• 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.


A  reference for definitions of terms used in the website which may be unfamiliar.



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


Gut Bacteria and Fiber


What Goes Wrong?

Acute Treatment

   • Saline Laxatives

   • Stimulant Laxatives

   • Enemas

   • Suppositories

   • Lubricant Laxatives

   • Stool Softeners

   • Osmotic Laxatives


   • Diet

   • Fiber or Prebiotics

   • Probiotics

   • Vitamins and Minerals

   • Osmotic Laxatives



Contact and More