

Gastrointestinal (GI) tract

A series of organs connected in a long tube through the body, extending from the mouth to the anus, that functions to digest and absorb food.

Sphincters

Tight rings of muscle that control the passage of food from one part of the GI tract to another.

Mechanical digestion

The physical breaking down and mixing of food, such as chewing or muscular contractions in the stomach.

Chemical digestion

The enzymatic and acidic process of altering the chemical composition of food to break complex molecules into absorbable units.

Salivary amylase

An enzyme produced in the salivary glands that initiates the chemical digestion of carbohydrates in the mouth.

Bolus

A mass of chewed food mixed with saliva created in the mouth prior to swallowing.

Peristalsis

Wave-like muscular contractions throughout the GI tract that propel food forward.

Epiglottis

A small organ that covers the opening of the trachea during swallowing to prevent food and drink from entering the lungs.

Gastroesophageal sphincter

The sphincter located at the base of the esophagus that separates the esophagus from the stomach.

Hydrochloric acid

A highly acidic component of gastric juice that denatures proteins and activates the enzyme pepsin in the stomach.

Pepsin

A protein-digesting enzyme in the stomach that is activated by hydrochloric acid.

Intrinsic factor

A substance contained in gastric juice that is essential for the digestion of vitamin B12.

Gastric lipase

A lipid-digesting enzyme produced in the stomach to break down fats.

Chyme

A semi-fluid mixture of gastric juices and partially digested food produced in the stomach.

Pyloric sphincter

The sphincter that separates the stomach from the small intestine.

Small intestine

The primary organ of nutrient absorption, consisting of three main sections: the duodenum, jejunum, and ileum.

Duodenum

The first section of the small intestine.

Jejunum

The middle section of the small intestine.

Ileum

The third and final section of the small intestine.

Villi

Finger-like projections lining the small intestine that increase surface area for nutrient absorption.

Enterocytes

Specialized absorptive intestinal cells located on the villi throughout the small intestine.

Brush border

The absorptive surface of the small intestine composed of microvilli.

Microvilli

Microscopic projections that make up the brush border to maximize intestinal surface area.

Large intestine (Colon)

The organ that receives undigested food material, absorbs excess water, and stores waste for 12 to 24 hours prior to elimination.

Ileocecal valve

The valve connecting the ileum of the small intestine to the cecum of the large intestine.

Accessory organs

Organs outside the GI tract tube—including the salivary glands, liver, gallbladder, and pancreas—that assist in digestion.

Bile

A digestive fluid produced by the liver and stored in the gallbladder that emulsifies fats in the small intestine.

Gallbladder

An accessory organ that stores bile and secretes it into the small intestine.

Pancreas

An accessory organ that produces digestive enzymes and bicarbonate to neutralize acidic chyme entering the small intestine.

Lipase

An enzyme responsible for breaking down lipids or fats.

Amylase

An enzyme responsible for breaking down carbohydrates.

Protease

An enzyme responsible for breaking down proteins.

Krebs cycle (Citric acid cycle)

A series of cyclical chemical reactions taking place within the mitochondria of cells that converts food nutrients into usable cellular energy.

Acetyl coenzyme A (acetyl CoA)

A molecule that enters the Krebs cycle and combines with other compounds to start energy-yielding cellular respiration reactions.

Adenosine triphosphate (ATP)

The major energy-providing currency of the body produced during cellular respiration.