Digestive System
Includes the organs that ingest good, mix and move the ingested materials, add secretions to facilitate digestion of the materials into smaller usable components, absorb the necessary nutrients into the blood or lymph, and expel the waste products from th
Ingestion
The introduction of solid and liquid nutrients into the oral cavity; First step in digestion
Motility
General term for voluntarily and involuntary muscular contraction for mixing and moving materials through the GI tract
Secretion
The process of producing and releasing substances into the GI tract
Digestion
The breakdown of ingested food into smaller structures that may be absorbed from the GI tract
Mechanical Digestion
Occurs when ingested material is physically broken down into smaller units without changing the chemical structure
Chemical Digestion
The activity of specific enzymes to break chemical bonds to change larger complex molecules into smaller molecules that can be absorbed
Absorption
Membrane transport of digested molecules, electrolytes, vitamins, and water from the GI tract into the blood or lymph
Elimination
The expulsion of indigestible components now absorbed
Gastrointestinal Tract
The tubular passage of mucous membrane and muscle extending about 8.3 meters from mouth to anus
Accessory Digestive Organs
Organs that assist in the breakdown of food
Mucosa
The inner-lining mucous membrane, typically consisting of an epithelium, lamina propria, and muscularis mucosae
Epithelium
Cellular layer that is in contact with the contents within the lumen; Simple columnar epithelium is most common type in the GI tract
Lamina propria
A layer of loose areolar connective tissue that helps anchor the epithelial layer
Muscularis mucosae
Thin layer of smooth muscle that causes slight movements in the mucosa which can facilitate secretions into the lumen or increase contact of materials in the lumen
Submucosa
Layer of areolar and dense irregular connective tissue that contains blood vessels, lymph vessels, nerves, and glands
Submucosal Nerve Plexus
Fine branches of nerves extending into the muscosa, along with their associated autonomic ganglia
Peyer's Patches
Collections of lymphatic tissue found in the submucosa of the small intestine
Muscularis
Layer of smooth muscle that usually contains two layers
Inner Circular Layer
Inner layer of smooth muscle oriented circumferentially
Outer Longitudinal Layer
Outer layer of smooth muscle that are oriented lengthwise
Myenteric Nerve Plexus
A layer of fine branches of nerves and associated autonomic ganglia located between the muscularis layer
Enteric Nervous System
Composed of the submucosal nerve plexus and myenteric nerve plexus
Sphincter
The thickening of the inner circular muscle layers that is able to close off the lumen at some point in order to control the movements of materials in the GI tract
Peristalsis
The alternating contraction sequence of the muscularis layers to propel ingested food through the GI tract
Mixing
The kneading motion that occurs at any moment within different regions of the GI tract to blend ingested materials with secretions; Lacks forward movement
Adventitia
The outmost tunic composed of areolar connective tissue and collagen and elastic fibers; Located outside the peritoneal cavity
Serosa
The outermost tunic composed of areolar connective tissue and collagen and elastic fibers that are all covered in serous membrane; Located in the peritoneal cavity
Parietal Peritoneum
The serous membrane that lines the inner surface of the abdominal wall
Visceral Peritoneum
The serous membrane that covers the surface of internal organs
Peritoneal cavity
The potential space between the peritoneal layers were fluid is secreted to lubricate the organs
Intraperitoneal
Organs that lie within the peritoneal cavity
Retroperitoneal Organs
Organs that lie outside the parietal peritoneum directly against the posterior abdominal wall
Mesentery
The double layer of peritoneum that supports, suspends, and stabilizes the intraperitoneal GI tract organs
Greater Omentum
Mesentery that extends inferiorly from the greater curvature of the stomach and covers most of the abdominal organs; Serves to insulate the organs and as storage for excess fat; "fatty apron
Lesser Omentum
Mesentery that connects the lesser curvature of the stomach and the proximal end of the duodenum and liver
Falciform Ligament
Flat, thin, crescent-shaped peritoneal fold that attaches the liver to the internal surface of the anterior abdominal wall
Mesentery Proper
Fan-shaped fold of peritoneum that suspends the jejunum and ileum from the internal surface of the posterior abdominal wall
Mesocolon
Fold of peritoneum that attaches parts of the large intestine to the posterior abdominal walls; Sectioned and named based on what part of colon it suspends
Barorecptors
Receptors that detect either stretch or pressure of a particular region of the GI tract as contents move through
Chemoreceptors
Receptors that detect the presence of specific substances of the passing contents within the lumen
Long Reflexes
The coordinated secretory and smooth muscle responses due to sensory input from receptors to the CNS
Short Reflexes
Digestive reflexes that do not involve the CNS; Only occur within neurons of the enteric nervous system in the GI tract wall
Labial Frenulum
Median fold of mucosa that joins the internal aspect of each lip to the gums
Transverse Palatine Folds
Friction ridges on the hard palate that assist the tongue in manipulating ingested materials prior to swallowing
Uvulua
Closes the posterior entrance to the nasopharynx with the soft palate during swallowing
Fauces
Represent the opening between the oral cavity and oropharynx
Lingual Frenulum
Fold of mucous membrane that connects the tongue to the floor of the mouth
Intrinsic Salivary Glands
Unicellular glands that continuously release small amounts of secretions independent of the presence of food
Lingual Lipase
An enzyme only from intrinsic secretions that begins the digestion of triglycerides
Extrinsic Salivary Glands
Multicellular exocrine glands outside the oral cavity that secrete in the presence of food
Parotid Salivary Glands
The largest salivary glands that produce approx. 20-30% of saliva
Submandibular Salivary Glands
Salivary glands that produce approx. 60-70% of saliva
Sublingual Salivary Glands
Smallest salivary glands that only produce approx. 3-5% of saliva
Bolus
Moistened, ingested food in the mouth and esophagus
Mastication
Mechanical digestion in the oral cavity
Mastication Center
Nuclei within the medulla oblongata and pons that control chewing
Detin
Hardest material in the body that forms the primary mass of a tooth
Enamel
Tough, durable layer that covers the surface and crown of a tooth
Pulp Cavity
Center of a tooth
Pulp
The tissue that contains the blood vessels and nerves of a tooth
Deciduous Teeth
Baby teeth
Gingivae
The firm but soft dense irregular connective tissue with overlying nonkertinized stratified squamous that surrounds the teeth
Pharungeal Constrictors
The skeletal wall that forms the wall of the pharynx
Reflux Esophagitis
Pain and irritation due chyme reflux
Hiatal hernias
When a portion of the stomach protrudes through the diaphragm into the thoracic cavity
Gastroesophageal Reflux Disease (GERD)
Chronic reflux esophagitis
Barret Esophagus
The changing of esophageal epithelium from stratified squamous to columnar secretory epithelium as a protection from erosive gastric secretions; Increases risk of cancer
Esophageal Hiatus
The opening of the diaphragm for the esophagus
Superior Esophageal Sphincter
The contracted rink of circular skeletal muscle where the esophagus meets the pharynx
Inferior Esophageal Sphincter
The contracted ring of smooth muscle at the inferior end of the esophagus; Structure itself isn't strong enough to prevent reflux
Voluntary Phase
Phase of swallowing after ingestion, controlled by the cerebral cortex
Pharyngeal Phase
Involuntary phase of swallowing when bolus arrives at the oropharynx
Swallowing Center
Located in the medulla oblongata that receives information from receptors stimulated by bolus
Esophageal Phase
Involuntary phase of swallowing during which the bolus passes through the esophagus
Gastric Bypass
Reducing the size of the stomach and diverting food to the jejunum
Cardiac orifice
Where the esophagus meets the stomach
Pyloric orifice
The opening of the stomach to the duodenum
Pyloric Sphinceter
A ring of circular skeletal muscle that regulates the entry of material to the small intestine
Rugae
Folds of the stomach that allow for expansion of the organ
Gastric Pits
Indentations in the lining of the stomach
Gastric Glands
Located in the stomach; secrete HCl and various enzymes (e.g., pepsin) when stimulated by gastrin.
Gastric Juice
A combination of Hydrochloric Acid and Pepsinogen that helps digest food in the stomach; Secreted from 4 types of gastric cells
Surface Mucous Cells
Line the stomach lumen and extend into the gastric pits; Secrete alkaline product containing mucin into gastric juice; Helps to prevent ulcers
Mucous Neck Cells
Cells located immediately deep to the base of gastric pits that produce acidic mucin that helps maintain the acidic conditions of the stomach
Parietal Cells
Cell responsible for secreting Intrinsic factor and HCl into the stomach
Intrinsic Factor
The glycoprotein that allows for the absorption Vitamin B12 in the ileum
Hydrochloric Acid (HCl)
Responsible for the maintenance of low pH within the stomach; Vomiting increases formation
Chief Cells
Most numerous secretory cells in gastric glands; Produce and secrete packets of zygomogen, granules mostly containing pepsinogen (becomes pepsin), and gastric lipase
Gastric lipase
Enzyme secreted from chief cells that has a limited role in fat digestion (~10-15%)
G-Cells
Cells that produce the hormone gastrin
Gastric Mixing
A form of mechanical digestion that changes the semidigested bolus to chyme
Chyme
Partially digested, semiliquid food mixed with digestive enzymes and acids in the stomach
Gastric Emptying
The movement of acidic chyme through the pyloric sphincter
Retopulsion
The reverse flow of chyme in response to the closing of the pyloric sphincter; Contribues to further mixing
Peptic Ulcer
A chronic, solitary erosion of a part of the stomach or duodenum lining
Gastric Ulcers
Peptic ulcers that occur in the stomach
Duodenal Ulcers
Peptic ulcers that occur in the duodenum
Perforation
The erosion of the entirety of an organ wall
Gastritis
Irritation of the gastric mucosa
Pacemaker Cells
Cells in the stomach walls that spontaneously depolarize less than four times a minute and establish the basic rhythm of muscular contraction of the stomach
Gastric Phase
The process following the bolus reaching the stomach, regulated by the nervous system via gastric reflex and the endocrine system through the release of gastrin
Intestinal Phase
The process following the chyme reaching the SI, regulated by the nervous and endocrine systems; Involves the intestinal reflex and the release of cholecystokinin and secretin
Cholecystokinin (CCK)
Stimulates the gall bladder to contract and send bile into the duodenum
Secretin
Stimulates pancreas to release pancreatic juice high in bicarbonate ions
Glucose-Dependent Insulinotropic Peptide (GIP)
Hormone believed to release insulin to the SI in response to increased glucose concentration of chyme
Inflammatory Bowel Disease (IBD)
Umbrella term for the autoimmune diseases Crohn disease and ulcerative colitis
Crohn Disease
A condition characterized by intermittent and relapsing episodes of intense abdominal cramping and diarrhea
Ulcerative colitis
Chronic inflammation of the colon with presence of ulcers
Irritable Bowel Syndrome (IBS)
Characterized by abnormal function of the colon with symptoms of crampy abdominal pain, bloating, constipation, and diarrhea
Circular Folds
The mucosal and submucosal tunics of the small intestine that extend inward toward the lumen
Villi
Fingerlike extensions of the intestinal mucosa that increase the surface area for absorption
Microvilli
Extensions of the plasma membrane of the simple columnar epithelial cells of the SI in order to increase the surface area for absorption
Intestinal Glands
Invaginations of mucosa between the villi that house goblet cells, unicellular gland cells, and enteroendocrine cells, secrete intestinal juice
Intestinal Juice
Slightly alkaline fluid secreted by mucosal cells that contains various digestive enzymes
Goblet Cells
Produce mucin to lubricates and protects the intestinal lining; Increase in number from the duodenum to the ileum
Unicellular Gland Cells
Cells in the intestinal glands that synthesize enteropeptidase
Enteropeptidase
Enzyme that catalyzes the activation of trypsin from trypsinogen
Enteroendocrine Cells
Release CCK and secretin in the SI
Brunner Gland
Produces a viscous, alkaline mucus secretion to protect duodenum from acidic chyme
Segmentation
Mixes chyme with accessory gland secretions through a "backward-and-forward" motion
Gastroileal Reflex
Distention of the stomach intensifies peristalsis at the ileum forcing chyme into the cecum
Biliary Apparatus
Network of thin ducts that transport bile from liver and gall bladder to duodenum
Hepatic Duct
The duct that leads from the liver to the common bile duct; transports bile.
Common Hepatic Duct
Large bile duct formed from L/R hepatic ducts that leads from gallbladder and joins with the cystic duct
Common Bile Duct
The duct that carries bile from the gallbladder and liver to duodenum
Hepatopancreatic ampulla
Cavity formed by the union of the common bile duct and the pancreatic duct
Hepatopancreatic Sphincter
Regulated movement of bile and pancreatic juice into the duodenum
Major Duodenal Papilla
Projection where the hepatopancreatic ampulla penetrates the wall of the duodenum
Accessory Pancreatic Duct
Alternate way for small amount of pancreatic juice may enter the duodenum through minor duodenal papilla
Minor Duodenal Papilla
Collects from accessory pancreatic duct
Porta Hepatis
The sight where blood and lymph vessels, bile ducts, and nerves extend from the liver; Hilum of the liver
Hepatic Lobules
Functional unit of the liver
Hepatocytes
Liver cells that continuously produce bile
Portal Triads
Bile ductule found at the periphery of each lobule
Hepatic sinusoids
Highly permeable blood capillaries between hepatocytes
Kupffer Cells
Macrophages in the liver
Liver cirrhosis
Scarring of the liver due to destruction of hepatocytes
Hepatic Portal Hypertension
High blood pressure in the hepatic portal venous system
Jaundice
Yellow of the skin and sclerae due to the liver's inability to eliminate bilirubin
Edema
Accumulation of fluid in body tissues due to reduced formation and release of albumin
Ascites
Fluid accumulation in the abdomen due to decreased albumin production
Bile Canaliculus
Small channel that transport bile from hepatocytes to bile ductule in the portal triad
Gallstones
Small crystals that form formed from cholestrol or calcium and bile salts in the gallbladder.
Cholelihiasis
The presence of gallstones either within the gallbladder or the biliary apparatus
Cholecystitis
Inflammation of the gallbladder
Cholecystectomy
Surgical removal of the gallbladder
Cystic Duct
Connects the gallbladder to the bile duct
Acinar Cells
Modified simple cuboidal epithelial cells
Acini lobules
Organized structures of acinar cells
Pancreatic Juice
Alkaline secretions of acinar cells and cells that line pancreatic ducts, composed of mostly water, HCO3-, and a mixture of digestive enzymes
Appendicitis
Inflammation of the appendix
Rectal Valves
Three thick transverse folds that ensure fecal material is retained during the passing of gas
Internal Anal Sphincter
Involuntary smooth muscle at the base of the anal canal
External Anal Spincter
Voluntary skeletal muscle at the base of the anal canal
Teniae coli
Thin, distinct, longitudinal bundles of smooth muscle that help the LI to contract and expand
Omental Appendices
Small accumulations of fat covered by visceral peritoneum
Polyps
Outgrowths from the colon mucosa; Usually a sign of colorectal cancer
Sigmoidoscopy
Procedure where an endoscope is inserted into the rectum and sigmoid colon
Colonoscopy
Procedure where an endoscope is inserted into the LI
Haustral Churning
Muscular churning of the LI to promote the absorption of water
Mass Movement
Powerful, peristaltic-like contractions involving the teniae coli to propel fecal mater toward the rectum
Diverticulosis
The presence of small "bulges" in the intestinal lining
Diverticulitis
Inflammation of the diverticula and may cause fatal rupturing
Gastrocolic Reflex
Increased peristalsis of the colon after food has entered the stomach
Defecation Reflex
Stimulated by stretch receptors in rectum when distended with feces
Salivary amylase
A salivary gland enzyme that hydrolyzes starch
Pancreatic amylase
Pancreatic enzyme that continues the digestion of starch into shorter strands of glucose as a component of pancreatic juice
Dextrnase glucoamylase
A brush border enzyme that breaks bonds between glucose subunits of oligosaccharides
Maltase
A brush border enzyme that breaks the bonds between two glucose molecules that compose maltose
Lactase
Brush Border enzyme that digests lactose to glucose and galactose
Sucrase
Brush Border enzyme that digests sucrose to glucose and fructose
Lactose Intolerant
Reduced amount of lack of lactase
Celiac Disease
An autoimmune disorder characterized by sensitivity to gluten
Trypsin
Pancreatic enzyme that digests proteins in the small intestine
Chymotrypsin
One of the main pancreatic proteases that degrades proteins into small polypeptides; activated (from chymotrypsinogen) by trypsin.
Carboxypeptidase
Enzyme that breaks down protein; Activated by trypsin to convert from procarboxypeptidase
Dipeptidase
Brush border enzyme that breaks the final bond between two amino acids for absorption
Aminopeptidase
Brush border enzyme that generates free amino acids from the amino ends of peptides
Emulsification
Breakdown of large fat globules into smaller, digestible particles
Bile Salts
Compounds in bile that aid in emulsification in the duodenum
Micelle
A spherical structure composed of aggregated amphipathic molecules that forms in aqueous solution
Chylomicron
A lipid transport globule composed of fats mixed with cholesterol and coated with proteins
Phosphatase
Enzyme that breaks the bonds holding phosphate to the rest of the nucleotide
Nucleosidase
Enzyme that breaks bond between sugar and nitrogenous base of nucleoside