Digestion and Absorption

Flashcards covering key terms and concepts related to digestion and absorption, describing the functions of primary and accessory organs, mechanical and chemical processes, nutrient absorption pathways, and common gastrointestinal conditions discussed in the lecture.

Digestion

The process of breaking down food into smaller compounds, primarily occurring in the small intestine.

Absorption

The process where digested nutrients cross the lining of the intestine to enter the body’s circulatory system.

Gastrointestinal (GI) tract

A series of organs with outer layers of muscles and an inner mucosal layer of glands and absorptive cells where digestion occurs.

Primary Digestive Organs

The mouth, esophagus, stomach, small intestine, large intestine, and rectum.

Accessory Digestive Organs

The salivary glands, liver, pancreas, and gallbladder.

Transit Time

The period of time it takes food to travel the full length of the digestion tract.

Mechanical Digestion

Physical processes like chewing, grinding, mixing, and peristalsis that break down food.

Peristalsis

Wavelike muscular movements that move food progressively through the GI tract.

Chemical Digestion

The breakdown of large food compounds into smaller units for absorption through the action of secretions and enzymes.

Defecation

The elimination of undigested and unabsorbed substances from the body.

Five Primary Tastes

Sweet, Salty, Sour, Bitter, and Umami.

Saliva

Fluid added in the mouth that lubricates food and contains enzymes (like salivary amylase) to initiate chemical digestion.

Salivary Amylase

An enzyme released in the mouth that begins the chemical breakdown of carbohydrates.

Epiglottis

A flap that closes during swallowing to prevent food from entering the trachea (windpipe) and causing choking.

Bolus

A mass of food that has been chewed and mixed with saliva, ready to be swallowed and moved through the esophagus.

Sphincter

Circular muscles that separate organs of the GI tract, acting as 'one-way doors' to prevent food from flowing backward.

Lower Esophageal Sphincter (LES)

A sphincter located between the esophagus and the stomach that prevents the reflux of stomach contents.

Pyloric Sphincter

A sphincter that separates the stomach from the small intestine, controlling the timed release of chyme.

Ileocecal Valve

A sphincter that separates the ileum (small intestine) from the cecum (large intestine), preventing the reflux of waste.

Segmentation (Digestion)

Circular muscle contractions in the stomach and small intestine that churn and mix food (chyme).

Chyme

The semifluid mass of partially digested food and gastric juices that moves from the stomach to the small intestine.

Gastric Juices

Secretions produced in the stomach including hydrochloric acid, mucus, pepsinogen, and the hormone gastrin.

Mucus (Stomach)

A protective lining in the stomach that shields its cells from hydrochloric acid.

Hydrochloric Acid (HCl)

A component of gastric juice that denatures proteins, liquifies food, activates pepsin and lingual lipase, helps iron absorption, and neutralizes bacteria.

Intrinsic Factor

A substance secreted by the stomach lining that is essential for the absorption of Vitamin B12.

Pepsinogen

A proenzyme that converts to active pepsin by stomach acid to initiate protein digestion.

Gastrin

A hormone produced in the stomach that controls stomach movement and HCl secretion, and communicates with other digestive organs.

Small Intestine

The primary site of digestion and absorption, divided into the duodenum, jejunum, and ileum.

Duodenum

The first section of the small intestine where initial digestion and absorption begin.

Jejunum

The middle section of the small intestine where most digestion and absorption of macronutrients occur.

Ileum

The final section of the small intestine, involved in the absorption of lipids, fat-soluble vitamins, and Vitamin B12.

Pancreas

An accessory organ that secretes alkaline bicarbonate to neutralize acidic chyme and enzymes that act on macronutrients (carbohydrates, fats, proteins).

Liver

An accessory organ that produces bile, which is crucial for fat digestion.

Gallbladder

An accessory organ that stores and releases bile into the small intestine to assist in the digestion of fats.

Pancreatic Juice

Contains bicarbonate to neutralize gastric juices and powerful enzymes (amylase, lipase, proteases) to break down carbohydrate, fat, and protein.

Bile

A digestive fluid produced by the liver and stored in the gallbladder, which emulsifies fat, allowing digestive enzymes to access and break it down.

Villi

Small, finger-like projections on the lining of the small intestine that greatly increase the surface area available for nutrient absorption.

Microvilli

Tiny, hair-like projections extending from each villus into the lumen of the small intestine, further increasing surface area and secreting digestive enzymes.

Crypts

Crevices located between the villi in the small intestine, containing cells that secrete fluid and new cells.

Goblet Cells

Specialized cells in the small intestine that secrete mucus to protect the intestinal wall.

Capillaries

Tiny blood vessels within the villi that absorb water-soluble nutrients from the intestinal wall and carry them directly to the liver.

Lacteals

Lymphatic vessels located within the villi that absorb fat and fat-soluble substances, transporting them through the lymph system.

Chylomicron

A lipoprotein formed within intestinal cells from longer chain fatty acids and glycerol, which enters the lacteals and lymphatic system.

Micelle

A small lipid-bile salt complex formed from monoglycerides and fatty acids, facilitating their transport to the surface of the villi for absorption.

Large Intestine

A 5-foot long organ primarily involved in propulsion, absorption of water and sodium, and preparation of waste for defecation.

Gut Microbiota

The community of bacteria, viruses, fungi, archaea, and other microorganisms residing in the large intestine, which produce vitamins, ferment fibers, and metabolize remaining nutrients.

Prebiotics

Non-digestible carbohydrate sources that act as food for beneficial microbes (probiotics) in the large intestine, supporting their metabolism and increasing their density.

Probiotics

Live microorganisms that, when consumed in adequate amounts, can have a beneficial effect on health, often found in foods like yogurt and kefir.

Synbiotics

A combination of both prebiotics and probiotics, designed to work together for enhanced digestive health benefits.

Choking

A condition where food accidentally enters and blocks the trachea, obstructing the air passageway and preventing breathing.

Constipation

A common digestive problem characterized by infrequent or difficult bowel movements, often improved with increased fiber, water, and exercise.

Diverticulosis

A condition involving the formation of small, bulging pouches (diverticula) in the weakened areas of the intestinal lining, most commonly in the colon.

Gastroesophageal Reflux (GERD)

Also known as heartburn, it is the pain resulting from stomach acid backing up into the esophagus.

Peptic Ulcer Disease

A lesion or sore in the lining of the stomach or the duodenum of the small intestine, most commonly caused by a Heliobacter pylori (H. pylori) bacterial infection or NSAID use.

Heliobacter pylori (H. pylori)

The most common bacterial cause of peptic ulcer disease.