• Absorption – the process by which nutrients from digested food move from the gut into the body and how cells exchange nutrients and water with the blood stream
• Absorption, Passive – osmosis, a selective diffusion process [see Osmosis]
• Active Transport – requires energy and a specific carrier molecule
• Adenosine Triphosphate (ATP) – a chemical synthesized by the mitochondria in cells to produce energy
• Amino Acids – the 'building blocks' of protein; protein is constructed of chains of amino acids which are folded into complex arrangements
• Artery – a blood vessel which carries oxygenated blood away from the heart
• Arteriole – the smallest division of the arteries
• ATP - [see Adenosine Triphosphate]
• Bacterial Translocation – gut bacteria or their by-products moving across the gut wall barrier into circulation
• Barrier Function – active function of the gut wall which protects and limits access to the inner body
• Bile – a digestive juice secreted by the liver and stored in the gall bladder; bile emulsifies fats [see Emulsify]
• Brush Border – an apt term for an epithelial surface covered with microvilli [see Epithelium and Microvilli]
• Carnivore, Carnivorous – eats mainly animals, not plants
• Cecum – a blind pouch at the beginning of the large intestine
• Central Nervous System – the brain and spinal cord
• Cholagogue – a drug or other substance which promotes the discharge of bile from the gall bladder, purging it downward
• Chyle – milky mix of emulsified dietary fat and lymph [see Bile, Emulsify, and Lymph]
• Chyme – thick semifluid mass of partly digested food made in the stomach
• Circulatory System – a system for delivery and pick-up
• CNS - see Central Nervous System
• Colon – a term for the large bowel or large intestine
• Detoxify - to remove or to make safe, said of chemicals and poisons
• Diffusion, Facilitated – diffusion requiring a carrier but not usually an energy source
• Diffusion, Passive – movement of molecules or ions from an area of high concentration to an area of lower concentration
• Digestion – the processes, both mechanical and chemical, by which food is broken down into absorbable form [see Absorption]
• Digestive System – the digestive tract plus the internal organs of pancreas, liver and gall bladder [see Digestive Tract]
• Digestive Tract – a complex specialized tube running from mouth to anus; the outside-the-inner-body part of the Digestive System
• Duct – a tubular channel used to deliver a secretion or substance
• Duodenum – the first section of the small intestine where the chyme is neutralized by buffers from the pancreas and bile delivered from the gall bladder
• Electrolytes – dissolved ions, usually of minerals, that conduct electrical impulses which facilitate movement in and out of cells
• Emulsify – to create a suspension of two substances, like oil and water, that would normally not mix
• Endocrine – glands in the body, such as the thyroid, pituatary, pancreas, which secrete hormones directly into the blood stream to give orders and directions elsewhere
• Endocrinopathic – trouble in the endocrine gland system, too much hormone production, too little hormone production [see Hormone]
• Endocytosis – absorption by engulfing [see Pinocytosis and Phagocytosis]
• ENS – [see Enteric Nervous System]
• Enteric Nervous System – a subdivision of the Peripheral Nervous System that directly controls the gastrointestinal system
• Enzymes - biomolecules constructed of amino acids that speed up biochemical reactions without changing in the process
• Epithelium – tissue which covers a surface or lines an organ and is composed of cells which secrete or transport or regulate; the skin (epidermis) is one form of epithelium
• Feces – see Poop
• Fermentable Fiber – fiber which the gut bacteria can utilize
• Fiber – undigestible/nonabsorbable leftovers from plant digestion consisting of
mainly complex sugar molecules
• Fiber, Dietary – fiber naturally present in food ingredients
• Fiber, Functional – fiber added to food items
• Fiber, Soluble – fiber which can dissolve in water
• Fiber, Insoluble – fiber which does not dissolve in water
• Gall Bladder - storage organ for bile synthesized in the liver
• Gastric Acid – a very acidic solution composed mainly of hydrochloric acid secreted into the stomach by special glands
• Gland – A cell or group of cells or organ that produces a secretion for use elsewhere
• Goblet Cells – specialized cells whose sole function is to secrete mucin which dissolves in water to form mucous (see Mucous)
• Gut Bacteria – microscopic organisms living in the bowel in numbers which outnumber the cells of the body
• Hematochezia – visible bright red blood on the stool [see Melena]
• Hepatic – of the liver, involving the liver
• Hormone – a chemical which controls and regulates the activity of certain cells or organs
• Ileocecal Valve – the valve between the small intestine and the
large intestine (see Sphincter)
• Ileum – last section of the small intestine where absorption of Vitamin B12 and resorption of bile salts occurs and whose wall contains an abundance of Peyer's Patches
• ICC – [see Interstitial Cells of Cajal]
• Infection – inflammation in response to foreign invasion by bacteria or other invasive organisms (see Inflammation and Pus)
• Inflammation – the body's innate and initial response to injury or other troubles characterized by pain, heat, redness, swelling and possible impairment of function (see Pus and Infection)
• Interstitial Cells of Cajal – cells in the wall of the gut that act as pacemakers for movement contractions, that set the pace of action
• Interstitial Fluid – the body's fluid outside the blood vessels
• Involuntary – not under one's own control
• Jujenum – longest and middle section of the small intestine where most absorption of nutrients occurs
• Lacteal – the chyle collecting vessel in the middle of each villus [see Chyle and Villi/Villus}
• Laxative – a food or drug that facilitates pooping
• Leukocytes – white blood cells
• Lumen – the interior space of a tubular organ such as an intestine or blood vessel
• Lymph – interstitial fluid once that fluid has moved into the lymph system [see Interstitial Fluid]
• Melena – occult or hidden blood mixed into the stool from a bleed higher in the digestive tract, often resulting in a dark tarry stool [see Hematochezia]
• Mesentery – tissue constructed of folds of the peritoneum which supports the small intestine like a flexible scaffolding and carries the blood supply
to the small intestine for absorption and transport of nutrients
• Mesocolon – the mesentery of the large intestine [see Mesentery]
• Metabolism, Metabolic – body processes at the cellular level
• Microvilli – smaller villi covering the villi
• Mitochondria – the power generators of a cell, power used to fuel cell division, absorption, etc. [see Adenosine Triphosphate or ATP]
• Molecule – the smallest particle of a substance that retains the chemical and physical properties of the substance and is composed of two or more atoms. A molecule of water is an example; two atoms of hydrogen and one of oxygen forms a molecule of water.
• Monocyte – a phagocytic white blood cells [see Phagocyte]
• Mucin – a substance composed of glycosylated proteins emitted by the goblet cells which forms mucous in contact with water [see Goblet Cells and Mucous]
• Mucous or Mucus – buffered slippery secretion of mucous membrane, a gel which lubricates and protects the membranes themselves and plays a role in immune function at the local level
• Mucous (or Mucus) Membrane – mucous-secreting tissue lining all body passages that lead to the outer world
• Muscle – specialized tissue with the ability to contract and to conduct electrical impulses
• Neutrophil – a phagocytic white blood cell [see Phagocyte]
• Omnivore, Omnivorous – eats both animal and plant foods
• Organ – a fully differentiated structural and functional unit in an animal that is specialized for some particular function
• Osmosis – diffusion of water across a selectively permeable membrane
• Pepsin – a protyletic (protein digesting) enzyme produced by special cells in the stomach to initiate protein digestion
• Peripheral Nervous System - the nerves belonging to other than the Central Nervous System and the Enteric Nervous System
• Peristalsis – the rhythmic rippling motion of muscles in the digestive tract to move its contents along [see Segmentation]
• Peritoneum – the membrane lining the body cavity
• Peyer's Patches – patches of lymphoid tissue or lymphoid nodules especially prevalent on the wall of the ileum which contain large amounts of lymphocytes and other cells of the immune system
• pH – a measure of how acid or alkaline a solution is
• Phagocyte – white blood cells whose assignment is to move out of the blood into tissue or lymph to destroy bacteria or consume debris
• Phagocytosis – absorption by 'eating' large molecules [see Endocytosis]
• Pinocytosis – absorption by 'sipping' small water soluble molecules
[see Endocytosis]
• Plicae Circulares – folds of the inner lining of the small intestine
• PNS - see Peripheral Nervous System
• Poop – familiar term for waste material discharged from the bowel
• Probiotics – supplement of beneficial live microorganisms such as bacteria and yeasts
• Pus – the hallmark of inflammation, a mix of white blood cells, fluid from damaged cells, and cellular debris (see Infection and Inflammation)
• Pyloric Sphincter – the valve between the stomach and the small intestine (see Sphincter)
• Rectum – the poop storage area of the large bowel
• Resorb or Resorption – to absorb again [see Absorption], essentially a reversal of direction
• Rugae – series of ridges produced by folding of the wall of an organ. Think origami. The stomach wall is folded into rugae, it is not smooth like a bowling ball.
• Saliva – a mix of mucous, water, enzymes and electrolytes which serves to lubricate food's passage down the esophagus as well as cleansing and protecting the mouth
• Segmentation – mixing contractions of the digestive tract; works in concert with peristalsis
• Septicemia – toxic systemic bacterial infection
• Short Chain Fatty Acids (SCFAs) – fermentation by-products of gut bacteria
• Smooth Muscle – type of muscle in the gut wall as opposed to striated muscle; involuntary muscle
• Sphincter/Valve – a ring of muscle that contracts to close an opening and relaxes to open
• Striated Muscle – skeletal muscle (voluntary) and heart muscle (involuntary)
• Stool – see Poop
• Synthesize – to make something new out of different parts, whether a chemical or a rag rug or a casserole from leftovers
• Translocation – change of location; gut bacterial breach of the barrier of the gut wall into the blood stream
• Valve – see Sphincter
• Vein – a blood vessel that carries deoxygenated blood back to the heart for reoxygenation
• Venule – the smallest division of the veins
• Villi (plural) and Villus (singular) – literally "shaggy hair", fingerlike projections on the wall of the small intestine, each covered in turn with microvilli
• Voluntary – under one's own control
• Water – the original, and still the most widely used, solvent; indispensable in poop to prevent constipation
Water - the original, and still the most widely used, solvent; indispensable in poop to prevent constipation.

Glossary

A reference for definitions of terms used in the website which may be unfamiliar.
Topics
Introduction
The First Lesson
Gut 101 – Full Version
• Overview
• Food
• Mouth
• Esophagus
• Stomach
Gut 101 - Condensed
Gut 102 – Full Version
• Small Intestine
• Large Intestine
Gut 102 – Condensed
Water
Gut Bacteria and Fiber
Poop
What Goes Wrong?
Acute Treatment
• Saline Laxatives
• Stimulant Laxatives
• Enemas
• Suppositories
• Lubricant Laxatives
• Stool Softeners
• Osmotic Laxatives
Prevention
• Diet
• Fiber or Prebiotics
• Probiotics
• Vitamins and Minerals
• Osmotic Laxatives
Glossary
Review
Contact and More