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Module 15 in the Syllabus

The Digestive System and Nutrition Images
Image gallery for study with links to larger teaching JPEGs for classroom presentation

Question Drill for The Digestive System and Nutrition
Conceptual Vocabulary Self-Test

Basic Terms Crossword Puzzle

Basic Puzzle Solution

Conceptual Vocabulary
Gastrointestinal tractThe gastrointestinal tract is the system of organs within multicellular animals that takes in food, digests it to extract energy and nutrients, and expels the remaining waste.
DigestionDigestion is the process of metabolism whereby a biological entity processes a substance in order to chemically and mechanically convert the substance for the body to use.
NutritionNutrition is a science that examines the relationship between diet and health.
NutrientA nutrient is a substance used in an organism's metabolism or physiology which must be taken in from the environment.
MouthThe mouth, also known as the buccal cavity or the oral cavity, is the orifice through which an organism takes in food and water.
EsophagusThe esophagus or gullet is an organ in vertebrates which consists of a muscular tube through which food passes from the pharynx to the stomach.
PeristalsisPeristalsis is the rhythmic contraction of smooth muscles to propel contents through the digestive tract.
SalivaSaliva is the watery and usually frothy substance produced in the mouths of humans and some animals.
SwallowingSwallowing, known scientifically as deglutition, is the reflex in the human body that makes something pass from the mouth, to the pharynx, into the esophagus, with the shutting of the epiglottis.
Small intestineThe small intestine is where the majority of digestion takes place, the part of the gastrointestinal tract (gut) between the stomach and the large intestine which includes the duodenum, jejunum, and ileum.
LiverIn addition to being the largest gland in the human body, producing bile for example, the liver plays a major role in metabolism.
VitaminA vitamin is a nutrient that is an organic compound required in tiny amounts for essential metabolic reactions in a living organism.
PharynxThe pharynx is the part of the neck and throat situated immediately posterior to the mouth and nasal cavity, and cranial, or superior, to the esophagus, larynx, and trachea.
MasticationMastication or chewing is the process by which food is mashed and crushed by teeth.
Gastric acidGastric acid is one of the main secretions of the stomach, an acid solution consisting mainly of hydrochloric acid, and small quantities of potassium chloride and sodium chloride.
Parietal cellParietal cells are the stomach epithelium cells which secrete gastric acid and intrinsic factor.
DuodenumThe duodenum is a hollow jointed tube about 25-30 cm long connecting the stomach to the jejunum.
Large intestineThe large intestine, commonly referred to by its Greek name, the colon, is the last part of the digestive system: the final stage of the alimentary canal in vertebrate animals.
Exocrine glandExocrine glands are glands that secrete their products into ducts.
BileBile is a bitter, yellow or green alkaline fluid secreted by hepatocytes from the liver with components including cholesterol, lecithin, bilirubin, biliverdin, sodium glycocholate and sodium taurocholate.
Vitamin AVitamin A is an essential human nutrient. In foods of animal origin, the major form of this vitamin is retinol, but all forms have a beta-ionone ring to which an isoprenoid chain is attached.
BolusA bolus is a round mass of organic matter moving through the digestive tract.
ChymeChyme is the liquid substance found in the stomach before passing through the pyloric valve and entering the duodenum.
Gastric juiceGastric juice is a strong acidic liquid, pH 1 to 3 in humans, released by gastric glands in the lining of the stomach. Its main components are digestive enzymes pepsin and rennin, hydrochloric acid, and mucus.
MicrovilliThe microvilli are structures that increase the surface area of cells by approximately 600 fold, thus facilitating absorption and secretion.
JejunumThe jejunum is the central of the three divisions of the small intestine and lies between the duodenum and the ileum.
IleumThe ileum is the final section of the small intestine.
Intestinal villiIntestinal villi are tiny, finger-like structures that protrude from the wall of the intestine.
ColonThe colon is another name for the large intestine.
Pancreatic juicePancreatic juice is produced by the pancreas, containing a variety of enzymes including trypsinogen, chymotrypsinogen, elastase, carboxypeptidase, pancreatic lipase, and amylase.
Pancreatic ductThe pancreatic duct is a duct joining the pancreas to the common bile duct.
GallbladderThe gallbladder, or cholecyst, is a pear-shaped organ that stores about 50 ml of bile until the body needs it for digestion.
Dietary mineralDietary minerals are the chemical elements required by living organisms, other than the four elements carbon, hydrogen, nitrogen, and oxygen which are present in common organic molecules.
SubmucosaIn the gastrointestinal tract, the submucosa is the layer of loose connective tissue that supports the mucosa, as well as joins the mucosa to the bulk of underlying smooth muscle.
CholecystokininCholecystokinin is a peptide hormone of the gastrointestinal system responsible for stimulating the digestion of fat and protein.
Gastric chief cellA gastric chief cell is a cell in the stomach that releases pepsinogen and rennin.
Bile acidReleased from the gall bladder, bile acids serve multiple functions including elimination of cholesterol from the body, elimination of catabolites from the liver, and emulsifying lipids and fat soluble vitamins in the intestine.
AmylaseAmylase is the name given to glycoside hydrolase enzymes that break down starch into glucose molecules.
PepsinPepsin is a digestive protease released by the chief cells in the stomach that functions to degrade food proteins into peptides.
SucraseSucrase is the name given to a number of enzymes that catalyse the hydrolysis of sucrose to fructose and glucose.
MaltaseMaltase is an enzyme produced by the cells lining the small intestine which specifically breaks down the disaccharide maltose.
LactaseLactase, a member of the beta-galactosidase family of enzymes, is a glycoside hydrolase involved in the hydrolysis of the disaccharide lactose into constituent galactose and glucose monomers
B vitaminsThe B vitamins are eight water-soluble vitamins that play important roles in cell metabolism.
ThiamineOne of the B vitamins, thiamine plays an important role in helping the body metabolize carbohydrates and fat to produce energy. It is essential for proper functioning of the heart, nervous and digestive systems.
RiboflavinAlso known as vitamin B2, riboflavin is the central component of the cofactors FAD and FMN. It is therefore required by all flavoproteins.
NiacinAlso known as nicotinic acid or vitamin B3, niacin is a water-soluble vitamin whose derivatives such as NADH, NAD, NADP play essential roles in energy metabolism and DNA repair.
Pantothenic acidAlso called vitamin B5, pantotheric acid is a water-soluble vitamin needed to form coenzyme-A.
BiotinBiotin is a water-soluble B-complex vitamin which is composed of an ureido ring fused with a tetrahydrothiophene ring. It is important for fatty acid synthesis, in gluconeogenesis, and to metabolize leucine.
Folic acidThe B complex vitamin, folic acid, is necessary for the production and maintenance of new cells.
Vitamin DVitamin D represents a group of fat-soluble prohormones, the two major forms of which are ergocalciferol and cholecalciferol.
Ascorbic acidVitamin C or ascorbic acid is a highly effective antioxidant. It acts to lessen oxidative stress, as a substrate for ascorbate peroxidase, as well as an enzyme cofactor in biosynthesis.
G cellThe G cell is a type of cell in the stomach that secretes gastrin. It works in conjunction with gastric chief cells and parietal cells.
S cellS cells are cells which release secretin, found in the jejunum and duodenum.
LactealA lacteal is a lymphatic capillary that absorbs dietary fats in the villi of the small intestine.
TrypsinTrypsin is a serine protease found in the digestive system, where it breaks down proteins. It is also often used in the laboratory for numerous procedures.
Serine proteaseSerine proteases or serine endopeptidases are a class of peptidases that are characterised by the presence of a serine residue in the active site of the enzyme.
Gastric pitsGastric pits are indentations in the stomach which denote entrances to the glands.
Vermiform appendixThe vermiform appendix is a blind ended tube connected to the cecum, from which it develops embryologically.
SecretinSecretin is a peptide hormone produced in the S cells of the duodenum for regulation of the pH of the duodenal contents via the control of gastric acid secretion and buffering with bicarbonate.
LipaseA lipase is a water-soluble enzyme that catalyzes the hydrolysis of ester bonds in water-insoluble, lipid substrates.
ChymotrypsinChymotrypsin is a digestive enzyme that can perform proteolysis which cleaves peptides favorably at the carboxyl side of tyrosine, tryptophan, and phenylalanine because those three amino acids contain phenyl rings.
Hepatic portal veinThe hepatic portal vein is a portal vein in the human body that drains blood from the digestive system and its associated glands.
CarboxypeptidaseCarboxypeptidase is an enzyme that hydrolyzes the carboxy-terminal (C-terminal) peptide bond of proteins and peptides thus releasing the last amino acid of the chain.
Vitamin KVitamin K denotes a group of lipophilic, and hydrophobic, vitamins that are needed for the posttranslational modification of certain proteins, mostly required for blood coagulation.
BeriberiBeriberi is a nervous system ailment caused by thiamine deficiency.
Vitamin B6Also known as vitamin B6, pyridoxal phosphate is the active form and is a cofactor in many reactions of amino acid metabolism, including transamination, deamination, and decarboxylation.
ScurvyScurvy is a deficiency disease that results from insufficient intake of vitamin C, which is required for correct collagen synthesis in humans.
Advanced terms that may appear in context in MCAT passages
RicketsRickets is a softening of the bones in children potentially leading to fractures and deformity. The predominant cause is a vitamin D deficiency.
PellagraPellagra is a vitamin deficiency disease caused by dietary lack of niacin and protein.
ForegutThe foregut is the anterior part of the alimentary canal, from the mouth to the duodenum at the entrance of the bile duct.
Alkaline tideAlkaline tide refers to a condition, normally encountered after eating a meal, when stomach acid is released into the stomach that causes a temporary increase in pH of the blood.
Ileocecal valveThe ileocecal valve is a sphincter muscle situated at the junction of the small intestine and the large intestine to regulate the flow of chyme into the bowels.
HepatocyteMaking up 70-80% of the cytoplasmic mass of the liver, hepatocytes are involved in protein synthesis, protein storage and transformation of carbohydrates, synthesis of cholesterol, bile salts and phospholipids, and detoxification.
GhrelinGhrelin is a hormone produced by cells lining the fundus of the human stomach that stimulate appetite.
LeptinLeptin is a protein hormone produced by adipose tissue that plays a key role in regulating energy intake and energy expenditure, including the regulation of appetite and metabolism.
FlavoproteinFlavoproteins are proteins that contain a nucleic acid derivative of riboflavin: the flavin adenine dinucleotide or flavin mononucleotide.
CyanocobalaminCyanocobalamin is a compound that is metabolized to a vitamin in the B complex commonly known as vitamin B12.
CholineClassified as an essential nutrient, choline is usually grouped with the B vitamins. This natural amine is found in the lipids that make up cell membranes as well as within many other physiologically important substances.
Gastrin releasing peptideGastrin releasing peptide is released by the post-ganglionic fibres of the vagus nerve which innervate the G cells of the stomach and stimulate them to release gastrin.
Enterochromaffin-like cellEnterochromaffin-like cells are a type of neuroendocrine cells found in the gastric glands of the gastric mucosa, particularly in the vicinity of parietal cells. ECL cells synthesize and secrete histamine.
PylorusThe pylorus is the region of the stomach that connects to the duodenum.
ChyleChyle is a milky fluid consisting of lymph and emulsified fats, or free fatty acids. It is formed in the small intestine during digestion of ingested fatty foods and taken up by lymph vessels specifically known as lacteals.
Brush borderA brush border is the name for the microvilli-covered surface of pseudostratified columnar epithelium and simple columnar epithelium found in small intestine and in the distal tubule of the kidney.
Brunner's glandsBrunner's glands, or duodenal glands, are compound tubular submucosal glands located throughout the duodenum which produce an alkaline secretion containing bicarbonate.
TrypsinogenTrypsinogen is the precursor form of the pancreatic enzyme trypsin.
ChymotrypsinogenChymotrypsinogen is a precursor of the digestive enzyme chymotrypsin.
EnteropeptidaseEnteropeptidase or enterokinase is an enzyme which transforms trypsinogen into trypsin, indirectly activating a number of pancreatic digestive enzymes.
CecumThe cecum is a pouch connected to the ascending colon of the large intestine and the ileum.
Ampulla of VaterThe ampulla of Vater is formed by the union of the pancreatic duct and the common bile duct.
Alpha-AmylaseAlpha-amylase is the major form of amylase found in humans and other mammals.
ErepsinErepsin is an enzyme that digests peptides which works only on the outside peptide bonds.
TocopherolTocopherol, also known as vitamin E, actually describes a series of organic compounds consisting of a methylated phenols.
Esophageal glandsThe esophageal glands are small compound racemose exocrine glands of the mucous type.
CanaliculusA canaliculus is an adaptation found on gastric parietal cells, which is a deep infolding, or little channel, serving to increase the surface area for secretion.
FundusThe fundus is the rounded part of the upper stomach which allows for an accumulation of gases produced by chemical digestion.
RugaeRugae is a term used in anatomy that refers to a series of ridges produced by folding of the wall of an organ, most commonly applied to the internal surface of the stomach.
AcinusAn acinus refers to the berry-shaped termination where the secretion of an exocrine gland is produced, such with the exocrine pancreas.
Bile canaliculiBili canaliculi are thin tubes that collect bile secreted by hepatocytes, which merge and form bile ductules, eventually becoming the common hepatic duct.
ErgocalciferolErgocalciferol is a form of Vitamin D. It is created from viosterol, which in turn is created when ultraviolet light activates ergosterol.
CholecalciferolCholecalciferol is a form of Vitamin D. Its precursor is 7-Dehydrocholesterol which only forms the vitamin after being exposed to UV radiation.
Dehydroascorbic acidDehydroascorbic acid is an oxidized form of ascorbic acid. It is actively imported into the endoplasmic reticulum of cells and generates the oxidative potential found there.

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