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Gastrointestinal Tract
Continuous muscular tube from mouth to anus.
Accessory Digestive Organs
Organs aiding digestion, e.g., liver, pancreas.
Ingestion
Taking food into the gastrointestinal tract.
Secretion
Release of digestive fluids into GI lumen.
Mixing and Propulsion
Churning and moving food through GI tract.
Digestion
Breakdown of food into smaller molecules.
Mechanical Digestion
Physical breakdown of food, e.g., chewing.
Chemical Digestion
Enzymatic breakdown of food molecules.
Absorption
Transfer of nutrients into blood and lymph.
Defaecation
Elimination of waste products from the body.
Peristalsis
Wave-like muscle contractions moving food forward.
Segmentation
Rhythmic contractions mixing food in intestines.
Gastric Juice Composition
Includes acid, enzymes, and buffers for digestion.
Small Intestine
Primary site for nutrient absorption.
Enteric Nervous System
Intrinsic nervous system controlling GI functions.
Myenteric Plexus
Controls GI motility and muscle contractions.
Submucosal Plexus
Regulates secretions in the GI tract.
Autonomic Nervous System
Extrinsic control affecting GI activity.
Parasympathetic Nervous System
Stimulates digestive processes and secretion.
Sympathetic Nervous System
Inhibits digestive activity and secretion.
Neural Reflex Pathways
Responses initiated by stimuli affecting digestion.
Motility
Capability of GI tract to mix and move material.
GIT Length
Approximately 5 to 7 meters long.
Oral Cavity
Space from gums and teeth to fauces.
Salivary Glands
Secrete saliva into oral cavity.
Extrinsic Salivary Glands
Three pairs of glands outside the oral cavity.
Intrinsic Salivary Glands
Small glands scattered throughout oral mucosa.
Mucous Cells
Secrete viscous mucus in saliva.
Serous Cells
Produce watery secretion with enzymes.
Parotid Gland
Contains only serous cells.
Submandibular Gland
Has equal serous and mucous cells.
Sublingual Gland
Primarily composed of mucous cells.
Composition of Saliva
99.5% water, 0.5% electrolytes and enzymes.
Salivary Amylase
Enzyme that breaks down starches.
Electrolytes in Saliva
Activate amylase and buffer acidic foods.
Lysozyme
Antibacterial compound found in saliva.
Control of Salivation
Regulated by autonomic nervous system.
Parasympathetic Stimulation
Increases saliva secretion for lubrication.
Sympathetic Stimulation
Decreases saliva, causing dry mouth.
Lingual Frenulum
Secures tongue to floor of mouth.
Extrinsic Tongue Muscles
Maneuver food and hold tongue position.
Intrinsic Tongue Muscles
Alter tongue shape for speech and swallowing.
Teeth
Accessory organs for chewing food.
Dentin
Calcified tissue providing tooth shape and rigidity.
Bolus
Soft mass of food ready for swallowing.
Monosaccharides
Simple sugars absorbed directly into bloodstream.
Lactose
Disaccharide sugar found in milk.
Fructose
Fruit sugar, a type of monosaccharide.
Lingual Lipase
Enzyme that breaks down triglycerides in mouth.
Pharynx
Common passage for digestive and respiratory systems.
Nasopharynx
Part of pharynx for respiration only.
Oropharynx
Part of pharynx for digestion and respiration.
Laryngopharynx
Part of pharynx for digestion and respiration.
Peristalsis
Muscular contractions propelling food to esophagus.
Oesophagus
Muscular tube transporting food to stomach.
Upper Oesophageal Sphincter (UES)
Regulates food movement from mouth to esophagus.
Lower Oesophageal Sphincter (LES)
Regulates food movement from esophagus to stomach.
Deglutition
Swallowing process involving multiple muscle groups.
Buccal Phase
Voluntary phase of swallowing using tongue.
Pharyngeal Phase
Involuntary phase triggered by tactile receptors.
Esophageal Phase
Involuntary phase moving bolus to stomach.
Stomach
J-shaped organ mixing food and gastric juices.
Chyme
Semi-liquid mixture of food and gastric juice.
Gastric Juice
Digestive fluid containing HCl and enzymes.
Intrinsic Factor
Protein necessary for vitamin B12 absorption.
Gastrin
Hormone stimulating gastric acid secretion.
Mucous Neck Cells
Secrete alkaline mucus protecting stomach lining.
Chief Cells
Produce pepsinogen, inactive form of pepsin.
Parietal Cells
Secrete hydrochloric acid (HCl) in stomach.
B12 absorption
Process of absorbing vitamin B12 in intestines.
Pepsinogen
Inactive enzyme converted to pepsin for protein digestion.
Pepsin
Active enzyme that breaks down proteins into peptides.
Gastric Lipase
Enzyme that digests triglycerides into fatty acids.
Gastrin hormone
Hormone that stimulates gastric acid secretion.
Mechanical digestion
Physical breakdown of food via muscular contractions.
Mixing waves
Peristaltic movements mixing food with gastric juice.
Chyme
Semi-liquid mixture of food and gastric juices.
Pylorus
Region regulating chyme passage to the duodenum.
Peristaltic waves
Rhythmic contractions moving food toward pylorus.
Chemical digestion
Breakdown of food by enzymes and acids.
HCl
Hydrochloric acid aiding digestion and killing microbes.
Parietal cells
Cells secreting H+ and Cl- to form HCl.
Proton pump
Transport mechanism secreting H+ ions into lumen.
ACh
Neurotransmitter stimulating gastric acid secretion.
Gastric juice
Digestive fluid containing enzymes and acids.
Pancreatic juice
Digestive fluid secreted by pancreas into intestines.
Sodium bicarbonate
Buffers gastric juice, creating alkaline pH.
Pancreatic amylase
Enzyme digesting starches into simpler sugars.
Trypsin
Enzyme breaking down proteins into peptides.
Hepatocytes
Liver cells performing metabolic and secretory functions.
Islets of Langerhans
Endocrine cells in pancreas secreting hormones.
Ribonuclease
Enzyme digesting RNA into nucleotides.
Deoxyribonuclease
Enzyme digesting DNA into nucleotides.
Bile canaliculi
Ducts collecting bile between hepatocytes.
Common hepatic duct
Bile duct from liver merging with cystic duct.
Cystic duct
Duct connecting gallbladder to common bile duct.
Common bile duct
Duct transporting bile to the duodenum.
Hepatic sinusoids
Capillaries between hepatocytes for blood exchange.
Hepatic artery
Supplies oxygenated blood to the liver.
Hepatic portal vein
Carries nutrient-rich blood to the liver.
Note 
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