GLOSSARY
- absorption
- taking in of a substance from the surroundings
- accessory gland
- an organ that originates as an outpocketing of the gut, and provides secretions during digestion (e.g. liver, pancreas)
,
- amphiphilic
- having one end soluble in water and the other soluble in lipid
- amylase
- an enzyme that breaks down starch (=amylose) into maltose
- appendix
- a non-functional finger-like extension from the caecum in humans
- autotroph
- an organism that creates its own food using inorganic nutrients and energy captured from an inorganic source
- basal layer
- layer of actively dividing cells that replaces lost or damaged cells of an epithelium
- bile
- a mixture of bile salts and bile pigments secreted by the liver and stored in the gall bladder
- bile pigment
- a greenish waste product resulting from the destruction of haemoglobin by the liver
- bile salt
- one of a family of molecules produced by the liver that is hydrophilic at one end and hydrophobic at the other
- bolus
- chewed and lubricated ball of food that passes down the oesophagus
- caecum
- a dead-end extension branching from the junction of the large and small intestines - used for bacterial
digestion of cellulose in many herbivores
- carnivore
- an organism that gets its energy by preying on other living organisms
- cellulose
- a complex carbohydrate used by plants and fungi to build cell walls; Though made of glucose units, cellulose cannot be broken down by animals.
- chief cells
- cells in the gastric pit which secrete pepsinogen
- cholesterol
- a complex, fat soluble organic compound used by the body to make steroid hormones and to
strengthen cell membranes
- cholecytstokinin (CKK)
- a hormone secreted by
the duodenum that stimulates contractions of the gall bladder to release bile
and secretion of digestive enzymes by the pancreas
- chyme
- contents of the stomach, which are pulverized to an opaque, acidic suspension
- chymotrypsin
- a protein digesting enzyme produced by the pancreas that splits polypeptides at specific points
- colon
- most of the large intestine, where water reabsorption occurs
- crop
- the modified lower part of a bird's oesophagus, used for storing food
- cud
- cakes of bacteria and partially fermented plant material regurgitated by ungulates, chewed and reswallowed as food
- detritus
- dead organic material that accumulates in an environment
- digestion
- the breaking down of macronutrients into useful micronutrients
- disaccharide
- a sugar formed from the bonding of two monosaccharides, or simple sugars
- duodenum
- the first part of the intestine, where most digestive enzymes are added to the chyme
- egest
- to eliminate material from the digestive tract (either undigested food via the mouth, or faeces via the anus)
- egestion
- elimination of bulk waste from food
- emulsify
- to break an insoluble substance into tiny particles that will remain suspended
- endocytosis
- pinching off of the cell membrane to form a vesicle or vacuole inside a cell
-
enterogastrone
- a hormone secreted by the small intestine that slows
peristalsis in the stomach when fats are present
- enzyme
- a specialized protein that accelerates a chemical reaction
- epiglottis
- a cartilage extension at the back of the tongue that covers the windpipe during swallowing
- epithelium
- the layer of cells lining an internal surface of an organ
- excrete
- to release a chemical for elimination from the body
- extracellular
- occuring outside a cell's boundary
- facilitated diffusion
- net movement of molecules through a membrane from an area of high concentration to an area of lower concentration via special protein gates in the membrane
- faeces
- (=feces) egested waste consisting of fibre and undigested food, intestinal bacteria and bile
- fibre
- indigestible cellulose from plant cell walls that is required as a bulking agent in food
- filter feeder
- an organism that gets its energy by filtering tiny organisms or particles of detritus from the surrounding water
- food
- material that is ingested for its nutrient content
- filter feeder
- an organism that gets its food by filtering tiny particles out of the surrounding medium (usually water) - (e.g. clams, sponges)
- gastric
- relating to the stomach
- gastric pit
- tiny pits in the wall of the stomach in which pepsinogen and HCl are secreted
- gastrin
- a hormone secreted by the stomach wall in
response to peptides in the chyme; stimulates secretion and peristalsis of
stomach; inhibited by HCl
- gizzard
- the modified stomach of a bird or reptile that grinds food using ingested gizzard stones
- haemoglobin
- (=hemoglobin) the red pigment in the red blood cells (erythrocytes) that carries oxygen
- hepatic portal
- large vein that carries all blood from the gut to the liver for screening, before it goes to the heart
- heterotroph
- an organism that gets its energy by consuming organic molecules stored in other organisms (e.g. animals, fungi, some bacteria and protists)
- hydrophilic
- soluble in water and other polar solvents
- hydrophobic
- insoluble in water, and usually soluble in non-polar solvents (=lipophilic)
- ileum
- last part of the small intestine where most absorption takes place
- ingest
- to take food into the body
- ingestion
- taking in of food through the mouth
- intracellular
- occuring inside a cell
- isotonic
- having the same solute concentration (i.e. salinity) as the surroundings
- jejunum
- middle part of the small intestine, where most chemical digestion takes place
- lacteal
- dead-end extension of a lymph duct extending into a villus where it picks up lipid droplets
- lipase
- an enzyme that breaks lipids into glycerol and fatty acids
- lipophilic
- soluble in lipids and other non-polar solvents (=hydrophobic)
- lubrication
- making a substance or passageway more slippery to reduce friction
- lumen
- the hollow centre of an organ, e.g. the interior of the intestine
- lymph
- extracelluar fluid derived from blood plasma, and returned to the blood by lymph ducts
- macromolecule
- a large molecule from which smaller useful molecules can be extracted, e.g. protein
- macronutrient
- a type of molecule that is needed in large quantities by the cell / body
- maltose
- a common disaccharide consisting of two glucose
molecules bonded together; the usual first product of starch breakdown
- mesenteric artery
- one of two major branches from the aorta to the intestine - anterior to the small intestine and posterior to the large
- mesentery
- the system of membranes that suspends and supports the intestines
- micromolecule
- a small molecule that can be absorbed and used by a cell or organism
- micronutrient
- an element or small molecule that is needed in only small quantities
- microvillus
- a finger-like projection of the cell membrane on a cell of a villus
- monosaccharide
- a simple sugar, capable of passing through a cell membrane (e.g. glucose,
galactose)
- mucosa
- any epithelium that includes mucus secreting cells
- mucus
- a water soluble protein that lubricates and protects moist surfaces of the body
- nuclease
- an enzyme that breaks DNA and RNA into nucleotides
- nutrient
- a chemical that must be acquired from the environment and is used in metabolism
- parietal cells
- cell in the gastric pit which secretes hydrochloric acid (HCl)
- pepsin
- a powerful enzyme that breaks specific bonds in long polypeptide chains under acid conditions
- pepsinogen
- an inactive form of the enzyme pepsin (one of a family of proteases called zymogens)
- peptidase
- an enzyme that breaks short peptides into amino acids
- peristalsis
- wave-like contractions of circular muscles that move contents of the gastrointestinal tract
- pharynx
- the chamber at the back of the mouth where the nasal passages, oesophagus and trachea open
- pinocytosis
- a form of endocytosis in which liquids are engulfed in vesicles
- polypeptide
- a chain of amino acids; proteins are specialized, functional polypeptides
- protease
- an enzyme that chops up proteins and long polypeptides
- rectum
- last section of the large intestine, where faeces are formed
- ruga
- (pl. rugae) one of the ridges in the inner wall of the stomach that acts as a baffle to create turbulence in the chyme
- saliva
- a mixture of water, dissolved mucus proteins, and amylase secreted into the mouth from five glands in the jaw, cheeks and throat
- secrete
- to release a chemical for some use within the body
- secretin
- a hormone released by the duodenum in
response to acid stimulation; induces release of NaHCO3 by pancreas
- sphincter
- strong circular muscle that restricts the opening of a passageway
- steroid
- a hormone produced from cholesterol (e.g. corticosteroid, testosterone, estrogen)
- substrate
- the molecule(s) on which an enzyme acts (=reactant)
- trypsin
- a protein digesting enzyme produced by the pancreas that splits polypeptides at specific points
- villus
- a finger-like projection of an epithelial tissue that serves to increase surface area
- vitamin
- an organic molecule required as a helper in a metabolic reaction that the body is unable to manufacture
- zymogen
- a protein digesting enzyme in an inactive form, and therefore not damaging to its producing cell